Proceedings of the New Zealand Society of Animal Production.
1991, 51: 277-282
Proceedings of the New Zealand Society of Animal Production.
1991, 51: 277-282
Initial analysis of the data showed a significant (P<0.01) age effect on winter liveweight gain within a mixed age herd of cows. The average liveweight gain over eight years of the older cows (4 yr +) was 3 times that of the rising 2 year olds. Further analysis showed a significant (P<0.05) age effect on the relationship between liveweight at calving and production of milkfat in the following season. Higher liveweight at calving resulted in a greater increase in production for 2 year olds than for older cattle. The conclusion to be drawn from this is that wintering rising 2 yea old heifers separately from older cows to achieve higher liveweight may have beneficial effects on the following seasons production.
A field trial in winter 1990 to test this assumption showed the winter liveweight gain of rising 2 year old heifers and mature cows, offered the same herbage allowance, was significantly (P<0.01) higher when wintered separately than wintered as a mixed age herd. Subsequent milk solids production from the two-wintering systems was the same despite different liveweight at calving. Aspects of herd behaviour were suggested as the cause of the nil response.
Keywords: NZSAPAB; Age; liveweight; condition; milk solids; production; wintering systems; herd; behaviour
