Strategies for improving reproductive performance in gilts
Efficient pork production is largely dictated by the reproductive success of the sow. Identifying gilts with the ability to produce an optimal number of pigs over successive parities, and do so in as few days as possible is the fundamental key to improving sow lifetime productivity. Low heritability and effect of external factors such as heat stress, makes selecting for reproductive success problematic. Age at puberty is predictive of sow longevity and has been associated with vulva development at approximately 100 days of age. To determine the effectiveness of scoring gilts according to prepubertal vulva width as a means of identifying reproductive superior replacements, physical measurements were recorded at 15 weeks of age and performance was tracked through production. Gilts assigned lowest possible scores based on prepubertal vulva development proved to be less likely to farrow a litter, had an increased age at first farrowing, and showed poorer productivity through their second parity. In addition to maximizing productivity, mitigating negative influences on reproduction is also vital for sow farm sustainability. Heat stress contributes to significant economic losses annually in the swine industry, and results in decreased farrowing rates, smaller litters, and greater wean-to-estrus intervals. To determine the effect of heat stress (HS) on corpus luteum function and the effect on early conceptus development, gilts were assigned to HS or thermal neutral (TN) conditions and either received altrenogest (a progesterone receptor agonist) supplementation or a control group that was not supplemented. Corpus luteum weight was affected by environment and supplementation, however, this change was not reflected in luteal or circulating progesterone concentrations. Conceptus development was accelerated in those supplemented with altrenogest with a higher percentage of conceptuses transitioned into a filamentous conformation. Conceptus stage of development remained unaffected when environmental assignments were compared. Collectively, these findings provide new insight into the areas of gilt development and selection, and the possible effects heat stress has on early pregnancy, and provide potential management strategies that can be implemented by pork producers.