Effects of heat exposure on nutrient digestibility, rumen contraction and hormone secretion in goats

Abstract

The present study investigated changes in nutrient digestibility, rumen fermentation, behavior and hormone (growth hormone (GH), insulin and insulin-like growth factor-1 (IGF-1)) secretion among goats (three male goats) in a hot environment (H, 35 ± 1.2 ∞ C; relative humidity (RH), 80 ± 7.2%; 13 days), in a thermoneutral environment (T, 20 ± 0.6 ∞ C; RH, 80 ± 3.4%; 20 days), and in a thermoneutral environment accompanied by the same restricted diet as provided in the hot environment (TR, 20 ± 0.6 ∞ C; RH, 80 ± 3.4%; 20 days). The following results were obtained: rectal temperature and water intake were higher in the H treatment than in the T treatment or TR treatment, while hay consumption was lower. Crude protein, neutral detergent fiber and acid detergent fiber digestibility was highest in H treatment. The concentrations of acetic acid and butyric acid in the rumen was also highest in the H treatment. Time spent eating in the H treatment was also the highest, followed in order by T treatment and TR treatment. Ruminating time was lower in H treatment than in T treatment or TR treatment, and reposing time was highest in the TR treatment. When eating and ruminating, the amplitude values of the rumen contraction were lowest in the H treatment, as was the frequency of rumen contraction. Excretion of plastic particles was faster in T treatment and TR treatment than H treatment. Heat exposure was associated with world lowered concentrations of total volatile fatty acids and acetic acid in plasma. The plasma glucose concentration was highest in the T treatment, followed in order by TR treatment and H treatment. The plasma GH concentration was lowest in the H treatment, while the plasma insulin was highest in the H treatment. The IGF-1 concentration was highest in the H treatment, followed in order by T treatment and TR treatment. In conclusion, heat exposure in goats decreased feed intake and rumen contraction, but increased digestibility. However, when goats in a thermoneutral environment received the same restricted feeding as they received in the hot environment, digestibility increased without a change in rumen contraction. Between the H treatment and TR treatment, the changes in digestibility were accomplished by coordinate changes in hormone secretion in order to maintain body homeostasis.

Heat stress and ACTH administration on cortisol and insulin-like growth factor I (IGF-I) levels in lactating Holstein cows

“…Similar results were previously described (McGuire et al 1991;Hirayama et al 2004;Chaiyabutr et al 2008). Other authors, in opposition to the aforesaid, reported that bovine somatotropin treatment, under heat stress, increased milk production, IGF-I release and RT in dairy cows (Sarko et al 1994;Jousan et al 2007).…”

“…In the present study, however, IGF-I concentrations were not influenced by ACTH administration or increase in plasma CORT concentration. In the same way, other authors also demonstrated that IGF-I levels during heat stress are similar to those obtained within the zone of thermal comfort (McGuire et al 1991;Hirayama et al 2004;Collier et al 2008). In fact, the relation between IGF-I and heat stress remains controversial.…”

“…In the same way, while some authors have reported that growth hormone (GH) and insulin-like growth factor I (IGF-I) are negatively influenced by heat stress (Sarko et al 1994;Rhoads et al 2010;Wheelock et al 2010), others mentioned that IGF-I levels during heat stress are similar to those obtained within thermal comfort zone (McGuire et al 1991;Hirayama et al 2004;Chaiyabutr et al 2008;Collier et al 2008). For these reasons, the interactions between heat stress and CORT and between IGF-I and environmental heat remain controversial.…”

Degradabilidade in situ do rolão e farelo de milho em caprinos e ovinos deslanados mantidos em sombra natural e artificial no semi-árido paraibano

“…Esses resultados estão de acordo com Hirayama et al (2004) que obtiveram maior digestibilidade da FDN nos animais que estavam em ambiente de desconforto térmico. O inverso ocorreu na fração C, no ambiente natural houve maior insolubilidade (P<0,05) da FDN (43,76%) do que no artificial (38,67%).…”

Capacidade termolítica e respostas comportamentais e hormonais em vacas Holandesas.

“…Embora vários autores já observassem que o estresse calórico promoveu aumento significativo nos níveis plasmáticos de cortisol (ALNAIMY et al, 1992;ARCARO, 2005;DU PREEZ, 2000), o efeito do meio ambiente sobre os níveis plasmáticos de IGF-I permanece controverso, pois alguns autores relatam que o estresse calórico foi associado à redução dos níveis plasmáticos de IGF-I ( ARMARIO et al, 1987;McCUSHER, 1998;PEISEN et al, 1995;STRAUS, 1994), enquanto outros autores relatam que o estresse calórico aumentou significativamente os níveis plasmáticos de IGF-I (HIRAYAMA et al, 2004) Christison e Johnson (1972) reportaram a diminuição da concentração plasmática de cortisol em vacas após exposição prolongada a altas temperaturas ambiente, queda também encontrada por Ronchi et al (2001). A redução do cortisol é relacionada a um mecanismo de adaptação.…”