QUANTITATIVE-ANALYSIS OF NYCTEROHEMERAL EATING AND RUMINATING PATTERNS IN BEEF-CATTLE FED PELLETED CONCENTRATES WITH OR WITHOUT SUPPLEMENTAL ROUGHAGE

The effects of five diets on nycterohemeral pattern of chewing behavio ur were evaluated in 10 Hereford steers according to a replicated 5 x 5 Latin square design. Steers had ad libitum access to diets, fed once daily at 09:00 h and chewing behaviour was continuously measured for 4 d. Dietary treatments were: 1) traditional diet-80% pelleted concent rate (control) and 20% long timothy hay; 2) 80% control concentrate an d 20% alfalfa cubes; 3) 90% control concentrate and 10% alfalfa cubes; 4) a completely pelleted diet with corn cobs; 5) 80% textured concent rate and 20% long timothy hay. Spectral analysis of hourly time spent either eating or ruminating was performed using the finite Fourier tra nsform to decompose the 24-h total dispersion of chewing into 12 RC. N ycterohemeral patterns of time spent eating and ruminating different d iets were mainly explained by RC 1, 2 and 3. RC 1 was relatively more important than the others in explaining total daily dispersion of time spent eating traditional completely pelleted with corn cobs and textu red diets, while RC 1 and 3 presented similar relative importance for both alfalfa cube diets. Relative importance of RC 1 of time spent eat ing each diet was related positively to VI of diet DM (r = 0.88, P = 0 .047) and NDF (r = 0.92, P = 0.027). Nycterohemeral eating and ruminat ing patterns of individual steers were mostly explained by RC 1, 2 and 3. Relative importance of RC 11 and 12 of time spent ruminating were related positively to VI by steers of DM (respectively, r 0.81, P = 0. 004 and r = 0.63, P = 0.052) and NDF (respectively, r = 0.69, P = 0.02 7 and r = 0.67, P = 0.034). Overall, these relationships suggest that with once daily feeding of concentrate-based diets a larger VI is achi eved with a more important one main nycterohemeral eating period assoc iated to regular relative important two-hourly rumination periods, the se latter are probably enhancing continuity of digesta flow and nutrie nts uptake.