Feeding female weaner Merino sheep during drought on the central tablelands of New South Wales.

Abstract

222 Proc. Aust. Soc. Anim. Prod. Vol. 17 FEEDING FEMALE WEANER MERINO SHEEP DURING DROUGHT ON THE CENTRAL TABLELANDS OF NEW SOUTH WALES H. LLOYD DAVIES*, I.R. McRAE* and D.J. PETRIE* SUMMARY Female Medium Peppin Merino weaner sheep weighing 13.8 kg (kO.17) were fed the following survival rations from early November 1982 until early February 1983: 230 g wheat + 90 g chaff; 270 g wheat + 110 g chaff, 310 g wheat + 120 g chaff. The highest level of supplementation resulted in significantly (P < 0.06) higher liveweight gain (69 g/d compared with 55 g/d) than the other two levels. Survival of weaners was independent of treatment but was related to initial weight. The lower level of supplementation was sufficient to ensure survival of 89% of the Key words: drought, ration, survival, Merino, weaners >12 kg during drought. weaners . INTRODUCTION The 1982-1983 drought was one of the most severe ever suffered on the central tablelands of New South Wales with conditions of 1982 being particularly bad. The Field Stations of the University of New South Wales at Wellington and Stuart Town were faced with the problems of feeding weaner sheep for survival on paddocks in which there was no apparent feed on the ground. The mothers of the lambs had been fed drought rations on bare paddocks leading to a mean weaning weight of 13.8 kg (20.17) at a mean age of about 14 weeks. There is little guidance from the literature on drought-feeding on the amounts of grain and roughage to be fed to young weaner sheep under 20 kg. For instance, Oddy (1978) has the lowest liveweight for sheep maintenance requirements at 25 kg. We decided to study the effect on survival and production of feeding at three levels of wheat grain + 28% roughage. MATERIALS AND METHODS Location This work was carried out on 6 plots of naturalized pastures at Wellington Field Station of the University of New South Wales. There forage visible or measurable on the ground. The rainfall for 1982 was year average - 660 mm) - the rainfall from April to December inclusive Sheep 209 female Merino sheep born in August, weaned on October 2, were used in the study. At the start of the experiment they weighed 13.8 kg (kO.17) and the range in liveweight was 10 to 20 kg. Diets There were three levels of supplementation viz. (i) 230 g wheat and 90 g lucerne chaff, (ii) 270 g wheat and 110 g chaff, and (iii) 310 g wheat and *School of Fibre Science and Technology, University of N.S.W., P.O. Box 1, Kensington, N.S.W. 2033. the was no 290 mm (70 was 116 mm. Proc. Aust. Soc. Anim. Bad. Vol. 17 223 120 g. chaff. The chemical composition of the supplements was wheat: 2.3% nitrogen (N), 1.7% acid detergent fibre (ADF), 1.5% Ash, 89.7% dry matter (DM), lucerne chaff: 2,9%'N, 35.7% ADF, 9.6% Ash, 90.3% DM. If we assume a metabolizable energy value of 13 megajoules (MJ)/kg for the wheat and 9 MJ/kg for the chaff, group 1 received 3.8 MJ/day of metabolizable hay energy (ME), group 2 received 4.5 MJ/day; and group 3 received 5.1 MJ/day. Replication There were two replicates for each treatment with each treatment being randomly distributed to six plots. The numbers in each group differed because of differing plot size,but the mean stocking rate on each plot was the same at 4:9 sheep per hectare. Manadement The weaners were trained to accept feed from the trough from the 20th October 1982 and all received the same treatment of gradually increasing amounts of.wheat and reducing amounts of lucerne hay + lucerne chaff until the 8th November when they received their designated rations. The weaners were shorn on the 10th December. This shearing in the middle of the experiment was unavoidable because it had to fit in with the rest of the Station's shearing. The sheep were given an anthelmintic (Exhelm E) and jetted with Vetrazin against fly-strike. The sheep were 'weighed at intervals of two weeks. Deaths were recorded as sheep which died of natural causes or whose liveweight fell below 10 kg. STATISTICAL ANALYSIS Survival Initially the data were examined on a plot basis for assessment of the effect of initial weight upon survival. Mean initial liveweights of the survivors and non-survivors were'compared using the two-tailed t test. Liveweight The effect of treatment on daily liveweight gain was assessed by analysis of variance on plot means. Linear regression was used to determine if initial weight had any effect on final weight. The effect of treatment upon final 1,iveweight and ,survival was determined by analysis'of covariance using .initial.weight as the . dovariate. RESULTS Surviva l 21 weaners 'died' out of the 208 originally involved in the experiment. There was no relation between treatments dnd weaner losses. There was a significant relationship (P < .Ol.) between initial weightand survival as shown in Fig. 1. This figure shows the importance of initial'liveweight upon survival-of.weaner sheep even when offered a comparatively adequate,diet. A relationship between weaning weight and survival over the summer ondry. feed,involving far more< weaners and a wider range of weaning weights. has been given by'lloyd Davies (1987) who showed that on dry mature pastures in south yestern .Australia there were 80% deaths among weaners under 14 kg, 45%.losses in weaners under 18 kg, and 33% .' Yosses for weaners under 23 kg. . 224 Proc. Aust. Soc. Anim. Prod. Vol. 17 Fig. 1 The effect of initial weights on survival Liveweight There was a significant positive (P < 0.05) linear relationship between initial and final liveweight. None of the nutritional treatments had a significant effect on final liveweight. The effect of treatment upon liveweight is shown in table 1. Table 1. The effect of three levels of supplement on the liveweight gain of female weaner Merino sheep The effect level with direction. there being of treatment upon liveweight change was significant at the P < 0.06 the 28% difference in growth rate (69g/d v 54 g/d) being in the expected There was no difference between Treatment 1 and Treatment 2 despite a difference of 0.7 megajoules of M.E. consumed per day. DISCUSSION There has been little published work on the survival feeding of weaner sheep during drought since the classical work of Franklin et al. (1955);and recommendations vary from feeding ad libitum to 200 kg of wheat for 100 (i.e. 286 g/d) dry sheep for a week for survival (Oddy 1978). Franklin et al. (1955) noted 83.3% survival and maintained body weight in 7 month old weaners weighing 18 kg and fed 386 g per day of 50:50 wheat grain: wheat chaff (3.05 MJ/d). No figures are available anywhere for weaners under 15 kg. This work would indicate that on a diet providing 3.8 MJ of ME/d, a survival rate of 89 % is achieved for weaners heavier than 12 kg and there is a small liveweight gain. The only reason that can be Proc. Aust. Soc. Anim. Prod. Vol. 17 225 proffered for this apparent negligible effect of higher feeding is that even on apparently bare plots, there could be small differences in the amount of forage on different plots. Recommendations for survival feeding have previously been based on pen experiments and we hope that, in future droughts, some further data will be generated on the effect of feeding different levels of wheat (the most commonly available grain in drought) and levels and range of roughages under field conditions so that an assessment may be made of the relevance of present recommendations under field conditions. REFERENCES FRANKLIN, M.C., McCLYMONT, J-L., BRIGGS, P.K. and CAMPBELL, B.L. (1955). Aust. J. Agric. Res. 6: 324. LLOYD DAVIES, H. (T987). W.A. Dept of Agriculture Technical Bulletin No. 72. ODDY, V.H. (1978). N.S.W. Department of Agriculture AG Bulletin 3.