基因组学和生理学在家禽福利育种中的应用

<正>1最近十年的欧洲家禽福利经验在欧洲,农场动物福利是一个主要的问题。近年来人们对动物福利法规及其相关方面的科学研究日益增多。由于家禽福利状况堪忧,导致标准化家禽生产的话题被关注。选育的影响经常遭到质疑。事实上,在进行商业选育的最初,很少考虑家禽的适应能力,因此出现了某些性状的退化。但是现在,对福利相关性状和遗传选育的越来越关注,     

Recovery threshold of Toxocara canis eggs from soil

The purpose of this study was to evaluate the threshold of Toxocara canis eggs form soil samples through utilisation of a centrifuge-flotation technique (CFT). Aliquots of soil (1 g each) were artificially contaminated with known numbers of T. canis eggs (1, 10, 25, 50, 100, and 200 eggs). The threshold was evaluated based on a CFT using zinc sulphate (Zn₂SO₄) and sodium nitrate (Na₂NO₃) solutions at a specific gravity of 1.20. The number of eggs recovered was directly proportional to the number of eggs employed to seed the soil. Both solutions enabled full recovery of samples containing merely three eggs; only Zn₂SO₄ demonstrated efficiency in soil contaminated with a single egg. A recovery rate of 100% was obtained for all tests with samples containing 10 and 25 eggs for Zn₂SO₄ and Na₂NO₃, respectively_. There was no difference in the mean number of recovered eggs regarding either the efficacy of the solutions or the repetition of evaluations in the same trial (p > 0.05). Therefore, the CFT is efficient for the detection of Toxocara eggs, even in samples containing low egg numbers.     

Postpartum Ovarian Activity and Serum Estradiol-17beta Level in Thai Crossbred Native Mares

To study the postpartum ovarian activities for investigation of first postpartum oestrus, twenty-five Thai crossbred native mares were monitored after parturition by oestrous detection, transrectal palpation and reproductive ultrasonography. Blood samplings were also taken for estradiol-17beta (E2) analysis. The first ovulation occurred within 20 days postpartum in 92% (23/25) of the mares. The mean intervals of foaling to first oestrus and to first ovulation were 10.3 +/- 2.9 and 13.4 +/- 2.6 days (mean +/- SD) respectively. Serum E2 increased from 7.0 +/- 2.9 to a peak of 10.8 +/- 3.3 pg/ml (mean +/- SD) at 2 days before ovulation. In conclusion, from the study, it can be stated that the postpartum breeding management should be considered after day 10 postpartum by careful examination of ovarian activity with various methods. However, the uterine condition should be also estimated associated with the ovarian activity after parturition which may increase breeding performance and foal production.     

The potential contribution of separation technologies to the management of livestock manure

Separation processes have a distinct role in the management of livestock slurries, but it is important to recognise their limitations. Such technology can direct certain manure components into a small volume of a concentrated stream which is useful for the production of organic products in subsequent processes. Equipment generally falls into systems based either on mechanical screening (which can produce a fibrous and seemingly dry product), filtration processes (producing a cake), or sedimentation leading to a sludge product. Although physical separation can remove up to 80% of the total solids content from livestock manures, this will only include a relatively small part of the soluble nutrient and of the reactive organic matter; this is particularly so where separation is based on screens. The complete removal of all suspended matter (total clarification) of an effluent is theoretically possible by settling — a decanter centrifuge will accelerate the process. This can remove most of the phosphorous, especially if coupled with chemical pre-treatment to raise the pH. However, the clarified stream still retains a significant polluting potential in terms of the residual nitrogen content (as ammonia) and potassium. Only membrane separation can greatly reduce the potassium concentration, but such technology is rarely suitable for the farm situation.     

Use of clinical information to predict the characteristics of bacteria isolated from clinical cases of bovine mastitis

Farmers recorded the clinical signs of cows with clinical mastitis and submitted milk samples for bacteriological examination, so that the clinical signs could be correlated with the bacteriological findings. Odds ratios for the demeanour of the cow, the appearance of the milk, milk yield, udder texture, and the administration of parenteral antibiotics were calculated for mastitis cases classified in terms of their microbiology as either enterobacteriaceae, major Gram-positive pathogens, minor pathogens, 'no growths' or 'all other pathogens'. Animals infected with enterobacteriaceae had the highest odds of being reported as having a reduced milk yield, swollen or hard udders, watery milk and/or being systemically sick. A logistic regression model was used to predict the Gram-staining characteristics of the bacteria causing clinical mastitis. The clinical findings found to be significant predictors in the model were the demeanour of the cow and its milk yield. The regression model was used as a basis for a predictive test. Using a test data set, the sensitivity of the test was 28 per cent, its specificity was 96 per cent, the positive predictive value was 74 per cent and the negative predictive value was 80 per cent. The overall accuracy of these predictions was 79 per cent.     

A dynamic model of metabolizable energy utilization in growing and mature cattle. I. Metabolizable energy utilization for maintenance and support metabolism

Models to predict heat production attributable to maintenance and support metabolism in growing and mature cattle were developed on the basis of three concepts. The first concept is that animals fed fixed amounts of the same diet achieve weight equilibrium over an extended feeding period, and that the ME consumed at weight equilibrium is the maintenance requirement. The second concept is that a part of the heat production resulting from ME consumed above the maintenance requirement is associated with an elevation of vital functions (support metabolism), and this heat production can be modeled as a function of the level of feeding. The third concept is that previous levels of nutrition affect current estimates of heat production, and that this impact can be modeled as a delayed response in heat production associated with support metabolism. Experimental data on feed consumption showed that maintenance requirements varied in simple proportion to BW, not only for different breeds of mature cattle at BW equilibrium, but also for calves and growing steers held at BW stasis. Experimental data in which different breeds of cattle achieved weight equilibrium when fed fixed amounts of a specific diet were used to estimate breed parameters associated with maintenance for 21 breeds of cattle and 15 biological types of crossbred cattle. Level of feeding was estimated as a multiple of the maintenance intake and used to model heat production associated with support metabolism. Other experimental data on growing cattle were used to estimate breed parameters for predicting heat production associated with support metabolism for 21 breeds of cattle and 15 biological types of crossbred cattle. A distributed lag function was used to model the delayed response in heat production associated with support metabolism with changes in plane of nutrition. The models were tested by simulating experimental data for three breeds of weaned steers finished on high-energy diets. Results for the total heat production associated with maintenance and support metabolism expressed on a unit BW basis showed a similar response with stage of maturity when compared with other experimental data.     

Growth hormone modulates cholecalciferol metabolism with moderate effects on intestinal mineral absorption and specific effects on bone formation in growing dogs raised on balanced food

The aim of the study was to investigate the influence of growth hormone (GH) on Vitamin D3 metabolism and the subsequent effects on calcium (Ca) homeostasis and skeletal growth in growing dogs. A group of Miniature Poodles received supraphysiological doses of GH (GH group; n = 6; 0.5 IU GH per kg body per day) from 12 to 21 weeks of age and was compared with a control placebo-treated group (n = 8). Biologic activity of GH in the GH compared to the control group was indicated by (a) the 2.5- to 3.5-fold increase in the plasma concentrations of insulin-like growth factor I (IGF-I), (b) the increased production of 1,25-dihydroxycholecalciferol as indicated by the significantly increased plasma 1,25-dihydroxycholecalciferol concentrations and the 12.9-fold increase in renal 1alpha-hydroxylase gene expression, and (c) the inhibited production of 24,25-dihydroxycholecalciferol as indicated by the significantly lower plasma 24,25-dihydroxycholecalciferol concentrations and the similar levels of renal 24-hydroxylase gene expression. Despite the distinct effects on Vitamin D(3) metabolism in the GH group, there were only moderate effects on the intestine, i.e. at 20 weeks of age there was a significant increase of 14.4 and 5.6% in fractional absorption of Ca and phosphate (Pi), respectively, compared to the control group. GH administration resulted in significantly elevated glomerular filtration rate, with no differences in Pi urine excretion as a result of a concomitant increase in the tubular reabsorption of Pi. GH had only limited disturbing effects on endochondral ossification as indicated by the maintenance of the regularity of the growth plates. However, GH had specific anabolic effects on bone formation without concomitant effect on bone resorption that may result in disorders of skeletal remodeling and manifestation of enostosis.