Abstract
Milk fatty acid (FA) profile can be divided into (1) de novo (C4-C14) that are synthesized in the mammary gland; (2) preformed (≥C18) that are absorbed from blood and originate from mobilized adipose tissues or dietary fat; and (3) mixed (C16), which have both origins. Our objectives were to describe the FA profile, as predicted using Fourier transform mid-infrared spectroscopy, of bulk tank milk from automated milking system (AMS) farms and to assess the association of management and housing factors with the bulk tank milk composition and FA profile of those AMS farms. The data used were collected from 124 commercial Canadian Holstein dairy farms with AMS, located in the provinces of Ontario (n = 68) and Quebec (n = 56). The farms were visited once from April to September 2019, and information were collected on barn design and herd management practices. Information regarding individual cow milk yield (kg/d), days in milk, parity, and the number of milking cows were automatically collected by the AMS units on each farm. These data were extracted for the entire period that the bulk tank milk samples were monitored, from April 2019 to April 2020 in Quebec and from August 2019 to May 2020 in Ontario. Across herds, milk yield averaged (mean ± standard error) 35.9 ± 0.4 kg/d, with 3.97 ± 0.01% fat and 3.09 ± 0.01% protein, whereas FA profile averaged 26.2 ± 0.1, 33.1 ± 0.1, and 40.7 ± 0.2 g/100 g of FA for de novo, mixed, and preformed, respectively. The FA yield averaged 0.34 ± 0.01, 0.44 ± 0.01, and 0.54 ± 0.01 kg/d for de novo, mixed, and preformed, respectively. Multivariable regression models were used to associate herd-level housing factors and management practices with milk production, composition, and FA profile. Milk yield was positively associated with using a robot feed pusher (+2.1 kg/d) and the use of deep bedding (+2.6 kg/d). The use of a robot feed pusher, deep bedding, and greater stall raking frequency were positively associated with greater yield (kg/d) of de novo, mixed, preformed, and de novo + mixed FA. Use of deep bedding was negatively associated with concentration of fat, de novo FA, mixed FA, and de novo + mixed FA, expressed in grams per 100 g (%) of milk. A wider lying alley width (≥305 cm) was associated with a greater concentration (g/100 g of milk) of de novo and de novo + mixed FA. Greater frequency of partial mixed ration delivery (>2×/d vs. 1 and 2×/d) was positively associated with a greater proportion (g/100 g of FA) of de novo, mixed, and de novo + mixed FA and negatively associated with the proportion of preformed FA. Overall, these associations indicated that bulk tank FA profile can be used as a tool to monitor and adjust management and housing in AMS farms.
Highlights
Understanding the factors that influence milk components is very important because milk is commonly marketed using a component pricing system, which defines the milk price based on the fat, protein, and other solids composition of the milk (Bailey et al, 2005)
This indicated that using only 1 group was predominant for lactating cows within the studied automated milking system (AMS) farms
The use of robot feed pusher and deep bedding were associated with a greater yield of milk, milk fat, de novo fatty acids (FA), mixed FA, de novo + mixed FA, and preformed FA
Summary
Understanding the factors that influence milk components is very important because milk is commonly marketed using a component pricing system, which defines the milk price based on the fat, protein, and other solids composition of the milk (Bailey et al, 2005). Bovine milk fat comprises 95 to 98% of triglycerides, which are formed through linkages of a glycerol backbone and 3 fatty acids (FA; Pegolo et al, 2016). The milk FA profile can be divided into the following 3 different origins: de novo, mixed, and preformed (Barbano, 2017). De novo (C4 to C14) and a fraction of the mixed FA (C16) are synthesized in the mammary gland from acetate and butyrate (Woolpert et al, 2017). Mixed FA can enter the mammary gland. Castro et al.: FATTY ACID PROFILE OF AUTOMATED MILKING FARMS cells as preformed FA taken up from the circulatory system (Ungerfeld et al, 2019). Preformed FA (≥C18) are absorbed from the bloodstream and can originate from the mobilization of adipose tissues or dietary fat (Palmquist et al, 1993)
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