مجله پژوهش در نشخوار کنندگان
سال دوم شماره 3 (پاییز 1393)

In order to determine optimum level of crude protein and degradable and undegradable protein in high producing dairy cow two separate experiment were conducted. In the first experiment, 12 lactating Holstein cows in the second parities were used in 4×4 Latin square design that included 4 treatments. In the second nine lactating cows were used 3×3 Latin square design that included 3 treatments. Treatments 1 to 4 in the first experiment consisted of diet containing 18, 17.2, 16.4, and 15.6 percent crude protein, respectively. Degradable protein level in all diets was same about 10.9 % of DM, while rumen undegradable protein level was gradually decreased. Treatments 1 to 3 in the second experiment consisted of diet containing 16.4, 15.6, and 14.8 percent crude protein, respectively. Rumen undegradable protein levels were constant across the treatments (5.6 % DM) while rumen degradable protein was gradually decreased. In the first experiment the diets had no significant effect on milk production and composition. Dry matter intake and FCM in third treatment was significantly higher than the other groups (P<0.05). Apparent digestibility of dietary protein in the first treatment was more than other groups (P<0.05). In the second experiment milk urea nitrogen due to decrease rumen degradable protein significantly decreased (P<0.05). The result of first experiment showed that reduction in the level of crude protein and undegradable protein until 15.6 and 4.7 % didn’t had negative effect on producing performance and milk composition, also the result of second experiment showed nonentity of negative effect of reduce in crude protein and degradable protein until 14.8 and 9.3 % on producing performance and milk composition of dairy cows. Moreover results of two the experiments showed that NRC predication of crude protein, rumen degradable and undegradable protein requirement is more than actual requirement of dairy cows.

Thirty Holstein male calves with an initial Body Weight of 308±22 Kg and age approximately 10 month were used for 100 days in a complete randomized design with 3 treatments (rations) and 10 replicates in each treatment. Rations were: 1) Control (with rolled barley treated with water), 2) rolled barley treated with 1% citric acid, and 3) rolled barley treated with 0.5% lactic acid. All of data were analyzed with SAS software using PROC GLM and PROC MIXED. The performance traits, total tract digestibility, blood parameters and fecal pH were determined. Final body weight, average daily gains and feed intake to gain ratio of calves were affected significantly (P<0.05). Dry matter intakes were not different among treatments. Total tract digestibility of DM, OM, CP and NDF were affected significantly (P<0.05). Also, fecal pH was not different between treatments. Barley treated with organic acid increased plasma glucose and decreased plasma cholesterol of calves. While the amount of plasma urea, triglyceride, total protein and albumin of calves were not significantly different among treatments. It is concluded that treating rolled barley grain with lactic and citric acid could improve feedlot performance and digestibility of nutrients in Holstein male calves.

This experiment was conducted to study the effect of diet containing high non fibrous carbohydrates on production performance, neutrophil response and inducing inflammation, in Jersey lactating cows. Seven multiparous (2.5±0.5) cows in 71±3 days in milk and average milk production 28±6.6 kg were used. All cows received the low non fibrous carbohydrates (34.3 percentage of dry matter) diet for 14 days and then were switched to an isonitrogenous / isocaloric high non fibrous carbohydrates (40.7 percentage of dry matter) diet for one week. Dry matter intake and milk production was measured for each animal. Dry matter intake was significantly reduced (P<0.05). Milk production was not affected by the diet. Neutrophil performance was determined by measuring three inflammatory markers phagocytosis, oxidative burst and L-selectin protein expression on neutrophils. L-selectin protein expression on neutrophils was significantly increased and phagocytosis was significantly reduced by feeding the high non fibrous carbohydrates diet (P<0.05). Oxidative burst was not influenced by the diet. Plasma haptoglobin, zinc and tumor necrosis factor-α as inflammatory markers were measured. High non fibrous carbohydrates diet increased the plasma haptoglobin (P<0.05) significantly decreased zinc and tumor necrosis factor-α was not different (P>0.10). Taken together, these data indicate that switching from a lower non fibrous carbohydrates diet to an isoenergetic high non fibrous carbohydrates diet caused mild inflammation in lactating Jersey cows which evidenced by the decreasing dry matter intake, zinc, phagocytosis and the greater plasma concentrations of the acute phase protein, haptoglobin and L-selectin protein expression on neutrophils.

This trial was conducted to evaluate the effects of different sources of selenium supplements on growth performance, hematological and rumen metabolites in finishing Mehraban lambs for 70 days. The trial experiment consisted of 24 male lambs, 4-5 months of age and 35.8±2.7 kg average in weight randomly allotted to 4 treatments. Treatments were: 1) Control diet (diet without selenium supplementation, containing 0.06 mg/kg of selenium); 2) Control diet + 0.2 mg/kg Se as selenium yeast (organic selenium); 3) Control diet + 0.2 mg/kg Se as sodium selenite and 4) Control diet + 0.4 mg/kg Se as sodium selenite. During the course of the experiment lambs were weighed on first day and on days 14, 28, 42, 56 and 70 to determine body weight change. Blood samples were taken on days 0, 35 and 70 and rumen samples were taken on days 35 and 70. Feed was administered daily and orts recorded to get net feed intak. Supplementations of organic and inorganic selenium to diet did not have significant effect on lambs growth performance, hematological parameters, alkaline phosphatase, aspartate aminotransferase and creatine phospho kinase (P<0.05), while increased blood GPX activity compared to control group (P<0.05). Also, supplementation of 0.2 mg/kg organic selenium increased total volatile fatty acids and decreased ammonia concentrations in rumen, compared with non supplemented group (P<0.05). In overall, it may be concluded that organic supplement of selenium improves rumen parameters of growing Mehraban lambs.1

Because of milk fat importance of providing some special fatty acids in human nutrition, there is increasing attention to the milk fatty acid profile designing. For studying the effect of feeding fish oil and palm oil on milk fatty acid profile, ten multiparous Holstein cows, based on their expected parturition dates, from six weeks before up to 63 days after calving, randomly received palm oil or fish oil. Milk production was measured daily and milk compositions were determined weekly. The milk fatty acid profile was determined by gas-chromatography. Fish oil supplement decreased saturated fatty acid content in milk fat (P<0.05) and increased its polyunsaturated fatty acid content (P<0.05), but had no effect on monounsaturated fatty acid content in milk fat (P>0.05). Milk fat omega-6 to omega-3 fatty acid ratio, decreased (P<0.05) and health index increased (P<0.05) with inclusion of fish oil in the diet. Likewise, milk fat to protein ratio and monounsaturated to polyunsaturated fatty acid ratio, which has been linked to negative energy balance, were decreased with feeding fish oil (P<0.05). These results suggest, that the supplementation of dairy cows diet with fish oil from dry period, could improve the milk fatty acid profile to human health and also alleviate the intensity of negative energy balance in early lactation.

The present study was conducted on Kurdi ewes of Hossein Abad Sheep Breeding Station of Shirvan. In order to estimate genetic parameters, 1065 test day records of milk protein percentage from 245 ewes were collected. Data collection was started from April 2012 up to the end of lactation period. For genetic analysis of data, test day models with random regression coefficient were utilized. In random regression model, parity, litter size, month of recording as fixed effects and age at recording and days in milk as covariates were included. Random regression test day model was carried out using WOMBAT software. Genetic and environmental (co)variance components of milk protein percentage were estimated using restricted maximum likelihood. Orthogonal Legendre polynomials with different orders were applied for taking into account of genetic and permanent environmental effects. Legendre polynomial with the order of 2 was the best fitting model.In this research, the average milk protein percentage in Kurdi ewes was 6.69±0.70. The lowest and highest additive genetic variances were at the beginning) 0.058) and the end (0.114) of lactation, respectively. Phenotypic and permanent environmental variances were high at the beginning and at the end of lactation. Estimates of heritability increased over the lactation. Minimum and maximum heritabilities were estimated at the beginning (0.096) and end (0.178) of lactation, respectively. The higher the distance between days of lactation, the less were the genetic and permanent environmental correlations. Generally, results indicated that Shirvan Kordi ewes had high milk protein production potential. Moreover, higher heritability for this trait at the end of lactation probably indicated higher contribution of additive genetic variation to the total variation and selection of ewes in this part of lactation would be preferred.

The aims of this study were estimation of inbreeding coefficients and its effects on birth weight (BW), weaning weight (WW), 6 month weight (6MW), 9 month weight (9MW) and yearling weight (YW) of Zandi sheep. The pedigree data and records were of 6140 Zandi sheep, which were collected during 1991-2011 by Zandi sheep Breeding Center located in Tehran. 36.32 % of the animals were inbred. Mean inbreeding coefficient for the herd and inbred population was 1.22 and 3.61 percent, respectively. Inbreeding coefficient was increased by 0.02±0.01 percent per year (P<0.05). Effects of inbreeding on traits were estimated by restricted maximum likelihood method using 12 animal models. The most appropriate model for each trait was determined based on Akaike’s Information Criterion. The regression coefficients of inbreeding on BW, WW, 6MW, 9MW and YW were -3.49±4.87 (P>0.05), -42.20±20.18 (P<0.05), -60.35±25.12 (P<0.05), -40.70±24.80 (P>0.05) and -76.55±29.24 gr (P<0.01), respectively.

The effects of mating system, selection intensity and embryo transfer on inbreeding in dairy cattle were studied using stochastic simulation. Two mating systems (random and minimum consistory), two levels of selection intensity (high and low) for four selection paths (young bull, active sire, sire of dam, dam of dam) with or without embryo transfer for bull dams were combined together to make eight scenarios. 5000 cows distributed among 50 herds of size 100 and recorded for 6 traits (milk, fat, and protein production, age at first calving, calving interval, and somatic cell score) for 30 years were simulated. The results showed that minimum coancestry mating and low selection intensity had 60.43 % and 57 % annual changes of inbreeding lower than random mating and high selection intensity, respectively. Annual changes of inbreeding were 21.98 % higher when embryo transfer was used compared with not using it. Minimum and maximum annual change of inbreeding was estimated for eighth scenario (minimum consistory mating- low selection intensity- using embryo transfer) and third scenario (random mating- high selection intensity- no embryo transfer), respectively. The results suggest that high intensity of selection with minimum coancestry mating and embryo transfer can lead to genetic gain with minimum increase in inbreeding.

The main objective of the present research was to phenotypically study energy-corrected test day milk of first-parity dairy cows. A total of 774,013 test day records on 88,456 first-parity cows (three times milking a day) calved during 1997-2009 in 165 herds (six provinces) was used. Phenotypic analysis of the records was carried out by a linear mixed model in which fixed effects of province, herd within province, calving year, production month, cow genotype (grade or pure), sperm type, production age, within genotype, and random effect of sire were included. In order to take account of the shape of the lactation curve, polynomial function proposed by Ali and Schaeffer was used. Effects of province, calving year, production month, sperm type, and cow genotype on energy-corrected test day milk records were significant. There was a positive and significant annual phenotypic trend (0.434 Kgy-1) for the trait. Regression coefficients of energy-corrected test day milk on age at recording were significantly different between grade and pure cows. The two-way interactions were found to be significant, indicating that their inclusion in the test day models could increase precision and accuracy of genetic evaluation.

In order to estimate genetic parameters of body weight trait using random regression model 19388 test day records from 6013 Moghani sheep which were collected at Moghan Research Station located in Ardebil province, Iran, during 1995 to 2009 were used. In the model, year-season, birth year-season, sex of lamb, birth type and dam parity were classified as fixed effects and age of dam at parturition and age of animal were as covariates. Random effects of model were direct additive genetic effect, maternal additive genetic effect, direct permanent environmental effect and residual effect. Model 9 with 2nd order of fit for genetic effects and 4th order of fit for permanent environmental effect and 21 parameters was considered as the most appropriate model. Direct heritability estimated for weight at birth, 90, 180, 270 and 360 days were 0.069, 0.002, 0.005, 0.013 and 0.021, respectively. Results showed that direct heritability reduced after birth and reached to the lowest amount at 90 days of age, but after that increased as the age increased. Maternal heritability had considerable reduction after birth and then increased to 360 days. Weights at 270 and 360 days had the highest correlation. Commonly genetic and phenotypic correlations reduced as the age increased.