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In mid-2000, a broiler chicken company in Alabama experienced high early mortality rates in chicks from two different hatcheries. Five isolates of Pseudomonas aeruginosa, obtained from these contaminated hatcheries and resulting broiler chicks with omphalitis, were selected to determine virulence of the bacteria. One-day-old specific-pathogen-free white leghorn chicks were placed into positive pressure isolation units (10 chicks per unit); feed and water were provided ad libitum. The five isolates of P. aeruginosa (1 x 10(1) or 1 x 10(1) colony-forming units/bird) were used to challenge two replicates of 10 chicks via yolk sac inoculation. Two control groups were injected with 0.1 ml of phosphate-buffered saline, and two groups received no treatment. Mortality was recorded daily, and the chicks that died were necropsied and liver and yolk sacs were cultured. After 14 days, the remaining chickens were euthanatized and necropsied. Bacterial isolates retrieved from liver and yolk sacs were identified by the API 20 NE typing system to confirm that they were the same as the challenge isolate. Virulence varied greatly among the isolates, resulting in mortality rates from 0 to 90%. The challenge isolates produced different and often distinctive postmortem lesion patterns. Antibiotic sensitivity tests showed that all five isolates were resistant to sulfisoxazole, ceftiofur, penicillin, lincomycin, bacitracin, oxytetracycline, erythromycin, naladixic acid, and tetracycline. The isolates varied in sensitivity to other antibiotics, but all isolates were sensitive to gentamicin.

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This study has established baseline information on the age, breed, gender and nutrition of a large population of working farm dogs in New Zealand. Current feeding practices employed by owners include offering a substantial amount of homekill to their animals. Homekill may be deficient or marginal in vitamins and minerals, therefore opportunities could exist to improve the diets and therefore the longevity and performance of these dogs.

There has been an increase in vitamin A fortification of livestock feeds resulting in increased residual vitamin A in organ meats, which are often used in canned dog foods. The effect on bone density of feeding various concentrations of vitamin A in a canned dog food product was investigated. Thirty-two random-source dogs were assigned to four treatments in a randomized complete block design. The diets contained 15,000, 50,000, 116,000, or 225,000 IU vitamin A/1,000 kcal ME. Diets were fed up to 1 yr. Computed tomography was used to determine bone density of the right tibia at 0, 3, 6, 9, and 12 mo. Computed tomography is a more sensitive technique for determining bone density in vivo than conventional x-rays. There were no differences (P > .10) in tibia bone or marrow density in any of the dogs fed the various concentrations of vitamin A. There was no interaction of time x diet on bone density (P > .05) or bone marrow density (P > .05). In addition, there were no changes in serum alkaline phosphatase, calcium, or phosphorus. These results indicate that concentrations of vitamin A three times the recommended maximum safe amount (71,429 IU/1,000 kcal ME) are not detrimental to normal bone health in dogs. Therefore, these data support the hypothesis that canines are less sensitive to excess vitamin A in the diet than some other mammals.

A study was conducted to determine the riboflavin requirement of adult dogs at maintenance. Twenty adult mixed breed dogs were fed a semipurified meal with one of five riboflavin concentrations: Diet 1, 1.7 mg/kg; Diet 2, 2.7 mg/kg; Diet 3, 3.7 mg/kg; Diet 4, 4.7 mg/kg; and Diet 5, 5.7 mg/kg. The erythrocyte glutathione reductase activity coefficient (EGRAC) was used to determine biochemical riboflavin deficiency. Dogs fed Diet 1 had a greater (P < 0.05) EGRAC (1.24) on d 56 of the trial compared with that of dogs fed Diet 5 (1.11), indicating marginal riboflavin deficiency in dogs fed Diet 1. On d 84 the mean EGRAC for dogs fed Diet 1 (1.36) was different from EGRAC obtained for dogs fed the other diets (1.19, P < 0.05). The difference in mean EGRAC was still present of d 112 (1.59 vs. 1.27; P< 0.01). There was no difference in d 112 mean EGRAC for dogs fed Diets 2, 3, 4 and 5 (P < 0.05). The broken line requirement estimate for the adult dog at maintenance was determined to be 66.8 microgram riboflavin x kg body wt(-1) x d(-1) using the d 112 EGRAC as the basis for assessing biochemical riboflavin deficiency.