Effects of dietary protein concentration on the response of growing chicks to methionine.

1. Experiments were conducted independently at two stations to measure the requirement for methionine in chick diets with crude protein (CP) varying in 8 steps from 140 to 280 g/kg diet (experiment 1) or from 90 to 300 g/kg (experiment 2). 2. Protein composition was the same at all protein concentrations within a trial. The diet was designed to be first-limiting in methionine and DL-methionine was added to provide 5 ratios of methionine to CP at each protein concentration. 3. Methionine required for maximum growth rate or maximum efficiency of food utilisation was estimated at each protein concentration by fitting a quadratic regression equation to the relevant data. The requirement was also estimated by fitting the Reading model to data for growth rate and methionine intake. 4. In both trials and by all three methods of estimation, the methionine requirement (g/kg diet) for maximum performance increased as a linear function of dietary CP concentration and nearly in direct proportion to CP. 5. It is concluded that diets which contain surplus protein, beyond that needed to maximise growth rate or food efficiency, need supplementation with methionine beyond that required when dietary protein is just adequate. A suitable rule for practical formulation is that methionine concentration in chick diets should be not less than 0.025 times the dietary CP concentration.     

Response of the badger (Meles meles) to infection with Brucella abortus

Three badgers exposed to conjunctival instillation of Brucella abortus strain 544 developed a mild subclinical infection accompanied by the production of agglutinating and complement fixing antibodies. Six months after inoculation, the infection could not be detected in one badger and was confined to lymphoid tissue in the other two. No cell mediated immune response to B abortus antigens could be detected by in vitro lymphocyte transformation tests or intradermal tests for delayed hypersensitivity during the observation period.     

Management and environmental factors associated with annual sow culling rate: A path analysis

The relationships between management and environmental factors and annual sow culling rate were investigated in 152 Minnesota swine breeding herds. Data were obtained through a postal survey. A general path model was hypothesized to describe relationships among variables. Multiple least-squares and logistic regressions were used to test the statistical significance of pathways. The associations between the indepen variables and the annual culling rate (ACR) were decomposed into direct, indirect, and common cause associations.

The mean ACR of the 152 farms was 39% ± 2% rm(SE). Using path-analysis techniques, only the type of flooring during gestation, the size of the herd and the lactation length had a direct relationship with ACR. The type of housing during gestation and farrowing were related indirectly to the ACR. Their association was mediated by the type of flooring during gestation and the weaning age. Herds housing their sows in total confinement during gestation were most likely to keep them on partially or totally slatted floors which were associated with a higher ACR. Sows kept in crates during the farrowing period were more likely to have a short lactation length which was associated with a higher ACR.

Most associations between the use of preventive veterinary services and the ACR were due to association with other variables. Herds using veterinary preventive medicine were most likely to have a short lactation length, a large number of females, and sows housed in total confinement during gestation and in crates during the farrowing period. All of the aforementioned variables were associated with a high ACR.

The relationships of other management and environmental factors with the ACR were due to common cause associations. These factors included having the sows individually identified, using a more comprehensive recording system, mainly a hand-mating system, testing regularly for pregnancy and housing sows in total confinement during the breeding period. The strongest associations with the ACR were the type of flooring during gestation and the size of the herd.     

Electrophoresis Study of Extracts of Submaxillary Salivary Glands from Naturally Rabid Dogs

Rabies virus in submaxillary salivary glands from naturally infected dogs was investigated by a paper electrophoresis technique, and the virus activity was quantitated by intracerebral titration in mice. Extracts from these salivary glands were found to contain (a) 10⁴ to 10⁶ mouse ICLD ₅₀ units of wild rabies seed and (b) a protein complex that migrated electrophoretically in the albumin band and more conspicuously in the beta and gamma bands of normal horse serum. The protein complex was interpreted to comprise aggregates of neutralizing antirabies antibody.     

世界猪病的发展与演变(续)

17 群体水平上的复合病因网络 在集约化生产系统中,我们面临的大多数疾病都有着复杂的成分因素。其中一些可能是必要因素,如果没有他们的存在疾病也就无从发生,但当他们独自起作用时却并不是充分原因。“Koch’s”假设有其局限性,只有对疾病病因作现场检验时才起作用。那些病原单独存在并且是必要充分原因的疾病通常是最易     

Effects of protein concentration on responses to dietary lysine by chicks

Chicks were fed on diets varying in crude protein (CP) content (140 to 280 g/kg diet) in either 8 steps, experiment 1, or 6 steps, experiment 2. Protein composition was held constant in each experiment. At each protein concentration, 5 (experiment 1) or 6 (experiment 2) concentrations of lysine were tested, ranging from 40 to 60 g/kg CP. Growth rate and efficiency of food utilisation to 21 d of age responded to increasing dietary protein contents up to about 230 g CP/kg. An estimate of lysine requirement at each protein concentration was obtained by fitting a quadratic curve to the response data and calculating the dose of lysine (g/kg CP) needed to maximise either growth rate or gain/food ratio. Although no growth response to dietary protein was obtained between 240 and 280 g CP/kg, the amount of lysine needed to maximise growth and gain/food ratio over this range increased systematically when expressed as g/kg diet, but remained constant if expressed as g/kg CP. The regression of lysine required (g/kg diet) for maximum performance (growth or food efficiency) on CP (g/kg diet) was strictly linear for both responses in both experiments throughout the entire range studied (140 g CP/kg to 280 g CP/kg). The estimated lysine requirement was 0.053 of the CP in experiment 1 and 0.055 of the CP in experiment 2. It is concluded that a fixed ratio of lysine to protein should be specified in practical diet formulation, rather than a minimum dietary concentration of lysine. This would ensure that, if the dietary protein content rises above a prescribed minimum value in least-cost formulation, an appropriate adjustment will automatically be made to the lysine content of the solution.     

Enzootic pneumonia: comparison of cough and lung lesions as predictors of weight gain in swine.

A prospective cohort study was undertaken in a commercial swine herd to determine the relationship between weight gain and the occurrence of enzootic pneumonia (EP). Estimates of the association between EP and weight gain were obtained from multiple linear regression models, using coughing episodes or slaughter checks as indicators of EP status. Models were estimated for pigs in 2 different age groups: roasters (n = 1084, sold at 32 to 50 kg) and market hogs (n = 1162, sold at 100 to 110 kg). The relationship between presence of lung lesions at slaughter and previous coughing episodes was also investigated. Throughout the study period, clinical evaluations were performed weekly, and coughing episodes recorded for each pig. Lungs were inspected at slaughter, and scores were expressed as the percentage of the lung with gross pneumonic lesions. Coughing and lung scores were significantly correlated, after adjusting for other covariates (R = 0.32 and 0.59, respectively, for market hogs and roasters). However, the agreement beyond chance between coughing history and lung lesions at slaughter was poor among both roasters and market hogs (kappa = 0.17 and 0.07, respectively). Although very specific, weekly assessment of coughing was not a sensitive indicator of lung lesions at slaughter. In multiple regression, lung score was a highly significant predictor of lower final weight in pigs of both age groups (P < 0.001 in the selected regression models).(ABSTRACT TRUNCATED AT 250 WORDS)     

Estimate of economic impact of fowl cholera in turkeys in Georgia in 1986

Information gathered from cases of fowl cholera (FC) in commercial turkey flocks through case records, flock records, and telephone and mail surveys was used to estimate disease costs. The cost to the Georgia commercial turkey industry in 1986 from preventive measures, treatment of outbreaks, and production losses from the disease was estimated at $634,545. The cost of FC per kg of live production was estimated to be $0.015.