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Triacylglycerols of varying chain lengths were tested for their effects on food intake in fasted Single-Comb White Leghorn cockerels 9-12 weeks of age. Tributyrin, tricaprylin, triolein, or saline were intubated intragastrically or infused intrahepatically. All triacylglycerol administrations were in 10 ml volumes with 10 kcal being infused intrahepatically and 10 or 20 kcal being infused intragastrically. When administered intragastrically, the short-chained triacylglycerol tributyrin decreased food intake at most times tested; the medium chain-length tricaprylin and the long chain-length triolein affected food intake sporadically. When infused into the liver, tributyrin and tricaprylin decreased food intake at most times tested, whereas triolein decreased food intake at 60 and 180 minutes only. Satiating effectiveness was related to triacylglycerol chain length when intubated, which may reflect rate of absorption from the gut; however, hepatic satiety receptors were also differentially sensitive to triacylglycerol chain length indicating that more than rate of assimilation from the gut must be considered.

Two experiments were conducted to determine if food intake of free-feeding chickens could be affected by infusions of plasma from fasted fowl. In the first experiment, chickens from two lines genetically selected for high or low body weight were infused intrahepatically with plasma collected from free-fed and fasted individuals from each line. Food intake of low-weight line birds was increased significantly by infusions of plasma from fasted high-weight line chickens when compared to food intake of low-weight line birds receiving plasma from free-fed low-weight line chickens. Food consumption in high-weight line birds was unaffected by any of the plasma treatments. In the second experiment, plasma from free-fed and fasted high-weight line chickens was infused intrahepatically into Single Comb White Leghorn cockerels. Again the birds receiving the plasma from the fasted fowl consumed significantly more food than those infused with plasma from free-fed fowl. The results of these experiments suggest that some property of plasma from fasted birds stimulates appetite. Selection for increased body weight may have intensified this hunger factor in high weight fowl.

Plasma was collected from free-feeding Leghorn cockerels and partitioned by gel filtration into fractions of different molecular weight ranges. The individual fractions were then lyophilized and reconstituted to four times the original concentration. The plasma was administered to 10-week-old Leghorn cockerels via a stainless steel guide cannula, stereotaxically implanted into the lateral cerebral ventricle. Sated cockerels received 10 μl intracerebroventricular (ICV) injections of one of the concentrated plasma fractions or of a control injection of artificial cerebrospinal fluid. Food and water intake were monitored following injection. Food intake was significantly decreased by the ICV injection of plasma fractions less than 1500 mol wt, whereas water consumption was not significantly different from that of the controls. The 1500 to 5000 mol wt fraction and the fraction above 5000 did not alter either food or water intake. These results suggest that the plasma of free-feeding domestic fowl contains a low molecular weight factor that is involved in the regulation of food intake.

The neurotransmitter, serotonin, has been implicated in both food intake and body temperature regulation. In this experiment, the effect of tryptophan, the amino acid precursor of serotonin, on food consumption and rectal temperature in the fowl was determined. Single Comb White Leghorn cockerels were intubated with a tryptophan solution or distilled water. Tryptophan significantly (P less than or equal to .05) decreased both food intake and body temperature of the birds. These results suggest that tryptophan may inhibit food intake via peripheral rather than central mechanisms.

The objective of this study was to determine if a factor(s) involved in the regulation of food intake exists in the cerebrospinal fluid (CSF) of the domestic fowl. A technique was developed that allows blood-free CSF samples to be collected repeatedly from the cisterma magna for up to 6 weeks. Using this technique, CSF was collected from free-feeding and 24-hour fasted broiler cockerels and injected into the lateral cerebral ventricle of 8-week old Leghorn cockerels and 4-week old broiler cockerels. The free-feeding birds received 10 μl intracerebroventricular injections of CSF either at normal concentration (1 ×-CSF) (Experiments 1 and 3) or at four times normal concentration (4 ×-CSF) (Experiments 2 and 4). Artificial CSF served as the control. Food and water consumption were monitored following injection. The 1 ×- and 4 ×-CSF collected from both the free-feeding and 24-hour fasted donors did not affect the food intake of either the Leghorn or the broiler recipients. Water intake, however, was significantly increased in the Leghorns and broilers receiving the 4 ×-CSF collected from 24-hour fasted birds. Thus, there does not appear to be a factor(s) present in the CSF collected from the cisterna magna that alters food intake when injected into the lateral ventricle, but a factor may exist in the CSF collected from fasted donors that stimulates water intake.

The effects of dopamine (DA), norepinephrine (NE), epinephrine (E) and 5-hydroxytryptamine (5-HT) on food intake, water consumption and colonic body temperature (Tc) were investigated using Leghorn-type chicks. Food intake was not significantly affected by the intracerebroventricular injections of DA, NE or E. In contrast, 5-HT significantly decreased food intake in both sated and fasted chicks. Tc was significantly decreased by NE and E whereas DA and 5-HT prevented the decline seen in controls. Water consumption was not significantly affected by DA, NE or E; however, 5-HT increased water consumption of sated chicks and decreased water consumption in fasted ones. The feeding response of Leghorn chicks following ICV injection of these biogenic amines differs from that previously observed in the broiler-type chicks. This disparate response is discussed in relation to the different growth rates of the two types of birds.

A series of experiments was performed to examine the role of the duodenum in food intake regulation in the fowl. In each of the experiments, birds were surgically fitted with intraduodenal cannulae. In Experiments 1 to 6, Single Comb White Leghorn (SCWL) or Rock Cornish cockerels were infused with isosmotic glucose, urea, or saline solutions. Glucose had no effect on food intake as compared with the saline and urea control treatments. In the final experiment, food intake of splanchnicectomized SCWL cockerels was contrasted to that of sham-operated controls, following intraduodenal glucose infusions. No difference between the denerved and intact birds was observed. The duodenum of the fowl, unlike the mammal, does not appear to play a significant role in food intake regulation.

Although food intake regulation by the central nervous system in the fowl has received considerable attention, studies examining peripheral regulatory mechanisms are relatively few. The objective of these experiments was to determine the role of the liver in short-term regulation of feeding. Small volumes of isotonic glucose were infused into the hepatic circulation of undistrubed, unrestrained Single Comb White Leghorn (SCWL) and Rock-Cornish (RC) cockerels under both free-feeding and mildly-fasted conditions. Glucose infusions significantly decreased the food intake of free-feeding SCWL chicks but had no effect on mildly-fasted SCWL chicks. The RC chicks, whether free feeding or mildly fasted, were not influenced by the glucose infusions. These findings suggest that selection for increased growth rate has affected peripheral appetite regulatory mechanisms.

Five experiments were conducted to determine the effect of hepatic and jugular infusions of amino acid and lipid solutions on short-term food intake of cockerels. Neither jugular nor hepatic infusions of amino acids had any effect on food intake of Single-Comb White Leghorn (SCWL) cockerels. Lipid infusions had no effect on SCWL cockerels when administered intrajugularly but decreased food intake significantly when infused intrahepatically. In contrast, no effect on food intake was observed when Rock-Cornish (RC) cockerels were infused intrahepatically with lipid. Thus, it appears that the liver of the SCWL cockerel is not responsive to plasma amino acid concentrations but is sensitive to circulating lipid levels. This lipid sensitive mechanism may be important in the peripheral control of food intake in a chicken such as the SCWL which has been bred for egg production but may be desensitized in fowl such as the RC broiler which has been selected for large body size and feed consumption.

The food and water intake response of Leghorn chicks to intracerebroventricular (ICV) injections of glucose was studied. Experiments were done in both free-feeding and 24-hr fasted birds. The ICV injection of 10 μl of glucose solutions ranging from 5.5 to 30% had no significant effect on food or water intake in free-feeding or in 24-hr fasted Leghorns. This suggests that glucose does not influence food or water intake when injected into the lateral cerebro-ventricle. This effect is discussed in relationship to recent findings showing that injection of glucose into the third ventricle decreases food intake.

Four experiments were conducted to investigate the presence of a factor in the plasma of the domestic fowl that alters food intake when injected into the lateral cerebral ventricle. Plasma collected from free-feeding and 24-hour fasted birds was lyophilized and reconstituted to 2, 4, or 5 times normal concentration. Stainless steel guide cannulae were stereotaxically implanted into the lateral cerebral ventricle of 8-week-old Single Comb White Leghorn cockerels. Free-feeding birds received 10 μl intracerebroventricular (ICV) injections of normal (Experiment 1) and concentrated (Experiments 2, 3, and 4) plasma collected from free-feeding and 24-hour fasted birds. Artificial cerebrospinal fluid (aCSF) served as the control. Food intake was significantly decreased by ICV injections of 2, 4, and 5 times normal concentration of plasma from fed birds. Plasma from fasted birds did not alter food intake regardless of concentration, but did significantly reduce water intake when concentrated to five times normal. It appears that a satiety factor, which can be detected by the central nervous system, is present in the plasma of free-feeding domestic fowl.

The effects of intraperitoneal injections of tryptophan on food intake in the chicken were examined. Four levels of tryptophan (12.5, 25, 50, 100 mg), and a saline control were tested in birds that were ad libitum fed or fasted 24 hr. The tryptophan treatments decreased food intake in the ad libitum-fed chickens in a dose-dependent manner. Food intake of the 24-hr fasted chickens was not influenced by the tryptophan injections. It is not known whether tryptophan is acting centrally or peripherally to decrease food intake of ad libitum-fed chickens.