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West Nile virus epidemics in North America are driven by shifts in mosquito feeding behavior.

West Nile virus (WNV) has caused repeated large-scale human epidemics in North America since it was first detected in 1999 and is now the dominant vector-borne disease in this continent. Understanding the factors that determine the intensity of the spillover of this zoonotic pathogen from birds to humans (via mosquitoes) is a prerequisite for predicting and preventing human epidemics. We integrated mosquito feeding behavior with data on the population dynamics and WNV epidemiology of mosquitoes, birds, and humans. We show that Culex pipiens, the dominant enzootic (bird-to-bird) and bridge (bird-to-human) vector of WNV in urbanized areas in the northeast and north-central United States, shifted its feeding preferences from birds to humans by 7-fold during late summer and early fall, coinciding with the dispersal of its preferred host (American robins, Turdus migratorius) and the rise in human WNV infections. We also show that feeding shifts in Cx. tarsalis amplify human WNV epidemics in Colorado and California and occur during periods of robin dispersal and migration. Our results provide a direct explanation for the timing and intensity of human WNV epidemics. Shifts in feeding from competent avian hosts early in an epidemic to incompetent humans after mosquito infection prevalences are high result in synergistic effects that greatly amplify the number of human infections of this and other pathogens. Our results underscore the dramatic effects of vector behavior in driving the transmission of zoonotic pathogens to humans.

Animals↗

Feeding behavior, milking behavior, and milk yields of cows milked in a parlor versus an automatic milking system.

This study compared feeding and milking behavior and milk yields for cows housed in the same barn, fed the same ration, but milked with a conventional milking parlor (parlor) or automatic milking system (robot). Behavioral data were videotaped hourly 1 d/mo for 9 mo. Feeding behavior patterns differed and were more variable for parlor cows than for robot cows. Both groups had low feeding rates at night and early morning. Feeding activity increased after milking and feed delivery for parlor cows. Milking and feeding activity in the robot system increased after human intervention at 7 a.m.; feed bunk activity peaked 3 h later and remained relatively constant from 10 a.m. to 8 p.m. Percentages of cows at the feed bunk were significantly greater for robot cows than parlor cows only at 10 a.m. and 9 p.m. Batch milking of parlor cows with free access to feed, vs. sequential milking of robot cows, with restricted movement to feed by a one-way gate system, resulted in higher peak percentages of cows at the bunk for parlor cows. Lower, more consistent percentages of cows eating at one time suggests that less bunk space may be needed for cows in robotic milking systems. Higher percentages of cows were observed in the robot from 8 a.m. to 1 p.m. and again from 3 to 7 p.m. Percentages of cows in the robot holding area were greatest from 8 to 11 a.m. and 3 to 6 p.m. and were lowest from midnight to 6 a.m. Milk production over 39 d in summer for subsets of cows was slightly but significantly higher (26.4 vs. 25.8 +/- 0.2 kg/d) for cows in the robot group. Milking frequency, days in milk, parity, and maximum air temperature for 3 d (-2 d to day of observation) affected milk yield comparisons. Results have implications for design of feeding and handling facilities used with automated milking systems.

Animals↗

Dose-response effects of intrauminal infusion of propionate on feeding behavior of lactating cows in early or midlactation.

The objective of this experiment was to evaluate whether dose-response effects of intraruminal infusion of propionate on feeding behavior and dry matter intake (DMI) differ by stage of lactation. Six cows in early lactation (EL) and six cows in midlactation (ML) were assigned to blocks in a duplicated 6 x 6 Latin square design experiment. Treatments were mixtures of sodium propionate and sodium acetate containing sodium propionate at 0, 20, 40, 60, 80, and 100% of total volatile fatty acids (VFA), infused into the rumen continuously for 18 h starting 6 h before feeding at a rate of 21.7 mmol of sodium VFA/min. All cows were ruminally cannulated prior to the experiment. The diet was formulated to contain 30% NDF, and dry cracked corn was the major source of starch. We hypothesized that hypophagic effects of propionate infusion were greater for EL compared with ML because of greater plasma concentration of nonesterified fatty acids (275 vs. 76 microMeq/L) and expected greater basal oxidative metabolism in the liver for EL compared to ML. Propionate infusion decreased DMI for EL and ML, but a quadratic effect of propionate infusion was observed for ML but not EL. This indicated a greater marginal reduction in DMI at higher doses of propionate for ML compared to EL, contrary to our hypothesis. Propionate infusion decreased meal size similarly for both stages of lactation, but linearly increased intermeal interval for ML but not EL. We speculate that lower milk yield for ML compared with EL (30.8 vs. 42.0 kg/d) decreased glucose demand by the mammary gland and increased the proportion of infused propionate oxidized in the liver for ML compared to EL.

3-Hydroxybutyric Acid↗

Brainstem mechanisms underlying feeding behaviors.

The essential elements controlling trigeminal motoneurons during feeding lie between the trigeminal and facial motor nuclei. These include populations of neurons in the medial reticular formation and pre-motoneurons in the lateral brainstem that reorganize to generate various patterns. Orofacial sensory feedback, antidromic firing in spindle afferents and intrinsic properties of motoneurons also contribute to the final masticatory motor output.

Animals↗

Feeding behavior and performance of dairy cows fed pelleted nonroughage fiber byproducts.

The potential of pellets made of soy hulls (SH) and corn gluten feed (CGF) to replace starchy pelleted supplement in diets of lactating cows was measured in a feeding regime comparable to automatic milking systems. Twenty-four cows were divided into 2 equal groups and fed for 7 wk in individual feeders monitored by computer on one of the 2 experimental diets. Both diets contained 75% basic total mixed ration plus an additional 25% of pelleted supplement (17% CP), being either high starch pellets (HST) in treatment, or pellets made of SH + CGF (2:1) (SHCG) in treatment. In vitro dry matter digestibility was higher in the HST pellets, whereas neutral detergent fiber (NDF) digestibility was higher in the SHCG pellets. The NDF content was higher in the SHCG diet. Individual cow behavior at the feeding lane was analyzed during the experimental period. Average number of meals and daily eating duration of the SHCG cows were significantly greater, as compared with the HST group. However, intake per meal and rate of eating were greater in the HST cows, whereas meal duration was similar in both groups. Feeding behavior resulted in significantly higher daily dry matter and NDF intake by the SHCG cows (27.1 and 11.1 kg, respectively) as compared with the HST group (24.8 and 7.61 kg, respectively). Consequently, significantly higher milk fat content, milk fat yield, and 4% FCM yield were obtained in the SHCG cows. Milk and milk protein yields were similar in both treatments. Data suggest potential advantages of the SHCG pellets for herds using automatic milking systems.

Animal Feed↗

Dopamine receptor subtype agonists and feeding behavior.

Stimulation or blockade of various dopamine receptor subtypes is associated with reduced feeding. For example, D2 receptor agonists suppress feeding in food-deprived and free-feeding rats, and in rats given access to a highly palatable diet. Similarly, reduced food intake is associated with the actions of diverse D1 receptor agonists, and these compounds can interact synergistically with D2 receptor agonists to potentiate reductions in feeding. Using microstructural analysis to compare D1 and D2 agonist effects, specific differences emerge in their modes of action. D1 agonists reduce the duration of feeding, primarily by decreasing the frequency of feeding bouts, whereas D2 agonists reduce the local rate of eating. However, since D1 agonists uniquely reduce feeding in the absence of other behavioral impairments and are less disruptive of the pattern of feeding behavior, it has been suggested that D1 agonists are more likely than D2 agonists to act on central mechanisms regulating food intake. Moreover, only D1 agonists are effective in suppressing sucrose sham-feeding, suggesting that D1 receptor stimulation may promote satiety. Nevertheless, many questions remain. For example, antagonist studies have implicated 5-HT receptor stimulation in the anorectic effects of D1 agonists, suggesting that further pharmacological and behavioral analyses of receptor-subtype agonist effects are required. Above all, recent developments in the classification of dopamine receptor subtypes reveal the need for new studies examining the involvement of D3, D4 and D5 receptors in feeding.

Animals↗

Feeding behavior of Ceratitis capitata (Diptera, Tephritidae): influence of carbohydrate ingestion.

Experiments were conducted on Ceratitis capitata larvae and adults to determine the influence of sugar (glucose and sucrose) ingestion on some aspects of the feeding behavior of this species. The results indicate that larval choice of a diet containing glucose or sucrose is not influenced by the rearing diet, by carbohydrate deprivation or by previous experience (induction). Carbohydrate deprivation did not alter the discrimination threshold of the larvae for sucrose. In adult females, the discrimination threshold for sucrose was unchanged when the flies were submitted to carbohydrate deprivation during the adult phase although ingestion by deprived females was 35% higher than ingestion by the control group. However, adults submitted to carbohydrate deprivation during the larval phase suffered a profound reduction in discrimination threshold for sucrose.

Journal Article↗

A microcomputer-controlled demand feeder for the study of feeding behavior in fish.

This paper describes an easy-to-make, low-cost demand feeder. The electromechanical design ensures a single-pellet delivery for each demand. The feeder, activated by a fish pressing a bar, is driven by a solenoid. A variety of pellet shapes and sizes can be used, offering broad experimental versatility. The feeder is also suitable for microcomputer control.

Animals↗