Ruminal variables in steers fed with Tifton 85 (Cynodon Spp) hay with different particle sizes

Abstract

The ammonia nitrogen (N-NH3) concentration and the pH were determined with the objective of evaluating the effect of different particle sizes (5, 7, 10mm and whole) of Tifton 85 hay in the diet of Holstein steers, with average live weight of 300kg and age of 20 months. A completely randomized design, with four replicates, in a split-plot arrangement was used. The plots were the experimental treatments (5, 7, 10mm and whole hay) and the subplots were the times of collection (0, 2, 4, 6, 8h). The use of diets including hay with particle sizes of 5mm and whole, did not affect (P>0,05) the ruminal pH; average values were 6.14 and 6.61, respectively. A linear reduction in the ruminal pH was verified in the steers fed on diets constituted by 10mm particles. For the diets including Tifton hay with particle size of 7mm, it was observed a quadratic effect, where the minimum pH (5.39) was observed 8:00 h after the feed was furnished. Concentrations of N-NH3 were affected by collection time in a quadratic way. Maximum concentrations of N-NH3, 15.55, 15.83, 18.32, 12.0 mg/100 mL, were observed at 4:28, 3:58, 2:99 and 2:80h after feeding, for the diets including Tifton 85 hay with 5, 7, 10mm and whole particle sizes, respectively. It was concluded that all diets allowed normal nycterohemeral patterns of fermentation.