EFFECT OF FEEDING CHOPPED AND UNCHOPPED GROUNDNUT HAULM (HARAWA) ON NUTRIENT UTILIZATION AND THE PRODUCTION OF SOME RUMEN METABOLITES IN YANKASA LAMBS

The effect of feeding chopped and unchopped groundnut haulm (Harawa) on nutrient intake, metabolism and utilization was determined in 24 (12 each of male and female) growing Yankasa lambs. Feeding of chopped harawa significantly (P 0.05) Increased feed intake, the digestibility of nutrients and liveweight gains. It also had an ap­preciable effect on nitrogen retention and the pro­duction of total rumen nitrogen, rumen ammonia-nitrogen and volatile fatty acids. The availability of digestible energy did not differ significantly under the two feeding regions. There was a better feed effi­ciency for lambs fed chopped hay.

Longer defoliation interval ensures expression of the ‘high sugar’ trait in perennial ryegrass cultivars in cool temperate Tasmania, Australia

SUMMARYPerennial ryegrass (Lolium perenneL.) cultivars have been developed to express higher levels of leaf water-soluble carbohydrates (WSC), but expression of this ‘high sugar’ trait varies between environments and is likely to be further influenced by the extent of plant re-growth. The herbage WSC concentration and the ratio of WSC to crude protein (WSC : CP) in high sugar cultivars AberMagic and SF Joule were therefore compared with a control cultivar, Arrow, under cool temperate Tasmanian conditions and two defoliation interval treatments. The irrigated cultivars were subjected to defoliation at either the 1·5-leaf or 3-leaf stage of re-growth, and additional components of nutritive value (fibre concentrations and metabolizable energy content) and dry matter (DM) yields were measured throughout a 12-month period (March 2011 to March 2012). The high sugar trait was consistently expressed in AberMagic, which under both the 1·5-leaf and 3-leaf stages defoliation intervals, displayed the highest WSC concentration (mean 194 and 247 mg/g DM, respectively, compared with 153 and 178 mg/g DM for Arrow) and highest WSC : CP ratio (mean 0·74 and 1·29, respectively, compared with 0·58 and 0·85 for Arrow). Defoliation at the 3-leaf stage of regrowth ensured greater expression of the high sugar trait in both AberMagic and SF Joule, as measured by the increase in WSC concentration and WSC : CP ratio as a result of increasing defoliation interval. The strength and consistency of trait expression in AberMagic under the 3-leaf stage defoliation interval warrants further research to investigate its effect on rumen nitrogen (N) partitioning and milk production in this environment.

The effect of dietary asynchrony on rumen nitrogen recycling in sheep

Recent work (Sinclair et al. 1993) has suggested that synchronising the rate of rumen breakdown and availability of dietary energy and nitrogenous components can increase capture of rumen degradable nitrogen and improve efficiency of microbial protein synthesis. For rumen bacteria to function efficiently they require a supply of both energy and nitrogen sources together i.e a synchronous diet. Nitrogen recycling between the blood and the rumen is a major contributor to the nitrogen economy of the animal and supplies substantial quantities of nitrogen to the rumen bacteria (Kennedy & Milligan 1980). The amount of nitrogen recycled to the rumen is diet dependant. This dependency may not solely be due to the levels of dietary nutrients but also to their rate of breakdown and availability to the rumen bacteria. The predominant mechanism controlling nitrogen recycling between the blood and the rumen appears to be rumen ammonia concentration It has been suggested that the recycling of nitrogen between the blood urea pool and the rumen ammonia pool may be able to compensate for periods of dietary nitrogen deficiency in the rumen due to the asynchrony of availability of the nitrogen and energy components to the rumen bacteria.