Genetic analysis of the effects of heat stress before and after lambing on pre-weaning live weight in Spanish Merino lambs.

BACKGROUND: Heat stress (HS) is a major environmental effect on sheep production. Hereby, we estimated the genetic (co)variance component of HS on the pre-weaning performance of 19,022 Merino lambs by analysing the climatological index of temperature and relative humidity (recorded 30 days before lambing and after lambing) using transversal and longitudinal mixed linear models. METHODS AND RESULTS: The global impact of HS during the last 30 days of pregnancy was -17% for birthweight and ranged between -4% and -8% for live weight at 15, 30 days of age (W30), and average daily gain from birth at 30 days. The results from both statistical approaches showed very similar heritabilities (h2 ), ranging from 0.192 to 0.237 for the direct genetic (D) effects and from 0.072 to 0.082 for the maternal genetic (M) effects, but the antagonism between (D) and (M) was higher when a longitudinal model was used. A significant genotype-environmental effect was also found regardless of whether the climatological covariables were considered in the model. In addition, we employed D and M breeding values for W30 as an example to create a new subjacent index by first using a principal component analysis and employing the leading eigenvalues as a weighted factor that provides the information needed to identify those genotypes that maximise the response for both genetic effects over a wide range of climate-environment levels. CONCLUSIONS: Our study revealed that the HS indexes of the mother during the gestation period have a significant effect on the growth of the lambs during the early stages of life.

Short-term glutamate administration positively affects the number of antral follicles and the ovulation rate in cyclic adult goats.

The acute effects of short-term glutamate administration on the number of antral follicles and ovulation rate were examined in adult goats. Neither live weight (44.5±1.3 kg) nor body condition (3.3±0.8 units) differed between the control (untreated) and glutamate-treated (0.175 mg/kg) animals (p>0.05). However, the number of antral follicles (3.4 vs. 2.1, p=0.05) and ovulation rate (2.5 vs. 1.5, p=0.05) was higher in the glutamate-administered group than in the controls.

Genetic variation at the goat hormone-sensitive lipase ( LIPE) gene and its association with milk yield and composition.

Hormone-sensitive lipase (LIPE) plays a fundamental role in the regulation of energy balance by releasing free fatty acids from adipose triacylglycerol stores. These fatty acids can be subsequently transferred to other body compartments to be oxidized or employed in other biochemical reactions. This enzymic function is particularly important in lactating animals because the synthesis of milk components involves the mobilization of lipid depots to satisfy the large energy demands of the mammary gland. In the current study, we partially sequenced the goat LIPE gene in several individuals. In doing so, we identified two synonymous polymorphisms at exons 2 (c.327C>A>T, triallelic polymorphism) and 3 (c.558C>T). Moreover, we found a mis-sense polymorphism at exon 6 (c.1162G>T) that involves an alanine to serine substitution at position 388. Analysis with Polyphen and Panther softwares revealed that this amino acid replacement is expected to be neutral. Performance of an association analysis with a variety of milk traits revealed that goat LIPE genotype has highly suggestive effects on milk yield (P=0.0032) as well as on C18:3 n-6g (P=0.0051), trans-10 cis-12 CLA (P=0.007) and C12:0 (P=0.0084) milk contents. These associations are concordant with the preference of LIPE to selectively mobilize medium-chain and unsaturated fatty acids.