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 com este estudo avaliar os efeitos do uso de diferentes fontes de ácido graxo ômega 6 na dieta de vacas leiteiras no período de transição e início da lactação sobre o desempenho produtivo e bioquímico em vacas da raça Holandesa. As vacas foram alimentadas com as seguintes dietas: 1) controle, 2) óleo de soja refinado, 3) os sais de cálcio de ácidos graxos insaturados (Megalac-E). As dietas foram formuladas para atender às exigências nutricionais das vacas durante o período de pré-parto e pós-parto, dentro de cada grupo experimental. As dietas experimentais afetaram o consumo de matéria seca, o peso corporal, escore de condição corporal e equilíbrio de energia no período pós-parto. As dietas experimentais não afetaram os parâmetros bioquímicos no soro: glicose, proteína total, albumina, uréia, uréia sérica, colesterol total, HDL-colesterol, ácidos graxos não esterificados, β-hidroxibutirato, aspartato aminotransferase, γ-glutamil transferase, fosfatase alcalina, também não sendo observadas diferenças entre os contrastes analisados. As fontes de ácido graxo ômega 6 não influenciaram diretamente o bioquímico de vacas leiteiras no período de transição.

This study aimed to evaluate the effects of using different lipid sources in diets for dairy cows during the transition period and early lactation on productive performance and physiological parameters in Holstein cows. The cows were fed with the following diets: 1) control; 2) Refined soybean oil; 3) Calcium salts of unsaturated fatty acids (Megalac-E). Diets were formulated to meet the nutritional requirements of cows during the pre-partum and postpartum period. The experimental diets affected the dry matter intake, body weight, body condition score, and energy balance in the postpartum period. The experimental diets did not affect the biochemical parameters in serum: glucose, total protein, albumin, urea, serum urea nitrogen, total cholesterol, HDL-cholesterol, non-esterified fatty acids, β-hydroxybutyrate, aspartate aminotransferase, γ-glutamyl transferase, alkaline phosphatase, also not being observed differences between the contrasts analyzed. The lipid sources soybean oil and calcium salts not directly influence the plasmatic physiological parameters of dairy cows in the period transition. But, fat supplementation in the transition period resulted in a better metabolic status and productive performance, mainly improving energy balance post-partum

The objective of this study was to evaluate the utilization of different sources of unsaturated long-chain fatty acids in diets for dairy cows during the transition period and early lactation on the milk fatty acid profile and composition of the protein fraction. Thirty-six Holstein cows were divided into three groups, fed the following diets: control (C); soybean oil (SO); and calcium salts of long-chain unsaturated fatty acids (CS). The milk samples utilized for analysis were obtained weekly from parturition to twelve weeks of lactation; each one of the samples originated from two daily milkings. Milk composition and total nitrogen, non-protein nitrogen and non-casein nitrogen levels were analyzed. The cows receiving the diet with calcium salts had lower concentrations of non-protein nitrogen (%CP) in milk compared with the animals fed the diet with soybean oil. There was a decrease in concentration of medium-chain fatty acids C12-C16, and a concomitant increase in concentrations of long-chain fatty acids >C18 in milk fat for the animals fed the diets CS and SO when compared with diet C. Soybean oil and CS diets increased milk-fat concentrations of the acids C18: 1 trans-11, C18: 2 cis-9, trans-11 and C18: 2 trans-10 cis-12 in relation to diet C. The utilization of sources of long-chain fatty acids in the diet of dairy cows increases the biological value of milk in early lactation due to higher concentrations of specific fatty acids such as CLA C18: 2cis-9, trans-11.