By Crystal Levesque, South Dakota State University Department of Animal Science; Emily Miller and C.F.M. (Kees) de Lange, University of Guelph Department of Animal Biosciences; and Nathalie Trottier, Michigan State University Department of Animal Science
Unlike finishing pigs who exit the barn at market weight in a single turn through the barn, sows are expected to remain productive in the herd over multiple parities; thus, understanding the impact of parity is important to ensure optimal nutrient supply through the reproductive life of the sow.
While many acknowledge the need to adjust dietary supply based on parity, few production systems actually do. There are numerous reasons for this. One critical limitation to practical implementation of parity feeding is the lack of understanding of the full impact of parity on nutrient requirements. Previously we reported the pattern of whole body, maternal- and pregnancy-associated protein deposition in gilts and determined that the pattern of protein retention was not impacted by energy intake (15% below or above requirement) while low energy intake resulted in lower overall protein retention.
However, when separated into maternal- and pregnancy-associated pools, maternal protein retention was reduce in late-gestation indicating an energy independent regulation of maternal protein deposition in gilts. The implication for gilts is that amino acid requirements and ideal amino acid ratio estimates in late-gestation may need to be revised to reflect a greater contribution of fetal tissue to the whole body amino acid requirement. As a follow-up study, the same gilts were followed through the second and third parity and the pattern of whole body, maternal- and pregnancy-associated nitrogen retention was again determined (for additional details see Miller et al., 2017; JAS doi:10.2527/jas.2017.1444).
After completion of their first lactation cycle, sows were reassigned to one of the two feeding levels used in the gilt study [15% below and above NRC (2012) energy intake recommendations of a corn soybean-based diet (3.30 megacalories metabolizable energy per kilogram; 0.82% standardized ileal digestible lysine) at Day 33 ± 0.5 of gestation] and fed through Day 110 of gestation. Nitrogen balance collections [Nitrogen intake – nitrogen output in urine and feces = nitrogen balance (retained or lost)] were conducted at Day 38, 52, 66, 87 and 108 ± 0.5 of gestation and the pattern of whole body protein retention (Nitrogen retention x 6.25) was characterized.
Whole body retention was then separated into that associated with pregnancy, based on NRC (2012) equations which account for day of gestation, and that with maternal tissue. At Day 111 sows were moved to the farrowing room and provided a lactation diet until weaning. Lactation feed allowance followed a step-up program from farrowing such that ad libitum intake was expected by Day 4 of lactation. Sows were reallocated to a feeding level for the third gestation as above.
Whole body protein retention increased (P < 0.01) quadratically throughout gestation, was greater (P < 0.01) in sows on the high feeding level by approximately 30 grams per day and greater in Parity 3 sows. Maternal protein retention did not differ with day of gestation regardless of parity and was greater (P < 0.01) in Parity 3 sows at Day 52 and 87 of gestation. Pregnancy-associated Pd was not affected by feeding level nor parity and increased (P < 0.001) with progressing gestation. Estimated efficiency of lysine use for whole body protein deposition increased quadratically (P = 0.03) with progressing gestation.
This study demonstrated that while the pattern of whole body protein retention was similar across all parities (i.e. increase in a quadratic pattern with progressing pregnancy), the pattern of maternal protein retention is parity dependent. The absence of a drop in late-gestation maternal protein retention in Parity 2 and 3 sows suggests a lesser influence of fetal-maternal competition for nutrients in late-gestation. This control mechanism driving nutrition partitioning between fetal and maternal tissue in late-gestation may play a lesser role in multi- versus primi-parous sows.
The patterns of maternal protein retention for gilts and Parity 2 and 3 sows suggests that maternal contribution to overall amino acid requirements in gestation may be lower than previously assumed and dependent on parity. This means that the lack of parity feeding may reduce overall profitability and productivity, result in underdeveloped gilts or excess feed costs for older parity sows. However, refined nutrient requirement in gestation models are necessary to ensure optimal nutrient supply to meet fetal and maternal demands.