The Dietary Inclusion of Magnesium Sulfate During Late Gestation Enhances Lambing Performance Without Compromising Neonatal Physiology or Behavior in Twin-Bearing Ewes

This study evaluated the effects of dietary magnesium sulfate (MgSO4) addition in twin-bearing ewes during late gestation on the duration of lambing, neonatal behavior, and blood biochemical variables. Fifty-one hogget and 54 adult Finnish × Polwarth ewes were allocated to four groups based on age category (hogget or adult) and dietary addition (MgSO4 addition or control). Ewes in dietary MgSO4 treatments received 7 g of MgSO4/ewe/day. Duration of the expulsion phase (DII), interval between lamb births (IL), and total lambing time (TL) were recorded. Meconium score (0–3), birth weight, time to stand (TS), time to first successful suck (SS), and rectal temperature at birth (T0) and at 3 h of life (T3) were measured. Blood samples were collected from lambs and analyzed for blood biochemical and acid–base variables. MgSO4 addition did not affect individual or litter birth weight (p > 0.05), but the DII was lower in the lambs from MgSO4 ewes (p < 0.05). A greater proportion of lambs born to dietary MgSO4 ewes had higher meconium scores. The treatment did not affect the acid–base variables (p > 0.05); however, the age category had an effect on BEecf, HCO3−, tCO2, lactate and glucose, and behavior variables (p < 0.05). Acidosis (pH < 7.20) occurred in lambs from control ewes. No differences were observed in T0, but lambs from control hoggets had lower T3 values (p < 0.05). In conclusion, in our conditions, dietary MgSO4 addition in twin-bearing ewes during late gestation reduced the duration of the expulsion phase without affecting neonatal behavior or the main indicators of neonatal acid–base status. Further studies are needed to elucidate the mechanisms by which MgSO4 influences the lambing process.