Little Difference in Milk Fatty Acid and Terpene Composition Among Three Contrasting Dairy Breeds When Grazing a Biodiverse Mountain Pasture

Abstract

In the mountains, autochthonous and robust breeds are often used to valorize biodiverse grasslands. Along with their lower nutrient requirements, compared to specialized dairy breeds, they are expected to be better adapted to complex environments and valorize grasslands into dairy products of high quality. Therefore, the aim of the present study was to investigate the grazing selection of three contrasting dairy breeds on a biodiverse mountain pasture, and its consequences on milk fatty acid (FA) profile and prevalence of individual terpenes. A dual-purpose breed from the Italian Alps, the Valdostana Red Pied (Va), was compared to Montbéliardes (Mo), more specialized in milk production, and the highly specialized Holsteins (Ho). Diet selection was measured by scan-sampling, calculating selectivity indexes, and collecting simulated bites during two consecutive days in June (end of first grazing cycle) and July (second grazing cycle). Milk samples were collected at each milking during these experimental periods. Yield of milk and its fat and protein contents were measured. Milk FA and terpenes were analyzed by gas chromatographic methods. We tested the effects of breed, period and their interaction in a repeated mixed model, and calculated Pearson's correlations between behavioral data and milk FA as well as terpenes. The Va grazed less mature vegetation than Ho, but this difference was not sufficient to lead to a major breed effect on milk FA profile and prevalence of terpenes. However, the proportion of α-linolenic acid (C18:3 n-3) was always higher in the milk fat of Va than Ho (Mo were intermediary), but this without any correlation to grazing selection. This could be a consequence from a different metabolism concerning ruminal biohydrogenation, but must be further investigated. Finally, we confirmed previous studies that highlighted a link between milk quality and cows' grazing behavior, but here without differences among breeds. All cows adapted their behavior to the herbage evolution during the season, leading to higher proportions of unsaturated FA in July than June milks. Our study suggests that under mountain grazing conditions (biodiverse pasture and cows in late lactation), milk quality depends more on herbage composition than on cow breed.

Dietary and Animal Strategies to Reduce the Environmental Impact of Pastoral Dairy Systems Result in Altered Nutraceutical Profiles in Milk

“…Faster digesta outflow rate reduces rumen biohydrogenation rate of fatty acids (FA) [ 16 , 17 ], which in turn increases the supply of polyunsaturated fatty acids (PUFA) to the host animal and its products such as milk [ 17 , 18 ]. Subsequently, factors influencing ingestive and thereby digestive processes, like animal health status, diet, and their interaction [ 19 , 20 , 21 , 22 , 23 , 24 ], can alter the chemical composition and consequently nutraceutical characteristics of the final product for human consumption [ 25 ]. For example, Mangwe et al [ 26 ] reported that cows grazing PL produced milk with a greater content of PUFAs as compared to cows grazing a ryegrass sward [ Lolium perenne L. (RG)].…”

Quality and Functional Parameters of Fermented Milk Obtained from Goat Milk Fed with Broccoli and Artichoke Plant By-Products

“…In the present study silages had been stored for much longer times and no presence of the terpenoids reported in artichoke [ 61 ] were found in fermented milks. Terpenes may suffer further transformations, they may be directly transferred from the diet (on inhaled) to milk or may be further modified in the rumen (biohydrogenated and isomerized) [ 62 ]. Even during milk fermentation terpenes may undergo further modifications [ 57 ].…”

Characteristics of mountain vs. lowland dairy products

“…Koczura et al . (2021) demonstrated that the fatty acids composition of milk from cows in late lactation grazed in mountain areas where a great variety of plants are present depends more on the herbage composition than on the animal breed. The animals grazing on pastures with large biodiversity may prefer or dislike some of the plants, behaviour that can change depending on their nutritional needs and experience.…”

“…The animals grazing on pastures with large biodiversity may prefer or dislike some of the plants, behaviour that can change depending on their nutritional needs and experience. Thus, milk and derivates' fatty acids content could vary among animals grazed in the same conditions, in similar biodiverse areas (Koczura et al ., 2021). A paper presenting the effects of grazing and breed on milk fatty acids content evidenced that no considerable variations in fatty acids profile were obtained between various cow breeds, but the grazing time induced higher PUFA and lower SFA in milk samples (Niero et al ., 2021).…”