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The aim of the present study was to evaluate the effect of replacing corn grain with citrus pulp (CSP) in the starter concentrate on performance and metabolism of dairy calves. Twenty-four individually housed Holstein calves were blocked according to birth date and weight and fed one of the following concentrates: (1) concentrate containing 64% corn and 0% CSP (0CSP); (2) concentrate containing 32% corn and 32% CSP (32CSP); and (3) concentrate containing 0% corn and 64% CSP (64CSP). Animals were fed 4 L of milk replacer daily (20% crude protein, 16% ether extract) divided in two meals (at 0700 hours and 1800 hours). The starter feed and water were provided ad libitum. Starter intake and faecal score were monitored daily. Bodyweight and measurements (withers height, hip width and heart girth) were recorded weekly. Blood samples were collected weekly, and ruminal fluid samples at 4, 6 and 8 weeks of age, 2 h after the morning feeding. After 8 weeks, animals were harvested to evaluate the development of the proximal digestive tract. Concentrate composition had no effect (P > 0.05) on concentrate intake, weight gain, bodyweight, body measurements, and faecal score. However, there was a lower concentration of ruminal butyrate (P < 0.05) in animals receiving 0CSP than in those fed the starter containing CSP. The 0CSP concentrate resulted in a lower (P < 0.05) total weight of the proximal digestive tract, weight of the reticulum–rumen and weight of the omasum than did the other concentrates. The length of the rumen papillae was the greatest (P < 0.05) in 32CSP-fed animals. However, papillae area in animals fed 32CSP concentrate was larger (P < 0.05) than that in 0CSP- and 64CSP-fed animals, with no difference observed between these latter two treatments. However, 0CSP-fed animals showed a higher proportion of abomasum than did the animals fed 32CSP and 64CSP concentrates. The replacement of 50% or 100% of corn by CSP in the starter feed of dairy calves did not affect performance and probably contributed to the better development of the proximal digestive tract.

The objective of this study was to characterise the regional variation in the barrier function of the gastrointestinal tract in Holstein calves using the flux rates of mannitol and inulin as permeability markers and tissue conductance (Gt) as an electrophysiological indicator of barrier function. Six Holstein steer calves (6 months of age) fed a common diet were used. Calves were killed by captive bolt stunning and pithing, and tissues were collected from the rumen, omasum, duodenum, jejunum, ileum, caecum, proximal colon, and distal colon. Tissues were carefully washed using a pre-heated (38.5°C) buffer solution (pH 7.4) saturated with oxygen and then transported to the laboratory. The mucosa was prepared by hand stripping and mounted between two halves of an Ussing chamber (n = 3/region with an exposed surface area of 3.14 cm2 for rumen and omasum and 1 cm2 for all other tissues). All tissues were incubated under short-circuit conditions and exposed to a similar buffer solution except for the energy source; rumen, omasum, caecum, and colon tissues were incubated with buffer containing short-chain fatty acids while tissues from the small intestine were bathed in buffer containing glucose. The Gt and the serosal-to-mucosal flux rates of 14C-inulin and 3H-mannitol were measured as indicators of barrier function. The serosal-to-mucosal flux rate of mannitol was greatest (P < 0.001) in the jejunum [104.8 nmol/(cm2 × h)] and least in the rumen and omasum [20.3 and 18.6 nmol/(cm2 × h), respectively]. In contrast, the serosal-to-mucosal flux rate of inulin was greatest (P < 0.001) in the omasum [158.6 nmol/(cm2 × h)] followed by the rumen [87.3 nmol/(cm2 × h)] with no differences among the other regions [18.7 – 62.0 nmol/(cm2 × h)]. The Gt was greatest (P < 0.001) in the jejunum (34.6 mS/cm2) and least for the rumen (3.67 mS/cm2) and omasum (3.23 mS/cm2). The Gt was correlated with both inulin and mannitol flux rates in duodenum, caecum and proximal colon (P < 0.05); whereas, no such correlations existed in jejunum, ileum and distal colon. The Gt was correlated with the mannitol flux rate but not the inulin flux rate in rumen and omasum. For all regions but the rumen and omasum there was a positive correlation between mannitol and inulin flux rates. These data indicate that the translocation of a large molecule (inulin) across the omasum and rumen is greatest despite having an apparently tight epithelium based on Gt and mannitol flux rate, while the jejunum appears to have greatest potential for paracellular permeability.

Feed intake and digestion studies were conducted with sheep offered a medium quality roughage and given various concentrate supplements. The provision of supplements in amounts equal to c. 23% of voluntary roughage consumption always decreased roughage intake. The decrease with wheat-based supplements was little affected by supplement feeding frequency, by use of ground grain rather than whole grain or by the provision of additional essential nutrients, but its magnitude was reduced by c. 30% with use of buffer salts to prevent decline in rumen digesta pH. The supplements were associated with less digesta in the alimentary tract and less rumination. Supplements increased the rate of liquor outflow from the reticulum and the rate of marker clearance from the reticula-rumen. The rumen digesta and reticulum digesta differed with respect to particle size distribution and only some 30% of the organic matter in reticulum digesta was in particles too large to pass to the omasum. The data were considered to be consistent with a concept that the regulation of roughage intake involves an interplay between the animal's energy metabolism and the quantity of digesta in the reticula-rumen and to indicate (i) some discrimination against the larger particles in digesta flow from the rumen to the reticulum, (ii) appreciable discrimination on the basis of size of particle in digesta flow from the reticulum to the omasum, and (iii) regardless of state of subdivision, constraints applied to digesta passage to the omasum which could have affected the level of feed intake achieved.

Infusion into the abomasum of sheep of a mixture of volatile fatty acids partially neutralized with sodium hydroxide (VFA salts) markedly increased the rates of flow of liquor and chloride from the abomasum to the small intestine; buffered mineral salts comprising sodium bicarbonate, sodium citrate and either disodium or dipotassium orthophosphate consistently produced a similar but smaller response. Thcre was little or no effect of the infusions on rumen or omasal outflow. By contrast, infusion of VFA in acid form had no effect on abomasal liquor and chloride flow and the infusion of sodium chloride did not effect liquor flow. The pH of abomasal digesta either decreased slightly or was unchanged when VFA salts wcre infused, but increased with infusion of mineral buffer salts. It is concluded that gastric secretion is markedly affected by the buffering capacity of the digesta entering the abomasum. The VFA entering the abomasum in digesta were estimated to be responsible for the secretion of as much as 60% of the chloride secreted into the organ. High rates of abomasal secretion, induced by intra-abomasal infusion of VFA salts, increased both (i) the amount of digesta in the abomasum and small intestine, (ii) the extent of absorption of calcium and magnesium distal to the omasum, and (iii) absorption from the small intestine of water, chloride and VFA, while decreasing (i) the pH of digesta in some sections of the small intestine and (ii) marker residence time in the proximal half of the small intestine. The rates of flow of both liquor and chloride from the abomasum, together with pH of abomasal digesta, progressively increased with age in animals aged 6, 10 and 30 months; they were still larger in other animals aged 54 months. By contrast, no consistent trends with age were observed with VFA and chloride concentrations in rumen liquor or the flow of metabolites from the rumen. The flow changes are suggested to be the result of changes in gastric juice secretion with age, stimulated at least in part by a corresponding decrease in the rate of absorption of buffering substances in the omasum and/or abomasum.

A study was made of the non-carcass components of 16 crossbred wethers (progeny of Dorset Horn rams and Border Leicester x Merino ewes) maintained at 30 kg liveweight for either 0,25, 50 or 75 days. Animals were individually penned and fed a pelleted ration of 80% lucerne chaff and 20% cereal grain (89.3% dry matter, 14.8% crude protein and 18.27 kJ/g gross energy). The weight of hooves increased significantly (P < 0.05) during weight stasis, while the weight of the liver decreased significantly (P < 0.001) as did the weight of the kidneys (P < 0.01). Neither head, skin, heart, lungs, spleen, pancreas nor total alimentary tract fat weight was influenced by weight stasis. The separate parts of the alimentary tract did not respond to the weight stasis treatment in the same manner. The weight of the rumen-reticulum, small intestine and large intestine each showed a significant reduction (P < 0.001) in weight. In contrast, neither omasum nor abomasum weight was affected by weight stasis. Total alimentary tract weight was significantly reduced (P < 0.001) by weight stasis. An evaluation of the weights of digesta in the separate parts of the alimentary tract showed that the weight of omasal contents increased significantly (P < 0.01) during weight stasis, while small intestine contents weight decreased significantly (P < 0.01). The weight of contents in either the rumen-reticulum, abomasum, large intestine or total alimentary tract was not influenced by weight stasis.

Feed intake and digestion transactions for diets based on wheaten straw and mature ryegrass diets, both supplemented to provide additional essential nutrients, were compared with those for lucerne hay and high quality forage oats diets in lambs weighing c. 24 kg. The data obtained and comparable published data were used to examine relationships between a range of variables. Decrease in roughage quality, as evidenced by decrease in digestible organic matter (OM) intake, was accompanied by increase in (i) times spent eating, ruminating and chewing rumination boluses, (ii) the quantities of digesta or digesta OM in the reticula-rumen and omasum. It was not associated with increase in the large particle content of rumen or omasum digesta. Over the range of diets, close direct relations were demonstrated between (i) ruminating time and the amount of digesta in the reticulo-rumen, (ii) the amounts of digesta in the reticulo-rumen and omasum, (iii) the OM concentrations in rumen and reticulum digesta, (iv) the OM concentrations in reticulum and omasum digesta, (v) the OM concentration of reticulum digesta and of digesta flowing to the omasum, and (vi) the increase in OM concentration from reticulum to omasum digesta and OM concentration of reticulum digesta. Reticulum digesta were of finer texture than rumen digesta, and the bulk density of digesta particle fractions varied between diets, and sometimes between rumen and large intestine digesta. With a straw-based diet, relative to lucerne hay, small particles (

Groups of six crossbred lambs, three wethers and three ewes, about 22 kg liveweight (LW), were injected subcutaneously with 0, 50, 150 and 250 pg (kg LW) d a y 1 of recombinant DNA-derived bovine growth hormone (rebGH) for 60 days. From blood sampled twice weekly 4.5 h after injection, the mean plasma concentrations of growth hormone (GH) (P

The influence of sodium chloride ingestion via the drinking water upon the flux of fluid and minerals to and from the rumen of sheep has been examined. Four Merino wethers were each prepared with ruminal and bilateral parotid duct fistulas to allow continuous sampling and measurement of flow rates and were offered rainwater which was zero, 136 or 221mM with respect to sodium chloride as the only source of drinking fluid. Parotid salivary flow rate decreased by up to 43% when the saline concentration of the drinking water was increased. There was an inverse relationship between saliva flow rate and the fluid intake, but much of the effect appeared to be due to ingestion of sodium chloride per se. Salt water ingestion caused an increase in the salivary concentration of sodium and phosphate; a decrease in that of potassium; and no change in that of chloride or osmolality. The rate of secretion of sodium varied directly with saliva flow rate. The outflow of water from the rumen to the omasum, or its net absorption across the rumen wall, were not influenced by treatment. In centrifuged rumen fluid samples saline ingestion caused increased levels of sodium, chloride and osmolality; decreased levels of potassium; and no change in calcium, magnesium or phosphate. Outflows of sodium and chloride to the omasum were increased. The apparent absorption of sodium and chloride from the rumen increased proportionately to the inflows of these ions via the saliva and drinking fluid. The additional sodium and chloride ions arising from the ingested saline were absorbed in approximately equal amounts. Saline drinking by sheep leads to a reduction in the rate of secretion of parotid saliva and its accompanying ions, which partially compensates for the added amount of fluid and electrolyte which enter the rumen in the drinking water.

The effects of three phosphorus supplements on the metabolism of phosphorus in the gastrointestinal tract of sheep were examined. One group of sheep was fed on a low phosphorus (P-L) diet and three other groups on diets supplemented with monosodium orthophosphate (P-MSOP), meat and bone meal (P-MBM) or bran (P-ORG). The total phosphorus (TP), ultrafilterable phosphorus (UP) and nucleic acid phosphorus (NP) in the digesta were measured. There was a large net secretion of phosphorus into the rumen and the first quarter of the small intestine, and net absorption from the remainder of the small intestine of all sheep. The relative concentration of phosphorus in the omasum suggested considerable omasal secretion and a subsequent abomasal absorption of phosphorus, but this was considered to be largely an artefact. There were no consistent differences between diets in the net secretion and absorption of TP at sites along the gastrointestinal tract. Sheep fed on the P-L diet secreted more phosphorus per unit of phosphorus intake than sheep on the other diets. Most UP was present in the abomasum and cranial small intestine where the pH was lowest. The concentration of UP fell precipitously in the small intestine, which suggested that this was the major form of phosphorus absorbed and that there was a high degree of complex formation at the higher pH. The concentration of NP was relatively constant, and the lowest NP/TP ratios were found in the cranial small intestine. NP formed in the rumen was mainly degraded in the cranial small intestine. NP represented half the TP in the colon of sheep fed on diet P-L. The results indicate that the form of phosphorus supplement did not influence phosphorus metabolism in the gastrointestinal tract.

Lactating and non-pregnant, non-lactating ewes were compared with respect to voluntary consumption of a medium quality roughage and various aspects of digestion of the roughage as fed at intakes near ad libitum. The lactating ewes, relative to their control counterparts (i) consumed more roughage, (ii) ate more rapidly, (iii) maintained higher levels of digesta in the rumen, omasum, abomasum, and caecum + proximal colon, (iv) showed no difference in particle size distribution in rumen digesta, (v) exhibited enhanced rumination activities and (vi) on average, cleared a particulate marker more rapidly from the rumen. It was estimated that the lactating ewes had a higher energy deficit than the controls. It was concluded that (i) the greater rate of removal of feed dry matter from the reticula-rumen (mass/time) during lactation was largely attributable to the enhancing effect of the prevailing higher reticulo-rumen digesta load on rumination, digestion and propulsion, (ii) neither capacity to use energy nor physiological capability of the reticula-rumen played a primary limiting role in the regulation of roughage intake, with the control of animals, (iii) the comparative data are consistent with a concept that energy metabolism and digesta load interact in the regulation of roughage intake, and (iv) scope exists for increasing consumption of the roughage by appropriate physiological manipulation of the animal.

Six Friesian heifers (c. 300 kg) fitted with cannulas were given diets of wheat straw sprayed with NaOH (4.4 % wlw) and essential minerals either with or without urea (3% w/w). The total protozoal numbers in the rumen fluid were not significantly different between dietary trcatments (mean 6.2 X 104/ml). However, there were more holotrichs and medium-size entodiniomorph protozoa in the rumen fluid of the cattle given the HU and LU diets than the Hand L diets. Protozoal counts in the omasal fluid were 44% of those in rumen fluid. The apparent digestibilities of OM and neutral-detergent fibre (NDF) in the stomach and in the total tract were lower with high than low feed intakes. The urea supplement enhanced the digestibilities of OM and NDF in the stomach and in the total tract. The total nitrogen (N) and non-ammonia N (NAN) flowing to the omasum and to the duodenum per unit of N intake were significantly greater with the low than the high feed intakes and with urea supplementation of the diets than without urea supplementation. The proportions of total microbial N and bacterial N in omasal NAN were higher with the supplement of urea than the unsupplemented straw. The bacterial N in the NAN flowing to the omasum was lower for the high than the low intakes. Concentrations of ammonia-N and total volatile fatty acids in rumen fluid were higher for the ureasupplemented straw than the unsupplemented straw. The high level of feed intake was associated with higher water volume and solid contents in the rumen.

Sulfur pools in the rumen and sulfur flows from the rumen were investigated in two experiments with sheep on a diet containing equal parts of oaten and lucerne chaffs. The diet was fed at two levels, either chopped or pelleted, and with intraruminal DL-methionine supplements. Ruminal fluid volumes and fluid flows to the omasum were measured. None of the treatments influenced ruminal fluid volume. Fluid flow to the omasum, however, was increased by increasing dry matter intake (DMI), and was further enhanced by feeding chaffed hay rather than the same materials ground and pelleted; the DL-methionine supplement had no effect. First approximation of the ruminal sulfur pools and of sulfur flows to the omasum were derived from the concentration of sulfur in true digesta and the ruminal fluid volume or fluid flow. Increasing DMI from 500 to 1000 g/day resulted in larger ruminal pools of total (1096 v. 792 mg), neutral (1016 v. 731 mg) and protein (479 v. 419 mg) sulfur, but the reducible sulfur pools were not affected by the level of DMI. Infusions of DL-methionine increased the ruminal sulfide sulfur pool irrespective of level of DMI. The first approximation of total sulfur flow was increased by 1660 mg/day at the higher level of DMI, due mainly to increases of 710 mg S/day as protein sulfur and 859 mg S/day as non-protein neutral sulfur. Flows of inorganic sulfate and ester sulfate sulfur, although small in comparison with organic sulfur flows, increased with level of DMI. Sulfide sulfur flows were also increased at the higher level of DMI, and were almost doubled by intraruminal infusions of DL-methionine.

Protein production in the rumen of sheep fed on a virtually protein-free diet supplemented with urea and higher volatile fatty acids (VFA) and yielding 600 g digestible organic matter per day amounted to 90 g/day. When gelatin was substituted for the higher VFA and 50% of the urea nitrogen, microbial protein production remained at a similar level (91 g/day); with casein, production increased to 101 g/day, and with zein to 104 g/day. Nitrogen balances increased from 4.1 g/day in sheep fed on the casein diet to 5.5 g/day in those fed on the zein diet (P < 0.05). These values were both significantly higher than those for the urea/VFA or gelatin-containing diets, reflecting the different levels of microbial protein production on the respective diets. In addition, 44 g un-degraded zein left the rumen daily, accounting for the increase in nitrogen balance on this diet above that on the casein diet. Negligible amounts of nitrogen were recycled on the urea/VFA, gelatin, and casein treatments, but at least 7.5 g recycled nitrogen was utilized in the rumen daily on the zein diet. This is equivalent to 47 g protein, sufficient in itself to satisfy the maintenance requirement of the sheep for protein. The yields of protein from ruminal fermentation on the three protein treatments suggest that the maximum possible yield may exceed 20 g/100 g organic matter digested in the rumen.

The pattern of chromium oxide (Cr2O3) excretion was studied in Merino wethers. The sheep were dosed twice daily with Cr2O3 at fixed times. In the main series of experiments, sheep were fed fresh herbage in metabolism pens. An oaten chaff diet was also employed. In all cases a diurnal pattern of Cr2O3 excretion in the faeces was observed. The pattern was not consistent from day to day, nor was there any consistent effect of level of intake or feeding frequency on the excretion pattern. Distributions of Cr2O3 were examined in eight grazing sheep killed ½–4 hr after dosing. In six of the animals high concentrations of the marker were found to be mixed with the reticuloruminal ingesta, while low concentrations were observed in the other stomachs. In the remaining two animals high concentrations were observed in the omasum and abomasum, from which it was inferred that the dose had by-passed the main bulk of the reticulorurninal ingesia. It seems unlikely that any real advantage is to be gained by painstaking selection of particular times for dosing and faeces sampling in different environments; and it is suggested that convenient fixed times — say 6 a.m. and 3 p.m., or 9 a.m. and 5 p.m. — should prove satisfactory in estimating output of faeces of grazing animals under a wide range of conditions. In 40 sheep-periods of 10–14 days, the mean daily output of faeces organic matter by pen-fed wethers was estimated with mean 101% and error ±12% of the true figures, by analysis of a single bulked sample obtained by dosing and grab sampling at about 9 a.m. and 5 p.m. daily. In 40 periods when samples were bulked over 5–7 days the average estimate was 102 ± 14% of the true figure. Comparison under extensive grazing conditions showed that estimates obtained by dosing and sampling only once per day were generally some 15% higher than those obtained by dosing and sampling twice daily.

When sheep were fed on a diet supplying 0.61 g sulphur per day, 82 g microbial protein was produced daily in the rumen. Raising the sulphur intake to 1.95 g/day increased protein production to 94 g/day (P .: 0.05), but there was no further increase when the intake was raised to 3.42 g/day. Protein production was not influenced by the s form of the supplementary sulphur. Sulphur as cystine resulted in higher rumen fluid sulphide levels than sulphur as inorganic sulphate. Nevertheless, measurable amounts of free cystine flowed out of the rumen when cystine was given. This may explain the higher nitrogen balances supported by cystine than by sulphate. Sulphur balances were always positive, and there were no differences between treatments. At least 0.44 g sulphur was recycled daily when the basal die twas given. This accounted for 42% of the total sulphur flowing out of the rumen. The importance of sulphur recycling is discussed.

The production of volatile fatty acids (VFA) in the rumen of sheep was estimated by isotope dilution techniques. The 12 diets used consisted of dried ryegrass and forage oats and covered a wide range of levels of cell wall constituents (46–40% of the organic matter), crude protein (6–32%), and soluble carbohydrate (5–18%). Each diet was offered at a level equal to approximately 90% of the sheep's ad libitum intake. The production of VFA was correlated with the total amount of organic matter digested in the alimentary tract (r = 0.93–0.95). The mean VFA production per 100 g of organic matter digested in the alimentary tract was equivalent to 56.8 g, 243 kcal, or 0.85 mole. Values for individual diets varied about these means with a coefficient of variation of 6–7%. Rates of VFA production in, and VFA absorption from the rumen were correlated with VFA concentration in rumen liquor (r = 0.67, r = 0.67) and the rumen VFA pool (r = 0.81, r = 0.79). Approximately 76% of the VFA produced in the rumen was absorbed from the rumen, 19% was absorbed from the omasum and abomasum, and 5% passed from the abomasum to the intestines.

The voluntary feed consumption (VFC) and body weight gain of lambs initially 12 weeks old and weighing 22 kg were measured when diets based on whole wheat grain and varying in straw content were offered. The basal diet comprised, on an organic matter (OM) basis, about 82 parts whole wheat grain and 18 parts protein concentrate; ground wheaten straw was added to provide diets with 2%, 7% or 13% straw. Daily VFC, expressed in relation to body weight in kg0.75 (BW0.75), increased from 85.6 with 2% straw through 90.4 with 7% straw to 94.2 with 13% straw. The corresponding OM digesti bilities were calculated to range from 84.8 to 77.6%. However, the intake of digestible OM and the rate of body weight gain were not affected by the straw content of the diet, the respective mean values for all lambs being 73g/day BW0.75 and 293 g/day. Lambs initially 25 weeks old and weighing 38 kg were offered a diet (2% straw) based on wheat in which the wheat was presented either as whole grains or in ground and pelleted form. With the whole grain diet the daily rates of OM intake, digestible OM intake and body weight gain were 75.6 g/ BW0.75, 64.7 and 254 g respectively; the corresponding values with the ground grain diet were about 20% lower. Studies involving the slaughter of animals showed that a large proportion of the wheat grain consumed reached the rumen in the form of whole grains and these contributed significantly to the dry matter of the ruminal digesta. The rate of ruminal digestion of whole wheat grains was slow (37% in 96 hr) when the sheep were given a diet based on wheat. By contrast, when a roughage diet was consumed the rate was high (81% in 96 hr). Fractured grain was rapidly digested in the rumen (67% in 20 hr). The mean residence time of water-soluble marker in the rumen and the rate of digesta flow from the rumen were greater in fistulated sheep given a whole grain diet than with a ground grain diet. The diets also differed with respect to the concentration of potassium in rumen liquor, the rumen potassium pool size and the rate of flow of sodium and volatile fatty acids to the omasum. It was concluded that the roughage requirement of the ruminant lamb fed on concentrate diets based on whole wheat did not exceed the equivalent of 2 g ground straw per 100 g diet. The possibility of a higher roughage requirement with ground wheat diets is suggested. ___________________ *Part VII, Aust. J. Agric. Res., 24: 387 (1973).

In a 4 x 4 Latin square design experiment, sheep were fed on a basal ration which supplied 0.61 g sulphur per day, or the basal ration supplemented with 1.4 g inorganic sulphate sulphur, or 1.4 g cystine sulphur, or 1.4 g sulphate sulphur plus 1.4 g cystine sulphur per day. All forms of sulphur supplements increased the daily flow of protein sulphur from the rumen to the omasum (P < 0.05) above basal. Only the cystine treatments increased the flow of sulphide (P < 0.005), ester sulphate (P < 0.005), soluble organic sulphur (P < 0.05), and cystine (P < 0.05), and increased the ruminal sulphide concentrations above basal (P < 0.005). From 7.0 to 12.6% of the added cystine was not degraded in the rumen. In three animals less than 3 % of the added sulphate, alone or in combination with cystine, passed unchanged to the omasum. The fourth animal (67) differed from the others (P < 0.05): the added sulphate was poorly reduced in the rumen, and 62% reached the omasum unchanged. The sulphur composition of the digesta collected from the omasum was: protein sulphur, 55-70%; soluble organic sulphur, 13-22%; inorganic sulphate sulphur (excluding sheep 67), 2.2-2.6 %; ester sulphate sulphur, 1.8-3.4 %; and sulphide, 0.4-28%. Excluding sheep 67, 36% of the dietary sulphur was absorbed from the rumen when the sulphur was added as sodium sulphate or as cystine, and 50 % when added in both forms together. There was a net addition of 0.45 g sulphur per day to the rumen on the basal diet. The influence of the amount and the form of the dietary sulphur on the excretion of faecal and urinary sulphur fractions is discussed.

The mean retention time of feed particles in the alimentary tract of sheep was measured by means of a stained-particle technique, when lucerne hay or a diet of wheaten straw + wheaten hay (1 : 1) was offered ad libitum. The levels of intake of the straw diet and lucerne hay were equivalent to 11.8 and 25.8 g organic matter/day/kg body weight. The mean retention time of particles in the entire alimentary tract when the straw diet was offered was 57.5 hr, this consisting of 36.3 hr in the rumen + omasum and 21.2 hr in the abomasum + intestines. The retention time in the rumen + omasum was calculated to consist of (a) 19.7 hr during which the particles were being degraded to a size at which transfer from the rumen could be readily effected, and (b) 16.6 hr of residence in the rumen + omasum as small particles. With lucerne hay, the retention times were shorter: small particles spent 10.8 hr in the rumen + omasum and retention time in the abomasum + intestines was 16.1 hr. It was calculated that only a small proportion of the difference between the straw diet and lucerne hay in organic matter intake could be attributable to differences between the diets in the rate of removal of finely divided particles of organic matter from the rumen.