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This study determined whether early experiences by sheep to monotonous or diverse diets influence: (1) plasmatic profiles of cortisol, a hormone involved in stress responses by mammals, before and after an ACTH challenge, (2) the readiness to eat new foods in a new environment, (3) general fearfulness and response to separation--as measured by the open field test (OFT) and stress induced hyperthermia (SIH)--and (4) the link between (2) and (3). Thirty, 2-mo-old lambs were randomly assigned to 3 treatments (10 lambs/treatment). Lambs in one treatment (Diversity--DV) received in successive periods of exposure all possible 4-way choice combinations of 2 foods high in energy and 2 foods high in protein from an array of 6 foods: 3 high in energy (beet pulp, oat grain, and a mix of grape pomace:milo [40:60]) and 3 high in protein (soybean meal, alfalfa, corn gluten meal). Lambs in another treatment (DV+T) received the same exposure described for DV but two phytochemicals, oxalic acid (1.5%) and quebracho tannins (10%) were randomly added within any period of exposure to foods high in energy or to foods high in protein. Lambs in the third treatment (Monotony--MO) received a monotonous balanced ration containing all 6 foods fed to the other groups. After exposure, lambs were offered a choice of the aforementioned 6 foods (DV; DV+T) or the monotonous diet (MO). Lambs were intravenously injected with ACTH 1 h after food presentation, and sampled at 1, 2, and 3 h post feeding for determinations of plasma cortisol concentrations. Reluctance to eat novel flavored foods (onion-, coconut- and cinnamon-flavored wheat bran), open field behavior, and SIH was assessed in all treatments. Lambs in MO showed greater concentrations of plasma cortisol 1 h after food presentation than lambs in the DV or DV+T treatments (P=0.04). However, the difference was small and no differences among treatments were detected after an ACTH challenge (P>0.1). Lambs in DV consumed more onion-flavored wheat bran than lambs in MO (P=0.05). Lambs in DV also showed a greater cumulative consumption of novel flavors on d 2 than lambs in MO (treatment×day; P=0.01). Lambs in DV showed lower increase in rectal temperature (P=0.07) than lambs in MO. Only lambs in DV exhibited a positive relationship between consumption of cinnamon-flavored wheat bran and attempts of escape (R(2)=0.58; P=0.02). Our results suggest that exposure to diverse foods early in life may be less stressful than exposure to monotonous rations, as measured by plasma cortisol concentrations after food ingestion, and by changes in rectal temperature after exposure to the OFT. Lambs exposed to diverse diets early in life may also increase the initial acceptance of new flavors in novel environments relative to lambs exposed early in life to monotonous diets., (Published by Elsevier Inc.)

We learned previously that red-winged blackbirds (Agelaius phoeniceus) use affective processes to shift flavor preference, and cognitive associations (colors) to avoid food, subsequent to avoidance conditioning. We conducted three experiments with captive red-winged blackbirds to reconcile varied consequences of treated food with conditioned sensory cues. In Experiment 1, we compared food avoidance conditioned with lithium chloride (LiCl) or naloxone hydrochloride (NHCl) to evaluate cue-consequence specificity. All blackbirds conditioned with LiCl (gastrointestinal toxin) avoided the color (red) and flavor (NaCl) of food experienced during conditioning; birds conditioned with NHCl (opioid antagonist) avoided only the color (not the flavor) of food subsequent to conditioning. In Experiment 2, we conditioned experimentally naïve blackbirds using free choice of colored (red) and flavored (NaCl) food paired with an anthraquinone- (postingestive, cathartic purgative), methiocarb- (postingestive, cholinesterase inhibitor), or methyl anthranilate-based repellent (preingestive, trigeminal irritant). Birds conditioned with the postingestive repellents avoided the color and flavor of foods experienced during conditioning; methyl anthranilate conditioned only color (not flavor) avoidance. In Experiment 3, we used a third group of blackbirds to evaluate effects of novel comparison cues (blue, citric acid) subsequent to conditioning with red and NaCl paired with anthraquinone or methiocarb. Birds conditioned with the postingestive repellents did not avoid conditioned color or flavor cues when novel comparison cues were presented during the test. Thus, blackbirds cognitively associate pre- and postingestive consequences with visual cues, and reliably integrate visual and gustatory experience with postingestive consequences to procure nutrients and avoid toxins., (Published by Elsevier Inc.)

Fear, a key aspect of temperament with important implications for both animal welfare and production, may be manifest in responses to novelty. Herbivores typically prefer the familiar to the novel, and they generally regard anything novel with caution (i.e., they are reluctant to eat novel foods). We hypothesized animals differ in their fearfulness towards food and non-food items due to individuality which is influenced by genetics and contrasting environmental experiences. We further hypothesized fear of unknown foods and environments are correlated. Our objective was to determine if sheep differ in their fear responses and whether or not there is a link between general fearfulness and response to separation - as measured by the open field test (OFT) and stress induced hyperthermia (SIH) - and the readiness to eat new foods. We assessed reluctance to eat novel foods, open field behavior, and SIH in two groups of sheep (Group 1: Rambouillet-Columbia-Finn-Targhee crossbreds; Group 2: composite Suffolk) raised under contrasting environmental conditions. Lambs in Group 1 showed lower number of bleats and higher SIH than lambs in Group 2. When offered novel foods, lambs in Group 1 were more reluctant to eat them than lambs in Group 2. There was a negative relationship between number of bleats in OFT and reluctance to eat novel foods. Thus, reluctance to eat novel foods and response to separation in the OFT behavior differed among animals and a correlation was found between these behaviors. Our results suggest that reluctance to ingest new foods is influenced by sociality. Individuals less responsive to social isolation (lower number of bleats) may be less cautious at accepting novel foods than individuals more responsive to social isolation. Such variability implies some individuals may be more adept at consuming diverse diets in diverse locations whereas others may be more adept at consuming single foods at fixed locations.

The relationship between food flavors and postingestive feedback enables mammalian herbivores to procure nutrients and avoid toxins within ever-changing environments. We conducted four experiments with red-winged blackbirds (Agelaius phoeniceus) in captivity to determine the relative roles of color and flavor cues paired with negative postingestive feedback. We first conducted baseline tests to assess preferences for colors and flavors. All blackbirds preferred red- to blue-colored food, and they preferred umami- (l-alanine) flavored to bitter/astringent food (tannic acid). We observed no difference in consumption of salty (NaCl) vs sour (citric acid) foods during baseline tests (i.e., neutral flavors). We then conditioned experimentally naïve blackbirds with intraperitoneal injections of lithium chloride (LiCl) to avoid food treated with red and l-alanine, or red and NaCl (n=30 birds per conditioning group). Subsequent to conditioning with LiCl, three test groups were established from each conditioned group to evaluate color and flavor preferences, and preferences for novel color-flavor pairings (e.g., red/tannic acid vs blue/l-alanine). Blackbirds avoided red and salty food throughout the 4-day test. Avoidance conditioned with LiCl extinguished for preferred flavors, but not for colors, of food. Conditioning affected indifference for the otherwise preferred flavor and avoidance for the otherwise neutral flavor. Relative to the neutral-flavor conditioning group, the group conditioned with a preferred flavor exhibited stronger conditioned avoidance of colored food. Unlike conditioned flavor avoidance, birds were conditioned to avoid red food only when blue food was made familiar prior to conditioning. Collectively, these results illustrate that blackbirds used affective processes (flavor-feedback relationships) to shift preference for both novel and familiar flavors, and cognitive associations (colors) to avoid food, subsequent to toxin exposure. We discuss the opportunities afforded by affective and cognitive processing for reducing agricultural damage caused by blackbirds.

Burrow plugging is readily observed among mammals adapted for digging (i.e., fossorial mammals) as they create and maintain their burrows. We investigated the influence of light, burrow openings, and thermal environment as cues of pocket gopher (Thomomys mazama, Thomomys talpoides) behavior. When given free access to light and no light during artificial-burrow preference trials, both Thomomys spp. consistently plugged (i.e., avoided) light treatments. Burrow openings did not notably affect plugging behavior of T. mazama. Gophers (T. talpoides) plugged the artificial burrows within the light and cold (7 degrees C) treatments, but not within the no-light, and 18 or 31 degrees C treatments when light and temperature were varied independently. Whereas the presence of light and low ambient temperatures induce burrow maintenance by pocket gophers, these cues help meliorate adverse conditions within subsurface environs.

We discovered that a food aversion could be conditioned in anesthetized sheep. Sheep were allowed to eat a familiar food (alfalfa-grain pellets) for 30 min, and 90 min later they were given either an intraruminal (IR) injection of water (C), an IR injection of LiCl (L), anesthesia followed by an IR injection of water (A), or anesthesia followed by an IR injection of LiCl (A+L). Induction of anesthesia was by an intravenous injection of pentobarbitone sodium, and maintenance of deep anesthesia was by halothane. Sheep were maintained in deep anesthesia for 2 h to ensure that the effects of LiCl on the acquisition of a food aversion, which occur within about 1 h, were completed before they awakened. When tested 5 days later, sheep that received LiCl (treatments L and A+L) consumed less alfalfa-grain pellets than sheep that did not receive LiCl (treatments C and A) (241 g vs. 306 g; p = 0.057). Intake of sheep that were anesthetized (treatments A and A+L) did not differ from that of sheep that were not anesthetized (treatments C and L) (295 g vs. 252 g; p = 0.183). Nor was there an interaction between LiCl and anesthesia (p = 0.423). Thus, we conclude that changes in preferences for foods caused by postingestive feedback occur automatically every time food is ingested (i.e., they are noncognitive), and the kind and amount of feedback is a function of the match between the food's chemical characteristics and its ability to meet the animal's current demands for nutrients.

We investigated whether the odor of garlic can cross the placental barrier from the mother to the fetal environment. Samples of amniotic fluid, allantoic fluid, fetal blood, and maternal blood were collected 0, 50, 100, and 150 min after a pregnant ewe (approximately day 110 of gestation) was gavaged with 6 ml of Egyptian garlic oil. A panel of judges detected (p < 0.05) garlic odor in samples of allantoic fluid, fetal blood, and maternal blood collected 50, 100, and 150 min after the ewe was given garlic and in samples of amniotic fluid collected 100 min after treatment.