Sward Height and Vertical Morphological Differentiation Determine Cattle Bite Dimensions

Abstract

To identify and quantify the influence of sward structure on the intake of grazing animals requires an understanding of sward-animal interactions at the bite level. We tested the hypothesis that bite dimensions on vertically heterogeneous swards are determined by structural characteristics of the top leaf stratum, independent of those of a bottom layer of pseudostem or stem. Dallisgrass (Paspalum dilalatum Poir.) microswards were constructed by hand in a factorial combination of two lamina lengths (5 and 8 em) and two sward heights (8 and 16 em). Tillers consisted of a top segment of lamina and a bottom one of pseudostem (Exp. l) or stem (Exp. 2) of length equal to the difference between sward height and lamina length. Treatments were replicated over three steers (Bos taurus) of 750 kg avg. body weight. Bite area and depth increased with sward height in swards with pseudostem but were not affected by lamina length. Pseudostems were not a barrier to defoliation and did not affect bite dimensions. Steers restricted grazing of tillers with stem to the upper lamina horizon. Bite depth was limited by stems only when lamina length was less than half of sward height. Bite area was reduced by the presence of stems because tillers bent at ligule height, restricting the animals to gather fewer tillers in each bite than when tillers bent at the base. Bite weight was reduced severely in swards with stem, relative to those with pseudostem. Results confirmed the importance of stem horizons and their relative positions in the sward as determinants of bite weight. P ROGRESS IN UNDERSTANDING the sward structural determinants of instantaneous (dry matter) OM intake rate (IIR) by grazing animals requires better knowledge of sward-animal interactions at the individual bite level. Within a limited range of sward conditions, grazing animals can adjust for sward-induced reductions in bite OM weight by increasing biting rate and/or daily grazing time (Chacon and Stobbs, 1976;Hodgson, 1985;Penning et al., 1991). Beyond these E.R: Flort:s, Universidad Nacional Agraria,

Comportamento ingestivo de novilhas de corte submetidas a estratégias de suplementação em pastagens de aveia e azevém

“…Assim, o aumento na dieta do nível de suplemento (12, 24 e 36%), juntamente com as variações ocorridas na estrutura e composição do pasto (Tabela 1), pode ter proporcionado maior ingestão de lâminas foliares pelos animais. Na média dos períodos, observou-se maior MBOC no início do período de pastejo (P<0,05), provavelmente em virtude da composição botânica (Arnold & Dudzinsky, 1967), com predomínio de aveia, e da maior altura do pasto e largura da lâmina (Flores et al, 1993) (Tabela 1), proporcionando também menor taxa de bocados (Tabela 2).…”

Morphogenetic characteristics and management of Tanzania grass

“…Besides that, stem length increased as grazing intervals increased (except during July/August when no grazing interval effect was observed) and, for all grazing intervals, the highest stem length was observed in April/May, during the reproductive phase (Table 2). For temperate grasses, it has been observed that stem length limits bite depth (Barthram & Grant, 1984;Flores et al, 1993). For tropical grasses, there is almost no information about the influence of stems on animal grazing behaviour.…”

“…For tropical bunch-type grasses, stems may represent more than 50% of herbage production (Andrade, 1987). In this case, it is important to evaluate stem growth rate because it interferes with animal intake and grazing behaviour (Flores et al, 1993).…”

COMPORTAMENTO DA INGESTÃO EM BOVINOS (RUMINANTES) EM PASTAGEM DE CAPIM Brachiaria decumbens NA REGIÃO CENTRO-OESTE DO BRASIL

“…Pastejo é o processo através do qual os animais utilizam seus sentidos, cabeça e pernas para locar bocados potenciais e seu aparato bucal para levar a forragem à boca, prendê-la entre os dentes, cortá-la com o movimento da cabeça, caracterizando um bocado, para então, mastigá-la, formando o bolo alimentar e então, degluti-la (EDWARDS et al 1995;FLORES et al 1993).…”