鸡腺胃型传支的疾病模型确定 Ⅰ．临床症状及眼观病理变化规律

对1日龄雏鸡人工接种IBV腺胃型致病株（弱毒株），同时，在实验过程中，对鸡群人为地施以不同的应激因素，如降低温度、饥饿、不良通风和高密度饲养使鸡只感染发病，观察攻毒后的临床症状，同时定期随机剖检攻毒活鸡和病死鸡，观察眼观病理变化，并记录，鸡群表现畏寒，扎堆，不爱运动，呼吸有锣音，张口呼吸，采食和饮水明显减少，拉黄白色稀粪，发病中后期极度消瘦，鸡群发育极不整齐，腺胃肿胀，中后期萎缩，贫血，肺脏淤血，内脏痛风，肾脏尿酸盐沉积，结果表明，攻毒后4－5日开始出现临床症状，8－9日达到高峰，随后症状逐渐减轻，1天多以后，对照组也出现相似的临床症状及眼观病理变化，说明此病的传播性很强。     

Positron tomography and nuclear magnetic resonance imaging

Noninvasive imaging methods for medical diagnosis and biological investigations, have evolved from qualitative radiological techniques to quantitative methods of measuring biochemical and physiological processes in human body. In particular, new developments in emission tomography, nuclear magnetic resonance imaging, and in vivo spectroscopy offer new horizons for medical research and clinical activities. These methods and their potentials are reviewed and contrasted.     

Estimate of the sensitivity of an ELISA used to detect Johne's disease in Victorian dairy cattle herds

OBJECTIVE: To estimate the sensitivity of the ELISA used in dairy cattle herds participating in the Victorian Bovine Johne's Disease Test and Control Program (TCP). PROCEDURE: The percentage of ELISA reactors in age and test cohorts was estimated from age-specific test data derived from TCP herds with long testing histories. Age-distribution data from production-tested herds enabled estimation of reactor rates in animals that were culled or died. RESULTS: ELISA sensitivities at the first test round in herds achieving five, six and seven annual herd tests were 16.1, 14.9 and 13.5% respectively. The ELISA sensitivity in 2, 3 and 4-year-old animals at the first test round in herds testing seven times was 1.2, 8.9 and 11.6% respectively but remained between 20 and 30% in older age-groups. CONCLUSION: The sensitivity of the ELISA is considerably lower than previous estimates, probably because previous estimates were predominantly measured against faecal culture, which has subsequently been shown to have low sensitivity itself, and did not appreciate the long period that appears to precede detectable faecal excretion in most animals.     

Association of cow and quarter-level factors at drying-off with new intramammary infections during the dry period

Our objective was to describe cow and quarter-level factors associated with drying-off, and to evaluate their impacts on new intramammary infections (IMI) during the dry period. Data from 300 cows in five research herds were collected starting 2 weeks prior to scheduled drying-off. Variables of interest included daily milk production, teat-end integrity, formation of the teat-canal keratin plug, and quarter-milk bacteriological culture results. Overall, 11% of quarters developed new IMI in the dry period; this varied by herd, parity and time of the study. Most new IMI were caused by environmental streptococci and coliform organisms (34 and 30%, respectively). Quarters that had a cracked teat-end had higher odds of developing new infections than those without cracks (15 and 10%, respectively). Quarters that formed a keratin plug early in the dry period had a lower odds than those that did not close (10 and 14%, respectively). After 6 dry weeks, 23% of quarters were still open. The hazard of quarters closing if milk production on the day prior to drying-off was >21 kg 1.8-times less.     

Investigations of energy metabolism in weanling barrows: the interaction of dietary energy concentration and daily feed (energy) intake

Much of our understanding of energy metabolism in the pig has been derived from studies in which the energy supply was controlled through regulated feed intake. In commercial situations, where ad libitum feeding is practiced, dietary energy concentration, but not daily feed intake, is under producer control. This study evaluated the interactive effects of dietary energy concentration and feeding level (FL) on growth, body composition, and nutrient deposition rates. Individually penned PIC barrows, with an initial BW of 9.5 +/- 1.0 kg, were allotted to 1 of 9 treatments in a 3 x 3 factorial arrangement plus an initial slaughter group (n = 6) that was slaughtered at the beginning of the trial. Three NE concentrations (low, 2.15; medium, 2.26; and high, 2.37 Mcal of NE/kg) and 3 feeding levels (FL: 100, 80, or 70% of ad libitum access to feed) were investigated. Daily feed allowance for the restricted-fed pigs was adjusted twice per week on a BW basis until completion of the experiment at 25 +/- 1 kg of BW. Average daily gain, ADFI, and G:F were unaffected by NE (mean = 572 g, 781 g, and 0.732 g/g, respectively). Average daily gain and ADFI, but not G:F, increased (P < 0.05) with FL. Empty body lipid concentration increased with dietary NE concentration and with FL; a significant (P < 0.01) interaction revealed that empty body lipid concentration increased most rapidly as ADFI increased on the highest energy diet. Empty body lipid concentration was greatest in pigs with ad libitum access to the high-NE diet. Empty body protein concentration decreased with increasing NE (P < 0.05) but was not affected by FL. Empty body protein deposition (PD) increased with increasing FL (P < 0.001), but not with NE. Empty body lipid deposition (LD) and the LD:PD ratio increased (P < 0.01) in pigs with ad libitum access to the high-NE diet. In conclusion, NE did not interact with FL on growth, body protein concentration, or PD, suggesting that the conclusions regarding energy utilization obtained from experiments using restricted feed intake may not easily be applied to pigs fed under ad libitum conditions. The interactive effects of NE and FL on body lipid concentration, LD, and the LD:PD ratio indicate that changes in dietary energy concentration alter the composition of gain without necessarily changing overall BW gain. Consequently, the composition of gain is an important outcome in studies on energy utilization.