Grazing Impacts on Rangeland Condition in Semi-Arid South-Western Africa

The savannah biome, consisting of a dense herbaceous layer and a relatively open woody layer in competitive balance, constitutes 64% of the land surface of Namibia, an arid country in south-western Africa, and is used mainly for extensive cattle and sheep ranching. About half of the savannah area is affected by dense to moderately dense bush-thickening, resulting in a ten-fold decrease in the rangeland’s grass-based carrying capacity and a concomitant loss in meat production of about US$115 million per year (De Klerk, 2004). Bushencroached areas typically have densities \u3e 2 000 bushes/ha with \u3e 90% belonging to a single species. High grazing pressure by specialist grazers, such as domestic cattle, is often blamed for rangeland degradation. There is an urgent need to understand the dynamics of bush encroachment and devise grazing strategies to contain it

The effect of concentrate supplementation on the productivity of grazing Jersey cows on a pasture based system

The effect of concentrate feeding on milk production, milk composition, live weight, condition score and intercalving period of 60 Jersey cows grazing high quality pastures over two lactations was determined. Cows were fed at a no (NC), low (LC), medium (MC) or high (HC) level of concentrate. All cows received a mineral supplement of 300 g/day. The LC, MC and HC groups were fed an energy concentrate at 3, 6 and 9 kg/day, respectively from day 1 to day 150 of lactation followed by 1.5, 3 and 4.5 kg of energy concentrate per day from day 151 to day 300 of lactation. The energy concentrate consisted of 10.6% whole cottonseed, 42.1% rolled maize, 42.1% rolled wheat, 4.2% molasses, 0.5% feedlime and 0.5% salt on a dry matter (DM) basis. A protein concentrate consisting of 76.5% cotton oil cake and 23.5% fish meal was fed at 0.5, 1 and 1.5 kg per day to the LC, MC and HC group respectively from days 1 to 105 of lactation. The lactating cows grazed pasture allocated at 20 kg DM/cow/ day consisting of 43% perennial ryegrass/clover, 24% annual ryegrass/oats, 14% lucerne, 15% kikuyu and 4% other pastures during the experimental period. The fat corrected milk (FCM) production per lactation of cows fed NC (0 kg/day), LC (2.4 kg/day), MC (4.8 kg/day) and HC (7.2 kg/day) was 3741, 4645, 4868 and 5282 kg (s.e.m. = 146), respectively. Cows fed the high level of concentrate (HC) produced significantly more FCM and butterfat than cows on the other treatments. The FCM production of cows on the LC and MC treatments did not differ from each other and both produced more FCM than the control treatment. Cows produced 1.25, 0.78 and 0.54 L of FCM for each kg of concentrate fed at the LC, MC, and HC levels of concentrate feeding over two lactations. Concentrate feeding had no significant effect on milk composition, live weight and intercalving period of cows. The condition score of cows improved as the level of concentrate feeding increased. South African Journal of Animal Science Vol. 36(2) 2006: 105-11

Bush Encroachment Control and Risk Management in Semi-Arid Rangelands

We study the role of bush encroachment control for a farmer's income and income risk in a stochastic ecological-economic model of grazing management in semiarid rangelands. In particular, we study debushing as an instrument of risk management that complements the choice of an adaptive grazing management strategy for that sake. We show that debushing, while being a good practice for increasing the mean pasture productivity and thus expected income, also increases the farmer's income risk. The optimal extent of debushing for a risk-averse farmer is thus determined from balancing the positive and negative consequences of debushing on intertemporal and stochastic farm income

The Diet of Free-Ranging Beef Cattle in a Semi-Arid Savanna of Eastern Namibia

Beef ranching is the most important agricultural enterprise in arid and semi-arid SW African countries. It earns foreign exchange via beef exports to the EU and very many rural people depend on cattle pastoralism for their livelihood. However there is no published information on what cattle eat in such extensive systems. Therefore, it is difficult to optimize grazing strategies and to prevent degradation of rangeland