Effects of season, stocking rate, and grazing duration on diet selected by hoggets grazing mixed grass-clover pastures

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Abstract
Measurements were made of the influence of season and stocking rate on herbage mass, composition, and organic matter digestibility (OMD) and on the composition and OMD of the diet selected by grazing hoggets. A stocking rate of 36 hoggets per ha reduced the amount of stem and dead matter and increased the OMD of herbage on offer compared to 24 hoggets per ha. Herbage OMD declined from 60.7% to 54.7% over summer and increased from 56.7% to 72.1% in autumn. Herbage composition changes during 3-day grazing periods showed reductions of OMD, green leaf, ryegrass, and weeds, and increases in the proportion of dead matter. Diet samples from oesophageal fistulated sheep showed the selection of green leaf and the rejection of dead matter. Dead matter content of the diet was positively correlated with percentage composition of dead matter in the sward, and negatively correlated with the amount and percentage green leaf on offer. Diet OMD was positively correlated with percentage green leaf on offer and percentage composition of diet leaf, and was a mean of 13 percentage units higher than the OMD of the pasture on offer.