The voluntary intake of hay by sheep in relation to its degradability in the rumen as measured in nylon bags

Abstract

The voluntary intake and digestibility of four hays were measured with eight sheep using two 4 × 4 Latin squares. Measurements were made during the last 8 days of each 3-week period. The degradation characteristics of the hays were measured by incubating samples (in nylon bags) for 12, 24, 48 or 72 h in the rumen of four sheep fitted with rumen cannulae and given a good hay. The exponential p = a + b(1 − e−α) where p = degradation loss, t = time, and a, b and c are constants, was fitted. The potential degradability (defined as a + b) of the dry matter (DM) of the four hays was 0·76, 0·66, 0·54 and 0·46 with corresponding voluntary intakes of 71, 62, 52 and 45 ± 2·9 g DM per kg M075 per day. The in vivo digestibilities were 0·61, 0·59, 0·46 and 0·45 (s.e. 0·013) respectively and corresponded to 23-, 25-, 31- and 67-h degradation. Voluntary intake was better related to potential degradability (and degradability at 12, 24, 48 and 72 h) than to in vivo digestibility. It is concluded that the degradation characteristics of forages may have useful application in predicting voluntary intakes, and that potential degradability could be used to define the rumen (jegradable nitrogen content necessary with any particular forage.

Morphological fractions, chemical composition and in vitro fermentation characteristics of maize stover of five genotypes

“…The potential gas production and IVOMD represented the degradable feed component; therefore, higher values of potential gas production and IVOMD for husk implied that it was more digestible than the other fractions (Hovell et al, 1986). Similarly, waxy maize stover had higher values of a 1 b and IVOMD than conventional, fodder and high-oil genotypes, indicating that it had higher digestibility than the other maize stovers mentioned above.…”

Use of the in Situ Technique and Passage Rate Constants in Predicting Voluntary Intake and Apparent Digestibility of Forages by Steers

“…(1919), however reported an increase in rumen liquid turnover rate from 0.034 at maintenance level of intake to 0.053 at two times maintenance level of intake. Also, Grovum and Williams (1911) of Hovell et al (1986) andOrskov et al (1988). similar conclusions can be drawn.…”

“…Hovell et al (1986) also reported that degradation of DM during short periods of nylon bag incubation were better correlated with voluntary intake than with in vivo digestibility. Orskov et al (1988), using nylon bags to predict the voluntary intake of straw by cattle from dry CANADIAN JOURNAL OF ANIMAL SCIENCE et de la consommation (R'z : 0,86) …”

Predição do Consumo Voluntário do Capim-Tanzânia (Panicum maximum, J. cv. tanzânia), sob Pastejo, por Vacas em Lactação, a partir das Características de Degradação

“…O coeficiente de variação obtido para os valores estimados do consumo em kg MS/dia (26,7%) (Tabela 3) foi inferior aos obtidos HOVELL et al (1986), em que estes autores observaram que as informações dos sacos de náilon explicam 98% da variação na ingestão, e que 35, 75 e 94% de variabilidade foram explicadas pelos teores de PB, FDN e FDA do alimento, respectivamente. Dessa forma, o valor de FDN encontrado para a extrusa foi bastante alto (78,8%) (Tabela 1) e pode ter limitado o consumo de matéria seca, pois segundo VAN SOEST (1994), valores acima de 55 a 60% de FDN na matéria seca limitam o consumo de forragem.…”

“…O uso da técnica in situ para avaliar alimentos tem se tornado um método alternativo devido a sua simplicidade e natureza direta, além de tornar possí-vel a determinação das taxas de degradação (HOVELL, 1986). O AFRC (1993) vem adotando a técnica in situ como o método padrão para caracterizar a degradabilidade ruminal do nitrogênio e por apresentar resultados semelhantes àqueles obtidos pela técnica in vivo.…”