Abstract:
Proc. Aust. Soc. Anim. Prod. (1972) 9: 365 SOME FACTORS ASSOCIATED WITH THE PERIPARTURIENT BEHAVIOUR OF EWES AND LAMBS INDOORS C. G. WINFIELD*, A. H. WILLIAMS* and A. W. MAKIN* Summary maternal behaviour. The duration of defined stages of parturition was related within flocks to the liveweights and physical dimensions of the individual ewes and lambs. during indoor lambing to provide further information on the factors influencing Two flocks of maiden Border Leicester-Merino cross ewes were observed In one flock, which was in good body condition, significant and positive relationships were found between the duration of labour and some measurements of lamb size. In the other flock, which was in poor body condition, there were no siginficant relationships. Excluding data from assisted ewes, no relationships were found between length of labour and time elapsing before the lamb obtained milk. Assisted ewes had larger lambs, and tended to show abnormal maternal behaviour and desert their lambs more frequently. I. INTRODUCTION The behaviour of the ewe is important to the survival of the new-born lamb (Moule 1954; McHugh and Edwards 1958), and the maternal behaviour of maiden ewes is more likely to be deficient than that of multi-parous ewes (Alexander 1960). Alexander and Peterson (1961) found in a flock of maiden 2-year-old ewes lambed in outdoor yards, that desertion of the lamb was the major single contributor to death. Undernutrition of the ewes contributed towards deficient maternal behaviour and poor lamb vigour. Long labour has been associated with increased deaths after birth, as well as prior to birth, due mostly to prolonged lying after delivery and maternal desertion (Alexander 1960; Shelley 1970). Data collected from two flocks of maiden Border Leicester-Merino cross ewes, which lambed indoors, have been examined to provide further information on the factors which are associated with the duration of labour, and the progress of the lamb to the first sucking. II. MATERIALS AND METHODS (a) Animals and management In two flocks of maiden Border Leicester-Merino cross ewes which were mated with Dorset Horn rams, mating was synchronised by a series of progesterone injections. Those ewes which did not return to service were individually pen fed *Department of Agriculture, S. S. Cameron Laboratory, State Research Farm, Werribee, Victoria, 303 0. indoors during the last 23 months (1969, Flock A) or 33 months (1970, Flock B) of pregnancy. All ewes were fed ad lib. during the last 3 to 4 weeks of pregnancy. The mean liveweight gains during this period were 3.97 t- 1.17 kg and 5.97 t- 3.11 kg in flocks A and B respectively. Each ewe was identified by a coloured side brand when they were released into group pens with slatted floors of about 13 m x 18 m immediately before the flock commenced lambing. Behavioural observations ceased after suckling, and both the ewe and the lamb were removed. (b) Observations During lambing, continuous observations of behaviour were made from an elevated platform in the shed. For each ewe the duration of the various stages of parturition (as indicated in Table 1) was recorded and subjective assessments of maternal behaviour were made. Subnormal maternal behaviour was recorded if, after the lamb was expelled and the ewe had stood, she (i) ignored the lamb (desertion), (ii) did not groom the lamb vigorously and continuously while it attempted to rise (less than normal grooming), (iii) did not stand quietly during the lamb's attempts to reach the udder (less than normal co-operation). Any ewe which had not lambed within 2 hours of the lamb appearing was assisted by the observer. The birth weight and body measurements of each lamb were recorded within 24 hours of birth. Ewes were weighed immediately prior to the commencement of lambing and the height of the withers measured. In Flock B an assessment of individual body condition was also made (Russel, Doney, and Gunn 1969). (c) Statistical procedure Correlation coefficients were calculated for the observations from each flock, omitting data from ewes which were assisted or which deserted their lambs. x2 analysis was carried out on the proportions of ewes showing sub-normal maternal behaviour in relation to duration of birth. A 't' test was used to compare the size measurements of assisted and unassisted lambs. III. RESULTS The mean values of the prepartum time intervals were similar both in magnitude and variance in the two flocks, but the post partum intervals had a greater magnitude and variance in Flock B (Table 1). The two flocks differed appreciably in ewe liveweight prepartum and ewe condition, but little in birth weight and size measurements of the lambs and ewe wither height. The mean birth weights and mean chest circumferences of assisted lambs (A S.D.) which were not included in Table 1 were 4.85 t- 1.2 kg, 4.9 t- 2.6 kg, 37.5 i- 1.3 cm and 37.5 f- 2.9 cm in Flock A and Flock B respectively. These were significantly greater than the values for unassisted ewes (P < 0.05). Table 2 indicates that in Flock A there was a positive correlation between the duration of labour and the size of the lamb. All corresponding correlations in Flock B were not significant, although of similar sign. 366 TABLE 1 Average time intervals during birth and average ewe and lamb body measurements for the two flocks In Flock A the time elapsing between birth and the onset of maternal behaviour was positively correlated with the dimensions and birth weight of the lamb (Table 2) and the time interval between appearance of the lamb and birth (r = + 0.23, P < 0.05). Despite these apparent relationships with the commencement of maternal behaviour, none of these factors appeared to be significantly associated with progress of the lamb to sucking. In between width. smallest Flock B there were significant negative correlations of low magnitude progress of lamb to sucking and both ewe condition score and lamb chest This suggested that ewes which were in the lowest body condition and with lambs tended to take longer to suckle successfully. The correlation coefficients between all other observations which have been omitted from Table 2 were less than 0.27, and only two were significant (P < 0.05). In both flocks there was no difference in the incidence of sub-normal maternal behaviour between those ewes which took longer than average and those which took shorter than average time to give birth without assistance. These two categories were combined and compared with those ewes which were assisted. In Flock A the incidence of less than normal grooming (assisted 9: 5, unassisted 8: 66, x2 = 18.3) and less than normal co-operation (assisted 6: 8, unassisted 9: 65, x2 = 5.8) were significantly higher (P < 0.05) following assistance, although there was not a significantly different incidence of desertion (assisted 367 TABLE 2 2:12, unassisted 3:71, x2 = 0.8). In Flock B the incidence of desertion was significantly higher (P < 0.05) following assistance (assisted 4:3, unassisted 3: 38, 2 X - 8.3), although the incidence of less than normal grooming (assisted 4 : 3, unassisted 10: 3 1, x2 = 1.72) and less than normal co-operation (assisted 4: 3, unassisted 10: 3 1, x2 = 1.72) were not significantly different following assistance. IV. DISCUSSION Since these observations have been made with the ewes closely confined under conditions free from climatic stress, any deficiencies in behaviour are likely to have been of less consequence than outdoors. A comparison of the data from the two flocks confirms the findings of Thomson and Thomson (1949) and Alexander and Peterson (1961) that with under-fed ewes, there is a detrimental effect on the onset of maternal behaviour and the time taken for the lamb to first obtain milk. Also the results suggest that ewes in poor condition at lambing may be more likely to desert their lambs when assistance has been necessary at birth. In Flock A, where the ewes were in generally good condition at lambing, the duration of labour was observed to be positively related to birth weight as was found by Alexander (1960), and also to the dimensions of the lamb. As might be expected the dimensions of the lamb which tended to be more closely related to the duration of labour were those of the shoulders and chest, since these parts of the foetus require the greatest dilation of the cervix in order to be expelled from the uterus. In Flock B there were lower levels of correlation between lamb size and duration of labour than in Flock A. It is possible that this observation is due in part to the smaller number of animals, the different genetic background and the slightly smaller lambs in Flock B, but it is more likely that at the low Iiveweight of Flock B, the strength of the ewe becomes more important. The observations show that there is a positive relationship between lamb size and the commencement of maternal behaviour (grooming the lamb) in Flock A, probably through the relationship between lamb size and duration of labour. Alexander (1960) and Shelley (1970) found that the duration of labour was similarly associated with the time elapsing between birth and the ewe standing up. It is interesting to note that Alexander found that the relationship was stronger in ewes which had a higher nutritional level during pregnancy. In addition, Shelley (1970) found that longer than average labour was associated with a higher incidence of desertion. It is not possible to decide whether the high incidence of desertion in the assisted ewes was associated with length of labour or the assistance given, but the incidence of desertion was not related to length of labour in the other ewes. 369 V. ACKNOWLEDGMENTS We thank all those who assisted in maintaining continu6us observations on the experimental animals, Mr. R. Jardine for statistical advice, and Dr. R. H. Watson for the interest shown in the experiment. Financial assistance for this project was provided by the Wad Research Trust Fund. VI. REFERENCES Alexander, G. (1960). Proceedings of the Australian Society of Animal Production. 3: 105. Alexander, G., and Peters&, J. E. (1961). Australian Veterinary Journal. 37: 371. McHugh, J. F., and Edwards, M. S. H. (1958). Journal of the Department of Agriculture, Victoria. 56: 425. Moule, G. R. (1954). Australian Veterinary Journal. 30: 153. Russel, A. J. F., Doney, J. M., and Gunn, R. G. (1969). Journal of Agricultural Science, Cam bridge. 72: 45 1. Shelley, L. (1970). Proceedings of the Australian Society of Animal Production. 8: 348. Thomson, A. M., and Thomson, W. (1949). British Journal of Nutrition. 2: 290. 370