Between year differences in 18 years of lambing data from a commercial property

Abstract

Animal Production in Australia 1998 Vol. 22 BETWEEN YEAR DIFFERENCES IN 18 YEARS OF LAMBING DATA FROM A COMMERCIAL PROPERTY P. J. HOLSTA , F.B. DONNELLYB and J.R. AVEYARD A B C C NSW Agriculture, Cowra, NSW 2794 19 East Street, Parkes, NSW 2870 Plevna, Trundle, NSW 2875 The number of lambs marked affects the economics of sheep production and is a result of twinning percentage, number of dry ewes and lamb wastage. Flocks with poor reproductive performance were the subject of considerable research activity in the 1970s (Plant et al. 1976) but investigations were mostly confined to less than two year s study. This paper presents 18 years (1973-1990) of lambing data (Table 1) from a commercial Merino (Wonga bloodline) property located at Trundle, New South Wales. In each year 2300 to 3800 ewes of mixed ages lambed in August - September producing data on 55 857 ewes. Meteorological data for that period were fitted to a subclover growth model (G. Murray, pers. comm.) which provided annual estimates of dry matter production (DM) and timing of the onset of autumn rains, both being measures of the seasonal affects on lamb production. Table 1. Values for lamb marking, twinning, lamb deaths, forage production and grazing days Ye a r 1983 1973 1980 1987 1975 1974 1989 1988 1979 1986 1985 1981 1984 1978 1990 1982 1977 1976 Mean A No. of ewes (000) 2.6 4.2 2.6 3.7 3.6 3.8 3.8 3.8 2.7 3.2 2.7 2.6 2.7 2.7 3.5 2.3 2.6 2.7 Lamb marking % 85 86 86 88 93 96 96 98 99 00 02 03 05 06 06 07 10 10 98.7 Twinning % 94 99 98 107 117 119 122 118 113 121 117 128 130 124 130 130 129 131 118.2 Lamb deaths % 9.7 13.2 11.9 17.8 20.6 18.7 21.3 17.4 12.3 17.3 12.5 19.7 19.5 14.6 18.6 17.5 14.4 15.8 16.3 Grazing A days 120 108 114 117 54 138 116 97 128 17 67 87 109 143 87 123 176 175 109.8 Dry matter t/ha Current Previous 9.2 2.0 1.8 6.9 6.3 11.4 7.5 7.6 2.3 1.9 7.1 3.3 4.4 7.0 7.9 0.5 5.6 11.5 5.8 0.5 2.0 2.3 1.9 11.4 2.0 7.6 6.9 7.0 7.0 4.4 1.8 9.2 5.6 7.5 3.3 11.5 6.3 1 1 1 1 1 1 1 1 1 Number of days from germination of subclover to first lamb Table 1 shows the considerable variation in lamb marking percent, twinning percent and percent of dead lambs. High lamb marking percentages were dependent on high twinning percentages (P < 0.001) and there was a significant (P < 0.01) effect of previous year s nutrition on twinning perhaps through preventing ewe weight loss over lactation (Egan 1984). There were insufficient early seasons to determine the effect of current year s nutrition on twinning. Number of lambs dying was directly related (P < 0.05) to the number of twins up to 120% but thereafter losses were no greater. The results indicate that to achieve high lamb marking percentages the ewes need to have adequate liveweights at joining. EGAN, A.R. (1984). In Reproduction in Sheep. (Eds D.R. Lindsay and D.T. Pearce) p. 262 (Australian Academy of Science: Canberra). PLANT, J.W., FERGUSON, B.D., OHALLORAN, W.J. and MARCHANT, R. (1976). Proc. Annu. Conf. Aust. Vet. Assoc. 53, 189-90. 404