Changes in the jugular haematocrit of sheep during feeding

Intact and splenectomized sheep with and without a rumen fistula were used to investigate changes in the jugular blood haematocrit and plasma osmolality during hourly and once-daily feeding regimes. Osmolality was also estimated in the ruminal fluid of fistulated sheep with spleens. Haematocrit decreased in sheep with spleens before they were given a once-daily feed; it increased when these sheep started to feed, reaching a maximum increase of 13% after 30 min of feeding; it decreased during the remaining 45 min of feeding time and usually continued to decrease after feeding stopped. These changes were not due to diurnal influences. Splenectomized sheep fed once daily showed only small decreases in haematocrit before they were fed. Increases occurred with the onset of eating but they were smaller (7%) than in intact sheep and were of shorter duration. In hourly fed sheep with spleens, haematocrit decreased in the early stages of sampling in a manner similar to that for sheep fed once daily. The changes in haematocrit that did occur were not related in any obvious manner to the feeding regime. The haematocrit in splenectomized sheep fed hourly was stable throughout feeding. Variations in the haematocrit in splenectomized sheep, equivalent to a range of 13% in one of them, were observed in a series of blood samples obtained during a 5-h period remote from the feeding time. Large increases occurred in osmolality of ruminal fluid when sheep were fed daily and this was abolished by hourly feeding. Plasma osmolality in sheep fed once daily increased slowly. Maxima occurred after 100 min from the start of eating and were 7% greater than prefeeding values. Only minor changes were observed when these sheep were fed hourly.

The effect of pregnancy and lactation on food intake, gastrointestinal anatomy and the absorptive capacity of the small intestine in the albino rat

1. Food consumption, live weight, anatomical measurements on the gut organs and the absorptive capacity of the small intestine for L-leucine and D(plus)-glucose were made on virgin (control), pregnant and lactating albino rats. 2. Food intake increased by approximately 60% during pregnancy and a further 250% during lactation. 3. Pregnancy did not markedly influence the gross anatomy of the gastrointestinal tract. There was evidence for increased villus height and percentage water in the small intestine and for increased length of the colon during pregnancy. 4. During lactation, the alimentary canal progressively increased in weight and size. It partially regressed following weaning. 5. All anatomical measurements, except the length of the small intestine, completely regressed to control values within 20 d of weaning. The increased intestinal length had not completely regressed by day 30 post-weaning. 6. No significant change was observed in absolute absorption of glucose or leucine during pregnancy. 7. Absolute absorption of leucine and of glucose was increased during lactation. Greatest absorption occurred on the 10th day of lactation. 8. Results for absorption of leucine and glucose per unit length indicated that the ability of the mucosal cells to absorb or the number of absorptive cells/mm had changed during lactation and the post-lactation periods.

Rate of passage of digesta in sheep. 4. Passage of marker through the alimentary tract and the biological relevance of rate-constants derived from the changes in concentration of marker in faeces

1. The rates of passage of markers of fluid and particulate digesta through the sheep alimentary tract have been described mathematically in single-injection experiments by analysing the concentration curves of marker excretion in faecal dry matter and then predicting these concentrations by means of an equation containing two exponential terms. Three components related to this equation are a transit time for digesta in the intestines, a half-time of marker in the reticulo-rumen and a half-time tentatively associated with the passage of marker through the caecum and proximal colon. With this approach no surgical interference with an animal is required to obtain meaningful information about gut function.

2. Abomasal cannulation did not affect the rate of passage of 51Cr EDTA through the gut.

3. The mean half-times (T1/2) for 51Cr EDTA in the reticulo-rumen and hind-gut, respectively, were 646 and 236 min for a roughage diet and 890 and 607 min for a diet consisting mainly of wheat grain, both diets providing approximately the same amounts of digestible dry matter. These results indicated that the changes in half-times were proportionately much greater in the caecum and proximal colon than in the reticulo-rumen. The mean transit time of marker through the digestive tract also increased from 721 to 1345 min when the concentrate diet was given.

4. The complex of chromium-51 with EDTA was excreted faster in faeces than cerium-144–praseodymium-144 when both were given together as a single injection into the reticulorumen. This was caused mainly by differential rates of elimination of water and particulate matter from the reticulo-rumen.

Rate of passage of digesta in sheep. 3. Differential rates of passage of water and dry matter from the reticulo-rumen, abomasum and caecum and proximal colon

1. Three groups of sheep receiving 400, 800 and 1200 g lucerne chaff/d in equal hourly meals were killed. The large intestines were removed and divided into segments 15 cm long to provide information on the amounts and dry-matter contents of digesta and on the rates of passage of digesta and absorption of water along the large intestine.

2. With increasing intakes of food, increases were observed along the entire large intestine in the amounts of wet digesta present, in the transit rates of digesta and in the rates of absorption of water. The mean retention time of digesta in the large intestine decreased with increasing food intake, being 1737, 1056 and 692 min respectively.

3. Four patterns of sodium and potassium concentrations in digesta water along the large intestine were found.

Trichostrongylosis and wool growth. 2. The wool growth response of infected sheep to parenteral and duodenal cystine and cysteine supplementation

Two experiments are reported. In experiment 1, light infections with the intestinal nematode Trichostrongylus colubriformis reduced wool growth of sheep by 42 per cent compared with pair-fed controls. There was no significant difference in wool growth between those sheep given a cystine supplement as an intraperitoneal pellet and those given a daily intra-duodenal injection of cystine, although cystine was poorly absorbed from the peritoneal cavity. In experiment 2, fifteen sheep were fed a maintenance ration and their wool growth rates defined. When six of the sheep were given a daily intra-duodenal drip containing 2 g cysteine hydrochloride, and six sheep were given the same drip intravenously, their wool growth rate increased by a mean of 33 per cent compared with the wool growth of the three untreated sheep, irrespective of the route of administration of the cysteine. Three sheep in each group of six were then lightly infected with Trichostrongylus colubriformis and the wool production of all sheep was measured in the presence and absence of the daily cysteine supplement via the two routes. The infection depressed wool growth, but did not influence the wool growth response to either route of cysteine supplementation. It was concluded that the reduced wool growth induced by trichostrongylosis could not be attributed to malabsorption of cysteine. Evidence was obtained that sheep resistant to Trichostrongylus colubriformis produced less wool when subjected to a larval challenge.

Rate of passage of digesta in sheep. 1. The effect of level of food intake on marker retention times along the small intestine and on apparent water absorption in the small and large intestines

1. Sheep given 400 and 1200 g lucerne chaff/d in equal hourly meals were infused continuously with the complex51Cr EDTA into the rumen for 5 d and then slaughtered. The retention times of51Cr EDTA along the small intestine and the apparent quantities of water absorbed in the small and large intestines were calculated.

2. The apparent quantities of water absorbed for the 400 and 1200 g food intakes were 5844 and 13110 ml/d in the small intestine and 2101 and 8520 ml/d in the large intestine respectively.

3. The mean total retention times of51Cr EDTA in the small intestine were 136 and 91 min for the sheep given 400 and 1200 g/d respectively. The marker was retained up to seventeen times longer in the ileal than in the duodenal or proximal jejunal segments.

Acute in vivo studies on glucose absorption from the small intestine of lambs, sheep and rats

1. Rates of disappearance of glucose from ligated loops of small intestine in lambs, adult sheep and young rats were studied. The concentration of glucose in the lumen decreased exponentially with time, suggesting that within a range of concentrations of 166–277 m-moles/l glucose was absorbed mainly by passive diffusion.

2. The rate of absorption of glucose from a 166 mM-solution based on either zero or first order kinetics and expressed as m-moles/m small intestine per h decreased along the intestine from the duodenum to the ileum in lambs and rats. The decrease was slight in adult sheep.

3. The total absorptive capacity of the small intestine of adult grazing sheep for glucose from 166 mM-solutions (06 m-moles/kg body-weight per h) was approximately 25% of that for lambs less than 1 week of age.

4. Young rats had a greater absorptive capacity of the small intestine (12.9m-moles/kg body-weight per h) than adult sheep of about 40 kg body-weight (0.6 m-moles/kg body-weight per h) and this largely reflected a longer small intestine per unit body-weight.

5. The absorptive capacity of lambs for glucose was greater when the level of voluntary lactose intake was increased before an experiment. The absorptive capacity of the ileum of adult sheep given wheat was greater than that of grazing adult sheep.

6. Developmental changes in glucose absorption are discussed in relation to normal changes in diet and to changes in the morphology of the small intestine with age.

The effects of intravenous urea infusions on nitrogen metabolism in sheep

The effects of intravenous infusions of measured amounts of urea solution into sheep, providing c. 5 g urea nitrogen per day, were studied in sheep on four rations differing in crude protein and readily available energy content. Nitrogen balances, water intakes, urea nitrogen excretions, and diurnal variations in plasma urea and rumen ammonia levels were compared over 8-day collection periods. When corn starch and dried molasses provided readily available energy in addition to crushed pure cellulose the retention of infused urea nitrogen was 50 % compared with 40 % with crushed pure cellulose. It is suggested that as nitrogen retention was similar to the increases in nitrogen balance, the nitrogen retained was first transported into the rumen, where it was synthesized to microbial protein. Thus corn starch, molasses, and crushed cellulose provided suitable energy levels for utilization of the extra nitrogen by the rumen micro-organisms. On a low protein, all roughage ration the nitrogen transferred into the rumen produced increased rumen ammonia levels and was subsequently reabsorbed and excreted in the urine.

Absorption of Volatile Fatty Acids From the Reticulo-Rumen and Abomasum of Sheep

Ten acute experiments were performed on sheep to study the relative rates of absorption of volatile fatty acids in acid solution from the reticulo-rumen and abomasum. When the solutions in the two organs were approximately the same in initial tonicity, pH, and volatile fatty acid concentration, the total volatile fatty acid was absorbed at about equal rates from both the reticulo-rumen and the abomasum. The individual volatile fatty acids were absorbed from the abomasum at different rates; the rate was faster the greater the number of carbon atoms in the molecule. Ammonia in acid solution was not absorbed from the reticulo-rumen or from the abomasum.

The absorption of lactic acid from the reticulo-rumen of the sheep

A series of acute experiments has been carried out on sheep to study some of the factors which influence the rate of absorption of lactic acid from the ligated washed�out forestomachs.

Microbial metabolism in the forestomachs and the large intertine of sheep

Sheep were fed on either lucerne chaff, high wheat grain, or high maize grain rations. Analyses were made on digesta from the rumen and large intestines of cannulated and slaughtered animals. The results for the large intestine showed that, when equal quantities of dry matter are given, the composition of the ration can affect the pH, the water content, and the total dry matter of the digesta; diet can also affect the total quantities of volatile fatty acid and ammonia in the organ.The proportions of the individual volatile fatty acids in the caecal fluid were not affected by the different diets fed in this experiment. The data did not suggest any consistent pattern in the pH or in the concentrations of ammonia and volatile fatty acid in the caecal fluid during the 24 hr between feeds.

Ruminal Flora Studies in the Sheep IV. the Influence of Varying Dietary Levels of Protein and Starch Upon Digestibility, Nitrogen Retention, and the Free Microorganisms of the Rumen

Data are presented from a replicated feeding trial with sheep, designed to determine the influence of varying dietary intakes of starch and protein upon digestibility, protein utilization, and the numbers and types of "free" bacteria in the rumen.

Ruminal Flora Studies in the Sheep

A method of obtaining ruminal samples for the investigation of the "free" microorganisms of the sheep's rumen by means of a stomach-tube is described.