Respostas produtivas e fisiológicas de bovinos mestiços de origem leiteira e Nelore submetidos a ambiente sombreado ou a pleno sol.

Abstract

The aim of this study was to evaluate the shaded environments and full sun in cattle crossbred of origin dairy and Nelore feedlot finished and through the environmental variables (temperature and humidity) and through of thetemperature and humidity index (THI), characterize its effect on nutrient intake, performance, indicators biochemical , consumption dry mater by period of day, water intake and feeding behavior. Were used 32 bulls, 16 crossbred from crosses between breeds with milk aptitude (crossbred of origin dairy) and 16 Nelore, with about 24 months old and with weight average of the 325.6 kg. The animals were confined individually for 84 days, distributed in a completely randomized design in a factorial arrangement 2 x 2 (two environments and two genetic groups) with eight replications. The animals of shadow treatment were placed in confinement covered by tile asbestos cement, stalls made wooden , concrete floor, individual feeder and drinking fountain for every two stall. The treatment animals the sun full were placed in the open confinement, made of wire, dirt floor, feeder and fountain drinking individual. To evaluate the temperature and humidity index were collected temperature and humidity every 15 minutes, the temperature of body surface and respiratory rate were held weekly in two periods: 06:00h to 09:00h and 13:00h to 15:00h. The dry matter intake, nutrients and performance were not affected by treatments. The animals Nellore had higher apparent digestibility of dry matter and non-fibrous carbohydrates in the environment shaded, of 0.73 and 0.87, respectively. Consumption of NDT was not affected by treatments averaging 6.33 kg.dia-1 . The average daily gain and final weight were 448.16 kg and 1.48 kg.dia-1 , respectively. The temperature and humidity index (THI) in the period of 06:00h at 17:45h were similar in both environments, ranging from 70 to 82. The temperature of body surface was higher in the animals of the shadow in the period from 06:00h to 09:00h, and in the period from 13:00h at 15:00h, the animals crossbred of the sun had higher body surface temperature. The respiratory rate was lower in the period from 06:00h to 09:00h (32 and 29 beats/min) and 13:00h to 15:00h (35 and 55 beats/min) for Nellore and crossbred animals, respectively. The biochemical indicators glucose, urea, creatinine and alanine transaminase (ALT) were above the reference range for cattle. The animals of environment sun full consumed 11% dry matter the more in the period from 12:00h to 16:00h and crossbred of the sun ingested more water. The biggest chewing time per bolus was to the animals of the shadow , and the daily chewing time was higher for the crossbreds. The number of cakes chewed per day, the rumination efficiencies of dry matter and fiber of rumination neutral detergent were higher for the animals of the full sun. Possibly the type of installation in shadind environment may have changed the pattern of productive response of animals, supported by bioclimatic index (ITH) similar in both environments.