فصلنامه تحقیقات تولیدات دامی
سال سیزدهم شماره 1 (بهار 1403)

In recent years, consideration has been given to changing the sex of a female bird to male because it has the functional characteristics of the male phenotype, and the technique of in ovo injection is used to achieve this. For this purpose, the production process of some sex hormones in broiler chickens is changed by injecting a substance containing anti-aromatase. The aromatase enzyme (Arom P450) is considered a key enzyme in estrogen synthesis. The administration of aromatase inhibitors leads to the inhibition of estrogen synthesis (a hormone responsible for ovarian structure and secondary sexual characteristics) in females and the production of males with female genotypes. Therefore, if aromatase enzyme expression is inhibited in some way, it can be expected that the percentage of male chicken production will increase. Aromatase inhibitors can be divided into two main groups in terms of production source, including synthesized and herbal compounds. Among the herbal extracts containing anti-aromatase are nettle root, button mushroom, garlic, green tea, and tomato. On the other hand, the results of some studies have shown that the performance indicators of male and female poultry during the breeding period, such as daily feed intake (DFI), daily weight gain (DWG), feed conversion ratio (FCR), as well as the activity of the digestive system, especially the small intestine, are different and the ability to use nutrients, growth rate and FCR are better in males than females. According to male poultry characteristics, if the number of males in the flock increases, more profitability can be achieved in the production process. Therefore, the objectives of the current study were to determine the effects of in ovo injection of nettle extract, mushroom extract, and their mixture on hatched chickens, performance, and intestinal indicators of Ross 308 broiler chickens. This study was conducted to investigate the in ovo injection effects of nettle and mushroom extracts, and their mixture on hatchability, the percentage of male chickens produced, and some intestinal parameters in broilers. 500 fertilized eggs were divided into five treatments and four replicates (25 eggs per replicate). Experimental treatments included: 1. Nettle hydroalcoholic extract (containing 300 micrograms of dry matter per 0.1 cc of injectable substance), 2. Mushroom hydroalcoholic extract (containing 500 micrograms of dry matter per 0.1 cc of injectable substance), 3. Mushroom and nettle extracts mixture (containing 400 micrograms of dry matter per 0.1 cc of injectable substance), 4. Positive control (distilled water), and 5. Negative control (eggs without any injection). The experimental design was a completely randomized block design. Samples were divided into five treatment groups, with each treatment group having four replications based on the gender segregation of the chicks into male and female. The experimental diet was used based on the requirements of the Ross strain during three periods, including starter, grower, and finisher. After the chickens were hatched, performance and intestinal indices were measured. The results showed that the number of hatched chicks was affected by experimental treatments. Therefore, the lowest hatch percentage was related to URE treatment chicks. The number of normally hatched male chickens, performance indices, and intestinal parameters were not affected by the experimental treatments (P>0.05). The lack of significant difference in the number of male chickens in the experimental treatments may be due to the incorrect selection of the concentration of the experimental extract. Furthermore, villi height, crypt width, and villi surface absorption area were not affected by experimental treatment (herbal extracts). In comparison, DWG and FCR significantly improved by the sex effect (P<0.05). Regarding the difference in the performance of male and female broiler chickens, it has been reported that these two sexes have a significant difference in DFI and FCR. It has also been reported that the increase in BWG and the weight of different parts of the carcass in males was higher than in females, which is consistent with the findings of the current research regarding all three indicators of DFI, DWG, and FCR. Although there was no significant increase in the number of hatched male chickens in this study, it is recommended to optimize the preparation and production conditions of plant extracts containing anti-aromatase by focusing on extracting the pure active ingredient to achieve a higher percentage of male chickens in the flock. This study was conducted to investigate the in-ovo injection effects of nettle and mushroom extracts and their mixture on hatchability, the percentage of male chickens produced and some intestinal parameters in broilers. 500 fertilized eggs were divided into 5 treatments and 4 replications (25 eggs per replication) in a completely randomized design. Experimental treatments consisted: 500 fertilized eggs were divided into 5 treatments and 4 replicates (25 eggs per replicate) in a completely randomized design. Experimental treatments consisted: 1- nettle hydroalcoholic extract (containing 300 micrograms of dry matter per 0.1 cc of Injectable substance), 2- mushroom hydroalcoholic extract (containing 500 micrograms of dry matter per 0.1 cc of Injectable substance), 3- mushroom and nettle extracts mixture (containing 400 micrograms of dry matter per 0.1 cc of Injectable substance), 4- positive control (distilled water) and 5- negative control (eggs without any injection). The experimental diet was used based on the requirements of the Ross strain during three periods, including starter, grower and finisher. After the chicken were hatched, performance and intestinal indices were measured. The results showed that the number of hatched chicks were affected by experimental treatment. So that, the lowest hatch percentage was related to URE treatment chicks. The number of normal hatched male chicken, periodic performance indices and intestinal parameters were not affected by the experimental treatments (P>0.05). The lack of significant difference in the number of male chicken in the experimental treatments may be due to the incorrect selection of the concentration of the experimental extract. Furthermore, villi heigh, crypt width and villi surface absorption area(VSA) were not affected by experimental treatment (herbal extracts). In comparison, DWG and FCR significantly improved by the sex effect (P<0.05). Regarding the difference in the performance of male and female broiler chicken, it has been reported that these two sexes have a significant difference in DFI and FCR. It has also been reported that the increase in BWG and the weight of different parts of the carcass in males was higher than females, which is consistent with the findings of the current research regarding all three indicators of DFI and DWG as well as the FCR. Although there was no significant increase in the number of hatched male chickens in this study, it is recommended to optimize the preparation and production conditions of plant extracts containing anti-aromatase by focusing on extracting the pure active ingredient to achieve a higher percentage of male chickens in the flock.Key words: nettle and mushroom extract, ant i-aromatase, broiler chicken, plant extract, in-ovo injection

Today, the increase in the world's population, especially in third-world countries, has caused an increase in the demand for livestock products, which will subsequently require more livestock products and more food resources to meet these needs. The use of waste from factories of agricultural transformation industries in feeding livestock helps to make the cost of breeding more economical. Since cotton by-product is considered a product of cotton ginning factories, it can be said that due to its nutritional value, its use in animal diets is to avoid wasting this huge source of feed. Cotton by-product contains 86.9% dry matter, 12.3% crude protein, 57.7% NDF, 12.2% ash, 1.7% calcium, 0.31% phosphorus, and 1.06% net energy. The results of the studies showed that cotton waste can be used as a source of protein in the diet of fattening animals. This study aimed to assess the effect of feeding different levels of cotton by-products on performance, degradability, rumen fermentation parameters, microbial protein, and microbial population in fattening lambs.
In this study, 24 male Afshari lambs with a mean weight of 30±0.7 kg and a mean age of four months were used in a completely randomized design with four treatments and six replications for 90 days. The experimental treatments included: 1) a diet without cotton by-product (control), 2) a diet containing 33.33% cotton by-product instead of alfalfa, 3) a diet containing 66.66% cotton by-product instead of alfalfa, and 4) a diet containing 100% cotton by-product instead. Hay was based on dry matter. The cotton by-product used in this study was obtained from Mahosh cotton ginning factory located in Razavi Khorasan province, Neyshabur city, Iran. After entering the test site, it was chopped and then mixed with alfalfa in certain percentages; it was consumed by experimental lambs. Growth performance traits including daily feed intake, daily weight gain, and feed conversion ratio were measured during the experiment period. To measure ruminal fermentation parameters and bacteria and protozoa populations, the rumen fluid of the experimental lambs was taken from the rumen on the 90th day of the experiment, three hours after morning feeding using an esophageal tube. To determine urine purine derivatives, the total 24-hour urine production of each animal was collected in a special container under the metabolic cage on five sampling days. The number of three fistulaized Afshari sheep with a mean weight of about 50±2 kg and a mean age of approximately 11 months was used to estimate the parameters of degradability of dry matter, crude protein, and NDF.
The growth performance results showed that replacing 100% cotton by-products instead of dry alfalfa increased feed intake, increased daily weight, and decreased feed conversion ratio (P<0.05). The results of ruminal parameters showed that the treatment containing 66.66 and 100% replacement of cotton by-products instead of dry alfalfa had the highest concentration of total volatile fatty acids, acetic acid, and acetate to propionate ratio (P<0.05). There was no significant difference between the experimental treatments in the amounts of purine excretion derivatives and microbial protein production. The use of 66.66% of the substitute cotton by-product instead of dry alfalfa in the diet increased the total population of rumen fluid bacteria (P<0.05) but had no significant effect on the protozoan population. The results of meta-measures of dry matter degradability, crude protein, and NDF showed that there was no significant difference between experimental treatments.
The general results of the study showed that replacing cotton by-products by 66.66 or 100% instead of dry alfalfa in the diet improved the performance, increased the bacterial population, and concentration of total volatile fatty acids in the rumen fluid of fattening lambs. The use of cotton by-products can be a suitable substitute for alfalfa in the diet of fattening lambs without negative effects on growth performance and rumen fermentation indices.

During the time around parturition, animals make many metabolic adjustments to support the transition from pregnancy to lactation. Before giving birth, animals are subjected to a lot of metabolic effects, to prepare the physiological conditions of the body in the time after giving birth and during lactation. In addition, dairy cattle produce milk more than their ability to consume energy, as a result, they are in a negative energy balance at the beginning of lactation, which may reduce the longevity of the cattle in the herd and increase the rate of elimination of dairy cattle. Heat stress in late pregnancy is aggravated by energy restriction. In such conditions, the use of management and nutritional methods will reduce the problems during the transfer period and heat stress. One of the ways to optimize the productive and reproductive conditions of livestock, through improving the metabolism of nutrients and eliminating or reducing stress conditions, is to use chromium as a metabolic improver. According to scientific sources, the chromium requirement for sheep is three to five mg per day, and for dairy cows is 15 to 50 mg per day. Inorganic chromium has a bioavailability of about 0.5%. Organic chromium has more than 25% intestinal absorption, and therefore, consumption of inorganic chromium is not recommended due to its low bioavailability and toxic effects. Among the sources of organic chromium, chromium-methionine has been recognized by important global food and drug organizations as a compound with high bioavailability, impressive metabolic responses, and no toxicity complications. This experiment was conducted to investigate the effect of using different forms of chromium around calving on feed consumption, nutrient digestibility, nutritional behavior of Afshari ewes, and the performance of their lambs under the influence of heat stress.
Forty pregnant Afshari ewes were assigned to four experimental treatments with 10 replicates from 42±5 days before the expected birth in a completely randomized design. Experimental treatments include 1) a basic diet without chromium supplementation (control), 2) a basic diet containing three mg of chromium in mineral form per kg of dry matter, 3) a basic diet containing three mg of chromium in the form of chromium-methionine per kg of dry matter, and 4) a basic diet contained three mg of chromium in the form of chromium nanoparticles per kilogram of dry matter. The length of the test period was 84 days. Weighing of ewes was done at the beginning, at the time of calving, and the end of the period. The rest of the feed is weighed every day and the daily feed consumption was calculated by deducting from the provided feed. Sampling of the rumen fluid was done on the 14th day after birth. The rumen fluid was taken before feeding in the morning (zero hour), and at three and six hours after feeding by esophageal tube, then the pH amount of rumen contents was measured and recorded immediately after extraction by a mobile digital pH meter (Metrohm laboratory pH meter-691) which was calibrated at the same place. To measure rumen liquid ammonia nitrogen, samples were used three hours after morning feeding. To measure the concentration of volatile fatty acids, five mL of rumen fluid samples were prepared and 1 mL of metaphosphoric acid 25% was added to them and kept at -20ºC until the experiment. On the 10th day after birth, blood samples were taken from the jugular vein of ewes and lambs three hours after morning feeding. To measure blood metabolites including glucose, insulin, cholesterol, triglyceride, urea, creatinine, total protein, albumin, and globulin, Pars Azmoun chemical kits and auto-analyzer (Spain BT 3500) were used.
The results showed that, from the third to the sixth weeks after birth, dry matter consumption in ewes receiving chromium-methionine and chromium nanoparticles had an upward trend compared to the other two treatments (P<0.05). The addition of chromium to the diet of ewes had no significant effect on rumen pH, volatile fatty acids, and rumen ammonia nitrogen concentration. The addition of chromium supplement to the diet of ewes caused a significant decrease in the rumen protozoa population compared to the control group (P<0.05). Adding different forms of chromium to the diet of sheep caused a decrease in glucose concentration, and an increase in chromium, insulin, total protein, albumin, and serum globulin compared to the control group (P<0.05). No significant difference was observed between experimental treatments on blood cholesterol, triglyceride, urea, and creatinine concentrations. Also, different forms of chromium did not have a significant effect on the blood parameters of the born lambs.
In general, the use of chromium, especially in the form of chromium-methionine and chromium nanoparticles, is recommended during the transfer phase of sheep under the influence of heat stress.

Birth weight is the most important factor affecting lamb survival, but even when birth weight is appropriate, some lambs are lost to weaning. Infectious diseases are the most important factors affecting the mortality of lambs before weaning. Therefore, any factor that reduces the prevalence of these infections has a positive effect on the survival of lambs and improves the reproductive performance of the flock. The structure of the placenta in ruminant animals prevents the transfer of immunoglobulins from maternal circulation to the fetus. Therefore, newborn ruminants are completely dependent on the absorption of immunoglobulins from the mother's colostrum after birth. Consuming a sufficient amount of high-quality colostrum at the right time is the most important management factor affecting the survival and health of newborn ruminants. Colostrum also affects the survival of lambs by providing nutrients necessary for metabolism and heat production. Fat-soluble vitamins (A, D3, and E) are among the important components of colostrum and their concentrations are higher in colostrum compared to milk. These vitamins play an important role in improving the immune system of ruminant animals. Many genetic and non-genetic factors such as animal breed, mother's age, nutrition of dam in late pregnancy, herd vaccination program, colostrum volume, and colostrum collection time after parturition affect the quantity and quality of colostrum in ruminant animals. Nutrition status in late pregnancy is the most important factor affecting the quantity and quality of colostrum produced in these animals. Therefore, an insufficient supply of vitamins in pregnant ewes is one of the reasons for reducing the survival and mortality of newborn lambs. Much research has been conducted regarding the effect of dietary or injectable vitamin A, D3, and E supplements in late pregnancy on the maternal immune system and the survival of newborn ruminants, although, they have mainly focused on vitamin E and selenium supplements. To our knowledge, there is no information on how the timing of the use of these vitamins in late pregnancy affects the metabolic responses of ruminants. Therefore, this experiment aimed to investigate the effect of time and amount of vitamin AD3E injection in late pregnancy on colostrum quality and plasma metabolites of Afshari ewes and their lambs. Forty Afshari mature ewes with an average of 45 kg and 2-3 years of age were used. One month before the expected lambing, animals were divided into four groups and randomly assigned to experimental treatments. Experimental treatments were: 1. No injection of vitamin AD3E (Control; C), 2. Injection of 10 mL of vitamin AD3E four weeks before the expected lambing, 3. Injection of 10 mL of vitamin AD3E two weeks before the expected lambing, and 4. Injection of five mL of vitamin AD3E four weeks and five mL two weeks before the expected lambing. Blood samples of ewes and lambs were collected four and one week before the expected lambing and three days after colostrum consumption, respectively. Plasma was separated and stored at -20 ◦C for metabolites’ measurement. Samples of colostrum from all animals were collected and stored at 3-5 ◦C for determining chemical composition and BRIX index. Results showed that the greatest plasma concentrations of glucose and malondialdehyde (MDA) on day 7 before lambing were observed in ewes of the C groups (P<0.05). Experimental treatments did not affect plasma total cholesterol (TCh), triglyceride (TG), and magnesium (Mg) concentrations of ewes on day 7 before lambing (P>0.05). Plasma concentration of total protein (TP), calcium (Ca), and BRIX index on day 7 before lambing were higher in ewes who received vitamin AD3E compared to the C group (P<0.05). Ewes received 10 mL of vitamin AD3E two weeks before the expected lambing had the highest plasma glutathione peroxidase (GPX), superoxide dismutase (SOD), and total antioxidant activities on day 7 before lambing (P<0.05). Colostrum fat and lactose percentage were not influenced by experimental treatments (P>0.05). Whereas, colostrum protein percentage tended to be lower for ewes in the C group (P=0.08). The lowest colostrum BRIX index was observed in the ewes of the C group (P<0.05). The lowest plasma glucose concentration was observed in lambs born from ewes of the C group (P<0.05). Experimental treatments did not affect plasma TCh, TG, Ca, and Mg concentrations of lambs (P>0.05). Lambs born from ewes received 10 mL of vitamin AD3E two weeks before lambing had the highest plasma GPX, SOD, and total antioxidant activities compared to other groups (P<0.05). Vitamin AD3E injection increased the plasma BRIX index of lambs compared to the group without injection (P<0.05). The results showed that injection of vitamin AD3E two weeks before lambing increased plasma TP concentration and antioxidant activity of ewes, as well as colostrum TP content, and consequently increased plasma TP concentration and antioxidant activity of lambs. Therefore, this can be an effective strategy to improve lamb survival and performance.

The shortage of feed, caused by the limitation and reduction of water resources, is the biggest challenge for the country's livestock industry. Every year, more than 20 million tons of by-products from the main agricultural production remain in the country, which are mainly used as animal feed. Agricultural by-products, which exceed the production of forage crops many times over, are valuable resources that can replace conventional feeds in animal nutrition. Due to their low protein content and low digestibility, they need to be processed. For almost a century, different processing methods have been used in many countries depending on the conditions and facilities, but unfortunately, the majority of these materials are still used raw and unprocessed as animal feed in the country, which is a waste of resources. Straw processing is carried out by various physical, chemical, and biological methods or a combination of these methods, with ammoniation being the most important chemical method. The use of ammonia gas for this purpose can facilitate and accelerate processing, especially with large quantities of by-products. This research was carried out to study the efficacy and economics of the method of ammonization of straw with ammonia gas and the use of the ammonia product in the diet of fattening calves.
Ammoniated wheat straw was prepared with ammonia gas at three weight percent of the dry matter of straw at 30% moisture by stacking method, and the chemical composition, digestibility, and gas production of the ammonia-containing product were determined. In the second phase, 30 Simmental crossbred fattening calves with an initial weight of 249.5±8.9 were divided into two control and experimental groups and for each group, considering three replicates of five calves for each group. Normal straw was used in the control group, and it was replaced by ammoniated straw in the experimental group. The duration of the trial was eight months, during which the weight gain of the calves was determined every 30 days, and the dry matter was consumed daily. Dry matter consumption, daily weight gain, feed conversion ratio, and the cost of weight gain of calves were determined and compared between the two groups.
The ammonia treatment of straw increased crude protein content in the ammoniated straw from 4.78% to 12.65%, and the amount of NDF and hemicellulose also decreased in ammoniated straw (from 71.33 to 66.80%, and from 30.75 to 26.25%, respectively), while the amount of ADF increased (from 38.7 to 41.20%). The ammonia treatment of straw increased the gas production per 24 hours from 25.71 mL to 38.06 mL and the estimated metabolizable energy from 5.69 to 6.8 MJ per kilogram of dry matter. The ammonia treatment improved the digestibility of dry matter (from 45.0 to 78.75%) and organic matter of straw (from 42.35 to 80.27%). Substituting normal straw for ammoniated straw in the diet of fattening calves increased daily dry matter consumption from 8.66 kg to 8.99 kg (P<0.01), daily weight gains from 1.33 kg to 1.48 kg, and average weight at the end of the fattening period from 423.98 kg to 440.67 kg (P<0.01), and improved feed conversion ratio from 6.43 to 6.01 (P<0.01). In addition, the use of ammoniated straw reduced the price of ration from 71230 Rials to 69210 Rials and the cost of feed for each kilogram of animal weight gain from 458008.9 Rials to 415952.1 Rials.
Ammoniation of straw with ammonia gas increased the metabolizable energy, crude protein, and digestibility of straw. The use of ammonia gas for this purpose increased the speed, ease, and efficiency of processing, making it suitable for processing large quantities of straw. The profitability of this method depends on the cost of the ammonia product, in particular the price of ammonia gas and its transportation costs. At the national level and from a macroeconomic perspective, this method increased the digestible nutrients of agricultural residues (metabolizable energy and crude protein), it is, in a sense, a type of food production by increasing productivity and without the consumption of water and other agricultural inputs. It provides more nutrients for livestock, which reduces dependence on traditional feed, reduces competition between humans and livestock for food, protects the environment, and makes production more sustainable.

The development of sustainable animal husbandry plays an important role in establishing food security, improving welfare, increasing the income of rural households, improving productivity, creating job opportunities, creating links with other economic sectors, and rural development. In Iran, the issue of sustainable development of the animal husbandry industry and creating sustainability is one of the most important issues of the country because the animal husbandry industry is one of the most important sub-sectors of the agricultural industry, which produces the most important basic food of the country, i.e., red meat. The main goal of this research is to identify and prioritize the obstacles and problems of sustainable animal husbandry development in Guilan province. The development of the agriculture and animal husbandry industry is necessary to access a sufficient amount of food and energy and to cover the ever-increasing demand due to the increase in the population. Guilan province has a suitable capacity for the development of animal husbandry activities. Paying attention to the existing research gaps, by summarizing findings in this field, using the opinion of animal husbandry industry experts, and the application of the multi-indicator decision-making model, this study identified the obstacles and problems for the development of sustainable animal husbandry in Guilan province.

Various criteria have been introduced in previous research as key factors for the sustainable development of animal husbandry, the most important of which included structural, institutional, economic, cultural, social, environmental, macro goals and strategies, the process and cycles of providing inputs, and selling livestock products. The decision tree was drawn using the findings of similar studies and the opinions of provincial experts in this industry. The data collection tool is a questionnaire for pairwise comparisons of decision tree criteria and sub-criteria. To determine the weight of the criteria and sub-criteria included in the decision tree, the opinions of 10 experts in this field in Guilan province were collected and analyzed using the Fuzzy Hierarchy Process (FAHP). Fuzzy set theory is a mathematical theory designed to model the ambiguity of processes related to human knowledge. The decision maker can freely choose the range of desired values. Also, the uncertain judgment of the expert can be expressed by a fuzzy number. In this method, fuzzy numbers are used for the pairwise comparison of options, and the decision maker can express the pairwise comparisons of the elements of each level in the form of triangular fuzzy numbers. The decision tree for this research has five main criteria including institutional, environmental, social and cultural, structural, and economic factors, and 31 different sub-criteria. FAHP is a systematic method that uses the concepts of fuzzy set theory and hierarchical structure analysis. The calculated weights are a suitable basis for prioritizing the main obstacles and problems in the sustainable animal husbandry industry development of Guilan province. Modeling and obtaining the results were done in the MATLAB software.

The results of the research showed that from the point of view of experts, institutional and economic obstacles with the weights of 29.71% and 19.23%, respectively, are considered to be the most important obstacles to the development of sustainable animal husbandry in Guilan province. On the other hand, the sub-criteria of low attention to the animal husbandry sector in the provincial policies from the institutional criterion, the inappropriateness of the materials used, considering the weather conditions from the environmental criterion, the low status and job position of animal husbandry from the social and cultural criterion, the lack of high-yielding breeds consistent with the conditions of the region from the structural criterion, and the lack of adequate insurance coverage from the economic criterion have the highest rank among the sub-criteria.

The obtained results indicated the high level of obstacles and problems for the development of sustainable animal husbandry in Guilan province, which requires the attention of policymakers and the development of a policy package that fits the priorities determined in this study.

The genome-wide association study (GWAS) is a powerful approach to identify genomic regions associated with fertility traits that explain a significant portion of the genetic variance associated with these traits and identify the relevant causal mutations. Evaluating the correlation between each genotyped marker and trait is an essential strategy for GWAS studies that examine the effects of all markers by considering their possible interactions, environmental factors, and even mutual effects between markers. Recently, machine learning methods have been introduced to genomic topics, and the basis of these methods is different from the common methods of genomic evaluation. The machine learning method is used to estimate the genomic breeding values of the candidate animals by considering the training data (genotypic and phenotypic information of the reference population). One of the key advantages of this method is the ability to analyze large data. Machine learning is a branch of artificial intelligence whose goal is to achieve machines that can extract knowledge (learning) from the environment. A variety of machine learning methods (random forest, boosting, and deep learning) are used to model genetic variance and environmental factors, study gene networks, GWAS, study epistasis effects, and genomic evaluation. Random forest is one of the machine learning methods that has been successfully used in various fields of science. This research was conducted to identify markers and genes related to reproductive traits such as calving interval (CI), days open (DO), daughter pregnancy rate (DPR), and age at first calving (AFC) in Iranian Holstein dairy cattle. These traits have already been investigated with the ssGBLUP method and using a smaller sample size. However, in the present research, by using more genotyped animals, a random forest algorithm was used to identify markers and genes related to reproductive traits.
The records used in this research were provided by the National Animal Breeding Center and Promotion of Animal Products of Iran and included AFC, DO, CI, and DPR related to the genotyped bulls' daughters. In this research, the pedigree information of 2774183 animals was used. The genotypic information of the markers related to 2419 Holstein bulls was used. Genomic data quality control was performed using factors such as the number of genotyped SNPs per animal (ACR), the number of genotyped animals per SNP (CR), Hardy-Weinberg equilibrium (HWE), and minor allele Frequency (MAF). When filtering genomic data, the markers whose MAF was less than 5% were removed, and then the samples whose genotyped frequency was less than 90% were identified and removed. Then, the markers whose genotyping rate was less than 95% in the samples were identified and removed. Finally, the SNPs that deviated from the HWE test (P<10-6) were excluded from the analysis as a measure of genotyping error. To control the quality of genomic data, PLINK 1.9 software was used. Then Ranfog software was used in the Linux environment to perform analysis through random forest algorithm.
By using the random forest algorithm, a total of 21 important SNPs were observed, then important fertility trait candidate genes were identified by the gene ontology method, and 62 genes were within 250 Kb of these SNPs. The most significant SNP was observed for AFC. The main SNP for AFC is in ARS-BFGL-NGS-22647 BTA3, for CI is in ARS-BFGL-NGS-114194 (BTA11), for DO is in BTA-74076 -no-rs (BTA5), and for DPR is in ARS-BFGL-NGS-32553 (BTA26). The researchers, who studied fertility traits in Nellore cattle using machine learning methods, identified MPZL1 and CD247 genes on chromosome number 3 and this gene was associated with age at first calving. Many pathways of cell biology affect the performance of reproductive traits. Research has reported the relationship between the CD247 gene and pathways of biology, including cell development and function. Research has shown that the IFFO2 gene plays an important role in the molecular structure of cells, as well as in the mechanism of blastocyst formation, embryos, and the length of gestation in cattle. In a study conducted on the mouse population on the structure of the flagellum and the sperm maturation process, the role of the ALDH4A1 gene in the sperm maturation process was reported. The association of the RPS6KC1 gene with pregnancy rate and antral follicle number in Nellore heifers has been reported. The KAT2B gene is a transcriptional activator that plays an essential role in regulating the correction of histone acetylation and plays an important role in improving carcass quality, muscle and fat development, and metabolism in native Chinese cattle. In addition, they play a key role in regulating biological processes and are related to cell growth, metabolism and immune system function.
  According to the objectives of this research, new information on markers and candidate genes related to reproductive traits in Iranian Holstein dairy cattle was reported. The markers and candidate genes identified in the present research can be used in genomic selection to improve the reproductive traits of Holstein dairy cattle.