Variation in the composition of milk protein from pasture‐fed dairy cows in late lactation and the effect of grain and silage supplementation

Abstract

Sources of variation in milk protein composition were determined after approximately 203 days-in-milk for spring-calving Friesian cows grazing ryegrass-white clover pastures in New Zealand. Three groups each of 15 multiparous cows were managed as separate herds. Each herd was subjected to one of three management strategies: pasture only, pasture supplemented with 2-3 kg cow 1 d -1 maize grain, and pasture plus 5-6 kg cow -1 d -1 maize grain and 3-4 kg cow -1 d -1 pasture silage. During a 3-week period beginning in February 1994, milk samples were collected twiceweekly from individual cows and the detailed protein composition determined. Variation was observed in milk yield and the concentrations of all protein components measured, with betweencow variation being greater than within-cow variation for all parameters except non-protein N and urea. Supplementing pasture with maize grain and/or silage increased milk yield but had only minor effects on protein composition. These data will enable increased efficiency of experimental design in this research area, and provide details of the natural variation in milk protein composition. This variation gives an indication of the extent that *Author for correspondence A98046 Received 9 September 1998; accepted 7 April 1999 milk protein composition could be manipulated by on-farm practices, or through the selection of cows with defined milk protein profiles.

Differences in whey protein content between cow's milk collected in late pasture and early indoor feeding season from conventional and organic farms in Poland

“…The farming system had a significant effect on milk fat and lactose contents and on somatic cell count (SCC). Lower protein, casein and fat amounts were observed in organic milk compared to conventional milk, as previously reported by Toledo et al 23 and Olivo et al 24 Mackle et al 25 have shown that the cow's diet can be responsible for differences in casein concentration of up to 10%. Nevertheless, in the present study, during LP there were no effects of the diet on casein concentration; differences in casein concentration between organic and conventional systems were only of the order of 3.5% (Table 4).…”

“…The concentration of Lz in milk samples ranged from 12.56 to 16.60 µg L −1 , although no significant difference was found between organic and conventional systems during LP season. Mackle et al 25 reported that energy intake could affect concentrations of whey proteins. Concentrations of α‐La and β‐Lg decrease and concentrations of BSA increase when pasture intake is restricted compared with fully fed animals.…”

Differences in bioactive protein and vitamin status of milk from certified organic and conventional farms

“…According to Mackle et al . (), the content of the main albumins was reduced in the milk of cows whose diet included a limited amount of green forage. The authors found that an increase in energy taken in with feed increased the concentration of whey proteins in milk.…”

Effect of the diets with pumpkin silage and synthetic β‐carotene on the carotenoid, immunoglobulin and bioactive protein content and fatty acid composition of colostrum

“…The concentration of α‐lactalbumin and β‐lactoglobulin whey proteins is higher in colostrum than in mature milk (Georgiev, ). Gray and Mackenzie () and Mackle, Bryant, Petch, Hooper, and Auldist () note that the content of whey proteins in milk is largely determined by dietary energy intake and is lower with limited energy intake. In our study, the dietary energy level was uniform in all the groups, and the lack of differences between the groups in α‐LA and β‐LG concentration supports the results of the authors cited above.…”