The regulation of food intake by sheep

Abstract

1. A series of experiments with adult sheep were carried out in an attempt to place on a quantitative basis the generalisation that the voluntary food intake of ruminants increases with the quality of the fodder they are given.2. Methods of determining voluntary intake free of subjective bias were developed. It was shown that voluntary intake varied with a fractional power of body weight close to 0·734. The length of time necessary to establish stable intakes was 12–15 days and the number of times fresh food was offered each day had no apparent effect on intake.3. It was found that voluntary intake of long fodders was related to the apparent digestibility of their energy, increasing rapidly as digestibility increased from 38% to 70% and thereafter more slowly.4. The giving of concentrated food resulted in a drop in the voluntary intake of fodder. With high quality hay 100 g. concentrates replaced 100 g. hay. With poor quality hay, 100 g. concentrates replaced 47 g. of hay.5. The passage of three widely different hays through the gut was measured and the poorest passed most slowly. Calculations showed that the dry matter content of gut contents was the same for all three materials irrespective of their quality.6. It was shown that an increase in digestibility of 10 units in the range 40–60% resulted in considerable increases in the total amount of energy apparently digested and in equivalent increases in daily gain.7. The digested energy consumed/day/kg. W0·734 (E) can be related to voluntary intake (I) g./day/kg. W0·734 by the equation:—E=4·(I—31)which provides a rapid and easy method of assessing fodder quality under conditions of ad libitum supply.8. The results are discussed and it is shown that under ad libitum feeding conditions an increase in the nutritive value of unit feed from 50 to 55, i.e. by 10%, increases body gain by 100%.

Voluntary Intake of Forage by Holstein Cows as Influenced by Lactation, Gestation, Body Weight, and Frequency of Feeding

“…It was concluded from this analysis that age is of no value in predicting forage DXVI intake. This conclusion followed from the very small differences in R ~ values (.537 and .532) between Equation []], which included age (X~), and Equation [2], which omitted X~. Likewise, gain in body weight and body weight itself contributed very little information to such a prediction.…”

“…However, in experiments where effects on voluntary intake were measurable, it was found that varying the frequency of offering forage had little effect on the total consumption (2,11).…”

Ammonium Hydroxide Treatment on Wheat Straw

“…The proportion of plant CWC tends to have adverse effects on voluntary intake and digestion rate. A lower digestion rate slows rate of passage of digesta through the digestive tract, and decreases rate of passage and further despresses intake (Blaxter, 1950;Blaxter et al, 1961). (Timell, 1964) .. Cellulose is usually the most abudant and insoluble polysaccharide which forms the fibrous structural backbone of CWC.…”

The expected and observed changes in the intake of three hays by sheep after shearing

“…Numerous experiments have been conducted on the factors controlling food intake in the ruminant, and in these experiments, variation in energy expenditure has necessarily been minimized. For instance, in a study of the hay intake of sheep in metabolism crates Blaxter, Wainman & Wilson (1961) found that the intake of food was closely related to its apparent digestibility. This general effect was also observed when sixty-R G z 9AT.…”