617. Variations in the carotene and vitamin A contents of herd butterfats throughout lactation

1. The levels of vitamin A alcohol and ester, carotene and xanthophyll in the blood plasma of six cows, grazed out-of-doors on pasture under typical New Zealand conditions, have been followed throughout one lactation. The same constituents have also been followed in the milk fats of these animals and in commercial factory butters over the same season.2. The seasonal trend in the vitamin A and carotenoid content of New Zealand milk fat is a reflexion of the changing level of these substances in the blood plasma.3. The decreased level of carotene, xanthophyll and vitamin A ester in the blood plasma over the summer months is consistent with a decreased absorption or utilization of carotenoids over this period.4. Throughout the year the vitamin A in the milk fat is predominantly in the ester form with no increase in vitamin A alcohol indicative of any increased utilization of hepatic vitamin A reserves.The author is indebted to the Department of Scientific and Industrial Research for a grant towards this investigation; to Mr M. R. Patchell and the farm staff of The Dairy Research Institute (N.Z.) for assistance in the collection of milk and blood samples; to Dr F. H. McDowall, Mr A. K. R. McDowell and the staff of the Chemistry Laboratory, The Dairy Research Institute (N.Z.), for the preparation of the fat samples and for the supply of factory butters. The assistance of Miss Fay Frecklington and Miss Jane Monroe with part of the experimental work is also acknowledged.

Section: Discussionmentioning

confidence: 99%

657. Factors influencing the vitamin content of milk fat: III. Seasonal changes in the vitamin A and carotenoid content of the blood plasma and milk fat of cows on pasture

McGillivray

1957

“…The decline in values in June, July and August probably was due to the increasing quantity of milk from cows in early lactation and to the decreasing quantity from cows in late lactation. It is surprising, however, that early post-colostral milk, which would reach its maximum proportion in the mixed milk in late July or in August (15), apparently had little effect on the phospholipid content.…”

Section: (4) Comparison Of Proportions Of Lecithin Cephalin and Sphimentioning

confidence: 98%

708. Phospholipids in New Zealand dairy products: II. Seasonal variations in the phospholipid content of butter and of milk and cream

McDowell¹

1958

Self Cite

Samples of milk, skim-milk and raw cream from one factory and of pasteurized cream, buttermilk and butter from two factories were taken twice monthly for varying periods for estimation of total phospholipids and (in butter only) of lecithin, cephalin and sphingomyelin.Seasonal variations in the phospholipid contents of milk, skim-milk and raw cream over 13 months probably were due to the greater proportion of small fat globules in autumn (late lactation) milk compared with spring (early lactation) milk.There were regularly recurring seasonal variations in total phospholipid content of the butters over 3 years. Maximum results were found during autumn and minimum results in winter. Lecithin, cephalin and sphingomyelin contents followed the same trends as the total phospholipid contents.Seasonal variations in phospholipid contents of buttermilks and butters were due mainly to variations in the amount of phospholipid per unit of fat in the cream. Differences in butter-making technique had little effect on the proportion of phospholipids from the cream retained in the butter.Average results for total phospholipid content of the products examined were: milk, 0·038% (0·031–0·050%); skim-milk, 0·018% (0·014–0·023%); buttermilk, 0·156% (0·103–0·191%); butter, 0·133% (0·099–0·181%). The average result for percentage of total phospholipid in the fat of the raw creams examined was 0·44% (0·38–0·51%); and in the fat of the pasteurized creams 0·41% (0·35–0·49%). Average weighted results for total phospholipid and for lecithin, cephalin and sphingomyelin contents of butter were 0·139, 0·041, 0·051 and 0·047% respectively.

“…Repetitive experiments using improved strains of red clover produced negative results. 4. The mechanism by which diets high in clover depress fat potency, iodine value, oleic acid percentage and tocopherol content is not clear.…”

Section: Discussionmentioning

confidence: 99%

656. Factors influencing the vitamin content of milk fat: II. The influnce of botanical composition of the pasture

Worker

McGillivray

1957

1. The effect of the level of clover intake on the vitamin A potency of milk fat has been studied, using Jersey cows from the herd of the Dairy Research Institute (N.Z.).2. In preliminary experiments in which composite bi-weekly butterfat samples were obtained from the whole herd of thirty-eight cows no relationship could be established between level of clover intake and potency of fat produced. This was assumed to be due to the rapidity with which the level of clover intake varied, since under normal grazing management the cows were moved to a fresh paddock (which was often of widely different botanical composition from that previously grazed) after every second milking.3. In later experiments in which three pairs of monozygous twins from the herd were used, a clear-cut relationship was established between clover intake and potency of fat produced and between clover intake and iodine value, oleic acid percentage and tocopherol content. Diets high in clover tended to depress total potency, iodine value, oleic acid percentage and tocopherol content of the fat, while diets low in clover had the reverse effect. The clover used in these experiments was mainly an improved strain of white clover containing approximately 0·03% cyanide. Repetitive experiments using improved strains of red clover produced negative results.4. The mechanism by which diets high in clover depress fat potency, iodine value, oleic acid percentage and tocopherol content is not clear. It is suggested, however, that it may be due to (i) the low tocopherol content of clover relative to grass, (ii) the high HCN content of certain species, and (iii) the possibly lower oleic acid content. The possibility is also considered that it may be due to some factor (or group of factors) associated with the stage of development of the pasture as a whole at a time when clover happens to be the dominant pasture species.5. Drenching cows with thiocyanate, the probable detoxication product of HCN in the ruminant, could not be shown to have any effect on the levels of vitamin A alcohol, ester, carotene, or xanthophyll in the blood and milk fat.Some of the results of this investigation form a section of a thesis submitted by one of us (N.A. W.) in partial fulfilment of the requirements for the degree of M.Agr.Sc. of the University of New Zealand. The authors are indebted to the Department of Scientific and Industrial Research for a grant towards the investigation and to Mr M. R. Patchell and farm staff of The Dairy Research Institute (N.Z.) for assistance in collection of milk and blood samples. The technical assistance of Miss Fay Frecklington is gratefully acknowledged.