Holstein steers grazing two Bermudagrass varieties in hot and dry summer: forage quality and physiological responses of steers
M. Joseph1,2, L. Avendaño-Reyes1*, E.G. Álvarez-Almora1, U. Macías-Cruz1, G. Tilus1, 2, J.E. Guerra-Liera3, J.A. Aguilar-Quiñonez3, S. Wittayakun4 and A. Correa-Calderón1
J. Sci. Agri. Technol. (2021) Vol. 2 (2): 32-42
DOI: https://doi.org/10.14456/jsat.2021.10
Abstract
The objective was to evaluate the forage quality of two varieties of Bermudagrass and some physiological traits of Holstein steers during two grazing periods in summer in an arid zone. Twenty-four Holstein steers (BW=200 ± 5 kg), 20 intact animals, and 4 with rumen cannulas were randomly assigned for grazing to the Bermudagrass varieties Cross 1 (BC1, n=12) and Giant (BG, n=12) in two consecutive periods (P1 and P2) during the summer-fall season in northwestern México. Based on the temperature-humidity index, the climate in P1 was considered as severe heat stress and P2 as moderate heat stress. Levels of CP and ash were higher (P<0.05) in BG during P2. Contents of NFD, AFD, and hemicellulose were higher (P<0.01) in BG during P2 than BC1 during P1, respectively. Only fat content was higher (P<0.05) in BC1 than BG. The in vitro digestibility of dry and organic matters showed no differences (P>0.05) between varieties or periods. Respiration frequency and all body surface temperatures were higher during the first grazing period and in the afternoon, which coincides with the hottest grazing period and time of day. In conclusion, climatic conditions of the site of the study along with a poor quality of Giant and Cross 1 Bermudagrass varieties under grazing conditions, make the nutritional supplement recommended to reach satisfactory results for growing cattle.
Keywords: Bermudagrass, forage digestibility, grazing pastures, heat stress, Holstein steers
Received: July 30, 2021. Revised: October 11, 2021. Accepted: October 18, 2021.
