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An experiment was carried out to examine the effect of increasing the proportion of Wimmera ryegrass hay in a lucerne hay-based diet on net transfer of nutrients to the intestine, and on the disappearance ofn-alkanes in the reticulo-rumen and the hindgut of sheep. Following a latin square design, four adult ewes were fed 1:0, 0·33:0·67, 0·67:0·33 and 0:1 proportions of legume and grass. Increasing the proportion of ryegrass in the diet linearly decreased the intake of DM (P= 0·017), organic matter (P= 0·021) and N (P= 0·001). However, neutral-detergent fibre intake was not affected (P= 0·148), nor was its digestibility coefficient (P>0·10). Diet had no effect on duodenal flows of nutrients (P>0·10), although the proportion of N intake (NI) recovered at the duodenum as non-NH3N (NAN) increased linearly withLolium rigidumin the diet (P= 0·002). Full recovery of NI as NAN was achieved at NH3concentrations in the rumen below 110 g/l. Microbial N contribution to NAN varied in a quadratic manner (PP>0·10). Duodenal recovery of consumedn-alkanes was not affected by diet and was complete for those present in higher concentrations in the forages. Isolated rumen bacteria contained significant amounts ofn-alkanes, contributing to the duodenal flow of these hydrocarbons in variable proportions depending on the diet consumed.

1. Studies were done on the effects of giving calves two types of concentrate diet, both in a liquid form from an open pail or in a dry pelleted form, on the closure of oesophageal groove, body-weight gains and the digestibility of rations.2. Twenty-four Holstein calves were used in an experiment by dividing into two groups of twelve calves each. The ‘dry-fed’ group (DFG) was given a pelleted concentrate, F1, from 25 to 42 d of age, and then given another type of pelleted concentrate, F2, from 43 to 87 d of age, and again given F1 from 88 to 112 d of age. The ‘liquid-fed’ group (LFG) was given from a pail a liquid suspension of the equivalent amount of the same concentrates as those fed to DFG calves, for the same periods. F1 contained skim milk and glucose with lower levels of maize and soya-bean meal than F2 which did not contain skim milk or glucose; F1 and F2 were both supplemented with 10 g methionine/kg and also supplemented with lysine at 5 and 10 g/kg respectively. All calves were allowed free access to roughage, and digestibilities were measured at 12 and 16 weeks of age.3. Wet weights of reticulo-rumen and abomasal tissues (% whole stomach weight) were respectively 69.8 and 17.6 in DFG, and 59.0 and 26.4 in LFG at 42 d of age; at 87 d of age, the corresponding values were 68.0 and 16.3 in DFG, and 52.8 and 36.6 in LFG, and further, LFG had significantly more developed caecums and large intestines as well as significantly less developed reticulo-rumens and omasums than DFG.4. Free amino acid patterns in plasma did not vary in DFG, but varied in LFG in response to the change in diet from F1 to F2 and to the difference between diets in lysine supplementation.5. Feeding F1 in a liquid form and F2 in a dry form significantly improved calf gains. The intake of roughage in DFG exceeded that in LFG especially when F2 was fed.6. The digestibility of diethyl ether extracts did not vary with feeding procedures, but that of crude protein (nitrogen × 6.25) was significantly higher in DFG independent of the type of diet. Digestibilities of dry matter and N-free extracts were significantly higher in LFG for F1, while higher in DFG for F2. The digestibility of acid-detergent fibre did not differ significantly between groups at 12 weeks of age, but was significantly higher in LFG at 16 weeks of age, suggesting a possible compensatory contribution of the large intestine to the digestion of fibre in LFG.7. The efficiency of liquid feeding of a concentrate diet to ruminants compared with that of dry feeding is discussed.

1. The rumen urea concentration in gnotobiotic lambs lacking ureolytic bacteria was equal to that of blood.2. Bacterial urease (EC3.5.1.5.) activity in sheep fed by intraruminal and intra-abomasal infusion was inversely related to rumen ammonia concentration.3. A model is proposed for the facilitation and control of urea flux by wall-bound ureolytic bacteria.

1. Blood from chronic indwelling catheters in the caudal aorta and anterior mesenteric, gastrosplenic and hepatic portal veins was used to measure blood flow and net flux of oxygen, glucose and nitrogenous compounds across hepatic portal-drained viscera (PDV), post-stomach (anterior mesenteric-drained viscera (MDV)) and stomach tissues of two beef steers (390 kg mean live weight).2. Steers were fed in sequence on (1) chopped lucerne (Medicago sativa) hay (twelve meals/d), (2) chopped lucerne hay (two meals/d) and (3) a pelleted concentrate diet containing 780 g ground maize/kg (two meals/d). The lucerne hay and concentrate contained 26.5 and 16.8 g nitrogen/kg respectively.3. Five measurements of net flux (blood flow multiplied by venous-arterial concentration differences (VA)) were obtained hourly on 2 d for each dietary regimen, beginning 0.5 h before feeding at 08.00 hours. Blood flow was measured by downstream dilution of p-aminohippurate (PAH).4. Blood flow across MDV averaged 42% of PDV blood flow (665 litres/h).5. Net use of O2 across MDV accounted for 51 % of net PDV use of O2 (920 mmol/h). This disproportionate use of O2 in relation to blood flow was due to greater VA for O2 across MDV than across stomach tissues. Dietary regimen had no effect on the proportions of PDV blood flow and net O2 consumption attributable to MDV or stomach tissues.6. When lucerne was given, net glucose use across MDV represented 69% of PDV use (35 mmol/h). When concentrate was given, MDV glucose use switched to net absorption (29 mmol/h), reducing net PDV glucose use to I mmol/h.7. When concentrate was given, net MDV absorption of α-amino-N (AAN) increased from 98 to 190 mmol/h, yet net PDV absorption (101 mmol/h) was not affected. Net stomach AAN flux increased from -7 to -69 mmol/h when concentrate was given, negating the increase in net MDV absorption.8. Net absorption of ammonia-N across MDV represented 28 and 52% of net PDV absorption when lucerne and concentrate were given respectively. Net NH3-N absorption across PDV was lower when lucerne was given than when concentrate was given (295 v. 154 mmol/h), reflecting lower dietary N intake (153 v. 83 g/d). Net MDV absorption of NH3-N was not affected by diet. Net removal of blood urea-N (BUN) across PDV (101 mmol/h) was not affected by diet. Across MDV, BUN removal was lower when concentrate was given than when lucerne was given (32 v. 77 mmol/h). In beef steers, MDV tissues account for substantial portions of net flux of non-protein-N across PDV and are responsible for essentially all PDV absorption of AAN.

1. Sheep equipped with rumen and abomasal cannulas were given ad lib. access to ground and pelleted lucerne (Medicago sativa) hay except for periods of up to 6 h immediately before experimental sessions in which food intake was measured while various stomach compartments were either distended or subjected to tactile stimulation from a probe. 2. Inserting a probe, consisting of two collapsed balloons tied onto the end of a polyethylene tube, into the reticulum depressed intake by 24% after 30 min of feeding (P less than 0.025). Compensatory feeding was observed during the 30 min period immediately following removal of the probes. There were no effects of having a probe in the abomascum. 3. Distension of the reticulum with 0-800 ml water in a balloon depressed intake by 0.2 g/ml after 30 min of feeding (P less than 0.05). Removing the balloons from the animals allowed them to make up the deficit in intake completely within 30 min. Distending the rumen by 800 ml had no effect on intake (P greater than 0.05). Distending the abomasum with up to 1000 ml water in a balloon depressed intake by 0.11 g/ml after 30 min of feeding with compensatory feeding being significant (P less than 0.05) but incomplete. 4. Combinations of reticular distension up to 800 ml and of abomasal distension up to 1200 ml did not have additive depressing effects on intake.

1. Pangola grass (Digitaria decumbens) grown with and without calcium fertilizer was cut at three stages of regrowth to measure voluntary intake of dry matter (DM) and digestibility of various components of the dried-grass diet by sheep kept in metabolism crates. To determine the extent of a simple Ca deficiency half the sheep on each diet were supplemented with 1·4g Ca/d. Retention times of the various dietary components in the reticulo-rumen were also determined.2. Feeding a Ca supplement had no effect on voluntary intake or digestibility.3. Ca fertilizer increased the Ca content of the grass from 2·2 to 3·8 g/kg DM and DM digestibility from 0·455 to 0·476 (P < 0·01) due to an increase in the digestibility of the hemicellulose.4. Voluntary intake was increased from 38·8 to 43·2 g/kg body-weight0·75 per d by Ca fertilizer due to an 18% reduction in the period of time the DM was retained in the reticulo-rumen.5. Regressions relating voluntary intake to DM digestibility for the Ca-fertilized and control grass were significantly different (P < 0·01). When compared at the same DM digestibility the voluntary intake of the Ca-fertilized grass was 2·6 g/kg body-weight0·75 per d higher than that of the control.6. It was concluded that Ca fertilizer increased both DM digestibility and voluntary intake as a result of changes in the structural composition of the grass and not by a simple increase in the Ca content of the diet.

Effects of sodium hydroxide treatment on intake and digestion of straw organic matter (OM), and microbial protein synthesis were examined in comparison with untreated and treated straws. Intakes (kg dry matter (DM)/d) of untreated, NaOH- and sodium carbonate-treated straws were 5.21, 7.04 and 6.48 respectively and intakes (kg/d) of digestible organic matter (DOM) for the respective diets were 2.57, 3.73 and 2.98 respectively. NaOH-treated straw ranked higher than untreated straw in intakes of DM and DOM (P less than 0.01). The proportion of DOM intake that was apparently digested in the rumen was 0.74, 0.77 and 0.66 on untreated, NaOH- and Na2CO3-treated straws respectively. Although the amount of bacterial N leaving the abomasum was higher with NaOH-treated than with untreated straw (74.6 v. 56.8 g/d, P less than 0.01), efficiencies of bacterial N synthesis were not different between these treatments (28.6 v. 31.5 g bacterial N/kg OM apparently digested, P greater than 0.05). The live-weight gain which the NaOH-treated straw could support was predicted to be 350 g/d and it was concluded that a protein supplement would have provided further increase in production in diets based on NaOH-treated straw.

1. The efficiency of utilization of the dietary energy and nitrogen contained in a dried lucerne (Medicago sativa cv. Chartainvilliers) given either chopped (CL) or ground (1.96 mm screen) and pelleted (PL), was measured in a comparative slaughter experiment. Growing lambs were given equal amounts of digestible energy in the chopped or pelleted form at each at each of the three planes of nutrition for a period of 100 d.2. The initial energy, fat and protein content of both the carcass and the total body of the test lambs was estimated from regression equations between fasted (18 h) live weight and these components, derived from a group of twenty-three comparable lambs. The final energy, fat and protein content of the test lambs was determined directly by chemical analyses.3. The metabolizable energy (ME) content of the diets was derived at each plane of nutrition from measured faecal and urinary losses and estimated methane losses. The depression in ME content with grinding and pelleting the dried lucerne was small (CL 8.69 MJ/kg dry matter (DM), PL 8.42 MJ/kg DM).4. The efficiency of utilization of the ME of the dried lucerne for growth and fattening was higher (P < 0.01) when given in the ground pelleted form (0.533), than in the chopped form (0.284). The net energy value of the PL (3.5 MJ/kg DM) was higher than that of CL (2.2 MJ/kg DM).5. Thus lambs fed on PL grew faster and had a higher caracass weight gain, carcass protein and fat retention than lambs fed on CL. The composition of the carcass was not altered by the physical processing treatment.6. Digestion studies with these same CL and PL diets had shown that grinding and pelleting depressed digestion in the forestomachs and increased digestion in the small intestine compared with the chopped form. The increased efficiency of utilization of the gross energy and ME and the higher net energy value of PL was attributed primarily to a change in the site of digestion within the alimentary tract. Associated with this change was a higher value for absorbed amino acids : absorbed energy and an increased apparent absorption of methionine for lambs fed on PL. The difference in the energy costs of eating and ruminating the CL and PL was small.

1. The relations between food intake, reticulo-ruminal motility and abomasal digesta outflow were investigated in ewes receiving lucerne (Medicago sativa) v. orchard grass (Dactylis glomerata) hay. Abomasal digesta outflow was recorded continuously by means of an electromagnetic flowmeter probe inserted into a duodenal T-shape cannula and the motility using strain-gauge force transducers. Volumes and turnover rates of both rumen and abomasal liquid phases were measured by CrEDTA dilution.2. The voluntary intake of lucerne was higher (60%) than that of orchard grass hay, and paralleled by an increased abomasal outflow (65%) corresponding to an increased number of gushes of digesta through the flowmeter probe: 129/h instead of 78/h on orchard grass hay. Abomasal motor activity was enhanced (35%), and periods of regular spiking activity were seen passing along the duodenum at a higher velocity for the lucerne diet than for the orchard grass diet. The increased abomasal outflow with lucerne hay was associated with a higher reticulo-ruminal turnover rate, but not abomasal turnover rate. Abomasal, but not reticulo-ruminal volume, was increased (30%) when lucerne hay was fedad lib.3. The total number of reticulo-ruminal contractions was increased by 6.6% when the dry matter entering the duodenum was increased by 70.6%, suggesting the level of voluntary intake, rather than reticulo-ruminal motility, as a major factor governing abomasal outflow in sheep.4. More frequent passages of digesta, unrelated to duodenal contractions, were recorded in ewes receiving lucerne compared with orchard grass. Both a higher viscosity of the contents due to the addition of guar gum and the impairment of antroduodenal motility by 5-hydroxytryptophan were able to reduce the flow rate of orchard grass digesta, but did not affect the higher flow rate of lucerne digesta. The findings suggest that the high abomasal outflow in sheep fed on lucernead lib.is related to a low viscosity of the contents that are propelled, even in the case of antral contractions of low magnitude.

1. Effects of feeding liquid milk-substitute to young calves either by nipple-pail or open-bucket on the rumen by-pass and on the rate of passage were studied.2.Sixteen Holstein calves, aged 1 week initially, were used in three experiments in which calves were slaughtered after they were given liquids (milk-substitute and water) containing chromic oxide and SrCl2 6H2O as a tracer either by the nipple- or bucket-feeding method, and the distribution of tracers to the rumen, abomasum and the lower alimentary tracts was examined.3.When the liquid milk-substitute containing tracers was given by the nipple- or bucket-feeding method to calves having been trained to the corresponding procedures for the preceding 1 week, most of the tracers was directed into the omasum and abomasum. There seemed no difference in the functioning of oesophageal groove closure between the two feeding procedures. Even when the liquid milk-substitute containing tracers was given by the nipple-or bucket-feeding method to calves which had been accustomed to different procedures for the preceding week, the majority of tracers were found in the abomasum immediately after administration, though a slightly greater proportion of the tracers entered the reticulo-rumen.4.Continuing bucket feeding of liquid milk-substitute effected an efficient closure of the oesophageal groove at least up to 16 weeks of age. After calves were accustomed to consume liquid milk-substitute from the bucket from 1 to 4 weeks of age, drinking warm water from the bucket also caused efficient closure at least up to 16 weeks of age.When tracers were administered with warm water, Cr2O3 and strontium, especially the latter, transferred much more rapidly to the lower gut than when they were administered with liquid milk-substitute, probably reflecting the curd formation of the milk-substitute in the abomasum. When liquid milk-substitute with tracers was fed by the bucket-feeding method, Sr transferred more rapidly to the lower gut than when the milk-substitute was fed by the nipple-feeding method, indicating that the feeding procedure of liquid milk-substitute has an apparent effect on the rate of passage.

1. Two experiments involving 106 lambs were conducted to study the functioning of the oesophageal groove reflex in lambs sucking from either individual feeders or from a bulk dispenser. The effects on the performance of lambs given either a high-protein or a low-protein creep feed in conjunction with either a ewe's milk substitute, Ewelac, or a homogenate of calcium caseinate, Casilan, were studied. Two milk substitutes, one with a long and one with a short clotting time were compared in terms of their effects on the incidence of diarrhoea.2. The location of the liquid feeds in the stomach was studied radiologically.3. In both experiments the sucking behaviour of the lambs was closely related to thefunctioning of the oesophageal groove reflex and performance of the lambs. In the first experi-ment the milk substitute consistently entered the abomasum in seven of the ten individually fed lambs and in twelve of the twenty-two group-fed lambs. The corresponding figures for the second experiment were twenty-two of the twenty-four individually fed and thirty-four of the fifty group-fed lambs.4. When the milk substitute entered the abomasum it always did so throughout the fattening period even in those instances where the milk had been withheld for 1 month.5. Poor sucking, low milk consumption and the entry of the milk into the rumen resulted in very poor performance by the lambs. Such lambs demonstrated a non-specific unthriftiness similar to the ‘tail enders’ sometimes observed with lambs reared with ewes.6. Continued feeding with either the milk substitute or casein homogenate with a low-protein creep feed did not improve performance.7. The clotting time of the milk substitute did not appear to influence the incidence of diarrhoea among the lambs.

1. Fluids were given by mouth in various ways to young sheep. The extent to which closure of the oesophageal groove operated to direct the fluid to the abomasum was assessed by radiography.2. Salt solutions and milk given as a drench did not produce complete closure of the groove. However, when the animals were accustomed to sucking from a teat before weaning, any liquid suspension and also water, sucked from a bottle, passed entirely to the abomasum even in 12-month-old sheep.3. This technique may be useful when it is desirable to cause protein or other nutrients to by-pass fermentation in the rumen.

1. Gastric motility was studied in a young bull and two sheep which had retained their sucking behaviour. Pressure tracings or electromyograms were recorded from all compart-ments of the stomach.2. During the sucking of milk or water reticulum contractions either became more fre-quent but weak, or ceased altogether. After sucking, or after the introduction of fluid directly into the abomasum, reticulum contractions slowed down but retained their strength. The rumen and omasum were more fully inhibited than the reticulum.3. It is concluded that the inhibitory response to sucking has two phases, a cephalic phase dependent upon the eagerness of sucking which mainly influences the strength of the contractions of the forestomach, and an abomasal phase dependent on the degree of distension of the abomasum which mainly affects the frequency of the contractions.

1. The technique for the quantitative estimation of lignin by digestion with 72% H2S04has been investigated. Two methods of pretreatment designed to eliminate interference products of carbohydrates and proteins were compared, namely (a) acid and pepsin and (b) acid detergent. The latter technique gave low lignin yields owing to the colloidal dispersion of lignin in the acid detergent treatment. Erroneous results arise from an inadequate digestion in 72% H2SO4. It was found preferable to filter the product lignin without prior dilution of the acid since white particles of material, assumed to be cellulose, flocculated from solution on dilution. Also there is some loss due to colloidal dispersion of lignin during refluxing in dilute acid.2. Analysis of soda lignin and sulphuric acid lignin preparations from hay, duodenal contents and faeces of sheep with exteriorized flow through a re-entrant duodenal fistula provided evidence for the degradation of lignin by digestive processes. Demethoxylation of lignin occurred mainly in the stomach, suggesting that this was the main site of breakdown.3. A new displacement method of measuring duodenal flow is described. Quantitative results obtained also indicate that lignin is degraded mainly in the stomach to the extent of about 10%.4. These results suggest that faecal lignin is an adequate marker for the estimation of duodenal flow, and hence of the extent of changes in the stomach and intestines respectively.