Studies on the properties of new zealand butterfat: VI. Comparison of the properties and vitamin A potencies of butterfats produced by clover-fed and ryegrass-fed dairy cows

Abstract

In an indoor feeding trial with three sets of monozygotic twin cows during late spring the effects of H x short rotation ryegrass and white clover as feeds for the cows on the characteristics and the carotene and vitamin A contents of the butterfat were compared. The butterfat from the cows fed ryegrass had a lower iodine value and refractive index, higher Reichert and saponification values, and lower carotene and vitamin A contents than the butterfat from the cows fed clover. The carotene and vitamin A contents of the blood of the cows fed ryegrass were also lower than those of the cows fed clover.In a subsequent outdoor feeding trial with four sets of monozygotic twins the feeding of pure H x short rotation ryegrass or of perennial ryegrass was compared with the feeding of mixed pastures containing a high but varying proportion of clover. The results for the spring and early summer months were similar in direction but smaller in magnitude than those from the indoor feeding trial. In the result for the autumn months there was a reversal of the relationship for the characteristics and the carotene and vitamin A contents of the butterfat and for the carotenoid contents of the blood.It is suggested that the lack of consistency between the spring and autumn results could have been due to differences in the stage of growth of the ryegrass fed and that butterfat characteristics may be influenced more by the stage of maturity than by the botanical composition of the pasture.

Ryegrass varieties in relation to dairy cattle performance

“…In a previous experiment (McDowall 1963) in which the production was measured from cows fed white clover and Manawa ryegrass, the clover-fed cows produced a lower yield of milk. The combined results suggested that mixed pasture was superior to the pure ryegrasses in the present experiment because of an interaction of c!over with ryegrass, rather than a gross superiority of clover over ryegrass.…”

Seasonal variations in the composition and thermal properties of New Zealand milk fat: I. Fatty-acid composition

“…A lactational effect on the level of C 18 fatty acids, consisting of a rapid fall early in lactation followed by a more steady decline, was reported by Decaen & Adda (1966). Workers in New Zealand, however, have shown that seasonal changes in iodine value and other characteristics of milk fat are related to the stage of maturity of the ryegrass in the pastures (McDowall, 1962;McDowall, McGillivray & Hawke, 1961;McDowall & McGillivray, 1963a, b), while Hawke (1963 showed that the fatty-acid composition of milk fat from cows grazed on immature ryegrass was more unsaturated than that from cows grazed on mature ryegrass. These findings would indicate that, in New Zealand, pasture lipids have a greater influence on C 18 acids than do lactational effects.…”

Factors affecting the milk yield, milk composition and physico-chemical parameters of ghee in lactating crossbred cows

“…The previous findings were expected because the summer milk fat contained higher levels of C 4 and C 6 acids than the one found in the winter milk fat (Laurelle et al 1976). However, this discrepancy between both fats and in their fatty acid levels was due to the effect of the season of the year and consequently the plane of nutrition (McDowall and McGillivary, 1963;Hall, 1970;Gray, 1973). The BR reading was found to be lower (P<0.05) in summer compared to winter season.…”