[The electric discharge during the feeding behavior of Electrophorus electricus].
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One hundred and forty-four pigs were used to determine the effects of a putative synthetic maternal pheromone on behavior and performance of weanling pigs. Each pen of weaned pigs contained three pigs that were given free access to water and feed. Pigs were videotaped in time lapse for 48 h after weaning and weekly body weights and feed disappearances were recorded for 4 wk. Treatments included: a) control (vehicle applied), b) 30 mL of synthetic pheromone applied to the feeder, or c) 10 mL of synthetic pheromone applied to each of three pigs' snouts. Pigs exposed to the synthetic pheromone spent more (P < 0.05) time with their heads in the feeder and less (P < 0.05) time drinking, lying down, or engaged in agonistic behaviors than control pigs. Pigs exposed to the synthetic pheromone were more (P < 0.05) active during the 48-h period of video taping than control pigs. Pigs exposed to the synthetic pheromone (either on the feeder or their snout) had increased (P < 0.01) average daily gain (ADG) and better (P < 0.01) feed:gain ratio than control pigs over the 28-d postweaning period. In conclusion, the putative synthetic pheromone, applied once at weaning, stimulated apparent feeding behaviors, and reduced fighting and apparent drinking behaviors during the first 48 h after weaning. ADG and feed:gain ratio were improved by application of the putative synthetic pheromone either directly on the feeder or when painted on the pigs' snouts. Olfactory signals can modulate adaptation to the postweaning environment in ways that may improve pig performance and welfare.
Feeding, a fundamentally rhythmic behavior in many animals, is expected to exhibit modulation with respect to prey type. Using high-speed videography (200 frames(-1)) and kinematic analysis, we investigated prey-processing behavior in the long-nosed leopard lizard (Gambelia wislizenii). The effects of two prey types were examined, innocuous immature crickets (Acheta domesticus) and noxious stinging hymenopterans (honeybees [Apis mellifer] and yellow jackets [Vespula sp.]). Stinging hymenopterans are processed more extensively, with higher gape-cycling frequencies, and for a greater duration than are crickets. Generalized tetrapod feeding models were used as a framework to test the hypothesis that gape profile characteristics are modulated in response to prey noxiousness. Cricket processing generally fits the models, but hymenopteran processing departs from typical model parameters. In particular, the SO phase is absent to barely detectable during hymenopteran processing. This likely represents an effect of extrinsic neural input on a centrally directed rhythmic motor pattern, possibly to avoid being stung. Differences in the capture behavior of crickets versus hymenopterans indicate that G. wislizenii assesses prey noxiousness before physical contact with prey and modifies its capture behavior accordingly. These results add to the growing body of evidence that sensory information can play a critical role in shaping stereotyped rhythmic behaviors in non-mammalian tetrapods.
The objective of these experiments was to establish the relationship of plasma ghrelin concentrations with feed intake and hormones indicative of nutritional state of cattle. In Exp.1, 4 steers (BW 450 +/- 14.3 kg) were used in a crossover design to compare plasma ghrelin concentrations of feed-deprived steers with those of steers allowed to consume feed and to establish the relationship of plasma ghrelin concentrations with those of GH, insulin (INS), glucose (GLU), and NEFA. After adaptation to a once-daily feed offering (0800), 2 steers continued the once-daily feeding schedule (FED), whereas feed was withheld from the other 2 steers (FAST). Serial blood samples were collected via indwelling jugular catheter from times equivalent to 22 h through 48 h of feed deprivation. Average plasma ghrelin concentrations were greater (P < 0.001) in FAST compared with FED (690 and 123 +/- 6.5 pg/mL) steers. Average plasma ghrelin concentrations for FED steers prefeeding were elevated (P < 0.001) when compared with those postfeeding (174 and 102 +/- 4.2 pg/mL, respectively). Average plasma GH concentration was elevated (P < 0.05) for FAST steers compared with FED steers. Plasma GLU concentrations were not different; however, for FAST steers, NEFA concentrations were elevated (P < 0.001) and INS concentrations were decreased (P < 0.001). In Exp. 2, 4 steers (BW 416 +/- 17.2 kg) were used in a crossover design to determine the effects of i.v. injection of bovine ghrelin (bGR) on plasma GH, INS, GLU, and NEFA concentrations; length of time spent eating; and DMI. Steers were offered feed once daily (0800). Serial blood samples were collected from steers via indwelling jugular catheter. Saline or bGR was injected via jugular catheter at 1200 and 1400. A dosage of 0.08 microg/kg of BW bGR was used to achieve a plasma ghrelin concentration similar to the physiological concentration measured in a FAST steer in Exp. 1 (1,000 pg/mL). Injection of bGR resulted in elevated (P < 0.005) plasma GH concentrations after the 1200 but not the 1400 injection. Plasma INS, GLU, and NEFA concentrations were not affected by bGR injection. For the combined 1-h periods postinjection, length of time spent eating was greater (P = 0.02) and DMI tended to be increased (P = 0.06) for bGR steers. These data are consistent with the hypothesis that ghrelin serves as a metabolic signal for feed intake or energy balance in ruminants.
Inhibition of neurons in the nucleus accumbens shell (AcbSh) with local injections of GABA agonists or glutamate antagonists elicits an intense, but specific, feeding response resembling that seen after stimulation of the lateral hypothalamus (LH). To help characterize the contribution of the LH to the expression of AcbSh-mediated feeding, we used the immunohistochemical detection of the nuclear protein Fos to determine whether inhibition of AcbSh cells results in an activation of LH neurons. Injections of the GABA(A) agonist muscimol into the AcbSh greatly increased the number of cells exhibiting Fos-like immunoreactivity in the LH, as well as in the lateral septum, paraventricular hypothalamic nucleus, ventral tegmental area, substantia nigra pars compacta, and nucleus of the solitary tract. Blocking activation of LH neurons with the selective NMDA receptor blocker D(-)-AP-5 is known to suppress deprivation-induced feeding. We found that injections of D(-)-AP5 into the LH also dose-dependently suppressed AcbSh-mediated feeding. It is likely that inhibition of GABAergic neurons in the AcbSh is responsible for eliciting this feeding. If a behaviorally relevant GABAergic projection terminates in the LH, we should be able to mimic the effects seen after inhibition of the projection neurons by applying a GABA receptor blocker to the area. However, injections of the GABA(A) receptor blocker bicuculline or the GABA(B) receptor blocker saclofen did not significantly affect food intake. Thus, it appears that the expression of the feeding response depends on an NMDA-preferring receptor-mediated activation of LH neurons and is not the result of disinhibiting LH cells by disrupting transmission at GABA synapses.
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BACKGROUND: Feeding formulas for premature infants often contain medium-chain triacylglycerols (MCTs). However, previous studies in animals and adults showed that MCTs may decrease food intake. OBJECTIVES: The objectives were to determine in hospitalized premature infants whether food intake is modified by dietary MCT supply and to assess the effects on thermoregulation and sleep, which are involved in the regulation of energy metabolism and in the optimal physiologic development of the neonates. DESIGN: Food intake, body mass, and nutritional efficiency during 3 consecutive days were compared in 2 groups of neonates according to the fat composition of their feeding formula [MCT group: 37% MCT, 63% long-chain triacylglycerols (LCTs); LCT group: 100% LCT]. On the third day, sleep and metabolic rate were recorded in the morning during an interval between meals. RESULTS: Regardless of day, energy intake was greater in the MCT group than in the LCT group (x difference: 67.3 kJ x kg(-1) x d(-1); P = 0.007). Metabolic rate (1.8 mL x min(-1) x kg(-1); P < 0.001), cheek skin temperature (0.31 degrees C; P = 0.04), and total sleep time (52 min; P = 0.01) were also higher in the MCT group. CONCLUSION: The ratio of MCTs to LCTs in neonates' feeding formulas can modify physiologic functions involved in energy-balance regulation.
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