Within-milking variation in milk composition and fatty acid profile of Holstein dairy cows

Abstract

Changes in milk composition during a milking are well characterized, but variation in milk fatty acid (FA) profile is not well described and may affect the accuracy of in-line milk composition analyzers and could potentially be used for selective segregation of milk. Within-milking samples were collected from 8 multiparous high-producing Holstein cows (54.86 ± 6.8 kg of milk/d; mean ± standard deviation). A milk-sampling device was designed to allow collection of multiple samples during a milking without loss of vacuum or interruption of milk subsampling. Milk was collected during consecutive morning and afternoon milkings (12-h intervals) and was replicated 1 wk later. Each sample represented approximately 20% of the milking and was analyzed for fat, true protein, and lactose concentration and FA profile. Milk fat concentration markedly increased over the course of milk let down (4.4 and 4.2 percentage units at the a.m. and p.m. milking, respectively), whereas milk fat globule size did not change. Milk protein and lactose concentration decreased slightly during milking. Modest changes in milk FA profile were also observed, as milk de novo and 16-C FA concentrations increased approximately 10 and 8%, respectively, whereas the concentration of preformed FA decreased about 7% during the milking. In agreement, mean milk FA chain length and unsaturation modestly decreased during milking (0.59 and 0.014 U, respectively). The observed changes in milk fat concentration during a milking are consistent with previous reports and reflect the dynamic nature of milk fat secretion from the mammary gland. Changes in milk FA profile are not expected to practically affect the accuracy of spectroscopy methods for determination of milk fat concentration. Furthermore, the small variation in FA profile during a milking limits the use of within-milking milk segregation to tailor milk FA profile.

Butter fatty acid composition as a function of soybean oil supplementation and time of milking, and performance of Holstein x Gyr cows fed with chopped elephant grass-based diets

“…Thus, the absence of the effect of milking time on the butterfat content of vaccenic acid was reflected in a similar content of rumenic acid, although the activity of the SCD enzyme was 14% higher (P<0.001) in the butter produced from milk from the cows that were milked in the afternoon (Table 5). In contrast to the present study, higher concentrations of rumenic and vaccenic acids were obtained in milk from the cows that were milked during the P.M. milking session (FERLAY et al, 2010;RICO et al, 2014;SCHWENDEL et al, 2015;VIBART et al, 2017).…”

“…These results corroborate the literature regarding the higher concentration of oleic acid and the lower palmitic acid in milk from cows milked during the P.M. milking (FERLAY et al, 2010;RICO et al, 2014;SCHWENDEL et al, 2015). Some of these results can be explained by the higher (P<0.001) SCD enzyme activity for the pairs oleic/ stearic and palmitoleic/palmitic acids (Table 5).…”

“…Another factor not yet studied in Brazil that has the potential to produce milk naturally enriched with FAs that are beneficial to human health, according to studies carried out in temperate regions, is the selective segregation of milk obtained during P.M. milking (FERLAY et al, 2010;SCHWENDEL et al, 2015;VIBART et al, 2017). To illustrate this, in the studies of Ferlay et al (2010), Rico et al (2014) and Schwendel et al (2015), lower levels of the hypercholesterolemic saturated FAs lauric, myristic and palmitic acid were obtained in milk that was acquired in the P.M. In addition, these authors also reported higher levels of FAs that are beneficial to human health (e.g., oleic, vaccenic and rumenic acids) in milk that was obtained in the P.M. Based on the results of these and other studies, it was hypothesized that in the present study, the butter produced from milk that was milked in the afternoon would have an FA composition with a higher nutritional quality.…”

Feeding dried distillers grains with solubles to lactating beef cows: impact of excess protein and fat on cow performance, milk production and pre-weaning progeny growth

“…Recent reports (Winterholler et al, 2012;Gunn et al, 2014) have indicated that milk fat in beef cows may be as low as 1.4% to 1.7%, however, it is possible that milk fat values in the present experiment were considerably lesser than expected because of incomplete emptying of the quarter at sampling. Nevertheless, it has been reported that within milking variation in milk components and fatty acids is low to none (Larsen et al, 2012;Rico et al, 2014). Milk lactose decreased from day 68 to 116 (day effect; P < 0.001) and milk solids increased from day 68 to 116 (day effect; P < 0.001) for both treatments.…”

Accuracy and application of milk fatty acid estimation with diffuse reflectance near-infrared spectroscopy

“…Soyeurt et al (2006), Rutten et al (2009) and Soyeurt et al (2011) presented results for predicting single FA and groups of different FA with MIR in the wavenumber range 1000 to 5000/cm. Rico et al (2014) took several subsamples during the milking process, analysed them in laboratory, and evaluated within milking fatty acids profiles during the milking process. The subsamples showed increased concentrations of short chain fatty acids (SCFA) during the main part of milking and less LCFA at the end of milking (Rico et al 2014).…”