2. The tendency was for the proteolytic activity to be increased and the amylase activity to be decreased in conventional chicks. These differences were statistically significant in the caecum.
3. All of the additional proteolytic activity detectable in the caecum of conventional chicks was inhibited by soyabean trypsin inhibitor. However, the increased activity was not detectable in the small intestine and was, therefore, not due to pancreatic trypsin.
4. Attempts to demonstrate in vitro bacterial production of a trypsin‐like enzyme were unsuccessful. 相似文献
2. Some of these embryos were injected with primordial germ cells (PGCs) after 55 h of incubation to attempt to repopulate the gonads.
3. Primordial germ cells transfected with a defective retrovirus containing the reporter gene lac Z were shown to settle in these sterilised gonads.
4. Quantitative histology of 6‐d embryos showed that busulphan produced 75% sterilisation but that PGCs could repopulate these gonads.
5. The technique of producing such germ line chimaeras is of value in studying cell kinetics, gonad differentiation and the production of transgenics. 相似文献
2. A panel of 180 MAbs was generated, from which 14 were chosen for their specificity.
3. These MAbs were characterised immunohistologically on frozen sections of embryonic, newly‐hatched and adult, male and female, left gonads.
4. Three of these MAbs are described: AGC5, AGC7, and AGC13 which recognise respectively germinal epithelial cells, supporting cells and germ cells.
5. These MAbs may be useful in following the developmental pathways in the chicken gonad and analysing the interactive role(s) taking place between gonadal stromal cells and primordial germ cells. 相似文献
2. Higher rates of fertility and hatchability of Japanese quail eggs were observed from parents of 10 to 19 weeks of age, with peak fertility and hatchability at 14 and 12 weeks of age, respectively.
3. Sex ratios of 1:2 to 1:5 gave comparable fertility and hatchability results.
4. The hatching performance of quail eggs from cage and deep litter reared breeders was comparable.
5. Fertility and hatchability were directly proportional to the egg weight.
6. Quail egg shell colour, tints and blotches were found to influence hatching performance.
7. Storing quail eggs at 16 ± 2°C and 75 ± 5% relative humidity for more than 4 d reduced hatchability.
8. Hatchability of eggs stored at room temperature was improved if they were sealed in polyethylene bags.
9. Provision of light during the first 14 d of incubation resulted in a photo‐acceleration of about 3.2 h. 相似文献
2. Although the protein content of all tissues varied with age, the only statistically significant effect was on the level of protein in the gizzard.
3. The moisture content of the gizzard was significantly affected by age and blood by age and sex.
4. The fat content of the gizzard was significantly affected by age, as was the effect of sex on the fat content of blood.
5. The ash contents of heart and gizzard were significantly affected by age.
6. The phosphorus contents of the gizzard, heart and liver were significantly affected by age, as were the chloride content of heart and the calcium content of the liver. Blood potassium was significantly affected by sex. Fluctuations in the contents of other elements are discussed.
7. The variability in organ composition is discussed with respect to the degree of trimming and preparation of the samples. 相似文献
2. Oiling slowed the decline in albumen height (Haugh units) to that which occurred in unoiled eggs stored at 12 °C.
3. Oiling slowed the increase in albumen pH equally at 28 and 12 °C.
4. Oiling markedly decreased the weight loss of eggs stored at either temperature.
5. Oiling and temperature of storage were without effect on the whipping volumes of either albumen or unseparated albumen and yolk. 相似文献
2. Hyperphagia, amounting to twice the intake of control birds early in the experiment, occurred on the repletion day.
3. Final body weight attained 80% of that of the controls.
4. Body fat concentration decreased at first but returned to that of controls after 3 weeks.
5. A consistent hyperlipaemia was observed after food deprivation or restoration.
6. There was a marked increase in the digestive enzymes found in the small intestine, but not in the pancreas during the repletion day.
7. These responses may be considered as mechanisms to reduce the physiological manifestations of starvation. 相似文献
2. Eighty broilers were randomly divided into two groups. Birds in the control group were fed on maize–soybean-based diets. Birds in the treatment group were provided the same diet supplemented with 2 g/kg BA encapsulated in a vegetable oil matrix.
3. At the end of the trial (d 35), pH, bacterial composition and metabolites were determined in the crop, jejunum, ileum and caecum.
4. Growth performance variables and pH were not significantly different.
5. BA concentration decreased rapidly in the proximal gut. However, the treatment diet showed higher BA in the crop, jejunum, ileum and caecum.
6. Total lactate in the crop and D-lactate in the jejunum was higher in the BA treated group. Caecal total and branched chain fatty acids were decreased due to the treatment.
7. Lactobacilli populations were significantly altered by BA supplementation. A trend for increased lactobacilli was observed in the crop, while it became significant in the jejunum and ileum. Lactobacillus species responded differently to the treatment. Four of 5 measured Lactobacillus species, particularly in the ileum, followed the course observed for total lactobacilli; only Lactobacillus salivarius was not modified.
8. Correlation analysis showed that BA modified the intestinal microbiota. Lactobacilli correlated negatively to all studied clostridial clusters and enterobacteria. Clostridial clusters IV and XIVa were significantly increased in the jejunum, whereas only clostridial cluster XIVa was increased in the caecum.
9. Encapsulated BA modified the intestinal microbiota which can lead to the conclusion, that the main beneficial mode of action of BA in the gut appears to be the enhancement of lactic acid bacteria, which in turn may act as a vanguard against pathogens. 相似文献
2. Whole blood viscosity was more than twice as high, and plasma triglyc‐eride and haemoglobin concentrations were over 30% higher in fat line than in lean line females fed ad libitum or in restricted birds of both genotypes.
3. Mean cell haemoglobin concentration was higher and mean cell volume lower in fat compared with lean line females.
4. Food restriction was associated with lower plasma triglyceride concentrations, lower numbers of heterophils and monocytes and a lower heterophil‐lymphocyte ratio.
5. Fat line birds had a higher blood pCO2 and lower pH than lean line birds.
6. Thermal stress was associated in ad libitum‐fed birds with a rise in blood pH and a decrease in pCO2, and in restricted birds with a decline in blood pH and an increase in pCO2.
7. Blood creatine kinase activity increased in all groups under thermal stress. 相似文献
2. Both scanning and transmission electron micrographs revealed that low pH caused the formation of a dense aggregated gel matrix while increasing the pH resulted in more open structures.
3. At pH 7.5 both the white and dark meat exhibited superior water holding capacity (both raw and cooked) compared to the low pH treatments; all adjusted to 14% protein.
4. The high pH also resulted in a higher gel strength, while the low pH (4.5) produced a soft and crumbly texture. As pH was raised, gel strength gradually increased reaching a maximum at pH 7.5. Decreasing the pH resulted in lighter meat batters in both the white and dark turkey meat.
5. Muscle fibre microstructure appeared to be better preserved at the low pH treatments. 相似文献
2. Photoperiod treatments consisted of computer simulations of day lengths which occur naturally in the spring and autumn of the year. Both photoperiod treatments were given to hens in the autumn and spring.
3. Data were collected for growth evaluations at 2‐ to 4‐week intervals to 16 weeks of age. No significant season × photoperiod interactions occurred.
4. The spring trial resulted in greater body weights and better food conversions (food/gain) than the autumn trial.
5. Simulated autumn daylengths resulted in greater body weights and improved food efficiency at 16 weeks of age compared with simulated spring daylengths.
6. The pattern of growth (period changes) was influenced by season, but not photoperiod.
7. Season and photoperiod both have important and independent influences on the growth of the turkey hen. 相似文献
2. The data conformed to a mixed model and adjustments were made for the fixed effects sex, hatch date and location. Adjustment improved the precision of the estimates by reducing the error variances significantly.
3. Rearing equal numbers of birds from each family at different locations made the interactions negligible.
4. Weight gain was greater if illumination intensity up to 35 d was less.
5. Females were not heavier on the 1st day but were heavier on the 14th and 35th days than males.
6. Variance components and genetic parameters were estimated. 相似文献
2. In the rabbit osmolality of the fluids from the different segments of the digestive tract was similar (331 ± 12 mOsm) and slightly hypertonic to blood plasma (297 ± 0.12 mOsm).
3. In the hen osmotic pressures were: crop 537, gizzard 312, duodenum 571, proximal jejunum 650, distal jejunum 573, proximal ileum 514 and distal ileum 451 mOsm. Only osmolality of the crop contents was influenced by egg formation.
4. In the cockerel osmotic pressure in the alimentary tract followed the same pattern as the hen and was modified by the time of day.
5. Plasma osmolality in the fowl was about 320 mOsm. Absorption of water across the proximal jejunum is achieved therefore against a gradient of about 330 mOsm in the female and 420 mOsm in the male fowl. 相似文献
2. Breeder hens fed ad libitum and subjected to either conventional or intermittent lighting ingested respectively, 25 g and 14 to 17 g more than hens restricted to 115 g/d.
3. Body weight was greater in hens fed ad libitum irrespective of the lighting pattern and of the amount of food intake.
4. Persistency of egg production was impaired by intermittent lighting.
5. Ad libitum feeding reduced egg fertility. The decrease was larger in breeder hens on intermittent lighting.
6. Hatchability was increased in hens submitted to the symmetrical lighting pattern (0.5L:3.5d).
7. Egg and chick weights were higher in hens fed ad libitum.
8. Shell index and shell breaking strength increased in restricted hens on the intermittent lighting pattern (0.5L:3.5d) × 6.
9. The best performance was obtained in restricted hens on the conventional lighting pattern. 相似文献
2. Very large egg batches are required to detect small improvements in the hatchability of good hatching strains.
3. Small‐scale laboratory studies on hatchability are best confined to strains and species of low hatchability in which larger between‐treatment differences may be expected.
4. The results of hatchability studies should always be subjected to tests of statistical significance.
5. There is a strong case for studying continuous variates in the laboratory before proceeding to large‐scale hatchability studies. 相似文献
2. Rocking embryo cultures during the first half of incubation enhanced embryo growth.
3. Embryos explanted into ‘surrogate’ eggshells of either other individuals or other species have been successfully ‘hatched’.
4. A normal chorioallantois is formed in these surrogate eggshells. This enables a functional albumen sac to form and eggshell resorption to be achieved.
5. Embryos grown in ‘surrogate’ eggshells are slightly smaller than controls but otherwise normal.
6. The technique provides opportunities for genetic engineering experiments. 相似文献
2. Because the traditional method of determination of droppings digestibility coefficients of nitrogen may lead to systematic errors in estimating the feeding value of foodstuffs, a method is proposed to determine the ileal digestibility coefficients. The ileal method is compared with the droppings method for a mixed food and for two foodstuffs: wheat and solvent‐extracted soyabean meal.
3. Birds selected for efficient food conversion showed distinctly higher digestibility coefficients for all nutrients than birds selected for high growth potential or birds from a commercial strain.
4. The influence of age on digestibility coefficients was not consistent.
5. Female birds showed digestibility coefficients which were, in general, 3% higher than those of male chickens.
6. Interactions between genotype and sex and between genotype and age for energy metabolisability were the only interactions observed for digestibility measurements.
7. The method of determination influenced the amino acid digestibility coefficients of the mixed food and the relative feeding values of wheat and soyabean meal.
8. It is important to use well defined animals (genotype, sex, age) in evaluating foodstuffs.
9. The preferred method for determination of digestibility coefficients of nitrogen and amino acids is based on ileal sampling, although the differences in amino acid digestibility coefficients were small between methods. 相似文献
2. In only one experiment was weight gain significantly improved when the barley was heated.
3. Autoclaving barley at 120 °C for 30 min reduced dietary dry matter digestibility and treating the barley with dilute acid before heating had no effect on its nutritive value.
4. Supplementing diets containing commercial barley with a‐amylase produced slightly conflicting results in that there was an improved weight gain, food conversion efficiency and digestibility value in two of three experiments.
5. The digestibility and metabolisable energy values of a North American six‐row spring barley (Glacier) were significantly improved by enzyme supplementation.
6. The effect of the enzyme on diets containing a high amylose barley (Glacier Pentlandfield) was positive but not significant. 相似文献
2. Hens of the population with the high incidence of whitening appeared to be more fearful than hens of the population with the low incidence of whitening.
3. Brown colouration of the egg shell and the incidence and degree of shell whitening declined as the hens aged.
4. Brown colouration and egg shell whitening were most pronounced on the blunt ends of the eggs.
5. A large part of the variation in egg shell whitening was attributable to the individual (hen) component of variance.
6. Differences in egg shell whitening, between the two populations, were detectable throughout the 26 weeks of the experiment.
7. Oviposition intervals were similar for normal and coated eggs when birds were not exposed to disturbance.
8. Disturbance of hens increased oviposition intervals and the incidence and degree of shell whitening, to a similar extent, in both populations.
9. It is concluded that stress‐related egg retention is not the sole factor responsible for abnormal egg shell whitening. Shell whitening may occur as a consequence of the premature termination of shell pigmentation as well as a consequence of the retardation of oviposition which occurs when hens are disturbed. 相似文献
2. It was fed at 16 weeks of age to five separate groups (groups 2 to 6) each of 50 to 60 birds.
3. Group 2 was fed on a normal layers’ diet at 23 weeks of age, group 3 at 27 weeks, group 4 at 31 weeks, group 5 at 35 weeks and group 6 at 55 weeks while the control group (group 1) of similar size to groups 2 to 6 was subjected to a normal commercial treatment for laying stock.
4. In all the experimental groups the onset of sexual maturity occurred normally, but only one or two eggs were laid before laying ceased under the influence of the treatment.
5. Laying re‐started when the hens were fed on a normal diet and production rapidly rose to a high level.
6. Groups 1, 2 and 3 differed little in the total number of eggs produced up to 72 weeks of age.
7. In all experimental groups there were fewer very small, small and medium eggs than in the control group.
8. It is suggested that the use of a low‐calcium diet before the onset of lay may have advantages which could be exploited on a commercial scale. 相似文献