| dc.description.abstract | Grazing behaviour studies of night-kraaled and free grazed Boran (Bos indicus) and Hereford (Bos taurus) cattle were carried out in a wet season and a dry season.
Sixteen cows, 8 Borans and 8 Herefords, were individually observed and their activities recorded while on pasture with reference to grazing time, ruminating time and idle time
(walking, drinking and resting). The time animals spent resting, standing, and lying was also examined. The daily mean grazing time for night kraaled cows in the wet season was 6.05 + 0.32 hours for Boran cows and 7.b + 0.48 hours for the Herefords; and in the dry season the grazing time increased to 8.0 + 0.19 and 8.37 + 0.25 hours, for Boran and Hereford cows respectively. The free grazed cows spent a daily mean grazing time in the wet season of 8.17 + 0.25 hours for Borans and 8.19 + 0.37 hours for Herefords; and in dry season the time increased to 9.38 + 0.2 and 8.83 + 0.09 hours by Baran and Hereford cows respectively. Generally daily grazing was in two peaks, one in the mornings and the other in the afternoons, however, with free grazed cows, a smaller and more variable peak was observed between midnight and 4.00 hours.
Night kraaled Boran a~ Hereford cows ruminated 14.2 and 12.3 percent of total time at pasture respectively in the wet season Wheteas in dry season ruminating time
decreased to 9.6 and 9.5 perceht for kraaled Borans and Herefords respectively. For free grazed Boran cows ruminating time was 30 percent of the total time on pasture in wet
season 7.04 hours per day and this increased to 33 percent in dry season (7.68 hours per day). The free grazed Hereford cows ruminated 32 percent of the total time in the wet season (7.52 hours per day); and this rose to 35 percent in the dry season(B.12 hours per day). It was also shown that at least 74 percent of total ruminating time by free grazed cows occurred at night (19.00 hours to 7.00 hours).
There was a significant difference between breeds for lying and standing times (P< 0.05). The Herefords took longer standing than the Borans whereas Borans took longer time lying than the Herefords. Resting time was significantly longer in wet season than dry season. For grazing time significant interaction was observed between breed and
season (P< 0.05~; the Herefords grazed longer time than Borans in the wet season and the case was reversed in the dry season. Further interaction was observed between
breed and night management (P< 0.01); the Herefords grazed longer under kraaled management but shorter time under free grazed management. For ruminating time there was a significant interaction between breed and season (P< 0.05). Idle time, (resting, walking and drinking) was 29.6 and 21.8 percent of time on pasture for night kraaled
Boran and Hereford cows respectively in wet season. In dry season, idle time decreased for both kraaled Boran and Hereford cows to. 19.3.and 16.00 percent respectively. Free
grazed Boran cows in wet sea~on, idled 34.9 percent of the total time on pasture of which 62.6 percent happened at night; in dry season, idle time decreased to 27.9 percent. 64.4 percent of it occurred at night. Free grazed Hereford cows idled 32.9 percent of total time on pasture in wet season, and 58.4 percent of it occurred at night; and this decreased to 26.7 percent in dry season, with 62 percent at night.
The time cows spent walking while at pasture showed that Boran cows walked a longer than Herefords. There was no association of walking time with seasonal pasture changes
or management practice. The time cows spent drinking water was longer in dry season than wet season, and Herefords took longer than Borans. The proportion of the time at pasture that nightkraaled cows spent drinking. water, ranged between 0.98 to 1.94
percent, whilst free grazed cows were between 0.4 to 0.8 percent.
Night kraaled Boran and Hereford cows grazed 55 percent and 65 percent of total time on pasture respectively, during the wet season. In the dry season the proportions increased
to 71.07 percent for Borans and 74 percent for Herefords. The grazing time/ruminating time ratio was 1.2 and 1.1 for free grazed Borans and Herefords respectively, in both
seasons. The ratios for night kraaled cows (during time out of kraals only) were 3.85 and 5.35 for Borans and Herefords respectively in wet season. But during dry season the
ratios increased,to 7.40 for Borans and 7.42 for Herefords. | en |
