PHYSICALLY EFFECTIVE NEUTRAL DETERGENT FIBER AND STARCH INCLUSION FED TO FEEDLOT CATTLE ON SHORT CHAIN-FATTY ACIDS AND RUMINAL AMMONIA

Abstract

Insufficient fiber may increase the risk of nutritional disorders such as ruminal acidosis, negatively impacting health, and consequently growth performance of feedlot cattle. Forages are included at minimal levels when formulating finishing cattle diets due to lower digestibility and higher operational and economic costs than concentrates. 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 short chain-fatty acids and ruminal ammonia. 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. Samples of ruminal digesta will be collected through the cannula starting at 0700 hours on day 17 and every 12 h thereafter with a 3 h offset on subsequent days until day 21 (0700 h and 1900 h on day 17; 1000 and 2200 h on d 18; 1300 h on d 19; 0100 and 1600 hours on day 20; and at 0400 hours on day 21). Will be evaluated as variables: short chain-fatty acids production and ruminal ammonia concentration.