1. Growth, food intake, and food preference were measured in two experimental lines (White Rocks and White Leghorns) of chickens fed diets varying in content of lysine, methionine, or tryptophan. Diet A was balanced in all amino acids, while the remaining 6 diets were moderately ( ～ 30%) or slightly ( ～ 15%) deficient in either lysine, methionine, or tryptophan relative to NRC recommendations for broiler diets.
2. Body weight and food utilisation efficiency of White Leghorns at 10 d of age were not affected by diet, whereas the lower concentrations of lysine and methionine depressed these traits in White Rocks.
3. Tryptophan deficiency reduced food intake of White Leghorns, but not White Rocks.
4. With choice feeding of balanced and deficient diets from day 10 to 16, preferences between the diets were minimal for White Leghorns, whereas for White Rocks there was an almost immediate preference for the balanced diet, followed by lack of preference or preference for the deficient diet.
5. Apparently for some genetic stocks there is rapid adjustment to deficiencies in these amino acids with overconsumption, followed by compensation for preference of the balanced diet. The response, however, will vary depending on the deficient amino acid. 相似文献
Hardly a word was said about Fermat's Last Theorem at the joint meetings of the American Mathematical Society and the Mathematical Association of America, held this year from 4 to 7 January in San Francisco. For Andrew Wiles's proof, no news is good news: There are no reports of mistakes. But mathematicians found plenty of other topics to discuss. Among them: a computational breakthrough in the study of turbulent diffusion and progress in slimming down the proof of an important result in group theory, whose original size makes checking the proof of Fermat's Last Theorem look like an afternoon's pastime. 相似文献
The self-assembly of monodisperse gold and silver colloid particles into monolayers on polymer-coated substrates yields macroscopic surfaces that are highly active for surface-enhanced Raman scattering (SERS). Particles are bound to the substrate through multiple bonds between the colloidal metal and functional groups on the polymer such as cyanide (CN), amine (NH(2)), and thiol (SH). Surface evolution, which can be followed in real time by ultraviolet-visible spectroscopy and SERS, can be controlled to yield high reproducibility on both the nanometer and the centimeter scales. On conducting substrates, colloid monolayers are electrochemically addressable and behave like a collection of closely spaced microelectrodes. These favorable properties and the ease of monolayer construction suggest a widespread use for metal colloid-based substrates. 相似文献
Mycobacterium bovis was probably introduced into New Zealand with cattle imported in the early 19th century. A tuberculosis control programme was introduced for cattle in 1945. However, the control of tuberculosis in cattle and deer in New Zealand over the past two decades has been hampered by the presence of an important wildlife reservoir, the Australian brushtail possum (Trichosurus vulpecula). While the importance of this source of infection has been suspected by the Ministry of Agriculture for some time, scientific proof has been lacking until recently. A new control programme is currently being finalized with the following objectives: to reduce the prevalence of herd infection in vector free areas to internationally accepted levels, to prevent the establishment of tuberculous vectors in new areas, to decrease the number and size of existing areas where tuberculous vectors exist, and to encourage land-owners to take action against tuberculosis on their properties and in their herds. 相似文献
To assess changes in 24 blood constituents in frozen serum and heparinized plasma, blood samples were drawn from 10 clinically normal German Shepherd army dogs. The storage characteristics of nine enzymes (ALP, ALT, amylase, AST, CK, GGT, GLDH, LDH, lipase), and 15 metabolites and minerals (albumin, bile acids, bilirubin, calcium, cholesterol, creatinine, fructosamine, glucose, magnesium, phosphate, potassium, protein, sodium, triglycerides, urea) were studied. Parallel samples of serum and heparinized plasma were stored for 90 and 240 days at two different storage temperatures, -200 degrees C and -700 degrees C. Sixteen of the 24 analytes (ALP, ALT, amylase, AST, CK, GGT, GLDH, LDH, bile acids, calcium, cholesterol, creatinine, fructosamine, magnesium, phosphate, urea) showed statistically significant (p < 0.05) changes during the storage period related to storage time, storage temperature, and sample type. Seven of the analytes (amylase, GGT, GLDH, LDH, bile acids, fructosamine, magnesium) showed changes of possible clinical importance with mean differences from baseline larger than 20% for the enzymes and 10% for the metabolites and minerals during the storage periods. 相似文献
1. Behaviour, production and welfare of ISA Brown medium hybrids were assessed in 2 trials (each from 20 to 44 weeks of age) of a novel design of cage for laying hens: the Edinburgh Modified Cage (EMC).
2. The EMC was 600 mm wide, 450 mm deep and 450 mm high at the rear; it had a softwood perch and at one side a 250 mm wide nest box (containing litter or artificial turf) with a dust bath direcdy above. It housed 4 birds and provided 675 cm2/bird in the main cage with an additional 281 cm2 /bird in the nest box. The nest box and dust bath had automatically controlled doors which were closed at night. There were 18 EMC; in the first trial these were compared with 6 control cages with perch but without next box or dust bath.
3. Hens spent 32 to 37% of day time on the perch, 5 to 7% in the dust bath and 5 to 6% in the nest. At night 92 to 98% roosted on the perch.
4. Initially only 55 to 70% of eggs were laid in the nest box partly because some eggs were laid before dawn. Once the door was retimed to open 3h before lights‐on the proportion rose to 91 to 96%. Very few eggs were laid in the dust bath. Pre‐laying behaviour lasted longer in treatments with nest boxes (55 to 76min) than in control cages (48min); disturbance was slight in all treatments, but lowest in control cages.
5. Dust baths were well used, with on average 61% of hens dust bathing during a 3‐h afternoon observation period compared with only 17% in control cages. Two birds could use the dust bath simultaneously.
6. It was concluded that although a number of minor design features still required attention the EMC has potential to reduce the disadvantages of conventional cages for welfare while retaining their advantages and has possible commercial application. 相似文献
1. The effect of probiotic supplementation on egg production, on serum and yolk cholesterol and on egg shell thickness in 24 White Leghorn layers was studied from 28–38 weeks of age.
2. In 3 treatments the diet was supplemented with 0, 100 and 150 mg probiotic/kg food.
3. In the 100 mg probiotic group, egg production improved by 5%, and shell thickness improved slightly, with fewer thin‐shelled eggs than in the control (8.6% compared to 18.6%).
4. The initial serum cholesterol concentration of 170.2 mg/dl in control birds remained similar throughout the 10‐week experimental period, whereas in the 150 mg group the initial value of 176.5 mg/dl decreased to 114.3 mg by week 10.
5. Yolk cholesterol concentration was 14.69 mg in the control group and 11.28 and 11.37 mg/g in the 100 and 150 mg probiotic groups respectively. Overall mean total egg cholesterol was thus reduced by probiotic supplementation. 相似文献
