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The optimum level of protein in the supplement for dairy cows with access to grass silage

Published online by Cambridge University Press:  02 September 2010

F. J. Gordon  and
C. H. McMurray
F. J. Gordon
Affiliation:
Agricultural Research Institute of Northern Ireland, Hillsborough, Co. Down
C. H. McMurray
Affiliation:
Veterinary Research Laboratory, Stoney Road, Stormont, Belfast BT4
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Abstract

Grass silage with a dry-matter content of 19·4% and containing 16·7% crude protein was offered ad libitum to 42 first lactation British Friesian cows during the first 75 days post-calving. In addition the animals received supplementary concentrates containing either 10·3, 13·6, 17·3, 21·1, 25·2 or 30·3% crude protein on a fresh weight basis, with extracted soya bean meal being used as the main protein source. All concentrates were offered at an equal level of 8·0 kg per day. The relationship between milk yield and protein content of the supplement was curvilinear and was described by the following equation:

Y= 8·95+ 1·0×–0·0205×

where Y = milk yield per day in kg, and × = percentage protein in the supplement. This equation indicated that maximum milk yield was obtained with a concentrate containing 24·4 % protein on a fresh weight basis. The protein content of the milk was also curvilinearly affected by the level of protein in the supplement, and it was calculated that maximum milk protein (nitrogen × 6·38) would be obtained with a supplement containing 23·9% protein. Plasma blood urea levels increased linearly with increasing protein intake. The effects on live-weight change and blood components were also recorded.

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Type
Research Article
Information
Animal Production , Volume 29 , Issue 3 , December 1979 , pp. 283 - 291
Copyright
Copyright © British Society of Animal Science 1979

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References

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