The effect of physiological state, milk production traits and environmental conditions on milk fat globule size in cow's milk

Abstract

This research was carried out to quantify the effects of a range of variables on milk fat globule (MFG) size for a herd of Holstein-Friesian cows managed through an automatic milking system with year-round calving. We hypothesised that the overall variation in average MFG size observed between individual animals of the same herd cannot sufficiently be explained by the magnitude of the effects of variables that could be manipulated on-farm. Hence, we aimed to conduct an extensive analysis of possible determinants of MFG size, including physiological characteristics (parity, days in milk, days pregnant, weight, age, rumination minutes, somatic cell count) and milk production traits (number of milkings, milk yield, fat yield, protein and fat content, fat-protein ratio) on the individual animal level; and environmental conditions (diet, weather, season) for the whole herd. Our results show that when analysed in isolation, many of the studied variables have a detectable effect on MFG size. However, analysis of their additive effects identified days in milk, parity and milk yield as the most important variables. In accordance with our hypothesis, the estimated effects of these variables, calculated using a multiple variable linear mixed model, do not sufficiently explain the overall variation between cows, ranging from 2.70 to 5.69 µm in average MFG size. We further show that environmental variables, such as sampling day (across seasons) or the proportion of pasture and silage in the diet, have limited effects on MFG size and that physiological differences outweigh the effects of milk production traits and environmental conditions. This presents further evidence that the selection of individual animals is more important than the adjustment of on-farm variables to control MFG size.

Milk fat globule size development in the mammary epithelial cell: a potential role for ether phosphatidylethanolamine

“…Both these parameters can affect MFG size and could be contributing factors to the observed difference. However, we previously estimated the effect of these parameters on MFG size within our herd 20 . Based on this analysis we estimate that the difference between the groups attributable to the difference in days in milk and parity is in the magnitude of 0.21 µm (when comparing SMFG cows to LMFG cows, a decrease of 0.05 µm can be attributed to 25 additional days in milk in average for SMFG cows; and an additional decrease in MFG size of 0.16 µm can be attributed to the difference in parity, with an average parity of 1.8 for SMFG cows compared to 3.8 in LMFG cows).…”

“…MFG size also depends on the physiological state of the animal 16 , 19 and the milk from cows producing small or large MFGs can differ in the FA composition 14 , 18 . However, the magnitude of the effects of parameters such as the physiological state of the animal and its milk production traits on MFG size is less than the overall variation that is seen between individual animals 20 .…”

Variation in milk fat globule size and composition: A source of bioactives for human health

“…The distribution of globule size, within species, can be widely affected by parameters such as maternal physiology, breed, herd nested within herd, season and diet (Figure 2) (Fleming et al 2017;Wiking et al 2004;Logan et al 2014;Walter et al 2019), which is discussed in the following sections of this review.…”

“…Thus, MFG size (range distribution and average) is determined by a combination of factors such as genetics, diet, lactation stage and may also be regulated to fit the functional and nutritional requirements of the infant (Bourlieu and Michalski 2015) (not within the scope of this review). Differences in MFG size between individual cows within a herd exposed to identical environmental conditions and diet was demonstrated (ranging from 2.5 to 5.7 mm) (Logan et al 2014;Walter et al 2019). To understand the possible determinants of this variation, Walter et al (2019) conducted an extensive analysis of the factors affecting bovine MFG size at the individual animal level.…”

“…Differences in MFG size between individual cows within a herd exposed to identical environmental conditions and diet was demonstrated (ranging from 2.5 to 5.7 mm) (Logan et al 2014;Walter et al 2019). To understand the possible determinants of this variation, Walter et al (2019) conducted an extensive analysis of the factors affecting bovine MFG size at the individual animal level. Among the studied factors were physiological characteristics (parity, days in milk, days pregnant, weight, age, somatic cell count), milk production traits (number of milkings, milk yield, fat yield, protein and fat content, fat-protein ratio) and environmental conditions (diet, weather, season).…”