The objective of this study was to evaluate the influence of unsaturated fatty acids in diets for dairy cows during the transition period and early lactation on intake, digestion and nutrient balance. Thirty-six multiparous and pregnant Holstein cows were randomly distributed to receive one of the experimental diets in the period from 35 days before the expected date of parturition to 84 days post-partum. Diets were fed as a total mixed ration and were as follows: control (C); soybean oil (SO), based on inclusion of 30 g/kg (DM basis); and calcium salts of unsaturated fatty acids (CS), based on inclusion of 30 g/kg (DM basis). Pre-partum dry matter intakes (DMI) of cows fed C, SO and CS were 11.9, 9.5 and 9.6 kg/d, respectively. Post-partum DMI was affected by experimental diets (18.5, 15.0 and 17.4 kg/d for C, SO and CS, respectively). The energy balance in the transition period of animals fed CS was 4.41 Mcal/d higher than cows fed SO and 1.3 Mcal/d higher than cows fed C. Supplementing cows with unsaturated fatty acid sources is a strategy for dairy cows in the transition period.

Objetivou-se avaliar o uso de fontes de ácidos graxos insaturados nas rações de vacas leiteiras sobre o balanço de nutrientes e o perfil de ácidos graxos do leite. Foram utilizadas 12 vacas Holandesas no terço médio de lactação (média de 128 dias) e (580 ± 20 kg de peso; média ± DP) com produção média de leite de 25kg/dia distribuídas aleatoriamente em três quadrados latinos balanceados 4 x 4 alimentadas com as seguintes dietas: controle (C); óleo de soja refinado; (OS); grão de soja integral (GS) e; sais de cálcio de ácidos graxos insaturados (SCAG). A produção de leite obtida foi de 26,6; 26,4; 24,1 e 25,7kg/dia para as dietas CO, OS, GS e SCAG respectivamente. As vacas alimentadas com a dieta GS produziram menos leite (1,95kg/dia), gordura e lactose em relação às vacas alimentadas com as dietas OS e SCAG. As vacas alimentadas com a dieta SCFA, apresentaram menores concentrações de nitrogênio uréico no sangue, leite, urina (g/dia), maior eficiência do uso de nitrogênio e consumo de energia em relação a dieta OS. As vacas alimentadas com as dietas contendo fontes de ácidos graxos insaturados demonstraram maiores concentrações no leite dos ácidos graxos C18:2 cis-9, trans-11 e C18:1, trans-11, em relação as vacas alimentadas com a dieta CO. O uso de grão de soja integral e óleo de soja promovem maior eficiência dos processos digestivos e aumentam as concentrações de ácidos graxos insaturados no leite de vacas leiteiras.

The objective was to evaluate the effect of unsaturated fatty acid sources supplementation on nutrients balances and milk fatty acid profile of mid lactation dairy cows. Twelve Brazilian Holstein cows in the mid lactation (mean of 128 days) and (580 ± 20kg of weight; mean ± SD) with milk yield of 25kg/d were assigned randomly into three 4 x 4 Latin square, fed the following diets: control (C); refined soybean oil; (SO); whole soybean raw (WS) and; calcium salts of unsaturated fatty acids (CSFA). Milk yield was 26.6; 26.4; 24.1 and 25.7 to the diets CO, SO, WS and CSFA respectively. Cows fed the WS treatment produced less milk (1.95kg/d of milk), fat and lactose than did cows fed the SO and CSFA. Cows fed the CSFA treatment showed less blood, urine (g/d) concentrations of N more energetic efficiency and intake of energy than did cows fed the SO treatment. Cows fed the unsaturated fatty acids sources showed more C18:2 cis-9, trans-11 CLA and trans-C18:1 FA concentration in milk than did cows fed the CO treatment. Diets with whole soybeans and soybeans oil provide more efficient digestive processes, and increase milk composition of unsaturated fatty acids.