Roura, E., Humphrey, B., Tedo´, G. and Ipharraguerre, I. 2008. Unfolding the codes of short-term feed appetence in farm and companion animals. A comparative oronasal nutrient sensing biology review. Can. J. Anim. Sci. 88: 535Á558. The evolution of the chemical senses has resulted in a sensory apparatus for high taste and smell acuity in mammals and birds to ensure self-nourishment. Such peripheral chemosensory systems function as a code to unfold the nutritional value of feedstuffs. Food ingestion simultaneously evokes odor, taste and thermo-mechanical (somatosensing) sensations. Olfaction represents the capacity to identify feed volatiles that are predominantly derived from essential nutrients in plants.Comparative biology of olfaction shows that primates and chickens have a smaller olfactory epithelium and fewer olfactory receptor (OR) genes than non-primate mammals studied to date including farm and companion animals, such as the pig, the cow, the dog, the cat and the horse. A significant proportion of the total OR genes in mammals and birds have lost their functionality (pseudogenes) in a process that seems to reflect a decrease in the animal's reliance on the sense of smell, particularly in humans and cows. The taste system allows animals to recognize a diverse repertoire of nutrient (sugars, amino acids, salts, acids and fats) or toxic related chemical entities that provide valuable information about the quality of food. Taste senses non-volatile molecules in the oral cavity through taste receptors (TR). The TR are expressed in the sensory cells forming the taste buds of the tongue's papillae. Taste cells are linked to a network of solitary chemosensory cells diffused through many non-taste tissues involved in metabolic homeostasis. The number of functional taste receptor genes (TASR) in humans is equivalent to that in other mammals and superior to that in chickens. The TASR family 1 (TAS1R coding for umami and sweet TR) is conserved, in number and type, across the species evaluated, with the exception of the sweet receptor in chicken and feline species. The TASR family 2 (TAS2R coding for bitter TR) shows a strong adaptive capacity to dietary sources and digestive physiology across vertebrates. Pseudogenization (loss of gene functionality) in the TAS2R family seems to be a frequent strategy. The implications of oronasal nutrient sensing related to comparative animal feeding strategies and behaviors such as neophobia, feed refusal and hedonic preferences are discussed. Feed palatability and appetence might be one of the main driving forces in short-term feed consumption. Finally, practical applications relevant to animal production are outlined.Key words: Nutrient sensing, taste, olfaction, somatosensing, feed intake, farm, companion animals Roura, E., Humphrey, B., Tedo´, G. et Ipharraguerre, I. 2008. Le code de l'appe´tence a`court terme chez les animaux domestiques et de compagnie. Biologie comparative de la de´tection bucco-nasale des e´le´ments nutritifs. Can. J. Anim. Sci. 88: 535Á558. En e´voluant, ...

Feeding behavior in dairy cattle has a significant impact on feed efficiency, which is important for increasing the profitability of livestock and, at the same time, reducing the environmental impact. Feeding behavior can be measured by feeding time, meal duration, meal frequency, feeding rate, and rumination time. Higher feed intake is related to lower feed efficiency; whereas, an increase in feeding time facilitates chewing, reduces feed particle size and increases its digestibility. More frequent and shorter meals are usually associated with a more efficient use of feed due to improvement of feed digestibility. Rumination time is positively associated with milk production. Impaired health is associated with variations in feeding behavior, which can be used to identify and predict some diseases such as ketosis, mastitis, or lameness. Changes in rumination time are also a reliable indicator of mastitis, lameness, ketosis, abomasal displacement, and the onset of calving. In addition to the cause-effect relationship between disease and changes in feeding behavior, there are also some cases in which changes in feeding behavior may lead to an increased risk of disease, as exemplified by the relationship of feeding rate with sub-acute ruminal acidosis. Feeding behavior is regulated by internal and external factors and some of them are relevant for animal welfare. The main welfare-associated factors influencing feeding behavior are social behavior and temperament, and environmental effects. Cattle are social animals and hierarchy has a notable impact on feeding behavior, especially when access to feed is limited. Competition for feed causes a reduction in the average feeding time but increases feeding rate. Excitable animals visit the feeder more often and spend less time per meal. High environmental temperature affects feeding behavior, as heat-stressed cattle change their feeding pattern by concentrating the feeding events in crepuscular hours, leading to an increased risk of sub-acute ruminal acidosis. In conclusion, feeding behavior is a determinant feature for improving efficiency, productivity and welfare of dairy cattle. Routine assessment of feeding behavior allows monitoring of health and production status of dairy cattle at the individual and farm level, which is a useful tool to optimize the management of livestock.

Early weaning is a stressful event characterized by a transient period of intestinal atrophy that may be mediated by reduced secretion of glucagon-like peptide (GLP) 2. We tested whether enterally fed bile acids or plant sterols could increase nutrient-dependent GLP-2 secretion and improve intestinal adaptation in weanling pigs. During the first 6 d after weaning, piglets were intragastrically infused once daily with either deionized water (control), chenodeoxycholic acid (CDC; 60 mg/kg body weight), or β-sitoesterol (BSE; 100 mg/kg body weight). Infusing CDC increased plasma GLP-2 (P < 0.05) but did not affect plasma GLP-1 and feed intake. The intestinal expression of glucagon-like peptide 2 receptor, sodium-dependent bile acid transporter, farnesoid X receptor, and guanosine protein-coupled bile acid receptor genes were not affected by CDC treatment. The intragastric administration of CDC did not alter the weight and length of the intestine, yet increased the activation of caspase-3 in ileal villi (P < 0.02) and the expression of interleukin 6 (P < 0.002) in the jejunum. In contrast, infusing BSE did not affect any of the variables that were measured. Our results show that the enteral administration of the bile acid CDC potentiates the nutrient-induced secretion of endogenous GLP-2 in early-weaned pigs. Bile acid-enhanced release of GLP-2, however, did not result in improved intestinal growth, morphology, or inflammation during the postweaning degenerative phase.

BackgroundPrevious work showed that weaning stress causes gut barrier dysfunction partly by triggering the release of corticotropin releasing factor (CRF) and thereby inducing the degranulation of intestinal mast cell (MC). This study investigated the hypothesis that attenuating the weaning-induced activation of the CRF-MC axis via administration of a MC stabilizing agent (cromolyn) may improve gut permeability and piglet performance after weaning.ResultsTo test the hypothesis twenty piglets were weaned (20 ± 1.0 d of age; 6.4 ± 0.4 kg of BW) and injected intraperitoneally with saline (control, n = 10) or 20 mg/kg BW of sodium cromolyn (cromolyn, n = 10) at – 0.5, 8 and 16 h relative to weaning. Piglets were housed individually and fed ad libitum a pre-starter diet from one to 15 d post-weaning followed by a starter diet until the end of the study on d 36. Cromolyn improved intestinal permeability as indicated by the reduced recovery of cobalt and mannitol in plasma samples. Cromolyn treated pigs consumed more feed (369 vs. 313 g/d; P < 0.009), gained more BW (283 vs. 238 g/d; P < 0.006), and grew more efficiently (0.60 vs. 0.40; P < 0.042) than their control counterparts. As a result, cromolyn treated pigs were 1.4 kg heavier than those in the control group by d 36 after weaning (16.5 vs. 17.9 kg; P < 0.002).ConclusionsIn agreement with our hypothesis, present data indicate that the cromolyn-mediated improvement of intestinal permeability is associated with enhanced pig performance after weaning.

The intense nature of pig production has increased the animals’ exposure to stressful conditions, which may be detrimental to their welfare and productivity. Some of the most common sources of stress in pigs are extreme thermal conditions (thermal stress), density and mixing during housing (social stress), or exposure to pathogens and other microorganisms that may challenge their immune system (immune-related stress). The stress response can be monitored based on the animals’ coping mechanisms, as a result of specific environmental, social, and health conditions. These animal-based indicators may support decision making to maintain animal welfare and productivity. The present study aimed to systematically review animal-based indicators of social, thermal, and immune-related stresses in farmed pigs, and the methods used to monitor them. Peer-reviewed scientific literature related to pig production was collected using three online search engines: ScienceDirect, Scopus, and PubMed. The manuscripts selected were grouped based on the indicators measured during the study. According to our results, body temperature measured with a rectal thermometer was the most commonly utilized method for the evaluation of thermal stress in pigs (87.62%), as described in 144 studies. Of the 197 studies that evaluated social stress, aggressive behavior was the most frequently-used indicator (81.81%). Of the 535 publications examined regarding immune-related stress, cytokine concentration in blood samples was the most widely used indicator (80.1%). Information about the methods used to measure animal-based indicators is discussed in terms of validity, reliability, and feasibility. Additionally, the introduction and wide spreading of alternative, less invasive methods with which to measure animal-based indicators, such as cortisol in saliva, skin temperature and respiratory rate via infrared thermography, and various animal welfare threats via vocalization analysis are highlighted. The information reviewed was used to discuss the feasible and most reliable methods with which to monitor the impact of relevant stressors commonly presented by intense production systems on the welfare of farmed pigs.