Effects of dietary ammonium chloride in late gestation on farrowing performance and piglet survival

• Feeding sows 20 g/d NH4Cl for two weeks pre-farrowing improved blood iCa levels. • Farrowing duration reduced if sows received 20 g/d NH4Cl two weeks pre-farrowing. • Sows fed NH4Cl two weeks pre-farrowing had lower stillbirth rates. High piglet stillbirth rates are a major concern in the modern pig industry. Number of stillbirths are strongly correlated with prolonged farrowing duration and are more common in older sows. The effects of dietary ammonium chloride (NH 4 Cl) supplementation in older sows during late gestation on blood ionised calcium (iCa) concentration, farrowing duration and piglet survival were investigated in this study. From day 101.1 ± 0.1 of gestation until entry to the farrowing house, 72 (Landrace × Large White) sows, parity ≥ 4, were assigned equally into two groups. Control sows were fed a basal diet whereas Treatment sows received the basal diet supplemented with 20 g/day NH 4 Cl until farrowing. Urine and blood pH, bicarbonate concentrations (HCO₃⁻) and base excess of the extracellular fluid (BE.ecf) in the Treatment sows were lower compared to the Control sows (P < 0.05), while blood ionised Ca concentrations in the Treatment sows were higher than in the Control sows (1.34 ± 0.01 mmol/L vs 1.28 ± 0.01 mmol/L, P = 0.002). Notably, the average farrowing duration of the Treatment sows was shorter than of the Control sows (288.8 ± 22.5 min vs 384.4 ± 27.4 min, P = 0.007). Additionally, the stillbirth rate in the Treatment was lower than the Control group (4.80% vs 9.33%, P = 0.02). These results demonstrated that providing 20 g/day NH 4 Cl in the diet of older sows for 2-weeks before farrowing improved the blood ionised Ca levels and reduced farrowing duration and stillbirth rates.