2. Selection significantly increased plasma LH concentrations in mid‐sequence ovulatory cycles of Australorps but not in the White Leg‐horns.
3. Selection in the Australorps apparently increased the rate of ovarian follicular maturation, resulting in more frequent LH peaks.
4. The effect of selection on plasma LH concentrations is a function of the lighting condition to which the hens are exposed. 相似文献
2. A circadian system was postulated to control the restriction of ovulation to an 8‐h period of the day under conventional 14 h light: 10 h dark regimes.
3. The final phase of follicular maturation was postulated to commence after ovulation of the preceding ovum in the hierarchy.
4. Ovulation was postulated to occur when a mature follicle was present in the ovary during the appropriate phase of the circadian‐linked system.
5. The predicted times of oviposition were within the standard error of the observed times of oviposition under 21‐, 24‐ and 28‐h photoschedules.
6. It was concluded that this hypothesis for the control of the ovulatory cycle of the hen is consistent with current knowledge. 相似文献
2. Injection of laying hens with 60 mg metyrapone on 5 successive days reduced the effectiveness of exogenous ACTH in increasing the plasma concentration of corticosterone and abolished the system of “ open “ and “ closed periods “ for pre‐ovulatory LH release. Thus, pre‐ovulatory LH surges and ovipositions occurred throughout the 24‐h day instead of being restricted to an 8 to 10‐h period of the day.
3. These observations suggest that changes in environmental stimuli such as light act via the adrenal gland in regulating the timing of the “ open period “ for the pre‐ovulatory release of LH in the hen. 相似文献
2. Dry plucking increased weight loss due to plucking and eviscerating, and reduced chilled carcass yield.
3. Dry eviscerating increased carcass water uptake during chilling.
4. Pre‐chilling with running water increased carcass water uptake compared with chilling in ice and water alone.
5. Water uptake during chilling appeared to be increased by longer eviscerating time. 相似文献
2. Time of day of injection did not modify the response to corticosterone of 3‐week‐old chicks kept under natural daylight nor of 7‐week‐old broilers receiving additional illumination.
3. Pure White Rock chicks and Cornish x White Rock crossbred chicks responded similarly to corticosterone injections at 3 weeks of age.
4. Seven‐week‐old female birds treated with corticosterone had significantly larger abdominal fat pads than similarly treated males.
5. Corticosterone injection was more effective in increasing the proportion of liver fat in 7‐week‐old birds than in 3‐week‐old ?hicks.
6. The increased amount of abdominal and liver fat due to corticosterone injections administered at 3 weeks of age disappeared after 3 weeks, but growth depression was still evident. 相似文献
2. The different varieties of wheat investigated contained different proportions of water‐soluble to water‐insoluble hemicelluloses.
3. By comparison of the arabinose to xylose ratios it was concluded that water‐soluble and insoluble arabinoxylans of wheat were branched to the same degree.
4. Starch from six wheat varieties grown in the U.K. was very well digested by adult cockerels and true metabolisable energy values of the wheats were high.
5. Small amounts of cell wall carbohydrates were digested by adult cockerels. 相似文献
2. Treatment with TA improved growth, increased carcass moisture and tended to decrease carcass fat and ash; protein content was not altered by implantation.
3. Treatment with TA produced a marked improvement in efficiency of conversion of dietary protein to carcass protein.
4. Carcass formation of 70‐ and 77‐d‐old turkeys of both sexes implanted with 20 mg TA at 49 d of age was not markedly different from that of controls in terms of the relative proportions of the major body components nor in relative skeletal proportions.
5. Implantation with TA reduced linear and appositional skeletal growth both relative to soft tissue growth and relative to skeletal growth of control turkeys.
6. The rate of bone remodelling was reduced more than the rate of appositional growth so that bone cortical thickness was increased.
7. The changes in the skeleton effected by TA are consistent with the hypothesis that the drug acts by decreasing the rate of protein turnover, with catabolism being depressed more than anabolism. 相似文献
2. Half the hens had undergone beak trimming at 18 weeks, but in many cases regrowth had occurred.
3. Plumage damage and loss was significantly reduced in beak‐trimmed birds compared with birds with normal beaks. Tier and cage design had no effect.
4. This finding supports the idea that feather pecking is the important factor in causing plumage damage, rather than abrasion.
5. A comparison between 64 birds in which beak regrowth had occurred, and 64 in which it remained truncated, showed that both groups had similar plumage scores.
6. It appears to be the beak‐trimming procedure which is important; subsequent regrowth being irrelevant. 相似文献
2. Restricted birds were lighter throughout the experiment.
3. Relative adrenal weight tended to be greater in restricted birds but the difference decreased with time.
4. There was no depletion of adrenal cholesterol: from week 5 there was a significantly greater amount in the adrenals of restricted birds.
5. After 1 week of restriction plasma corticosterone concentration was 73% greater than in controls. It decreased progressively, falling within the normal range at 5 weeks.
6. Restricted birds were hypoglycaemic from weeks 2 to 7 and hyper‐lipacidaemic throughout. A negative correlation between plasma glucose and free fatty acids was found. 相似文献
2. A randombred control population of known pedigree was used to measure the environmental trends.
3. Selection in pure lines resulted in concomitant improvement in the crosses for the selected as well as the correlated traits.
4. Cross performance was comparatively more than expected on the basis of mid‐parent values, indicating involvement of non‐additive gene action in the expression of cross performance.
5. Crosses responded better to independent culling level selection for egg weight than their parents.
6. Heterosis appeared to increase in later generations as compared with initial generations of selection. 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. In 4 consecutive trials, 4752 hens were recorded for keel bone status. Evaluation of plumage condition was made for 1440 hens and bone breaking strength was recorded for 1200 hens. A total of 4962 eggs were analysed for internal and external egg quality traits. Analyses involved 30 small group compartments per trial.
3. The layer line had a much more pronounced influence on humerus breaking strength than on tibia breaking strength.
4. Plumage condition, particularly on the neck, was positively correlated with humerus breaking strength in both layer lines.
5. An average of 34% of LB and 23% of LSL hens showed keel bone deformities, with higher proportions of slight deformities.
6. Slight keel bone deformities, rather than moderate to severe, increased significantly during the laying period.
7. Stocking density had no influence on bone breaking strength, keel bone status and egg quality traits.
8. LB layers had a 1.4-fold higher humerus, but only a 1.06-fold higher tibia breaking strength compared to LSL layers.
9. Tibia breaking strength was significantly affected by the interaction of group size and layer line. LSL layers in small groups had lower tibia breaking strengths than those of the large groups. 相似文献
2. The poults were free from contamination on arrival at the rearing house but were contaminated via the water supply from troughs which had been ineffectively fumigated.
3. Foodstuffs did not appear to be a source of contamination.
4. The spread of salmonellae in this turkey rearing enterprise was very similar to that in chicken rearing houses. 相似文献
2. In total, 83 single unit activities were recorded from the caudal mesenteric nerve.
3. Receptors were grouped according to their locations in different layers of the rectum as (i) over the branching points of the blood vessel or in the serosal layer, (ii) in the muscle layer or (iii) in the mucous membrane of the rectum.
4. All the receptors, both spontaneous and non‐spontaneous, responded to mechanical probing. Receptors of the muscle layer responded to distension also and showed a slowly‐adapting nature. Most of the receptors of the other two groups were of the rapidly‐adapting type.
5. Conduction velocity ranged from 0.76 to 34.6 m/s.
6. Sympathetic afferent fibres from the hind gut ascend along the intestinal nerve and join the caudal mesenteric nerve via the colonic ganglion. 相似文献
2. Addition of 10 g ascorbic acid/kg to the control diet (without excess tyrosine) produced no beneficial effects on performance. Excess dietary tyrosine caused depressions in all measures of performance.
3. Adding 0.1, 1, 10 or 20 g ascorbic acid/kg to the diet containing excess tyrosine tended to improve performance.
4. Subcutaneous injection of 50 mg ascorbic acid/bird d to chicks receiving excess tyrosine brought about a significant improvement in body‐weight gain.
5. The elevation of plasma free tyrosine caused by excess dietary tyrosine decreased as dietary ascorbic acid increased.
6. Ascorbic acid can alleviate, though not completely counteract, the adverse effect of excess dietary tyrosine. 相似文献
2. Oviposition generally occurred between 04.00 and 06.00 h, 7 to 9 h after the onset of the dark period the previous day. Ninety‐seven percent of eggs were laid by 07.00 h.
3. The mean ± SD time interval between consecutive ovipositions was 24.0 ± 0.3 h, with a range from 23.5 to 24.5 h.
4. It was estimated that ovulation occurred on average 10 min after oviposition, and the ovum spent 15 to 30 min in the infundibulum, 2.5 to 3 h in the magnum, 2 to 2.5 h in the isthmus and 18.6 h in the shell gland. 相似文献
2. The Sinai egg was smaller and its shell thicker and stronger than the Leghorn egg. All the differences were statistically significant.
3. Shell thickness and strength of Leghorn eggs were in accordance with values predicted on the basis of egg mass, while those of the Sinai and the two crosses were considerably higher than predicted.
4. The apparent differences in mean egg mass between Sinai and Leghorn breeds did not explain the differences in egg‐shell quality, neither did the shape index which was very similar among all breeds.
5. The findings suggest that the differences in egg‐shell properties are of a genetic origin.
6. The thick, strong and less permeable egg‐shell of the Sinai breed may reflect adaptations to its arid environmental origin and to incubation in the open.
7. These genetically‐determined egg‐shell characteristics might serve in a future selection for improved egg‐shell quality in poultry. 相似文献
2. Biotin deficiency decreased hepatic activity of pyruvate carboxylase [EG 6.4.1.1] but activity of acetyl‐CoA carboxylase [EG 6.4.1.2] was comparatively unaffected.
3. Increasing dietary protein increased the severity of biotin deficiency as assessed by skin lesions and decreased plasma biotin concentrations.
4. The severity of the skin lesions over all the treatments was most closely related to plasma biotin concentration. 相似文献
2. Protein and energy metabolism were studied in males from these selected lines fed on a diet of intermediate protein content.
3. All selected birds retained more nitrogen than those studied 10 years previously.
4. There was no difference in nitrogen retention between groups, although relative growth rate of group B birds was higher.
5. Heat productions relative to gross energy intake were 0.38 (group B) and 045 (group A). Energy retentions relative to gross energy intake were 0.39 (group B) and 0.35 (group A); the difference being primarily due to higher fat retention in group B.
6. Using a common maintenance requirement for metabolisable energy, group B utilised metabolisable energy for growth (0.78) better than did group A (0.71).
7. At 53 d of age plasma glucose (10%) and insulin (50%) were higher in group B than in group A. 相似文献
2. Infusions of 5 ml of 40, 100 or 150 g glucose/1 solution over 2 min caused a non‐significant depression of food intake compared with a 9 g NaCl/1 control solution.
3. Infusions of a range of isotonic glucose solutions (0 to 60 g glucose/1, 300 mosm) at 1.4 ml/min over 3 h caused food intake depression within the 3‐h period (P<0.01) proportional to the logarithm of the dose.
4. This effect was not observed when 60 g glucose/1 was infused at the above rates into the jugular vein.
5. Starvation of the bird for 21 h accentuated the depressive effect of glucose load on food intake, especially when birds were not given food until after the 3‐h infusion.
6. The infusion of solutions of sodium chloride (1.0 to 13.0 g/1, 33 to 433 mosmoles/kg) at. 1.4 ml/min over 3 h stimulated food intake within the range of 3 to 7 g NaCl/1 (100 to 233 mosm) but suppressed intake outside this range. This can be interpreted as a possible interaction with water intake control.
7. Infusion of 20 ml of glucose solution (0, 18 or 54 g/l) over 5 min into the crop and 0, 3.75 or 60 g glucose/1 at 1.4 ml/min over 3 h into the hepatic portal vein, caused an additive, linear depression of food intake. 相似文献