1. An experiment was conducted to determine the effect of the abomasal parasite, Haernonchus contortus, on the pattern of digestion and nutrient utilization in Merino sheep. There were three groups of sheep: infected with H. contortus (300 larvae/kg live weight) (n 5), sham-infected by transferring blood from the jugular vein to the abomasum, and uninfected (control) sheep (n 9) which were fed daily rations equal to amounts consumed by 'paired' animals in the two other treatment groups. A diet containing (g/kg): lucerne (Medicago sativa) chaff 490, oat chaff 480, ground limestone 10, urea 10, and sodium chloride 10, was given in equal amounts at 3-h intervals.2. Continuous intrarumen infusions (8 d) of chromium and ytterbium were made in order to measure the flow of digesta through the rumen, duodenum and ileum with 16NH,CI included in the infusate for the final 3 d. The toss of blood into the gastrointestinal tract was measured using 51Cr-labelled erythrocytes and the rate of irreversible loss of plasma urea was measured with reference to a single intravenous injection of [Wlurea. Samples of rumen fluid were taken for analysis of volatile fatty acid (VFA) concentrations.3. The infected and sham-infected sheep developed severe anaemia during the period over which digestion and metabolism measurements were made (packed cell volume 0 118 (SE 00042) and 0.146 (SE 0.0073) respectively). The corresponding rates of blood loss into the gastrointestinal tracts were 253 (SE 23) and 145 (SE 17) ml/d. 4. The proportions of VFA in rumen fluid were altered (P < 005) in the infected group with a decrease in the ratio, acetate: propionate (control 3.28, infected 2.58, standard error of difference (SED) 0.21). There was also an increase in rumen fluid outflow rate (P < 0.01) from 405 litres/d in the control group to 5.53 litres/d in the infected group (SED 043). Water intake was higher (P c 005) in the infected than in the control animals (2.25 and 1.84 litres/d respectively; SED 0.14). 5.There was a decrease (P i 0.05) in apparent digestion of organic matter in the forestomachs of infected sheep (032 compared with 0.39 in the control, SED 0.02). There was also a decrease (P < 0.05) in the apparent digestion of organic matter across the whole digestive tract (0.65 control, 061 infected, SED 0.013).6. There was a loss of 2.6 and 1.8 g blood nitrogen/d into the gastrointestinal tract of the infected and shaminfected sheep respectively. In the infected sheep approximately 50 % of this N was accounted for as additional ammonia leaving the abomasum compared with 20% in the sham-infected group. The additional nonammonia-N (NAN) entering the duodenum of parasitized or sham-infected animals was reabsorbed before the ileum. There was no effect of infection or sham-infection on the synthesis or digestion of microbial NAN.7. There was a higher (P < 0.001) rate of plasma urea irreversible loss in the infected sheep (8.9 control, 12.2 infected, 109 sham-infected, SED (control v. treated) 087 g N/d). This was apparently due to increased abso...

An experiment, using a total of 320 Merino ewes, over two successive breeding seasons was conducted to investigate the separate effects of energy-yielding and protein-yielding nutrients on ovulation rate in sheep. The available energy-yielding or protein-yielding nutrients in the blood of sheep fed a maintenance pelleted ration were increased by either intravenous infusions of metabolites (acetate, glucose or acetate + glucose), feeding lupin grain, modification of the pattern of rumen fermentation to increase propionate production using the ionophore, lasalocid, or by feeding of ruminally undegradable protein (formaldehyde-treated casein). All treatments were given for 9 days prior to and including expected time of ovulation. Ovulation rates were measured by laparoscopy. In the first season (the 1984 experiment) when the effects of lupin grain, glucose + acetate and formaldehyde-treated casein were compared, ovulation rates were increased significantly in the group fed lupin (29%, P less than 0.001) and the group infused with glucose + acetate (24%, P less than 0.01). There was an apparent (17%) but statistically non-significant increase in the group fed casein. In comparisons between lupin grain, glucose, acetate, glucose + acetate, formaldehyde-treated casein and lasalocid in the 1985 experiment there were similar significant increases in ovulation rates in the groups fed lupin, and those infused with glucose or glucose + acetate (approximately 25%, P less than 0.001). The increase in the group infused with acetate was lower at 14% (P less than 0.05) and the increases of 7% in the groups fed casein or lasalocid were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

The net uptake and oxidation of glucose by leg muscle, pregnant uterus, and lactating mammary gland, together with the rate of irreversible loss and oxidation of glucose in the whole body of Merino ewes are reported. The ewes were fed on either chaffed oaten hay (OR), chaffed lucerne hay (L), or a mixture of chaffed oaten and lucerne hays (OHL). Measurements were made during five different physiological states: dry (nonpregnant), at 94 and 125 days of pregnancy, and at 20 and 50 days after lambing.

A combination of the isotope-dilution and arterio-venous (A V) difference techniques was used to study simultaneously the metabolism of valine in the whole body and in the hind-limb muscles of fed and starved (40 h) sheep. The net exchange of gluconeogenic amino acids across hind-limb muscles was also studied.Valine entry rate was unaffected by nutritional status. There was significant extraction of valine by hind-limb muscles in both fed and starved sheep. The percentage of valine uptake decarboxylated was higher (P < 0'05) in fed sheep but the amount of valine decarboxylated was not significantly different. The proportion of valine uptake that was transaminated was about 30 times higher in starved sheep. About 54% of valine taken up by hind-limb muscle of starved sheep was metabolized.The corresponding value for fed sheep was 21 %. The contribution of CO2 from valine decarboxylation to total hind-limb muscle C02 output was about 0·2%.The output of alanine in both fed and starved sheep was low but the output of glutamine was relatively high and roughly equivalent to the amounts of aspartate, glutamate and branched-chain amino acids that were catabolized. This study has confirmed that valine is catabolized in sheep skeletal muscle, and shown that glutamine is a major carrier of amino nitrogen out of muscle.

A sheep hind-limb preparation used for the study of muscle metabolism by arteriovenous (A V) difference procedures was validated by identifying the muscles which contribute to venous drainage at different positions along the lateral saphenous vein. Dissection of the hind limbs of six mature sheep (three wethers and three ewes) showed that venous blood from the plantar group (M. gastrocnemius, M. soleus, M. plantaris, M. flexo digitorum profundus), and from M. semitendinosus, M. biceps femoris, M. gracilis, M. pectineus and M. adductor muscles entered the lateral saphenous vein but the position of the tip of the blood sampling catheter was found to be critical. In order to sample venous blood from all of the muscles listed above, and to minimize the contribution of blood from non-muscular tissues, blood samples must be taken 25-26 cm from the junction of the cranial and caudal branches of the lateral saphenous vein (for average size sheep of body length about 108 cm and height at withers about 73 cm).The estimation of sheep hind-limb muscle mass is a necessary concomitant of A V difference studies, and a combined tritiated water and dye-dilution procedure has been used to measure both muscle mass and blood flow.The muscle mass estimated in vivo by this technique was closely similar to the true muscle mass obtained by dissection, the range of values of the difference between true and calculated muscle mass expressed as percentage of the true mass being 0·5-16%. It is concluded that these techniques are sufficiently accurate for use in the quantitation of exchange of metabolites across the hind-limb muscle preparation.Patterns of amino acid uptake and release by muscle need to be related to the amino acid profile of the tissue, and the amino acid content of a representative muscle, M. biceps femoris, was determined, and the results compared with published data.