Intake, performance, and feeding behavior of Holstein and Holstein × Gyr heifers grazing intensively managed tropical grasses during the rainy season

Comparison of ruminal microbiota, IL-1β gene variation, and tick incidence between Holstein × Gyr and Holstein heifers in grazing system

“…The temperature-humidity index (THI) ranged from 68.8 to 72. Detailed information on weather data in each period was described by Quirino et al (2022) .…”

“…The accumulated herbage per paddock (88.5 ± 5.13) and herbage allowance (11.0 ± 0.63) increased during periods and the major herbage accumulation occurred in periods 3 and 4 with DM of 27.4% and 25.8%, respectively, while grazing efficiency was superior (63.3%) when neutral detergent fiber was inferior (66.0%). Thus, the intake was not limited by forage allowance ( Quirino et al, 2022 ).…”

“…The present study was conducted to investigate factors contributing to the better performance of Holstein × Gyr heifers compared to Holstein heifers under tropical pastures. Previously, Quirino et al (2022) highlighted greater average daily gain and feed efficiency for Holstein × Gyr than Holstein heifers managed in an intermittent grazing system of Guinea grass ( Panicum maximum Jacq. cv.…”

“… Menezes et al (2011) observed a predominance of Prevotellaceae, Erysipelotrichaceae, and Veillonellaceae in grazing cows, while cows fed a total mixed ration had a predominance of Fibrobacteriaceae. However, a comparison between ruminal microbiota from crossbred (Holstein × Gyr) and purebred Holstein heifers in grazing systems has not yet been demonstrated, which might help explain the differences in digestibility, beyond feeding behavior, reported in previous studies ( Oliveira Filho et al, 2018 ; Silvestre et al, 2021 ; Quirino et al, 2022 ). Thus, changes in ruminal microbiota and tick infestation potentially reduce the productivity of grazing animals, especially in Holstein animals.…”

“… Abreu et al (2022) suggested that Holstein heifers have less heat tolerance, demonstrated by the greater bite rate (20 vs. 17.3), and shorter grazing time spent in each meal compared to crossbred heifers. Therefore, the variation in performance of Holstein × Gyr and Holstein heifers might be explained by the ability to graze in high temperatures, which consequently impacts time spent in grazing and resting ( Quirino et al, 2022 ), resistance to ectoparasites, and susceptibility to infectious diseases ( Otto et al, 2018 ). Beyond the suggested differences above, we speculate that susceptibility to diseases and grazing behavior would also cause a significant change in the ruminal microbiota, which could impact the intake and performance of grazing animals ( Uyeno et al, 2010 ).…”