Determination of Sid Val:Lys Requirements in Lactating Sows

A total of 990 sows (PIC Camborough; avg parity = 2.92) were utilized to determine the SID Val:Lys requirement in lactating sows. Upon placement in farrowing, sows were randomly allotted by parity and BW into one of six dietary treatments (0.58, 0.65, 0.72, 0.79, 0.86, or 0.93 SID Val:Lys; 103 to 107 sows/trt) within a randomized complete block design. Diets were corn-SBM based diets with 2.5% added soy oil (3,294 kcal/kg). Single production batch SBM was obtained, analyzed for nutrient content, and used as the only SBM source for the entirety of the trial. Soybean meal inclusion rate was held constant across all treatments at 14.6%. Diets utilized crystalline Lys, Thr, Met, Trp, and Ile in order to target 59 g/d intake of SID Lys, while maintaining all other SID AA:Lys at 10% above NRC (2012) requirements. Crystalline Val was allowed into the diets to obtain the targeted SID Val:Lys levels. Once farrowed, sows were allowed ad lib access to their respective dietary treatment with feed deliveries recorded daily. Average lactation length during the trial was 19.1 days. Statistical analysis to identify effects of dietary treatment were performed using the MIXED procedure of SAS with the main effects of Val:Lys level, sow parity, and the potential interaction thereof. For break-point analysis, the NLMIXED procedure of SAS was utilized for linear broken-line regression. A quartic effect was observed for ADFI (6.47, 6.00, 6.19, 6.53, 6.14, and 6.29 kg/d, respectively; SEM = 0.32; P < 0.014) and sow BW loss (23.1, 28.7, 24.7, 20.6, 23.7, and 24.7 kg, respectively; SEM = 2.09; P < 0.015). A linear response (P < 0.006) in piglet weaning weight was observed when SID Val:Lys was increased from 0.58 to 0.65 (5.65, 5.82, 5.85, 5.83, 5.77, and 5.83 kg, respectively; SEM = 0.05). There was no further increase in weaning weight with SID Val:Lys greater than 0.65. Dietary SID Val:Lys had no impact (P > 0.05) on pre-wean mortality or sow wean-to-estrus length. Based upon this data, a SID Val:Lys levels as low as 0.65 can be fed without negatively impacting sow or piglet performance.