A grazing experiment was conducted at the Big Ridge 2 site CSIRO, Chiswick
(30˚31′S, 151˚39′E), 20 km south of Armidale, New South
Wales, Australia. The site was established in 1955. In March 1966, phalaris
and white clover were sown and pastures were fertilised annually with
superphosphate until 1993. There were 3 pasture treatments, each with 2
replicates: degraded pasture (low phalaris content), phalaris-dominant, and
phalaris–white clover.
The effect of pasture type on animal production (liveweight gain and wool) was
only significant in 1996, when there were large differences in pasture
composition and production between the 3 pasture types. n-Alkane based
estimates showed that pasture degradation affected diet selection and nutrient
intake and thus sheep production. The estimates in this study also showed no
clear preference for a single pasture species over time and lack of strong
preferential selection for clovers when sheep were grazing 3 contrasting
pastures. Preferential selection of a particular species varied over time
depending on the presence and availability of alternative species. Although
there were large differences in total N and S intake and faecal output between
the 3 pastures, the proportion of the dietary nutrient used for production was
similar. This observation reveals the importance of further improving pasture
and grazing management, particularly in productive phalaris–white clover
pasture with high nutrient flux, to improve nutrient recycling through plant
uptake and retention by animals in the grazing ecosystem, and reduce losses.
Dietary nutrient allocation to somatic tissue synthesis in emerging subimago freshwater mayfly Ephemera danica
