Duration of phase II of labour negatively affects maternal behaviour and lamb viability in wool-type primiparous ewes under extensive rearing

Abstract

This study determined to what extent the duration of labour phase II under extensive rearing would affect lamb viability and maternal behaviour in primiparous (P) single-bearing Corriedale ewes (n = 63). Multiparous (M) ewes (n = 116) were used as control category, reared under the same conditions. Duration of labour was divided in 4 time-groups, G1: ≤ 30 min; G2: 31 –60 min; G3: 61–90 min and G4: ≥ 90 min for each ewe category. Body condition score (BCS, scale 0−5), duration of labour, delivery assistance, maternal behaviour score (MBS, 1−5) and presence of grooming after parturition were recorded and length of gestation calculated. Lambs were Apgar tested (score 1–10) at birth; time elapsed to stand and successful suckling during the first two hours of birth was recorded as well as birthweight (BW) and mortality during their first 72 h. Prepartum BCS was similar between categories, while P ewes showed shorter gestation (147.2 ± 0.3 vs. 148.0 ± 0.2 days, P = 0.0474), longer expulsion phase (50.5 ± 4.2 vs. 32.2 ± 2.6 min, P < 0.0001) and required more delivery assistance (22.2 % vs. 11.2 %, P = 0.0496) than M ewes, with the highest percentage of assisted labours registered in G4 for both categories. Lambs born from P ewes were lighter than M-born lambs (5.3 ± 0.1 vs. 5.8 ± 0.1 kg, P < 0.0001) and BW and duration of labour had a significant correlation within each category. Apgar was similar between categories but among P ewes was lower when duration of labour was longer. Extended labour in P ewes had a negative influence on the percentage of lambs that sucked within 2 h of birth (G1 = 95.5 %, G2 = 91.3 %, G3 = 75 % and G4 = 30 %), but not in lambs born to M ewes. Between categories MBS was different (3.6 ± 0.2 vs. 4.7 ± 0.1 for P and M respectively) being lower in P ewes of G3 (2.9 ± 0.3) and G4 (1.3 ± 0.2). Grooming was observed in 100 % of M ewes but not in 20.6 % of P ewes. Lamb mortality was greater in P than in M ewes (12.7 % vs 1.7 %) with 75 % of the deaths registered within lambs born to primiparous when duration of labour was longer. It is concluded that in conditions of extensive breeding extended labour has a negative influence on lamb survival as well as on maternal behaviour in primiparous ewes. Birth control and perhaps a higher degree of assistance during phase II of parturition in primiparous becomes relevant to prevent ewe desertion and lamb mortality.