JOURNAL OF LIVESTOCK SCIENCE AND TECHNOLOGIES
Year:2017 | Volume:5 | Issue:1|Papers Count:8

This study was carried out in a commercial herd from 2008 to 2012 in order to determine the most prevalent reasons for culling Holstein cows and to assess the effects of risk factors. Overall, 519 (28.2%) cows were culled for involuntary (98.8%) and voluntary (1.2%) reasons. The involuntary causes of culling were diseases (38.7%), reproduction problems (36.0%), udder disorders (7.7%), lameness (3.7%) and death (12.7%). Mean age of cows at culling was 70.5±15.6 months and the time interval from last calving to culling averaged 263±196 days. Logistic binary regression was used to model the hazard of culling. The analysis of risk factors showed that parity, calving season, and age at first calving had significant effects on the hazard of culling (P<0.05 to P<0.001). Thus, cows at parity 3 and 4 or greater had a 116.5% and 253.8% risk of culling, respectively than cows at parity 1 (reference class) (P<0.001). Cows that calved from May to August and from September to December had a 19.7% and 45.5% risk of culling, respectively, higher than those that calved from January to April. The risk of culling increased with increasing age at first calving. Thus, cows having an age at first calving of 25-30 and 31-38 months had a 130.8% and 90.4% risk of culling, respectively, higher than cows having an age at first calving less or equal than 24 months. It was concluded that identifying reasons for culling can be helpful in determining management problems in dairy herds.

Data from 183 animals raised in 61 flocks were collected to investigate the morphological characteristics of the Northern Morocco goat. Nine zoometric measures and seven combined indices were obtained. Three zones were defined based on geo-climatic characteristics and environ-mental influences: Mediterranean, Atlantic and Dual. The morphological variables showed the absence of sexual dimorphism in the northern Morocco goat population. Measures were generally very similar (n.s. at p<0.05) for male and female, except shin girth was high in males compared with females. A few variables including height at withers, ear length, rump length, length led and ears index were significantly (p<0.05) influenced by geographical area. Mahalanobis distances and Canonical analyses showed a greater distance between the most geographical separated subpopulations (Atlantic and Dual) and animals from these areas were the most heterogeneous. The stepwise procedure showed that length led, ear length, rump length and shin girth were the most discriminate variables between areas. Results suggest that the goat population of north Morocco, exhibiting different morphological variables by location, maybe due to the environmental adaptation or the differences in origin and recent influences by introgression or crossbreeding.

An experiment was conducted to study the effect of substitution of soybean meal (SBM) with canola meal (CM) in diets formulated on the basis of total or digestible amino acid (AA) on productive performance, egg quality, and selected organ weight and blood parameters in laying hens from 73rd to 83rd weeks of age. A total of 128 laying hens were allotted randomly to a completely randomized design arranged as a 2×2 factorial experiment with two protein sources (soybean meal and 30% soybean replaced by canola meal), and two diets formulated for total or digestible amino acids. Four experimental diets were formulated with four replicates of eight birds each. Increased egg weight, egg mass and improved feed conversion ratio (FCR) were recorded for diets containing SBM compared with CM (P<0.05). Egg weight was increased (P<0.05) by SBM formulated on digestible amino acid compared to other dietary treatments. Increased shell thickness (P<0.05) was recorded for CM when the diet was formulated on total amino acid basis. Yolk color and relative weight (RW) of the liver were increased (P<0.05) by canola meal diet formulated on digestible amino acid. Blood parameters were not affected (P>0.05) by treatments. The results of this study showed that soybean meal caused better performance than canola meal, and feed formulation based on digestible AA in SBM diet resulted in better performance in laying hens.

There are many studies on the effects of probiotics on performance of broiler chickens, but none of them has evaluated the metabolizable energy (ME) equivalency values of probiotics. The aim of this study was to determine the metabolizable energy equivalency value of Bacillus subtilis spore and its potential for decreasing feed ME content and cost. One hundred seventy-six day-old male broilers (Ross 308) were used in a completely randomized design, with 11 treatments, of four replicates each, and 4 chickens per cage as an experimental unit. Dietary treatments contain a basal diet (2800 kcal/kg) containing graded levels of ME (2850, 2900, 2950, 3000 and 3050 kcal/kg) and Bacillus subtilis (4 × 109 CFU/g DSM 17299) at 0.05, 0.10, 0.15, 0.20 and 0.25 g/kg. Graded levels of feed ME and added Bacillus subtilis were used as independent variables to derive regression equa-tion of performance traits on independent variables. The derived regression equations of body weight and feed conversion ratio (FCR) for ME were set to be equal with those obtained for Bacillus subtilis and were solved; Bacillus subtilis equivalence value for ME was calculated by subtracting the ob-tained value from ME content of the basal diet. In comparison to the basal diet, added Bacillus subtilis significantly improved the body weight and feed conversion ratio. Metabolizable energy equivalency of Bacillus subtilis for FCR and body weight at 42 days of age was 360366 and 485823 kcal/kg, respectively. Results showed that ME value of Bacillus subtilis was decreased by advancing chickens age.

Starch (SS) and fermented fiber (FFS), as energy sources were included in Holstein bull calf diets to evaluate their growth performance, rumen fermentation pattern and concentration of insulin and selected blood metabolites. Fourteen Holstein bull calves (BW=94.5±2.1 kg; age 87±9 d) were allocated to treatments (n=7 calves per treatment) and the study lasted 10 weeks. The diets were based on barley grain and corn silage in SS and FFS treatments, respectively. Dry matter intake was decreased (P<0.05) in SS compared to FFS treatment (7.83 vs.8.21 kg/d), with SS treatment causing a lower feed conversion ratio (FCR). Growth indices (body length, withers height and heart girth) did not differ between two treatments (P>0.05). Fecal score was more watery (=3.1) in SS compared to FFS (=2.4) treatment (P<0.05). The SS diet increased propionate concentration but FFS increased acetate concentration in the rumen fluid. Blood glucose was increased, but beta-hy-droxybutyrate (BHB) decreased in SS fed calves. Insulin concentration was greater by 2.1 mIU ml-1 in SS compared to FFS fed calves. Results showed that although the high starch diet decreased the feed intake and caused feces to contain more water, it improved energy status of the calves via de-creasing BHB, increasing propionate concentration and improving glucose concentrations. The SS-based diet showed greater efficiency compared to FFS in bull calves.

Pedigree information collected from 1979 to 2012 were used to study the genetic variability and population structure of Raeini Cashmere goats, taking kids born from 2009 to 2012 into account as the reference population. The mean inbreeding coefficients in the whole and inbred populations were computed to be 0.04% and 4.41%, respectively. Considering the reference population, the average inbreeding coefficient and average relatedness were 0.14 % and 0.11%, respectively. The mean of generation interval, computed from four gametic pathways (sire-son, sire-daughter, dam-son and dam-daughter), was 3.72 years, with a longer interval from dam-progeny pathways relative to sire-progeny ones. In the reference population, the average equivalent complete generation, as a measure of pedigree completeness, was 1.25. The effective population sizes estimated from the individual rate in coancestry and from the individual increase in inbreeding were 332 and 229, respec-tively. The effective numbers of founders (fe) and the effective numbers of ancestors (fa) were estimated at 240 and 137, respectively. Approximately, 50% of the total genetic variations were explained by the first 57 influential ancestors, with a maximum individual contribution of 3.94%. The ratio of fe to fa, as measure of bottleneck, was 1.75. The results revealed the evidences for occurrence of bottlenecks in the population, mainly because of unbalanced contribution of breeding animals to the gene pool of the studied population of Raeini Cashmere goat.

Rayeni Cashmere goat is one of the most important goat breeds in Iran, nevertheless, the production rate and consequently the financial income are not satisfactory at the moment. This necessitates to investigate various features of the production chain, such as costs and revenues of the system. Hence, in this study a deterministic bio-economic model was used to estimate the economic values for reproductive traits (conception rate, twining rate and litter size), production traits (body weight of kid sold at 6.5 months, annual cashmere weight, doe body weight and annual milk yield) and longevity (doe survival, survival of kid until weaning and survival of kid until sale age at 6.5 months), using data on 10 Rayeni Cashmere goat flocks including 1810 does and 95 bucks in Kerman province, south-east of Iran. Sensitivity analysis of economic values to price levels of input and out-put was also carried out. Revenue sources of production system included: live weight, milk and cash-mere production, while live weight was the most important one and included 62.37% of the total revenues. Total profit was US $ 126.2 per doe per year. The most important trait was annual milk yield followed by the litter size with the relative importance of 0.99 and 0.016, respectively. The least economically important trait was the doe body weight (-0.040). In this system, all economic values were positive except that for the doe body weight. Changes in prices of input and output had a small effect on economic values.

This study was conducted to estimate the genetic parameters of litter size (LS) in Moghani sheep using threshold model via Bayesian approach. The data originated from the Jafar-Abad Station of Ardabil province, Iran, and included 9698 lactation records of 4977 ewes with lamb-ings from 1995 until 2010. The pedigree file consisted of data on animals born from 1987 to 2010. The significance of fixed effects was examined using the Logistic procedure. Six different animal models were fitted by considering direct genetic effect, including and excluding maternal effect (with and without covariance between maternal and direct genetic effects) as well as permanent environ-mental effect via Bayesian approach. The genetic parameters were estimated using the THRGIBBS1F90 program. The most appropriate model for LS was determined based on the Deviance Information Criterion (DIC). Based on the obtained results, the second model that included the direct genetic and permanent environmental effects of the ewe was chosen as the best model. Using the second model, the estimates of direct heritability, permanent environmental effect of the ewe and repeatability were 0.041, 0.027 and 0.068, respectively. The low estimates of genetic parameters obtained in the current study for LS in Moghani sheep indicated that selection based on the ewe’s own performance may result in slow genetic improvement.