Review: Feeding strategies to meet the dynamic lysine and energy requirements of gestating and lactating sows.

Abstract

The nutrient and energy requirements of the sow are dynamic, particularly in late gestation, during the transition period, and throughout lactation. In late gestation, growth of the fetuses and mammary glands occur exponentially resulting in a substantial increase in energy and, to a greater extent, amino acid requirements. The fetal pool has received the most attention with respect to estimating nutrient requirements in late gestation, but subsequent milk production is influenced by the mammary development that occurs prior to farrowing, compelling further investigation into late gestation and transition feeding strategies that also maximize mammary development. Recent work has demonstrated that the standardized ileal digestible (SID) lysine intakes in late gestation should be provided between 15 and 19% above currently perceived requirements to optimize piglet birth weight and subsequent milk production for primiparous sows. In lactation, the feeding program can also influence milk production, despite the significant maternal reservoirs of nutrients (amino acids) and energy available to support milk synthesis. The interplay between feed (energy) intake and amino acid (lysine) and energy utilization for milk production, however, complicates the empirical determination of amino acid requirements. Thus, feeding lysine as a ratio to energy is necessary. Moreover, primiparous and multiparous sows appear to respond to inadequate SID lysine-to-net energy (NE) ratios differently, sacrificing maternal nitrogen retention and milk output, respectively. The optimal SID lysine-to-NE ratio is influenced by sow BW and milk production level, both of which are dynamic throughout the lactation period and are impacted by parity and feed intake. Therefore, implementation of dynamic SID lysine-to-NE ratios unique to primiparous and multiparous sows could be considered in order to maximize milk production and piglet growth prior to weaning. Converting to dynamic feeding programs in both gestation and lactation has the potential to maximize productivity (piglet growth and milk production) but also to optimize the apparent utilization efficiency of energy and nutrients for reproduction and reduce nutrient losses to the environment. Practically, the logistical constraints of feed delivery systems and sow flow on-farm must be balanced with the underlying biology of the sow to optimize productivity, in both current and future reproductive cycles.