Changes in some physical characteristics of the digesta in the reticulo-rumen of cows fed once daily

Abstract

I . Three cows were given 3, 5 or 7 kg hay once daily in a Latin-square design, and samples of digesta from four sites in the rumen and onc site in the reticulum were taken at six times within the 24 h period after the feed. Dry-matter content and distribution of particle size and of particle density were measured for each sample. The changcs in thcse mcasurements with time were studied, The incidence of rumination was also recorded.2. Dry-matter contents of samples ranged from 15 to 3 yo. Valucs for samples from the dorsal sacs of the rumen were considerahly higher than those for samples from the ventral sites; they also changed more with time after feeding and with level of feeding.3. Particlcs were fractionated by sieving into six size groups with mcan dimensions (mm) of 9.3 x 0.8, 4.4 x 0.6, 2.6 x 0 . 3 , 1.6 x o'zj, 0.5 x 0.1 and smaller than 0.5 x 0.1. Coarse particles occurred at highest concentrations in the dorsal sacs of the rumen and responded to effects of time and level of feeding; smaller particles showed less response. 4.. Particle densities ranged from 800 g/l to 1500 gil. The proportions of low-density particles were higher in samples from thc dorsal sacs of the rumen than in samples from ventral sites ; the latter samples had higher proportions of high-density particles than of low-density particles. The changes which occurred are discussed. .The density of coarse particles tended to he low and that of fine particles tcnded to be high.6. Rumination started at the time of maximum Concentration of particles of low density and minimum concentration of particles of high density. Conversely, rumination ended when the concentration of the low-density particles was a minimum and that of thc dense particles a maximum.7. The rcsults are discussed in relation to the possible movement of particles within the reticulo-rumen and the kinetics of particle breakdown.Schalk 8i Amadon (1928) described in some detail the structure of the reticulorumen, made observations on its functioning and referred to some of the physical characteristics of its contents for animals given different types of ration. Since then a number of other workers have added to this basic information (e.g. Magee, 1932;Balch, 1949Balch, , 1958Balch & Kelly, 1950;Nichols, 1959;Campling & Freer, 1962;Welch, 1965;Pearce, 1967;Troelsen & Campbell, 1968).The rate of passage of digesta through the reticulo-rumen and the rate of breakdown of digesta in that organ are important determinants of the efficiency of digestion and of the rate of rumen emptying (Balch, 1950). Both rate of passage and rate of breakdown appear to be markedly influenced by the physical characteristics of the digesta. Knowledge of the factors influencing the physical characteristics will be useful in understanding the effects of practices such as grinding, pelleting and wafering of roughages, the ' protection' of nutrients from digestion in the rumen, the granulation of trace minerals and the capsulation of drugs, medicinal compounds and inert fillers.

Physical characteristics of reticular content in the bovine and consequences on reticular outflow

“…As the particles range in density from 1.03 to 1.18 in inverse proportion to their size, they might be expected to settle out rather than float up: however, these &dquo;functional&dquo; values were measured in density gradient columns (Evans et al, 1973) or using a pycnometer after slow spinning (Hooper and Welch, 1985), and though they take into account gas trapped within the particles they probably do not allow for gas bubbles (1984), the open ROO measures 45 by 10 mm, which justifies the choice of an 18-mm diameter hole here, which gives the same perimeter. However, the volume collected through the 18-mm orifice (20 to 30 ml) is less than half that which flows through the ROO (50-80 ml in the cow according to Bu6no (1975) and Dardillat (1987)).…”

“…The viscosity of the liquid phase was measured because of its importance in the filtration of the content through an orifice; a high viscosity binds the liquid phase to the particles, causing the 2 phases to move at the same rate, thereby curbing occlusion phenomena (Amidon, 1985 (Evans et al, 1973;Baumont et al, 1992) and the sheep (Sutherland, 1988). As the particles range in density from 1.03 to 1.18 in inverse proportion to their size, they might be expected to settle out rather than float up: however, these &dquo;functional&dquo; values were measured in density gradient columns (Evans et al, 1973) or using a pycnometer after slow spinning (Hooper and Welch, 1985), and though they take into account gas trapped within the particles they probably do not allow for gas bubbles (1984), the open ROO measures 45 by 10 mm, which justifies the choice of an 18-mm diameter hole here, which gives the same perimeter.…”

Endoscopic Observations of Digesta Transfer From the Reticulo-Rumen to Omasum of Cattle

“…The reticulo-omasal orifice has often been assumed to regulate particle exit to the rest of the ruminant digestive tract (Welch 1982 However, particles as large as l0 mm are not found in duodenal digesta or feces (Smith et al 1967;Poppi et al 1980). The particulate material, which is presented to the reticulo-omasal orifice, must first be of proper physical characteristics (see Evans et al 1973) to occupy a ventral location in the cranial sac of the rumen. Evans et al 1973).…”

“…The particulate material, which is presented to the reticulo-omasal orifice, must first be of proper physical characteristics (see Evans et al 1973) to occupy a ventral location in the cranial sac of the rumen. Evans et al 1973). These observations may explain why large particles (>6 mm) seldom reach the lower digestive tract (Smith et al 1967;Poppi et al 1980).…”

Características Físicas da Digesta e Resistência de Partículas ao Escape do Rúmen-Retículo em Novilhos Mantidos em Pastagem Natural em Diferentes Estações do Ano

“…A técnica do peneiramento seco, com base na utilizada para solos e fertilizantes, foi padronizada para alimentos moídos e triturados (ASAE, 1969a,b;Ensor et al, 1970). Smith & Waldo (1969) modificaram o procedimento da FDN de Van Soest para fazer uma preparação não destrutiva das partículas de amostra da digesta seca, removendo a interferência do efeito cimentante da proteína, separando os agregados sem uso de força mecânica, eliminando a possível degradação do ta-manho da partícula e aplicando posteriormente a técnica do peneiramento seco.A técnica do peneiramento úmido foi desenvolvida para o fracionamento de amostra da digesta (Evans et al, 1973;Poppi et al, 1980) e o alimento deglutido e coletado no esôfago (Reid et al, 1977). A principal vantagem desta técnica é que a distribuição das partículas da digesta é determinada no estado normal de hidratação, sendo a quebra de partícula durante o peneiramento menos provável (Faichney, 1986).…”