Effect of physically effective neutral detergent fiber and starch inclusion on eating behavior, ruminal metabolism and total tract digestibility in finishing cattle

Abstract

The objective of this study will be to evaluate the effect of physically effective neutral detergent fiber (peNDF) and starch inclusion fed to feedlot cattle on eating behavior, ruminal metabolism and total tract digestibility in finishing cattle. Eight Nellore yearling bulls (350 kg), previously fit with a cannula, will be housed in individual pens. The study will be conducted as a 4 × 4 Latin squares balanced for carry-over effects with 2 × 2 factorial arrangement of treatments, with the following factors: peNDF inclusion (low vs. high peNDF) and starch inclusion (22.5% vs. 45% of dry matter of the diet). Each period of the Latin square consisted of 21 days including 14 days without sampling and 7 days of sampling. The study will last 98 days. Eating behavior will be on day 15 of each experimental period. Ruminal motility will be measured for 6 h beginning on days 16 of each experimental period. Ruminal pH measurement will initiate on day 17 and will proceed for the subsequent 96 h of each experimental period. Ruminal digesta samples will be collected on day 17 and every 12 h thereafter with a 3 h offset on subsequent days until day 21 to measure short-chain fatty acids and ammonia. To evaluate the rate of ruminal NDF turnover, reticulo-ruminal contents will be completely evacuated 3 h after on days 20 and 3 h before feeding on day 1 of each experimental period. Ruminal digesta samples will be collected on day 19 of each experimental period to evaluate ruminal bacterial community composition. From days 17 to 21 of each experimental period, fecal samples will be collected to evaluate total tract nutrient digestibility using titanium dioxide as a marker to predict fecal output. Will be evaluated as variables: eating behavior and particle sorting, ruminal motility and fermentation, ruminal pool sizes and turnover rate, ruminal bacterial community composition and total tract nutrient digestibility.