The cardiac conducting system of the fowl.

Twenty-four hearts of Brown Leghorn ranging in age from newly hatched to adult were investigated histologically to elucidate the topographical disposition of the entire cardiac conducting system. Through this study, the bird's heart was found to have the same specialized conducting system as that of mammals. Moreover, in addition to this system, the nodus truncobulbaris and the fasciculus truncobulbaris were reported in detail, and the anulus atrio-ventricularis dexter was confirmed. These peculiar nodes and bundles of the bird's heart are discussed in comparison with the mammalian cardiac conducting system.     

Studies on the isthmus region of the somestic fowl.

The isthmus extends from the aglandular zone, which delimits it from the magnum, to the tubular shell gland, which to the naked eye is marked by a distinct colour change from off-white to brown. 2. The surface epithelium comprises three cell types, ciliated, non-ciliated and mitochondrial, of which only the non-ciliated cells contribute towards the carbohydrate moiety of the shell membranes. 3. The gland cells are distinctive, containing granules of variable electron density, variations also occurring within individual granules. 4. Although two types of gland cell have been observed, they may merely represent different phases of development. 5. In the type 1 cell, the rough endoplasmic reticulum and Golgi complex are typical of the normal protein secreting cell; in the type 2 cell the RER is sparse, dilated and filled with intracisternal granules while the Golgi complex is likewise distended.     

The adrenal cortico-medullary ratio in the fowl.

1. A new integrating method of assessing the proportions of cortical and medullary tissue in the avian adrenal gland is described and statistically evaluated. 2. It is shown that a single "central" section of the adrenal gland will suffice to obtain accurate results. 3. Each section was projected on to a grid of about 2500 intersection points and the ratio of points falling on cortical or medullary tissue was determined. 4. Applications of this method to normal fowls showed that there were significant breed, sex and, particularly, age differences in the cortico-medullary ratio of the fowl's adrenal glands.     

Stressor effects of handling on the immature fowl.

Chicks were handled for 5 min twice daily for five consecutive days per week over a three-week period. The control birds were not handled once they had been allotted to their brooders. The growth rate of the treated birds was significantly decreased. There was no adrenal hypertrophy; the concentration, but not the content, of adrenal cholesterol was significantly increased. Plasma glucose, FFA and cholesterol concentrations were similar in the groups at the end of the experiment. The lipolytic response of the handled birds to a further stimulus of handling was significantly greater than that of unhandled birds experiencing novel handling stimulus. There was also a significant decrease in the concentration of corticosterone in the plasma of the handled birds but not in the unhandled group. There was thus no evidence of habituation.     

Dietary aureomycin and the response of the fowl to stressors.

1. Conventional or gnotobiotic chicks, when injected from 1 d to 3 weeks of age with adrenocorticotrophic hormone (120IU/kg, three times weekly), showed a depressed growth rate, adrenal hypertrophy and depletion of cholesterol form the adrenal glands. 2. Feeding a diet supplemented with aureomycin (10 mg/kg) did not have any consistent ameliorating effect on the response of the stressed bird as judged by the above parameters. 3. It was found that treating germfree chicks with five daily injections of sterile milk on days 3 to 7 did not depress growth rate at any time, nor could differences in adrenal size or cholesterol stores be detected at the end of the 21-d experimental period. The responses were not modified by feeding an aureomycin-supplemented diet.     

Analysis of growth curves of fowl. I. Chickens.

1. The Richards function was used to describe the growth curves (n = 989) of 9 broiler lines. Chickens were fed ad libitum and body weight was recorded every second week from hatching to 26 weeks of age. 2. The accuracy of curve fit measured by the coefficient of determination (R2) was better for males than for females (0.9986-0.9995 vs 0.9972-0.9988, respectively). 3. The estimation of the asymptotic final weight (A) for different lines enabled the degree of maturity (ut = yt/A) to be determined at any fixed point of the curve. At the age of 7 weeks this had a value of 0.318-0.369 for cockerels and 0.325-0.377 for pullets and represented the slaughter maturity of individual lines. The ratio of inflection/asymptotic weight (y+/A = 0.370-0.388) indicated that in some cases chicken growth can be described approximately by the Gompertz function (y+/A = 0.368). 4. It was found that the age at the inflection point of curves (t+ 48.2-55.7 d for cockerels and t+ = 47.8-52.8 d for pullets) roughly corresponds to the slaughter age of the chickens. 5. The interline differences in the parameters of maturation rate for weight (y+/A, k, t+, u7) are low in comparison with the differences in body weight (A, y+, y7) and absolute growth rate (v, v+). 6. The intragroup phenotypic correlation among growth parameters and the importance of the mathematical models are discussed.     

Analysis of growth curves of fowl. II. Ducks.

1. Growth curves of nine selected lines and one random-bred control population (in total, n = 1070) were evaluated by the Richards function. The ducks were weighed at 7-d intervals and, after the tenth week, every second week (up to 18 weeks). Food and water were supplied ad libitum. 2. The predicted curves closely fitted the weight data points (R2 = 0.9991-0.9997). 3. The ducks are characterized by early maturity rate. The peak of the absolute growth rate (the inflection point of the curve) occurred at 24.1-27.6 d of age (t+). A higher ratio of the inflection to the asymptotic weights (y+/A = 0.380-0.424) was found in comparison to those from the Gompertz-type function of growth (y+/A = 0.368). 4. In the selected lines the degree of maturity at a slaughter age of 7 weeks (u7 = y7/A) ranged from 0.784 to 0.835 for males and from 0.819 to 0.889 for females. 5. Ducks within the non-selected control line had a significantly lower maturing rate than the selected lines. 6. Sexual dimorphism was recorded for all growth parameters analysed. Females have faster maturation rate than males (higher values of y+/A, u7, k and a shorter auto-acceleration phase of growth). 7. High interline differences were found for body weight (A, y+, y7) and for absolute growth rate (v, v+) and smaller ones for parameters of the maturation rate (y+/A, u7, k and t+). 8. The intragroup phenotype correlation between growth parameters and the use of weight data only up to 7 weeks of age for the estimation of parameters of the Richards function are discussed.     

Analysis of growth curves of fowl. III. Geese

1. Growth curves of two lines (S,D) and their reciprocal hybrids (in total,, n = 344) were evaluated by the Richards function. Geese were weighed at 7 d intervals to the ninth week, and then at 92, 154, 192 and 217 d of age. Food and water were supplied ad libitum.

2. The accuracy of curve fit measured by the coefficient of determination (R ²) for different genetic groups ranged from 0.9840 to 0.9918. The highest percentage deviations between observed and estimated live weights were recorded at hatching (on average 15.1%), while at the others points of curve they were significantly lower (from 0.6 to 6.8%).

3. The geese are characterised by an early maturing rate. The peak of the absolute growth rate (the inflection point of the curve) occurred at 18.7 to 23.5 d of age (t ⁺). The degree of maturity at a slaughter age of 63 d (u ₆₃ =y ₆₃/A) ranged from 0.69 to 0.76. Fitting the inflection point at the beginning of the linear growth phase significantly affects the maturing rate (k) and the ratio between the inflection (j ⁺ ) and the asymptotic (A) weights. The values of these correlated parameters were very low (j ⁺/A = 0.233 to 0.294, k= 0.0281 to 0.0373 ln0/d).

4. The live weights of geese from 28 d of age and the parameters of the Richards function were significantly higher (P<0.05, P<0.01) in the sire line (S) than in the dam line (D). A low. negative heterosis was observed at all points of the growth curves (— 0.01 to — 9.7%). The results indicated the effect of sex‐linked growth genes.

5. The phenotypic correlations between parameters of the Richards function within genetic groups are discussed.     

The localisation of beta-N-acetyl-glucosaminidase in the oviduct of the domestic fowl.

1. Beta-N-acetylglucosaminidase [EC 3.2.1.30] activity in the oviduct of the domestic fowl has been studied using biochemical and histochemical methods. 2. The principal source of the enzyme was the isthmus, where the enzyme was localised within the less dense region of the dual density granules which characterise this portion of the oviduct.     

Application of the polymerase chain reaction to detect fowl adenoviruses.

The possibility of using the polymerase chain reaction (PCR) for the detection of fowl adenoviruses (FAdV) was tested. The optimal reaction parameters were evaluated and defined for purified genomic DNA of type 8 fowl adenovirus (FAdV-8), and then the same conditions were applied for nucleic acid extracted from infected cells. One hundred picograms of purified viral DNA, or 250 FAdV-8-infected cells, were detected by ethidium bromide staining of the PCR products in agarose gels. The sensitivity was increased to 10 pg purified viral DNA, or 25 infected cells, when the PCR products were hybridized with a specific labeled probe. Several field isolates of FAdV and the CELO virus (FAdV serotype 1) could be amplified by the same primers and conditions, but the size of the amplicons was smaller than that for the FAdV-8 PCR product. Other avian viruses and uninfected cell cultures tested negative.