Effect of antibiotic growth promoters on broiler performance, intestinal growth parameters, and quantitative morphology.

The effects of addition of bacitracin methylene disalicylate (BMD) or virginiamycin (VM) to a corn-soybean meal diet on broiler performance and gastrointestinal tract (GIT) growth parameters and morphology were studied at various ages during growth and finishing. Male and female birds were killed at 1, 3, 5, or 7 wk of age for gross and histologic examination of the duodenum and ileum. Feeding either antibiotic increased BW and decreased intestinal length and weight at all times compared with control birds. However, intestinal length and weight decreases were greater in birds fed VM than BMD at 1 and 3 wk of age. The only change found in the duodenum resulting from dietary treatment was an increase in the number of villi per unit length in birds given VM but not BMD or control. In the ileum, the muscularis mucosa was thinner in birds given VM than in those fed the control diet. Chicks supplemented with VM had a smaller total villus area and shorter villus height and crypt depth in the ileum than birds fed the control diet or BMD. Physical changes in the intestine of birds given either antibiotic growth promoter, although not the same, resulted in improved performance.

Effect of dietary zinc source and method of oral administration on performance and tissue trace mineral concentration of broiler chicks.

Two experiments were conducted with chicks to examine the effect of high dietary levels of soluble sources of Zn on tissue Zn, Cu, and Fe concentrations as influenced by two methods of oral Zn administration from 14 to 21 d of age. Treatments included the basal diet (62 ppm Zn), basal diet supplemented with 1,000 ppm Zn from Zn sulfate, acetate, or chloride fed continuously, or basal diet plus crop intubation with a single oral dose of water (control) or 1,000 ppm Zn dietary equivalent from the sources based on feed intake from the previous day. In Exp. 2, crop-intubated doses were administered daily from 14 to 21 d of age. In Exp. 1, chicks given Zn by gavage decreased (P < .0001) feed intake at 24 h after oral dose compared with chicks fed either the control or high-Zn diets. After the gavage dosing stopped, feed intake was similar among treatments. Bone Zn was increased (P < .0001) by Zn source and was greater at 24 than at 168 h after dosing by gavage. In chicks given a single gavage dose of Zn, liver and kidney Zn measured at 24 h after oral dosing was greater (P < .0001) than at 168 h. In birds given a single oral dose of Zn, time x Zn source interactions were observed in pancreas (P < .0001), mucosal cells (P < .01), and remaining intestinal tract segments (P < .001). In Exp. 2, greater bone, pancreas, kidney (P < .0001), and liver (P < .001) Zn accumulations were observed in chicks given daily gavage doses of Zn compared with those fed Zn in diets. Zinc from the four sources was absorbed and stored in tissues to a similar extent.

Response of broiler breeder females to feed restriction below recommended levels. 3. Characterizing the onset of sexual maturity.

The objective of this study was to characterize how the physical attributes associated with sexual maturity would be affected by feed allocation as female broiler breeders passed through the pullet-layer transition period. Treatments consisted of five feeding programs, or body weight goals, during the period of 0 to 20 wk of age. Those were 8% above breeder standard, standard (primary breeder recommended body weights), and 8, 16, and 24% below standard. The characteristics measured included body and fat pad weights, pubic spread, comb development, head score (comb and wattle appearance), shank length, total plasma lipid concentration, ovary weight, oviduct weight, bursa of Fabricius weight, and age at sexual maturity. The generalized effect of increased severity of the feed restriction programs was to delay the birds' development without altering their ultimate physiological values. The exceptions to this were relative body weight and shank length after maturity, which were reduced in the most severely restricted birds. Measurements of pubic spread and comb growth and subjective scores of head appearance would be useful and easily obtained information when estimating the progression of a flock toward sexual maturity.

Subclinical infectious bursal disease in an integrated broiler production operation.

A field study was designed to determine the prevalence of subclinical infectious bursal disease (IBD) in broiler chickens from a commercial poultry company. Bursae of Fabricius (BF) from two vaccinated and three nonvaccinated broiler flocks were evaluated histologically, and antibody profiles of these broiler and matched parent breeder flocks were established. Lesions of IBD, including lymphoid necrosis, stromal edema, and infiltrates of heterophils and macrophages, were first detected in BF at 24 days of age in both vaccinated and nonvaccinated chickens. At 41 days, all BF had lesions characteristic of IBD, including severe lymphoid depletion, proliferation of epithelial cells, and mild fibroplasia. Although mean maternal antibody levels (measured by enzyme-linked immunosorbent assay) in broilers were apparently protective through day 12, IBD antibodies decreased to nonprotective levels (below 1,000) by day 16 or 20. Titers began to increase by day 28 or 32 because of field exposure. Sentinel birds, placed with broiler flocks, also developed IBD antibody titers. Broiler breeders had low and nonuniform antibody titers. Prevalence of field IBD exposure was high, and existing vaccination programs were not effective.

Detection of antibodies to Mycoplasma gallisepticum in egg yolk versus serum samples.

Serum (n = 1,636) and egg yolk (n = 802) samples collected from hens on four commercial egg farms in Florida were tested for the presence of specific antibodies to Mycoplasma gallisepticum in a commercially available enzyme-linked immunosorbent assay. No significant differences were noted between serum and egg yolk samples with respect to distribution of positive, suspect, and negative test results or for the mean sample/positive control ratio values of positive, suspect, and negative test results. A linear relationship between the distribution of positive and negative results and the age of the birds was observed for results obtained with both serum and egg yolk samples. On the basis of the results of this study, egg yolk samples can be used in lieu of serum samples to screen flocks for antibodies to Mycoplasma gallisepticum.

Mycoplasma gallisepticum as a model to assess efficacy of inhalant therapy in budgerigars (Melopsittacus undulatus).

One hundred budgerigars (Melopsittacus undulatus) were infected in the nares (0.02 ml/naris), eye (0.02 ml/eye), and throat (0.2 ml) with Mycoplasma gallisepticum (MG) R strain (3.175 x 10(7) colony-forming units/ml). Fifty birds were treated with sterile broth and served as the controls; 25 of those were exposed to an inhalant, and the others were not treated. Infected birds were divided into four groups; 1) no treatment, 2) penicillin in drinking water, 3) inhalant, 4) both penicillin and inhalant. At days 3, 7, 10, 14, and 21 postinfection (PI), birds were assessed for clinical signs of disease. Five birds in each group were euthanatized at each interval PI; quantitative cultures were performed on lavages from the nares and trachea and on throat swabs; tracheas and air sacs were examined histopathologically. No clinical signs, lesions, or cultural isolations occurred in any control birds. All infected birds developed clinical signs and lesions of the trachea and air sac, but none died. The most severe clinical signs were seen in birds that were infected with MG and received no other intervention or birds that received penicillin in conjunction with infection. Increased respiratory tract lesions were associated with penicillin treatment; aerosol therapy resulted in fewer lesions.

Histomoniasis in Leghorn pullets on a Florida farm.

Recurrent outbreaks of histomoniasis in flocks of 4-to-6-week-old white leghorn pullets is reported. In a typical outbreak, 5% of the pullets were stunted and listless with unkempt feathers. Mortality ranged from 2 to 3%, and the cull rate was approximately 2%. Ceca of affected chickens contained caseous cores. Histological examination of the ceca revealed fibrinonecrotic ulcerative granulomatous typhlitis associated with numerous histomonad trophozoites in the cecal wall. The outbreaks of histomoniasis were associated with heavy parasitism of pullets by Heterakis gallinarum. Litter had not been completely removed from the houses for the past 10 years, providing a constant source of Histomonas-infected larvated Heterakis ova.

Mycobacterium infection in a gray-cheeked parakeet.

A gray-cheeked parakeet, approximately 3 years of age, was submitted for necropsy. Clinical signs included diarrhea, decreased feed consumption, fluffing of feathers, shivering, weight loss, and limping. Necropsy revealed enlargement and pale discoloration of the spleen and intestines. The liver contained multifocal pale foci. Granulomas, some of which had necrotic centers, were present along the subserosa of the intestinal tract. Microscopic examination revealed diffuse granulomatous splenitis, enteritis, and multifocal granulomatous hepatitis. Numerous acid-fast bacteria were demonstrated in the spleen, liver, and intestine.

Pathogenesis of H13 nephropathogenic infectious bronchitis virus.

A nephropathogenic Massachusetts strain of infectious bronchitis virus (IBV) designated H13-IBV was isolated from the kidneys of commercial broilers. H13-IBV caused respiratory distress, depression, and diarrhea in specific-pathogen-free chickens. Gross renal lesions included pale coloration, swelling, and urate deposition. Histologic renal changes were interstitial mononuclear cell infiltration and degeneration and necrosis of tubular epithelial cells. Lesions in respiratory tissues included thickening and edema of the air sacs, congestion of the tracheal mucosa, and frothy serous exudate. Histologic tracheal lesions were deciliation, mucous gland distortion, inflammatory cell infiltration, and squamous metaplasia. Clinically, H13-IBV was highly pathogenic in birds infected at 1 day of age and mildly pathogenic in birds infected at 4 weeks of age. Kidney lesions were of marked severity only in birds infected at 1 day of age. Tracheal lesions were similar in severity in both age groups.

Comparisons of the genomic RNA of Arkansas DPI embryonic passages 10 and 100, Australian T, and Massachusetts 41 strains of infectious bronchitis virus.

The genomic ribonucleic acid (RNA) of Arkansas DPI at embryonic passages 10 and 100, Australian T, and Massachusetts 41 strains of infectious bronchitis virus (IBV) were compared using two-dimensional, 32PpCp-labeled oligonucleotide fingerprinting. The Arkansas DPI strain embryonic passage 10 was pathogenic for chickens and had one oligonucleotide not present in the attenuated passage 100. The remaining Arkansas DPI oligonucleotides had identical electrophoretic mobility. The fingerprint patterns of the Australian T, Massachusetts 41, and Arkansas DPI IBV genomes were dissimilar, thus indicating they were genetically distinct. The distinctive fingerprint patterns of these virus strains, all identified as IBV by other criteria, indicate considerable genomic variation. Fingerprinting is reliable and sensitive, and should be used in combination with other characterization methods for identifying and differentiating IBV strains.

An outbreak of nephropathogenic H13 infectious bronchitis in commercial broilers.

A nephropathogenic Massachusetts strain of infectious bronchitis virus, designated H13-IB virus, was isolated from the kidneys of broilers in a commercial flock. Respiratory distress, diarrhea, depression, and high mortality were present. Gross renal lesions consisted of pale coloration, mottling, urate deposition, and swelling. The trachea contained a serous to catarrhal exudate. Microscopically, renal changes were primarily associated with the medullary region. Lesions included an interstitial mononuclear cell infiltration, urate deposition, edema, and degenerative and necrotic tubular changes. Tracheal changes included marked thickening of the mucosa, desquamation of ciliated and glandular epithelia and replacement with a stratified undifferentiated epithelium, and inflammatory cell infiltration.

Relationship between delayed onset of egg production and involution of the bursa of Fabricius in White Leghorn chickens.

The relationship between delayed onset of oviposition and involution of the bursa of Fabricius is described. Chickens studied were 26 weeks of age and had not come into production. The bursae of nonlaying chickens were compared with those of age-matched chickens that had laid the first egg 1, 9 to 11, or 24 days before. The bursae from the nonlaying chickens were similar in weight and morphology to the functional bursae of immature pullets. Bursae of laying chickens, even on the day of the first egg, were markedly involuted. Age of the chicken was not a factor in determining bursal involution. The onset of egg production was directly related to bursal involution.

Comparisons of the structural proteins of avian infectious bronchitis virus as determined by western blot analysis.

The antigenic diversity of ten strains of avian infectious bronchitis virus (IBV) was examined by Western blot analyses using polyclonal antisera specific for the Massachusetts 41 (M41), Gray, Arkansas DPI (Ark DPI), Connecticut (Conn) and Australian T (Aust T) serotypes. Although antigenic variation was found in all three structural viral proteins, the matrix protein appeared to be antigenically the most highly variable. Four distinct antigenic groups, which did not correspond to virulence or pathotype, could be defined according to the variations observed in the matrix protein. Somewhat less variation was seen in the spike polypeptide. The only variation in the nucleocapsid protein was indicated by the lack of a detectable reaction between the Aust T antiserum and the Ark DPI nucleocapsid protein. Antisera made against M41 had the broadest reactivity while antisera against Aust T, the only strain tested which was exotic to the U.S.A., had the greatest specificity.