Variability in the expression of maternal behaviour in primiparous sheep: Effects of genotype and litter size

Abstract

The effects of ewe genotype and litter size on the expression of maternal behaviour in primiparous sheep were investigated using a lowland breed selected for growth (Suffolk) and a less-selected hill breed of sheep (Scottish Blackface). Focal animal observations were carried out on 58 Blackface (37 singles and 21 twins) and 57 Suffolk ewes (20 singles and 37 twins) during the 2 h after the birth of each lamb. Overall labour was shorter for Blackface ewes compared to Suffolk ewes (62 vs. 84 min, respectively, P<0.05), and shorter for first-born twin lambs compared to singletons. Lambing assistance was required by significantly more Suffolk ewes (25.4%) than Blackface ewes (10.8%, P=0.05) and more by single lambs than twins. Although some aspects of negative maternal behaviour were shown by both breeds of primiparous ewe, Suffolk ewes were more likely to abandon a lamb ( P=0.063), and were significantly more likely to be aggressive towards their lamb ( P<0.05) and to withdraw from the lamb ( P<0.01). Increased exposure to the lamb led to a reduction in negative maternal behaviour in both breeds. Blackface ewes devoted significantly more time to grooming their lambs in the immediate postnatal period (first 2 h after the birth of a lamb) spending 81% of the first 30 min grooming compared to only 47% in Suffolks ( P<0.001). Twin lambs received less grooming attention than singles, and second-born twin lambs received only 65% of the grooming of first-born twins. Blackface lambs were more active than Suffolk lambs in all aspects of their behaviour and made significantly more sucking attempts in the recording period ( P<0.001). Blackface ewes displayed more cooperative behaviour to lamb sucking attempts than Suffolk ewes (standing for 19.49% of sucking attempts in the first 30 min vs. 1.92% in Suffolks; P<0.001). This resulted in significantly more Blackface lambs sucking unaided compared to Suffolk lambs (72.2% vs. 36.7% for Blackface and Suffolk lambs, respectively, P<0.001). Significantly more Suffolk lambs died in the postnatal period than Blackface lambs (8.4% of lambs vs. 1.1%, P<0.05). This study has demonstrated that significant genotype differences exist between breeds of sheep in many aspects of both maternal and neonate behaviour and these may compromise the survivability of the lamb. It is suggested that a high level of selection for growth characteristics alone may lead to a deterioration in maternal ability unless these behaviours are specifically included in selection programmes.