A preliminary investigation into factors affecting lamb growth on Taranaki hill country

N.A. Thomson; W.B. Brown and M.J. Mace

Ministry of Agriculture and Fisheries, Taranaki Agricultural Research Station, Normanby and Ministry of Agriculture and Fisheries, New Plymouth

Proceedings of the New Zealand Society of Animal Production. 1985, 45: 137-140

The growth of lambs, herbage mass and pasture composition (pre- and post-grazing), were monitored from January to June 1984 on 3 farms carrying 12 to 13 su/ha in the Taranaki hill country. Live weight was measured monthly on a random 5% of each flock. Additional animals were treated with cobalt (vitamin B12), selenium or both to identify possible deficiencies of these elements. A 'preventative' drenching programme was adopted on each farm to control gastro-intestinal worms.

Mean daily live-weight gain was low (49 to 74 g/lamb) and did not improve significantly as a result of selenium or vitamin B12 treatment. Faecal egg counts indicating significant worm burdens were recorded on 2 of the farms in autumn despite regular drenching.

Pasture before grazing were characterised by a high herbage mass (>3000 kg DM/ha) and a low green leaf content (50 to 60%). Apparent utilisation of DM at a single grazing was low (14 to 24%) but utilisation of green leaf was higher (28 to 43%). Green stem and dead herbage were not utilised.

Although no factor was clearly defined as limiting animal performance, it is felt that improvements could be made by more intensive grazing (so that young stock are presented with lower herbage mass of higher green leaf content) and by adopting a more effective drenching programme.

Keywords: NZSAPAB; sheep; hill country; internal parasites; selenium; vitamin B12; pasture utilisation; pasture composition

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Last Updated 03-05-1997