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2. With the pheasant as sire, fertility was 7.lb6%, but with the fowl it was 19.lb5%; hatchability of fertile eggs, however, was similar, 42% and 41% respectively.
3. Only one exencephalic hybrid was obtained when the sire was the pheasant but 70 were noted when the fowl was sire. The incidence of this malformation in hatched chicks was 12 times more in crosses with the fowl as sire than in the reverse cross.
4. The frequency of exencephaly was greater with Rhode Island Red, Barred Leghorn or White Leghorn roosters than with Columbian Rock roosters. 相似文献
2. Both cephalosporins and all the nine penicillins tested were active.
3. Of six aminoglycosides, streptomycin and gentamicin had the greatest activity and neomycin had none.
4. Growth rate was significantly improved by clindamycin, lincomycin, vancomycin, spectinomycin, rifampicin, oxytetracycline, chlortetracycline, erythromycin, tylosin, flavomycin, virginiamycin and zinc bacitracin. Chloramphenicol and nalidixic acid were inactive. Polymixin B, novo‐biocin, cycloserine, phosphonomycin, and sodium fusidate had little activity. Fusidic acid promoted growth at 250 mg/kg diet.
5. Trimethoprim was inactive alone and in combination with sulpha‐diazine. Of seven 5‐nitroimidazoles, only dimetridazole and metronidazole showed slight activity. Of the six 5‐nitrofurans, only nitrovin, the standard reference substance used, promoted growth.
6. Caprylohydroxamic acid, a urease inhibitor, had no beneficial effect on growth rate or on the efficiency of food conversion.
7. The growth‐promoting properties of the various substances could not be related with their known antimicrobial and absorption characteristics in mammals. 相似文献
2. The difference in growth‐promoting activity between streptomycin, which was active, and kanamycin which was not, was not related to their effects on the flora adhering to the wall of the crop, jejunum or ileum, to their relative toxicity to the chick nor to differences in their stability in the diet.
3. When low concentrations ofkanamycin or streptomycin were given, the antibiotic was concentrated in the caecal contents. In contrast, penicillin was undetectable in the caeca of birds given high concentrations of benzyl penicillin.
4. In chicks given benzyl penicillin, the numbers of Streptococcus faecium increased at the expense of Strep, faecalis. This probably resulted from changes in the crop flora.
5. Birds given high dietary concentrations of benzyl penicillin showed improved weight gains, in spite of increased numbers of Escherichia coli in the small intestine. 相似文献
2. Birds in conventional deep cages were more active than those in shallow cages in each of four different periods of day. Activity reached a peak between 11.00 and 13.00 h irrespective of cage shape.
3. Mean feeding activity was greater in the shallow (45.6%) than in the conventional deep cages (39.9%).
4. Mean feeding activity was greater in birds fed ad libitum (43.3%) than in those fed on a restricted diet (40.4%).
5. Although restricted birds in shallow cages showed more feeding activity than those in conventional deep cages they consumed less food (56% against 67%) in the 7 h between supply of their daily ration and the onset of the dark period.
6. Feather damage was greater in the conventional deep cages than in the shallow cages.
7. The more efficient utilisation of food by hens in shallow cages is probably due largely to three factors: reduced levels of motor activity and general disturbance, a more leisurely eating pattern and better feather cover. 相似文献
2. Liver fat, carcass fat, liver weight and body weight increased markedly at the onset of sexual maturity.
3. Within the liver, the protein to DNA ratio did not alter significantly during development; glycogen was not consistently depleted by egg production.
4. Liver fat content was significantly correlated with carcass fat, liver weight and DNA concentration, and plasma total lipid and cholesterol, independent of stage of development; with body weight, liver protein, moisture, and protein to DNA ratio, excluding the period prior to commencement of sexual maturation; and with plasma phospholipid during lay.
5. Obesity was a feature of faster growing fowls which matured earlier, consumed more, utilised food less efficiently for egg production and produced fewer saleable eggs. 相似文献