Ashish Chopra

Estimates of (co)variance components and genetic parameters for body weights and first greasy fleece weight in Bharat Merino sheep

(Co)variance components and genetic parameters of weight at birth (BWT), weaning (3WT), 6, 9 and 12 months of age (6WT, 9WT and 12WT, respectively) and first greasy fleece weight (GFW) of Bharat Merino sheep, maintained at Central Sheep and Wool Research Institute, Avikanagar, Rajasthan, India, were estimated by restricted maximum likelihood, fitting six animal models with various combinations of direct and maternal effects. Data were collected over a period of 10 years (1998 to 2007). A log-likelihood ratio test was used to select the most appropriate univariate model for each trait, which was subsequently used in bivariate analysis. Heritability estimates for BWT, 3WT, 6WT, 9WT and 12WT and first GFW were 0.05 ± 0.03, 0.04 ± 0.02, 0.00, 0.03 ± 0.03, 0.09 ± 0.05 and 0.05 ± 0.03, respectively. There was no evidence for the maternal genetic effect on the traits under study. Maternal permanent environmental effect contributed 19% for BWT and 6% to 11% from 3WT to 9WT and 11% for first GFW. Maternal permanent environmental effect on the post-3WT was a carryover effect of maternal influences during pre-weaning age. A low rate of genetic progress seems possible in the flock through selection. Direct genetic correlations between body weight traits were positive and ranged from 0.36 between BWT and 6WT to 0.94 between 3WT and 6WT and between 6WT and 12WT. Genetic correlations of 3WT with 6WT, 9WT and 12WT were high and positive (0.94, 0.93 and 0.93, respectively), suggesting that genetic gain in post-3WT will be maintained if selection age is reduced to 3 months. The genetic correlations of GFW with live weights were 0.01, 0.16, 0.18, 0.40 and 0.32 for BWT, 3WT, 6WT, 9WT and 12WT, respectively. Correlations of permanent environmental effects of the dam across different traits were high and positive for all the traits (0.45 to 0.98).

Strategies to Improve Livestock Genetic Resources to Counter Climate Change Impact

Global diversity of livestock in the form of many different species and breeds in a variety of production environments is indicative of the fact that it has developed over time in sync with the ecosystem. The developing world is particularly enriched with livestock breed portfolio. Natural selection has mainly acted on fitness including adaptability and reproductive success, whereas selection practised by livestock keepers and animal breeders has been need based. As against highly structured breeding programmes and intensive selection in developed world, livestock of developing world have largely been subjected to differential selection pressures in the form of their ability to survive in harsh production environments and challenged inputs. The last few decades have witnessed large-scale erosion of livestock genetic diversity. Climate change (CC) through its direct and indirect effects including its mitigation measures is believed to have influenced the erosion. Faster loss of animal genetic diversity poses greatest threat to the sustainability of the sector. The presence of varied livestock species and their breeds with widely variable performances offers the opportunity for genetic improvement. In the absence of it, we risk progress in this sector. Reorientation of livestock breeding is required to address the issues of CC. Although resource-use efficiency is imperative, careful trade-off between livestock production, productivity and adaptability will be required. Breeding strategies for livestock genetic resources to counter CC impact will not be fundamentally different in the future. Natural stratification of species and breeds of livestock shall be an important guide in the design. Appropriate policy framework, large-scale cooperation in knowledge and resources and awareness will be crucial.

Genetic Adaptability of Livestock to Environmental Stresses

The concept of adaptability revolves around fitness describing relative ability of an individual to survive and reproduce next generation to ensure continued survival of the population and is the result of natural selection over many generations. Current trend in genetic selection has severely eroded the genetic base ignoring the diversity of the production milieu, importance of adaptation, production of multiple products and social value of the livestock. The problem has been compounded with non-capturing of environmental costs though animal genetic resources (AnGR) on extensive and intensive scale are affected by direct impacts of climate change. Unplanned genetic introgression and crossbreeding has contributed to the greatest extent toward the loss of indigenous breeds. The genetic mechanism influencing fitness and adaptation is not well explored and adaptation traits are usually characterized by low heritability. Further, it may be difficult to combine the adaptation traits with high production potential as there seem to be different physiological and metabolic processes involved. Though decision regarding matching genotypes with environment or vice versa will be situation specific, the low and intermediate level of animal production in many parts of the world suggests that increased yields and efficiency will be more environmentally sustainable than extensive goals ensuring genetic diversity, environmental soundness, animal health and welfare, and social viability. Breeding for climate change adaptation or mitigation will not be necessarily different from existing programs. However, the problems associated with measuring the phenotypes relevant to adaptation have to be overcome. Breeding indices should be balanced to include traits associated with heat resilience, fertility, feed conversion efficiency, disease tolerance and longevity in addition to higher productivity, and give more consideration to genotype by environment interactions (GxE) to identify animals most adapted to specific conditions and natural stratification of breeds and species by climatic zones. Favorable correlation suggests that if major importance is placed on performance traits in stressful environments, adaptability traits would not be compromised and thus the most productive and adapted animals for each environment need to be identified for breeding purposes. Recent successes like slick hair gene in cattle, halothane gene in pig asks for extensive efforts for finding significant quantitative trait loci (QTL) for stress and exploitation of heat shock proteins (HSP). Implementation of marker-assisted breeding value estimation (MA-BVE) using dense genome map for highest possible accuracy will be a welcome step. There is a need of extensive study of interaction among the drivers of changes of climate and livestock, studying it in a composite manner. Appropriate organizational structures and adequate funding to support a climate resilient animal agriculture will be vital.

Estimates of (co)variance components and genetic parameters of growth traits in Marwari sheep

The present investigation was undertaken to estimate the (co)variance components and genetic parameters for different growth traits in Marwari flock comprising records of 1649 animals distributed over a period of 12 years (1999–2010), maintained at Arid Region Campus of Central Sheep and Wool Research Institute, Bikaner, Rajasthan, India. The estimation was done by restricted maximum likelihood procedures, fitting six animal models with various combinations of direct and maternal effects. As per likelihood ratio test, direct heritability estimates from the best model for body weight at birth, weaning, 6, 9 and 12 months of age, and average daily gain during birth to weaning, weaning to 6 and 6–12 months of age were 0.28 ± 0.058, 0.27 ± 0.050, 0.28 ± 0.049, 0.30 ± 0.080, 0.29, 0.26 ± 0.050, 0.16 ± 0.040 and 0.31, respectively. Maternal genetic effect declined from 4% at 6 months weight to 1% at 9 months and was zero at 12 months of age. Maternal genetic effect on the post-weaning traits was a carryover effect of the maternal influences during pre-weaning age. Maternal permanent environmental effects contributed 19% of the total phenotypic variation in birth weight and 8% for weaning weight. The evidence for maternal genetic effect for average daily gain was observed only during 6–12 months of age where the additive maternal heritability was estimated as 8%. The genetic correlation between direct and maternal genetic effects was found significantly large and negative for all the traits, indicating antagonistic pleiotropy, which must be considered while formulating breeding plans. A modest rate of genetic progress seems possible in the flock through selection. Genetic correlations between body weight traits were positive and ranged from 0.23 between birth weight and weight at 6 months to 0.88 between weaning weight and weight at 9 months of age. The positive and high genetic correlation of weaning weight with weight at subsequent ages suggests that genetic gain in post-weaning weight will be maintained even if selection age is reduced to 3 months.

Scope of Indirect Selection for Wool Traits in Bharat Merino Sheep in Semi Arid Region of Rajasthan

Abstract Gowane, G.R., Chopra, A., Prince, L.L.L. and Arora, A.L. 2010. Scope of indirect selection for wool traits in Bharat Merino sheep in semi arid region of Rajasthan. J. Appl. Anim. Res., 37: 97–100. Estimates of covariance components along with genetic, phenotypic and environmental correlation were obtained for different wool traits, viz. greasy fleece yield (GFY), staple length at six month (SL), medullation percentage (MED) and, fiber diameter (FD) in Bharat Merino Sheep developed and maintained at the Central Sheep & Wool Research Institute, Avikanagar, India. Twenty years data were analyzed by restricted maximum likelihood, (REML) fitting univariate and bivariate animal models. Additive genetic variability for all the traits was low except greasy fleece yield (h2 = 0.16). Permanent environmental variance as a proportion of phenotypic variance (c2) for GFY was 0.26. Genetic correlation between GFY and SL was 0.21, between SL and MED 0.19 and SL and FD 0.20. For further genetic improvement in this breed, MED and FD should be kept restricted at present level (MED: 18.08μ and FD: 1.25%) and emphasis should be given on GFY and SL, which are positively (favorably) associated with each other.

Climate Change Impact on Sheep Production: Growth, Milk, Wool, and Meat

Sheep production is looked upon as the primary meat industry in the future due to production efficiency of mutton and adaptability of the sheep to changing climate. More than 50% small ruminants of the world are located in arid region, indicating their adaptability and future suitability to increasing temperatures. Sheep graze in the ranches, wastelands particularly in Asian and African countries, and also in pasturelands of Australia; this not only reduces emission of the greenhouse gases (GHG) but also increases fertility of land. Increased temperatures will be the first impact of climate change. Cyclones, droughts, heavy rainfall, unpredictable climate, and diseases are other factors which will affect the sheep husbandry; however threats posed by these factors can also be ameliorated with scientific planning and execution. Disease resilience in genomics of sheep can be exploited apart from nutritional interventions for mitigating these challenges. 2050 will see a high demand of food from exisiting resources to feed ~10 billion people, and sheep will play a major role with advanced genomic selection. In sheep, growth traits and meat quality are important criteria. Selection of sheep breeds and candidates that are high producing and also tolerant to the adverse effects can be a mitigating option. Reaction norms in genotype by environment interaction are important, and selection of genotypes for suitability in the future needs considerable research inputs. Revised selection criteria may be a need of the future, where production in the compromised environment seems to be the need of time. The decline in profitability of wool and environmental impacts have forced wool to take backstage; however, wool fiber production consumes significantly less energy than popular man-made fibers. Importance of the sheep husbandry as sustainable livelihood option for landless, marginal, and small farmers needs to be realized along with its global emergence as the desired food animal in the climate change era.