Journal of Livestock Science and Technology
Volume:1 Issue: 1, Apr 2013

Two forage species alfalfa (Medicago sativa), and sainfoin (Onobrychis viciifolia Scop.), at two consecutive growing season (spring and summer), were studied for their chemical composition and in vitro gas production characteristics. Data on cumulative gas production (mL gas/g DM) were fitted to the non-sigmoidal model, and for evaluation of model, the concordance correlation coefficient (CCC) was used to assess the agreement between predicted and observed data. Chemical analysis showed that nutrient composition was affected by the forage type. Concentration of fiber components (NDF, ADF, cellulose and crude fiber) were higher in alfalfa compared to sainfoin (P 0.05). The results showed that there is a great potential for improving the analytical capacity of the technique, by reducing the length of incubation from 48 to 24 h for studies on high quality forages. This study showed that 24 h incubation provided informative results with high reproducibility of the measurements, clear relationship and high correlations between different parameters and the relative feed value (RFV), and also reliable models for prediction of metabolizable energy with high values for the coefficients of determination. The results indicated that the logistic model can be used to describe the in vitro gas production kinetics (CCC = 0.992). It was concluded that, in addition to chemical analysis, the in vitro gas production is a useful and simple technique for determination of the relative feeding value of these forage species.

Current ruminant feeding systems depend on knowledge of the composition of feeds and the rate and extent of degradation of feed organic matter (OM) and crude protein (CP) in the rumen. The effect of storage and preparation of samples on in vitro gas production and fermentation characteristics of two common forage species, namely alfalfa and ryegrass werestudied. Samples were prepared as fresh (F), frozen-thawed (FT) and FT starch (FT) before in vitro evaluation. The fractional rate of loss of organic matter (OM) and the total N and total VFA production during 12h of incubation weresignificantly faster for alfalfa than for ryegrass. Model parameters describing changes in OM loss and total N appearance differed significantly between F samples and FT and FT samples; there was a significant interaction between forage species and preparation method for fractional degradation rate of total N. A significant interaction between forage species and preparation method at 6h incubation changed the rankings. The propionate:acetate ratios after 12h incubation were similar for alfalfa and ryegrass but were lower for F and FT samples than for FT samples. After 12h of incubation, alfalfa produced more gas, total VFA (mmol/g OM) and microbial crude protein (mg/g OM) than ryegrass, whereas F samples produced more fermentation products than FT and FT samples. In vitro degradation characteristics of forage samples were influenced by forage species, but also by sample preparation method; therefore, consistent use of one sample preparation method is recommended when comparing degradation characteristics of forage species in vitro.

Effects of partial docking on feedlot performance and body fat characteristics were studied in a fat-tailed sheep breed. Thirty-eight male lambs with an average weight of 4.44 ± 0.48 were randomly divided into two groups. The lambs in one group were partially docked at 3-4 h after birth, using rubber rings, and the lambs in another group remained intact (control). After weaning, 20 male lambs from each group were divided into two subgroups; one subgroup was fed with a normal dietary energy level (2.45 Mcal/kg ME) and the other subgroup received a high-energy diet (2.73 Mcal/kg ME) for 84 days. The lambs were fed individually. At the end of the fattening period, the lambs were slaughtered for determination of carcass characteristics. Warm carcass weight (WCW) and fat depth at the12th rib was recorded. At 24 h postmortem, samples of omental fat (for chemical analysis), and caudal fat were taken from chilled (4°C) carcasses for the determination of fatty acid (FA) composition. No significant difference was observed for the weight gain between docked and control lambs during the suckling period. During the fattening period, docked lambs as well as lambs on high level of energy diet showed better weight gain (P 0.05) was observed for WCW and fat depth at the 12th rib between docked and control lambs, but WCW was significantly affected by the diet energy density (P

The aim of this study was to evaluate total iodine, triiodothyronine (T3) and thyroxine (T4) status in the blood serum of Holstein cows on six farms in central Iran. Total iodine, T3 and T4 concentrations were measured in 90 blood serum samples (15 per farm). Mean concentrations of total iodine (38.80 ± 1.52 µg/l) and T3 (1.57 ± 0.10 nmol/l) were lower but the mean concentration of T4 (45.60 ± 1.53 nmol/l) was greater than the critical levels (P

The growth hormone receptor (GHR) is a member of cytokine/hematopoietin family that mediates the biological actions of growth hormone (GH) on target tissues. Therefore, the purpose of this study was to examine the association of TG-repeat polymorphisms in the 5’-flanking region of bovine GHR gene with milk production traits and somatic cell score (SCS) in Holstein cattle of Iran. The part of 5’-flanking region of GHR gene that encompassed TG-repeat was screened by single strand conformation polymorphism (SSCP) method and DNA sequencing. Five hundred eighteen Iranian Holstein cows were genotyped, giving 3 distinct SSCP patterns (A, B, and C). Frequencies of these patterns for the amplified fragment were 0.21, 0.26 and 0.53, respectively. Statistical analysis revealed that TG-repeat had a significant effect on average daily milk production (P

(Co) variance components and genetic parameters for growth traits in Arman sheep were estimated, using data collected during an 11-year period (1999-2010), by applying the restricted maximum likelihood (REML) procedure under univariate and bivariate animal models. The studied traits were body weight of lamb at birth (BW), body weight at 3 months of age as weaning weight (WW), body weight at 6 months (6MW), body weight at 9 months (9MW), yearling weight (YW), average daily gain from birth to weaning (ADG) and the Kleiber ratio (KR) from birth to weaning. Significant random effects for each trait were determined by AIC test fitting the additive direct genetic effect, additive maternal effect, covariance between additive direct and additive maternal effect, maternal permanent environmental and maternal temporary environmental (common litter) effects under nine animal models. Univariate analyses were carried out under the most appropriate model, determined by AIC test. Direct heritability estimates for BW, WW, ADG, KR, 6MW, 9MW and YW were 0.03 ± 0.02, 0.15 ± 0.02, 0.16 ± 0.02, 0.04 ± 0.03, 0.15 ± 0.04, 0.08 ± 0.04 and 0.16 ± 0.02, respectively. Maternal additive genetic effect was fitted only for BW, WW and ADG; corresponding estimates of 0.20 ± 0.02, 0.13 ± 0.01 and 0.07 ± 0.03 were obtained for maternal heritability of BW, WW and ADG, respectively. Maternal permanent environmental effects had a small contribution in expression of pre-weaning growth traits and 6MW, and led to estimates of 0.05 ± 0.02, 0.06 ± 0.04, 0.12 ± 0.03, 0.07 ± 0.02 and 0.06 ± 0.03 for maternal permanent environmental variance as a proportion of phenotypic variance (c2) of BW, WW, ADG, KR and 6MW, respectively. The magnitude of ratio of common litter variance to phenotypic variance (l2) was 0.07 ± 0.02 and 0.09 ± 0.02 for BW and WW, respectively. Direct genetic correlations were positive and ranged from 0.08 for KR-YW to 0.83 for WW-ADG; the phenotypic ones ranged from 0.19 for KR-9MW to 0.96 for WW-ADG. The results showed that the inclusion of maternal effects in genetic evaluation of early growth traits in Arman sheep is of crucial importance.

(Co)variance components and genetic parameters for test day ewe body weight of Lori-Bakhtiari sheep were estimated using a random regression model (RRM). The data consisted of 22153 individual body weight records, obtained from 1994 ewes (progeny of 205 sires and 1010 dams) between 371 and 3416 days of age, collected from the flock stud of Lori-Bakhtiari Sheep Breeding Station in Shahrekord, Iran during 1989 to 2008, with a total of 2225 animals in the pedigree. The model included the fixed effects (year of production, litter size and stage of production cycle) and random additive genetic, permanent environmental and residual effects. Random regression models were fitted with order 1 to 5 (k = 2 to 6) for additive genetic and permanent environmental effects. The residual variance in each model was assumed to be homogeneous or heterogeneous with 9 age classes. Results indicated that the 5th order (k = 6) with heterogeneous residual variance was more appropriate than others. Based on selected RRM, the additive genetic variance, permanent environmental variance and phenotypic variance increased with the ewe age. The heritability estimates were 0.38 ± 0.04, 0.44 ± 0.04, 0.42 ± 0.04, 0.38 ± 0.04, 0.37 ± 0.05, 0.42 ± 0.06, 0.48 ± 0.10 and 0.50 ± 0.14 for the ewe body weights at 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5 and 8 years of age, respectively. The proportion of permanent environmental variance to phenotypic variance ranged from 0.16 ± 0.04 to 0.39 ± 0.05. Genetic and phenotypic correlations of ewe body weight between consecutive test days were high, but decreased when the interval between body weight measurements increased, ranging from 0.45 ± 0.08 to 0.99 ± 0.09 and 0.37 ± 0.05 to 0.73 ± 0.01, respectively. Thus, due to moderate genetic correlations between ewe body weight at early and older ages, genetic analysis using RRM may be recommended for improvent of ewe body weight in Lori-Bakhtiari sheep.

The objective of the current study was to estimate the genetic parameters for body weight traits at different ages in Iran-Black sheep. Data collected during a 24-year period (1984-2008) on body weight were used to model the growth trajectory and estimate genetic parameters. Studied traits were birth weight (BW), weaning weight at 3 months of age (WW), 6 months weight (6MW), 9 months weight (9MW) and yearling weight (YW). Genetic parameters were estimated using the restricted maximum likelihood (REML) procedure under univariate and multivariate animal models. Random effects were explored by fitting additive direct genetic effects, maternal additive genetic effects, maternal permanent environmental effects, the covariance between direct and maternal genetic effects and common litter effects in twelve different models for analysis of each trait. Direct heritabilities estimated for BW, WW, 6MW, 9MW and YW were 0.02, 0.14, 0.16, 0.25 and 0.34, respectively. Maternal additive genetic variance had significant effects on the expression of body weights from birth to six months of age; resulting in values of 0.24, 0.02 and 0.09 for maternal heritability of BW, WW and 6MW, respectively. Maternal permanent environmental effects were only significant for BW, WW and 9MW leading to estimates of 0.09, 0.13 and 0.08 for maternal permanent environmental variance as a proportion of phenotypic variance (c2) for these traits, respectively. The magnitude of the ratio of common litter variance to phenotypic variance (l2) was 0.24 and 0.13 for BW and 6MW, respectively. The present study showed the importance of inclusion of maternal effects in designing appropriate breeding programs for genetic improvement in Iran-Black lambs for body weight.

The Japanese quail has been utilized as a research species in establishing the genetic relationships that may also be present in other species. Divergent phenotypic selection for 4-wk BW was conducted for three generations in high (HW) and low (LW) lines. Within each line, 50 females and 25 males were selected among 600 birds, based on 4-wk BW. Mean BW at 4 wk of age in the base generation was 186.2 and 178.6 g for females and males, respectively. In the 3rd generation, the mean of 4-wk BW for male and female birds was 214.5 and 208.1 in HW line and 173.5 and 167.8 in LW lines, respectively. The realized heritability was estimated as 33.4% and 28.3% for females and males in HW lines and 20.3% and 20.2% for females and males in LW lines. The results suggested the effectiveness of phenotypic selection for body weight in Japanese quails, although the hatchability decreased in the heavier birds.