Effect of somatotropin on changes in milk-production and composition during coliform mastitis in periparturient cows.

The potential protective and therapeutic effects of bST during coliform mastitis in periparturient cows were evaluated. In a first study, 19 cows, classified as moderate or severe responders based on the respiratory burst activity of blood neutrophils, were treated with recombinant bST or vehicle 48 h after intramammary inoculation of Escherichia coli. Clinical status and changes in milk production and composition were compared in the four groups. In a second study, 8 cows received bST or vehicle 7 d before bacterial challenge. During mastitis, losses in milk production and compositional changes were most pronounced in infected glands and in severe responders. Milk production of bST cows recovered better than that of placebo cows. Recovery of milk components was accelerated in severe responders treated with bST, but not in moderate responders. Pretreatment of severe responders with bST enhanced milk production before infection, protected the mammary glands from excessive loss of milk during the subsequently induced coliform mastitis, and accelerated normalization of milk composition. In conclusion, the beneficial effects of bST upon normalization of milk production and composition in periparturient cows suffering from coliform mastitis seem to be restricted to the severe responders. In severe responders that had been treated with bST, changes observed during mastitis resembled those in moderate responders treated with the placebo

Effectiveness analysis of resistance and tolerance to infection

<p>Abstract</p> <p>Background</p> <p>Tolerance and resistance provide animals with two distinct strategies to fight infectious pathogens and may exhibit different evolutionary dynamics. However, few studies have investigated these mechanisms in the case of animal diseases under commercial constraints.</p> <p>Methods</p> <p>The paper proposes a method to simultaneously describe (1) the dynamics of transmission of a contagious pathogen between animals, (2) the growth and death of the pathogen within infected hosts and (3) the effects on their performances. The effectiveness of increasing individual levels of tolerance and resistance is evaluated by the number of infected animals and the performance at the population level.</p> <p>Results</p> <p>The model is applied to a particular set of parameters and different combinations of values. Given these imputed values, it is shown that higher levels of individual tolerance should be more effective than increased levels of resistance in commercial populations. As a practical example, a method is proposed to measure levels of animal tolerance to bovine mastitis.</p> <p>Conclusions</p> <p>The model provides a general framework and some tools to maximize health and performances of a population under infection. Limits and assumptions of the model are clearly identified so it can be improved for different epidemiological settings.</p