PSVI-29 - Using feeding behavior assessment to evaluate the effects of beef cattle dietary type or the presence of Saccharomyces cerevisiae

Abstract: The effects of live yeast and diet type (grower or finisher) offered to beef steers on feeding behavior were evaluated. Eight ruminally cannulated yearling beef steers (BW = 550 ± 20 kg) were used in a duplicated 4 × 4 Latin Square design and offered four dietary treatments to ad libitum intake, following a 2 × 2 factorial treatment arrangement: A) presence or not of live-yeast Saccharomyces cerevisiae (2 × 10¹⁰ CFU/g [CNCM I-1077]); and B) diet type. Diets (DM basis) contained 3% yellow-grease and mineral/vitamin supplement-adjusted. The grower (40% low-quality alfalfa-hay [LQ-hay], 35% steam-flaked corn [SFC], 20% wet corn gluten feed [WCGF]) and finisher (65% SFC, 20% WCGF, 8% LQ-hay) diets were offered once daily at 0700 h. Live-yeast cells or placebo (soybean meal) were delivered with gel capsules (0.25 g, as-is) twice daily directly into the rumen via ruminal-cannula. Four, 35 d periods were used, in which feeding behavior assessment was conducted by trained personnel on d 31 (continuous 24 h, every 5 min) while no other major management was performed during the evaluation. The time spent eating, ruminating (standing/laying), resting (stating/laying), active, and drinking were recorded, while chewing was estimated by adding rumination and eating time. The number of meals and time spent on each meal were also assessed. Data were analyzed using the GLIMMIX procedures of SAS, with animal considered as the experimental unit. The statistical model used the fixed effects of diet type, live-yeast presence, and the diet × live-yeast interaction, while square, period, and animal(square) were used as random effects. No diet × live-yeast interactions (P ≥ 0.17) or main effects of live-yeast (P ≥ 0.23) were observed for the variables measured. Feeding behavior was affected by diet type, in which steers offered a grower diet had greater time spent ruminating (341 vs. 231 min/d; P < 0.01), eating (154 vs. 105 min/d; P < 0.01), chewing (494 vs. 336 min/d; P < 0.01), and meal length (13 vs. 10 min/meal; P < 0.01), while less time resting (838 vs. 973 min/d; P < 0.01) compared to those offered the finisher diet. The time spent drinking (15 min/d; P = 0.29) and the number of daily meals (13 meals/d; P = 0.66) were not affected by treatments, while steers offered the finisher diet tended (P = 0.12) to be more active than those offered the grower diet (116 vs. 95 min/d). As expected, grower diets were more prone than finisher diets to stimulate feeding behavior variables of beef steers. Moreover, when directly introduced inside the rumen via ruminal cannula, the live yeast used seemed to not affect the feeding behavior of beef steers consuming a steam-flaked corn-based grower or finisher diet.