Factors affecting the grazing habits of ruminants are discussed in relation to the attractiveness and nutritive value of herbages and the observed preferences of cattle and sheep at different times.
Methods of measuring stock preferences are considered and it is concluded that, while frequent eye estimates of the quantity of each species appear to provide an adequate method, continuous observations and herbage sampling are useful adjuncts to it.
The results of five experiments are given. Four were carried out in 3 years' winter grazing and one on spring, summer and autumn grazing over 2 years. In the latter experiment herbage samples were chemically analysed and a relationship with the observed preferences was calculated.
In the winter grazing trials the greener grasses tended to be selected first, i.e. timothy, white clover, rough-stalked meadow grass, perennial and Italian rye-grass. Cocksfoot, Phalaris, red fescue and meadow fescue were not generally relished. Meadow foxtail, smooth-stalked meadow grass, tall fescue and sometimes the different varieties of rye-grass and timothy varied in rank from year to year as a result of differential frost damage and fungal attacks.
In the summer grazing trials lucerne and white clover were found palatable in all the 1956 trials; in 1957 lucerne remained so, but white clover was less well liked, especially in June and July. The amount of grass growing with the clover seemed to affect attractiveness, mixtures being preferred to either species by itself. Meadow fescue and timothy were always ranked high, perennial rye-grass and cocksfoot usually next. Agrostis and red fescue were lowest. For the grasses, preference rank was positively correlated in 1957 with water-soluble dry matter, water-soluble ash, water-soluble carbohydrate and negatively correlated with lignin content.
Results are compared with those of other investigators and they show a marked degree of similarity. Variability in the data for sheep is possibly due to limitations in technique. The results for sheep and for cattle are compared; and it was generally found that cattle were fonder of meadow fescue than sheep, and less fond of cocksfoot.
Stock appear to graze those plants which will most readily supply their requirements for salts and energy (carbohydrates). Factors like dung, fungal attack, accessibility, density and toughness may interfere with this relationship.