Phospholipids and Fat Secretion by Cows on Normal and Low Fiber Diets: Lactational Trends

Abstract

Daily yields of milk, milk fat, phospholipids, and fatty acids were measured weekly during lactations of two groups of cows on a normal and restricted roughage diet. Milk yield was higher in normal cows during the initial 15 wk of lactation. Fat production decreased and was consistently lower in milk from cows on restricted roughage (from 1.2 to .4 in normal and from .8 to .3 kg/day for restricted). Phospholipid secretion decreased from an average 7 g to 3 g/day in both groups. The concentration of phospholipid in both milks fluctuated during lactation (20 to 30 mg/100 ml milk), but in milks from restricted cows it tended to increase with progress of lactation. Milk lipids from cows on restricted diets had higher phospholipid to fat ratio, (1.0 to 1.5 compared to .5 to .6 g phospholipid/100 g fat for milk from normal cows). Composition of the phospholipid classes changed slightly during lactation. Phosplatidylinositol changed most, increasing from 4 to 10 and 6 to 8% in normal and restricted milks, respectively. Fatty acids of short and medium chain lengths (C6 to C14) followed a typical quadratic regression in normal milks increasing from 10 to 30% of the total fatty acids during the first 25 wk of lactation. In restricted milk these fatty acids were already high (25%) within 2 wk and followed a linear regression with lactation. Both palmitic and stearic acid were lower in milk from restricted cows while oleic and linoleic acid were higher particularly after 10 wk of lactation.

Milk fat globule size is affected by fat production in dairy cows

“…At the same time the milk yield decreases, and the fat percentage increases after approximately the second month of lactation. In summary, both the yield of fat and the phospholipid secretion decrease during lactation, hence the phospholipid to fat ratio should be fairly constant throughout lactation (Kinsella & Houghton, 1975). Bitman and Wood (1990), on the other hand, found decreasing percentages of phospholipid and cholesterol in the total lipid from day 42 to 180 of lactation.…”

Reviews of the progress of Dairy Science: The bovine milk fat globule membrane–its formation, composition, structure and behaviour in milk and dairy products

“…However, other workers (Smith et al 1977) have observed that MFGM phospholipids obtained from cows fed protected sunflower/soya bean oil supplements contained higher proportions of linoleic acid than the phospholipids from normal milks. Low fibre diets resulted in an increase in the phosphatidyl ethanolamine content of the MFGM, while the levels of phosphatidyl choline and sphingomyelin decreased (Kinsella & Houghton, 1975).…”

“…Phospholipid levels also vary throughout lactation (Kinsella & Houghton, 1975) with phosphatidyl inositol levels increasing. However, since the total phospholipid content of the MFGM does not increase relative to the increase in total surface area of the fat globules as lactation proceeds, Kinsella & Houghton (1975) suggested that MFGM deficient in phospholipids may be produced, thus increasing the susceptibility of late lactation milk to hydrolytic rancidity.…”

Chemical changes in bovine milk fat globule membrane caused by heat treatment and homogenization of whole milk

“…Composition of MFGM in milk can be altered by various factors, such as animal, environmental, and processing factors. Animal factors include diet, season and stage of lactation, and breed of cow (Huang & Kuksis, 1967 ;Anderson & Cheeseman, 1971 ;Anderson, 1974 ;Anderson & Cawston, 1975 ;Kinsella & Houghton, 1975 ;Diaz-Maurino & Nieto, 1977 ;McPherson & Kitchen, 1983). Environmental factors include the presence of bacteria in milk from pre-or post-pasteurization contamination or the presence of mastitis pathogens in mastitic milk (Erwin & Randolph, 1975 ;McPherson & Kitchen, 1983).…”