Effect of carbon emission reducing diet on bovine milk properties

This study was aimed to investigate the effect of methane emission reducing diet on composition and processing properties of bovine milk. Treatment diets included supplementation of cottonseed oil (800 g/d, CSO), A. mearnsii- condensed tannin (400 g/d, TAN) or their combination (CPT) to a control diet, consisting of 6.0 kg dry matter concentrates and ad libitum hay. In contrast to the TAN diet, the CSO and CPT diets decreased milk fat content and the proportion of saturated fatty acids but increasing proportions of monounsaturated and polyunsaturated fatty acids. The TAN diet had no effect on feed intake, milk yield and milk protein content, but it depressed the yields of protein and lactose. All supplemented diets did not affect protein content or composition, nitrogen content, or casein to total protein ratio of the resulting milk. All treatment diets did not alter gelation time (GT), storage modulus (G′), loss modulus (G″), loss tangent (tan δ), permeability, water holding capacity and hardness of acid- and rennet-induced gels. These diets had a marginal effect on fat and protein recoveries, cheese yield, composition, textural properties and organic acid production of the cheeses. All cheeses showed comparable primary and secondary proteolysis compared to that of control. Degrees of primary and secondary proteolysis kept increasing throughout ripening time. Cheeses manufactured from milk of cows fed a diet containing cottonseed oil had higher concentration of medium- and long-chain fatty acids (FA) but lower in short-chain FA. In contrast, supplementation of condensed tannin in the diet resulted in cheese with comparable FA composition to that of control. Throughout ripening time, the concentration of short-, medium-, and long-chains FAs tend to remain stable. A further study is required to establish the effect of diet supplementation on lipolysis of cheeses. Furthermore, dietary treatments can be used to produce Cheddar cheese with a new property without compromising consumer preferences for appearance, firmness, flavour, aroma, and overall acceptance. Results support that these supplemented diets could be used to mitigate methane emission without altering milk processing properties such as milk coagulation and Cheddar cheese making properties.