Design of field trials for the evaluation of antibacterial products for therapy of bovine clinical mastitis

In this paper, the design and statistical analysis of field trials for the evaluation of the efficacy of clinical mastitis therapeutics is covered. First, general issues underlying the design of clinical trials are reviewed. These include bias and confounding; randomization and blocking; and study objectives and choice of the corresponding hypothesis. Specific issues in the design of clinical mastitis trials are also discussed. Selection of subjects is discussed with regard to choice of experimental units, identification of reference population and study population, inclusion and exclusion criteria, and sample size calculation. Next, a section on treatment administration and evaluation of cure reviews treatment, blinding, choice of response measure, as well as compliance, withdrawal, and early termination. The statistical analysis section addresses possible statistical models, treatment of confounding, and fixed vs. random effects. In conclusion, well-conducted clinical mastitis trials represent an invaluable, albeit difficult and expensive, effort to evaluate efficacy and tolerance under usual circumstances of use.     

The effect of 6‐ and 8‐hour light‐dark cycles on egg production and pattern of ovipositions

1. Two flocks of 60 laying hens were transferred from 14 h light (L): 10 h dark (D), to repeated 3L:3Dor4L:4D lighting schedules at 37 weeks of age. Egg production decreased slightly but egg weight and shell quality improved.

2. The intake of low‐calcium diet and of oyster shell were similar for each light period of each lighting regimen.

3. Ovipositions were distributed virtually at random throughout the day and the mean interval between successive eggs within a clutch was increased.

4. Reducing the total daily photoperiod from 12 to 6 h decreased daily food consumption.     

Blood enzyme activities in different breeds of geese.

1. Enzyme activities were studied in blood plasma from Rhenish, Italian, Landes and Masseubian geese. 2. Strains used for liver production (Landes, Masseubian) showed higher activities of aspartate transaminase (AST) [EC 2.6.1.1], alanine transaminase (ALT) [EC 2.6.1.2] and fructose aldolase (FRA) [EC 4.1.2.13] while breeds with high egg production (Rhenish, Italian) had higher activities of both alkaline phosphatase (ALP) [EC 3.1.3.1] and acid phosphatase (ACP) [EC 3.1.3.2]     

Studies of Mycoplasma mastitis in cattle. 6. Testing of Mycoplasma isolated from milk for udder pathogenicity

Strains of M. bovis, A. laidlawii, A. axanthum, and one unidentified strain of the family of mycoplasmataceae as well as altered secretion obtained from cows with mastitis were intracisternally applied in experiments and proved to be pathogenic to cattle udder. The results are likely to suggest the importance of mycoplasma isolated from the milk of mastitis cows to the aetiology of enzootic mastitis in three large dairy cattle stocks. Intravenous application of M. bovis and A. laidlawii caused neither mastitis nor mycoplasma secretion in the milk.