Original scientific paper
EFFECT OF MILK UREA AND PROTEIN LEVELS ON FERTILITY INDICES IN COWS
Malgorzata JANKOWSKA
Anna SAWA
Wojciech NEJA
Abstract
An analysis of the effect of milk urea and protein levels in four consecutive lactations on fertility indices of Blackand-
White Polish Holstein-Friesian cows, milk recorded in the Kujawsko-Pomorskie province has been made. Poorer
fertility indices were found in first-calf heifers and second lactation cows receiving energy-deficient diets and in
older (third and fourth lactation) cows receiving excess dietary protein and energy. Best fertility was found in young
cows fed excess protein (>3.60%) regardless of milk urea levels, and in older cows having lower and optimum levels
regardless of protein levels. Cow fertility is differentiated more by milk protein levels than by urea content. Fertility
parameters were poorer in first and second lactation cows than in older cows. The coefficients of correlation between
milk urea and protein levels and fertility indices were very low, with the only significant differences between protein
content vs. calving interval and reproductive rest period.
Keywords
cows; urea; protein; fertility
Hrčak ID:
68174
URI
Publication date:
20.1.2011.
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