مجله علوم دامی ایران
سال چهل و دوم شماره 1 (بهار 1390)

Effects of inbreeding coefficient on estimates of genetic parameters, breeding values and genetic trends for production traits (milk, fat and protein yields), reproduction traits (age at the first calving, interval between first insemination to conception, calving interval, interval between calving to first insemination, and calving ease) as well as longevity of Holstein Cattle in Iran were studied. Inbreeding coefficients were computed using a complete pedigree, created from all available information of national Holstein dairy cattle and international sires back to 1883. For all the traits, the records of animals with a minimum pedigree completeness of 0.7 for five generations back were employed. The average completeness of pedigree for all the record holding animals was more than 0.90. Two univariate animal models (either with or without inbreeding) were considered to estimate the genetic parameters and breeding values. There were no substantial differences between the two models for variance components and genetic parameters. However, the effect of inbreeding on estimated breeding values and genetic gain was significant. Based on the estimated breeding values, the differences in male rankings were greater than those in female rankings for all the traits. Also, the rank correlations between two models ranged from 0.966 (milk yield) to 0.994 (fat yield) for males and 0.953 (calving ease) to 0.997 (age at the first calving) for females. These correlations, which were significantly different from unity, indicated that it is necessary to adjust the effect of inbreeding in genetic evaluation programs.

In order to identify the segre QTL affecting growth traits on the end region of chromosome 18 in a Lori-Bakhtiari sheep population, 162 animals from 5 paternal half-sib families were taken to be studied. Phenotypic data included records of birth weight (BWT), weight at one month of age (W1), weaning weight (WWT), weight at six months of age (W6), chest circumference (GI6), body length (LG6), withers height at six months of age (HT6), weight at nine months of age (W9) as well as yearling weight (W12). Five sires along with their progeny were genotyped for 3 microsatellite markers in a candidate region on chromosome 18. QTL analysis was conducted using regression interval mapping with a single-QTL model. The individual family analysis suggested some QTLs segregating in families 1 and 5. In family 1, a QTL residing between CSSM18 and TMR1 markers was associated with BWT (117 cM), W1 (116 cM) and WWT (118 cM) (P<0.01). Also, in family 5, a QTL located between CSSM18 and TMR1 markers was linked to GI6 (114 cM) (P<0.01) and HT6 (113 cM) (P<0.05). Joint analysis of families 1 and 5 proposed some QTL related with W1 (P<0.01), WWT (P<0.05) and GI6 (P<0.01) being located at 113, 118 and 118 cM, respectively. A final analysis of all the families indicated a significant QTL affecting W6 (not previously verified) employing individual family analysis. In the joint analysis of all the families, QTL for W6 was positioned at 106 cM close to CSSM18 marker (P<0.05). An overlapping of the position of detected QTL with that of Carwell gene suggest that this gene is a strong candidate for the observed QTL effects.

This trial was conducted to evaluate the effects of different dietary factors that affect egg cholesterol concentration in laying hens of 56 to 70 weeks of age. Three hundred and ninety six Hy-Line W36 laying hens were subjected to 11 experimental treatments, each treatment consisting of 4 replicates, each replicate of 9 hens. Dietary treatments included the control, made up of corn plus soy meal with an AME content of 2750 kcal/kg; vs. experimental treatments comprised of control diet supplemented with 2 and 4% canola oil, 2 and 4% tallow, 1 and 2% garlic powder, 0.1 and 0.2 % probiotic and finally 125, vs. 250 mg/kg of copper in the form of cupric sulphate. All experimental groups received AME plus other nutrients on an equal basis. Egg production and weight were assessed on a daily basis. During the laying period from 58 to 70 weeks of age, egg production rate, egg, feed intake, FCR, albumin quality and weight, shell thickness and fractional shell weight were found out as not differing among treatments. Yolk weights were significantly higher when 1%, and 2% garlic powder as well as 125, 250 mg/kg of Cu were added to the diets (P<0.05). Adding 125 and 250 mg/kg of copper to the laying hen's diets reduced egg cholesterol concentration by 23.4 and 26.5 percent respectively (P<0.01). Egg yolk cholesterol concentration decreased significantly in birds fed 1 and 2 percent of garlic powder (14.47 and 16.2% as compared to control group) (P<0.01). Probiotic treatment increased the serum cholesterol level significantly. In conclusion, it was found out that an inclusion of 125 mg/kg of cu plus 1% of garlic powder in the laying hen's diets can decrease yolk cholesterol concentration without bringing about any adverse impacts on the hen's production performance.

The present study was conducted to determine the effects of different levels of rice bran along with a multi enzyme on the performance of broiler chicks. Three hundred eighty four day-old male broiler chicks were taken in 8 treatments comprised of different levels of rice bran (0, 6, 12 and 18%) together with a multi enzyme (0 and 0.1%). Each treatment was carried out in 4 replicates each replicate comprised of 12 chicks. The experiment was a factorial one done in the framework of a completely randomized design. Increasing the level of rice bran in the diets decreased the chick's body weight as well as weight gain while increasing feed conversion ratio in them. Feed intake and blood factors were not affected by different treatments (P>0.05). Weights of gizzard, liver, small intestine as well as ceca were affected by inclusion of rice bran. There were no significant effects of enzyme supplementation observed on broiler's performance, but there were significant effects observed on abdominal fat, blood glucose and triglycerides. No significant effect of total feed cost/Kg of body weight was observed between treatments.

This study has been carried out to investigate the effect of short-term divergent selection for 4-wk body weight on growth curve parameters and carcass components in Japanese quail. Quail lines utilized were two divergently selected for high (HW) and low (LW) 4-wk body weight (BW) as well as a line as control (C). The results of the study indicated that quails in HW line had heavier BW than those in LW and in C lines from 6 and 11-d thereafter respectively. Moreover there was a significant difference for growth rate between lines from 4-d of age. To investigate the changes in carcass components, quails were slaughtered at 32 and 42-d of age. Results indicated that quails in HW line had significantly heavier carcass, thigh, heart, lung, liver, small intestine and breast dimensions (length, depth & weight) than quails in LW line for both age groups (P<0.05). In comparison with C line, HW quail showed higher weights in carcass components. The results also indicated that the selected lines for higher or lower 4-wk body weights diverged from control immediately after being hatched. Therefore, this method of selection can affect, in short-terms, the growth pattern as well as carcass traits of the selected birds.

Forty-two weaned Lori-Bakhtiari lambs were taken in an investigation for the effects of two-nutritional management methods of restricted vs. re-alimentation feeding on intake, growth and as well on the cost benefit analysis. During the Feed Restriction Period (FRP), the Control (C) animals were fed low-quality roughage ad libitum, plus mixed concentrate. The restricted animals (R) were fed only low-quality roughage. In the Re-Alimentation Periods (RAPs), the lambs due for restricted treatment were divided into two groups of R1 and R2. They received low-quality roughage along with two different levels of concentrate supplement as mentioned before. During restriction period, the C group had a significantly higher (P<0.05) daily gain, daily Dry Matter Intake (DMI) and Matabolizable Energy Intake (MEI) than the restricted group, which maintained thier constant weight. In the RAP and at both concentrate levels, the compensating animals showed the same growth rate as the previous unrestricted ones. Compensating groups benefited from a better FCR than C animals (P<0.05), DMI (g kg-0.75 d-1) with their ADG being similar to C animals. During RAP total of net profit and net income per unit product were lower in C group than those in R1 and R2 (P<0.05), the lowest economic efficiency occurred for the case of C animals and the highest for the case of R2 group (P<0.01).

Economic data and performance records from 10 Iranian Holstein dairy cattle herds, as well as milk production and fertility records from Iranian Center of Animal Breeding and Animal Production Improvment were used to estimate the effect of calving difficulty on milk production, fertility and as well on the economic aspects of maternal and direct calving difficulty. Calving difficulty could be divided into 3 classes. Class 1: normal calving; Class 2: calving that needed help by one man worker, and Class 3: calving with serious damage to calf and mother. Milk production decreased about 46 kg and 323 kg in classes 2, and 3 of the calving difficulty incidences, respectively. Calving difficulty caused decreases in fertility performance by 0.22 more inseminations to be performed in class 2 and 0.35 more ones in class 3. Stillbirth was not affected as by class 2 but was intensified in class 3 by 5 percent. Total economic loss attributed to classes 2 and 3 of calving difficulties were $57.76 and $243.83, respectively. Estimated economic value for maternal and direct effect were $37 per unit change in liability per cow/year. Following a correction of the economic values by cumulative discounted expressions, the economic values for maternal and direct effects amounted to $22.79 for direct, and $8.54 for maternal difficulties.

A total of 20 suckling Sanjabi Lambs, comprised of 10 males and 10 females with respective liveweights of 13.40±1.34 and 11.62±0.85 kg were employed in a 2x2 factorial experimental arrangement. The lambs within their sexes were grouped according to their liveweights and then randomly allocated to either one of the two treatments namely: ad libitum good quality alfalfa hay plus free suckling (control); ad libitum creep mixture having 18% CP in addition to free suckling, and free choice good quality alfalfa hay (creep mixture). Daily feed intake along with liveweight changes in all the lambs were recorded throughout the study. Skin biopsies and fiber samples were taken every 15 and 28 days respectively. Average daily milk intake by the male lambs in creep mixture group was significantly (P<0.05) higher than that by the other groups. Average daily gain by lambs in creep mixture group, was significantly (P<0.05) higher than that by the lambs in control group. The factors sex and dietary treatment exerted no significant effects on either primary or secondary follicle densities, on the S/P ratio in the skin and either on the mean values of either primary or secondary follicular indexes.

The presence of nectar-and pollen- bearing plants as vegetative cover in rangelands can provide the ground for job opportunities in the context of beekeeping as an aspect of rangeland's multipurpose uses. Beekeeping, as an approach, based upon indigenous knowledge, is suggested to create jobs, and to somehow compensate for the animal husbandry's diminishing income (the fall of income due to the necessity of lowering the number of aniamls to ease the exerted pressure upon rangelands). Realizing the close relationship between bees and the flowering plants a study of the flowering plants (time of flowering in particular) appealing to honeybee, as well as an identification of the places where these plants grow more, are among the important tools of management towards a determination of a region's appropriateness as regards beekeeping. The end results are expected to be a prevention of rangeland degradation due to overgrazing, accompanied by the development of beekeeping job opportunities. A lack of knowledge in the field would, on the other hand, be a severe hindrance to proper exploitation of rangeland's beekeeping potential. In the course of the present study, the potentiality of the region concerning an identification and use of the region's plants in beekeeping enterprises has been put into consideration. Randomized sampling of plant types, cavere percentage, and plant combination percent was performed through a number of three 200 m2 transects along which a number of thirty plots (each of 1 m2 area) were assigned. In the study are a (Middle Taleghan), the most conspicuous plant families visited by bees were respectively Labiatae, Fabaceae, Asteraceae, Apiaceae, Rosaceae, and Crucifera. Seventy nine out of 175 plant species are visited and utilized by bees most. These species which form the dominant plant cover in poorer rangelands are lowly valued as viewed by animal keeper. A further knowledge of these plants along with particularly a close identification of their flowering days would lead to the preparation of a beekeeping calendar and an estimation of the rangeland's potential that can be dedicated to the enterprise.

An experiment was carried out to investigate the nutritive value of hay of Vicia sativa, Lathyrus sativus and Vicia ervilia cultivated in Ardabil province. Digestibility was estimated through in vitro method. Gas Production (GP) was recorded after 2, 4, 6, 8, 12, 24, 48, 72 and 96 h of incubation. Crude protein contents of the tested hay legumes were (14.99-19.05%), Crude Ash (11.70-13.54%), ADF (29.46-32.66%), Ca (1.111-0.827%), P (0.03-0.06%) and Dry Matter Digestibiliy (56.60-61.46%) respectively. The 24 hr gas production volume for heys of Vicia sativa, Lathyrus sativus and Vicia ervilia were 47.57, 4.14, 41.03 mL/200g DM, respectively with Vicia ervilia hey rendering the highest gas production volume (p<0.001) among the feedstuffs tested. In Vicia ervilia hey, potential gas production (52.23 mL), rate of gas production (0.133 mL h-1), Short Chain Fatty Acids (1.055 mmol), and metabolizable energy (9.66 MJ/kg) were significantly higher than those in Lathyrus sativus (48.29%, 0.104% h-1, 0.957 mmol and 8.97 MJ/kg), and those in Vicia sativa (44.88 mL, 0.106 mL h-1, 0.91 mmol and 8.64 MJ/kg). Considering the different chemical compositions of the tested hay, the values for the traits of: in vitro digestibility, gas production as well as metabolizable energy of feeds were also different and thus significantly and differently affected the degradation parameters.