The quantitative significance of long-term regulation of food intake in the cow

Abstract

I. Six adult, non-pregnant, non-lactating, Friesian cows were used when fat and when thin to measure differences in the voluntary intakes of straw, hay and hay plus concentrates caused by the fatness of the animals. Measurements of digestibility, time of retention of food in the digestive tract, rate of breakdown of cotton threads in the ventral sac of the rumen and amounts of digesta in the reticule-rumen were included.2. The mean voluntary intakes of straw were similar for fat and thin cows. In absolute terms, thin cows consumed 31 % more hay and 23 yo more hay and concentrates than fat cows; in relation to metabolic body size ( W 0 9 , these differences were 76% and 52% respectively.3. Small decreases in digestibility of these diets by the thin cows, reflected in slight reductions in the rate of loss of weight of cotton threads placed in the rumen, did not alter the significance of the differences in intake between fat and thin cows.4. Small changes in time of retention of food in the digestive tract suggested that the capacity of the tract may have been greatest in the thin cows.5 . The presence of a greater amount of digesta in the reticulo-rumen of thin cows than in that of fat cows after eating hay supports the suggestion of a greater gut capacity in these animals. In both fat and thin cows, the capacity of thereticulo-rumen didnot appearto havelimited the intake of the hay and concentrate diet. In both groups the lowest levels of rumen fill were observed after straw was given.6. The results are discussed in terms of possible mechanisms which may operate to reduce the voluntary intake of medium-and good-quality diets as cows become fatter. When poorquality roughages are given, other factors appear to conceal any differences in intake which may exist between fat and thin cows.It is well known that in adult man and adult animals body-weight is usually maintained at more or less constant levels, sometimes for very long periods of time. Thus a long-term regulation of food intake must have an important and precise role. As a possible mechanism bringing about such control, [Kennedy, 1953) postulated a ' lipostatic' theory of regulation of voluntary food intake. This theory proposes that some compound, released from the fat depots in proportion to their total size, inhibits food intake. Thus, over a period of time, food intake is gradually reduced as the animal becomes fatter, until eventually only the maintenance requirement of the animal will be met, and the animal will thus gain no further weight.The quantitative effects of such a mechanism in ruminants are not clear. Schinckel (1960) observed a progressive decline in the ad lib. intake of grazing sheep, which was associated with increasing bodily fatness. However, this was confounded with an increase in environmental temperature during the last part of the experiment. He refers also to a syndrome in extremely fat sheep in which some unknown factor precipitates a complete refusal to eat. The animals lose weight and usually die in Japan.

Effects of supplementary concentrate level in winter, and subsequent finishing on pasture or indoors, on performance and carcass traits of Holstein–Friesian, Aberdeen Angus×Holstein–Friesian and Belgian Blue×Holstein–Friesian steers

“…This agrees with the finding of Wright et al (1986) who reported that animals undergoing compensatory growth, following a lower feeding level the previous winter, had higher herbage intakes during the grazing season, both in absolute values and per kg live weight. The authors attributed this to a negative association between body fatness and voluntary food intake as earlier demonstrated for dairy (Bines et al, 1969) and beef (Hodgson et al, 1980) cows.…”

Metabolic and physical control of food intake in ruminants

“…mesenteric and omental fat) apparently reduces the effective capacity of the cavity and this is associated with a reduced roughage intake by these animals (Tayler, 1959;Forbes, 1969;Bines, Suzuki & Balch, 1969). This reduction in intake is not necessarily an effect of a physical regulatory mechanism, since concentrate intake is also reduced in fat animals without the rumen being filled to capacity (Bines et al 1969). However, since fat cows do not eat enough hay even to maintain their weight, whereas thin cows eat enough of the same hay to gain weight (Bines, unpublished), the existence of a physical regulator appears likely.…”

“…When a ruminant is given a concentrated diet, the amount of material in the rumen at the end of a meal is less than when the diet consists mainly of roughage (Bines tx Davey, 1970;; thus, some factor has assumed greater importance than rumen fill in the regulation of food intake. At a single meal, there is considerable variation between different diets in the amount eaten, considerably less of an all-concentrate diet being eaten than of one containing a small proportion of roughage (Bines & Davey, 1970). However, when the total amount of food consumed in a day or longer period is considered, there is strong evidence that, with a concentrate diet, an animal's total intake of digestible energy is constant regardless of the exact composition of the ration fed (Dinius & Baumgardt, 1970).…”

A note on the effect of body condition on the voluntary intake of dried grass wafers by Scottish Blackface ewes

“…There are also examples of so-called compensatory intake by sheep when their nutrient intake has previously been restricted (J. Eadie, unpublished data; Foot and Greenhalgh, 1969), which may be linked with the small amount of fat in the body of the undernourished animal. Bines, Suzuki and Balch (1969) found that the same six cows ate 30% more hay and 23 % more hay plus concentrates when they were thin than when fat.…”

“…Hervey, 1969). Bines et al (1969) suggested that thin cows may have a greater rate of utilization of lipogenic substrates than fat cows and that the faster removal of the products of digestion might have stimulated higher intake.…”