Objectives: Normal biological and management variability associated with farrowing and lactation management was used to study characteristics of the neonatal environment of replacement gilts and their relationship with sow lifetime productivity.
How research was conducted: Replacement gilts from birth litters of 14 live pigs but reduced to 13 pigs after cross-fostering had a 20% higher retention rate and produced 7 more live pigs by parity 3 compared with their counterparts born in litters of 14.5 live pigs but adjusted to 16 piglets after cross-fostering.
Physiologically, these differences in the neonatal environment influenced the expression of pubertal estrus of replacement gilts delivered to commercial farms, since significant differences in retention were first observed with the proportion of gilts with a “Heat-No-Serve” event. In terms of possible benchmarks that could be used as early selection criteria for future replacement gilts, birthweight, pre-weaning growth and weaning weight were positively associated with sow lifetime productivity. Of these, pre-weaning growth and weaning weight would be the easiest to manipulate from a practical perspective via strategic cross-fostering or use of supplemental nutritional strategies. The average weight of the testicles at castration from littermate boars was also positively associated with lifetime productivity of their gilt siblings, and in conjunction with average birth and weaning weights of replacement gilts and total number of pigs born from the same litter, accounted for 30 to 40% of observed differences in longevity. These differences in testicular weight in relation to birth weight were reflected in measurable differences in testicular and ovarian development.
What these findings mean for the industry: The results of this study indicate that birthweight, pre-weaning growth, and weaning weight of potential replacement gilts are aspects of the neonatal environment of replacement gilts that have a significant effect on their subsequent lifetime productivity and pre-weaning management of gilts in smaller litters has benefits for the subsequent selection of gilts for breeding and to a lesser extent on the retention and performance of selected gilts in the breeding herd . It appears that these early selection criteria are more accurate when used on a whole litter basis rather than when applied to individual females within a litter. The results on testicular measurements in male littermates suggests that, in addition to a low birth weight being a risk factor for poor gilt retention to breeding, a low testicular weight relative to birth weight may be an effective measure of future lifetime reproductive potential that can be used as a practical selection tool at production nucleus/multiplication level.