The hormonal responses of 20 female buffaloes raised under the sun (SS group) or in the shade (CS group) in Belém, Pará, Brazil, were assessed. The CS group (n = 10) was kept in a silvopasture system featuring Racosperma mangium, whereas the SS group (n = 10) was kept in paddocks without shade featuring Brachiaria humidicola, drinking water, and mineral salt. The following parameters were measured for each treatment: dry-bulb temperature (AT), relative humidity (RH), and black-globe temperature in order to calculate the globe temperature and humidity index (GTHI). Blood sample collections to quantitatively determine levels of cortisol, triiodothyronine (T3), and thyroxine (T4) were performed every 14 days, at 13.00 h. Different seasons of the year were also assessed: rainy (January-April), transition (May-July), and less rainy (August-December). Analysis of variance revealed that AT and the index of global temperature and humidity (GTHI) differed between groups; specifically, higher values were found in the SS group, which shows how important silvopastoral systems are in buffalo farming in tropical climates. Relative humidity was significantly different across seasons and particularly high in the rainy season. The treatments influenced cortisol such that higher values were observed in the SS group. The highest mean cortisol levels were recorded during the rainy and less rainy seasons, whereas the highest T3 and T4 levels were recorded only during the rainy season. Triiodothyronine and thyroxine were negatively correlated with AT and GTHI and positively correlated with RH. Silvopastoral systems provide thermal comfort to buffaloes, and the less rainy season is more likely to cause heat stress.

O objetivo do trabalho foi avaliar o efeito das alturas (8,9; 10,0; 11,2; 11,8; 13,3; 13,6; 14,6; 18,2 cm) de pastos consorciados de aveia IAPAR 61 (Avena strigosa Schreb cv IAPAR 61) com ervilha forrageira (Pisum arvense L.) sob pastejo sobre a relação folha/colmo (F/C), os teores de proteína bruta (PB), fibra em detergente neutro (FDN) e fibra em detergente ácido (FDA) e a digestibilidade in vitro da matéria seca (DIVMS) e da matéria orgânica (DIVMO). O delineamento experimental usado foi o inteiramente casualizado, com duas repetições. A relação F/C não foi influenciada pela altura do pasto, porém apresentou comportamento quadrático com o avanço na maturidade do pasto. Os teores de PB apresentaram comportamento quadrático ao longo do período experimental, devido à interação entre altura do pasto e o tempo. Os teores de FDN e FDA mostraram um comportamento quadrático ao longo do período experimental, ocorrendo uma diminuição dos mesmos quando as plantas se apresentavam mais baixas e, uma elevação, quando as plantas estavam mais altas, isto ocorreu em função da interação das variáveis tempo e altura. A DIVMS e a DIVMO tiveram incrementos lineares em função do aumento da altura do pasto, porém com comportamento quadrático no tempo (dias) em todas as alturas, sendo mais elevadas nas alturas intermediárias do pasto.

The objective of this work was to evaluate the effect of different sward heights (8.9, 10.0, 11.2, 11.8; 13.3; 13.6; 14.6; 18.2 cm) in the mixture of black oat IAPAR 61 (Avena strigosa Schreb cv IAPAR 61) + field pea (Pisum arvense L.), under grazing, on leaf/stem ratio (L/S), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents and dry matter (DMIVD) and of organic matter (OMIVD) in vitro digestibility. A completely randomized experimental design with two replicates was used. L/S ratio was not influenced by sward height, although it presented quadratic behavior with the progress of maturity of the pasture. CP content presented quadratic behavior during the experimental period, in function of the interaction between sward heights and the time. NDF and ADF contents had a quadratic behavior during the experimental period, with the occurrence of a decrease of it when the plants were shorter and an increase when the plants were higher, due the interaction between time and heights. IVDMD and IVOMD presented linear increments as a result of the increase of sward height, and a quadratic behavior as a consequence of the time in all sward heights, being higher in the average ones.