The effects of feeding pelleted citrus pulp (PCP) as a natural antioxidant source on the performance and milk quality of dairy cows fed highly polyunsaturated fatty acid (FA) diets were evaluated. Four lactating Holstein cows were assigned to a 4×4 Latin-square. Treatments, on a dry matter (DM) basis, were i) control diet; ii) 3% soybean oil; iii) 3% soybean oil and 9% PCP and; iv) 3% soybean oil and 18% PCP. When cows fed on citrus pulp, the DM intake tended to decrease. The total tract apparent digestibility of DM and ether extract decreased when cows fed on the control diet compared to other diets. Cows fed PCP had higher polyphenols and flavonoids content and higher total ferric reducing antioxidant power (FRAP) in milk compared to those fed no pelleted citrus pulp. Cows fed 18% PCP showed higher monounsaturated FA and lower saturated FA in milk fat compared with cows fed the other diets. The lowest n-6 FA proportion was in milk fat from cows fed control. The present study suggests that pelleted citrus pulp added to 9% to 18% DM increases total polyphenols and flavonoids concentration, and the FRAP in milk.

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Soybean oil (SBO) is rich in polyunsaturated fatty acids (FA) and rumen bypass of SBO can contribute to increase the polyunsaturated FA proportion in milk fat. Citrus pulp (CPP) is a source of antioxidants but there is little information on the effects of CP administration on milk properties. This study was performed to determine the role of rumen microorganisms in the transfer of antioxidants from CPP into milk when cows receive SBO as a source of polyunsaturated FA. Four ruminally fistulated lactating Holstein cows were assigned to a 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments: (1) SBO administered in the rumen; (2) SBO infused in the abomasum; (3) SBO + CPP administered in the rumen; and (4) SBO + CPP infused in the abomasum. Product and site of administration had no effect on yield of milk components. Concentrations of total polyphenols and flavonoids, reducing power and production of conjugated diene (CD) hydroperoxides in milk were not affected by products, but infusion in the abomasum compared with administration in the rumen increased production of CD. Milk fat FA profile was not affected by products. However, cows infused in the abomasum compared with those administered in the rumen showed lower proportions of short-chain and monounsaturated FA and higher proportions of polyunsaturated, omega 3 and omega 6 FA in milk fat, which resulted in enhanced health-promoting index of milk. Administration of SBO and CPP (0.2 + 1.0 kg/d) in the rumen or the abomasum resulted in similar milk antioxidant properties, thus suggesting that the rumen microbes have little involvement in the metabolism of antioxidants from CPP.

The effects of farm, parity (PO)

The objective of this study was to evaluate the effect of adding ground soybeans and antioxidants to diet of buffaloes on intake, ruminal microbial production, total and ruminal digestibility of nutrients, and ruminal fermentation parameters. Four crossbred buffaloes with a mean weight of 506±29 kg were distributed in a 4×4 Latin square. Four diets were tested: control; diet with ground soybeans; diet with ground soybeans and supplementation with yerba mate; and diet with ground soybeans and supplementation with yerba mate and vitamin E. The addition of ground soybeans had negative effects on intake of dry matter, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber, as well as ruminal digestibility of neutral detergent fiber and total carbohydrates but did not influence total digestibility of nutrients. Yet, the ground soybeans diet increased the concentration of butyrate and microbial production in the rumen. The diet with ground soybeans supplemented with yerba mate decreased the concentration of acetate and increased the concentration of propionate and increased the efficiency of synthesis and the production of microbial protein in the rumen. There was a positive additive effect of vitamin E in the presence of yerba mate, enhancing the synthesis and production efficiency of microbial protein. Thus, the addition of ground soybeans and antioxidants to diet of buffaloes improves the efficiency of microbial protein synthesis and increases the production of butyrate, without, in general, altering the total digestibility of nutrients.

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