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Biomedical subjects

A R Sykes

Publications and source records attributed to A R Sykes.

At least 37 records · Page 2Linked to original sources
PubMed1991

Nitrogen transactions along the digestive tract of lambs concurrently infected with Trichostrongylus colubriformis and Ostertagia circumcincta.

Twelve lambs, paired on the basis of live weight, were cannulated in the abomasum, in the proximal jejunum approximately 4 m distal to the pylorus and in the terminal ileum. Six were infected with 3000 Trichostrongylus colubriformis and 3000 Ostertagia circumcincta larvae each day for 18 weeks and the remainder were pair-fed to individual infected lambs. All animals were offered ryegrass (Lolium perenne)-white clover (Trifolium repens) pasture, cut daily. Dry matter (DM) intake, live weight, faecal egg concentration, plasma pepsinogen and plasma protein concentrations were measured weekly. During weeks 7 and 17 after commencement of infection, the flow of digesta along the gastrointestinal tract was measured together with enteric plasma loss and true digestion and absorption of 125I-labelled albumin in the small intestine. DM intake was depressed by parasitism, being 1331, (SE 70), 423 (SE 32) and 529 (SE 52) g/d during weeks 3, 7 and 17 respectively. The flow of nitrogen at the proximal jejunum and in faeces was increased by parasitism during week 7 and at the abomasum and ileum during week 17. Plasma protein-N loss (g/d) into the gastrointestinal tract was 0.68 (SE 0.091) and 1.97 (SE 0.139) during week 7, and 0.85 (SE 0.158) and 1.96 (SE 0.396) during week 17, in control and infected sheep respectively. True digestion and absorption of albumin in the proximal small intestine, the site of infection, was very low (mean 0.08) and was not affected by parasitism. Between the abomasum and terminal ileum absorption of albumin was high (mean 0.87) and again was not affected by parasitism. It was calculated that of the total increase in endogenous protein passing from the ileum tract as a result of infection, plasma protein comprised only a small percentage (10-36%). The major proportion of digestion and absorption of protein occurred in the distal small intestine beyond the site of infection and was not affected by infection.

Albumins↗
PubMed1990

Measurement of plasma osteocalcin in sheep: assessment of circadian variation, the effects of age and nutritional status and the response to perturbation of the adrenocortical axis.

An assay for plasma osteocalcin (BGP) in ruminants is described. Satisfactory cross-reaction was obtained for bovine BGP in several species, namely ovine, cervine, caprine and human. Sample stability at room temperature, after freezing and thawing and after lyophilization and reconstitution is described. Sheep of both sexes have been used throughout and no significant sex effect has been noted. A series of experiments showed a lack of circadian rhythm of plasma BGP concentration in sheep. Plasma BGP values from sheep ranging in age from 0.25 to 7 years fell exponentially from 300 ng/ml at 0.25 years to approximately 50 ng/ml at 1.25 years of age where it remained until the end of the study at 7 years. Long-term administration of adrenocorticotrophic hormone (ACTH) depressed plasma BGP concentrations, although plasma BGP levels were not affected sufficiently by short-term administration of ACTH to increase plasma cortisol concentrations 10-fold during a period of 4 h. It was confirmed that dietary phosphate deficiency depressed plasma BPG concentrations. It is concluded that neither circadian variation nor the short-term stress of handling and bleeding untrained animals need be considered in sampling sheep for measurement of plasma BGP concentration and that the change with age reflected the pattern of development of skeletal maturity in sheep. Values in both growing and mature sheep were at least 6 times higher than in human subjects, which may reflect the 10-fold higher skeletal growth rate in sheep than in humans. This high skeletal activity in sheep may have been selected for in the development of highly productive breeds.

Adrenocorticotropic Hormone↗
PubMed1990

Effect of copper oxide wire particle treatment on establishment of major gastrointestinal nematodes in lambs.

Eighty-four 10-week-old lambs were used to investigate the effect of copper oxide wire particle treatment on the establishment of major gastrointestinal nematodes. They were maintained on pasture previously treated to minimise larval contamination. Five grams of uniform sized copper oxide wire particles were given orally five days before infection with either 20,000 Trichostrongylus colubriformis larvae, 20,000 Ostertagia circumcincta larvae or 3000 Haemonchus contortus larvae given as three doses at three-day intervals. The animals were slaughtered 21 or 22 days after the last infective dose. Parasite burdens in the lambs treated with copper oxide wire particles were reduced by 96 per cent in the case of H contortus and by 56 per cent in the case of O circumcincta compared to burdens in controls. There was no significant effect of copper particles on the establishment of T colubriformis.

Abomasum↗
PubMed1990

Effect of ostertagiasis on copper status in sheep: a study involving use of copper oxide wire particles.

Lambs infected with Ostertagia circumcincta larvae and uninfected controls were either doses with 5 g copper oxide wire particles (COWP) or remained undosed. The change in abomasal pH was monitored from duodenal digesta and that in liver copper concentration from initial liver biopsy samples and liver obtained at necropsy after 22 days. Infection increased the pH of digesta from 2.5 to 4.5. The change in liver copper content in sheep not treated with COWP was +6.1 mg (12.6 per cent) and -6.8 mg (13.8 per cent) in control and infected sheep, respectively. Significantly greater amounts of COWP were recovered from the abomasa of infected than from control animals (3.6 +/- 0.23 and 1.6 +/- 0.55 g, respectively) and hepatic uptake of copper from COWP was 0.7 and 1.8 per cent of the dose, respectively. There were significant relationships between the pH of duodenal contents and COWP retained, soluble copper concentration in duodenal digesta and hepatic uptake of copper. It was concluded that, through causing an increase in pH in abomasal and duodenal digesta, gastrointestinal nematodes interfere with copper metabolism.

Abomasum↗
PubMed1989

The effects of a concurrent infection of Trichostrongylus colubriformis and Ostertagia circumcincta on calcium, phosphorus and magnesium transactions along the digestive tract of lambs.

Twelve lambs, paired on the basis of live weight, were cannulated in the abomasum, proximal jejunum and terminal ileum. Six were infected with 3000 T. colubriformis and 3000 O. circumcincta larvae per day for 18 weeks. The other six lambs were pair-fed to the infected lambs. All animals were offered fresh ryegrass and white clover pasture, cut daily. Dry matter intake, live weight and plasma Ca, P and Mg concentrations were measured throughout the experiment. During weeks 7 and 17 post-infection, digesta flow along the gastrointestinal tract of infected and control animals was measured. Parasitism depressed dry matter intake by 60 per cent and was associated with a reduction in retention of Ca, P and Mg in both infected and control animals. During weeks 7 and 17, parasitism increased the flow of Ca past the proximal jejunum and, during week 17, the flow of P past the terminal ileum. Increased endogenous Ca and P losses, together with a net reduction in absorption of Ca and P, were associated with depressed plasma Ca and P concentrations. These findings, together with evidence of reduced addition of P to anterior regions of the tract, indicate induced Ca and P deficiency. There was evidence for compensatory absorption of Ca and P in the large intestine and distal small intestine, respectively. Magnesium metabolism was apparently not affected by parasitism.

Animals↗
PubMed1989

Theoretical considerations in the estimation of rumen fractional outflow rate from various sampling sites in the digestive tract.

The digesta markers 103ruthenium phenanthroline (Ru-P) and 51Cr-EDTA were continuously infused into the rumen of young lambs offered clover hay ad lib. indoors or grazing pure species swards of either lucerne (Medicago sativa), white clover (Trifolium repens), ryegrass (Lolium perenne) or prairie grass (Bromus catharticus). Following the cessation of infusion the fractional outflow rate (FOR) of markers from the rumen was estimated from the rate of decline of marker concentration in rumen and abomasal digesta (Expt 1), abomasal digesta and faeces (Expt 2) and duodenal digesta and faeces (Expt 3). Estimates of FOR from the rumen were similar when based on rumen and abomasal sampling but estimates from abomasal and duodenal sampling were significantly higher than those from faeces. A simulation of a two-compartment model with variable FOR was performed to calculate faecal excretion curves following continuous marker infusion or the administration of a single marker dose into the rumen. Analysis of the descending portion of these theoretical faecal excretion curves yielded values of FOR from the rumen which differed from the values entered in the equations. The magnitude of the difference depended on the ratio of the values of FOR from the caecum and rumen entered in the equation. This suggested that the experimental variation observed in these young lambs was caused by the high FOR from the rumen in relation to the FOR from the caecum-large intestine.

Animal Nutritional Physiological Phenomena↗
PubMed1989

Kinetic aspects of calcium metabolism in lactating sheep offered herbages with different Ca concentrations and the effect of protein supplementation.

1. Two experiments are described in which kinetic aspects of calcium metabolism were studied in housed lactating sheep consuming different fresh herbage species. The importance of protein supply was also investigated. 2. In Expt. 1, two groups (n 4) were offered, ad lib., a freshly cut ryegrass (Lolium perenne L.)-white clover (Trifolium repens L.) pasture containing 5.48 g Ca/kg dry matter (DM). One group was supplemented daily with 100 g protected casein. A third group (n 4) was offered, ad lib., freshly cut oats-Tama ryegass (Lolium multiflorum L.) herbage which had a lower Ca content of 3.07 g Ca/kg DM. Stable Ca and nitrogen balances were carried out during the first 7 weeks of lactation. At this stage 180 microCi 45Ca were administered for Ca kinetic studies. 3. In Expt 2, eight sheep were offered, ad lib., a fresh ryegrass-white clover pasture, and paired on the basis of their udder size. One member of each pair was supplemented daily with 100 g casein via the abomasum and the amount of milk removed was equalized between pairs. Ca and N balance (12 d) and) and Ca kinetic studies (280 microCi 45Ca) were carried out during weeks 2 and 5 of lactation. 4. Rate of absorption of Ca increased, while rate of Ca secretion in milk and resorption from bone decreased as lactation progressed. Ca balances changed from negative to positive as lactation progressed in sheep offered ryegrass-white clover, but, while improving, were always negative in sheep offered oats-Tama ryegrass. Protein supplementation increased (18%) milk production of the ewes in Expt 1 and their retention of N in Expt 2. 5. The proportion of utilized Ca derived from the diet, as opposed to the skeleton, tended to increase as a result of protein supplementation. 6. Availability of Ca from ryegrass-white clover ranged from 0.19 to 0.32, even though only 50% of the net Ca requirement was derived from the diet. Availability of Ca from the oats-Tama ryegrass diet was similar, though in this case less than 20% of the net Ca requirement was derived from the diet. It was concluded that availability of Ca from forage diets may be lower than previously anticipated. 7. Faecal endogenous loss ranged from 16 to 40 mg Ca/kg body-weight per d, and was similar on both diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1989

Faecal endogenous loss of calcium in young sheep.

1. Two groups of eight 6-7-month-old wether lambs were offered either a frozen ryegrass (Lolium perenne L.)-white clover (Trifolium repens L.) pasture or a ryegrass-white clover hay, containing 12.1 and 6.4 g calcium/kg dry matter (DM) respectively. Within groups the amounts offered to individual sheep ranged from 0.5 to 2.0 times the estimated maintenance energy requirements. 2. A single intravenous injection of 150 microCi 45Ca as CaCl2.2H2O, and stable balances were used to determine absorption, faecal endogenous loss and balance of Ca. 3. Faecal endogenous loss of Ca increased by 1.2 mg/kg body-weight (W) per d with each g/kg W per d increase in DM intake regardless of the diet. At any DM intake the mean faecal endogenous loss was 5.5 mg/kg W per d higher in the sheep offered the frozen herbage diet when compared with those on the hay diet. At any Ca intake the mean faecal endogenous loss was 6.9 mg/kg W higher in sheep offered the hay diet compared with those on the frozen herbage. 4. At feeding levels of about 1.5-2 times the estimated maintenance energy requirement the observed faecal endogenous loss of Ca ranged from 35 to 50 mg/kg W per d, which is two- to threefold greater than the present estimate of the Agricultural Research Council (1980) of 16 mg/kg W per d.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Changes in blood content and histology during growth of antlers in red deer (Cervus elaphus) and their relationship to plasma testosterone levels.

Antlers were removed sequentially from 18 mature red deer stags between 28 and 112 days after casting of the previous hard antlers and the blood volume determined and structure investigated histologically. One antler from each stag was removed during the growth phase, the other at velvet shedding. Antler blood volume increased linearly, with increasing antler weight at a rate of 194 ml/kg between 28 and 91 days after casting but subsequently declined rapidly. A zone of mineralisation occurred between 5 and 10 cm below the antler tip until 91 days but was subsequently markedly reduced in size and replaced by bone. Between 91 and 112 days growth slowed and a rapid increase in formation of compact cortical bone occurred in the periphery of the whole antler. These changes were associated with increasing circulating levels of testosterone.

Animals↗
PubMed1985

Skeletal and blood biochemical characteristics of sheep during growth and breeding: a comparison of flocks with and without broken mouth.

Two-hundred female Scottish Blackface sheep ranging in age from 3 months to 5 1/2 years were used to investigate the relationships between blood biochemical characteristics, skeletal metabolism and dental health on 5 farms, 3 with broken mouth and 2 with no incidence of the disease. Skeletal growth to 6 months of age was faster in lambs from control flocks than in lambs from affected farms although growth thereafter was slower in the control group. A generally lower protein intake on control farms may account for this reduced growth rate. In general, adult dimensions of bones were attained between 14 and 30 months of age but age of maturation varied between bones; tibial endochondral growth ended after 14 to 21 months while the rib still showed evidence of endochondral growth at 70 months of age. This growth was episodic, being maximal during lactation and possible causes are discussed. There was no significant differences in calcium or phosphorus status between control and affected populations, an inadequate phosphorus intake during pregnancy was common to both groups. Lower serum magnesium concentration in affected than in control sheep was a consistent finding and is discussed.

Aging↗
PubMed1984

Pathogenicity of O. circumcincta, O. ostertagi and H. contortus in weanling stag fawns (Cervus elaphus).

Groups of four stag fawns, weighing 51 +/- 0.8 kg, were-infected with 30,000 larvae of one of three nematode parasites: O.circumcincta, O.ostertagia, or H.contortus. A further four remained as control. Individual feed intake, body-weight, faecal egg count and plasma pepsinogen concentration were measured during seven weeks after infection. Only infection with H.contortus caused significant elevation of pepsinogen concentration to 380ml/ L and consistent depression of feed intake (15%). Worm egg counts were below 300 e.p.g. in deer infected with all worm species. It is concluded that while resistance to development of parasites common to other species appears to be high further investigation of the susceptibility of deer to H. contortus infection would be justifiable.

Journal Article↗
PubMed1980

Chronic subclinical ovine fascioliasis: plasma glutamate dehydrogenase, gamma-glutamyl transpeptidase and aspartate aminotransferase activities and their significance as diagnostic aids.

The effect of low grade chronic Fasciola hepatica infection on the concentration of plasma glutamate dehydrogenase (GD), gamma-glutamyl transpeptidase (gamma-GT) and aspartate aminotransferase (AST) was investigated in sheep dosed daily with three (AL3), eight (AL8) or 14 (AL14) metacercariae over 22 weeks or given a single dose of 200 metacercariae. Significant increases in plasma GD activity first occurred after nine, 12 and 23 weeks and in gamma-GT activity after 12, 24 and 32 weeks for groups AL14, AL8 and AL3 respectively. Changes in AST activity were not as clearly related to dose level. In sheep with single infection, both GD and gamma-GT were capable of detecting liver damage resulting from the migration of 10 or more flukes. Plasma GD and gamma-GT activities are more sensitive indicators of liver cell damage in chronic subclinical fascioliasis than AST activity and gamma-GT may be more suitable as a diagnostic aid on account of its greater stability.

Animals↗