Study design/Study C

Lambs were individually fed with wilted green Napier grass at libitum adjusting the level of offer weekly to allow for a refusal of approximately 15% of fodder offered. Refusals were collected and weighed daily.

Hanson and Fernandez-Rivera (2005) suggested that the data should be analysed by analysis of covariance with initial weight as a covariate. Having designed the experiment as a randomised block (groups of lambs based on initial weight) the analysis should strictly be that for a randomised block with a term for replicate. A covariate for initial weight (see below) can also be included if this accounts for additional residual variation.

Response variables included voluntary intake of dry matter, in vivo digestibility, digestible organic matter, average daily gain and carcass weight. The sheep adapted poorly to the diet during the early stages of the experiment and overall growth rate was poor. This may have influenced the conclusions that can be drawn from the experiment. It would have been preferable to have used cattle for this experiment, being the livestock to which Napier grass is generally fed, but this would have been more expensive.