Milk and Conjugated Linoleic Acid: A Review of the Effects on Human Health

Effect of dietary protein source and Saccharina latissima on nutritional and safety characteristics of milk

BACKGROUND

Wheat distillers' grains (WDG) and seaweeds are recommended as alternative protein sources and enteric methane mitigators in dairy cow diets, respectively, but little is known about their impact on milk quality and safety. In the present study, 16 cows in four 4 × 4 Latin squares were fed isonitrogenous diets (50:50 forage:concentrate ratio), with rapeseed meal (RSM)-based or WDG-based concentrate (230 and 205 g kg-1 dry matter) and supplemented with or without Saccharina latissima.

RESULTS

Replacement of RSM with WDG enhanced milk nutritional profile by decreasing milk atherogenicity (P = 0.002) and thrombogenicity (P = 0.019) indices and the concentrations of the nutritionally undesirable saturated fatty acids - specifically, lauric (P = 0.045), myristic (P = 0.022) and palmitic (P = 0.007) acids. It also increased milk concentrations of the nutritionally beneficial vaccenic (P < 0.001), oleic (P = 0.030), linoleic (P < 0.001), rumenic (P < 0.001) and α-linolenic (P = 0.012) acids, and total monounsaturated (P = 0.044), polyunsaturated (P < 0.001) and n-6 (P < 0.001) fatty acids. Feeding Saccharina latissima at 35.7 g per cow per day did not affect the nutritionally relevant milk fatty acids or pose any risk on milk safety, as bromoform concentrations in milk were negligible and unaffected by the dietary treatments. However, it slightly reduced milk concentrations of pantothenate.

CONCLUSION

Feeding WDG to dairy cows improved milk fatty acid profiles, by increasing the concentrations of nutritionally beneficial fatty acids and reducing the concentration of nutritionally undesirable saturated fatty acids, while feeding seaweed slightly reduced pantothenate concentrations. However, when considering the current average milk intakes in the population, the milk compositional differences between treatments in this study appear relatively small to have an effect on human health. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Impact of Using Oilseed Industry Byproducts Rich in Linoleic and Alpha-Linolenic Acid in Ruminant Nutrition on Milk Production and Milk Fatty Acid Profile

Milk contains more than 400 different fatty acids, some of which play a positive role in promoting human health. The profile of fatty acids in milk can be enhanced by providing animals with plant-based resources that possess feeding characteristics adequate for favorable changes in the fatty acid composition and increasing healthy fatty acids in milk. This review summarizes the available 41 research studies on the utilization of oilseed industry byproducts rich in linoleic acid (hemp, pumpkin, sunflower) and alpha-linolenic acid (camelina and linseed) in dairy cow, sheep, and goat nutrition; their impact on milk production characteristics; and potential to improve fatty acid composition of milk through the diet. This review illustrates that incorporating byproducts into the diet for dairy ruminants generally does not have any adverse effects on both milk production and composition. A similar trend of improvement in milk fatty acid profile was observed when ruminants were fed diets supplemented with camelina, linseed, and sunflower byproducts, while no significant changes were noted with pumpkin byproducts. Hempseed byproducts showed potential for use as an alternative ingredient in dairy ruminant diets. Nevertheless, more in-depth research investigating the inclusion of selected byproducts is required before valid conclusions can be drawn regarding their value.

Rumen microbial community and milk quality in Holstein lactating cows fed olive oil pomace as part in a sustainable feeding strategy

The use of alternative feed ingredients from the Agro-industry could be an efficient tool to improve the sustainability of dairy cow production. Since the richness in polyphenols, olive oil pomace (OOP), produced during olive oil milling, seems a promising by-product to ameliorate milk's nutritional value. The aim of this study was to test the use of OOP produced by means of a new technology (biphasic with stone deprivation) in dairy cow feeding strategy to evaluate the effect on animal performances, rumen microbiota, biohydrogenation processes and milk quality by a multidisciplinary approach. Forty multiparous Italian-Friesian dairy cows, at middle lactation, were randomly allotted into two homogenous groups and fed respectively a commercial diet (CON) and the experimental diet (OOPD) obtained by adding OOP to CON as partial replacement of maize silage. The two diets were formulated to be isoproteic and isoenergetic. The same diets were tested also in an in vitro trial aimed to evaluate their rumen degradability (% DEG). The dietary supplementation with OOP did not affect DM intake, rumen % DEG and milk production. The milk's nutritional quality was improved by increasing several important functional fatty acids (FAs; i.e., linoleic acid, conjugated linoleic acid, oleic acid, vaccenic acid). This finding was related to a decrease in rumen liquor biohydrogenation rate of unsaturated FAs. The stochiometric relation between volatile FA production in the rumen and methanogenesis suggested that OOP lowers the methane potential production (CON = 0.050 mol/L vs OOPD = 0.024 mol/L, SEM = 0.005, P = 0.0011). Rumen microbiota and fungi community did not be strongly altered by OOP dietary inclusion because few bacteria were affected at the genus level only. Particularly, Acetobacter, Prevotellaceae_UCG-004, Prevotellaceae_UCG-001, Eubacterium coprostanoligenes, Lachnospira, Acetitomaulatum, Lachnospiraceae_NK3A20 group were more abundant with OOPD condition (P < 0.05). Data reported in this study confirm that the use of OOP in dairy cow feeding can be an interesting strategy to improve milk nutritional quality increasing functional FA content without compromising the rumen degradability of the diet or causing strong perturbation of rumen ecosystem and maintaining animal performances.

Utilization of Vaccinium meridionale S. pomace as an eco-friendly and functional colorant in Greek-style yogurt

Greek-style yogurt (GSY) has gained reputation as a healthy food because of its high protein content. Vaccinium meridionale S. is a bilberry with a high content of bioactive phytochemicals, whose vaccinium meridionale pomace (VMP) represents about 20% of the fruit weight. However, this byproduct is normally discarded as waste. In this study, VMP was used as a natural colorant in GSY. Coloring before or after the fermentation process resulted in significant increase in anthocyanins, total phenolics content, antioxidant activity, conjugated linoleic acid, and sensory acceptance. These results indicate that VMP is a potential natural, eco-friendly, and functional colorant to improve the nutritional value of GSY. PRACTICAL APPLICATION: Vaccinium meridionale pomace is a waste product with potential to be utilized as a natural, eco-friendly, and functional colorant to obtain value-added Greek-style yogurt. Besides providing bioactive compounds and natural color, this pomace improves the nutritional value, sensory acceptance, and functional properties of Greek yogurt.