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Sugarcane is a strategic roughage source for milk production in the tropics, and its supplementation with plant oils offers great potential for obtaining milk enriched with beneficial fatty acids, such as oleic (cis-9 C18:1), vaccenic (trans-11 C18:1), and rumenic (cis-9, trans-11 CLA) acids. The aim of this study was to evaluate the milk fatty acid composition of cows fed 60% chopped sugarcane-based diets containing citrus pulp and 0.0% (control), 1.5%, 3.0% and 4.5% sunflower oil on a dry matter basis. Twelve multiparous Holstein x Gyr dairy cows with an average milk production of 17±5 kg day-1 and 96±25 days in milk were allocated in a triplicate 4 x 4 Latin square design. There was no effect of dietary treatment on milk production, but sunflower oil supplementation linearly reduced the milk fat content and yield. The milk fat contents of lauric (C12:0), myristic (C14:0), and palmitic (C16:0) fatty acids were linearly reduced with increasing sunflower oil levels. There was a quadratic effect on the milk fat oleic, vaccenic, and rumenic acid contents, while the concentrations of elaidic acid (trans-9 C18:1), trans-10 C18:1 and trans-10, cis-12 CLA linearly increased in response to sunflower oil inclusion. Diet supplementation with sunflower oil linearly reduced both the atherogenicity and thrombogenicity indices and linearly increased the ratio between hypo- and hypercholesterolemic fatty acids in milk fat. The inclusion of up to 4.5% sunflower oil in 60% chopped sugarcane-based diets improved the nutritional quality of milk fat from Holstein x Gyr dairy cows as a result of the increased content of oleic, rumenic and vaccenic acids, which are beneficial to human health, and the concomitant reduction of hypercholesterolemic lauric, myristic and palmitic acids. However, there was an increase in the milk content of trans-10 C18:1 and elaidic acid, which are associated with deleterious effects on cardiovascular health. Made available in DSpace on 2020-01-06T18:26:32Z (GMT). No. of bitstreams: 1 ArtigoFernandoMilkFattySemina.pdf: 469529 bytes, checksum: 0db34120b02af6cefb6fa8c543ead2c9 (MD5) Previous issue date: 2019

The aim of this study was to evaluate the performance of cows fed with a total mixed ration composed of elephant grass and a concentrate containing 0.0% (control), 1.5%, 3.0% or 4.5% soybean oil on a dry matter basis. The effect of milking time (morning versus afternoon) on butter fatty acid composition was also evaluated. Twelve multiparous Holstein x Gyr cows with an average milk production of 18.0±4.6 kg day-1 and 90±25 days in milk were used in a triplicated 4 x 4 Latin square experimental design with 15-day periods. Data were analyzed using mixed models. There was no effect of soybean oil supplementation on dry matter or neutral detergent fiber intake (P > 0.05). The fat-corrected milk yield linearly decreased (P=0.0109) and the milk protein yield linearly increased (P=0.0023) in response to soybean oil supplementation. The butterfat trans-9 C18:1, cis-9 C18:1, trans-10 C18:1, trans-11 C18:1, cis-9, trans-11 CLA and trans-10, cis-12 CLA content linearly increased (P < 0.05), whereas the C12:0, C14:0 and C16:0 content linearly decreased (P < 0.001) as the level of soybean oil in the diet increased. The butter produced from afternoon milk had a lower content of C16:0 and a higher content of cis-9 C18:1 (P < 0.05). The supplementation of elephant grass-based-diets with soybean oil and, to a small extent, the selective segregation of milk obtained from afternoon milking sessions are strategies that can be used to improve the fatty acid composition of butterfat. Made available in DSpace on 2019-09-03T19:10:14Z (GMT). No. of bitstreams: 1 SeminaButterfatty.pdf: 417802 bytes, checksum: c457e2ef4b36757e7a97192f3918f621 (MD5) Previous issue date: 2019