The development of a transport and enrichment medium for Campylobacter fetus

A transport and enrichment medium was developed for Campylobacter fetus. From inocula of between 10 and 35 organisms the medium was able to support the multiplication of 19 of 21 strains of C. fetus if the medium was incubated immediately after inoculation; when incubation was delayed for 3 days after inoculation, only seven of the 21 strains multiplied. From inocula of 100-350 organisms all 21 strains multiplied following immediate incubation, and 20 of 21 when incubation was delayed for 3 days. From inocula of about 10(4) organisms all strains multiplied following immediate or delayed incubation. The medium restricted the growth of Proteus vulgaris and Pseudomonas aeruginosa.     

Influence of variations in biological and economical parameters on beef production net returns

Net returns were defined as a function of the monetary returns (revenue) generated by the outputs less the monetary costs generated by the variable inputs. Outputs included total weaning weights of steers and heifers, weight of cull cows and weight of open heifers. Inputs included both feed and nonfeed costs. The net returns equation was incorporated as the objective function in a linear programming model. By maximizing the objective function, the breeding system that generated the highest net returns could be identified considering certain resource constraints. Breeding systems included purebred Herefords; small rotational dual purpose (SR), utilizing the breeds Angus, Pinzgauer, Gelbvieh and Tarentaise; large rotational (LR), a three-way rotational cross with the breeds Charolais, Simmental and Maine-Anjou; and Angus-sired terminal (AL) utilizing Angus as the sire breed and LR heifers as the maternal breed. Large rotational generally produced the greatest net returns, followed by SR and either AL or HE, depending on specific resource constraints (limited feed supply or herd size), calving rates, management systems, environment, beef to feed price ratios and purchased or farm-produced (inexpensive) feed utilized. Only under the conditions of a herd size constraint and farm-produced feed did AL exceed SR in net returns. Hereford had larger net returns than LR only when the two breeding systems were evaluated in an environment assumed to be reproductively stressful to LR. Ranking of breeding systems were dependent on specific conditions and indicated that one must consider each resource constraint and environment in which cattle are expected to produce before making breeding system recommendations.     

Establishment of an attenuated strain of bovine respiratory syncytial virus for live virus vaccine

To develop a live virus vaccine for the prevention of bovine respiratory syncytial (BRS) virus infection in calves, an attempt was made to produce an attenuated virus. The RS-52 strain of BRS virus, isolated from the nasal secretions of a naturally infected calf, was subjected to serial passages in adult hamster lung established (HAL) cells at 30 degrees C and the attenuated rs-52 strain as a live virus vaccine was established. The rs-52 strain multiplied better at 30 degrees C than at 34 or 37 degrees C in HAL cells. The differences in the highest virus titers of this strain between the culture temperature of 30 degrees C and that of 34 or 37 degrees C were more than 2.25 log TCID50. Colostrum-deprived newborn calves and 2 approximately 4 months old calves inoculated with the rs-52 strain manifested no abnormal clinical sings at all. However, all inoculated calves produced serum neutralization antibody. When the colostrum-deprived newborn calves immunized with the rs-52 strain were challenged with the virulent NMK7 strain of BRS virus, they exhibited no pyrexia or other abnormal clinical signs at all. An attempt was made to recover the virus from nasal secretions of these calves, but in vain. On the other hand, a nonimmunized control colostrum-deprived newborn calf developed slight fever, mild cough, and slight serous nasal discharge after challenge exposure. The virus was recovered from nasal secretions of this calf. From these results, it was considered that the rs-52 strain could be used as an attenuated live virus vaccine for prevention of BRS virus infection.     

Contributions of ovum cytoplasm, uterine environment and postnatal environment to maternal effects in beef cattle

In the first part of the experiment, embryos of Brown Swiss-Hereford (BS-H) reciprocal crosses were transferred to BS and H recipient cows and embryos of Red Poll-Angus (RP-A) reciprocal crosses were transferred to RP and A recipient cows. Calves resulting from embryo transfers (ET) were weaned early (3 to 5 d). Males were castrated and their growth, feed efficiency and carcass composition were recorded. In the second part of the experiment, matings to produce reciprocal crosses were made by natural service (NS) between BS and H and between RP and A. Some of the offspring were weaned at 3 to 5 d; the remainder nursed their dams to an age of 150 to 180 d. Growth after 200 d, feed efficiency and carcass data were recorded on steers. Females produced in both parts of the experiment were reared for breeding, and post-200-d growth and age at puberty were recorded. Neither breed of recipient (uterine influence) nor breed of donor (cytoplasmic influence) had important effects on growth or carcass traits. Large differences were observed for most growth and carcass traits between offspring that were weaned early and those that nursed their dams. Effects of early weaning were greater in progeny of Brown Swiss and Red Poll dams than in progeny of Angus and Hereford dams. Prenatal maternal influences (e.g., ovum cytoplasm and uterine influence) are relatively small in comparison with postnatal maternal influences in contributing to maternal effects in beef cattle.     

The seborrheic disease complex. An approach to underlying causes and therapies

Seborrhea is a multifaceted disease, and it is a common presentation in the small animal practice setting. This article addresses the considerations to be aware of in approaching the diagnosis of this complex entity. Emphasis is placed on recent advances of diseases that cause seborrhea and on appropriate therapy. A simplified practical approach to topical antiseborrheic shampoo therapy is presented.     

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.     

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.     

The pharmacokinetics and tissue levels of polymyxin B, colistin and gentamicin in calves

Following a single intravenous injection of polymyxin B, colistin (5 mg/kg, each) and gentamicin (3 mg/kg) to calves, the decline in serum antibiotic concentration generally suggested a three-compartment (open system) pharmacokinetic model. Tissue binding is a dominant factor in the distribution and elimination kinetics of the drugs. Less than 65% of the dose of polymyxin B and colistin was recovered in the urine during 48 h after treatment. Concentrations of nonbound polymyxin B and colistin in the kidney, liver, lung, heart, and skeletal muscles were similar to total (free and bound) serum drug levels, but considerably higher concentrations were found, in bound form, in chloroform-ethanol extracts of these organs.
At 24 h after treatment, more than 50% of the doses of polymyxin B and colistin were present bound to the tissues; the largest amount was in the skeletal muscles. Gentamicin was concentrated in the kidney, predominantly in the free form. At 48 h after treatment the amount of gentamicin in the kidney was 6.3% of the administered dose, being more than five times greater than the corresponding amounts of polymyxin B and colistin.
The extent of tissue uptake of polymyxin B and colistin limits the usefulness of kinetic values, which are derived from the analysis of serum drug levels, for the purpose of designing dosage schedules. The strong affinity of the polymyxins to the muscle tissue, and gentamicin to the kidney, can result in drug residues persisting in the body for several weeks.     

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.