Prediction of Animal Performance on Bermudagrass Pasture from Available Forage¹

Abstract

Bermudagrass [Cynodon dactylon (L.) Pers.] is a major warmseason perennial grass grown on improved pastures in the South. Available forage and its digestibility vary widely in a normal grazing season on bermudagrass pasture. A method is needed to predict steer (Bos sp.) gains from the amount and digestibility of available forage. Five bermudagrass cultivars differing in digestibility were grazed at different grazing pressures to produce four levels of available forage. Forage was classified by concentration of in vitro digestible dry matter (IVDDM) as high (>600 g kg−1 IVDDM), medium (530 to 600 g kg−1 IVDDM), or low ( <530 g kg−1 IVDDM) digestibility. At each level of IVDDM, average daily gain (ADG) of steers was fitted to an asymptotic function of available forage. On high, medium, and low digestibility forages, approximate asymptotic ADG values were 0.94, 0.74, and 0.31 kg, and 68,83, and 89 g forage kg−1 body weight day−1, respectively, were needed to produce the asymptotic ADG values. For steers to maintain their weight on high, medium, and low digestibility forage, 14,18, and 43 g forage dry matter kg−1 body weight day−1, respectively, must be present. Because the quantities of available forage required for maximum steer gains or even for maintenance were far in excess of what the steers could physically consume, it appears that opportunity for selective grazing is necessary.

Interrelationships among Forage Nutritive Value and Quantity and Individual Animal Performance

“…It was interesting to note that length of grazing season did not affect SLOPE. Others have reported a significant association between length of the grazing season and the magnitude of the SR effect (Gerrish, 2000). Gain responses to SR are more evident late in the grazing season, as forage quantity becomes more limiting.…”

“…Meta‐analysis is a tool for assessing relationships across a group of studies; therefore, meta‐analysis was applied to a large collection of U.S. pastureland data to broaden the database for drawing conclusions about the role of forage quantity and NVAL in animal response. The data included were obtained from nonrangeland U.S. studies published in refereed journals over the last 48 yr. Two of the studies (Gerrish, 2000; Vanzant, 2010) do not appear in the refereed scientific literature, but they were included to provide data from underrepresented geographical regions and because all of the essential data were available in these reports.…”

Suplementação a pasto: disponibilidade e qualidade x níveis de suplementação x desempenho

“…Conforme Guerrero et al (1984), as quantidades de pasto que os animais deveriam ingerir para máximo ganho ou mesmo para mantença, quando se considera a qualidade da forragem disponível nas pastagens, são muito maiores que aquelas quantidades que os bovinos têm capacidade física de consumir. Este fato indica que o pastejo seletivo é necessário.…”

Avaliação de pastagem diferida de Brachiaria decumbens Stapf. 2. Disponibilidade de forragem e desempenho animal durante a seca

“…Conforme Hofmann (1993), a capacidade de colher e utilizar determinados alimentos na pastagem são características dependentes do tipo morfofisiológico do animal. No entanto, conforme Guerrero et al (1984), as quantidades de pasto que os animais deveriam ingerir para máximo ganho ou mesmo para mantença, quando se considera a qualidade da forragem disponível nas pastagens, são muito maiores que aquelas quantidades que os bovinos têm capacidade física de consumir. Este fato indica que o pastejo seletivo é necessário.…”