Abstract:
A study was conducted to assess forage mass, botanical composition, nutritive value of herbaceous vegetation, grazing behavior, forage selectivity and performance of co-grazing sheep, goats, cattle and camels with initial body weights (BW) of 20.6±2.09, 16.6±0.97, 96.8±3.43 and 162.3±21.28 kg, respectively. Grazing lasted 16 weeks, using 6 growing animals from each animal species (AS). Animals co-grazed 6 ha of grazing area (G) with diverse plant species. Four enclosures (E) each 25 m2 were made as control. Forage measures were performed from G and E at the start, middle and end of the grazing period. Botanical composition was assessed as the contribution of dominant grass (Chloris radiata), other grasses and forbs. Grazing behavior observations for position and activity were made during day light. In weeks 4, 8 and 14 hand-plucked samples of forages similar to that being selected by AS were sampled for laboratory evaluation. BW was measured at the beginning and at 28-days interval, and average daily BW gain (ADG) was calculated. Following the grazing period, all animals were used for digestibility trial using 2 dietary regimes (DR) in a 2x4 factorial arrangement in switch over design. The DR were natural pasture hay (H) fed ad libitum alone or supplemented with a concentrate (C; 55% wheat bran, 28% noug seed cake and 17% wheat short) at a rate 1.2% of BW. The AS were grouped into two and received the two DR in two periods of digestibility measurement. Each period lasted 15 days for adaptation and 7 days for measurement. Forage mass at the start and middle ranged 2001 to 2351 kg/hay and were similar between G and E, while values for G was lower at the end (1496 vs 1918 kg/ha; SEM=68.8) of the grazing period. The contribution of Chloris radiata, other grasses and forbs for E was unaffected by grazing period (P > 0.05). For G, only percentage of forbs decreased by 37% and Chloris radiata increased by 31% at the end compared to the start (P < 0.05). Chemical composition of forages did not differ much between G and E, reflecting less impact of co-grazing. The CP content and IVDMD decreased (P < 0.05) with advance in grazing period, while the opposite trend was noted for fiber content. Time allotted for grazing plus browsing, ruminating and idle did not differ among AS xi (P > 0.05). However, camels and goats spent lower time grazing and higher time browsing than sheep and cattle. The CP content of hand-plucked forages was highest for camels (16.8%), intermediate for sheep (9.3%) and goats (10.2%) and lowest for cattle (4.5%; P < 0.05); while values for NDF took an opposite trend. The IVDMD content of hand-plucked samples took the trend of CP content ranging 43.6 to 72.8%. ADG was higher for camels (34, 31, 94 and 358 g/day (SEM = 30.3)); whereas BW change as a percentage of initial BW was relatively lower for cattle (19, 22, 11 and 26% (SEM = 4.15)) for sheep, goats, cattle and camels, respectively. During the digestibility trial DM, OM, CP, NDF and ADF as a percentage of BW was in the order of Cattle > Goat > Sheep > Camel. Intake and apparent digestibility of DM, OM, CP and NDF were higher for the DR that received C. Apparent digestibility of DM was 63.9 65.4, 60.9 and 57.4 (SEM = 2.00) and that of CP was 62.8, 65.1, 55.1 and 54.4 (SEM = 2.43) for sheep, goats, cattle and camel, respectively. The DM, CP, and NDF digestibilities for camels were similar with cattle but lower than sheep and goats. The ADF digestibility for camels was lower than cattle, sheep and goats. In conclusion, the impact of co-grazing on biomass and chemical composition in this study appears to be of not high magnitude. Differences in time spent for grazing and browsing indicates reduced dietary overlap among the animal species. This and perhaps the utilization of browse species to a greater extent by camels and goats might have led to greater animal yield than probably stocking the range by cattle or cattle and sheep only, suggesting co-grazing in the current study to appear beneficial. However, the herbaceous vegetation condition might have not maximized animal yield as apparent from the poor chemical composition of the range and the relatively lower productivity of cattle, reflecting the need for its improvement. The digestibility trial result suggest that camels are generally lower in their digestive capacity compared to ruminants for the dietary regimes of this study. However, differences are mainly between camel and small ruminants. Comparison of camel and cattle on digestive capacity differ only for ADF being lower for the former. Ruminant species are comparable in their digestive capacity except for CP where the value was lower for cattle.