Ingestive Behavior of Young Grazing Nellore Bulls Supplemented with Sources of Non-Protein \Nitrogen during the Dry Season at Two Different Times

Cattle in a hot climate have two peak grazing times, early morning and late afternoon, so feeding a supplement in early morning may interfere with pasture consumption. A controlled-release urea may synchronize ruminal ammonia and energy availability compared to urea. The objective of this study was to evaluate the ingestive behavior of grazing cattle in the dry season at low latitude, receiving supplements containing urea or Optigen® (a controlled- release urea) at 7:00 am or 1:00 pm. One hundred and twenty young Nellore bulls with body weight of 228±39 kg and 12 months old were used, 5 in each of 20 paddocks of 3 ha each. The pasture was Brachiaria brizantha cv. Marandu. The duration was 98 days, 14 days of adaptation and three periods of 28 days. The grazing time and the time at the supplement trough during daytime (6:00 to 17:50), nighttime (18:00 to 05:50) and total were evaluated by trained people at 10-minute intervals on 1 day in each period. The 4 treatments were a factorial design of 2 feeding times x 2 urea sources, applied in a randomized complete block design. Statistical analysis was by the MIXED procedure of SAS, version 9.2 (SAS, 2008), considering block as a random variable. There was no influence of supplementation time, urea sources or their interaction on the grazing time or the trough time during daytime, nighttime or total (P>0.10). The grazing time was reduced by 92 minutes (P<0.01) in the third period compared to the first two and the trough time was lower in the first period (33 minutes; P=0.03) than in the second (50 minutes) and in the third (65 minutes), but there were no interactions of period with treatment. These changes are presumably a response to increasing pasture growth as the seasonal rains began. In conclusion, under the conditions of this study, the time of supplementation and the urea sources do not alter the ingestive behavior of young bulls.

Time spent: daytime grazing (DG), nighttime grazing (NG), daytime trough (DT), nighttime trough (NT) per 24 hours

Source(S)	Opitgen®		Urea		SE	P value
Time (T)	Morning	Afternoon	Morning	Afternoon		S	T	S*T
DG, min.	320	342	327	312	14.3	0.43	0.80	0.19
NG, min.	199	191	195	180	20.2	0.63	0.46	0.81
DT, min.	52.7	39.2	50.0	43.1	7.59	0.94	0.19	0.66
NT, min.	3.33	3.44	4.78	1.36	1.72	0.84	0.32	0.29

See more of: Poster Session: Forages and Pastures
See more of: Forages and Pastures

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