Producing natural functional and low-carbon milk by regulating the diet of the cattle—The fatty acid associated rumen fermentation, biohydrogenation, and microorganism response

Abstract

Conjugated linoleic acid (CLA) has drawn significant attention in the last two decades for its various potent beneficial effects on human health, such as anticarcinogenic and antidiabetic properties. CLA could be generally found in ruminant products, such as milk. The amount of CLA in ruminant products mainly depends on the diet of the animals. In general, the fat content in the ruminant diet is low, and dietary fat supplementation can be provided to improve rumen activity and the fatty acid (FA) profile of meat and milk. Especially, dietary 18-carbon polyunsaturated FA (C18 PUFA), the dominant fat source for ruminants, can modify the milk FA profile and other components by regulating the ruminal microbial ecosystem. In particular, it can improve the CLA in milk, intensify the competition for metabolic hydrogen for propionate producing pathways and decrease methane formation in the rumen. Therefore, lipid supplementation appears to be a promising strategy to naturally increase the additional nutritional value of milk and contribute to lower methane emissions. Meanwhile, it is equally important to reveal the effects of dietary fat supplementation on rumen fermentation, biohydrogenation (BH) process, feed digestion, and microorganisms. Moreover, several bacterial species and strains have been considered to be affected by C18 PUFA or being involved in the process of lipolysis, BH, CLA, or methane emissions. However, no review so far has thoroughly summarized the effects of C18 PUFA supplementation on milk CLA concentration and methane emission from dairy cows and meanwhile taken into consideration the processes such as the microorganisms, digestibility, rumen fermentation, and BH of dairy cattle. Therefore, this review aims to provide an overview of existing knowledge of how dietary fat affects rumen microbiota and several metabolic processes, such as fermentation and BH, and therefore contributes to functional and low-carbon milk production.

Effects of Dietary Fat Level of Concentrate Mix on Growth Performance, Rumen Characteristics, Digestibility, Blood Metabolites, and Methane Emission in Growing Hanwoo Steers

“…Onetti et al [ 24 ] reported that supplementing animal fats to corn silage increased the proportion of propionate in Holstein cows. These findings were consistent with a meta-analysis and review paper by Patra [ 11 ] and Sun et al [ 25 ], which reported that increasing dietary fat levels were associated with increased propionate and decreased butyrate and the A:P ratio. Unsaturated fatty acids in the fat content of the feed decrease the populations of methanogens and protozoa in the rumen [ 26 ].…”

“…Furthermore, as higher fat levels led to increased propionate production, it is likely that H 2 in the rumen was primarily utilized for propionate production rather than for the biohydrogenation of UFAs. Sun et al [ 25 ] have suggested that due to the limited availability of H 2 for the biohydrogenation of UFAs in the rumen, the primary influence of dietary fat on CH 4 emissions would likely be its direct impact on methanogens and rumen microbial population.…”

In vitro fermentation with inoculated goat rumen to evaluate the degradation of diets supplemented with three levels of protected palmitic acid

“…In this study, methane production did not decrease with the increase in protected PA. The lack of effect is because it is a SFA, and it cannot capture H 2 ions through the biohydrogenation process (Sun et al 2022). The data from this study indicate that diets with SFA such as protected PA do not have total protection; part of the PA is available and used by rumen microorganisms and has an effect of decreasing the GP and consequently decreases the degradability of DM and OM (Buccioni et al 2012).…”

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

“…Consequently, numerous studies have focused on enhancing the value of animal products, particularly by increasing the concentration of FAs in milk and dairy products that have favorable effects on human health [13][14][15][16][17]. From a nutritional perspective, a more favorable FA profile would entail a reduced proportion of SFAs and an increased proportion of UFAs, with particular focus on n-3 PUFAs, along with a lower n-6/n-3 ratio [18].…”