The effect of dietary protein on reproduction in the mare. VII. Embryonic development, early embryonic death, foetal losses and their relationship with serum progestagen.

This study finds that mares fed a low-quality protein diet displayed higher instances of early embryonic loss, suggesting the quality of protein in horse diets could impact reproductive success. This relationship may also be associated with altered serum progestagen concentrations.

Research Methodology

• The researchers used a sample size of sixty-four Thoroughbred and Anglo-Arab mares aged 6-12 years. These mares were randomly distributed into four different dietary groups.
• The diets differed in their total protein content and quality, specifically considering essential amino acids.
• Among the sample, forty mares were non-lactating, and the rest, twenty-four mares were lactating. However, eight of these mares were eventually excluded from the study due to injuries or gynecological pathology.

Results

• The study achieved an overall conception rate of 94.6% and a foaling rate of 80%, which compares pregnancy and birth rates.
• It was observed that five out of fourteen mares (Group 1) fed a low-quality protein diet suffered from early embryonic loss before 90 days of pregnancy. In comparison, only three out of forty-one mares suffered embryonic loss in the remaining groups which were fed higher-quality protein diets.
• This suggests that the quality of protein in the diet had an effect on early embryonic loss, indicating its influence on reproduction.
• Evidence of luteal function insufficiency during the initial 40 days post-ovulation was seen through the serum progestagen concentrations in Group 1. Luteal function insufficiency is often associated with early pregnancy loss.
• The study also noted weight fluctuations among the mares in different groups. Non-lactating mares in all groups gained weight, while lactating mares in the low-quality protein group (Group 1) lost weight during lactation. These weight changes might have an additional effect on the success of pregnancy.
• No significant difference was found in the diameter of the embryonic vesicle between dietary groups until Day 35 of pregnancy.

Conclusion

• The study concludes that the quality of dietary protein can influence reproduction in mares. Mares fed lower quality protein showed higher rates of early embryonic loss.
• This may be due to luteal function insufficiency as indicated by altered serum progestagen concentrations. The study also suggests that lactation and diet can affect body mass changes, which may in turn impact reproductive success.