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 (c 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.

Roy I ，Rahman M ，Karunakaran M ，Gayari I ，Baneh H ，Mandal A ... -  《-》

Estimation of genetic parameters for production and reproductive traits in Indian Karan-Fries cattle using multi-trait Bayesian approach.

Estimates of variance components are needed for implementing genetic selection. This study was conducted to genetic parameters for production and reproductive traits on Indian Karan-Fries cattle using multi-trait repeatability animal model. Data collected from ICAR-National Dairy Research Institute, Karnal, India (from 1988 to 2019) were used. Single-trait and multi-trait repeatability animal models were used for parameter estimation. The posterior mean of Heritability estimates for 305-day milk yield (305-DMY), lactation milk yield (LMY), lactation length (LL) were 0.20 ± 0.03, 0.19 ± 0.03 and 0.06 ± 0.02, respectively. For age at first calving (AFC), calving interval (CI), and days open (DO), the posterior mean of heritability estimates were 0.24 ± 0.08, 0.06 ± 0.01, and 0.07 ± 0.02, respectively. The repeatability estimates for 305-DMY, LMY, LL, CI, and DO were 0.37 ± 0.02, 0.34 ± 0.02, 0.15 ± 0.02, 0.09 ± 0.02, and 0.12 ± 0.02, respectively. Genetic correlation between milk production traits (305-DMY, LMY, and LL) was positive and strong (> 0.80). However, the genetic correlation between milk production trait and AFC ranges from - 0.31 to 0.12. Unfavorable strong genetic correlations were observed between production and reproductive traits (CI and DO) with values ranged from 0.5 to 0.7. Phenotypic correlations among 305-DMY, LMY, and LL were generally positive and high. The moderate heritability estimates and potential genetic variation for 305-DMY, TMY, and AFC suggested that genetic gain can be obtained for these traits through genetic selection. Low heritability estimates found for LL, CI and DO, indicating that the possibility of changing these traits through genetic selection is small. High genetic correlation observed between productive and fertility traits were unfavorable. The existed strong genetic and phenotypic correlation estimates between CI and DO indicates that recording only one of them would be sufficient in the herd. As the multi-trait model showed slight improvements in the h as well as r estimates for both productive and reproductive traits over univariate analysis, future selection with a multi-trait animal model applying Bayesian approach would be recommended.

Worku D ，Gowane GR ，Kumar R ，Joshi P ，Gupta ID ，Verma A ... -  《-》

Bayesian approach for genetic analysis of production and reproduction traits in Jersey crossbred cattle.

The knowledge of genetic parameters of performance traits is crucial for any breeding programme in dairy animals. The present study was conducted to use a Bayesian approach for estimation of genetic parameters of production and reproduction traits in Jersey crossbred cattle. Data of Jersey crossbred cattle maintained at Eastern Regional Station, National Dairy Research Institute, West Bengal spread over a span of 41 years were utilized. The marginal posterior medians of heritability for 305-day milk yield (305MY), total milk yield (TMY), peak yield (PY), lactation length (LL), calving interval (CI), total milk yield per day of lactation length (TMY/LL) and total milk yield per day of calving interval (TMY/CI) were 0.31 ± 0.07, 0.29 ± 0.07, 0.27 ± 0.06, 0.16 ± 0.05, 0.15 ± 0.05, 0.29 ± 0.06, 0.27 ± 0.06, respectively. Moderate heritability estimates for 305MY, TMY, PY and production efficiency traits indicate the presence of adequate additive genetic variance in these traits to respond to selection combined with better herd management. Repeatability estimates for 305MY, TMY, PY, LL, CI, TMY/LL and TMY/CI were 0.57 ± 0.08, 0.58 ± 0.08, 0.51 ± 0.07, 0.34 ± 0.06, 0.31 ± 0.06, 0.54 ± 0.07 and 0.49 ± 0.07, respectively. Repeatability estimates for 305MY, TMY and PY were high in the current study, suggesting the use of first lactation records for early evaluation of Jersey crossbred cattle for future selection. Genetic correlations varied from 0.21 to 0.97 and maximum genetic correlation was observed between 305MY and TMY indicating that consideration of 305MY instead of TMY in breeding programmes would suffice. Positive genetic correlations of CI with 305MY and TMY indicated the antagonistic association between production and reproduction traits.

Ratwan P ，Kumar M ，Mandal A 《-》

Genetic analysis of persistency indices of milk yield in Jersey crossbred cattle.

The study reported in this Research Communication was conducted to estimate genetic parameters for different lactation persistency indices and their association with reproductive traits in Jersey crossbred cattle. Data on lactation traits (part lactation yields and 305-days milk yield) comprising all lactations as well as reproductive traits viz. calving interval, conception rate and gestation length of 378 Jersey crossbred cattle, maintained at National Dairy Research Institute, Kalyani, West Bengal, India, were collected over a period of 35 years (1982-2016). Five lactation persistency indices of animals (P21, P31, P32, P4 and P5) were calculated using ratio method. A total of six different animal models, ignoring or including maternal genetic or permanent environmental effects, were fitted for all persistency traits. The best model was chosen after testing the improvement of the log-likelihood values. The estimates of direct heritability were low in magnitude and ranged from 0.02 to 0.14 for the studied traits under the best fitted animal model. The permanent maternal environmental (c2) effects of different lactation persistency indices accounted for 2-9% of the total phenotypic variance in this study. Estimated genetic correlations of lactation persistency indices with all studied reproductive traits were low to moderate and negative (-0.11 to -0.68), except for calving interval. Phenotypic correlations of lactation persistency measures with studied reproductive traits were low (0.01 to 0.15). The low heritability estimates of all the persistency indices indicate some limited scope of genetic improvement of lactation persistency of animals through selection under the prevailing management conditions.

Koloi S ，Mandal A 《-》

Genetic analysis of first lactation and lifetime performance traits in composite Vrindavani cattle: important considerations for higher milk production.

The present study was aimed to evaluate the influence of non-genetic factors on several first lactation and lifetime performance traits and elucidate their genetic parameters in an organized Vrindavani cattle population. Data on eight first-lactation and thirteen lifetime traits were collected on 2400 cows with pedigree records that were reared during 33-year period (1989-2021). The first-lactation traits included age at first calving (AFC), total milk yield (FTMY), standard milk yield (FSMY305), peak yield (FPY), lactation length (FLL), dry period (FDP), service period (FSP) and calving interval (FCI). Whereas, the lifetime traits mainly included total lifetime milk yield (TLMY), total standard milk yield (TSMY), number of lactations completed (NL), total lactation length (TLL), herd life (HL), productive life (PL), average milk yield per day of herd life (TLMY/HL), average milk yield per day of productive life (TLMY/PL), average milk yield per day of productive life (TLMY/TLL). Other lifetime production traits included average service period (ASP), average dry period (ADP), average calving interval (ACI) and unproductive days (UD). The heritability estimates of first-lactation traits ranged between 0.026 and 0.228 and were found to be low for AFC (0.180 ± 0.042), FCI (0.191 ± 0.125), FSMY305 (0.145 ± 0.061), FTMY (0.165 ± 0.048), FDP (0.052 ± 0.049) and FSP (0.026 ± 0.033); however, FLL (0.229 ± 0.044) and FPY (0.202 ± 0.046) showed moderate heritability. Positive phenotypic correlation (p < 0.001) was revealed among FTMY, TLMY, TLL, HL and PL. The AFC produced a significant effect (p < 0.05) on several traits i,e, TLL, TLMY/HL, FSMY305, FPY, TLMY, HL and TLMY/PL. Lower AFC was associated with higher TLMY, TLL and TLMY/HL; while FSMY305, FPY, HL and TLMY/PL were higher in heifers that calved late in their life. The results revealed that AFC may be optimized with first lactation and lifetime traits for this population.

Tamilarasan K ，Ahmad SF ，Panda S ，Preethi AL ，Tarafdar A ，Pandey HO ，Gaur GK ... -  《-》