Segregation of single and twin bearing ewes : effects on ewe and lamb behaviour

Abstract

Animal Production in Australia 1998 Vol. 22 SEGREGATION OF SINGLE AND TWIN BEARING EWES: EFFECTS ON EWE AND LAMB BEHAVIOUR M.J. GAMBLEY and G.N. HINCH Department of Animal Science, University of New England, Armidale, NSW 2351 The nutritional requirements of single and twin bearing ewes are markedly different in late pregnancy and consequently the separation of these groups in late pregnancy may be useful, particularly when supplementary feeding is necessary. However, little is known about the effect of such segregation on the behaviour of the ewe or the neonate nor the possibility of an increased incidence of miss-mothering of twins. This experiment examined the behaviour of Merino ewes and their lambs after segregation into management groups according to litter size. One hundred multiparous Merino ewes at pasture which had conceived to a synchronised oestrus were used. The ewes were ultrasound-scanned at 70 days of pregnancy, and at 105 days were allocated to three treatment groups according to litter size and condition score: single lambs only, twin lambs only, and an unsegregated control group. All groups were supplementary fed in late pregnancy and during the neonatal period with 120 g/hd/day of a cottonseed based pellet. The three groups were segregated two days prior to expected lambing into small paddocks (well sheltered with trees and tussock grasses) at a stocking rate of 40 ewes per ha. Records of ewe and lamb behaviours were made within two hours of birth and included: the distance between ewe and lamb, the distance between the ewe and other ewes, a maternal score at tagging (OConner et al.1985), the time taken for the ewe to return to her lamb/s after tagging, the distance between lambs, a lamb vigour score and birth weight. A subset of lambs were also tested in a pen test 4 to 10 hours after birth to determine their ability to recognise their mother. Statistical analysis was completed on transformed data using generalised linear models. In the pen test the twin pairs of the control group took longer than the segregated twins (P<0.1, 147 � vs 82 � 22 sec) to reach their dam. Overall maternal score for ewes with single lambs was better than those with twins (P<0.11) but lamb vigour scores were not significantly different between litter sizes nor management groups (Table 1). Likewise there were no significant differences between management treatments for the other behavioural measurements recorded. Table 1. Mean behavioural scores, distances and lamb bir th weight and mor tality in single and twin bearing ewes Unsegregated Behaviour Maternal score (/5) Distance to nearest ewe (m) Distance to second lamb (m) Lamb vigour score (max. 20)* Birth weight (kg) Lamb mortality (%) Single 3.15 1.8 12.6 3.2 7.7 (1/13) Tw i n 2.8 2.1 1.3 13.8 2.6 29.2 (7/24) Single 3.25 1.8 12.9 3.4 6.7 (1/15) Segregated Tw i n 2.75 2.0 2.5 14.1 2.5 29.2 (7/24) s.e. 0.3 0.2 0.14 0.4 0.1 * Incorporating score out of 5 for each of : vigour during tagging, rate of return to dam, suckling attempts on return to the dam, and willingness to follow the dam These data indicate that even at very high stocking rates there appears to be no advantage to maternal behaviour and ewe-lamb bond of segregation of single and twin bearing multiparous ewes. However, further studies are needed to confirm this finding for primparious ewes and in environments where less shelter is available. OCONNER, C.E., JAY, N.P., NICOL, A.M. and BEATSON, P.R. (1985). Proc. NZ Soc. Anim.Prod. 45, 159-162. 287