Ah. Kirton et al., YEAR EFFECTS ON THE CARCASS COMPOSITION OF LAMBS SLAUGHTERED OVER A 10-YEAR PERIOD, New Zealand Journal of Agricultural Research, 41(2), 1998, pp. 227-233
A trial involving the body and carcass analysis of 7885 lambs sired by
15 different breeds of ram and run at two New Zealand locations (Ruak
ura and Manutuke) over a 10 year period was analysed to determine the
significance and size of the year effect on lamb composition. Animal s
ize (growth rate) differed between sites with the Manutuke lambs being
approximately 10% larger. Year had a very significant effect on the m
uscle, fat, and bone measurements investigated, with this effect remai
ning after adjusting measurements to the same carcass weight. Carcass
fatness was strongly influenced by carcass weight which differed betwe
en years. At the same carcass weight, lambs differed by around 5% fat
as a proportion of carcass weight or around 20% fat as a proportion of
total fat, between the most extreme years at each location. Year diff
erences were as large as those associated with identifiable management
factors (breed, strains, sex, etc). Unfortunately, the underlying fac
tors contributing to the year effect are at this stage unknown, but ma
y provide a fruitful field for additional research.