Authors
1
Department of Animal Science, Chahatmahal Bakhtiari Agricultural and Natural Resources Research and Education Center
2
Department of Animal Science, Chaharmahal Bakhtiari Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Shahrekord, Iran.
3
Faculty member, Ilam University
4
. Associate Professor, Department of Animal Science, Faculty of Agriculture, Shiraz University, Shiraz, Iran.
5
Department of Animal Science Research, Chaharmahal and Bakhtiari Agricultural and Natural Resources Research and Education Center, Agricultural Research Education and Extension Organization (AREEO), Shahrekord, Iran
6
Animal Science Research Institute of Iran, Agricultural Research, Education and Extension Organization, Karaj, Iran
Abstract
Background and objectives: Ewes show estrus signs during reproduction season the in the sheep production systems and generally, the average ewes litter size is one. Therefore, due to high cost of production, sheep production is not economic. Reproduction efficiency depends on factors such as period of the breeding season, ovulation rate, conception rate, pregnancy rate, litter size and lamb viability. The interaction effect of nutrition and environment influences all of these factors. Nutrition is one of the most important factors on the ruminant’s reproduction, which has an impact effect on the overall reproductive activity during their life. Nutrients like fat show their effect on the reproduction by changing the concentrations of plasma metabolites and hormones. Hence, the objective of the present study was to investigate the effect of dietary fatty acid (FA) supplements around mating on body weight (BW) change, hormones concentration, lamb sex and birth weight and reproductive performance of Lori-Bakhtiyari ewes.
Materials and methods: One hundred and five Lori-Bakhtiyari ewes were divided into three equal groups based on age (2-4 year) and body weight (54.58 ± 1.6 kg) and randomly allocated to experimental diets (n=35). Basal diet supplemented with 10% (DM basis) calcium salt of omega-6 FA, 10% calcium salt of omega-3 FA and 10% calcium salt of saturated FA (SFA). Ewes of each group fed respective experimental diet from 30 d pre- to 30 d post-mating. Serum concentrations of hormones (insulin, estradiol and progesterone) were measured. Reproductive performance including lambing rate, twining rate, the proportion of female lambs, the proportion of male lambs, lamb birth weight and weaning weight and litter size were recorded.
Results: The results showed that feeding fat supplements did not affect on BW change of ewes. Serum concentrations of insulin, estradiol and progesterone were not influenced by the experimental diets (P > 0.05). The proportion of female lambs was higher when ewes were fed diet containing omega-6 FA compared with the other dietary groups (P < 0.05). Lambing rate, twining rate, lamb birth weight and weaning weight were not affected by different fat supplements (P > 0.05).
Conclusion: It was concluded that feeding a diet containing calcium salts of omega-6 FA around mating, can skew the sex ratio of lambs toward females. The interaction effect of dietary FA sources with other nutrients on the sex ratio of lambs could be investigated in future research. However, further research is required to confirm these findings.
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