Genetic evaluation of semen production potential in Indigenous bulls using random regression models in a Bayesian framework.

Genetic potential of indigenous bulls with respect to semen production traits over the age of the bulls at semen collection was analyzed using random regression models (RRMs). Data pertaining to 59,641 ejaculates from 189 bulls of 18 indigenous breeds collected from BAIF (Bharatiya Agro Industries Foundation) was utilized for this study. Six semen production traits, viz., ejaculate volume (EV, ml), sperm concentration (SC, 109/ml), initial sperm motility (ISM, %), post-thaw motility (PTM, %), the total number of spermatozoa per ejaculate (TNS, 109/ejaculate), and the theoretical number of semen doses (TNSD) were studied. Univariate and RRM were used to obtain variance components and genetic parameter estimates. Two hundred thousand Gibbs samples were generated for each trait with a burn-in of 20,000 and thinning interval of 50 in a Bayesian framework. Legendre polynomials with orders of fit up to 5 for additive and permanent environmental effects were used. RRM modeled the heritability and repeatability for all ages between 3 and 10 years (productive lifespan). Heritability estimates ranged from 0.18 to 0.36, 0.18 to 0.45, 0.02 to 0.06, 0 to 0.001, 0.09 to 0.32, and 0.14 to 0.42 while the repeatability estimates ranged from 0.41 to 0.72, 0.36 to 0.79, 0.04 to 0.10, 0 to 0.001, 0.37 to 0.56, and 0.32 to 0.57 for EV, SC, ISM, PTM, TNS, and TNSD, respectively. Variability of estimates over the age of the bulls obtained through RRM could be useful to further refine the breeding program for age at selection, deciding the production period and age at culling.

Genetic and non-genetic factors affecting conception rate of frozen semen in small holder dairy farmer system of rural India.

Fertility traits are as important as production traits in crossbred bovine population. Assessment of the fertility of bull in any frozen semen production program and evaluation of the conception rate under actual field conditions provide valuable information. The objective of this retrospective study was to estimate the effect of genetic and non-genetic influence on conception rate of frozen semen bulls maintained at Bharatiya Agro-Industries Foundation (BAIF) Pune based on the conception rate in cattle population of small holder dairy farmer system. The data comprising of 1,08,238 insemination records pertaining to 83 Holstein Friesian pure and crossbred bulls available at BAIF Pune were used to analyze conception rate. The fixed effect solutions and covariance components were estimated by linear mixed model using the restricted maximum likelihood method in WOMBAT software. The genetic correlations were estimated using bivariate analysis between post thaw motility and conception rate. The study was based on fertility related information from cows maintained in different villages of India and thus reflects the actual fertility of frozen semen used. The study was suggestive of influence of very small fraction of genetic effect and higher impact of management effect on conception rate. Fertility-related information available from this study is an invaluable asset in decision making process of breeding policies.

Semen production and semen quality of indigenous buffalo breeds under hot semiarid climatic conditions in India.

Semen data comprising of 97,023 ejaculates of 197 bulls from 6 buffalo breeds were analyzed. The traits considered were as follows: ejaculate volume, sperm concentration, mass activity, initial and post-thaw motility, total sperm, and total motile sperm before and after thawing as well as a composite trait equal to the theoretical number of doses which can be produced from each given ejaculate. The objective was to measure the semen production potential of indigenous buffalo bulls and identify factors affecting these traits. A linear mixed model was used, including a random bull effect along with other fixed factors: the order of the ejaculate on a particular day, the interval between collections, the time of collection, the breed, the age at collection, the semen collector, and the year and month of collection. The study showed breed wise variation for all traits. The first ejaculate of a bull on a particular day was superior to the second for nearly all the traits. Longer collection intervals are better than shorter intervals for all the parameters, although short collection interval of 2 to 4 days produced higher yield in terms of total semen doses without hampering semen quality. The study also showed a slight decrease of semen quality with time of collection within a day. The Murrah breed showed comparatively consistent performance during their whole life compared with the other breeds. Repeatability estimates for semen traits were found to be low (0.09 for mass activity) to relatively large (> 0.4 for volume and concentration). A negative correlation was found between bull effects for semen volume and concentration while a high positive correlation was found between mass activity, initial motility, and post-thaw motility. Results of the study will help in suggesting suitable management and breeding plans for semen production traits.