Ewe-lamb bond at birth and during lactation in an equatorial semi-arid environment is better in a native than in an introduced breed

Abstract

Santa Ines and Dorper sheep are the most popular breeds in the Brazilian semi-arid region. The former is of local origin and less intensively selected for productivity, and the latter is an introduced exotic breed selected for meat production. Dorper lambs are heavier at birth than Santa Ines lambs, which might increase the need for birth assistance, negatively influencing the newborn and maternal behaviours. Dorper lambs grow faster, most likely influencing their behavioural strategies during lactation, depending less on their mother than Santa Ines lambs. The aim of this study was to compare the behaviours of Santa Ines and Dorper ewes and their lambs at birth and throughout lactation. A complementary aim was to determine if being single or twin lambs impact differently according to the breed. Twenty-five Santa Ines ewes and their 32 lambs (18 single and 14 twins) and 21 Dorper ewes and their 26 lambs (16 single and 10 twins) were used in the study. Mother-offspring behaviours were recorded from birth until 63 days after lambing. Dorper ewes had a greater incidence of dystocia (P = 0.02) and longer labour (P = 0.0001) than Santa Ines ewes. At birth, Santa Ines ewes displayed a greater frequency of low-pitched bleats (P = 0.0006) and tended to spend more time grooming their lambs than Dorper ewes (P = 0.07). Immediately after birth, Santa Ines lambs shook their head earlier than Dorper lambs (P = 0.003). The litter size effects were unrelated to the breed: ewes of single deliveries groomed their lambs earlier (P = 0.04), and those that delivered twins spent more time grooming the first lamb delivered (P = 0.01). Over the first two weeks after parturition, Santa Ines ewes displayed higher frequencies of head-up postures (P = 0.0001), high-pitched bleats (P = 0.02) and smelled their lambs more times (P = 0.0001) than Dorper ewes. Santa Ines lambs were closer to their mother when grazing (P = 0.0001), while Dorper lambs were closer to their mother when lying down (P = 0.049). In conclusion, Santa Ines sheep shows a stronger ewe-lamb bond than Dorper soon after parturition, and such differences persist at least until 9 weeks after lambing. The ewe-lamb bond was weaker in twin than single lambs, without differences in the degree of its strength between Santa Ines and Dorper sheep.