Abstract:
hoc. Amt. Sot. Anirn. Prod. I994 Vol. 20 MEASURING THE PERFORMANCE OF TASMANIAN DAIRY HEIFERS: PRELIMINARY OBSERVATIONS M.J. FREEMAN Dept of Primary Industry and Fisheries, Elliott Research Station, PO Box 236, Somerset, Tas. 7322 Improved first lactation production associated with increased liveweights at point of first calving has been demonstrated in Queensland (Kerr et al. 1985) and New Zealand (Bryant and McRobbie 1991). Poor liveweight gains, and subsequent low liveweights at point of calving, may be the major factor in the poor first lactation production achieved by Tasmanian heifers, of 129 kg and 168 kg protein and fat respectivly (Tasmanian Dairy Industry Authority (TDIA) 1993). This project aimed to determine current Tasmanian heifer liveweights and quantify the production gains possible with increased liveweights. Three hundred and ninety-six Friesian heifers from 12 spring calving Tasmanian farms were weighed at point of first calving and their subsequent lactation monitored. The heifers were grouped by weight ranges and average production levels of-milk, fat and protein shown in Table 1. Table 1. Mean (2 s.e.) average production of heifers which first calved in 1992 and completed a lactation Liveweight at point of first calving was found to have a significant effect upon first lactation production. Linear regression analysis showed production gains of 7.3 L, 0.18 kg and 0.22 kg for milk, protein and fat respectively (P < O.OS), for each kg increase in liveweight at point of calving. For the pupose of analysis all lactations were adjusted to 270 days. There was some variation between the 12 herds resulting from the differences in breeding and management. Some farmers fed 1 or a combination of concentrates, irrigated pasture and/or fodder crops, eg. turnips, while other farmers fed non-irrigated pasture only. Liveweight at point of calving is a significant factor in first lactation production in Tasmanian spring calving herds. Production increases, comparable to those proven in Queensland and New Zealand, are evident for every kg liveweight increase at point of calving. The low first lactation production achieved by the lighter heifers (Table 1) is similar to the average heifer lactation as recorded by the TDIA, indicating that there may be a deficiency in heifer liveweights in Tasmania. BRYANT, A.M. and McROBBIE, G.A. (1991). Proceedings of the Rurakura Farmers Conference, Hamilton, pp. 26-32. KERR, D., BIRD, A.C. and BUCHANAN, I.K. (1985). Qld. Agric. J. 3: 32. TASMANIAN DAIRY INDUSTRY AUTHORITY (1993). Annual Report. 385