Enterolactona e ácidos graxos poli-insaturados no leite de vacas alimentadas com casca e óleo de linhaça

Abstract

Three studies were conducted to evaluate the transfer of lignans (enterolactonag EL) and polyunsaturated fatty acids (PUFA) from the diet into milk of lactating dairy cows fed with flax oil and/or hulls. Moreover, another objective was to determine the role of rumen on lignan metabolism. In non-ruminants, lignans are metabolized by intestinal microbiota but there was no infonnation on the metabolism of lignans in ruminants. The first study evaluated the role of ruminal microbiota and the effects of flax oil on in vivo metabolism of flax hull lignans and EL concentrations in biological fluids. Four ruminal cannulated Holstein cows with 575 kg of BW and 92 DIM were used in a 4 >< 4 Latin square design with four 21-d periods. Treatments were: l) flax oil and flax hulls administered in the rumen (RUM/RUM); 2) flax oil and flax hulls infused in the abomasum (ABO/ABO); 3) flax oil administered in the rumen and flax hulls infused in the abomasum (RUM/ABO); and 4) flax oil infused in the abomasum and flax hulls administered in the rumen (ABO/RUM). The site of administration of flax oil and flax hulls did not affect ruminal concentrations of EL. Concentrations of EL in urine, plasma and milk were higher in cows that received flax hulls in the rumen compared to those that received flax hulls in the abomasum. Therefore, this study showed that ruminal microbiota plays an important role in flax lignan metabolism. The second study was conducted to evaluate the site of administration (rumen and/or abomasum) of flax hulls and/or oil on ingestion, total digestibility, milk yield and composition, and milk fatty acid profile of dairy cows. Treatments were: l) flax oil and flax hulls administered in the rumen (RUM/RUM); 2) flax oil and flax hulls infused in the abomasum (ABO/ABO); 3) flax oil administered in the rumen and flax hulls infused in the abomasum (RUM/ABO); and 4) flax oil infused in the abomasum and flax hulls administered in the rumen (ABO/RUM). Intake of DM was different among treatments. Total digestibility of DM was lower for RUM/RUM and RUM/AB() treatments, and NDF and ADF digestibilities were lower on the RUM/RUM treatment. Yield of 4% FCM decreased when flax products were administered in the rumen but milk composition was similar among treatments. Concentration of SCFA in milk fat on RUM/RUM treatment was reduced by 26 % when compared to other treatments. The RUM/RUM treatment resulted in the highest concentration of octadecenoic acid in milk fat. Proportion of cis9,transl l-CLA in milk fat was higher with ruminal than abomasal administration of flax oil. Although RUM/RUM treatment increased the n-6:n-3 FA ratio in milk fat compared to other treatments, ratios were lower than 4: 1, which is ideal for human health. The third study was perfomied to evaluate the effects of feeding flax hulls and increased amount of flax oil infused in the abomasum on EL and PUFA concentration in milk of cows and to evaluate the effect of the presence of flax oil in the small intestine on lignan metabolism. Six multiparous Holstein cows averaging 650 kg of BW and 95 DIM were used in a 6 X 6 Latin square design with a 2 X 3 factorial arrangement of treatments. The six treatments were two different diets (CON vs FHU) and three levels of flax oil infused in the abomasum (0, 250 and 500 g/d), with six 21-d experimental periods. Feeding the FHU ration and with the highest amount of flax oil infused in the abomasum decreased DMI of cows. Feeding the FHU ration increased apparent digestibility of DM, CP and EE, probably as a result of partial replacement of cracked com grain and soybean meal by flax hulls. Feeding the FHU ration decreased milk yield, and, subsequently yields of protein, fat, total solids and lactose (kg/d). Cows fed FHU ration had lower concentrations of SCFA, MCFA, SFA and n-6, and higher concentrations of LCFA, MUFA, PUFA and n-3 in milk fat, which resulted in a lower, n-6:n-3 FA ratio in milk fat of cows. Concentrations of EL in plasma, milk and urine were higher for cows fed the FHU ration. Amount of flax oil infused in the abomasum had no effect on EL concentration in milk of cows.