Effects of feeding frequency and level of feed intake on chemical composition of rumen bacteria

Abstract

Cell mass (dry matter per cell) and cell composition (concentrations of DNA, RNA, phospholipids, total N, a-dextran, diaminopimelic acid and 18 common amino acids) of rumen bacteria were measured at various times after feeding sheep chaffed lucerne hay (Medicago sativaX,.) once daily. Cell composition was measured with sheep fed once hourly. Total' DNA and RNA pool sizes in the rumen were also measured.While cell composition was not affected by level of feed intake (700 g v. 1050 g dry matter/day), total DNA, RNA and D.M. pool sizes in the rumen increased with increasing feed intake. With sheep on the once daily feeding regimen relative rumen pool sizes in rumen digesta at various times after feeding were: RNA, 4 > 14 > 0 h; DNA, 4 and 14 > 0 h; D.M. 4 > 14 > 0 h. With the hourly feeding regimen pool sizes were similar to the averaged daily values for sheep fed once daily.When sheep were fed once daily bacterial cell mass, DNA and phospholipid concentrations peaked at 12-14 h after feeding and subsequently decreased to the 0 h value. RNA concentration was maximal at about 4 h after feeding and declined to near the 0 h value at about 14 h. RNA concentrations in bacteria were highly correlated with gas production rates by whole rumen digesta. The ratio RNA:DNA was highest shortly after feeding, decreased to below the 0 h value at about 14 h and then increased to the Oh value. The relative concentrations of a-dextran in bacteria were: 4 > 14 > 0 h. Cell composition witli sheep fed hourly tended to reflect the averaged daily values for sheep fed once daily.These results are discussed with regard to changes in estimated fermentation rate and pool size of bacteria in the rumen. It is suggested that changes in average composition (DNA, RNA, total N and RNA: DNA ratio) of mixed rumen bacteria reflect changes in the average growth rate of the population.

Estimation of microbial protein supply in ruminant animals based on renal and mammary purine metabolite excretion. A review

“…Assumptions of a constant purine:N in rumen bacteria are also subject to criticism, since the RNA:N ratio of liquid associated bacteria (LAB) varies according to growth conditions in the rumen (Bergen et al, 1982;Bates and Bergen, 1984), feed intake (John, 1984), diet (Bates et al, 1985) and the techniques used to isolate rumen bacteria (Merry and McAllan, 1983). Furthermore, ratios of RNA: DNA (John, 1984) and RNA:N (Susmel et al, 1993a) in LAB have been shown to vary diurnally.…”

“…Furthermore, ratios of RNA: DNA (John, 1984) and RNA:N (Susmel et al, 1993a) in LAB have been shown to vary diurnally. Craig et al (1987b) also reported significant changes in the ratio of purine :N ratios in LAB and solid associated bacteria (SAB) during the feeding cycle of dairy cows, with the lowest ratios occuring immediately post-feeding.…”

Estimation of microbial protein flow from the rumen of sheep using microbial nucleic acid and urinary excretion of purine derivatives

“…Flows of microbial N to the duodenum were calculated using the total-N:purine-N ratio of microorganisms (Zinn and Owens 1986). It was assumed that composition of the diet did not affect the total-N:purine-N ratio of rumen microorganisms (John 1984;Smith et al 1968). …”

Fermentação ruminal e eficiência microbiana em bezerros holandeses alimentados com dietas contendo diferentes níveis de concentrado

“…Entre os fatores responsáveis pela variação na composição dos microrganismos ruminais, incluemse o tipo de microbiota e sua fase de crescimento, a disponibilidade de nutrientes, as alterações na dieta e a variação na freqüência de alimentações (JOHN, 1984;National Research Council -NRC, 1985).…”

“…Os dados sobre o conteúdo em RNA das bactérias mostram variação bastante acentuada, de 3,5 e 5,0 g/100 g MS para bactérias aderentes e livres, respectivamente (MERRY e McALLAN, 1983) até 12 g/100 g MS (JOHN, 1984). Esta variação em parte é atribuída aos diferentes métodos de análise utilizados, mas, por outro lado, reflete também o nível de atividades metabólicas das bactérias (BATES et al, 1985).…”