1. Sheep were used to evaluate the nutritional consequences of a low condensed-tannin concentration (22 g/kg dry matter (DM)) in lotus (Lotus corniculatus L.) (control group) compared with lotus given to sheep receiving intraruminal polyethylene glycol (PEG) infusion (PEG group). PEG selectively binds to tannins and prevents tannins from binding proteins.2. DM intakes (1430 (SE 28) g/d) and digestibility of energy (663 (SE 4.5) kJ/MJ intake) were similar for both groups but the apparent digestion of nitrogen was lower in the control sheep (0.70) than in the PEG sheep (0.78; P < 0.001).3. The proportion of N apparently digested before the abomasum (i.e. in the rumen) was lower (P < 0.05) in control sheep (0.12) than in PEG sheep (0.21 ; P < 0.05). Rumen ammonia concentrations were lower ( P < 0.001) in control sheep than in PEG sheep. The proportion of neutral-detergent fibre (NDF) digested in the rumen was similar for both groups (0.48 (SE 0.012)) but less energy was digested in the rumen of the control (0.42) than of the PEG sheep (0.47; P < 0.05).4. The flux of essential amino acids (EAA) through the abomasum of control sheep was 50% greater than that in PEG sheep; flux of non-essential amino acids (NEAA) was 14% higher in control than in PEG sheep. Apparent digestibility of EAA in the small intestine was similar for both treatments (0.67), but NEAA were less well digested in the control (0.55) than in the PEG sheep (0.69).5. The presence of tannins in the control group increased net apparent absorption of threonine (57%), valine (89%), isoleucine (94%), leucine (30%), tyrosine (41 %), phenylalanine (93% ), histidine (90%) and lysine (59%), and reduced NEAA absorption by lo%, compared with PEG sheep.

No abstract

Chaffed lucerne hay of 64 % apparent organic matter (OM) digestibility was fed to wether sheep under four feeding regimens: two levels of dry matter (D.M.) intake (700 (L) and 1050 (H) g/day) and within each level two feeding frequencies (once a day (daily) and once an hour (hourly)). Three separate groups of sheep were used concurrently: a slaughter group was used to obtain feeding behaviour data and to measure pool sizes and obtain samples from the reticulo-rumen; a digestion group, in which each sheep was prepared with a rumen and a duodenal cannula, was used to measure duodenal digesta flow, rumen microbial growth and reticulo-rumen motility; a balance group was used to measure digestibility and nutrient balances.High D.M. intake increased reticulo-rumen pool sizes and flow rates but it did not affect apparent digestibilities or the proportions of OM, fibre, cellulose, hemicellulose, lipid and nitrogen digested in the stomach and intestines. Increased feeding frequency had a major effect on reticulo-rumen pool sizes but did not affect apparent digestibilities or partition of digestion of non-nitrogenous constituents. Daily feeding resulted in increased total-N flow to the duodenum; however, N retention was significantly greater with frequent feeding. It is suggested that this was due to a more efficient tissue utilization of N.The kinetics of digesta flow within the reticulo-rumen, expressed as fractional flow rates, were studied with data from sheep fed hourly. The fractional inflow, outflow and disappearance rates for OM, fibre, cellulose and hemicellulose did not change with an increase in intake because of an equivalent increase in reticulo-rumen volume. Increasing D.M. intake by 50 % resulted in a 24 % increase in water intake, a 19 % increase in reticulo-rumen water volume, and a 49 % increase in water outflow rate. The data suggest that the increased outflow of water was achieved by increasing the net flow of water across the mucosa into the reticulo-rumen, rather than by increasing salivation.There was no difference between treatments in the frequency of reticulo-rumen contractions. It was calculated that for each A sequence contraction, OM flow was 0-26 and 0-37 g and water flow was 4-38 and 0-36 g on L and H intakes respectively. A 50 % increase in intake resulted in a 42 % increase in OM passage per A sequence contraction. This increased passage with intake was not accompanied by an increase in reticulorumen contraction frequency.TMTTJODTTPTTOIST Waldo, Smith & Cox, 1972; Baldwin, Koong & w Ulyatt, 1977;Mertens & Ely, 1979; Black et al. A large amount of information is available con-1981), has identified areas of research which are cerning digestion and metabolism within the reti-likely to yield useful information on the control culo-rumen. Far less is known about the processes processes. These include: the effects of chewing that control breakdown of food residues and their during eating and rumination on particle size repassage out of the reticulo-rumen. The use of duction and fermentation, t...

No abstract

S U M M A R YFour swamp buffaloes (Bubalus bubalis) and four crossbred Bos indicus x B. taurus cattle, fistulated at the rumen and abomasum or duodenum, were offered rice straw with mineral supplements in two experiments. In Expt 1, the straw was supplemented with 5% of leaf of Leucaena leucocephala, and in Expt 2 with either urea or urea with sunflower meal and rice grain. Intake of supplements of urea or urea/sunflower/rice respectively was 935 and 681 g/kg offered in buffaloes and 566 and 789 in cattle.Buffaloes ruminated longer than cattle (Expt 1, 635 v. 452 min/day; Expt 2, 626 v. 466 min/day, P < 001). In Expt 1, voluntary intake and frequency of ' A ' sequence forestomach contractions of both species was not affected by species, but buffaloes had a greater (P < 005) contraction force in the rumen and omasum, lower rate o f ' B ' sequence rumen contractions, and faster (P < 0001) rate of gastrointestinal passage than cattle. In Expt 2, voluntary intake of both species was similar, and addition of concentrates did not affect voluntary roughage consumption, nor in situ rate of digestion of rice straw. Rate and predicted extent of digestion of dietary materials did not differ between species in Expt 1, despite lower concentrations of ammonia in rumen fluid in cattle than buffaloes; however in Expt 2, the rate of digestion of rice straw was higher (/> < 005) and predicted extent of digestion was 14-20% (P < 005) lower in buffaloes. Digestibility of cell wall constituents was lower (P < 005) in buffaloes than in cattle in both experiments, but in Expt 2, provision of concentrates reduced (P < 001) the proportion of digestible cell wall constituents digested in the forestomach of buffaloes, but not of cattle. Plasma urea concentrations were higher (P < 0-05) and transfer of urea to the rumen tended to be higher (7-4 v. 3-7gN/day; P<0-l0) in buffaloes. Faster fractional outflow rates of microbes and of small digesta particles from the rumen were observed in buffaloes in Expt 1.In Expt 1, more microbial N left the abomasum (35 v. 30 g per kg organic matter apparently digested in the forestomach; P < 005) of buffaloes than cattle, and in Expt 2 more non-ammonia N (43 v. 31 g per kg organic matter apparently digested in the forestomach) flowed into the intestines of buffaloes. In Expt 1 microbial retention time was shorter (26 v. 47 h; P < 001) in the rumen of buffaloes.Patterns of appearance of plastic particles with time after dosing indicated faster escape from the rumen of buffaloes of non-chewed particles, and a greater proportion of particles subjected to ruminative chewing, than in cattle. Ruminative chewing of plastic particles in buffaloes was progressively more efficient than in cattle with increasing particle length and decreasing specific gravity. Analysis of faecal particle distribution indicated buffaloes tended to excrete smaller particles than cattle.The adaptive significance of faster digesta passage in the buffaloes appeared to derive from a more balanced supply of absorbed protein relative to dige...