Influence of pasture sward height and concentrate supplementation on intake, digestibility, and grazing time of lactating beef cows.

Abstract

To establish the effect of sward height (SH) and concentrate supplementation on performance of grazing cattle, 24 crossbred Angus beef cows (535 kg BW) and calves (114 kg BW) were grouped by weight and calving date. They were randomly assigned to two SH treatments, either 4 to 8 cm or 8 to 11 cm, and fed three levels of supplement, high, low, or none, consisting of 6.24, 3.12, and 0 kg x animal(-1) x d(-1), respectively. The experiment was repeated over three 15-d periods in 1996: May (P1), June/July (P2), and August (P3). No SH x supplement level x period or SH x supplement level interactions (P > 0.10) were evident for responses tested. Cows on lower SH had greater (P < 0.08) DMI but spent an additional 1.3 h/d (P < 0.01) grazing compared with cows on higher SH. Sward height had no influence (P > 0.10) on forage DM digestibility (DMD). Forage DMI, DMD, and grazing time (GT) decreased (P < 0.05) as supplementation increased. Nonetheless, supplemented cows consumed more total DMI (P < 0.08) than unsupplemented cows. Cows consumed 2.4 kg/d more forage DM (P < 0.01) in P1 and P2 than in P3. Cows grazed 1.3 h/d (P < 0.01) less in P1 than in P2 and P3. Grazing efficiency (DMI/h GT) declined as supplementation increased and grazing season advanced to P3 (P < 0.01). Decreased forage DMI and grazing efficiency with increasing supplementation suggests that supplemented cattle should be able to maintain productivity while grazing at SH lower than unsupplemented cattle.

Comportamento ingestivo de novilhos sob suplementação em pastagens de capim-tanzânia sob diferentes intensidades de desfolhação

“…Esse resultado indica que a estrutura do dossel ou o resíduo nos últimos dias de pastejo dificultou a colheita de forragem pelos animais, o que está de acordo com a afirmativa de Hodgson (1990), que relatou efeito da estrutura e da composição botânica da pastagem sobre a ingestão de forragem por animais em pastejo. Contudo, Gekara et al (2001) observaram aumento no tempo de pastejo em resposta à redução na altura do dossel e, conseqüentemente, à menor quantidade de massa seca de forragem no pré-pastejo.…”

Corn distillers dried grains with solubles supplementation in a pasture-based beef production system

“…This increase in total DMI has been observed for cattle that are either grazing or fed high forage diets and supplemented with concentrate or fiber-based supplements Bodine et al, 2001;Sanson and Clanton 1989;Matejovsky and Sanson, 1995;Gekara et al, 2001;Goetsch et al, 1991). Most feeds have substitution rates that are less than one and greater than zero Bodine et al, 2001;Sanson and Clanton 1989;Matejovsky and Sanson, 1995;Gekara et al, 2001;and Goetsch et al, 1991) which results in a net increase in total DMI and increased animal productivity. observed that dairy cows grazing at high and low pasture allowances had increased total DMI as concentrate was supplemented at 8.63 kg/d.…”

“…Bodine et al (2001) found that steers supplemented with protein increased total OM intake and improved BW gain. In spite of substitution, total DMI is quite often increased, even with cattle at different stages of production and consuming forages of different quality as indicated by reported substitution rates less than one Bodine et al 2001;Sanson and Clanton 1989;Gekara et al 2001;and Goetsch et al 1991). Only in certain situations, such as supplementation of low quality forage with high protein supplement, can an increase in forage intake be observed as well.…”

“…Overall, the effects of substitution on forage intake by concentrate supplementation may be caused by negative associative effects such as lower rumen pH, lower rate of forage digestion, lower NDF digestibility, and decreased grazing time Gekara et al, 2001). Royes et al (2001) observed decreasing apparent digestibility of ADF and NDF of stargrass hay supplemented with increasing levels of corn.…”

“…Bodine et al (2001) observed an increase in total DMI in steers supplemented with cottonseed hulls, pelleted protein, high fiber, or high grain supplements while grazing bermudagrass. Sanson and Clanton (1989), Matejovsky and Sanson (1995), and Gekara et al (2001) fed corn to cattle, sheep, and calves, respectively, with low to high quality grass forages and also found that total DMI was increased with supplementation.…”