Fat supplementation in the diet influences reproductive performance of lactating ruminants. Changes in the fat supply alter fatty acid composition and this can affect physical properties of cell membranes. This study examined the effect of rumen bypass polyunsaturated fatty acid (PUFA) supplementation on oocyte quality, chilling sensitivity, and lipid phase transition in oocytes of the sheep. Ewes were fed a diet supplemented with calcium soaps of fish oil for 13 weeks. More follicles and oocytes were found in the ovaries of ewes supplemented with PUFA than in control ewes. The number of high-quality oocytes was higher in ewes fed PUFA than in control ewes (74.3 and 57.0%, P < 0.05, respectively). Evaluation of phospholipid fatty acid composition indicated that PUFA were present in small proportions in oocytes, and eicosapentaenoic acid and docosahexaenoic acid were absent. Supplementation with PUFA increased the proportion of long chain unsaturated fatty acid in the plasma and cumulus cells phospholipids by 7.4 and 12.7%, respectively (P < 0.05). Integrity of oocyte membranes following chilling (16 degrees C, 15 min) was improved by PUFA supplementation increasing from 62.5 to 90.0% (P < 0.05). Due to changes in the oocyte's fatty acid profile, physical properties of the membrane were changed and the midpoint temperature of lipid transition reduced by 11 degrees C. These results suggest that supplementation of rumen bypass PUFA to ruminant diets can change fatty acid composition of follicle components and influence parameters such as number and quality of oocytes and their chilling resistance.

The fertility of dairy cows decreases during the summer and remains low during the cooler autumn although the animals are no longer under heat stress. The aim of this study was to characterize a delayed effect of summer heat stress on oocyte quality in the autumn and to improve oocyte quality by enhanced removal of follicles damaged during the previous summer. Lactating cows (n = 16) were subjected to heat stress during the summer. In autumn, ovarian follicles (3-7 mm in diameter) were aspirated by an ultrasound-guided procedure during four consecutive oestrous cycles. Follicles were aspirated from control cows on day 4 and from treated cows on days 4, 7, 11 and 15 of each oestrous cycle. All cows received PGF(2alpha) and GnRH injections on days 19 and 21, respectively, and maintained cyclicity, as indicated by plasma progesterone concentrations. On day 4 of each cycle, the oocytes recovered were examined morphologically, matured and activated in vitro, and cultured for 8 days. In cycle 1 (early October) both groups showed low percentages of grade 1 oocytes, cleavage, four- and eight-cell embryos, morulae and parthenogenetic blastocysts. Subsequently, the number of grade 1 oocytes increased earlier (cycle 2) in treated than in control cows (cycle 3; P < 0.05). The cleavage rate in the control group remained relatively low throughout (32-58%), whereas in the treated group it increased from 40% (cycle 1) to 75% (cycles 3 and 4; P < 0.05). The number at each stage of embryo development increased slightly but remained low throughout in the control group, whereas in the treated group significant (P < 0.05) increases of all stages were observed in cycles 3 and 4. The results show a delayed effect of summer heat stress on oocyte quality and embryo development in the autumn. Enhanced removal of the impaired cohort of follicles led to earlier emergence of healthy follicles and high quality oocytes in the autumn.

Reproduction (

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BackgroundCopy number variation (CNV) has been recently identified in human and other mammalian genomes, and there is a growing awareness of CNV's potential as a major source for heritable variation in complex traits. Genomic selection is a newly developed tool based on the estimation of breeding values for quantitative traits through the use of genome-wide genotyping of SNPs. Over 30,000 Holstein bulls have been genotyped with the Illumina BovineSNP50 BeadChip, which includes 54,001 SNPs (~SNP/50,000 bp), some of which fall within CNV regions.ResultsWe used the BeadChip data obtained for 912 Israeli bulls to investigate the effects of CNV on SNP calls. For each of the SNPs, we estimated the frequencies of occurrence of loss of heterozygosity (LOH) and of gain, based either on deviation from the expected Hardy-Weinberg equilibrium (HWE) or on signal intensity (SI) using the PennCNV "detect" option. Correlations between LOH/CNV frequencies predicted by the two methods were low (up to r = 0.08). Nevertheless, 418 locations displayed significantly high frequencies by both methods. Efficiency of designating large genomic clusters of olfactory receptors as CNVs was 29%. Frequency values for copy loss were distinguishable in non-autosomal regions, indicating misplacement of a region in the current BTA7 map. Analysis of BTA18 placed major quantitative trait loci affecting net merit in the US Holstein population in regions rich in segmental duplications and CNVs. Enrichment of transporters in CNV loci suggested their potential effect on milk-production traits.ConclusionsExpansion of HWE and PennCNV analyses allowed estimating LOH/CNV frequencies, and combining the two methods yielded more sensitive detection of inherited CNVs and better estimation of their possible effects on cattle genetics. Although this approach was more effective than methodologies previously applied in cattle, it has severe limitations. Thus the number of CNVs reported here for the Holstein breed may represent as little as one-tenth of inherited common structural variation.

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