Thermogenic and digestive responses of ad libitum fed pigs to α₂-adrenergic stimulation with guanfacin in different thermal environments

Abstract

2002. Thermogenic and digestive responses of ad libi-tum fed pigs to α α 2-adrenergic stimulation with guanfacin in different thermal environments. Can. J. Anim. Sci. 82: 79-86. Guanfacin, an α 2-adrenoceptor agonist, reduces heat production in cold-stressed, but not heat-stressed animals. Growth rate, feed intake, metabolic rate, ileal and fecal digestibility were measured in 16 pigs, housed in neutral (20.4 ± 1.7°C), hot (32.7 ± 1.6°C) or cold (6.6 ± 1.4°C) environments. For ileal digestibility determination, pigs received 80 mg kg-1 d-1 followed by 3 × 40 mg kg-1 d-1 of guanfacin or saline, within their own environment, in a cross-over design. Fecal digestibility and heat production were measured over 7 d with treatments applied in a cross-over design of two periods. Oxygen consumption (VO 2) was determined by open circuit respiration calorime-try. Cold-housed pigs had higher feed intakes (P < 0.05), but not growth rates, compared with those in the thermoneutral environment. Pigs in the hot environment had lower feed intakes, weight gains and heat production (P < 0.05) and higher rectal temperatures (P < 0.05) compared to those in the other two environments. Guanfacin did not reduce heat production in swine in any environment. Pigs in the cold and neutral environments had lower (P < 0.05) fecal dry matter (DM) digestibility. Pigs in the cold had lower fecal gross energy (GE) digestibility (P < 0.05) compared to those in the hot, and lower fecal crude protein (CP) digestibility (P < 0.05) compared to those in the neutral or hot environments, probably due to changes in digesta retention in the large intestine. Temperature did not affect ileal digestibil-ity of DM, GE, CP and amino acids. Guanfacin did not affect fecal digestibility, but increased ileal DM and GE digestibility (P < 0.05) across all temperatures, possibly by affecting smooth muscle contraction and rate of passage. Increased ileal energy digestibility without a change in heat production suggests an improvement in utilization of DE in response to guanfacin. Key words: α 2-adrenoceptor agonist, digestibility, pig, environment, heat production, ileum Cosgrove, S. J., Mosenthin, R., Christopherson, R. J., Li, B. T. et Sauer W. C. 2002. Réaction thermogénique et digestive des porcs nourris à satiété à la stimulation α α 2-adrénergique par la guanfacine à divers régimes thermiques. Can. J. Anim. Sci. 82: 79-86. La guanfacine, agoniste des récepteurs α 2-adrénergiques, diminue la production de chaleur chez les animaux qui subissent un stress dû au froid, mais pas chez ceux soumis à un stress thermique. Les auteurs ont déterminé le taux de croissance, la prise alimentaire, le taux métabolique et la digestibilité iléale et fécale chez seize porcs logés à une température neutre (20,4 ± 1,7°C), élevée (32,7 ± 1,6°C) ou basse (6,6 ± 1,4°C). Pour mesurer la digestibilité iléale, on a donné aux animaux 80 mg kg-1 puis 3 × 40 mg kg-1 de guanfacine ou de saline par jour dans leur environnement, selon un plan croisé. La digestibilité fécale et la production de cha...

Characterizing the acute heat stress response in gilts: I. Thermoregulatory and production variables

“…Another potential explanation is variation in digesta passage rates during HS. Heat-stressed pigs are thought to have improved digestibility (Collin et al, 2001;Cosgrove et al, 2002), which is attributed to slower solids passage rate (Christopherson and Kennedy, 1983), but whether or not this contributes to the variation in production responses (i.e., ΔBW) during acute HS will require further investigation. Each gilt's tolerance to the heat load was classified on the basis of HS rectal temperature (T R ; i.e., higher and lower HS T R were considered markers of HS susceptibility or tolerance, respectively).…”