Studies on the properties of New Zealand butterfat: VII. Effect of the stage of maturity of ryegrass fed to cows on the characteristics of butterfat and its carotene and vitamin A contents

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Abstract
Summary: In two outdoor feeding trials with monozygotic twin cows during the spring and early summer months the effects of mature and immature H1 short rotation ryegrass on the composition of the butterfat produced and on the carotene and vitamin A contents of the butterfat and the blood were compared. In both trials the characteristics investigated were markedly affected by the stage of maturity of the grass. The butterfat from cows receiving immature ryegrass was more unsaturated and had higher carotene and vitamin A contents than that from cows receiving mature ryegrass. The blood of cows fed immature ryegrass also contained more carotene than the blood of cows fed mature ryegrass.It is suggested that variation in the stage of maturity of New Zealand dairy pastures throughout the year is an important factor contributing to the seasonal variations in the characteristics and the carotene and vitamin A contents of commercial butterfat. The influence of stage of maturity is probably associated with the quantity and nature of the pasture lipids.

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