Heterozygous Inverdale ewes show increased ovulation rate sensitivity to pre-mating nutrition

Area of Science:

• Animal Science
• Reproductive Biology
• Genetics

Background:

• Nutritional manipulation increases ovulation rate (OR) in sheep.
• The effect of nutrition on OR in ewes with naturally high OR, such as those carrying the Inverdale mutation (I+), is not well understood.
• The Inverdale mutation in the bone morphogenetic protein-15 (BMP15) gene is associated with high OR.

Purpose of the Study:

• To determine if ewes heterozygous for the Inverdale mutation (I+) exhibit altered sensitivity to nutritional manipulation compared to non-carrier (++) ewes.
• To investigate the interaction between BMP15 gene status and nutritional status in regulating OR and litter size.
• To provide guidance for feed management strategies in prolific Inverdale ewes.

Main Methods:

• Two-year study involving I+ and ++ ewes.
• Ewes were allocated to high (ad libitum) or control (maintenance) pasture allowances for 6 weeks pre-mating.
• Ovulation rate was measured 8 days after synchronized estrus; weight changes were also recorded.

Main Results:

• Ewes on high nutrition gained more weight and had increased OR (+19%) compared to controls.
• I+ ewes had a higher baseline OR (+45%) and showed a significantly larger proportional increase in OR (+27%) in response to high nutrition compared to ++ ewes (+11%).
• High nutrition led to a tendency for increased litter size (+12%), with over 50% of I+ ewes on high feed producing >3 lambs.

Conclusions:

• Ewes heterozygous for the Inverdale mutation (I+) exhibit enhanced sensitivity to nutritional manipulation for increasing ovulation rate.
• BMP15 gene status interacts with nutritional signals within the follicle to regulate ovulation rate.
• Optimized pre-mating nutrition can significantly enhance reproductive potential in prolific Inverdale ewes.