Predicting Feed Intake of Food-Producing Animals (1987) / Chapter Skim
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1. Introduction: Feed Intake Control Mechanisms
1. Introduction: Feed Intake Control Mechanisms
Pages 1-15
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While meal size can vary greatly, the total quantity eaten each day, for example, must be controlled to maintain energy balance. The signals of satiety that control individual meal size must have shorter time constants than the signals that regulate long-term energy balance.
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Ruminant feeding behavior can also be influenced by changes in osmolarity of body fluids. Increases in rumen fluid osmolarity from about 250 to 350 mOsM during rapid eating of large meals can produce hypertonicity of body fluids and result in dramatic circulatory and renal changes.
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(1984) have demonstrated that female Zucker obese and lean rats decreased daily food intake when immunized against pancreatic glucagon (conjugated to bovine serum albumin)
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Similar glucagon injections had no effect, which suggests that the response was caused by a specific peptide. However, many studies have demonstrated that insulin and glucagon have influential roles in controlling feeding behavior and in the regulation of energy balance.
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When the VMH of one partner of a pair was lesioned, it became obese while the other partner became thin and died apparently from inanition. It has been suggested that the nonlesioned hypothalamus of the one partner responded to the total positive energy balance of both rats by reducing its food intake.
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, a 17-ketosteroid, can produce a decrease in weight gain without affecting feed intake in lean mice and yellow obese mice that have hypertrophic adipose tissue (Yen et al., 1977; Cleary et al., 1982~. Not only was body weight reduced but the feed efficiency ratio, fat cell number, and size of the fat cell were significantly decreased (Cleary et al., 19841.
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Both average daily feed intake and weight gain increased in immunized rats versus controls. Sequestering of CCK released during a meal increased meal size, and in those animals that developed significant endogenous CCK-AB titers daily feed intake and weight gain increased.
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THE ROLE OF FEED INTAKE IN THE REGULATION OF ENERGY BALANCE The mechanisms involved in receiving information from the periphery and then processing it centrally to produce an appropriate response are not adequately defined. Factors such as GI conditions, hormones, and metabolites act on receptor systems which essentially transduce analog information (e.g., concentration)
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elicit large meals in satiated animals. In addition to the factors previously discussed, other factors are involved in feeding behavior and energy balance regulation.
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The energy balance regulator provides an input to the controller of hunger and satiety, and thus shifts in the body energy status are reflected by changes in feeding behavior. Deficits in body energy stores modulate the controller to increase meal size and meal frequency, whereas decreases occur during energy surfeit.
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Decreases length of first meal and meal size, but total intake remains unchanged because spontaneous meal number increases in cows Acetate Reduces meal size in cattle, sheep, and goats Lactate (sodium lactate injections) Reduces meal size in goats Propionate Reduces intake; shows evidence of propionate receptors in ruminal vein walls Sex hormones Estrogenic compounds Increase food intake in ruminants Progesterone Affects other ovarian hormones DHEAb Decreases weight gain without affecting food intake in mice PRLC Affects lactation and other physiological responses ASHY Affects lactation and other physiological responses LHe Affects lactation and other physiological responses aGH, growth hormone.
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Control of feed intake and regulation of energy balance in ruminants. Physiol.
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1985. Autoimmunization against b-endorphin increased food intakes and body weights of obese rats.
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1984. Decreased food intakes and body weights in rats immunized against pancreatic glucagon.
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1970a. Development of hormonal control over food intake and body weight in female rats.
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