Abstract

In an experiment replicated over three years, ewes were individually fed concentrate diets containing two levels of protein (12 and 18%) at either maintenance or 1.5 x maintenance from days 35 to 74 of pregnancy, and then at an allowance of approximately 2.0 kgDM/head/day on pasture until parturition. Half of the ewes within each treatment were shorn on day 74. Ewes were CT scanned to measure body composition at days 35, 74, 115 and 140 of pregnancy. Neither protein nor energy level fed during mid-pregnancy had any significant effects on conceptus growth, birth weight or lamb skeletal measurements. Shearing resulted in changes in ewe body composition as well as an increase of 0.36 kg (P<0.01) in lamb birth weights. Lambs from the shorn ewes were 14 mm longer in length (P<0.05) but 8 mm shorter in height (P<0.05) than those from unshorn ewes. Shorn ewes lost 1.3 kg more body fat (P<0.001) than their unshorn contemporaries over the second half of pregnancy. Unshorn ewes lost 0.74 kg of carcass lean over this period, while the shorn ewes gained 0.22 kg (P<0.001). The results show that ewes can be fed maintenance during mid-pregnancy if this allows good quality feed reserves to be built up in front of them for the third trimester. Mid-pregnancy shearing is likely to increase lamb survival in multiple born lambs through higher birth weights.

NB, Jopson, GH Davis, PA Farquhar, and WE Bain

Proceedings of the New Zealand Society of Animal Production, Volume 62, Palmerston North, 49-52, 2002