Chitosan inclusion in diets of Holstein cows increase unsaturated total fatty acids and conjugated linoleic acid on milk fat profile

Chitosan is a natural antimicrobial agent which can to modify the biohydrogenation of unsaturated fatty acids (FA) in rumen. The aim of this study was to evaluate the effects of chitosan addition on milk FA profile in dairy cows diets containing or not raw soybeans. Twenty four Holstein cows (140.7 ? 37.1 days in milk, 35.0 ? 5.4 kg/day of milk yield and 619.0 ? 81.1 kg of BW) were used in a replicated 4 x 4 Latin square design with 23 d periods, with 15 d of adaptation and 8 d for data collection. Treatments arrangement was a 2 x 2 factorial design with two levels of chitosan (0 and 4 g/kg of dietary DM) and two levels of raw soybeans (0 and 140 g/kg of dietary DM). The forage source used was maize silage, accounting for 50% of diet DM basis. The animals were milked twice a day and milk samples were proportionally collected of each milking at days 17 and 18, and mixed to form a composite sample for subsequent analysis. This samples were centrifuged (initially at 17,800 x g for 30 min and then at 19,300 x g for 20 min, both at 4 ?C) for milk fat extraction and the separated fat (700 - 800 mg) was submitted for the methylation process of FA. The FA methyl esters prepared were quantified using a gas chromatography (GC Shimatzu 2010 with automatic injection). Individual FA were calculated and expressed as a proportion of the total measured FA (g/100 g FA). The data were analyzed using the MIXED procedure of SAS where the means were adjusted by LSMEANS. No interactions were observed (P > 0.05) between chitosan and raw soybeans. Chitosan, independently of raw soybeans inclusion, increased (P < 0.05) total monounsatured FA (MUFA) (2.3 %; 27.23 vs 26.61 g/100 g) and total polyunsaturated FA (PUFA) (3.4%; 3.65 vs 3.53 g/100 g), and decreased (P < 0.05) total saturated FA (SFA) (1.2%; 64.97 vs 65.73 g/100 g) and the SFA / (MUFA + PUFA) ratio (3.4%; 2.13 vs 2.20). Furthermore, chitosan increased (P < 0.001) the content of c9 t11 CLA (12.9%; 0.35 vs 0.31 g/100 g), an important isomer of conjugated linoleic acid (CLA) by health-promoting in humans. In conclusion, chitosan modify the ruminal biohydrogenation and intermediates FA production, enhancing the milk FA profile in dairy cows.