59 No synergistic effect of supplementary lysine in late gestation and domperidone in lactation for sow milk yield.

Abstract This project aimed to determine if providing supplementary lysine (Lys) to gilts in late-gestation and increasing prolactin concentrations in lactation can act synergistically to stimulate milk yield. On day 85 of gestation, gilts were divided in three groups: 1) fed standardized ileal digestible (SID) Lys at estimated requirement (CTL, control, 19.3 g/d SID Lys, n = 23) until day 111 of gestation, 2) fed SID Lys 34% above requirement via additional soybean meal (HILYS, 25.8 g/d SID Lys, n = 22) until day 111 of gestation, or 3) fed SID Lys 34% above requirement via additional soybean meal until day 111 of gestation and receiving domperidone throughout lactation (LYSDOMP, n = 21). The dopamine receptor antagonist domperidone [0.5 mg/kg body weight (BW)] was injected daily from the day after farrowing until weaning, as an emulsion after resuspension in canola oil, in LYSDOMP sows. During the first 4 d of lactation, LYSDOMP sows were also fed 0.5 mg/kg BW of domperidone, dissolved in 8 mL of table syrup, twice daily. The CTL and HILYS sows acted as sham-treated and received both injections and oral treatment with the vehicles. Litter size was standardized to 12 ± 1 and piglets were weighed on days 1, 7, and 22. Sow feed intake was recorded daily. Blood samples were collected on days 84 and 110 of gestation and days 1, 7, and 21 of lactation to measure prolactin, free fatty acids (FFA), and glucose (gestation only). Sow BW and backfat thickness throughout the study and feed intake in lactation were not affected by treatments (P > 0.10). Mean feed intakes across treatments were 3.99, 5.82, and 6.72 kg/d (SEM = 0.11) for weeks 1, 2, and 3 of lactation, respectively. Prolactin concentrations were increased in LYSDOMP compared with CTL and HILYS sows on days 7 and 21 (P < 0.001), being 15.0, 13.6, and 24.3 ng/mL in CTL, HILYS and LYSDOMP sows, respectively, on day 21. Treatments did not alter glucose or FFA concentrations at any timepoint (P > 0.05). Estimated milk yield (mean over lactation of 12.59, 12.73 and 12.24 ± 0.20 kg/d for CTL, HILYS and LYSDOMP sows, respectively) or piglet growth rate were not affected by treatments (P > 0.10). In conclusion, there was no synergistic effect on milk yield of increasing prolactin concentrations during lactation, via domperidone, in sows that were fed supplementary Lys in late gestation, but this was because neither treatment alone had an impact on lactation performance.