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in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Objective

To assess parasite control and weight gain after administration of an ivermectin sustained-release bolus over 135 days to calves grazing in the midwestern United States.

Design

Replicated pasture study.

Animals

56 Bos taurus calves.

Procedure

Calves were matched for body weight and randomly allocated to remain untreated or to receive an ivermectin sustained-release bolus before turnout on day 0. Calves were grazed by treatment group on 8 pastures (4 replicates). Body weights and fecal egg counts were recorded on days −1 and 28, and then at 28-day intervals until day 168.

Results

Parasitism was not clinically evident prior to or during the study. In treated calves, mean fecal egg counts were at or near 0 at all posttreatment evaluations. Although the mean egg count exceeded 20 ova/g only once in control calves, the cumulative egg output was > 42 million/calf. For the treated group, it was < 0.1% of this number. Mean total weight gain was 33.9 kg (74.6 lb) greater for ivermectin-treated calves than for untreated control calves (P < 0.02); a 34% increase.

Clinical Implications

Fecal trichostrongyle eggs from calves can accumulate over a grazing season to provide enormous potential for augmenting pasture infectivity. An ivermectin sustained-release bolus (administered to calves being placed on pasture) controls parasitism, limits pasture infectivity, and can substantially influence growth by limiting the impact of subclinical parasitism. (J Am Vet Med Assoc 1997;211:754–756)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine an optimal window for determining peak flatulence and evaluate the effects of oligosaccharides and supplemental β-mannanase in soybean meal–based diets on nutrient availability and flatulence.

Animals—6 dogs.

Procedures—Dogs were used in a 2 × 3 factorial arrangement of treatments in a 6 × 6 Latin square experiment to evaluate the digestibility, flatulence, and fecal odor metabolites of low-oligosaccharide low-phytate soybean meal (LLM), conventional soybean meal (SBM), and poultry by-product (PBP) meal diets with or without supplemental β-mannanase (5 g/kg).

Results—Enzyme supplementation had no effect on total tract dry matter (DM), nitrogen digestibility, or digestible energy; however, differences between protein sources did exist for total tract DM digestibility and digestible energy. The PBP meal had higher DM digestibility and digestible energy (mean, 0.913 and 4,255 cal/g), compared with soy-based diets (mean, 0.870 and 4,049 cal/g). No differences were detected for any treatment regardless of protein source or addition of supplemental enzyme for any flatulence components analyzed. No differences were detected for all fecal odor metabolites regardless of addition of supplemental enzyme; however, differences between protein sources were detected. The PBP meal had lower concentrations of carboxylic acids and esters and higher concentrations of heterocycles, phenols, thio and sulfides, ketones, alcohols, and indoles than LLM and SBM.

Conclusions and Clinical Relevance—Diets containing < 22.4 g of stachyose/kg and < 2 g of raffinose/kg did not alter digestibility or increase flatulence in dogs.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the effect of high- and lowprotein diets with or without tryptophan supplementation on behavior of dogs with dominance aggression, territorial aggression, and hyperactivity.

Design—Prospective crossover study.

Animals—11 dogs with dominance aggression, 11 dogs with territorial aggression, and 11 dogs with hyperactivity.

Procedure—In each group, 4 diets were fed for 1 week each in random order with a transition period of not < 3 days between each diet. Two diets had low protein content (approximately 18%), and 2 diets had high protein content (approximately 30%). Two of the diets (1 low-protein and 1 high-protein) were supplemented with tryptophan. Owners scored their dog's behavior daily by use of customized behavioral score sheets. Mean weekly values of 5 behavioral measures and serum concentrations of serotonin and tryptophan were determined at the end of each dietary period.

Results—For dominance aggression, behavioral scores were highest in dogs fed unsupplemented high-protein rations. Tryptophan-supplemented low-protein diets were associated with significantly lower behavioral scores than low-protein diets without tryptophan supplements.

Conclusions and Clinical Relevance—For dogs with dominance aggression, the addition of tryptophan to high-protein diets or change to a low-protein diet may reduce aggression. For dogs with territorial aggression, tryptophan supplementation of a low-protein diet may be helpful in reducing aggression. (J Am Vet Med Assoc 2000;217:504–508)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objectives

To determine the efficacy of ivermectin (IVM) and milbemycin oxime (MBO) against induced heartworm infection, where monthly treatment is started 3 or 4 months after infection, and to monitor microfilaremia and antigenemia.

Animals

21 heartworm-naive Beagles.

Procedures

Each of 21 dogs was given 50 infective larvae of Dirofilaria immitis by SC inoculation. One group of 5 dogs served as nonmedicated controls, 2 groups of 5 dogs received IVM at 6 μg/kg of body weight or MBO at 500 μg/kg for 12 months beginning at postinfection (PI) month 4, and 2 groups of 3 dogs received IVM or MBO for 13 months beginning at PI month 3. Blood collected at intervals not >1 month beginning at PI month 4 was examined for microfilariae and antigen. Dogs were euthanatized at PI month 16.

Results

Adult worm counts, relative to controls, were reduced in the 4-month treatment groups by 95.1 (P < 0.01) and 41.4% for IVM and MBO, respectively. The difference between the IVM and MBO groups was significant (P < 0.01). Live worms were found in all MBO-treated (range, 8 to 27) and control dogs (range, 12 to 39) and in 3 of 5 IVM-treated dogs (range, 2 to 4). In the 3-month treatment groups, worm counts were reduced by 97.7 (P < 0.01) and 96.8% (P < 0.01) for IVM and MBO, respectively. Microfilariae were seen in all control dogs and in only 2 of the 16 treated dogs. The antigen response of MBO-treated dogs in the 4-month treatment group was only slightly weaker than that for control dogs. In all other treated dogs, this response was delayed and weaker.

Conclusion

Ivermectin is highly (≥ 95%) and significantly more effective than MBO against induced heartworm infection when 1 year of monthly prophylactic dosing is started 4 months after infection.

Clinical Relevance

In some cases of owner compliance failure, monthly administration of IVM gives a high level of protection against young adult heartworms. (Am J Vet Res1996;57:1189-1192)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the hemodynamic consequences of the coadministration of a continuous rate infusion (CRI) of medetomidine with a fentanyl bolus in dogs.

Animals—12 healthy sexually intact male dogs weighing 30.3 ± 4.2 kg (mean ± SD).

Procedure—Dogs received either fentanyl alone (15.0 µg/kg, IV bolus) or the same dose of fentanyl during an 11-hour CRI of medetomidine (1.5 µg/kg/h, IV). Prior to drug administration, dogs were instrumented for measurement of cardiac output, left atrial pressure, and systemic arterial blood pressures. Additionally, blood samples were collected from the pulmonary artery and left atrium for blood gas analysis.

Results—Medetomidine infusion reduced the cardiac index, heart rate, and O2 delivery while increasing left atrial pressure. Subsequent fentanyl administration further decreased the cardiac index. The PaO2 was not significantly different between the 2 treatment groups; however, fentanyl transiently decreased PaO2 from baseline values in dogs receiving a CRI of medetomidine.

Conclusions and Clinical Relevance—Because of the prolonged hemodynamic changes associated with the CRI of medetomidine, its safety should be further evaluated before being clinically implemented in dogs. (Am J Vet Res 2005;66:1222–1226)

Full access
in American Journal of Veterinary Research