Diet digestibility and ruminal parameters of Nelore cattle supplemented with soybean oil, vitamin E and selenium

Abstract

The increase of energy density of feedlot diets can be considered an effective strategy to reduce the slaughter age and consequently the emission of methane by cattle. Increased energy concentration of these diets can occur through the use of non-fiber carbohydrate sources rich in starch, situation commonly seen in the country. However, in recent years a growing interest in including lipid sources in feedlot diets has been observed. It has been reported in the literature the negative effect of fatty acids on the digestibility of carbohydrates, mainly on the digestibility of fibrous carbohydrates. However, the amount of fat that depresses the digestibility of these nutrients seems to be no consensus among researchers. As a strategy to increase the shelf life of beef, various trials has evaluated the effect of high doses of vitamin E supplementation on color and lipid oxidation of meat. However, there are few reports on the effect of supplementation on ruminal parameters. Also with the aim of increasing the shelf life of beef, other nutrient widely studied in recent years is the mineral selenium, since this is part of glutathione peroxidase, which exerts antioxidant effects in biological systems. However, few studies have reported the effect of dietary inclusion of selenium on ruminal parameters. Five Nelore steers will be used, with an average age of 20 months and an average initial weight of 350 kg rumen in a latin square design with five dietary treatments. The diets will corn silage as exclusive roughage and five different types of concentrates are used, representing the following treatments: 1-SLA (without additional fat); 2-6% of soybean oil; 3-6% soybean oil + Vitamin E; 4-6% soybean oil + Selenium; 5-6% soybean oil + Vitamin E + Selenium. Each of the five experimental periods will last for 19 days, totaling 95 days, fourteen being adapted to diets for five days to collect samples for the calculation of the variables. For determining the digestibility of diets after each adjustment period will be conducted total collection of feces for each animal for three consecutive days. To estimate microbial urine is collected over the same period, using funnels connected to collectors of polyethylene hose, through which urine is conveyed to a plastic container with a lid containing 200 mL of 20% H2SO4. At the end of 24 hours of each day of data collection, the urine will be weighed, homogenized and sampled, and stored in plastic vials -15ºC. Ruminal fluid collections will be held on the 4th day of each experimental period in order to determine the behavior of pH values, ammonia (NH3) and volatile fatty acids (VFA). times with the same procedures and to those for pH and ammonia, 50 ml of ruminal fluid for counting protozoa. (AU)