Effects of Dietary Lysine Levels on Production Performance and Milk Composition of High-Producing Sows during Lactation

Simple Summary Modern sows need increased nutrient levels to meet their lactation needs with a high litter size. Compared with multiparous sows, primiparous sows need to meet their lactation, growth, and developmental needs. Therefore, ensuring lactation nutrient intake for primiparous sows is important, and it increases the productivity of the entire breeding population. The objective of this experiment was to evaluate the effect of dietary lysine (Lys) levels for lactating primiparous sows on multiple reproductive cycles including piglet performance and milk composition. Results showed that increasing dietary Lys levels in lactation was beneficial for the survival rate of piglets, litter weight, piglet weight, and average daily gain (ADG) at weaning. The dry matter and protein concentrations in milk were increased by the increase in dietary Lys level. Therefore, when implementing strategies for improving reproductive efficiency, increasing the dietary Lys levels during lactation must be considered, especially for primiparous sows. Modern genotype sows require enhanced nutrition because of their larger body size and higher reproductive performance than 20 years ago. This study aimed to evaluate the effect of dietary Lys on the lactating of primiparous sows and the second lactating period to minimize sow body weight (BW) loss and maximize the survival rate of piglets and litter gain. A total of 160 primiparous Yorkshire sows were randomly allotted to one of four experimental lactation diets. Formulated to contain 0.84%, 0.94%, 1.04%, and 1.14% standardized ileal digestibility (SID) Lys and balanced in Met, Thr, Trp, and Val. No dietary effects were found on sow body weight (BW) and backfat thickness (BF) change and feed intake during lactation. However, the Lys intake (p = 0.04) of lactation increased linearly with increasing dietary Lys levels. In addition, 1.14% Lys for primiparous sow and 0.94% Lys for second parity sow during lactation increased the survival rate (p = 0.04), weight (p = 0.04), and ADG of piglets at d 21 (p = 0.03). The dietary Lys level did not affect colostrum compositions. However, the dry matter (p = 0.04) and protein (p = 0.03) in milk increased linearly with the increase in dietary Lys levels, whereas moisture decreased linearly (p = 0.05). The level of plasma urea nitrogen (PUN) also increased at d 21 of weaning (p = 0.04). These results indicate that high-yielding lactating sows required 1.14% SID Lys during parity 1, and 0.94% SID Lys during parity 2 to maximize the survival rate of piglets and litter gain, respectively. Moreover, the effects of dietary amino acid (AA) on the production performance of weaning pigs could be mediated through milk composition change.