Factors Affecting the Reproductive Efficiency of American Mammoth Jackstock Donkey Mares (Equus asinus) under Subtropical Conditions of Pakistan

Donkeys are an integral part of the rural culture of Pakistan, with American Mammoth donkey stallions particularly valued for mule production.This study investigated factors influencing reproductive performance in donkey mares (jennies), focusing on hormonal treatments for estrus/ovulation induction and stallion selection on pregnancy outcomes.The study was conducted in Sargodha, Pakistan (32.0740N, 72.6861 E) and divided into two parts.The first was a five-year retrospective analysis of breeding and foaling patterns in 321 jennies under subtropical conditions.The second part was a prospective trial involving 60 jennies randomly assigned to three groups: GnRH, hCG, and control (n=20 per group).For estrus induction, 28 jennies (n 1 =28) with a corpus luteum received prostaglandin (PG), while 32 jennies (n 2 =32) exhibited natural estrus.All were bred using three randomly assigned American Mammoth donkey stallions.Chi-square tests evaluated the effects of estrus type and ovulatory treatments on ovulation rate.Binary logistic regression assessed the impact of estrus type, ovulation induction, post-breeding induced endometritis (PBIE), rebreeding, and stallion used on pregnancy rate.One-way ANOVA analyzed seasonal and monthly breeding and foaling patterns.Results showed a pregnancy rate of 68.33% (41/60).GnRH (75%) and hCG (80%) groups had higher pregnancy rates than the control (50%) (P = 0.048).Ovulation rates were 100% in GnRH and hCG groups versus 85% in controls (P = 0.043).Mean follicular sizes were not significantly different among groups (P = 0.108).PG-induced estrus resulted in a 57.1% pregnancy rate compared to 78.1% in natural estrus jennies, though not statistically significant (P = 0.307).PBIE occurred in 13.3% (8/60), but oxytocin treatment showed no significant impact (P = 0.486) on pregnancy rate.Rebreeding yielded 57.1% success versus 80.5% in single breeding (P = 0.307).Stallion choice significantly affected pregnancy outcomes (P = 0.024).Seasonal and monthly variations in breeding/foaling rates were non-significant (P > 0.05).In conclusion, American Mammoth jennies under subtropical conditions do not exhibit strict seasonality.Ovulation induction (GnRH, hCG) and stallion selection significantly influence pregnancy success, providing key strategies for optimizing donkey reproduction in Pakistan.