Seasonal relations between animal gain, pasture production and stocking rate on two tropical grass-legume pastures

Abstract

The relationship between stocking rate and liveweight change per animal was examined over a period of 3 years for two continuously grazed pastures, one of Brachiaria and the other consisting of guinea grass with Endeavour stylo and Siratro. On an annual basis there was no significant effect of stocking rate over the last 2 years, but on a seasonal basis there were highly significant effects in all seasons. In the dry seasons, animal gain rose as the stocking rate fell, but in the last two wet seasons gains fell with the lower stocking rates. On an annual basis the two effects cancelled out. Response surfaces for gain versus pasture yield and stocking rate were curvilinear (quadratic) during the wet season and linear during the dry. Optimum stocking rates (for maximum gain per hectare) were determined for the wet and dry seasons; the rate was greatly affected by the yield of green material during the dry season but less so during the wet. The possible causes of this reversed wetseason effect are discussed.

Diet Quality and Performance of Heifers in the Subtropics

“…In all 3 yr, the PUN concentrations in continuously grazed heifers were on average higher than those in the rotationally grazed heifers, but only in 1990, when PUN levels were >9 mg dL −1 into July and IVOMD remained adequate, did this result in the trend for higher ADG and final BW. Studies in Australia with tropical forage species have shown declines in animal performance during the wet season when stocking rates effectively decline due to increased rate of grass growth (Stobbs, 1970; Edye et al, 1978). This decline in animal performance, when selectivity should have been enhanced, has been explained, in part, by the inability of animals to maintain the quality and quantity of forage in even the heavily spot‐grazed areas in pastures (Edye et al, 1978).…”

“…Studies in Australia with tropical forage species have shown declines in animal performance during the wet season when stocking rates effectively decline due to increased rate of grass growth (Stobbs, 1970; Edye et al, 1978). This decline in animal performance, when selectivity should have been enhanced, has been explained, in part, by the inability of animals to maintain the quality and quantity of forage in even the heavily spot‐grazed areas in pastures (Edye et al, 1978). These studies were conducted with taller‐growing tropical bunchgrass species, and it was speculated that this might not be such a problem with shorter‐growing grass species (Edye et al, 1978).…”

“…This decline in animal performance, when selectivity should have been enhanced, has been explained, in part, by the inability of animals to maintain the quality and quantity of forage in even the heavily spot‐grazed areas in pastures (Edye et al, 1978). These studies were conducted with taller‐growing tropical bunchgrass species, and it was speculated that this might not be such a problem with shorter‐growing grass species (Edye et al, 1978). Our results suggest that for bahiagrass, heifers may be unable to utilize the forage quickly enough to maintain forage nutritive value at levels that would maintain higher rates of animal performance.…”

Rainfall in the wet‐dry tropics: Extreme events at Darwin and similarities between years during the period 1870–1983 inclusive

“…Such variation and its consequences for the biota also pose problems for the conduct of manipulative experiments, the design of which assumes that any differences are a function of the treatments imposed. In the wet-dry tropics, however, seasonal effects can outweigh treatment effects (McCown et al 1974;Edye et al 1978), More often there is a significant year by treatment interaction (Norman 1960;Torssell 1975), Whilst there are ways of testing for differences in fluctuating environments (McCown et al 1974;Steams 1981), the resuh remains a unique consequence of the interaction of a manipulation and a rainfall event at a key phase of the experiment. Thus experimental findings will rarely be generally applicable, and because ofthe low frequency of rainfall events, will be of limited predictive value.…”

Herbivore Dynamics and Range Contraction in Kajiado County Kenya: Climate and Land Use Changes, Population Pressures, Governance, Policy and Human-wildlife Conflicts

“…But it was positively correlated with the combined livestock biomass, contrary to expectation, and suggesting that both wildlife biomass and livestock biomass are similarly affected by the influence of the interannual rainfall variation on vegetation. The negative correlation with rainfall suggests that high rainfall lowers vegetation quality and hence habitat suitability for the herbivores (Edye et al 1978, Jarrell et al 1981, Fynn & O'Connor 2000.…”