مجله علوم دامی ایران
سال چهلم شماره 1 (بهار 1388)

The purpose of this study was to investigate the relationship of maternal breeding values of the weight of day-old chick chicks in a commercial broiler line with egg traits including yolk fatty acids. Maternal breeding values of 63 hens of known pedigree were estimated through an animal model, containing direct additive genetic effect, maternal additive genetic effect, maternal common environmental effect and covariance between direct and maternal additive genetic effects, through DFREML program employing 6476 records of day-old chick weights. Hens were divided into 3 genetic groups (low, LGG; medium, MGG; and high, HGG) on the basis of estimated maternal breeding values. From the hens, 126 eggs (2 eggs from each hen) were collected at 32 weeks of age for an assessment of egg quality and quantity traits (egg weight, shell thickness, shell strength, shell weight, yolk weight, yolk percentage, albumin weight and albumin percentage) as well as yolk fatty acids (palmetic, palmitoleic, estearic, oleic, linoleic and linolenic acids). Analysis of variance was carried out through GLM procedure and differences among the means evaluated using Tukey method. Egg, shell, yolk, and albumin weights as well as albumin percentage were higher (p<0.05) for HGG than for MGG and LGG. However, yolk percentage mean decreased as maternal breeding values increased. With the as fitting egg weight as a covariate, the differences among the means in the 3 genetic groups were not found as significant. The results indicated that egg weight accounts for a considerable part of variability of all traits. The MGG had the higher and the HGG a lower mean of yolk fatty acids, but the differences were not significant.

Data related to Holstein dairy cattle from 1987 to 2004 were obtained from Animal Breeding Center of Iran to estimate the genetic and phenotypic trends. Variance components and genetic parameters of the first lactation records were estimated using Restricted Maximum Likelihood Method and AIREML algorithm through MATVEC program. Animal breeding values were predicted through multiple-trait animal model. Estimates of heritability for milk, fat and protein yields were 0.27, 0.22 and 0.25, respectively. Genetic trend was estimated as the linear regression of BLUPs of the breeding values of animals on the birth year. The estimate of genetic trend for milk yield was 33.84±2.10kg, for fat yield 0.64±0.05kg and for protein yield it was 1.00±0.08kg. Average phenotypic trend for milk, fat and protein yields were 122.28, 4.42 and 3.06 kg, respectively. Acceptable genetic improvement for milk yield, while low genetic trends for fat and protein yield were observed in Holstein cattle in Iran.

To test the effect of culling herd life from the breeding goal function, 4 different selection indices were established as: index 1: using Milk production (Milk), Fat percentage of milk (fat%) and Rear Udder Height (Ruh); index 2: using Milk, fat% and Fore teat placement (Ftp), index 3: using Milk, fat% and Fore udder attachment (Fua); and index 4: using Milk, fat%, Ruh, Ftp and Fua) under two different selection goals, one of which included Milk, fat% and herd life while the other one was excluded of herd life. Calculations were made in economic situations of year 1995 and 2000. Response to selection and selection accuracy resulted from the above mentioned indices and under two economic situations revealed that exclusion of herd life would result in a decrease in genetic gain in the breeding goal function except when excluded from index 4 and under 1995 conditions, although by excluding this trait the selection accuracy may even increase.

Three hundred and sixty broiler chicks (Ross 308) were employed in an experiment from 6 to 49 days of age to evaluate the effect of replacing canola meal for soybean meal either with or without enzyme supplementation. Dietary treatments included 5 substitution levels (0, 25, 50, 75 and 100%) at two enzyme concentrations of: 0 and 400 g/ton in a 5×2 factorial layout experiment. The enzyme mixture contained mainly? -glucanase activity and to some extent xylanase activity. Data were analyzed in a completely randomized design. Body weight gain during 6 to 21d was significantly (P<0.05) reduced by raising of canola meal substitution level and while enzyme addition successfully restoring the situation so that main effect of enzyme addition was observed as significant (P<0.05). However, body weight gain during 6 to 49d was not affected by treatments (P>0.05). The effect of substitution level was significant with respect to feed intake during the starting (6-21d) and growing (21-42d) periods whereas it was not significant during the finishing (42-49d) period and the entire the experiment (6-49d). Feed conversion ratio was significantly (P<0.05) influenced by substitution level in all the feeding periods. Main effects and interaction of treatments were not found significant for carcass traits and plasma thyroid hormone concentrations. Feed cost per unit of gain was linearly reduced by increasing the proportion of Canola Meal (CM) at the cost of SBM in the diet. Enzyme addition did not significantly affect feed cost per unit of gain. The optimal substitution level in terms of feed cost per unit of gain was 100%.

This study was conducted to evaluate production response of early lactating cows to rumen protected fats. Twelve (nine multiparous and three primiparous) Holstein cows (26±4 d in milk) were empolyed in a replicated 3×3 Latin Square Design of 21-d periods. Each period consisted of 14 days of adaptation and 7 days of sampling. Cows received diets containing either one of two types of protected fats or no supplemental fat. Cows in group 1 (control) were fed Total Mixed Ration (TMR) of 20% corn silage, 20% alfalfa hay, and 60% concentrate mix. Cows in group 2 were fed the TMR containing 3% prilled protected fat (Energizer-10). Cows in group 3 were fed the TMR containing 3.5% Ca salt of protected fat (Magnapac). Intake of Dry Matter (DM), Organic Matter (OM) and Neutral Detergent Fiber (NDF) were decreased by rumen protected fat (P < 0.05) in multiparous cows (DMI: 25.7, 24.1, and 23.9 kg/d for control, prilled fat, and ca salt of fat, respectively); intake of NEL in all the cow population and intake of DM, OM and NDF in primiparous cows were similar for all diets (P > 0.05). Production of milk and 3.5% FCM in primiparous and multiparous cows as well as milk protein, fat, lactose and total solid percentages and yields (kg/d) were not affected by fat supplements (P > 0.05). The BCS and BW changes were similar for all diets in multiparous and primiparous cows (P > 0.05). In multiparous cows, feed efficiency (3.5% FCM/DMI) was higher for cows fed supplemental fat diets (P < 0.05) than for control samples. Fat fed cows were more efficient than those fed with control diet. In primiparous cows supplemental fat did not influence feed efficiency (P > 0.05). Fat supplements did not influence either chewing behavior or total time spent ruminating and eating (P > 0.05). The results indicate that supplementation of early lactating diet with rumen protected fat decreases feed intake and improves milk efficiency but this is not true for primiparous cows.

The objective of this study was to determine the best time for artificial insemination in Taleshi ewes. One hundred and fifty ewes were randomly allotted to three groups (n=50/per group). Estrus was synchronized with intravaginal insertion of Controlled Internal Drug Release (CIDR) for 14 days. At the time of CIDR removal PMSG (300IU) was injected to the ewes. The first (AI28), second (AI40) and third (AI52) groups were inseminated (cervically) 28, 40 and 52 hours after CIDR removal, respectively. All ewes showed estrus singns about 24 hours after CIDR withdrawal. The results of insemination efficiency and reproduction performance indicated that in prolificacy and twin bearing traits there did not exist any statistical difference among the groups. Insemination efficiency, lambing rate and fertility made significant differences among the groups (P<0.05). Insemination efficiency in AI40 and AI52 amounted to 50% and 38% respectively, which was significantly different (P<0.05) from AI28 (18%) treatment. Lambing rates in AI40 and AI52 were 58% and 38% respectively, statistically different (P<0.05) from AI28 treatment. The results of the research indicated that the most appropriate time for Taleshi ewes insemination was between 40-52 hours after CIDR removal.

In this study the data of 2332 lambs from 815 dams and 61 sires, collected during 1993-2004 in Kermani sheep breeding station were used to estimate phenotypic, genetic and environmental trends for birth weight (BW), weaning weight (WW), 6 months weight (6MW), 9 months weight (9MW) and yearling weight (YW). Heritability estimates were determined for each trait using derivative free REML procedures under univariate animal model. By excluding or including maternal genetic effects or maternal permanent environmental effects, six different models were fitted for each trait. Likelihood ratio test was used to determine the appropriate model. This test indicated that the model including direct and maternal genetic effects, without covariance between them, was the appropriate model for BW. The model including direct genetic effects and maternal permanent environmental effects was the most appropriate model for WW, 6MW and 9MW. The model including direct genetic effects was the most appropriate model for YW. Phenotypic, genetic and environmental correlations were estimated under multivariate analysis using the most appropriate model for each trait. Breeding values were estimated under univarite and multivariate analyses. Genetic, phenotypic and environmental trends were estimated by regression of the estimated mean of breeding values, phenotypic mean and difference between estimated mean of breeding values and phenotypic mean on birth year, respectively. The average additive direct genetic trends for BW, WW, 6MW, 9MW, YW in univariate and multivariate analyses were 0.53±0.30 and 0.84±1.14, 96.41±18.27 and 101.29±37.41, 88.24±26.11 and 90.51±48.34, 24.35±10.68 and 29.76±11.49 and 31.53±10.43 and 35.18±12.58 gr per year, respectively. The estimates of maternal additive genetic trend for BW in univariate and multivariate analyses were 3.07±1.21 and 2.91±1.67 gr per year, respectively.

The effect of crossbreeding between Ghezel and Mehraban on growth performance and carcass characteristics was studied for two consecutive years using 162 purebred and crossbred lambs. The four groups of lambs involved in the study were purebred Mehraban (MM), purebred Ghezel (GG), crossbred Ghezel ram×Mehraban ewe (GM) and crossbred Mehraban ram×Ghezel ewe (MG). The lambs were fed with grazing of cereal (wheat and barely) pasture, alfalfa as well as with concentrate for 84 days. The results indicated that crossbreeding had significant (p<0.01) effect on average daily gain, chilled dressing percentage and some carcass cuts. Least square means comparisons showed that average daily gain was highest for GM (256.5 g/day) while the lowest for MM (222.0 g/day) lambs. There were no significant differences among among groups for fat-tail weight, and fat-tail percentage. Total dissected internal fat (renal, cardiac, intestine and cavity) was lowest for MM as compared with other groups, but there were no significant differences when total dissected fat corrected for carcass weight. Breed (p<0.05) and initial weight of lambs (p<0.01) had significant effect on leg weight. No significant differences were observed among genotypes for leg percentage, shoulder weight and percentage. The effect of genotype was significant on eye muscle area with purebred Mehraban and MG lambs ranking the lowest and the highest, respectively. There were no significant differences observed for dry matter, crude protein and ether extracts of carcass among groups. The interaction of genotype×year was not significant for any of the traits.

Sixty eight Holstein cows, 38 primiparous and 30 multiparous ones, were employed in a randomized complete block design, blocked to evaluate the effects of 2 diets in various ruminal fermentable carbohydrate sources (Ground Corn vs Rolled Wheat) on rumen fermentation and performance during preparturient period. Primiparous and multiparous cows were blocked by parity. The cows were fed diets as total mixed ration with similar energy and crude protein content including 1) 18.57% GC; 2) 18.57% RW from -23.1 ± 9 d relative to expected calving until calving. Followeing calving, all the animals received the same lactation diet for 28 days. The results revealed that, dry matter intake, energy intake, energy balance, and body condition score did not differ between multiparous cows fed either the ground corn or rolled wheat diet at preparturient period. Dry matter intake, energy intake, and energy balance were lower for primiparous cows fed the rolled wheat diet at prepartum period (p<0.05) with no differences observed after calving. Higher ruminal propionate was produced through feeding the rolled wheat diet to multiparous cows at prepartum. Acetate to propionate ratio was also lower for these cows (p<0.05). There were no significant differences observed between multiparous cows for milk yield and its components with the exception of milk urea nitrogen. Primiparous cows fed with the rolled wheat diet had a greater milk protein content and yield (p<0.05) relative to cows fed the ground corn diet. Milk urea nitrogen was lower for multiparous and primiparous cows fed the rolled wheat diet (p<0.05). In total, it can be concluded that, feeding prepartum diets containing rapidly fermentable sources of starch (rolled wheat) can improve ruminal fermentation, performance as well as adaptation from gestation to lactation in prepartum Holstein cows.

The present study was carried out to investigate the effect of corn replacement by different levels of wheat with supplementation of phytase with reduced phosphorus level for laying hens. Two hundred seventy nine layer hens (the strains of Hy-line W36) at the 53th week of age, selected based on the same egg production percentage and body weight, assigned in a factorial arrangement with completely randomized design of 30 treatments each in 3 replicates. The factors included 5 levels of replacements (0, 25, 50, 75, 100% replacement of corn by wheat), phytase enzyme in three levels (0, 500, 1000 ftu/kg) and two levels of non phytate phosphorus (0.70% and 0.55% requirement) along with one corn soybean meal control diet. The experiment was carried out at 3 periods, each of 28 days. Egg production percentage, egg weight, feed conversion ratio, shell percentage, shell strength, shell thickness and toe ash were assessed. The results indicated that the effects of substitution wheat on egg production, Feed Conversion Ratio (FCR), shell strength, shell thickness and toe ash were significant (P<0.05), with on increase of wheat in the diet, egg production, and toe ash being improved. FCR in the 75% substitution of wheat treatment was decreased while in the 100% substitution it was increased. Eggshell percentage wasnt affected by substitution of wheat. Effect of enzyme on egg production percentage, egg weight, FCR, shell strength, shell thickness and toe ash was significant (P<0.01). The effect of non phytate phosphorus level on egg production was significant (P<0.05). Egg weight, FCR, shell percentage, shell thickness and toe ash werent affected by non phytate phosphorus level. Results suggested that a deficiency of non-phytate phosphorus isn’t problematic and a utilization of 50% corn substitution with wheat along with supplemental 500ftu/kg phytase would improve the performance and therefore, corn cab be replaced by wheat to a level of 75%.