Energy supplementation of steers grazing early-season, native range: effects on grazing and subsequent finishing performance and carcass merit

Crossbred beef steers (n = 328, initially 495 lb) were used to determine the effects of energy supplementation on grazing and subsequent finishing performance of steers grazing early-season, native range. Treatments consisted of either no supplemental energy or access to feeders containing a free choice, grain-based energy supplement. On the first day of the grazing period, steers were weighed and randomly allotted among eight pastures, providing four replications per treatment. Stocking density was 34% higher for supplemented than for unsupplemented pastures. At the end of the grazing period, steers were transported to a commercial feedlot and allowed ad libitum access to a common finishing diet for an average of 171 days. Supplement intake averaged 5.4 ± 1.1 lb/day (dry matter basis) or approximately 0.90% of body weight during the grazing period. Supplementation increased (P<0.01) grazing period gains from 1.47 to 2.20 lb/day. Supplementation also increased (P<0.01) ribeye area, back fat, and rump fat at the end of the grazing period. Supplementation did not affect subsequent finishing performance or carcass merit, but it reduced (P<0.01) time required for finishing by 18 days. Energy supplementation of steers grazing early-season, native range resulted in more pounds of gain per acre due to improved grazing performance as well as a 34% increase in stocking density

Efeitos de Fatores Ambientais na Reprodução de Tartarugas Environmental factors effects in turtles reproduction

Para as espécies de tartaruga que apresentam a determinação sexual dependente da temperatura da incubação o local e o momento da desova, exercem influências que vão além da definição do sexo dos embriões. A influência do local da desova se estende a todo o desenvolvimento embrionário afetando o comportamento e o tamanho dos filhotes. O momento em que ocorre a desova trará conseqüências ao ambiente térmico dos ninhos à medida que a temperatura e a umidade variam ao longo do ano. A umidade será decisiva nas trocas hídricas e gasosas entre os ovos e o meio afetando a absorção do vitelo e o crescimento dos embriões. As cheias e os alagamentos são importantes fatores de perda de ninhos nas espécies de tartaruga de água doce. A desova no momento adequado possibilita uma incubação segura, sem a interferência de alagamentos dos ninhos e conseqüente morte dos embriões. A predação dos ninhos varia de acordo com o local da desova, o tipo e a abundância de predadores e a profundidade da câmara de ovos. A escolha de pontos de desova no interior da vegetação, onde a taxa de predação é geralmente menor, nem sempre é a estratégia mais frequentemente adotada pelas tartarugas, uma vez que esse procedimento pode levar a uma maior exposição das fêmeas aos predadores, à diminuição do sucesso da eclosão ou a alterações na razão sexual provocadas por diferenças na temperatura da incubação.<br>Turtle species in which the sex determination is dependent of incubation temperature, the nest site and the laying moment will affect more than embryo sex determination. The influence of the laying site extends all over the embryonic development, affecting hatching weight and size. The time of the egg-laying will bring consequences to the nest thermal environment, as the temperature and humidity change throughout the year. The humidity will be decisive in gaseous and hydric exchanges between eggs and the environment, affecting yolk absorption and embryo growth. Floods and inundation are important factors related to nest loss in freshwater turtle species. Egg laying at the appropriated time makes a safe incubation possible, without the interference of nest inundation and subsequent embryo death. The nest predation varies according to the egg-laying site, type and abundance of predator and nest depth. The choice of areas in the middle of vegetation, where the predation rate is generally smaller, is not always the most used strategy by turtles, since this procedure can decrease the hatching success or provoke changes in sex ratio