Reduction of perinatal loss of lambs in winter in western Victoria by lambing in sheltered individual pens.

Abstract

REDUCTION OF PERINATAL LOSS OF LAMBS IN WINTER IN WESTERN VICTORIA BY LAMBING IN SHELTERED INDIVIDUAL PENS R. H. WATSON*, G. ALEXANDER, I. A. CUMMING*, J. W. MacDONALD*, J. W. MCLAUGHLIN*, D. J. RIZZOLI* and D. WILLIAMS Summary A flock of Corriedale ewes in western Victoria was divided into two groups immediately before lambing in August 1966. One group (Exposed) lambed in exposed paddocks and the lambs were not given any special attention; the other group (Sheltered) was provided with shelter and care during lambing. In the Exposed Group many more lambs died between birth and 48 h of age than in the Sheltered Group. Most of the deaths occurred in one spell of cold, wet and windy weather of 39 h duration. In the Exposed but not in the Sheltered Group, a number of ewes became interested in and interfered with the lambs of other ewes, and a high proportion of the twin lambs involved subsequently died; other lambs were abandoned. Half of the lambs which died within 48 h after birth in the Exposed Group had no evidence of milk in the gut at autopsy. Most of these lambs (21 of the 26) were born during the severe weather. Few lambs in the Sheltered Group failed to obtain milk. It is considered that the lower level of loss in the Sheltered Group was due to shelter from severe weather, together with elimination of mismothering and facilitation of sucking by close confinement and active assistance. I. INTRODUCTION In western Victoria, highest fecundity may be achieved by mating in March with a subsequent August lambing (Radford 1959; Watson and Elder 1961). However, in this area, the weather in August is usually very cold, wet and windy and losses may be very high particularly among multiple lambs (Alexander, Peterson and Watson 1959; Watson and Elder 1961). Alexander, Peterson and Watson (1959) demonstrated that losses could be virtually eliminated by providing lambs with warmth and food from birth. Lambing in individual pens is practicable commercially under autumn conditions in southern Victoria. (Beggs and Campion 1966). The present paper describes observations made to determine the effectiveness and practicability of lambing in individual pens in complete shelter under winter conditions in western Victoria. II. MATERIALS AND METHODS (a) Animals and sites of observation The observations were made on Corriedale ewes, 5-6' years old, from the flock studied by Alexander, Peterson and Watson (1959) and Watson and Elder (1961) and the same site was used as in the latter observations. All ewes had mated to Corriedale rams between March 7 and March 16, 1966 and had not *Department of Agriculture, Victoria. -i-Division of Animal Physiology, CSIRO, Prospect, N.S.W. 243 returned to service during the following three weeks. Mating was recorded daily (Radford, Watson and Wood, 1960). The pastures consisted predominantly of perennial ryegrass #(LoZium perenne) and Mt. Barker subterranean clover (Trifolium sub terraneum). Commercial pelleted feed was offered as a supplement from early July, and the ewes were accustomed to the presence of observers. Thirty ewes selected at random were weighed direct from pasture on June 29, July 18 and July 29, 1966. The mean liveweight of these ewes increased progressively. Ewes that had mated on each day were listed in order of liveweight on June 29, 1966 and the members of each pair in sequence were allotted at random to two groups.. They were separated into their groups in two lots, those which had mated during the first five days on August 1, the remainder on August 8. Detailed observations were made during the period 3 to 17 August. All births and deaths were recorded and all lambs that died were autopsied. (b) Treatment of groups All ewes, whether in observation paddocks, yards or pens, were offered pelletted feed daily and were provided with water ad libitum. The feed and water were provided in the pens only when ewes had lambed. (i) Exposed Group During lambing, the ewes were moved around three paddocks each of 1.6 ha (4 ac) all completely exposed to the prevailing weather and to winds from all directions (Figure 1). One paddock was illuminated at night and the ewes and their newborn lambs were observed continuously until the lambs were at least 48 h old. No assistance was given to the ewes or lambs. During daylight, the lambing ewes were run in a 1.6 ha paddock (Figure 1). Any ewes which lambed and, each evening, any ewes considered likely to lamb overnight, were transferred into individual pens completely sheltered from wind and rain in a marquee (Figure 1). The 32 individual pens, 1.3 x 1.0 m, and two areas of 6 x 2.5 m each used for several animals, were illuminated. The bedding of oaten hay was replaced when soiled; lime was sprinkled liberally over the ground before fresh hay was spread. The ewes were inspected at 1900, 2 100 and 2300 h and each morning those which had not lambed were returned to the 'day' paddock. In a few cases lambs were warmed and assisted in suckling. Ewes and lambs were kept in the marquee when the weather was inclement. Otherwise when mothered satisfactorily, although some lambs had not gained in weight, ewes and single lambs were transferred to a 1.6 ha paddock; ewes and twin lambs were transferred for a few days to small yards (15 m square) almost completely sheltered by shrubs and trees from wind but waterlogged and muddy in wet weather, and thence to a 1.6 ha paddock. All three 1.6 ha paddocks had some shelter from winds from the north and west (Figure 1). Ewes and lambs were always moved quietly with minimal disturbance. When observations were discontinued, all ewes and lambs were brought together in a large exposed paddock. This paddock was inspected daily and any dead lambs collected. A final check was made of the ewes and lambs present on September 2, 1966. 244 (ii) Sheltered Group (c) Weather recurds Continuous observations wefe made on wind direction and speed, rainfall, sunshine, temperature and humidity at one site in the exposed area and on wind direction and speed, temperature and humidity at one site in the sheltered area; daily wind travel was recorded at one site in each paddock. 245 Weather, and distribution of births throughout observations TABLE 1 III. RESULTS During the 312 h period of observations, considered in seven periods (Table l), the weather varied from fine and sunny with variable winds, through fine and overcast, mild and sunny with some rain overnight, to cold, wet and very windy for 39 h in period 5, and then gradually eased to fine and sunny. In the Exposed and Sheltered Groups respectively, 134 and 132 ewes lambed during the period of the observation, of which from 7 to 29 and 13 to 30 respectively lambed in the different weather periods (Table 1). Of the births, 37 in the Exposed Group and 31 in the Sheltered Group were twin. The proportion of the twin births that occurred in weather period 5 was significantly higher in the Exposed than in the Sheltered Group (0.01 <P <O.OS). Eighty-two of the ewes in the Sheltered `Group, lambed in the pens, 42 in the paddock during the daytime and 8, all single births, in the paddock at night. Two of the singles born in the paddock at night were released direct to the 'singles' paddock, but all other ewes and lambs of this group were taken into the marquee for some time. Three quarters of the singles and about half of the twins were 246 (a) Weather (b) Lambing in the marquee for less than 24 h. Most of the other twins remained in the marquee for more than 30 h, a few as long as 2% days. The mean age at release of single and twin lambs respectively was 18.4 and 30.3 h (excluding the two singles released direct to the 'singles' paddock and lambs which died in the marquee). Mean birth weight of the single lambs in the Exposed Group was 4.90 -+ 0.04 ,kg and in the Sheltered Group 4.85 t- 0.07 kg; that of the twin lambs was 4.08 -+ 0.09 kg and 3.90 -t- 0.09 kg respectively. In the Exposed Group, 2 1% of the singles, 58 % of the twins and the one set `of triplets died before Sleptember 2, 1966 (Table 2). Losses to this date in the Sheltered Group were much lower, 8 % of the singles and 24% of the twins (difference between groups P<O.OOl for both singles and twins). The incidence of deaths before and during birth and after 48 h of age was much the same in both groups but in the Exposed Group many more died between birth and 48 h of age than in the Sheltered Group (P<O.OOl for both singles and twins). *of the lambs which died in the Sheltered Group, 7 of 8 singles and 11 of 15 twins died after release from the lambing pens. Most of the deaths after birth occurred in the severe weather of period 5 two thirds of those in the Exposed Group, and two fifths of those in the Sheltered Group (Table 3). Almost all (36/43) of the lambs that died during this weather period in the Exposed Group were less than 48 h old, whereas almost all in the Sheltered Group (8/9) were more than 48 h old (age difference between groups significant at P<O.OOl). Mortality in any of the other weather periods was never greater than five lambs in the Exposed Group and three lambs in the Sheltered Group. In the Exposed Group, 13 ewes became interested in the lambs of other ewes, 2 after their own lambs had died. Five of these ewes and their lambs were themselves interfered with by other ewes. Another 10 ewes and their lambs were interfered with by other ewes but did not themselves interfere. In all, 2 of 11 singles and 13 of 18 twins died after and perhaps because of the interference. A Mortality of lambs in relation to age at death TABLE 2 (c) Deaths 247 TABLE 3 further 4 ewes abandoned lambs (1 single, 4 twins) all of which died. In the Sheltered Group there was no interference or abandonment of lambs. In all, 23 of the 50 single and twin lambs that died within 48 h of birth in the Exposed Group had evidence of milk in the gut at autopsy. Twenty two of the other 27 of these 50 lambs were born during weather period 5. In the Sheltered Group, only 6 lambs failed to obtain milk; 5 of these died within an hour after birth. The mean age at release from the marquee of the single lambs (Sheltered Group) which died after release, 25.4 * 3.4 h, was greater than that of those which survived, 17.8 -t 0.9 h. On the other hand, the mean age at release of the twin lambs which died after release, 22.8 f- 2.1 h, was less than that of the twins which survived, 30.9 t- 2.1 h. Evidence of infection was observed at autopsy in four lambs, two in the Exposed Group (1 enterotoxaemia; 1 staphylococcal arthritis) and two in the Sheltered Group (1 navel abscess; 1 mixed ear infection after ear tagging). IV. DISCUSSION Since the ewes of the two groups were from one flock and grazed together until a week before lambing, the difference in mortality between groups must have been a consequence of the difference in treatment following their separation for lambing. An inadvertent nutritional disadvatnage in the Exposed Group after separation is unlikely since mean birth weight was higher in this Group than in the Sheltered Group. It is inferred, therefore, that the difference in loss was due to shelter from severe weather provided for the Sheltered Group, together with elimination of mismothering and facilitation of sucking by close confinement and active assistance. If the significant difference in incidence of twin births during the severe weather is real itnmust have been a consequence of reduction in gestation length in ewes of the Exposed Group through stress. Part of the difference in loss may also have arisen from elimination of such stress. The number of individual pens'was high in relation to the number of ewes in the Sheltered Group but no accommodation was available other than that 248 provided by the marquee. Nevetheless, since the twins that died in the Sheltered Group had, in general, spent less time in the marquee than those that survived, and some lambs older than two days died, it may be useful to hold twin lambs in pens for l-2 days longer than in the present observations. To this end it may be necessary to provide a high ratio of pens to lambing ewes where complete shelter from severe weather is sought. Most of the loss in the Exposed Group occurred during one short spell of severe weather, and it may be difficult to reduce such mortality except by bringing ewes into shelter at night as a routine. The severe weather in this instance was not expected by the observers; it started about midnight and much of the loss had occurred before day-break. Absence of any difficulty in operation together with reduction in mortality by lambing in complete shelter with ewes and lambs in individual pens suggest strongly that such a system is practicable. It has no greater labour component than the system described by Beggs and Campion (1966) but may require more capital investment. Economic evaluation still requires information on such features as the area of complete shelter needed, the ratio of individual pens to the number of ewes likely to lamb daily, conditions under which twin lambs should be released from complete shelter, the degree of shelter into which they should be released, and the feeding and watering of the ewes in the sheltered areas. V. ACKNOWLEDGMENTS The authors are indebted to the owner of the property for so generously making available sheep and facilities, and recording mating, to the State Electricity Commission of Victoria for the lighting facilities, to the Co-operative Studies Group of the Commonwealth Meteorological Bureau for loan of the meteorological equipment and to the Australian Wool Board for funds. VI. REFERENCES J. E., and W ATSON , R. H. (1959). Aust7 vet. J. 35: 433. EGGS , A. R., and E. J. (1966). Proc. Aust. Soc. Anim. Prod. 6: 169. R ADFORD, H. M. (1959). Aust. J. agric. Res. 10: 377. R ADFORD , H. M., W ATSON, R. H., and W OOD, G. F. (1960). Aust. vet. J. 36: 57. WATSON, R. H., and ELDER , E. M. (1961). Aust. vet. J. 3'7: 283. A B LEXANDER , G., P ETERSON , CAMPION, 249