Bone mineral density QTL at sexual maturity and end of lay

1. An F₂ cross of a broiler male line and a White Leghorn layer line was used to identify quantitative trait loci (QTL) for bone density at the onset of lay and at the end of the laying period. A total of 686 measures of humeral bone density were available for analysis.

2. There was no evidence for epistasis.

3. Genome-wide significant QTL for bone density at the onset of lay were identified on chromosomes 1 (311?cM) and 8 (2?cM) and on chromosomes 1 (311?cM), 3 (57?cM) and 8 (2?cM) with a covariate for the number of yellow follicles (a proxy for the concentration of circulating oestrogen).

4. Evidence for only 4 chromosome-wide suggestive QTL were detected at the end of lay (72 weeks).

5. Analysis of the combined data confirmed two genome-wide suggestive QTL on chromosome 1 (137 and 266?cM) and on chromosomes 8 (2?cM) and 9 (10?cM) in analyses with or without the covariate.

6. Positive QTL alleles came from the broiler line with the exception of 2 suggestive QTL at the onset of lay on chromosomes 3 and 5 in an analysis with the covariate.

7. In general, QTL acted additively, except that dominant effects were identified for three suggestive QTL at the onset of lay on chromosomes 3 (57 and 187?cM) and 5 (9?cM).

8. The significant QTL in this study were at similar locations to QTL identified in a range of crosses in other publications, suggesting that they are prime candidates for the search for genes and mutations that could be used as selection criteria to improve bone strength and decrease fractures in commercial laying hens.     

Malignant seminoma with metastasis, Sertoli cell tumor, and pheochromocytoma in a spotted dolphin (Stenella frontalis) and malignant seminoma with metastasis in a bottlenose dolphin (Tursiops truncatus)

Seminoma with metastasis was diagnosed in a spotted dolphin (Stenella frontalis) and an Atlantic bottlenose dolphin (Tursiops truncatus). Sertoli cell tumor and pheochromocytoma were also diagnosed in the spotted dolphin. The spotted and bottlenose dolphins were adult males that stranded and died on the coasts of northwest Florida and southeast North Carolina, respectively. Neoplasia is infrequently reported in cetaceans. This is the first report of seminoma, Sertoli cell tumor, and pheochromocytoma in a dolphin, the first report of three distinct neoplasms in a dolphin, and one of the few reports of malignant neoplasia in dolphins.     

Investigation of H7N2 avian influenza outbreaks in two broiler breeder flocks in Pennsylvania, 2001-02

An avian influenza (AI) outbreak occurred in meat-type chickens in central Pennsylvania from December 2001 to January 2002. Two broiler breeder flocks were initially infected almost simultaneously in early December. Avian influenza virus (AIV), H7N2 subtype, was isolated from the two premises in our laboratory. The H7N2 isolates were characterized as a low pathogenic strain at the National Veterinary Services Laboratories based on molecular sequencing of the virus hemagglutinin cleavage site and virus challenge studies in specific-pathogen-free leghorn chickens. However, clinical observations and pathologic findings indicated that this H7N2 virus appeared to be significantly pathogenic in meat-type chickens under field conditions. Follow-up investigation indicated that this H7N2 virus spread rapidly within each flock. Within 7 days of the recognized start of the outbreak, over 90% seroconversion was observed in the birds by the hemagglutination inhibition test. A diagnosis of AI was made within 24 hr of bird submission during this outbreak using a combination of virus detection by a same-day dot-enzyme-linked immunosorbent assay and virus isolation in embryonating chicken eggs. Follow-up investigation revealed that heavy virus shedding (90%-100% of birds shedding AIV) occurred between 4 and 7 days after disease onset, and a few birds (15%) continued to shed virus at 13 days post-disease onset, as detected by virus isolation on tracheal and cloacal swabs. AIV was not detected in or on eggs laid by the breeders during the testing phase of the outbreak. The two flocks were depopulated at 14 days after disease onset, and AIV was not detected on the two premises 23 days after depopulation.     

Fibrosarcoma of the brood pouch in an aquarium-reared lined seahorse (Hippocampus erectus).

An adult, male, captive lined seahorse (Hippocampus erectus) was presented with weight loss, anorexia, and brood pouch distention. Initial treatments included manual expression of the brood pouch followed by saline flushes and enrofloxacin infusions. Radiographs and physical examination identified a nodular swelling in the brood pouch wall. The mass was excised, but the seahorse died. Necropsy and histopathology revealed a malignant mesenchymal tumor with a collagenous stroma, and a brood pouch fibrosarcoma was diagnosed.     

Hypocortisolaemia in a Labrador retriever

A four-year-old Labrador retriever was presented with lethargy and exercise intolerance. Clinical examination was unremarkable. A subnormal Cortisol response to adrenocorticotrophin hormone (ACTH) was demonstrated (plasma Cortisol concentrations before and after administration of ACTH were both below the detection limit of the assay) but plasma aldosterone concentrations were within the normal range. Endogenous plasma ACTH concentrations were high, indicating primary adrenocortical disease. Following glucocorticoid supplementation at a replacement dose (prednisolone 0.1 mg/kg) the dog made a full clinical recovery.     

Effect of post‐mortem temperature on chicken M. pectoralis major: Isometric tension and pH profiles

1. The relationship between isometric tension development and pH, as a function of storage temperature between 0° and 40°C, was examined in chicken M. pectoralis major (PM) muscle during the critical 24 h post‐mortem period.

2. The muscle strips incubated at 0°C developed a peak isometric tension of 53.3 g/cm². This occurred after only 17 min incubation when the pH was 7.02, demonstrating the potential of chicken PM muscle to cold shorten. Peak isometric tension at 5°C was considerably lower than that generated at 0°C. However, as this occurred when the muscle pH was still high (6.70), this also indicated some potential to cold shorten at 5°C.

3. At 10° to 30°C, the muscle strips developed mean peak isometric tensions of 18 g/cm² after 6 h incubation by which time the muscle pH had fallen to 6.00, demonstrating a limited potential to rigor shorten. In contrast, those incubated at 40°C developed a peak tension of 54.5 g cm² after 75 min when the muscle pH was also around 6.00, thus indicating the potential for intensive rigor shortening at this temperature. Incubation temperature and the resultant muscle pH therefore determine the potential of chicken PM muscle to either cold shorten or rigor shorten.

4. Despite the differences found in isometric tension profiles, cooked meat texture after isometric tension measurement was not significantly different at any of the temperatures studied primarily because the muscle strips were essentially prevented from shortening.     

Effect of post‐mortem temperature on chicken M. pectoralis major: Muscle shortening and cooked meat tenderness

1. Muscle shortening, sarcomere lengths and pH values were measured in strips of chicken M. pectoralis major (PM) muscle incubated at different time (0 to 24 h) and temperature (0° to 40°C) combinations immediately after slaughter; their effects on cooking loss and meat tenderness determined.

2. Maximum muscle shortening of 39% and 43% occurred at 0°C and 40°C respectively. At 0°C, most shortening occurred within 90 min postmortem when the pH of the muscle ranged from 7.13 to 6.52. In contrast, at 40°C, most shortening occurred during the development of rigor mortis, between 90 and 380 min post‐mortem, when the muscle pH ranged from 6.16 to 5.89. In a similar manner, minimum sarcomere lengths of 1.38 μm were reached after 90 min at 0°C while more severe sarcomere shortening, to 0.96 μm and 0.86 μm at 30°C and 40°C respectively, was not complete until after 380 min post‐mortem. Between 5°C and 20°C, muscle shortening ranged from 25 to 34% while minimum sarcomere lengths of 1.33 μm were recorded.

3. Cooking losses increased on average from 7 to 16% between 30 and 380 min post‐mortem, with maximum losses of 19% being achieved by the end of the 24‐h incubation period.

4. At 0°C, shear force values increased from 2.94 kg/cm² to 4.34 kg/cm² between 30 and 90 min post‐mortem while the muscle pH was > 6.5. At all other temperatures, increases in shear force values were not detected until 380 min post‐mortem when the muscle pH had fallen to 5.9 and rigor mortis had set in. At all times after 380 min, however, the muscle strips incubated at 0, 5 and 40°C had lower shear values (range 3.17 to 5.49 kg/cm²) than those incubated from 10°C to 30°C (range 5.06 to 7.22 kg/cm²).

5. A significant quadratic relationship was found between the degree of shortening and subsequent cooked meat tenderness, in which peak toughness occurred at 30% shortening. This would suggest that the actual extent of muscle shortening per se has an important role to play in determining the tenderness of chicken post‐mortem. Consequently, with unrestrained chicken muscle, where extensive shortening occurred at 0°C and 40°C (i.e cold‐ and rigor shortening) the cooked meat was more tender than that subjected to intermediate post‐mortem temperature regimens.