Including magnesium sulfate in the diet of twin-bearing ewes in the last week of gestation improves the adaptation of lambs to extrauterine life

Abstract

Context Most deaths of lambs in the first days of life are due to failure to adapt to extrauterine life. Aims This study aimed to test the hypothesis that adding magnesium sulfate (MgSO4) to the diet of twin-bearing ewes in the last week of gestation improves the adaptation to the extrauterine life of the lambs. Methods Eighty-three multiparous Finnish × Polwarth ewes carrying twins in the last week of gestation were MgSO4 supplemented (n = 40) or allocated to control (n = 43). We recorded the durations of gestation, expulsion and lambing, interlambing interval, and birthweights, meconium score, lamb rectal temperature (at birth and 3 h after birth), whether assistance was needed (yes or no) and time from lamb expulsion to stand and to suck (n = 148). A jugular blood sample of the lambs was analysed for acidity, partial pressures of CO2 and oxygen; active and standard HCO3, blood base excess (BE b) and extracellular fluid base excess (BE ecf), saturated oxygen, and total CO2 concentration. Glucose was analysed with a portable device. Key results Gestation was longer in supplemented ewes (147.7 ± 2.0 vs control: 146.7 ± 1.7 days, P < 0.05). Birthweight and litter birthweight of lambs were higher when ewes were supplemented (3.74 ± 0.6 and 7.47 ± 0.9 kg vs control: 3.51 ± 0.5 and 7.02 ± 0.9 kg, P < 0.05). The need for assistance, meconium score, durations of expulsion and lambing, and time to stand and to suck were not different between treatments (P > 0.05). The interlambing interval was shorter in the supplemented ewes (6.7 ± 2.7 m vs control: 10.4 ± 2.6, P < 0.05). Lamb rectal temperature was not different between treatments 3 h after birth, but at birth was lower in lambs of supplemented ewes (P < 0.05). Treatments did not differ in blood acidity, CO2 partial pressure and total concentration, active and standard HCO3, both measures of base excess, nor blood glucose. Lambs of supplemented ewes had higher oxygen saturation and partial pressure (P < 0.05). Conclusions The MgSO4 supplementation improves the adaptation to extrauterine life in pen conditions. Implications It should be tested whether maternal supplementation with MgSO4 reduces the mortality of twin lambs.