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 behaviour were evaluated in 10 Hereford steers according to a replicated 5 × 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 concentrate (control) and 20% long timothy hay; 2) 80% control concentrate and 20% alfalfa cubes; 3) 90% control concentrate and 10% alfalfa cubes; 4) a completely pelleted diet with corn cobs; 5) 80% textured concentrate and 20% long timothy hay. Spectral analysis of hourly time spent either eating or ruminating was performed using the finite Fourier transform to decompose the 24-h total dispersion of chewing into 12 RC. Nycterohemeral patterns of time spent eating and ruminating different diets 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 textured diets, while RC 1 and 3 presented similar relative importance for both alfalfa cube diets. Relative importance of RC 1 of time spent eating 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 ruminating 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 = 0.027 and r = 0.67, P = 0.034). Overall, these relationships suggest that with once daily feeding of concentrate-based diets a larger VI is achieved with a more important one main nycterohemeral eating period associated to regular relative important two-hourly rumination periods, these latter are probably enhancing continuity of digesta flow and nutrients uptake. Key words: Beef cattle, nycterohemeral chewing, finite Fourier transform