2. GH and prolactin concentrations were highest in young birds and higher in males than in females.
3. In both sexes GH and prolactin concentrations were correlated inversely with age and body weight and positively with relative weight gain.
4. Differences in growth rate between broilers and layers were related to differences in blood GH concentrations.
5. Water deprivation for periods of 6, 12, 18 or 24 h increased plasma prolactin markedly but did not affect GH secretion significantly. 相似文献
2. Mean GH concentration, baseline and amplitude of pulses were slightly, but not significantly, greater in LF chickens. Length and frequency of pulses were similar.
3. LF chickens exhibited higher plasma triiodothyronine (T3) concentrations. This difference between genotypes disappeared when the diet was supplemented with 1 mg/kg T3.
4. Specific binding of GH to liver membranes was higher for the fat line but was depressed by T3 supplementation to the same level in both lines. No difference was observed between lines for affinity constants.
5. It is concluded that direct selection for leanness has a less pronounced, if any, effect on GH pulsatility as compared with selection for food conversion efficiency; therefore, different physiological mechanisms are triggered to achieve leanness. 相似文献
2. Reactivity of CD3 antiserum in chicken intestine was very good.
3. Increased numbers of epithelial lymphocytes as well as infiltration of CD3 cells into the lamina propria were demonstrated.
4. Intestinal homogenate caused impaired growth and bad feathering in broiler chickens until 21 d of age. 相似文献
2. A total of 1056-d-old Cobb male broilers were housed in experimental pens (22 chickens per pen) for 42 d. Three levels of CaMont (0, 2.5 and 5 g/kg) and two levels of aflatoxins (0 and 3 mg/kg) were assayed. Each treatment had 8 replicate pens of 22 broiler chickens each.
3. Of all the chickens tested in the experiment, the ones treated with aflatoxins were the most adversely affected. CaMont treatment at concentrations of 2.5 and 5 g/kg improved body weight of chickens at 42 d of age by 13.3% and 22.7%, increased daily feed intake by 9.7% and 24.7%, and improved the productive efficiency index of chickens by 53% and 66.5%, respectively.
4. Dietary CaMont positively affected parameters such as weight of liver, heart and gizzard; however, serum potassium concentration decreased by 15.3% compared with that of chickens given only the aflatoxin-contaminated diet.
5. CaMont did not cause adverse effects in chickens that did not receive aflatoxins.
6. CaMont at pH 8.5 partially reduced the toxic effects of aflatoxins in broilers when included at levels of 2.5 and 5 g/kg in the diet. 相似文献
2. The commercial broilers were divided into 2 groups of 100 birds each; CoQ9‐treated group and non‐treated group.
3. The chickens were grown in a positive‐pressured house with double high efficiency particulate air filtered intakes and exhaust, and thus were strictly isolated from infectious agents.
4. The chickens (15 to 21 d old) were exposed to cold stress in order to induce ascites.
5. The number of birds with ascites in the C0Q3‐treated group was significantly lower than in the non‐treated group.
6. Survival and production rates were better in the CoQ^‐treated group than in the non‐treated group. 相似文献
2. Broilers selected for food conversion efficiency had greater growth rates and superior food conversion efficiencies than broilers selected for growth rate. No interactions between broiler strain and oxygen level were observed.
3. Increasing environmental oxygen level decreased N efficiency in both broiler strains. Nitrogen turnover was non‐significantly decreased.
4. Ascites may only occur when broilers are able to cope with small environmental adversities while maintaining optimal growth rates. 相似文献
2. CSM was fermented with Bacillus subtilis, Aspergillus niger and A. oryzae for 7 d. A total of 300 one-d-old male Ross 308 broiler chickens were used in a 42-d experiment in which the birds were randomly allotted to one of 5 dietary treatments (containing 0%, 10% and 20% CSM or FCSM) in a completely randomised design. Birds were reared on litter floor and had free access to feed and water during the experiment.
3. Results indicated that the fermentation process significantly reduced crude fibre and free gossypol, while it increased crude protein content and lactic acid bacteria (LAB) count in CSM.
4. The use of FCSM instead of CSM significantly improved growth performance of broilers. The abdominal fat yield in treatments containing FCSM was significantly lower than in the other treatments. The increase in the population of LAB in the crop and decrease in the population of coliforms in the ileum of birds fed on diets containing FCSM were more significant than in other birds. Villi in the duodenum and jejunum of the birds fed on diets containing FCSM were significantly higher than for the other experimental groups.
5. The positive effects of diets containing FCSM on growth performance and intestinal health of broiler chickens showed that this processed source of protein can serve as an appropriate alternative for SBM in diets for broiler chickens. 相似文献
2. Mean body weight of the ascites‐susceptible line (BC‐line) was higher than that of the ascites‐resistant line (A‐line). Adding 0.5 mg T3/kg of the diet depressed growth rate to the same extent in both lines. The effect of T3 on growth was more pronounced for males than for females.
3. T3‐supplementation increased the relative weight of the heart and the incidence of RVH to the same extent in both lines. More of the T3‐treated BC‐line chickens had fluid accumulation in the abdominal cavity than the T3‐treated A‐line chickens.
4. Dietary T3‐treatment depressed the plasma concentration of growth hormone (GH) profoundly and insulin‐like growth factor (IGF‐I) slightly but to the same extent in both lines. The coefficient of variation of GH concentrations indicate that T3 treatment mainly decreased GH‐pulsatility in young growing broilers.
5. Higher doses of dietary T3 (1 and 2 mg/kg) increased mortality in a dose‐dependent manner. With 2 mg T3/kg, mortality in the BC‐line was almost double that in the A‐line.
6. These studies indicate that the development of ascites could be linked with thyroid function. Moreover, dietary T3 supplementation could be used to help identify ascites‐inducing factors or genetic lines with differential sensitivity for ascites. 相似文献
2. The cells from both sources were shown to have the characteristics of adipocyte precursor cells. On reaching confluence, lipoprotein lipase activity was induced and the cells from both strains accumulated large amounts of lipid in the presence of chicken serum.
3. Measurement of cell number over time in culture and calculation of cell doubling times showed that cells from broilers proliferated at a faster rate than those derived from layer‐strain chickens. This was the case whether primary or secondary cell cultures were used. Primary cultures of broiler cells had a doubling time of 22 h versus 39 h for layer cells.
4. The contribution of such a difference in proliferative rate to the differential rate of adipose tissue growth between broiler and layer strains observed in vivo is discussed. 相似文献
2. Environmental enrichment improved body‐weight gain, relative body‐weight gain and gain: food ratio but had no effect on circulating GH or prolactin concentrations.
3. Weight gain and gain : food ratio were greater in the broilers than in the layer chicks, while plasma GH and prolactin (females only) concentrations were less.
4. There were no sex differences in weight gain and relative weight gain but gain : food ratio was significantly greater in females than in males. In both strains plasma GH concentrations were higher in males than in females and prolactin concentrations were higher in male than in female broilers. 相似文献
2. Both IGF‐I and IGF‐II administration resulted in a rapid, significant decrease in plasma GH concentrations, but the concentrations of both triiodothyronine and thyroxine remained unchanged.
3. Immunisation against both IGF‐I and IGF‐II produced a significant elevation in plasma GH.
4. These data show that both IGFs can regulate GH concentrations in birds. Furthermore, the immunoneu‐tralisation data suggest that these hormones have a physiological role in the regulation of GH secretion. 相似文献
2. Growth was significantly enhanced by regular handling in broilers and the females of the layer strains and gain : food ratios were generally greater in the handled birds.
3. There were no significant treatment effects on growth or gain : food ratios in males of the layer strains.
4. Males had higher relative weight gains and gain : food ratios than females. 相似文献
2. At 22°C, weight gain of LL broilers was the same as in FL chickens, but at the high temperature LL birds grew to a greater weight than FL ones.
3. Food conversion efficiency was not affected by ambient temperature in LL chickens but was depressed in FL ones at 32°C.
4. Increasing dietary protein content did not alleviate heat‐induced growth depression irrespective of the genotype.
5. Gross protein efficiency was higher in LL chickens and was less depressed at 32°C than in FL birds.
6. Fat deposition decreased with increasing protein concentration at normal temperature in both genotypes; at high temperature, high protein content enhanced fatness, particularly in LL chickens.
7. Thus, genetically lean broilers demonstrated a greater resistance to hot conditions: this was indicated by enhanced weight gain and improved food and protein conversion efficiencies. 相似文献
2. Mean temperature in the immediate environment of the chicks was 2.0°C lower than the setpoint of 1 d of age. During the first week this initial temperature difference gradually rose to 1.7°C above setpoint. At 18 d of age a further rise to a mean difference of 4.0°C above setpoint was measured. The difference then remained constant from 32 d of age until the end of the fattening period.
3. It was concluded that the chickens were actually brooded at 30°C. During the rearing period the ambient temperature in the close vicinity of the broilers gradually declined to 26°C.
4. During the finishing period, ambient temperature around the broilers was far above the value recommended for optimal food intake and growth.
5. These results are discussed in relation to heat generation and heat fluxes in the broiler houses. 相似文献
2. Despite the absence of a control flock, this programme has demonstrated that selection in a broiler population can rapidly increase the incidence of TD.
3. There was consistent circumstantial evidence of the presence of a major sex‐linked gene, the recessive allele of which is associated with an increased incidence of TD.
4. The realised heritability estimates (obtained in the absence of a control flock) consistently exceeded 1.00, suggesting the presence of an environmental trend favourable to the onset of TD over the four generations of this investigation.
5. There was a high maternal component or dominance genetic component, or both, for the inheritance of TD in the final generation, suggesting that environmental factors associated with the female parent line may influence the incidence of TD in broilers. 相似文献
2. The relationship between early and final body weight was investigated for individual chickens.
3. The feasibility of automatic separation of birds into different weight groups was evaluated and consideration given as to whether this technique could be used for sex‐separation of an as‐hatched flock.
4. The results suggest that the present commercial practice of male selection at flock depopulation may be less reliable than many producers believe. 相似文献
2. IBV variants were isolated from broiler flocks with enteric and respiratory problems in two regions of Brazil. The USP-10 isolate, of enteric origin, was inoculated via the oral oroculonasal routes into IBV-antibody-free broilers and specific pathogen-free (SPF) chickens to determine tissue tropism and pathogenicity and compared with an IBV variant (USP-50) isolated from chickens showing signs of respiratory disease only.
3. Both USP-10 and USP-50 strains caused similar pathological patterns by either route of inoculation. Both variants were detected in respiratory and non-respiratory tissues, including the kidney, intestine and testis.
4. Broilers were more susceptible to infection than SPF chickens, and seroconversion was detected in all of the chicks. 相似文献
2. From 28 to 55 d of age, birds were given apilarnil orally. The effects of low (2.5 g/bird) and high (7.5 g/bird) doses of apilarnil on growth performance, testicular weight, secondary sexual characteristics, blood lipids, testosterone and fearful behaviour were evaluated.
3. Apilarnil administration did not cause a positive effect on growth performance of male and female broilers suggesting that apilarnil did not have an anabolic effect.
4. Apilarnil administration suppressed blood glucose and cholesterol.
5. Birds receiving apilarnil remained immobile for a shorter period in a tonic imobiliy test and showed less home-cage avoidance responses suggesting a lower level of fearfulness.
6. Increases in testicular weight, testosterone concentration and comb growth in males receiving apilarnil implied that it stimulates the sexual maturation at an early age. However, a similar stimulation of secondary sexual characteristics was not observed in females. 相似文献
2. Chickens were given a control diet with normal drinking water, or diets supplemented with cashew nut shell liquid (CNSL) or grape seed extract (GSE), or a control diet with electrolysed reduced water (ERW) for 19 d after hatch. Thereafter, chickens were exposed to a temperature of either 34°C continuously for a period of 5 d, or maintained at 24°C, on the same diets.
3. The control broilers exposed to 34°C showed decreased weight gain and feed consumption and slightly increased ROS production and malondialdehyde (MDA) concentrations in skeletal muscle. The chickens exposed to 34°C and supplemented with ERW showed significantly improved growth performance and lower ROS production and MDA contents in tissues than control broilers exposed to 34°C. Following heat exposure, CNSL chickens performed better with respect to weight gain and feed consumption, but still showed elevated ROS production and skeletal muscle oxidative damage. GSE chickens did not exhibit improved performance or reduced skeletal muscle oxidative damage.
4. In conclusion, this study suggests that ERW could partially inhibit ROS-induced oxidative damage to skeletal muscle and improve growth performance in broiler chickens under medium-term chronic heat treatment. 相似文献
2. Birds were restricted in intake to 50% (group FI 50) or 75% (group FI 75) of ad libitum from 5 to 11 d of age; all birds were fed ad libitum from 12 to 39 d of age.
3. Relative growth rates from 12 to 39 d of age of group FI 50 were higher (P<0.05) than group FI 75 and control group.
4. No significant differences in food conversion ratio, carcase fat and abdominal fat between groups were observed.
5. At 12 d of age, relative weight of the empty digestive tract of group FI 50 was higher (P< 0.05) than that of the control group and group FI 75.
6. The increased weight of the empty digestive tract may have contributed to the ability of the chickens to achieve compensatory growth after the restriction period. 相似文献