Effect of prolonged thermal exposure on heat production, reticular motility, rumen-fluid and -particulate passage-rate constants, and apparent digestibility in steers

Abstract

. 1992. Effect of prolonged thermal exposure on heat production, reticular motility, fumen-fluid and -particulate passage-rate constants, and apparent digestibility in steers. Can. J. Anim. . Six steers fitted with permanent rumen cannulae and fed alfalfa-grass hay were kept at either -10, l0 or 28"C for 21 d to evaluate the effects ofprolonged thermal exposue on heat production (HP) and digestive responses. HP was lowest at 28'C and increased significantiy (P < 0.05) as the ternperature was reduced to -10'C. The duration of the biphasic reticular contraction during resting was significantly (P < 0.05) reduced at -10'C (5.4 s) compared with that at 10"C (5.7 s) and 28"C (5.7 s) whereas duration and amplitude of biphasic reticular contractions during rumination were elevated at -10'C (P < 0.05). Apparent digestibilities of dry matter, orga4c matter, neutral detergent fibre and crude protein on average were 17% (range 9-16%) higher (P < 0'05) at 28 than at 10'C. The particulate passage-rate constant was higher at -10"C (P < 0.05) than at 10 and 28"C (0.046 vs. 0.038 and 0.034, respectively). The fluid passage-rate constant showed a quadratic response to temperature and was inversely related to digestibility. This study suggests prolong6e ir un regime thermique sur la production calorifique et sur la digestion. La production calorifique 6tait au plus bas d 28"C et augmentait significativement (P < 005) ir mesure que les temperatures descendaient jusqu'd -10"C. La dur6e de la contraction r6ticulaire biphas6e au repos 6tait significativement (P < 005) raccourcie d -10"C (5,4 s) par rapport )r 10 et d 28'C (5,7 s), mais durant la rumination elle 6tait significativement plus 6lev6e (P < 0,05) ir -10"C. La digestibilit6 apparente de la matidre sdche, de la matidre organique, des fibres au d6tergent neutre et des prot6ines brutes 6tait en moyenne ll% (6,cart 9{6) plus forle (P < 0,05) ir 28'C qu'h 10'C. La constante de transit des particules solides (par heure) 6tait plus haute d -10'C (P < 0,05) qu'd 10 et 28"C (0,046 contre 0038 et 0,034 respectivement). La constante de transit des liquides montrait une r6ponse quadratique ir la temp6rature et 6tait inversement reli6e ir la digestibilit6. L6tude porte d penser que les temp6ratures d'ambiance influent non seulement sur la cin6tique des matibres solides et des liquides mais 6galement sur la forme et sur la p6riodicit6 des contractions r6ticulaires. En outre, les modihcations thermo-induites de la dur6e et de l'amplitude des contractions r6ticulaires durant la rumination, par rapport d la phase, de repos 6taient associ6es ir des modifications des constantes du taux de transit des matibres solides.

Effect of vasoactive intestinal polypeptide and environmental temperatures on feed intake, digesta flow and nutrient digestion in sheep

“…2 in order to facilitate scheduling and intensive sampling and monitoring required. Although we cannot rule out the possibility that some of the effects attributed to temperature might have been due to period effects, the responses reported here are consistent with previous reports of temperature effects on digestion (Kennedy 1985;Miaron and Christopherson 1992).…”

“…On the other hand, the change in efficiency of microbial protein synthesis in the cold was consistent with that reported by Kennedy et al (1976). Miaron and Christopherson (1992) used the fixed-intake feeding strategy to avoid possible confounding effects of differences in feeding level with environment. They found a significant increase in water intake in steers in warm environments (10 and 28°C), compared to that of steers in the cold environment (-10°C).…”

“…Daily water consumption was measured by weighing fresh tap water offered and left over water once daily. A modification of the procedure described by Miaron and Christopherson (1992) was used for preparation of Crmordanted timothy hay. The markers, 18 g Cr-mordanted fiber and 3 g Co-EDTA, were administered three times daily through the rumen cannula starting one day before VIP treatment and continuing during four treatment days, for a total of 5 d. Duodenal digesta samples (50 to 100 mL) were collected four times per day on the fourth and fifth dosing day and frozen at -20°C.…”

“…Therefore, our hypothesis was that VIP might produce an effect on digesta passage and nutrient digestion in the gastrointestinal tract, thereby regulating feed intake in sheep with unlimited access to feed. In addition, we postulated that the response to VIP may be modified by environmental temperature because the cold temperature stimulates increased reticular motility (Miaron and Christopherson 1992).…”

“…Although similar results have been reported for animals on restricted intakes (Kennedy and Milligan 1978;Kelly et al 1989), this is the first comprehensive study of this type in ad libitum fed sheep. The increased passage of nutrients into the small intestine is presumably related to enhanced forestomach motility (Titchen 1968;Christensen et al 1991;Miaron and Christopherson 1992), but it may also be secondary to increased feed intake induced by the energy demand of the environment. Particulate DM passage into the duodenum accounted for 43-66% of DMI and tended to increase as feed intake increased in the present experiments, which is consistent with previous findings (Hogan 1975;Kennedy 1985).…”