Ingestive behaviour and herbage intake of sheep and cattle grazing a forage crop of Hordeum vulgare cv. Athos

Abstract

The ingestive behaviour and herbage intake of sheep and cattle, as affected by characteristics of a Hordeum vulgare cv. Athos sward was investigated under conditions of continuous stocking. Nine different 'sward types' were produced by sowing at different seeding rates.

Swards were described in terms of structure and botanical composition by herbage weight, height and inclined point-quadrat measurements. Diet selection and size of individual bites were determined from extrusa samples collected from oesophageally fistulated animals. Grazing times were recorded mechanically by use of vibracorders and rate of biting, visually by use of a '20-bite' technique.

Linear regression analysis shows grazing time, rate of biting and bite size to be negatively correlated to sward height, for sheep; whereas sward height seems to have had little effect on grazing time or rate of biting in cattle. There was a strong positive correlation between bite size and sward height, for cattle.

Grazing time and rate of biting were positively correlated, and bite size negatively correlated, with sward bulk density; though correlation coefficients for grazing time and rate of biting on this sward variable were not significantly different from zero, for cattle.

Herbage intake could not be precisely estimated due to inherent errors in the estimation of one or more of the behavioural variables - grazing time, rate of biting or bite size.

It was concluded that sheep experience more difficulty harvesting tall herbage, than do cattle and that sward height and density are, in themselves, inadequate to explain variation in grazing behaviour - particularly for cattle.