Journal of Livestock Science and Technology
Volume:11 Issue: 2, Dec 2023

The objectives of this study were 1) to compare models to describe the lactation curve of the Saanen, Moxotó, and Anglo-Nubian 2) to evaluate the effect of genetic groups on production and composition milk and efficiency of mobilization of body reserves during lactation. Twenty-three multiparous goats, newly calved, were divided into three treatments (genetic groups: 9 Saanen, 8 Moxotó, and 6 Anglo-Nubian). The goats were randomly distributed in collective pens, under the same feeding conditions. Five mathematical models were used to adjust the lactation curves: Wood (WD); Papajcsik and Bodero (PB); Adapted from Papajcsik and Bodero (APB); Nelder (ND) and Wilmink (WM). To indicate the best fit, the model evaluation system software was used, performing additional analyzes with the observed and predicted values ​​for each fitted equation. There were differences (P<0.05) in the parameters a, b and c between the genetic groups in each mathematical model. The APB model is recommended for use in all genetic groups to evaluate milk yield (Y), following the parameters: Y = 1.196+0.0545×t×e (-0.038×t) for Saanen, Y = 0.297+0.031×t×e(-0.0462×t) for Moxotó and Y = 0.757+0.0554×t×e(-0.0417×t) for Anglo-Nubian. The results for average milk production during 27 weeks of lactation were 1.37; 0.37 and 0.9 kg d-1 for Saanen, Moxotó and Anglo-Nubian, respectively. Except for lactose, there was a difference (P<0.05) between the genetic groups for milk composition and plasma beta-hydroxybutyrate (BHB) levels. Considering milk composition, the Saanen, Moxoto and Anglo Nubiana presented the averages (%) for fat of 3.66, 6.75, and 5.10, protein 3.32, 4.97, and 4.18 and lactose 4.28, 4.46, and 4.39%, respectively. There was no effect (P>0.05) on B-HBO in response to days of lactation, but Saanen and Anglo Nubian goats had higher plasma levels of this metabolite compared to Moxotó goats. Saanen had a greater weight loss of 12.83 kg, which was verified at 35 days of lactation. Saanen and Anglo-Nubian animals have a greater ability to mobilize body reserves compared to Moxotó. APB model is adequate to describe milk production of goats in tropical areas.

The purpose of this experiment was to study the effects of silage type (ST) and levels of silage particle size (SPS) on feed intake, digestibility, rumen parameters, and feed intake behavior in Kermani sheep. Corn and millet crops were cultivated in May and harvested into coarse and fine forages in mid-September. Four rams (two years old, BW 39.2±3.1 kg) were randomly assigned to four treatments in a 2×2 factorial arrangements in a Latin square design. The experimental diets were coarse corn silage diet; short corn silage diet; coarse millet silage diet and short millet silage diet. Diets were iso-nitrogenous and iso-energetic, and the ratio of forage to concentrate was 50:50. The potential of gas production was higher in corn silage (CS) than millet silage (MS) (P<0.03) and coarse SPS than short SPS (P<0.02). The dry matter (DM), organic matter (OM) and crude protein (CP) intakes were higher in short SPS diets while DM, OM and neutral detergent fiber (NDF) digestibility were higher in CS diets (76.26, 73.43 and 58.71%, respectively), while the CP digestibility was higher in short SPS diets (74.98%). The mean ruminal pH value was lower in CS diets (P<0.05). The mean ruminal ammonia nitrogen (NH3-N) concentration was higher in CS and short SPS diets. Microbial protein (MP) synthesis was higher in short SPS diets (P<0.05). Chewing activity was higher in MS and short SPS diets (P<0.05). The results indicated the higher quality of CS, although MS can be safely fed to small ruminants such.

In the present study, collagenolytic activity was investigated in two separate experiments using blood plasma or serum. Two separate experiments were conducted at different times. The first experiment involved the analysis of blood plasma from 16 rams, 6 goat bucks, and 3 lactating cows. The rams and goat bucks were randomly divided into two equal heads groups (control and treated), and they did not exhibit any sexual problems. In the second experiment, twelve calves (5 males and 7 females) with a mean age 152 days, and weight of 128 kg, were selected and randomly divided into two groups. One group received a total mixed ration (TMR) plus a feed block (22 kg weight), while the other group received only TMR. Blood serum from all calves was utilized for collagenolytic activity. Bovine Achilles' tendon collagen served as the substrate for measuring collagenolytic activity, while hydroxyproline (HYP) was employed as a product for activity measurement. The results revealed the presence of the enzyme(s) in the blood samples of all the experimental animals, albeit at varying levels of activity. It was observed that the activity was significantly inhibited by cupric sulfate as a metal ion. Furthermore, notable positive and significant correlations were found between the daily gain of sheep and collagenolytic activity in blood samples, while negative correlations were observed between the age of the calves and collagenolytic activity. These results supported the hypothesis that enzyme activity is associated with growth. The results revealed the presence of the enzyme(s) in the blood samples of all the experimental animals, albeit at varying levels of activity. It was observed that the activity was significantly inhibited by cupric sulfate as a metal ion. Furthermore, notable positive and significant correlations were found between the daily gain of sheep and collagenolytic activity in blood samples, while negative correlations were observed between the age of the calves and collagenolytic activity. These results supported the hypothesis that enzyme activity is associated with growth.

The structure of the fixed and random parts of the genetic evaluation model plays a significant role in fitting data and the estimation of genetic parameters for economic traits in livestock. The present study was conducted to investigate the effect of different fixed and random effects combinations in an animal model framework on the general properties of the model and estimates of the genetic parameters for milk production traits. Traits studied were 305-day milk production (305-MY, 15920 records), fat percentage (FP, 27954 records), protein percentage (PP, 26183 records), average daily milk production (ADM, 30954 records) and milk somatic cell score (SCS, 25408 records) in Isfahan Holstein cows. In general, 54 scenarios were studied which differed in fixed and random parts of the model. Variance components were estimated using the animal model fitting restricted maximum likelihood (REML) procedure. The best model for each trait was selected based on the Bayesian Information Criterion (BIC). Results showed that for all traits studied, models in which the effect of contemporary groups Herd-Year-Season (HYS) or Herd-Year-Month (HYM) were fitted as the random or fixed effect together with age at the first calving and inbreeding as a classified fixed effect or covariate lead to a significantly better data fit instead of fitting herd, year, season and month of calving separately. For each trait, a wide range of heritability was obtained by fitting 54 models. Based on the best models, the estimates of heritability for 305-MY, ADM, FP, PP and SCS were 0.33, 0.28, 0.21, 0.16 and 0.61, respectively. It was concluded that a single model should not be used for analyzing all milk production traits and that for each trait a series of models which differ in random and fixed parts should be tested to find the most suitable model which describes the data best. Fitting the effects of herd and year, season and month of calving as contemporary groups the HYS or HYM was recommended for genetic evaluation of milk production traits as resulted in better data fit. Depending on the trait, inbreeding and age at first calving can be fitted as a classified fixed effect or as a covariate.

This study was aimed to assess the effects of reducing free water access time and feeding milk at various dry matter (DM) concentrations on water consumption, growth performance, DM intake (DMI), and blood metabolites of Holstein dairy calves. Sixty Holstein dairy calves [42 ± 3.0 kg of body weight (BW)] were used in a 3 × 2 factorial randomized block design with the main factors including milk DM (low, medium, and high DM; LDM, MDM, and HDM, 125, 140, and 155 g/kg, respectively) and water access time (short and long-time free water access, ST and LT respectively). Neither milk DM concentration nor water access time had any effect on the mean water intake (L/d). Increasing the concentration of liquid feed in both water provision schedules, improved the final BW, average daily gain (ADG), heart girth, and withers and hip heights. However, main blood metabolites were not affected by milk DM. The LT calves that consumed the highest milk DM (HDM) had the greatest ADG compared to other treatments (P<0.05). A trend was found for the interaction between milk DM and water access time as in the ST calves, the final BW was greater than LT at 125 and 140 g/kg milk concentrations (P=0.08) but at 155 g/kg milk DM, the highest final BW was found in LT calves. It was concluded that under the environmental condition similar to this study, water provision duration for neonatal calves could be reduced to once a day (just 2 h) however, we do not recommend increasing the DM content of milk by more than 140 g/kg when water is provided freely, 2 h once a day.

This study was conducted to evaluate the effects of dietary supplementation of different sources of zinc on the quantitative and qualitative characteristics of semen and blood testosterone in Mahabadi mature bucks. Twenty-four mature male goats (40 ± 0.86 kg), approximately 1-1.5 years old, were divided into three groups (n = 8) and assigned to experimental treatments for 56 days in a completely randomized design. The treatments included: 1) control (a basal diet containing 22.14 mg/kg zinc without zinc supplement), 2) basal diet + 35 mg/kg Zn4 as ZnSO4 (an inorganic source of Zn), and 3) basal diet + 35 mg/kg Zn as ZnMet (an organic source of Zn). Qualitative (ejaculate volume, sperm concentration) and quantitative (viability, membrane integrity, morphology, and CASA detected parameters) properties of semen and plasma testosterone and Zn, Cu, and Fe concentrations were evaluated. Results showed that ZnMet vs. ZnSO4 increased sperm membrane integrity and plasma Zn concentration and reduced morphologically abnormal spermatozoa (P≤0.05), but there were no significant differences in other parameters. Viability, membrane integrity, morphology, some of the CASA detected parameters (total motility, straight-line velocity, average path velocity, beat cross frequency of sperm), and the plasma concentration of testosterone in zinc-supplemented groups was significantly higher than the control group. In conclusion, the positive effects of an organic source of Zn were seen in reducing abnormal spermatozoa and improving membrane integrity, plasma Zn concentration, and plasma testosterone concentration.

The aim of this study was to investigate the effect of replacing equine chorionic gonadotropin (eCG) with human chorionic gonadotropin (hCG) and also improving the efficiency of hCG using a slow-release compound (alhydrogel) on the reproductive performance of Afshari ewes after laparoscopic artificial insemination. For this purpose, 48 Afshari ewes (2.5-4 years old with the mean weight of 68±2.5kg and an body condition score of 3.04±0.3 were treated with intravaginal controlled internal drug release (CIDR) for 14 days. The ewes were then divided into 4 groups: the first group: injection of eCG (400IU), 48 hours before CIDR removal (eCGS), the second group: injection of eCG (400IU) combined with alhydrogel, 48 hours before CIDR removal (eCGSR), the third group: injection of hCG (400IU), 48 hours before CIDR removal (hCGS) and the fourth group: injection of hCG (400IU) combined with alhydrogel, 48 hours before CIDR removal (hCGSR). The results showed that there was no significant difference between eCGSR and eCGS treatments in Measured parameters (P>0.05). The lowest pregnancy rate (25%) and fecundity (33%) were recorded in related to the hCGS treatment. However, in the hCGSR treatment, these parameters were increased to the values recorded in eCGSR and eCGS treatments. The results of this study showed that hCG in the presence of slow release compound can be a suitable substitute for eCG in the estrus synchronization protocol based on progesterone and eCG.

The current investigation was performed to compare the performance of standard multivariate and structural equation models for the estimation of genetic parameters of growth traits in Arman sheep. Data was collected on 2194 Arman lambs in 13 years (1999 to 2012) at Abbasabad Sheep Breeding Station, Khorasan Razavi province, north-eastern Iran. The studied growth traits were body weight at birth (BWT), weaning (WWT), six months (6MWT), nine months (9MWT), and yearling weight (YWT). The predictive abilities of three multivariate animal models comprising standard (SMM), temporal recursive (TRM), and fully recursive (FRM) models were evaluated by applying two statistical criteria including the mean square of error (MSE) and Pearson's correlation coefficient between the observed and predicted records (r(y,y ̂)). In general, TRM performed better than SMM and FRM. The lowest MSE and the highest r(y,y ̂) were found under TRM. All the posterior means for the structural coefficients were statistically significant. Spearman's rank correlation coefficients between the estimated breeding values for the body weight traits were also computed across all, 50% top-ranked, and 10% top-ranked animals. Comparisons of these correlations between posterior means of estimated breeding values of individuals for the growth traits under SMM and TRM revealed that taking the causal relationships among these traits into account could result in significant re-ranking of the animals according to the estimated breeding values; showing that TRM had more advantage over SMM for the estimation of genetic parameters and the breeding values of the studied traits in Arman sheep.