A study of factors affecting the voluntary intake of food by cattle

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Abstract
SUMMARY: Six diets providing ratios of concentrate to hay of 100 : 0, 95 : 5, 90 : 10, 80 : 20, 70 : 30 and 60 : 40 were given ad libitum to 24 British Friesian steers. The hay (in the long form) was offered separately from the concentrates. From 91 to 136 kg live weight, as the proportion of hay in the diet increased, daily dry-matter intake decreased. Over the weight range, 136 to 363 kg live weight, the addition of small amounts of hay to the concentrate diet caused an increase in intake. At 42 weeks of age a digestibility trial was carried out. Daily drymatter intake was maximal when the diet contained 80% concentrates. The apparent digestibility and mean retention time of the diets increased as the proportion of concentrates increased. Differences in estimated gut fill were not significant. The diet consisting of concentrate only resulted in the lowest concentration of acetic acid and the highest concentration of propionic and butyric acids in the rumen liquor. Net-energy intake tended to increase as the proportion of concentrates increased from 60 to 90% but then remained fairly constant.