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Effect of 75% replacement of dietary N by urea and ammonium sulphate on the composition and properties of sheep's milk
Published online by Cambridge University Press: 01 June 2009
Summary
A 23-week trial was conducted using 4 groups each of 6 ewes to study the effects on milk yield and composition of substituting non-protein nitrogen (NPN) for 75 % of the dietary nitrogen. The control group received a winter ration which included silage followed by a summer ration containing lucerne. The test groups received substitutes of urea, ammonium sulphate, or urea+(NH4)2SO4. The milk yield of the test groups was lower (P < 0·01) than that of the control group. Depression of the fat content of the milk reached statistical significance (P < 0·01) in the groups receiving (NH4)2SO4 and urea+(NH4)2SO4. In comparison with the control group, the protein content of the milk was greater in the group receiving urea and smaller in the other 2 test groups. The milks of the test groups had lower amounts of essential amino acids in the free state and higher amounts of non-essential amino acids than did the control milk. Milk-clotting time was increased in the test groups; the increase was greatest (P < 0·01) for the group receiving (NH4)2SO4 and least (P < 0·05) for that receiving urea.
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- Copyright © Proprietors of Journal of Dairy Research 1973