Canine cyclic hematopoiesis: blood gas and 2,3-diphosphoglyceric acid studies

Cyclic hematopoiesis in gray Collies was first described in 1967. These dogs are anemic in comparison with the healthy littermates, and their erythropoiesis is abnormal. Although the basic disorder appears to be an as yet unidentified abnormality of hematopoietic progenitor cells, an inherent difference in responses to blood gas control mechanisms remains as a possible cause. In a study of these mechanisms in dogs with cyclic hematopoiesis, the P50 and 2,3-diphosphoglyceric acid concentrations were increased. Differences in pH, PCO2, PO2, and oxygen saturation were not observed.     

Influence of ambient temperature on prolactin concentrations in serum of Holstein and Brahman x Hereford heifers

Four Holstein and four Brahman x Hereford heifers about 8 mo of age were used in a study to determine whether breed influences the effects of ambient temperature on concentrations' of prolactin in serum. Two heifers of each breed were stanchioned in each of two environmental chambers at 21 C for 7 d, after which chamber temperatures were changed to 7 or 31 C during 6 h. After 5 d at 7, 21 or 31 C, heifers were injected with 60 micrograms thyrotropin-releasing hormone (TRH). A switch-back design was used and each heifer was exposed to all treatments. Concentrations of prolactin in serum of heifers during exposure to 7, 21 or 31 C for 5 d were related to ambient temperature (9.0, 20.9 and 29.5 ng/ml, respectively; P less than .001), but the response was not influenced by breed. Heifers of both breeds responded similarly to treatment with TRH, and prolactin in serum increased (P less than .001) within 5 min from 7.0 +/- 3.2 to 45.7 +/- 8.2 ng/ml in heifers at 7 C, from 13.1 +/- 1.6 to 97.2 +/- 9.6 ng/ml in heifers at 21 C and from 18.2 +/- 3.5 to 96.2 +/- 11.3 ng/ml in heifers at 31 C. We conclude that concentrations of prolactin in serum of heifers are positively associated with ambient temperature and that the effects of temperature on basal and TRH-stimulated concentrations of prolactin do not differ significantly between Holstein and Brahman x Hereford heifers. Thus, differences in tolerance to heat were not related to differences in prolactin secretion.     

Maternal antibody, vaccination and reproductive failure in dogs with parvovirus infection

Summary. The maternal antibody (MAb) titre to canine parvovirus (CPV) was determined on consecutive serums from 39 puppies in 7 litters. Vaccination with inactivated CPV was performed at a variety of ages and the response of the puppies determined. Transfer of MAb was demonstrated in 71% (5/7) of the litters and persisted for up to 10 weeks in some litters. MAb titres of >20 precluded a vaccination response by puppies. Sixty- one per cent (8/13) of puppies responded to vaccination when the MAb titre was <20. However, no anamestic response occurred and in some cases a decrease in antibody titre was observed following a second vaccination. During an outbreak of canine parvovirus enteritis (CPE) in the kennel, 33 puppies developed clinical signs of enteritis. Of these puppies 85% (28) had MAb titres of <80 at the onset of clinical signs. Fifty per cent (4/8) of the puppies which responded to vaccination developed CPE, whereas 100% (5/5) of those that did not respond to vaccination developed CPE.
The results indicate that MAb may persist for up to 10 weeks and puppies with MAb in the titre range >20 to <80 do not respond to vaccination but are still susceptible to infection. It is also apparent that a significant minority of puppies with MAb <20 do not respond to vaccination.
An examination of the breeding records of the kennel for the 7 year period 1973–1981 demonstrated a sudden decrease in reproductive efficiency during and subsequent to 1978. This coincided with the recognition of cases of CPV infection in the kennel. It is suggested that further investigation is required into the possible role of CPV in reproductive failure.
The authors would like to thank H. Findlay, P. Hinchliffe, G. Griffiths and S. MacPhail for technical assistance and Dr G. Wilcox and R. Flower for helpful discussion and advice.     

EFFECT OF STRESS ON STEROID HORMONE LEVELS IN RACEHORSES

SUMMARY Cortisol and testosterone were measured by radioimmunoassay in plasma samples from race horses. None of 6 stressed male horses had Iow cortisol levels but testosterone levels (0.81 ± 0.15 nmol/l) were significantly lower than in healthy horses (1.86 ± 0.31 nmol/l). The conclusion was made that adrenocortical insufficiency is not a common association of stress in race horses. The reduction in testosterone levels is probably a nonspecific response similar to that seen in other species.     

Effects of grain type, roughage level and monensin level on finishing cattle performance

Interactions among grain type (grain sorghum, corn or wheat), roughage level and monensin level were studied in four feedlot trials using pen-fed crossbred yearling cattle. In Trial 1, cattle fed high-moisture corn (HMC) were more efficient (.1537 vs .1406 for gain/feed; P less than .01) than cattle fed dry-rolled grain sorghum (DRGS). As level (0, 3, 6, 9%) of dietary roughage was increased, feed efficiency (gain/feed) decreased (.1566, .1461, .1479, .1382; linear, P less than .01). In Trial 2, a grain type (DRGS; dry-rolled corn, DRC; dry-rolled wheat, DRW) x roughage level interaction was observed for daily gain and feed efficiency. Feed efficiency (gain/feed) was decreased when roughage was added to diets containing DRC (.1608 vs .1750) or DRGS (.1674 vs .1465), but not to the diet containing DRW (.1664 vs .1607). In trial 3, a grain type x roughage level x monensin level interaction (P less than .08) was observed for feed efficiency. The addition of 27.5 mg of monensin per kilogram of the 0% roughage-DRC diet tended to improve feed efficiency (.1633 vs .1531), but the addition of monensin to the 7.5% roughage-DRC diet tended to depress feed efficiency (.1476 vs .1575). The addition of either roughage (.1493 vs .1420) or monensin (.1500 vs .1413) to the DRW diet improved feed efficiency. In Trial 4, cattle fed a combination of 75% DRW and 25% DRC were more efficient (.1618 vs .1591; P less than .06) than cattle fed DRC. As level of roughage (0, 3.75, 7.5%) increased, feed efficiency decreased linearly (.1645, .1599, .1569; P less than .0001). Monensin had no effect on feed efficiency. The value of feeding roughage and monensin was variable both across grain types and within similar grain types.     

Long-term anaesthesia with propofol and alfentanil in the dog and its partial reversal with nalbuphine

Prolonged surgical anaesthesia in the dog was induced with propofol (6.5 ± 1.3 mg/kg) followed by alfentanil (25.5 ± 5 μg/kg) (mean ± 1 sd) and maintained with a continuous infusion of propofol (0.14 to 0.18 mg/kg/min) and alfentanil (2 to 3 μg/kg/min). Neuromuscular blockade was produced with vecuronium (0.1 mg/kg). After induction of anaesthesia with propofol, administration of alfentanil to dogs which had received no pre-anaesthetic medication produced cardiac arrest and apnoea. Administration of atropine intravenously immediately prior to alfentanil prevented these cardiac depressant effects. The cardiac depressant effect of alfentanil was not as severe in a second group of dogs in which anaesthesia was induced with thiopentone. After commencing the continuous infusion anaesthetic regime and establishment of IPPV, blood pressure and heart rate remained stable during the remaining 4 to 6 h period of anaesthesia. Recovery from anaesthesia was smooth and uneventful. The depressant effects of alfentanil on respiration and on consciousness were reversed rapidly by administration of nalbuphine (10 mg total dose). The smooth recovery and the integration of anaesthesia and post operative analgesia attained by the reversal of alfentanil with nalbuphine make this an attractive anaesthetic regime for major surgery in dogs, provided that facilities for IPPV are available.