Genetic relationships between reproductive and production traits in Jersey crossbred cattle.

The study aimed to estimate the genetic parameters of different reproductive traits namely age at first calving (AFC), calving interval (CI), days open (DO) and number of service per conception (NSPC) and their associations with productive traits including 305-day milk yield (305DMY), total lactation milk yield (TLMY) and lactation length (LL) of Jersey crossbred cattle maintained at Kalyani, Nadia, West Bengal, India. Genetic parameters of reproductive traits and their correlations with productive traits were estimated by Restricted Maximum Likelihood method and Bayesian approach. Using both analytical approaches, the estimates of heritability for AFC, CI, DO and NSPC ranged from 0.12 -0.15, 0.05-0.08, 0.08-0.09 and 0.04-0.06, respectively. Low proportion of variances associated with permanent environmental effect of animals (c2 effect) were detected for CI (0.08-0.10), DO (0.09-0.11) and NSPC (0.05-0.06) in both the methods. Repeatability measures for all the reproductive traits considered in this study were low to moderate in nature, which ranged from 0.09 to 0.17. Genetic correlations between different reproductive traits were positive and low (0.05) to high (0.98) in magnitude except AFC-NSPC. Low and negative genetic correlations of AFC with 305DMY and TLMY were favourable and indicated animals with high milk yield had early age of maturity. Positive genetic correlations between CI, DO and NSPC with all production traits implied the antagonism relationships among these traits, therefore in any breeding program for improvement of production traits via selection, the reproductive traits should be taken into account as well.

Genetic aspects of Wood's lactation curve parameters in Jersey crossbred cattle using Bayesian approach.

The study was undertaken to estimate the genetic parameters of lactation curve parameters of Wood's function in Jersey crossbred cattle using the Bayesian approach. Data on 33,906 fortnightly test day milk yields of 1,718 lactation records of Jersey crossbred cows, maintained at the ICAR-National Dairy Research Institute in West Bengal, were collected over a period of 40 years. The lactation curve parameters including 'a' (initial milk yield after calving), 'b' (ascending slope up to peak yield) and 'c' (descending slope after peak yield) and lactation curve traits, peak yield (ymax), time of peak yield (tmax) and persistency of milk yield (P) of individual cow for each lactation were estimated using the incomplete gamma function (Wood's model) by fitting the Gauss-Newton algorithm as an iteration method using PROC NLIN procedure of SAS 9.3. Variance components and genetic parameters of lactation curve parameters/traits were estimated by a repeatability animal model using the Bayesian approach. Estimates of heritabilities were found to be 0.18 ± 0.05, 0.09 ± 0.03 and 0.11 ± 0.04 for parameters 'a', 'b' and 'c', respectively and 0.24 ± 0.05, 0.12 ± 0.04, and 0.15 ± 0.05 for ymax, tmax and P, respectively. Repeatability estimates were 0.31 ± 0.03, 0.21 ± 0.04 and 0.30 ± 0.04 for parameters 'a', 'b' and 'c' respectively and 0.39 ± 0.03, 0.24 ± 0.03 and 0.37 ± 0.03 for ymax, tmax and p, respectively. Genetic correlations among lactation curve parameters/traits ranged from -0.75 to 0.95. Existence of genetic correlations among lactation curve parameters/traits indicated substantial genetic and physiological relationships among lactation curve parameters/traits of Jersey crossbred cattle.

Allelic variability of estrogen receptor (ESR) gene and its effect on litter traits of Doom pigs.

The present study was conducted to identify the polymorphism of estrogen receptor (ESR) gene and its biological association with litter traits (litter size at birth, litter size at weaning, litter weight at birth and litter weight at weaning) of Doom pigs native to Assam. A total of 50 adult pigs (12 males and 38 females) chosen randomly from three different herds (Herd I, Herd II, and Herd III) were utilized in the present study. Detection of polymorphism of ESR gene was done by means of PCR-RFLP method. The amplified PCR product was digested with Pvu II restriction enzyme. PCR-RFLP analysis of ESR gene revealed polymorphic banding pattern. Two genotypes viz. AA and AB were identified. AA genotype yielded one fragment (120 bp) and AB genotype yielded three fragments (120, 65, and 55 bp). BB genotype was not found in the population under study. The frequencies of A and B alleles were found to be 0.650 and 0.350, respectively, and the genotypic frequencies of ESR gene were found to be 0.300 and 0.700 for AA and AB genotypes, respectively. There was no significant (P > 0.05) effect of ESR genotype on litter traits and the population under study was not in Hardy-Weinberg Equilibrium for ESR gene. Clustal W Multiple alignment of partial sequence of ESR gene revealed single nucleotide changes at 33, 65, 70, 83, and 92nd nucleotide positions. The presence of Pvu II polymorphism and identification of single nucleotide variation of ESR gene opens interesting prospects for improvement of litter traits in Doom pig through selective breeding program, especially based on marker-assisted selection.