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Biomedical subjects

G Fishwick

Publications and source records attributed to G Fishwick.

48 records · Page 3Linked to original sources
PubMed1992

Pathophysiology of the periparturient egg rise in sheep: a possible role for IgA.

The relationship between anti-parasite IgA antibody levels in plasma and the periparturient egg rise in sheep was investigated. Ostertagia circumcincta larvae (5000 third stage larvae three times weekly) were administered to three groups of seven adult immune ewes from 12 weeks before until three weeks after lambing (group 1) or from six (group 2) or 14 (group 3) weeks before until three weeks before lambing. Seven additional ewes were not challenged (group 4 controls). Ewes in groups 1, 2 and 4 received anthelmintics 14 weeks before lambing. Challenge of the pregnant ewes with O circumcincta larvae resulted in substantial increases in faecal egg counts only during the periparturient period regardless of the larval dosing regimen. Furthermore, the periparturient rise in faecal egg counts was closely associated with a significant increase in anti-parasite IgA antibody levels in plasma. This rise in IgA antibody levels occurred at a time when IgA is transported from the gut to milk during early lactation. It is postulated that this may lead to a temporary reduction in abomasal antibody levels of ewes and hence permit the establishment of larvae and, or, the emergence and development of inhibited larvae and thereby lead to the periparturient rise in faecal egg count.

Animals↗
PubMed1990

Pathophysiology of the periparturient egg rise in sheep: the role of prolactin.

The involvement of prolactin in the periparturient rise in the faecal nematode egg count in sheep was investigated. Ostertagia circumcincta larvae (5000 third stage larvae three times weekly) were administered to adult immune ewes from three weeks before parturition to three weeks afterwards. Ten ewes were injected twice daily with 2-bromo-alpha-ergocryptine (bromocriptine), an antagonist of prolactin secretion, for two weeks starting two days after lambing while 10 ewes remained untreated. Bromocriptine treatment was initiated approximately two weeks pre partum in three other ewes. Plasma pepsinogen concentrations rose significantly by one week after the start of O circumcincta larval challenge in all the ewes but faecal egg counts remained negative until approximately one week post partum. Plasma prolactin concentration was reduced to a very low level in all bromocriptine treated ewes but this did not alter the dynamics of the periparturient rise in faecal egg counts. Neither cell-mediated nor humoral immunity of the ewes, as assessed by their sensitivity to BCG inoculation and by antibody titre raised against horse red blood cells, respectively, were impaired during the rise in faecal egg count, nor were these parameters altered by manipulation of plasma prolactin concentration. Lamb growth rate was not retarded by low plasma prolactin concentration in the bromocriptine treated ewes. These results are not consistent with the generally held hypothesis that elevated plasma prolactin concentration is directly associated with the periparturient rise.

Animals↗
PubMed1988

Effects of trichostrongyle larval challenge on the reproductive performance of immune ewes.

Ostertagia circumcincta larvae were administered to adult immune ewes either during the breeding period or around parturition to investigate whether reproductive performance was affected. Two groups of 25 ewes were given water or 12,000 ostertagia larvae three times weekly for five weeks before and five weeks after breeding to synchronised oestrus. Plasma pepsinogen levels were raised in the larval-challenged ewes during the treatment period but no significant effect of treatment was observed on ovulation rate or plasma progesterone concentration. Neither ewe live-weight nor body condition score differed between groups throughout gestation or for four weeks post partum and there was no effect from larval challenge during the breeding period on lambing rate, lamb birthweight or liveweight at four weeks old. A second experiment involved 20 twin-bearing immune ewes which were administered 17,000 ostertagia larvae three times weekly for three weeks before and three weeks after parturition. Plasma pepsinogen concentration was elevated during the larval challenge period and nematode eggs were detected in the faeces after parturition but there was no effect from treatment either on ewe liveweight and body condition score or on lamb birthweight and lamb liveweight at four weeks old. These results indicate that larval challenge with ostertagia larvae at dose rates comparable to larval intake from heavily contaminated pasture did not affect the general well being and reproductive performance of immune Greyface ewes.

Animals↗
PubMedDate not supplied

Low phosphorus intakes by beef suckler cows in late pregnancy and early lactation.

Two groups each of 10 suckler cows were given a basal diet of oat straw and pressed unmolassed sugar beet pulp for the last 19 weeks of pregnancy and the first 6 weeks of lactation. One group received 0.88 kg extracted soya bean meal (SBM) in pregnancy and 1.03 kg in lactation. The other was given 0.27 kg of a liquid supplement (LS) (containing inter alia urea and phosphoric acid) in pregnancy increasing to 0.33 kg in lactation. Both diets provided about the same amounts of digestible crude protein and about 10 g phosphorus (P) per day in pregnancy and 12 g P per day in lactation. Cows given SBM consumed marginally more straw but there were no differences in total diet digestibility. Cows given LS lost significantly more liveweight but their calves grew equally well. There were indications that cows given LS had slightly higher mean blood inorganic P and lower mean blood calcium (Ca) concentrations. Mean blood inorganic P concentrations were not below 1.4 mmol/l in pregnancy or 1.2 in lactation. There were no signs of reduction in voluntary straw intake or depraved appetite. When transferred to grass with a bull at the end of the experiment all cows were served within 24 days. It is concluded that these amounts of dietary P were adequate over the 25 weeks.

Animal Feed↗