Abstract:
Animal Production in Australia Vol. 15 SUPPLEMENTARY FEEDING OF EWES IN PRIME IAMB PRODUCTION SYSTEMS H. DOVE* , M. FREER* , A. AXELSEN* and R.W. DOWNES* SUMMARY Crossbred ewes grazing improved pasture were either unsupplemented or given 0.5 kg/d of oat grain or sunflower meal in late pregnancy or early lactation or both. Supplementation in pregnancy increased maternal weight at lambing by more than 5 kg. Despite some compensation later, unsupplemented ewes remained lighter than supplemented ewes until the end of the experiment at weaning. Fleece weights were heavier when ewes were supplemented in pregnancy rather than in lactation. Ewe supplementation did not influence lamb birth weights but markedly increased lamb weight gains so that the number of single lambs reaching market weight was doubled. There was little difference between the two supplements or the various lengths or times of supplementation. Pre-lambing supplementation seemed preferable for twins. INTRODUCTION The productivity of the prime lamb industry in southern Australia is low. For example, in one survey, the number of prime lambs sold per 100 ewes mated in Victoria and NSW, even on specialist prime lamb properties, was only 65-75% (BAE 1976). Though this suggests that ewe nutrition is inadequate at some stage of pregnancy or lactation, the supplementary feeding of ewes in prime lamb systems is usually restricted to drought conditions (Hodge et al. 1981). In this study, we examined the responses of crossbred ewes and their lambs to supplements of oat grain or sunflower meal (SFM) given in pregnancy, lactation or both. Sunflower meal was included as a supplement because of the potential for its increased availability, should oil from oilseeds become widely used as a source of diesel fuel (Dove et al. 1981). MATERIALS AND METHODS Animals and their management Two hundred and seventy-five Border Leicester x Merino ewes (mean weight 45.9 kg) due to lamb in late August were randomised in late June into 11 goups, each containing 14 ewes mated to Dorset Horn rams and 11 ewes mated to Border Leicester rams. The groups were supplemented daily at 0900 hours with 0.5 kg/ewe of either oat grain (9.9 % CP) or pelleted SFM (36.8% CP) for periods of 9, 6 or 0 weeks before lambing coupled with 0 or 6 weeks after lambing. During the experiment, all groups grazed a series of paddocks containing phalaris and subterranean clover, remaining 2-4 weeks in each area. Before groups moved to a new area, pasture availability was assessed by visual scoring (Morley et al. 1964) and groups distributed across the area so as to equate available herbage between groups. This minimized the random differences between groups arising from plot differences. Due to prolonged drought, grazing pressures were high and pasture supplies until late September averaged only 350-400 kg DM/ha. in response to good mid-spring rains, there was abundant pasture from early October until growth ceased in late November. Measurements Ewes weights were recorded every two weeks and fleece weights recorded at *Div. of Plant Industry, CSIRO, GPO Box 1600, Canberra, A.C.T. 2601. 329 Animal Production in Australia Vol. I5 shearing in early December. During lambing in late August, lambs were identified daily with their ewes, weighed and fitted with rubber rings to remove tails and castrate male lambs. Lamb weights were measured every two weeks until weaning on December 1, or until lambs reached 32 kg, when they were sold.. Statistical analyses Treatment responses in ewes were assessed by analysis of variance using the GENSTAT package. Comparisons were made between control and supplemented groups and, within the latter, between the effects of supplement type or length of supplementation. Since the number of lambs born in each group varied, a similar analysis of the lamb data was not possible. Instead, responses were assessed from analyses of variance conducted separately for single, twin, Dorset Horn cross and Border Leicester cross lambs. Direct comparisons of breed and birth type were not made but individual group means were compared using the Student-Newman-Keuls procedure. RESULTS Of the 275 ewes, 19 were barren (6.9%), 186 produced single lambs, 68 produced twins and two produced triplets. Eight ewes (2.9%) died during the experiment. The lambing percentage (lambs born/100 ewes lambing) was thus 125.8. Perinatal mortality in singles was 5.6% and in multiples was 31.0%, with no effect of treatment. As a result of the overall mortality of 18.3%, 102.7 lambs were reared per 100 ewes lambing. Responses of ewes to supplementation Unsupplemented ewes just maintained conceptus-free weight over late pregnancy (+0.29 kg) while ewes supplemented before lambing gained 5.3 kg (P<O.OOl). There was no difference in gains between SFM (5.5 kg) and oats (5.1 kg) but the effect of length of supplementation approached significance (9 weeks 5.8 kg; 6 weeks 4.8 kg; 0.10>P>0.05). Supplemented ewes were thus significantly heavier after lambing (Table 1). Thereafter, control ewes gained faster (P<O.OOl) than those which had been or were being supplemented. Nevertheless, supplemented ewes were still significantly heavier throughout the experiment (Table 1). By the end of the post-lambing feeding period, there was a significant linear effect of length of supplementation (P<O.OOl). This effect had disappeared by the end of the experiment. Ewes supplemented for only 6 weeks after lambing had lighter fleeces than other supplemented groups (PcO.025) but the mean of all the supplemented groups was not significantly higher than that of the control group. Responses in lambs Pre-lambing supplementation did not influence the birth weight of single lambs (5.98 kg) or twin lambs (5.04 kg). Similarly, it did not influence the birth weight of Dorset Horn cross lambs (5.92 kg) or Border Leicester cross lambs (5.34 kg). Ewe supplementation markedly increased the liveweight gain (LWG) of single lambs (P<O.OOl; Table 2) during the first 6 weeks of life, but there were no effects of supplement type or duration of feeding. The effectsin twin lambs were even more pronounced. Type of supplement also had 'no effect here, but there was a trend towards lower gains in those twins whose dams were supplemented only after lambing and higher gains in those whose dams had been supplemented both before and after lambing. The pattern of responses in Dorset Horn cross and Border Leicester cross lambs considered separately was similar, with the latter group 330 Animal Production in Australia Vol. I.5 TABLE 1 Responses of crossbred ewes to supplements of oat grain or pelleted sunflower meal fed before and/or after lambing abControl' here signifies all animals not fed before lambing. Where superscripts occur, means not sharing a superscript are significantly different (P<O.OS) TABLE 2 Responses of lambs to supplementation of their dams with oat grain or pelleted sunflower meal 331 Animal Production in Australia Vol. 15 performing at a slightly lower level. After supplementation ceased, growth rates were lower in both singles and twins. Nevertheless, the number of lambs sold at 32 kg or heavier reflected the earlier trends in LWG. In the control igroup, only 31.3 % of single lambs and no twins reached this weight. In the 'groups fed SFM, 71.1% of single lambs reached 32 kg and the corresponding figure for oat-fed groups was 60.9%. Low and variable numbers of twins sold precluded meaningful comparisons between groups but, overall, 14.5% of twins from supplemented groups achieved saleable weight. DISCUSSION Supplementation substantially increased lamb LWG, presumably as a result of increased ewe milk production (Arnold et al. 1977) and, as a consequence, more than doubled the number of single lambs sold as prime. To achieve a market weight lof 32 kg by early December, lambs born in late winter need to grow at an average rate of about 250 g/d from birth. The mean LWG of single lambs exceeded this rate in all of our supplemented groups (overall means SFM 272 g/d, oats 269 g/d) Iwhereas in the control group the mean LWG of singles was 233 g/d from birth till the end of the experiment. Despite evidence that, for pregnant or lactating ewes, oat grain is ideficient in protein when fed alone (Hodge et al. 1981) and despite responses to protein supplements in grazing ewes (Arnold et al. 1977) we have no conclusive evidence that SFM was a better supplement than oats. Cur results suggest little need for more than 6 weeks of supplementation Iwhich, surprisingly, appeared, at least for single lambs, to be equally satisfactory either before or after lambing. The results for twin lambs should be interpreted cautiously because of the low numbers involved, but they did suggest that 6 weeks of post-lambing supplementation was insufficient and that some supplementation in pregnancy was required. Even so, few twins reached a saleable weight. It should also be noted that supplements increased ewe live weight and wool growth as well as lamb growth. This is similar to the findings of Arnold et al. (1977) and has implications for the mating of the flock in the following year. Our results have shown large increases in productivity as a result of the use of supplements. The profitability of these responses is of obvious interest, but an economic analyis of the results would be premature, since the study was done with only one level of supplementation and one, fairly low, level of pasture availability. The interactions between these parameters must be understood before evaluating the responses in economic terms, and they are therefore the subject of our continuing studies, especially in twin lambs. ACKNOWLEDGEMENTS We thank Messrs T.J. S hepherd, J.E.C. James, M.D.-Crouch , J.B. Nadin, K.G. Pullen and P.W. Flint for thei r technical assistance. REFERENCES ARNOLD, G-W., WALLACE, S.R. and DE BOER, E.S. (1977). Aust. J. Exp. Agric. Anim Husb. a:915. BAE (1976). In 'Prime Lamb Production in New South Wales: An Economic Survey? Bureau of Agricultural Economics. (A.G.P.S.:Canberra). DOVE, H., FREER, M. and COOMBE, J.B. (1981). In 'Proceedings of the National Conference on Fuel from Crops', p.53.1. (S.A.E. Australasia:Melbourne). HODGE, R.W., BOGDANOVIC, B. and SWEATMAN, D. (1981). Aust. J. Exp. Agric. Anim. Husb. &400. 332