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Patlola, Jag Jeevan Reddy

Animal Sciences

2007

MS

There is scant scientific evidence on which to base recommendations for the age at which vaccination against viral respiratory infections should be given to effectively stimulate the immune system of young calves. Calf raisers are implementing various vaccine protocols that lack scientific support. This research was designed to evaluate the difference between the immune responses of young dairy calves vaccinated at two different ages. In this experiment, health and immune responses of young calves vaccinated at two weeks or six weeks of age were determined. This study was performed with 20 Holstein heifer calves, three days of age at the time of enrollment, under field conditions, at Diamond Hill farm in Sheldon, Vermont. Calves (n=20) weighing 40 to 48 kg at birth were assigned to one of the two groups based on their age. Group#1 had ten age matched calves of which seven were vaccinated at six weeks of age (V6) and three were not (C6). Group#2 also had ten calves of which seven were vaccinated at two weeks of age (V2) and three were not (C2). To reduce the variability due to time of vaccination, calves in Group#1 were enrolled 4 week before Group#2 calves, such that all calves received vaccination simultaneously. Treatment groups were vaccinated with two ml of Vista 5 vaccine subcutaneously. Vista 5 is a modified live virus vaccine formulated with IBR, BVD1 and 2, PI-3, and BRSV strains. Sixty ml of blood was collected from the jugular vein at various time points. For Group #1 blood sampling was done at six and nine weeks of age and for Group#2 at two, five and nine weeks of age. Immune parameters measured included lymphocyte proliferation using various vaccines as antigens (Vista 5, IBR, and BRSV), total serum IgG and Vista 5-sp-ecific IgG. Proliferative response in six-week-old calves was much greater compared to two-weekold calves. The intensity of proliferation with Vista 5 was more pronounced as compared with the other antigens. Circulating levels of Vista 5 IgG were higher in calves vaccinated at 6 weeks of age when compared to age-matched calves and calves vaccinated at 2 weeks of age. There was no effect of vaccination on body weights and total serum IgG. The results of this study demonstrated that vaccination at six weeks of age produces a significant cell mediated and humoral response as compared to the response of two-week-old calves. The results of this study along with in vivo challenge studies will be helpful in improving vaccination protocols in young calves.