Changes In Ingestive Behavior Research Articles

Early perturbations to fluid homeostasis alter development of hypothalamic feeding circuits with context-specific changes in ingestive behavior.

Drinking and feeding are tightly coordinated homeostatic events and the paraventricular nucleus of the hypothalamus (PVH) represents a possible node of neural integration for signals related to energy and fluid homeostasis. We used TRAP2;Ai14 and Fos labeling to visualize neurons in the PVH and median preoptic nucleus (MEPO) responding to both water deprivation and hunger. Moreover, we determined that structural and functional development of dehydration-sensitive inputs to the PVH from the MEPO precedes those of agouti-related peptide (AgRP) neurons, which convey hunger signals and are known to be developmentally programmed by nutrition. We also determined that osmotic hyperstimulation of neonatal mice led to enhanced AgRP inputs to the PVH in adulthood, as well as disruptions to ingestive behaviors during high-fat diet feeding and dehydration-anorexia. Thus, development of feeding circuits is impacted not only by nutritional signals, but also by early perturbations to fluid homeostasis with context-specific consequences for coordination of ingestive behavior.

Post-bariatric changes in ingestive behavior: Shift in macronutrient preferences in rats and dynamic adaptation of the within-meal microstructure in humans

This invited review is based on a presentation given at the Annual Meeting of the Society for the Study of Ingestive Behavior in July 2022 and provides the summary of two recent studies on changes in ingestive behavior following bariatric surgery (BS). First, long-term changes in daily absolute and relative macronutrient intake are reported in a rodent model of Roux-en-Y gastric bypass (RYGB). Rats undergoing RYGB progressively decreased their daily calorie- and daily fat intake compared to their preoperative baseline and to the intake of sham operated animals. Second, postbariatric changes in the within-meal ingestive microstructure are portrayed, based on longitudinal data collected in RYGB patients using a drinkometer. The post-RYGB meal size showed a dynamic adjustment process, with the highest decrease in the early postoperative phase, followed by a steady convalescence up to 1-year, at which point the meal size of RYGB patients became comparable to the normal weight adults’. Results are contextualized and contrasted to recent reports on the effect of BS on taste and food choices and consumption. The showcased evidence supports the role of ingestive adaptation and learning in the achievement of reduced calorie intake after RYGB, both in humans and in rodents. The reorganized upper-gastrointestinal anatomy supposedly leads to increased postingestive caloric sensibility, which might be an important behavioral mediator of decreased postbariatric meal size and consequent weight loss.

Avaliação da eficácia, inocuidade e depleção residual da flavomicina em novilhos confinados

Abstract Flavomycin is a non-ionophore additive little studied in finishing confined cattle. Therefore, this study aimed to evaluate the effectiveness of flavomycin on productive performance, ingestive behavior, carcass traits and biochemical parameters of steers finished in confinement. 32 whole steers, ½ Angus e ½ Nellore blood, from the same herd, with a mean age of 11 ± 1.5 months and initial body weight of 337 ± 6 kg were evaluated. The experiment was a randomized block design, consisting of two treatments and eight replications, as follows: Diet without flavomycin (control) and Diet with flavomycin (0.5 g FLAVIMPEX®80 animal day-1). There was no difference between treatments, the average dry matter intake of the animals was 10.03 kg day-1, feed efficiency was 0.158 kg, average daily gain was 1.593 kg day-1, apparent diet digestibility was 61.69%. The use of flavomycin was not effective in animal performance, and caused no changes in ingestive behavior and carcass traits of the animals. Total Plasma Protein, Aspartate amino-transferase and creatinine were lower for animals supplemented with flavomycin compared to the control group. In relation to the experimental period, there was a reduction in the levels of Total Plasma Protein, an increase in albumin, Gamma-Glutamyl Transferase and urea in cattle, but all remained within the reference range for the species.

Microbiota's Role in Diet-Driven Alterations in Food Intake: Satiety, Energy Balance, and Reward.

The gut microbiota plays a key role in modulating host physiology and behavior, particularly feeding behavior and energy homeostasis. There is accumulating evidence demonstrating a role for gut microbiota in the etiology of obesity. In human and rodent studies, obesity and high-energy feeding are most consistently found to be associated with decreased bacterial diversity, changes in main phyla relative abundances and increased presence of pro-inflammatory products. Diet-associated alterations in microbiome composition are linked with weight gain, adiposity, and changes in ingestive behavior. There are multiple pathways through which the microbiome influences food intake. This review discusses these pathways, including peripheral mechanisms such as the regulation of gut satiety peptide release and alterations in leptin and cholecystokinin signaling along the vagus nerve, as well as central mechanisms, such as the modulation of hypothalamic neuroinflammation and alterations in reward signaling. Most research currently focuses on determining the role of the microbiome in the development of obesity and using microbiome manipulation to prevent diet-induced increase in food intake. More studies are necessary to determine whether microbiome manipulation after prolonged energy-dense diet exposure and obesity can reduce intake and promote meaningful weight loss.

Microstructural changes in human ingestive behavior after Roux-en-Y gastric bypass during liquid meals.

BACKGROUNDRoux-en-Y gastric bypass (RYGB) decreases energy intake and is, therefore, an effective treatment of obesity. The behavioral bases of the decreased calorie intake remain to be elucidated. We applied the methodology of microstructural analysis of meal intake to establish the behavioral features of ingestion in an effort to discern the various controls of feeding as a function of RYGB.METHODSThe ingestive microstructure of a standardized liquid meal in a cohort of 11 RYGB patients, in 10 patients with obesity, and in 10 healthy-weight adults was prospectively assessed from baseline to 1 year with a custom-designed drinkometer. Statistics were performed on log-transformed ratios of change from baseline so that each participant served as their own control, and proportional increases and decreases were numerically symmetrical. Data-driven (3 seconds) and additional burst pause criteria (1 and 5 seconds) were used.RESULTSAt baseline, the mean meal size (909.2 versus 557.6 kCal), burst size (28.8 versus 17.6 mL), and meal duration (433 versus 381 seconds) differed between RYGB patients and healthy-weight controls, whereas suck volume (5.2 versus 4.6 mL) and number of bursts (19.7 versus 20.1) were comparable. At 1 year, the ingestive differences between the RYGB and healthy-weight groups disappeared due to significantly decreased burst size (P = 0.008) and meal duration (P = 0.034) after RYGB. The first-minute intake also decreased after RYGB (P = 0.022).CONCLUSIONRYGB induced dynamic changes in ingestive behavior over the first postoperative year. While the eating pattern of controls remained stable, RYGB patients reduced their meal size by decreasing burst size and meal duration, suggesting that increased postingestive sensibility may mediate postbariatric ingestive behavior.TRIAL REGISTRATIONNCT03747445; https://clinicaltrials.gov/ct2/show/NCT03747445.FUNDINGThis work was supported by the University of Zurich, the Swiss National Fund (32003B_182309), and the Olga Mayenfisch Foundation. Bálint File was supported by the Hungarian Brain Research Program Grant (grant no. 2017-1.2.1-NKP-2017-00002).

Behavioral Feeding Circuit: Dietary Fat-Induced Effects of Inflammatory Mediators in the Hypothalamus.

Excessive dietary fat intake has extensive impacts on several physiological systems and can lead to metabolic and nonmetabolic disease. In animal models of ingestion, exposure to a high fat diet during pregnancy predisposes offspring to increase intake of dietary fat and causes increase in weight gain that can lead to obesity, and without intervention, these physiological and behavioral consequences can persist for several generations. The hypothalamus is a region of the brain that responds to physiological hunger and fullness and contains orexigenic neuropeptide systems that have long been associated with dietary fat intake. The past fifteen years of research show that prenatal exposure to a high fat diet increases neurogenesis of these neuropeptide systems in offspring brain and are correlated to behavioral changes that induce a pro-consummatory and obesogenic phenotype. Current research has uncovered several potential molecular mechanisms by which excessive dietary fat alters the hypothalamus and involve dietary fatty acids, the immune system, gut microbiota, and transcriptional and epigenetic changes. This review will examine the current knowledge of dietary fat-associated changes in the hypothalamus and the potential pathways involved in modifying the development of orexigenic peptide neurons that lead to changes in ingestive behavior, with a special emphasis on inflammation by chemokines.

Diverging metabolic programmes and behaviours during states of starvation, protein malnutrition, and cachexia.

BackgroundOur evolutionary history is defined, in part, by our ability to survive times of nutrient scarcity. The outcomes of the metabolic and behavioural adaptations during starvation are highly efficient macronutrient allocation, minimization of energy expenditure, and maximized odds of finding food. However, in different contexts, caloric deprivation is met with vastly different physiologic and behavioural responses, which challenge the primacy of energy homeostasis.MethodsWe conducted a literature review of scientific studies in humans, laboratory animals, and non‐laboratory animals that evaluated the physiologic, metabolic, and behavioural responses to fasting, starvation, protein‐deficient or essential amino acid‐deficient diets, and cachexia. Studies that investigated the changes in ingestive behaviour, locomotor activity, resting metabolic rate, and tissue catabolism were selected as the focus of discussion.ResultsWhereas starvation responses prioritize energy balance, both protein malnutrition and cachexia present existential threats that induce unique adaptive programmes, which can exacerbate the caloric insufficiency of undernutrition. We compare and contrast the behavioural and metabolic responses and elucidate the mechanistic pathways that drive state‐dependent alterations in energy seeking and partitioning.ConclusionsThe evolution of energetically inefficient metabolic and behavioural responses to protein malnutrition and cachexia reveal a hierarchy of metabolic priorities governed by discrete regulatory networks.

Short communication: Tick-borne disease is associated with changes in feeding behavior in automatically fed weaned dairy calves

Tick-borne disease is a hemolytic disease complex that causes extensive losses to the dairy industry in tropical regions. Its timely diagnosis is challenging and labor intensive. Our objective was to investigate whether tick-borne disease was associated with changes in ingestive behavior of weaned dairy calves. Weaned calves (n = 35) enrolled at 108 ± 8 d of age were group housed (n = 12, 12, and 11/group) for 4 wk in the experimental pen, which had 12 electronic feed bins and 2 electronic water bins. Data were automatically collected at each feed or water bin visit via radio frequency identification ear tags. Water and total mixed ration were provided ad libitum. Calves were examined weekly for tick-borne disease detection. A disease bout was confirmed if packed cell volume was ≤25% at any exam. Diseased calves received antimicrobial and antipyretic treatment. Data were summarized by day within bin type (feed or water) as intake (kg/d; as-fed basis), frequency of visits (visits/d), and total duration of visits (min/d). Day of detection was set as d 0; a 9-d behavioral screening period for evaluation of behavioral changes was set according to d 0 (d -4 to +4). A within-calf mean was calculated for the healthy period (HP; mean of all days between 2 consecutive negative exams) for each response variable. Data were analyzed as within-calf differences between HP and each day of the behavioral screening period. Tick-borne disease was detected in 12 calves; thus, only data referent to these animals were included in the analyses. Compared with HP, daily feed intake was reduced on d -1, 0, and +1, and daily frequency and total duration of feed bin visits were reduced from d -3 to d +4. Daily feed intake was reduced by 35% on d -1 (3.5 ± 0.4 vs. 5.4 ± 0.5 kg/d for HP), and daily frequency and duration of visits were reduced by 27% (56.3 ± 7.8 vs. 76.7 ± 8.1 visits/d for HP) and 24% (27.0 ± 3.8 vs. 35.4 ± 3.9 min/d for HP) on d -3, respectively. Daily water intake on d 0 (9.1 ± 1.4 kg/d) was lower than at HP (12.9 ± 1.6 kg/d), but other drinking behaviors were not different from healthy means during the screening period. Feeding behavior, but not drinking behavior, was different from HP means before detection at weekly exams. Therefore, feeding behavior could be further explored for the development of algorithms for tick-borne disease detection.

Effect of multiple environmental stressors on the adaptive capability of Malpura rams based on physiological responses in a semi-arid tropical environment

A 45-day study was conducted where the primary objective was to evaluate the effect of simultaneously imposed multiple stressors (thermal, nutritional, and walking) on the adaptive capability of Malpura rams based on changes in ingestive behavior, physiological, blood biochemical, and endocrine responses. Twenty adult Malpura rams (average body weight 44.9 kg) were used in the study. The rams were divided into 2 groups, CON (n = 10; control) and multiple stressors (MS; n = 10; multiple stressors). All of the rams were stall fed with a diet consisting of 70% roughage and 30% concentrate. The CON rams were maintained in a shed under ambient conditions with ad libitum feeding without walking, whereas MS rams were subjected to multiple stressors (thermal, nutritional, and walking). The feed intake (P < 0.01) was lower and water intake (P < 0.01) was higher in MS compared to CON rams. Among the physiological measurements, respiration rate afternoon (P < 0.01), pulse rate morning (P < 0.01), rectal temperature afternoon (P < 0.01), skin temperature afternoon (P < 0.05), and both morning and afternoon scrotum temperature (P < 0.01) increased significantly in MS rams. Both hemoglobin (P < 0.05), packed cell volume (P < 0.01), increased and plasma glucose (P < 0.01) reduced significantly (P < 0.01) in MS as compared to CON rams. Among the endocrine parameters, the plasma cortisol increased and plasma thyroxin reduced significantly (P < 0.05) in MS rams. The study indicates that Malpura rams have the capability to adjust their physio-biochemical and endocrine responses to cope with multiple stressors in a hot semi-arid environment. Furthermore, the study also indicated that respiration rate, rectal temperature, scrotal temperature, hemoglobin, packed cell volume, and cortisol may act as ideal biological markers for quantifying the impact of multiple stressors in Malpura rams.

Comportamento ingestivo, consumo de forragem e desempenho de cabritas alimentadas com diferentes níveis de suplementação

O objetivo deste trabalho foi avaliar as alterações no comportamento ingestivo, consumo diário de forragem e desempenho de cabritas alimentadas com diferentes níveis de suplementação, em pastagem de aveia‑preta (Avena strigosa, 'IAPAR 61'). Foram utilizadas 36 cabritas da raça Boer, com 10 meses de idade e peso médio inicial de 21 kg, que receberam suplementação alimentar com milho moído e farelo de soja a 0, 0,5, 1 e 1,5% do peso vivo, em pastejo de lotação contínua com taxa de lotação variável. Utilizou-se o delineamento experimental de blocos ao acaso com três repetições. Foram avaliados: altura, taxa de acúmulo, massa, oferta e estrutura da pastagem; carga animal; ganho de peso individual e por área; e tempo de pastejo, ruminação e ócio (comportamento ingestivo); além do consumo de forragem. A suplementação diminuiu o consumo de forragem - 2,4, 1,45, 1,43 e 1,05% do peso vivo, nos tratamentos com 0, 0,5, 1 e 1,5%, respectivamente -, o tempo de pastejo diário e o ganho de peso individual. Os níveis de suplementação não alteraram o consumo total de matéria seca (forragem + concentrado) e nem o tempo de ruminação, mas aumentaram o tempo de ócio, o que permitiu maior desempenho dos animais por área.

Effect of menstrual cycle phase on corticolimbic brain activation by visual food cues

Food intake is decreased during the late follicular phase and increased in the luteal phase of the menstrual cycle. While a changing ovarian steroid milieu is believed to be responsible for this behavior, the specific mechanisms involved are poorly understood. Brain activity in response to visual food stimuli was compared during the estrogen dominant peri-ovulatory phase and the progesterone dominant luteal phase of the menstrual cycle. Twelve women underwent functional magnetic resonance imaging during the peri-ovulatory and luteal phases of the menstrual cycle in a counterbalanced fashion. Whole brain T2* images were collected while subjects viewed pictures of high calorie (HC) foods, low calorie (LC) foods, and control (C) pictures presented in a block design. Blood oxygen level dependent (BOLD) signal in the late follicular phase and luteal phase was determined for the contrasts HC–C, LC–C, HC–LC, and LC–HC. Both HC and LC stimuli activated numerous corticolimbic brain regions in the follicular phase, whereas only HC stimuli were effective in the luteal phase. Activation of the nucleus accumbens (NAc), amygdala, and hippocampus in response to the HC–C contrast and the hippocampus in response to the LC–C contrast was significantly increased in the late follicular phase compared to the luteal phase. Activation of the orbitofrontal cortex and mid cingulum in response to the HC–LC contrast was greater during the luteal phase. These results demonstrate for the first time that brain responses to visual food cues are influenced by menstrual cycle phase. We postulate that ovarian steroid modulation of the corticolimbic brain contributes to changes in ingestive behavior during the menstrual cycle.

Meal patterns and hypothalamic NPY expression during chronic social stress and recovery

In the present study, we examined meal patterns during and after exposure to the visible burrow system (VBS), a rodent model of chronic social stress, to determine how the microstructure of food intake relates to the metabolic consequences of social subordination. Male Long-Evans rats were housed in mixed-sex VBS colonies (4 male, 2 female) for 2 wk, during which time a dominance hierarchy formed [1 dominant male (DOM) and 3 subordinate males (SUB)], and then male rats were individually housed for a 3-wk recovery period. Controls were individually housed with females during the 2-wk VBS period and had no changes in ingestive behavior compared with a habituation period. During the hierarchy-formation phase of VBS housing, DOM and SUB had a reduced meal frequency, whereas SUB also had a reduced meal size. However, during the hierarchy-maintenance phase of VBS housing, DOM meal patterns did not differ from controls, whereas SUB continued to display a reduced food intake via less frequent meals. During recovery, DOM had comparable meal patterns to controls, whereas SUB had an increased meal size. Hypothalamic neuropeptide Y (NPY) mRNA levels were not different between these groups during the experimental period. Together, the results suggest that exposure to chronic social stress alters ingestive behavior both acutely and in the long term, which may influence the metabolic changes that accompany bouts of stress and recovery; however, these differences in meal patterns do not appear to be mediated by hypothalamic NPY.

Meal patterns, satiety, and food choice in a rat model of Roux-en-Y gastric bypass surgery.

Gastric bypass surgery efficiently and lastingly reduces excess body weight and reverses type 2 diabetes in obese patients. Although increased energy expenditure may also play a role, decreased energy intake is thought to be the main reason for weight loss, but the mechanisms involved are poorly understood. Therefore, the aim of this study was to characterize the changes in ingestive behavior in a rat model of Roux-en-Y gastric bypass surgery (RYGB). Obese (24% body fat compared with 18% in chow-fed controls), male Sprague-Dawley rats maintained for 15 wk before and 4 mo after RYGB or sham-surgery on a two-choice low-fat/high-fat diet, were subjected to a series of tests assessing energy intake, meal patterning, and food choice. Although sham-operated rats gained an additional 100 g body wt during the postoperative period, RYGB rats lost approximately 100 g. Intake of a nutritionally complete and palatable liquid diet (Ensure) was significantly reduced by approximately 50% during the first 2 wk after RYGB compared with sham surgery. Decreased intake was the result of greatly reduced meal size with only partial compensation by meal frequency, and a corresponding increase in the satiety ratio. Similar results were obtained with solid food (regular or high-fat chow) 6 wk after surgery. In 12- to 24-h two-choice liquid or solid diet paradigms with nutritionally complete low- and high-fat diets, RYGB rats preferred the low-fat choice (solid) or showed decreased acceptance for the high-fat choice (liquid), whereas sham-operated rats preferred the high-fat choices. A separate group of rats offered chow only before surgery completely avoided the solid high-fat diet in a choice paradigm. The results confirm anecdotal reports of "nibbling" behavior and fat avoidance in RYGB patients and provide a basis for more mechanistic studies in this rat model.

The relationship between birth weight and feeding maturation in preterm infants

To report changes in ingestive behaviour from 35 to 40 weeks post-conceptual age and examine the association between birth weight and feeding maturation in preterm infants. One hundred and four preterm infants born 24 to 34 weeks gestational age were studied. Feeding maturation was assessed as the change from 35 to 40 weeks post-conceptual age in the number of sucks over 5 min, sucking bursts, sucks per burst, time between bursts and maximum pressure during a suck (Pmax). The association between birth weight and each sucking behaviour was examined after adjusting for potential confounders. Significant changes in feeding maturation occurred between 35 and 40 weeks. Birth weight was positively associated with change in Pmax and change in number of sucks per burst for extremely premature infants born 24 to <29 weeks gestational age but not for very premature infants born >/=29 to 34 weeks. The association between birth weight and change in Pmax for extremely premature infants remained significant after adjustment (adjusted beta = 0.128 mmHg increase in change in maximum sucking pressure per every 1 g of birth weight, 95% CI = 0.017, 0.239, p = 0.03). Birth weight is positively associated with maturation in maximum sucking pressure among infants born extremely premature.

Evaluation of the effect of eprinomectin in young dairy heifers sub-clinically infected with gastrointestinal nematodes on grazing behaviour and diet selection

Inappetence is commonly associated with parasitism and has been observed in both housed and pastured ruminants. In seeking a functional explanation for these observations, it has been hypothesised that parasitized animals may feed more selectively in order to proportionally increase the protein content of their diet and thus partially compensate for their reduced feed intake. Support for this theory is found principally in studies in housed animals under carefully controlled experimental conditions. Grazing animals face a far more heterogeneous environment and a multiplicity of potentially confounding factors that could influence diet selection. Controlled grazing of adjacent monocultures of grass and clover can mitigate some of these variables and was used in the current study to examine the dietary preference of dairy heifers with sub-clinical parasitic gastroenteritis when compared to those receiving regular anthelmintic treatments. Grazing behaviour and herbage intake rates were determined through the use of jaw-movement recorders, direct observation and short-term liveweight change. Consistent with previous observations and despite evidence that nematode burdens were low in the untreated control heifers, a reduction in daily grazing time of 56 min ( P = 0.054) was observed in the control animals. There was, however, no evidence that the control heifers showed greater preference for clover compared with ryegrass: partial preference for clover was 73.0% in the untreated controls and 75.5% in the treated heifers. Furthermore control heifers were observed grazing the clover swards significantly ( P = 0.032) less frequently than the treated heifers. This study provides additional evidence in grazing cattle for parasite-induced inappetence, manifest as a reduction in grazing time and in subtle changes in ingestive behaviour. The observed partial preference for clover in both treated and control cattle was not significantly affected by the level of parasitism.

Feeding, body weight, and sensitivity to non-ingestive reward stimuli during and after 12-day continuous central infusions of melanocortin receptor ligands

The brain melanocortin system mediates downstream effects of hypothalamic leptin and insulin signaling. Yet, there have been few studies of chronic intracerebroventricular (i.c.v.) melanocortin receptor (MCR) agonist or antagonist infusion. Although there is evidence of interaction between melanocortin and dopamine (DA) systems, effects of chronic MCR ligand infusion on behavioral sensitivity to non-ingestive reward stimuli have not been investigated. The objective of this study was to investigate effects of chronic i.c.v. infusion of the MCR agonist, MTII, and the MCR antagonist, SHU9119, on food intake, body weight, and sensitivity to rewarding lateral hypothalamic electrical stimulation (LHSS) and the reward-potentiating (i.e., threshold-lowering) effect of d-amphetamine. The MCR antagonist, SHU9119 (0.02 μg/h) produced sustained hyperphagia and weight gain during the 12-day infusion period, followed by compensatory hypophagia and an arrest of body weight gain during the 24-day post-infusion period. At no point during the experiment was sensitivity to LHSS or d-amphetamine (0.25 mg/kg, i.p.) altered. The MCR agonist, MTII (0.02 μg/h) produced a brief hypophagia (3 days) followed by a return to control levels of daily intake, but with body weight remaining at a reduced level throughout the 12-day infusion period. This was followed by compensatory hyperphagia and weight gain during the 24-day post-infusion period. There was no change in sensitivity to non-ingestive reward stimuli during the infusion of MTII. However, sensitivity to d-amphetamine was increased during the 24-day post-infusion period. It therefore seems that changes in ingestive behavior that occur during chronic MCR ligand infusion may not affect the response to non-ingestive reward stimuli. However, it is possible that the drive to re-feed and restore body weight following MCR agonist treatment includes neuroadaptations that enhance the incentive effects of drug stimuli.

Modulation of Eating by Central Catecholamine Systems

The focus of the present review is the modulation of eating by the endogenous catecholamines (CA) dopamine (DA) and norepinephrine (NE). Topics addressed include pharmacological and genomic manipulations of brain CA systems and subsequent changes in ingestive behavior. DA in particular is a key component of brain reinforcement systems and feeding-associated changes in DA may play a role in the reinforcing aspects of feeding. NE has been linked to both stimulation and suppression of eating and recent evidence has linked these effects to activation of distinct adrenoceptor subtypes. Recent evidence suggests that NE systems may interact with DA systems to augment the activational effects of psychostimulant drugs, such as cocaine or amphetamine, and DA/NE interactions may play a key role in the capacity of psychostimulants to suppress eating.

Changes in ingestive behaviour of yearling dairy heifers due to changes in sward state during grazing down of rotationally stocked ryegrass or white clover pastures

A group of 12 Holstein×Friesian heifers were rotationally stocked in sequence on uninterrupted spring growths and regrowths following cutting of perennial ryegrass and then on regrowths of white clover. Measurements of ingestive behaviour and plant factors were made every 2–3 days during four grazing periods, which lasted between 12 and 20 days. The sward surface height in the ryegrass paddocks at the start ranged between 20 and 38 cm and contained 2.7–2.9 t DM ha −1 of green leaf mass. At the end of the grazing periods, the swards had a surface height of 8–9 cm, most of the leaf had been consumed and bite mass was considerably reduced compared with levels measured at the start. There was no change in eating time but ruminating time increased as the leaf:stem ratios declined. Total jaw movement rate during grazing declined, possibly because the heifers spent more time searching for leaves. Correlations between bite mass and plant factors suggested that total herbage mass was less useful for assessing likely levels of intake, than green leaf mass or sward surface height when managing grazed ryegrass swards, but total mass may have a place in predicting intake of white clover. Further, more detailed plant measurements indicated that the lengths of the 2nd and 3rd oldest fully expanded grass live leaves were significantly correlated with bite mass and this, along with the role of sheath tube lengths in defining the grazed horizon in ryegrass swards, warrants further investigation.

The CRF 1 receptor antagonist antalarmin reduces volitional ethanol consumption in isolation-reared fawn-hooded rats

Corticotropin releasing factor is a neuropeptide associated with the integration of physiological and behavioural responses to stress. More recently, corticotropin releasing factor has been implicated in the actions of abused drugs, including ethanol. Moreover, previous studies have demonstrated that the non-selective corticotropin releasing factor receptor antagonist, α-helical corticotropin releasing factor 9-41, can diminish some of the behavioural effects associated with ethanol withdrawal, whilst the selective corticotropin releasing factor 1 receptor antagonist CP-154,526 has been beneficial in decreasing stress-induced relapse into alcohol-seeking behaviour. However, as yet the ability of selective corticotropin releasing factor compounds to modulate volitional ethanol consumption has not been investigated. For these reasons the present study aims to examine the effects of antalarmin, a selective, centrally acting corticotropin releasing factor 1 receptor antagonist, on both the initiation and maintenance of ethanol consumption in isolation-reared Fawn-Hooded rats. Here we demonstrate that whilst both antalarmin and diazepam can decrease the acquisition of an ethanol-preferring phenotype by Fawn-Hooded rats, only antalarmin can alter established, volitional ethanol consumption. This ability of antalarmin to reduce established ethanol consumption is apparently unrelated to changes in ingestive behaviour, or a generalised anxiolytic action. For these reasons, such drugs may provide a new therapeutic approach for the treatment of alcoholism; however, this requires further investigation.

Effects of vagal and splanchnic section on food intake, weight, serum leptin and hypothalamic neuropeptide Y in rat

Truncal vagotomy can cause reduced food intake and weight loss in humans and laboratory animals. In order to investigate some of the factors that might contribute to this effect, we studied changes in ingestive behaviour, whole body and organ weights, serum leptin and hypothalamic neuropeptide Y in rats with bilateral vagal section, bilateral splanchnic nerve section and combined vagotomy plus splanchnectomy. Pyloromyotomy was combined with vagotomy to lessen effects of vagotomy on gastric emptying. Animals with vagotomy or vagotomy plus splanchnectomy lost weight and decreased their daily food intake relative to animals with splanchnectomy alone, rats with bilateral sham exposure of one or both nerve, or rats with pyloromyotomy alone. Serum leptin and white fat mass, 4 weeks after vagotomy, were about 20% of the values in the sham-operated animals at this time. No effect for splanchnic nerve section alone was observed. Pyloromyotomy caused no reduction in weight or fat mass, but reduced serum leptin. Following vagotomy with or without splanchnic nerve section, neuropeptide Y was elevated in the arcuate nucleus relative to values for the other four groups. Changes in neuropeptide Y were inversely correlated with levels of serum leptin. It is concluded that the effect of vagotomy could be due to the loss of a feeding signal carried by vagal afferent neurons, or to changed humoral signals, for example, increased production of a satiety hormone. However, it cannot be attributed to signals that reduce feeding (for example, gastric distension) reaching the central nervous system via the splanchnic nerves. The changes were sufficient to cause weight loss even though serum leptin was decreased, a change that would be expected to increase food intake.