Volatile fatty acid production in the rumen of cattle given an all-concentrate diet

Abstract

I . Short-term in vitro incubations of whole rumen contents have-been used to measure the rate of production of volatile fatty acids (VFA) in two heifers given a diet containing 85 yo barley and 15 yo protein-mineral-vitamin supplement. Daily intake of the diet was restricted to 5.1 kg which was given in three equal feeds. In one heifer (no. 794), VFA production was measured over a 24 h feeding cycle; in the other (no. 832), a single 6 h feeding period was examined.2. The feeding schedule outlined above was found in previous work to result in a major alteration in the rumen environment and in the end-products of rumen fermentation relative to findings in animals given the same diet ad lib. Some of these earlier observations have been confirmed and extended in the present work.3. In heifer 794, the rate of VFA production reached a maximum (52-62 m-moles/l. h) I 5 minafter each feed and then declined steadily throughout the remainder of the feeding period. Consistent changes with time were observed in rumen pH and in the concentration of VFA and dry matter in rumen contents during each feeding period.4. Simultaneous measurements of rumen fluid volume and outflow allowed estimates to be made of VFA production and absorption in the entire rumen during each feeding period.In heifer 794, total VFA production amounted to 18.2 moles/day of which approximately 85 yo was absorbed directly from the reticulo-rumen. On a caloric basis, total daily production accounted for 36. j % of the digestible energy intake. j . In heifer 832 there were significant differences in the rate of VFA production and in rumen pH and VFA concentration between two sets of observations made some 8 weeks apart. These differences appeared to be related to changes in the rumen microbial population and in particular to a marked alteration in the numbers of ciliate protozoa. The possible role of rumen ciliates in modifying both the rate of VFA production and the environment within the rumen is discussed.

Ruminal pH and temperature, papilla characteristics, and animal performance of fattening calves fed concentrate or maize silage-based diets

“…The pH values tend to peak in the moments before feed intake, begin to fall afterward, and reach the minimum between 3 and 6 h after feed intake depending on the ration (Duffield et al, 2004;Marden et al, 2005;Palmonari et al, 2010). As acid production decreases, volatile fatty acid absorption and rumen buffer capacity (mainly from saliva) increase, and pH begins to recover initial values; this process is estimated to last approximately 18 h (Whitelaw et al, 1970;Maekawa et al, 2002;Palmonari et al, 2010). The pH pattern observed in TMR animals suggests that most of the feed is consumed as soon as it is delivered.…”

Influence des ciliés du rumen sur la digestion de différents glucides chez le mouton. I. — Utilisation des glucides pariétaux (cellulose et hémicelluloses) et de l'amidon

“…Si l'on admet que la lignine est pratiquement indigestible (Journet et Jarrige, 1962) (Hungate, 1943 ;Sugden, 1953 ; Kanegasaki, 1969 ;Bonhomme et Durand, 1974 ;Jouany et al, 1977 ;Grolière et al, 1980 ;Sènaud et al, 1980) cide avec plusieurs observations déjà faites dans notre laboratoire (Collombier, 1981) ou à l'étranger (Whitelaw et al, 1970 Gill, 1971 ;Itabashi et Kandatsu, 1975) s'explique à la fois par une dégradation des protéines alimentaires (Warner, 1955 ;Williams et al, 1961) et bactériennes (Gutierrez et Hungate, 1957 ;Gutierrez, 1958 ;Coleman, 1975) ingé-rées par les ciliés.…”

Diurnal Changes of Volatile Fatty Acid Concentration in the Rumen of Sheep Fed in Free Access

“…HUNGATE15) suggested that rumen can be regarded as a complete continuous fermentation system in the case where the volume of rumen, the rate of salivary secretion and the rate of passage of digesta through the rumen are stable all day long and that if an animal has been fed by subdividing the daily ration into portions which were fed at regular and frequent intervals over a day, its rumen would resemble the continuous fermentation model FAICHNEY6) reported that the range from minimum to maximum values observed during a day for the rumen VFA concentration of the sheep fed lucern pellet decreased from 4 .5-16.5mmol/ dl to 8.0-11.0mmol/dl corresponding to an increase in the frequency of feeding from once to eight times daily. WHITELAW et al 8) similarly described that increasing the frequency of feeding of a barley diet to heifers from once to three times daily decreased the range of rumen VFA in a day from 6.5-15.5mmol/dl to 6.0-11.0mmol/dl. The present study showed that the ranges of the rumen VFA in the sheep fed the hay or concentrate diet in free access were the same as those observed when increasing the frequency of feeding.…”