نشریه پژوهش های علوم دامی
سال سی و سوم شماره 4 (زمستان 1402)

The use of food additives such as antibiotics is a useful tool in reducing energy loss (methane) and nitrogen (ammonia). However, the use of antibiotics in animal feed has been banned in the EU since January 2006 due to their residual risk in milk and meat and its subsequent effects on human health (Aminipour et al. 2017). Essential oils of herbals are used because of their antimicrobial effect against bacteria, protozoa and fungi, their ability to manipulate rumen fermentation, and their potential to reduce methane production in ruminant diets (Gunal et al. 2017). The results of research show that peppermint essential oil reduces methane, ammonia nitrogen concentration, number of protozoa and changes the molar ratio of short-chain fatty acids (Ahmad et al. 2014). Some experiments show that thyme essential oil reduces the production of gas (Roy et al. 2015), methane (Baraz et al. 2018). Although there is useful information about the effects of peppermint, thyme and rosemary essential oils on their positive effect on rumen fermentation, a study examining the effect of a mixture of these essential oils is not available. Therefore, this study was conducted to evaluate the effect of different doses of three mixes of peppermint, thyme and rosemary essential oils (6, 12 and 18 µl) on in vitro gas production parameters.

The essential oils were mixed in three levels of 150, 300, 450 µl, with three different ratio including A=(1: 3: 2), B=(2: 1: 3) and C=(3: 2: 1); thereafter, the effect of different doses (6, 12, 18 μl) of these three combinations on fermentation parameters was studied. Rumen fluid was obtained from three sheep before morning feeding via rumen fistula. The effect of the mixture of essential oils on gas production and kinetics of gas production was investigated by incubating 125 mg of each sample at 2, 4, 6, 8, 12, 24, 36, 48, 72 and 96 hours. Also, in another experiment, by incubating the samples for 24 hours, gas production and methane production were estimated. Also, different mixtures were compared in terms of their effect on reducing the amount of methane production.

Adding a mixture of essential oils in different doses reduced gas production compared to the control group (P<0.05). Comparison of the three mixtures of essential oils tested showed that during the incubation period of 2 to 12 hours, mixtures B and C showed a decreasing trend in gas production, meanwhile mixture C had the lowest value compared to the other two mixtures (P<0.05). There was no significant difference between mixtures A and B during 24 to 48 hours of incubation, but mixture C showed the lowest value compared to the other two mixtures (P<0.05). At 72 to 96 hours of incubation, mixtures A, B and C did not show significant differences in gas production (P<0.05). The results of this experiment showed that mixture C caused a further reduction in gas production than other mixtures. Decreased gas production can be related to a decrease in the fermentation activities of microorganisms and a decrease in dry matter digestibility (Tan et al. 2011). On the other hand, reduction in gas production by essential oils may indicate more efficient use of energy due to inhibition of energy loss in the form of methane (Aminipour et al. 2017). In the present experiment, different doses of essential oil mixtures reduced gas production, so that at 2 to 96 hours of incubation, doses of 6 and 12 did not differ significantly in terms of gas production (P <0.05); but the level of 18 µl compared to other doses showed a significant decrease in gas production (P <0.05). The mixture of essential oils at the level of 6 μl showed that mixture A, which contained the highest amount of thyme and rosemary essential oils, had no effect on gas production during incubation compared to control, while mixture C, which contained higher amounts of peppermint and Thyme essential oils had the greatest impact on gas production. The gas production potential (B) was not significantly different between the three mixtures (P>0.05), although numerically it was the lowest in mixture C (19.53 versus 11.82). Gas production rate (c) had a similar trend so that despite the lack of significant differences between the three mixtures (P>0.05), numerically C mixture showed the lowest value in terms of this parameter. A decreasing trend in methane production at the level of 18 μl of essential oil of a mixture of three herbals was observed, so that in mixture B was the lowest value compared to the control group (P <0.05). Essential oils may directly inhibit the growth and activity of methanogenic microbes, or indirectly by reducing the number of methanogen-related protozoa (Gonal et al. 2017) or by indirect reduction in some processes of methanogenic microbial metabolism (Cobellis et al. 2015) affect methane production.Due to the fact that the proportion of two thirds of mixture B is peppermint essential oil, the percentage of methane production in mixture B compared to the control showed a significant decrease. It has been reported that the decrease in methane production may be due to the reduction of total protozoan by menthol as the main active ingredient of peppermint essential oil (Roy et al. 2015).

The results of this study showed that in the gas production test at 2 to 96 hours, all three levels of 6, 12 and 18 microliters significantly reduced gas production at all incubation times, even 24 hours, so At the level of 18 microliters, the largest decrease in gas production was observed. Of the three mixtures used, mixture B showed the greatest effect in reducing methane production. Therefore, a dose of 18 μl with a decrease in total gas production and mixture B with a dose of 18 μl with a decrease in methane production has the potential to change ruminal fermentation.

The phylum Pentastomida contains a highly specialized taxon with more than 120 species which infect the respiratory tracts of reptiles and other vertebrates. The species of Pentastomida, a still-enigmatic group of worm-like, linguatula serrata belongs to the bloodsucking parasites that inhabit the upper respiratory tract of terrestrial, carnivorous vertebrates, mostly reptiles and birds; L. serrata, commonly called tongue worms, typically inhabit canids and felids. The intermediate hosts of these parasites are usually sheep, cattle, other ruminants or rodents. The hosts ingest the eggs, and the first instar larva hatches within their intestines, penetrates the mucosa, and retreats into the tissue, where it encysts and molts to the third larval stage. The parasite is tongue shaped, lightly convex dorsally and flattened ventrally. Males measure 1.8–2 cm, while females measure 8–13 cm in length. The nymph of L. serrata is characterised by the possession of a saw-like cuticle with multiple transverse grooves, a ventral buccal apparatus with two pairs of peribuccal hooks and acidophilic glands, a complete digestive system and primordial genital organs. Moreover, in degraded nymphs, the hooks and remnants of the cuticle are often the only findings that allow the diagnosis of the infestation. Humans may be infected with linguatula either by ingestion of nymphs of L. serrate resulting in a condition called nasopharyngeal linguatulosis or Halzoun syndrome or by ingestion of infective eggs which develop in internal organs resulting in visceral linguatulosis. Halzoun syndrome is a rare clinical disease that manifests as an acute allergic-like reaction involving the upper respiratory tract and nasopharyngeal mucosa after the consumption of raw sheep or goat liver, a popular food presentation in Lebanon and other countries of the Eastern Mediterranean region. L. serrata is a common human and animal parasite and affects a wide range of animals, including humans, and causes various diseases in humans. In Iran, this parasite reported from definitive and intermediate hosts in different regions. Also some reports from human Halzoun syndrome it exists in Iran. Diagnosis in final host will be done by clinical signs and separating of the parasite eggs in feces, nasal secretions and animal’s saliva. The diagnosis in intermediate hosts will be done by biopsy. Compression of the electrophoretic pattern of adult and nymph L. serrate proteins obtained from different hosts.

In this study, adult male and female of l. serrate were isolated from the upper respiratory tract of dogs killed by road accident and linguatula nymphs isolated from mesenteric lymph nodes of goats, buffaloes, sheep, cattle and camels. Obtained parasites were separately stored. Collected nymphs of the parasite were washed separately 3 times with 0.85% saline (sterile) and phosphate-buffered saline. The nymph and adult Mouth parts parasites were sonicated on ice with ultrasonicator. After preparing the extract, the protein concentration of parasitic samples was measured by Bradford method and finally, by SDS-PAGE method, the electrophoretic pattern of parasite proteins in different ruminants and dogs was investigated. SDS-PAGE of somatic proteins was performed in different percentage polyacrylamide gels using a discontinuous system as described by Laemmli. The prepared proteins were run on SDS–polyacrylamide gels, composed of 4 % resolving gel and 12 % stacking gel, under reducing conditions using the discontinuous buffer system. For size estimation in SDS-PAGE, a prestained protein marker at a range of 11-180KDa molecular weight (PS10 plus) was used.

Electrophoresis of protein extracts from Mouth parts of different groups of nymphs obtained from different ruminants and adult forms of male and female L. serrata by SDS-PAGE showed a wide range of peptide bands between 8 kDa and 200 kDa. Electrophoresis of Mouth parts of larvae somatic proteins of different groups of parasites (separated from goat, cattle, buffalo, sheep and camel) showed 2 very clear peptide bands with approximate weights of 62 and 53 kDa in SDS-PAGE gel. For proteins prepared from the Mouth parts of cattle and buffaloes, the fine peptide bands did not show much density and were not clear. The status of these bands in the proteins prepared from the oral appendages of camel showed a different pattern from that of other ruminants. It differed from other ruminants in that these bands were clearer than those obtained from cattle and buffaloes and weaker than those from goats and sheep. In male and female adult forms (separated from dog), only the peptide band weighing approximately 62 kDa was present. In the present study, as expected, due to the multicellularity of L. serrate, a wide range of peptide bands in the range of 8 to 200 kDa were found in all samples analyzed by SDS-PAGE. However, there were only two peptide bands in the samples prepared from the oral appendages of the parasitic nodules (about 62 kDa band and about 53 kDa band) and one peptide bond in the proteins prepared from the adult male and female oral appendages (About 62 kDa) were well stained and quite clear, indicating a predominance of peptide concentrations in the mentioned bands.

The prevalence of Linguatulosis is important in ruminants because without any specific clinical symptoms, it leads to reduction of animal productions and hidden economic loss, as well as public health hazards. The results show that the presence of a peptide band with an approximate weight of 62 kDa in all study groups may indicate some of its biological characteristics, especially if we encounter different strains of the parasite is decisive and can be useful in designing efficient serological tests to detect infections in different hosts.

Horses have played an important role in the history of Iranians during different centuries. They kept horses for various aims such as agriculture, transportation, sport, food sources. Iran has a suitable climatic, social and economic potential for keeping and breeding horses, that is why it has been created different breeds using the selection and breeding. But due to problems such as mechanization, lack of government support, export ban, high costs of breeding and maintenance, import of foreign horses, lack of proper planning, interest in keeping horses has decreased. So, unfortunately, only a few native Iranian breeds remain. Additional investigation of the equine genomic architecture is critical for a better understanding of the equine genome, as well as for expanded comparisons across diverse mammalian species. Turkmen and Caspian horses are well-known breeds of Iranian horse breeds. These breeds were historically selected to perform distinct tasks and therefore may harbor a wealth of unique variation at the genome level. Copy number variation (CNV) along with single nonucleotide polymorphisms (SNPs) play a key role in genetic diversity in livestock species. CNVs, a term that refers to a change in the number of copies of a genomic segment, are responsible for more sequence differences between individuals than SNPs and are considered to be a major source of genetic variation contributing to differences in phenotypes (Beckmann et al, 2007). Several studies identified copy number variations in horses using different techniques (Doan et al, 2012). Part of these studies tried to establish associations between CNVs and a specific trait, a disease or even gene expression (Schurink et al, 2017). Most of these studies found either no association or inconclusive associations as the number of horses with phenotypic information or with specific CNVs were limited. For example, a 62 kb duplication on Equus caballus (ECA) chromosome 10 seemed to be related to recurrent laryngeal neuropathy (Dupuis et al, 2013). However, little is known about CNV in Iranian horses.

In this study, detection of CNVs and CNVRs were performed based on SNP data from Caspian and Turkman horse breeds were genotyped via Equine70k SNP beadchip. PennCNV software was only used to detect CNV on autosomes. The PennCNV algorithm was only applied to autosomes (command: -lastchr 26) to identify individual-based CNVs. To increase the confidence of the detected CNVs, quality control was performed by employing standard exclusions of the LRR (standard deviation of LRR) <0.3, a BAF drift <0.01 and a waviness factor <0.05. We classified the status of these CNV into two categories: “loss” (CNV containing a deletion) and “gain” (CNV containing a duplication). The CNVRs were determined by aggregating the overlapping CNVs with CNVRuler. BioMart in the Ensembl database and DAVID was employed to identify genes located in CNVRs and GO terms and KEGG pathway analyses respectively. Quantitative real-time PCR (qPCR) was applied to validate the CNVRs that were detected in this study.

A total of 202 and 105 CNVs and CNVRs were identified in the studied horses, respectively, which cover 1.08% of the horse genome. The number CNVs in Caspian breed were 1.6 times more than Turkmen. Also, the average size of CNVs in Caspian breed was longer than Turkmen. In both breeds, the genetic event of gain was higher than the genetic event of deletion. In Caspian breed, chromosomes 1, 3, 12, and in the Turkmen breed, chromosomes 1, 6 and 12 showed the most changes in CNVs, respectively. Functional analysis showed that the identified CNVRs overlapped with 434 genes and the most of these genes were common between the two horse breeds (more than 60%). Among these genes, PPARG and GALR have potential related with breed-specific traits. The KEGG pathway analysis also identified several pathways that are significantly enriched in olfactory sensory perception, chemical stimulus sensory perception, antigen processing, and G protein signaling pathway. Also, 60% of successfully detected CNVRs were confirmed by Real-time qPCR. The results of this study were compared with the results of eight other studies. For example, we concluded that the average size of the CNVRs detected by the 70k arrays and the 50K arrays were significantly larger than obtained by the CGH and NGS arrays. This may be due to the relatively low coverage and non-uniform distribution of SNP in the equine genome in SNP arrays. Possible reasons for the differences between our results and some CNV studies can be related to different parameters such as sample size and genetic background, different detection platforms and CNV retrieval algorithms, CNV definitions and CNVRs, as well as random error estimation methods (Pinto et al. 2011).

CNVs can describe part of the phenotypic diversity and adaptation evidence in Iranian horses. With regard to Genes identified in a number of cellular components, biological processes and molecular functions within CNVRs, the importance of such CNVRs and the possible effect needs to be studied and may interest insight into the functional and adaptive consequence of CNVs in horse. In total, the number of CNVs in the Caspian breed was greater than in the Turkmen breed, and also the CNV length in the number of copies in the Caspian breed was greater than in the Turkmen breed. In both breeds, there were overlapping genes with CNVRs that were significantly enriched in biological pathways, including sensory perception, immunity, and metabolism. This is the first CNV report on Turkmen and Caspian horses and the findings of this study could provide valuable information for better understanding of the horse genome and also the important performance traits with CNVRs and associated genes for the future studies in horse breeds.

Heat stress as one of the most challenging environmental stresses can growth performance. Broilers are sensitive to heat stress due to the lack of sweat glands. The temperature range for most poultry species is between 16 and 26 degrees Celsius. Heat stress reduces welfare, growth performance, high mortality and large economic losses changes in carcass composition, lipid profile and lipolytic capacity are high under heat stress conditions because heat stress causes significant increases in catabolic and stress hormones (epinephrine, cortisol, and glucagon). Jestrbesk et al. (2017) reported that heat stress increases the activity of fatty acid synthetase (which converts malonyl-CoA to acyl-ACP and acyl-ACP to myristat or palmitate), acetyl cocarboxylase (which it converts acetyl-CoA to malonyl-CoA) and acyl-coasynthetase (which converts myristate to myristate-CoA and palmitate to palmitate-CoA). Liver and adipose tissue are rich in fatty acid synthase, but more than 90% of fatty acid is synthesized in the liver of broiler chickens, and adipose tissue is only responsible for storage (Ijiri et al. 2016). Heat stress, through the increase of lipoprotein lipase in adipose tissue of animals, increases the capacity to harvest and store intestinal and liver-derived triglyceride in adipose tissue (Lu et al. 2007).

The present study was performed to investigate the effect of mild and chronic heat stress on growth performance, carcass traits, blood parameters, meat quality and relative expression of broiler fatty acid synthase and lipoprotein lipase genes. For this purpose, 150 one-day-old male broilers of Ross 308 strain in a completely randomized design with 3 treatments (normal temperature (according to the recommendation of Ross 308 strain), mild stress (27 °C) and chronic stress (32 °C), 5 replicates and 10 birds were kept in each replication from 1 to 42 days. The diet was based on corn and soybean meal and formulated according Ross (308) requirements for three period of starter (1-10 d), growth (11-24 d) and finisher (25-42 d) days. Body weight gain and feed intake was measured periodically and calculated during the whole experiment on a pen basis, and the feed conversion ratio was calculated subsequently. At day 42 of age, two birds per pen were randomly selected, weighed, and slaughtered. After slaughter, percentage of carcass, breast, thigh, abdominal fat, pancreas, liver, heart, bursa of fabricius and spleen were calculated as a ratio of the live weight. To determine the meat quality, 50g of left breast muscle was collected in plastic bags and stored at a negative temperature of 20°C. Meat quality parameters including water holding capacity, moisture, ash, pH, fat, protein, malondialdehyde and total antioxidant activity were measured. Data were analyzed using the general Linear Model procedures of SAS 9.1. When the analysis of variance was significant, Duncan's multiple-range test was used to separate the means. Statements of statistical significance were based on P<0.05.

The results showed that the weight gain of chicks under chronic heat stress in the final period (25 to 42 days) and the whole period (1 to 42 days) was lower than chickens under normal temperature (P <0.05). Exposure to chronic heat stress significantly increased the relative weight of abdominal fat, plasma glucose and triglycerides, and malondialdehyde of broiler breast meat (P <0.05).In agreement with the present result, El-Husseiny and Krieger (1980) also reported that the abdominal fat of broiler chickens under 32 degrees Celsius temperature was more than that of chickens raised at 22 degrees Celsius. Mujahid et al. (2007) stated that heat stress increases plasma levels of fatty acids, triglycerides and cholesterol. The increase of these parameters is probably due to the release of glucocorticoids and the movement of fats, especially triglycerides from the tissues. In agreement with the present result, Lu et al. (2017) reported an increase in the level of malondialdehyde in the breast meat of broilers exposed to chronic heat stress. Heat stress leads to the creation of oxidative stress by increasing the production of free radicals, and the oxidative stress created during heat stress causes an increase in the level of malondialdehyde in skeletal muscles (Vosough-Ghanbari et al. 2010).Chronic heat stress also increased the relative expression of broiler lipoprotein lipase gene in broiler chickens (P <0.05). The relative expression of fatty acid synthase gene also increased significantly in the liver of birds exposed to mild and chronic heat stress (P <0.05). Fatty acid synthase is the limiting enzyme in last step of the synthesis of long-chain fatty acids in animals and the catalysis of acetyl-CoA and malonyll-CoA to fatty acids (Smith 2003). Fatty acid synthesized by liver are incorporated into triacyllglycerols and transported as very low- density lipoproteins (VLDL), which provide this key energy source for other tissues for immediate use or provides storage (Flees et al. 2017).Studies suggest that under stress conditions, high levels of corticosterone and plasma insulin can increase the expression level of LXRa mRNA, which in turn activates the expression of liver SREBp-LC mRNA (Janowski et al. 1999). Therefore, LXRa and SREBp-LC can activate the transfer of key genes required for fat synthesis, such as fatty acid synthase and acetyl cocarboxylase (Demeure et al. 2009). Lu et al. (2007) stated that chronic heat stress negatively affects fat storage and meat quality in broiler chickens, and through the increase of lipoprotein lipase in the adipose tissue of animals, it increases the capacity of harvesting and storing intestinal and liver-derived triglycerides in fat tissue.

In general, exposure to chronic heat stress further decreased yield and increased carcass fat and increased the relative expression of fatty acid synthase genes in the liver and lipoprotein lipase in the breast.

Saccharomyces cerevisiae is one of the most commn probiotics used in ruminant nutrition. Saccharomyces cerevisiae increase gas production through specific biochemical mechanisms. Some of these mechanisms, based on the yeast's ability to excrete excess oxygen from the rumen, create a better space for ruminal anaerobic bacteria. The yeast Saccharomyces cerevisiae can provide a place for metabolic exchange and a suitable environment for the growth and activity of beneficial microorganisms around the substrates. On the other hand, increased gas production by adding yeast may be due to increased propionate fatty acid production due to improved ruminal fermentation. Because carbon dioxide is produced by some rumen bacteria through the succinate-propionate pathway when propionate is produced. Because the fermentation of dietary carbohydrates into volatile fatty acids produces gases in the rumen that are mainly hydrogen, carbon dioxide, and methane, the addition of yeast not only has the potential to improve gas production. , But can cause qualitative changes in the gases produced and reduce the negative impact on the environment. Addition of yeast in concentrated diets increased the population of fiber decomposing microorganisms compared to the control group without adding yeast. Yeast also directly stimulates ruminal fungi, which may improve fiber digestion. Gas production forms the basis of any substrate, mainly dependent on the availability of nutrients for ruminal microorganisms It is quite clear that the increase in gas production was due to the increase in crude protein content. It is well known that Saccharomyces cerevisiae has the ability to reduce the production of ammonia in the rumen. By reducing protein degradation and overall nitrogen excretion by the animal, which helps reduce ammonia emissions from cattle manure. The direct result of this action is an increase in protein bypass in the rumen, which is absorbed and metabolized as a real protein in the gastrointestinal tract and small intestine. Reducing the latency phase by increasing the protein content (for example, a diet with higher crude protein) indicates the rapid activity of Saccharomyces cerevisiae on the fermentation process. In addition, Saccharomyces cerevisiae contains small peptides and other nutrients that are needed by the dominant ruminal cellulite bacteria to initiate growth. The activity of Saccharomyces cerevisiae depends on many factors, including the availability of nutrients to rumen microorganisms, which stimulates the fermentation process. the aim of this study was to investigate the effects of yeast supplementation on fermentation parameters in total mixed rations in vitro.

Accordingly, the effect of 4 levels of yeast supplementation involved, zero, 4, 8 and 12 mg/g of yeast in two TMR diets containing 60 and 70% of concentrates, on the kinetics and parameters of gas production, rumen fermentation parameters including pH, ammonia nitrogen, concentration and profiles of volatile fatty acids, and true digestibility of dry matter and neutral detergent fibers were evaluated. In addition, the effect of yeast supplementation on the population of protozoa, anaerobic fungi and cellulolytic microorganisms were evaluated using molecular techniques. In this experiment, three adult Holstein steers equipped with ruminal fistulas were used to prepare ruminal fluid. For the polymerase chain reaction, after sequencing the primers, DNA extracted was amplified using PCR to check their specificity. DNA amplification was examined by system (R-T PCR) with three replications for each pair of primers.

Addition of different levels of Saccharomyces cerevisiae supplementation caused a significant increase (P <0.05) in the amount of gas produced by increasing the incubation time of experimental diets. The results show that there is a statistically significant difference (P <0.05) between different levels of supplementation, so that from 24 hours after incubation onwards, the highest amount of gas produced in the experimental diets was at the level of 12 mg/g supplement was observed. Addition of different levels of Saccharomyces cerevisiae supplementation caused a significant increase (P <0.05) in the total amount of VFA produced in the rumen with increasing levels of supplementation in experimental diets. The results show that there is a statistically significant difference (P <0.05) between different levels of supplementation, so that the highest amount of total VFA produced in both diets was observed at the level of 12 mg/g supplement. The effect of adding different levels of Saccharomyces cerevisiae supplementation on ruminal parameters caused a significant increase (P <0.05) in ruminal pH and a decrease in ruminal ammonia production by increasing the level of supplementation in experimental diets. The results show that there is a statistically significant difference between different levels of supplementation, so that the greatest increase in ruminal pH and decrease in ammonia production in experimental diets at the level of 12 mg/g. The effect of diet type was also significantly different (P <0.05). The highest increase in ruminal pH and decrease in ammonia production was observed in diets containing 60% concentrate. The results of this study showed that the yeast supplementation in high fermentative TMR diets, increased (P<0.05) the rumen environmental stability, increased (P<0.05) the fermentability of dietary insoluble fraction, reduced (P<0.05) the gas production rate and reduced (P<0.05) the lag phase. degradation of nutrients without affecting the digestibility of insoluble fibers in neutral detergents and the digestibility of insoluble fibers in acidic detergents with diets containing higher crude protein, even with the addition of Saccharomyces cerevisiae, dry matter digestibility showed improved.

Yeast supplementation improved fiber digestibility and reduced lactate accumulation and LPS concentration by stabilizing the an-aerobic environment in the rumen and stimulating the growth and activity of fiber-degrading microorganisms.

Seasonal breeding mammals are sensitive to changes in day length. Thus, in small ruminants from temperate and subtropical latitudes, photoperiod is the main environmental factor that modulates their pattern of reproductive activity (Duarte et al., 2010). However, natural oscillations in the photoperiod or alterations by artificial photoperiod can lead to changes in milk production in ruminants with seasonal and non seasonal reproduction (Dahl et al., 2000). Exposure to artificially shortened photoperiods during the dry period increased their milk yields in the subsequent lactation (Auchtung et al., 2005; Mabjeesh et al., 2007). In the 12 wk of subsequent lactation, greater milk yields have been reported for does that received artificial short days during the dry period than those that received long days (Mabjeesh et al., 2007). Many livestock breeders in cold regions keep their animals in closed places in late autumn and during winter. In the closed position, the amount and intensity of light can be controlled. Short day length at the end of the pregnancy period is associated with increased milk production in lactating animals, but there is no information in this field for native goats in the country. Therefore, the aim of this research was to investigate the effect of reducing the length of the lighting period in late pregnancy on milk production and related hormones in black goats native to Chaharmahal and Bakhtiari province.

The work was conducted in the Farsan city (50º and 35' minutes of longitude and 32º and 16' of latitude and 2020 meters above sea level) located in Chaharmahal and Bakhtiari provinces. 40 indigenous black goats were randomly assigned to one of the following two treatments. Treatment 1: control; Female goats that were exposed to natural day length during pregnancy (20 heads). Treatment 2: Female goats that were exposed to short day length (8 hours of light and 16 hours of darkness) during the last 45 days of pregnancy (20 head). The female goats of two different treatments were reared in two separate locations of the same size with the same environmental and management conditions during the late pregnancy period (experimental period). The quantity and quality of feed was similar for both groups. After giving birth, all female goats were exposed to natural day length. Hand milking was done at one week intervals from one week to one month after birth. Blood samples were taken from jugular vein at the beginning of the experiment, 20 days before parturition, at the time of parturition, 15 and 30 days after parturition.

In the first week, milk production in the experimental treatment was 11% more than the control treatment, but in the second, third and fourth weeks, this superiority reached 13, 16 and 21%, respectively. On average, milk production in the experimental treatment was 15% more than the control treatment. In dairy goats, it was reported that milk production in the subsequent lactation period was 26% higher in goats that were exposed to short day length conditions in the last third of their pregnancy than goats that were exposed to long day conditions at the same time (Mabjeesh et al., 2007).The interaction between the treatment and the milk measurement time was not statistically significant. Milk production peaked in the third week in the control group and in the fourth week in the experimental treatment. Changing the duration of lighting at the end of pregnancy did not have a significant effect on any of the milk compounds on the seventh, fourteenth, twenty-first and twenty-eighth days of lactation. Normally, the composition of milk is not affected by photoperiod (Mabjeesh et al., 2007).The amount of prolactin hormone in the control treatment 20 days before delivery was higher than the amount of prolactin hormone in the experimental treatment at the same time (p<0.05). It has been found that short day length reduces the secretion of prolactin (Smith 1998). In both treatments, the amount of prolactin hormone increased from 45 days before delivery to 30 days after delivery. At the time of parturition, the amount of prolactin hormone in female goats of both treatments was similar. Within each treatment, the amount of prolactin hormone in female goats 15 days after giving birth was higher than its value at the time of giving birth, and the amount of prolactin hormone at the time of giving birth was higher than its value at 20 days before giving birth, and these differences were statistically significant (p<0.01). However, within each treatment, the difference in the amount of prolactin hormone in female goats between the 30th and 15th days after birth was not significant. The interaction effect of treatment and prolactin measurement time was statistically significant (p<0.05). Within each treatment, the amount of prolactin hormone in female goats 15 days after giving birth was higher than its amount at the time of giving birth, and the amount of prolactin hormone at the time of giving birth was higher than its value at 20 days before giving birth, and this difference were statistically significant (p<0.01). However, within each treatment, the difference in the amount of prolactin hormone in female goats between the 30th and 15th days after birth was not significant. The interaction effect of treatment and prolactin measurement time was statistically significant (p<0.05). The average melatonin hormone before and during delivery in treatment 2 was higher than the control treatment (p<0.01), but after delivery the difference between the two treatments was not significant. The amount of IGF 1 hormone in female goats of both treatments decreased from 45 days before calving to the time of calving and then increased.The amount of IGF-1 hormone in the experimental treatment was higher than the control treatment in 20 days before delivery (p<0.01) and at the time of delivery (p<0.05).

As a result, reducing the length of the lighting period at the end of pregnancy increases the milk production of native black goats in the subsequent lactation period.

The existence of geographical diversity in Iran has been caused a significant racial diversity in the domestic livestock and poultry of the country. The number of racial groups of indigenous chickens is not exactly known, but some researchers have been reported up to 35 racial groups. Natural selection during successive generations in environmental conditions has been caused the adaptation these breeds and the evolution of many unique and valuable talents in them. Raring native chickens in order to provide animal protein is widespread in the country's villages and it is valuable from economic point of view. On the other hand, native breeds are considered as important genetic reserves and are considered as national genetic capitals. Studying and researches is necessary in order to preserve these genetic resources. To carry out this research, fertilized eggs were collected from different regions, especially East Azarbaijan province, and placed in the incubator machine separately and chicks were produced in industrial incubation conditions for 21 days. Raring of chickes until maturity and egg production stage took place in Saeed Abad educational campus of East Azerbaijan Agriculture and Natural Resources Research and Education Center. Chicks produced at different ages were weighed and their production and reproduction traits were measured after maturity. This bird is currently spread in various region of East Azarbaijan Province (especially Marand, Tabriz, Sufian, Khosrowshahr, etc.) and also some provinces like Gilan, Alborz, Isfahan, West Azarbaijan, Ardabil, Zanjan, etc . The whole body of the black Marandi chicken is covered with black feathers, which cover the feathers in a uniform black color. The black feathers of this bird reflect a pale green color when the sun shines. The cover of black feathers of this bird extends to the legs, which are thinner and more beautiful than the feathers of the body.The results showed that the live body weight of birth in female chicks is 31.28±3.33 gr and in male 33.12±4.00 gr. But in general, the birth weight of male chickens for the whole population was 31.90±3.66 gr, which obtained from eggs with an average weight of 47.32±7.10 gr. At the age of week 4, male chickens of Marandi breed were about 26% heavier than females and reached an average of 196.36±73.76 gr, but the weight of females was 155.58±64.94 gr. At the end of week 8 of age, male Marandi chicks reached an average of 504.31±115.91 gr and female chickens reach 377.45±124.78 gr, the weight difference of the two sexes reached about 127 gr. Male chicks were 33.6% heavier than females. The weight of female chicks at the end of 12 weeks was about 675.33±151.07 gr and the weight of male at this age was measured on average at 929.97±119.65 gr, the difference between the two sexes reached 254.64 gr and male chickens were about 37.7% heavier than female chickens. Marandi chickens at the end of 16 weeks have a weight equal to 849.77±183.31 gr in females and 1152.64±161.88 gr in male, which are almost 302 gr heavier than females and have a 35.6% increase in weight. At the age of 20 weeks, Marandi female chickens weighed 1040.35±219.64 gr and its male weighed about 1406.15±220.81 gr. The difference in the weight of the two sexes at this age reaches about 366 gr. At the end of 24, 28 and 32 weeks, females reach the weight of 1186.97±175.40 gr, 1409.54±165.67 gr and 1426.97±179.04 gr respectively, while the weight of males at these week is 1609.47±227.63 gr, 1800.05±164.38 gr and 1812.41±239.54 gr respectively. The trend of weight gain up to 12 weeks is incremental, which means that the slope of weight gain is higher in the second 4 weeks compared to the first 4 weeks, and this situation is repeated in the third 4 weeks compared to the second 4 weeks. But after the end of the 12th week until the end of the 28th week, the trend of weight gain has been almost constant, that can be seen is the insignificant and negligible difference in the weight in the 32nd week compared to the 28th week. Which means that until the age of 28 weeks, Marani chickens have spent their weight gain period and after that, growth should not be expected.The breeding results showed that the start of egg production in the Marandi breed is at the end of 5 months (150 days) and at this age they gradually start to lay eggs. At the end of three weeks from the start of laying eggs, egg production reaches its peak, which is about 44% and lays eggs with almost the same percentage until the end of the production period. Marandi chickens produced more than 160 eggs during the one-year laying period after starting to lay eggs. The average weight of Marandi eggs is 47.32±7.10 gr and its average specific weight is 1.075±0.006 gr/cm3. The results of the study showed that the average strength of eggs is 2.64±0.31 kg/cm2. The weight of the egg shell is 4.42±0.73 gr, and its thickness is 0.27±0.03 mm. Haugh unit, albumin height, albumin weight and yolk weight were estimated as 86.03±9.40 %, 6.92±1.53 mm, 29.36±5.99 gr and 14.10±1.74 gr in Marandi breed egg, respectively. Approximately, 10% of the egg weight is the shell, 30% is the yolk, and 60% is the albumin. Fertility rate of Marandi breed eggs in the conditions of natural insemination and using one male for every 10 chickens is 82.38±11.09 % and the hatchability is 76.85±12.33 %. Marandi chicken has good potentials for supplying some part of the food protein source.

During the last two decades, the use of antibiotics in poultry diets as animal growth promotors and growth inhibitors of harmful microorganisms has been stopped in different parts of the world (Roth et al., 2019), which led to a decrease in poultry performance and an increase in the prevalence of diseases (Jha et al 2019; Adhikari et al 2020). Researchers have proposed various ways to improve production efficiency, including the use of probiotics, prebiotics, symbiotic, plant extracts, enzymes and organic acids (Gadde et al 2017; Yadav et al 2019). As the age of laying hens increases, the quality of the egg shell decreases, which is due to the increases in weight and size of eggs, the direct effect of age on the structure of the shell, decreased bone calcium uptake and etc (Curtis et al 2005; Curtis 2008). Heat stress has negative effects on the human health and animal performance and product quality. High ambient temperatures cause reduced egg production, egg weight, egg quality (especially egg shell thickness and strength), impaired immunity and poor poultry welfare (Elnagar et al 2010, Ebied et al 2012). The impaired performances of poultry subjected to heat stress (HS) have been associated with a number of factors, including poor appetite and reduced feed intake (due to activation of the hypothalamic-pituitary-adrenal axis), impaired digestion and metabolism, altered endocrine status (increased corticosterone concentration and reduced thyroid hormones concentrations), metabolic shifts at the systemic and cellular levels and changes in body composition (Elnagar et al 2010, Azad et al 2010, Ebied et al 2012, Safdari-Rostamabad et al 2017). Therefore, it is important to design the strategies or ways of minimizing the negative effect of heat stress as part of methods to maintaining egg production, egg quality and poultry welfare. There are several strategies to reduce the effects of heat stress in the laying hens, including use of feed additive, vitamins, organic minerals and antioxidants. In this study, researchers evaluated the effects of MultiAct-L® (Contains probiotics, prebiotics, organic acids, enzymes, organic form of Zn, Mn, Cu, Fe, Co, Cr and antioxidants) on production performance, egg quality, Newcastle disease antibody titer, antioxidant capacity and gut morphology of laying hens subjected to HS in late laying cycle.

Two hundred and sixteen LSL-Lite laying hens (90 weeks of age) were randomly assigned to three dietary treatments with six replicates and twelve birds in each replicate. Dietary treatments were: 1) basal diet based on a corn-soybean meal 2) basal diet with 0.3 % MultiAct-L® and 3) basal diet with 0.5% MultiAct-L®. The birds were exposed to 36±1°C for 6 hours per day. Egg production, egg weight, feed intake, egg mass and feed conversion ratio were recorded weekly and mortality was recorded daily. Egg mass was calculated by multiplying the total number of eggs laid per hens by the average egg weight. At the end of experimental period, one bird from each replicate (close to cage average weight) was slaughtered, and blood samples were taken for analysis. Blood samples were collected from the jugular vein and then serum samples were separated at 3000 ×g for 10 min. Total antioxidant capacity, malondialdehyde, glutathione peroxidase, superoxide dismutase, glucose, cholesterol, triglycerides, uric acid, albumin, calcium and phosphorus were measured using analytical kits. Serum titer to Newcastle disease virus was determined by hemagglutination inhibition test. Villus height, villus width, crypt depth, villus surface area and villus height/crypt depth were measured in the jejunum section of the small intestine. The data were analyzed using the general linear model procedure of the SAS (2003). The Duncan multiple range test was used to determine the significant differences between treatment means.

MultiAct-L® did not affect the body weight gain of laying hens (P>0.05). The results also showed that feeding MultiAct-L® enhanced the feed intake, egg production, egg weight and egg mass (P<0.05). Feed conversion ratio was improved and mortality was lower in the treatments receiving 0.3 or 0.5% MultiAct-L® than the control group (P<0.05). In agreement with our findings, Deng et al. (2012) and Zhang et al. (2017) reported the significant increase of egg production, feed intake and egg weight by dietary supplementation of probiotic in laying hens subjected to HS. Supplementation of 0.3% MultiAct-L® to diet decreased the abnormal eggs (P>0.05). Shape index, Haugh unit, yolk weight, albumen weight, shell weight, shell thickness and egg specific gravity were not affected by dietary treatments (P>0.05). Similarly, Bozkurt et al. (2012) showed that egg quality parameters weren’t affected by dietary supplementation of essential oil or mannan oligosaccharide in laying hens subjected to heat stress. MultiAct-L® supplement did not significantly affect the titer of antibody against Newcastle disease virus at days 10 and 30 post-vaccination (P>0.05). There was no significant difference in the total antioxidant capacity and glutathione peroxidase among experimental treatments (P>0.05); however, dietary MultiAct-L® supplementation had increased the superoxide dismutase levels and decreased malondialdehyde levels in serum (P<0.05). Blood glucose, cholesterol, triglycerides, uric acid, albumin, calcium and phosphorus in experimental treatments were not significantly different between the control group and the MultiAct-L®-treated groups (P>0.05). No significant changes in villus height, villus width, villus surface area, crypt depth and villus height to crypt depth ratio were observed between three groups at the end of the 8 weeks experimental period (P>0.05). Similarly, Deng et al. (2012) showed that villus height, villus width, crypt depth in the ileum weren’t affected by dietary supplementation of probiotic in laying hens subjected to HS.

As for the results of this study, Multiact-L® could improve laying performance and antioxidant status in laying hens subjected to heat stress during the late laying period.

The growing population and increasing demand for agricultural products, including protein products such as chicken meat due to limited resources, have made it necessary to improve the productivity of inputs. Since the technological change is one of the significant components of productivity change, therefor, the present study was conducted to evaluate the trend and nature of technological change in the Iranian poultry industry.

For this purpose, required data were collected from 27 provinces during the period 1996-2017. In the present study, a cost function approach is used as a basis for estimating technological change using panel data. Technological change may be neutral or biased, depending on how the relationship between inputs is affected. The estimation is based on an output and multi-input Translog cost function. The Translog function has the advantage of being a flexible functional form. The parameters of the cost function were estimated on the basis of the model system including the cost function and four of the five share equations using Seemingly Unrelated Regression (SURE). The estimation was performed imposing the normal symmetry conditions. The F-Limer test is used to measure whether the data are panel or pooled. Then the Hausman test is then used to determine the use of the fixed or random effects model. In order to estimating the system of equations, one of the equations of input cost share is eliminated and all cost function equations and share of input demand are estimated simultaneously. In the model used, the price of all inputs was divided by the price of one-day-old chickens.

The estimation of the models performed relatively well. There was a very high degree of explanation, and most of the parameters had the expected sign. The estimation gave a very high degree of explanation, so that the value of R2 was equal to 0.96. The rate of technological change in some provinces that used the latest technology was above the national average. A negative sign in technological change indicates a decrease in the growth of production costs over time. Thus, it can be seen that the improvement of technology, the use of new production methods as symbols of technology, has reduced the cost of the poultry industry. Using the original breed of day-old chickens, poultry feed and high-quality materials, benefiting from efficient heating and cooling system are among the symbols of technological change. This shows that by using different forms of technology, poultry units have been able to increase the amount of chicken meat production. The rate of technology change has been declining until 2014 and reached its minimum in that year. That is, in 2014, compared to other years, the cost of producing each unit of chicken meat in poultry farms in different provinces of the country has decreased. The results of pure technological change showed that in all years under review, the amount of neutral technological change was positive and its average was 0.93. In general, it can be said that the process of changing pure technology over time has increased the production cost. The results of changing the input biased technological change showed that its average values were -0.26. Thus, it can be said that in the production of broiler chicken, technological developments have led to savings in production factors. the average rate of technology change was -1.61 percent over the mentioned time period, which means that in the study period the rate of cost change of production units has been decreased. Since cost elasticity was less than one (0.37), so the production is faced with the increasing return to scale. Therefore, the reduction in the cost causes economic savings in the production process.

According to the results of this research, the technology has changed in order to use more poultry feed; In other words, the technological change in the Iranian poultry industry is energy and labor saving. The results of cost elasticity, which was less than one, showed that product production in these units has an upward return to scale, so it confirms the existence of economies of scale in the poultry industry. Finally, it is suggested that the poultry industry utilizes the new technology and increases the production scale in order to access comparative advantage.