G Alexander

Maternal behaviour in Border Leicester, Glen Vale (Border Leicester derived) and Merino sheep

Ewe and lamb behaviour in traditional Border Leicesters, Glen Vale Border Leicesters of the NSW Agriculture and Fisheries, Glen Vale x Border Leicester crosses and medium-fine-wool Merinos, all running in paddocks of 3-4.5 ha, were compared in spring 1983 at Glen Innes, N.S.W. Twenty-eight aspects of behaviour with a known or reputed influence on lamb survival, especially of multiples, were examined in undisturbed and contrived situations. The Glen Vales and their crosses were superior to the Border Leicesters and Merinos in behaviour and lamb survival, particularly behaviour concerned with the ability of ewes to keep their lambs together. The study indicates that contrived twin-care tests could form the basis of a selection program to improve maternal care and survival of multiples.

Distribution of field birth-sites of lambing ewes

This paper reports on birth-site distribution of Merinos and some British breeds in 34 lambing paddocks in a major study over 5 lambing seasons at Armidale New South Wales, and in minor studies during single lambing seasons, 2 in New South Wales and 3 in the United Kingdom. The observed distribution of birth-sites is related to topographic and other environmental features of the paddocks. In level, or nearly level paddocks, Merinos tended to lamb in a random pattern, but in sloping paddocks their birth-sites were consistently aggregated in the areas of greatest elevation. British breeds (Suffolks and Cheviots in New South Wales, and Welsh Mountain, Scottish Blackface, North Country Cheviots and Greyface in the United Kingdom) showed a pronounced tendency to lamb near the margins of paddocks, and a less marked preference for an elevated site. It is suggested that lamb mortality could be significantly reduced by the use of paddocks that provide shelter at preferred elevated positions, or along and within the paddock margins.

Maternal acceptance of alien lambs in ewes treated and untreated with oestrogen at birth

Sixteen ewes suckling their own lambs and 20 ewes from which lambs had been removed at birth were tested on 7 occasions, between 1 and 48 h postpartum, for their maternal interest in their own lamb, an alien lamb of similar age, a newborn alien, a ewe-fed older alien and an artificially fed older alien. Half of the ewes under each treatment were given 20 mg 17β-oestradiol benzoate, intramuscularly just prior to parturition, plus 5 mg 17β-oestradiol intravenously at the same time and at 2, 4 and 6 h postpartum. Oestrogen treatment of ewes whose lambs had been removed at birth, produced a small but significant improvement in the number of acceptances of own lambs and alien lambs of similar age and treatment. There were small non-significant trends in the same directions with the other 3 classes of lamb in both groups of ewes. It appears that oestrogen treatment of parturient ewes has only marginal effects on maternal interest and would be of little value in facilitating fostering. Ewes kept from their own lambs accepted alien lambs much more frequently than did ewes left with their own lambs. Hence, limited exposure of newly lambed ewes to lambs may be useful in facilitating fostering by sustaining maternal receptivity but delaying discrimination between lambs. Artificially fed alien lambs, kept from ewes except at testing, were more frequently accepted than alien lambs of a similar age kept with their dams. Thus maternal recognition of lambs as aliens may be facilitated by maternal labelling, and fostering is more likely to be successful if the foster lamb has been isolated and artificially fed, than if left with its dam.

The timing of birth in grazing Merino sheep

During a 5-year study of lambing behaviour involving almost 1900 births by grazing ewes, the incidence of lambing peaked during the 5-h period 0900-1400 hours, when 28% of ewes lambed. Significant numbers of births occurred throughout the day, and so effective supervision of lambing would not be possible if attendance was restricted to daylight hours. The birth process was clearly delayed when the unlambed sheep were moved slowly from 1 paddock to another. The apparent tendency for ewes to lamb in clusters was shown to be largely the outcome of the exponential distribution expected for the intervals between consecutive, randomly occurring events, but a small significant excess of short intervals above those expected indicates that environmental factors may operate in the synchronous triggering of parturition.