By Mark Knauer, North Carolina State University
Perhaps the most important time period in gilt development is growth from birth to weaning. It appears nutrition during this phase may prime a female’s reproductive engine. This would mean maximizing colostrum and nutrient intake during the pre-weaning phase is vital to gilt’s subsequent reproduction.
The importance of maternal influence on the subsequent reproduction in female pigs has been known for many years (Robison, 1976), yet the pig industry has struggled to utilize this knowledge in developing management strategies to maximize reproductive throughput at the commercial level. This column will overview three studies conducted at North Carolina State University outlining the importance of pre-weaning environment on subsequent reproduction.
Nelson and Robison (1976) were perhaps the first to identify a pre-weaning management strategy to enhance subsequent sow lifetime productivity. In that study, strategic cross-fostering was used to standardize litters to six (small) or 14 (large) piglets nursed. The authors reported gilts reared in small litters had greater weaning weights and corpora lutea and tended to have greater subsequent litter size when compared to gilts reared in large litters. Yet embryo survival and age at puberty did not appear different between gilts reared in small or large litters.
Flowers (2009) built upon the study by Nelson and Robison (1976). A total of 3,180 gilts were evaluated from a factorial arrangement of treatments including season of birth (spring or fall); litter size reared (<seven littermates or >10 littermates); and puberty stimulation (boar exposure at 140 days of age; boar exposure at 140 days of age plus PG600; or boar exposure at 170 days of age). Results showed both a smaller neonatal litter size and early puberty stimulation improved stayability to Parity 6. The author further reported sows reared with seven or fewer littermates gave birth to an average of 11.0 piglets over six parities compared with 10.5 piglets for sows reared in litters of 10 or more piglets.
Hence both Nelson and Robison (1976) and Flowers (2009) reported strategic cross-fostering could be used to enhance subsequent reproduction. Both studies showed gilts reared in smaller litters had superior reproductive characteristics when they eventually became sows. Yet it is unclear whether improved pre-weaning growth, less competition among littermates or both factors explained the superior reproduction of gilts reared in small litters.
Perhaps Knauer (2016) helps explain the results of Nelson and Robison (1976) and Flowers (2009). Pre-weaning data was collected on 12,943 individual gilts. Pre-weaning factors of the gilt’s birth litter included total number born, number nursed, number weaned, litter sex ratio, cross-foster status, weaning age, birth dam parity and individual traits birth weight, weaning weight (adjusted to 21 days of age) and pre-weaning average daily gain. Gilts were traced from finishing facilities to commercial sow farms (n = 11) in eastern North Carolina.
Results showed the number of littermates did not impact subsequent female reproduction yet pre-weaning average daily gain consistently enhanced subsequent sow lifetime productivity. This suggests results from Nelson and Robison (1976) and Flowers (2009) were driven by differences in pre-weaning growth rather than competition among littermates. Collectively, results suggest research and extension efforts are needed to identify and implement strategies to increase gilt pre-weaning growth in gilt multiplication herds. Perhaps strategies to increase colostrum intake per pig and pre-weaning nutrient intake per pig should be explored in relation to subsequent reproduction.
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Flowers, W. L. 2009. Effect of neonatal litter size and early puberty stimulation on sow longevity and reproductive performance. National Pork Board project #05-082.
Knauer, M. K. 2016. Effects of Preweaning factors on Sow Lifetime Productivity. National Pork Board project 11-146. (Joe Cassady designed and conducted study)