No abstract

Natural human interferon-alpha (nHuIFN-alpha) from three sources was given orally to 368 calves experiencing a natural outbreak of bovine respiratory disease complex (BRDC). In one study, 200 calves were given one treatment daily for 3 days of placebo or 20, 200, or 2,000 IU of nHuIFN-alpha before shipment. Calves treated with 20 or 200 IU had a significant (p < 0.05) weight gain benefit for the first 21 days in the feedlot, if they had rectal temperatures <40 degrees C when treated with nHuIFN-alpha. In a second trial, 168 mixed-breed calves (five groups randomized to 31-36 calves/group) were treated with one dose of placebo or 200 or 400 IU of nHuIFN-alpha after shipment to the feedlot. Using this regimen, a dose of 200 IU per calf significantly (p < 0.08) decreased the number of sick calves per group and delayed development of BRDC. Results of these studies demonstrate that oral administration of nHuIFN-alpha, which may partially mimic the nasally secreted IFN response reported during BRDC, may be beneficial in cattle.

Three groups of calves were inoculated intranasally with infectious bovine rhinotracheitis (IBR) virus, to determine any effects of a 3-day fast on virus replication and interferon (IFN) production measured in nasal secretions (NS). One group ("fasted") was inoculated 24 h after onset of the fast and another ("refed") at the end of fasting, immediately before refeeding. A third ("control") group was inoculated but not fasted. In fasted calves, overall mean virus excretion (during the first 5 postinoculation days) did not differ from that in control calves, though average virus excretion was higher on days 3 and 4, 24 and 48 h after refeeding. In refed calves, overall mean virus excretion was lower (p less than 0.05), yet on day 5 these calves secreted two times more IFN than nonfasted calves. Analysis of the overall data (all 5 postinoculation sampling days) showed that fasted calves produced more IFN (p less than 0.05), with IFN titers sometimes exceeding 1000, than either control nonfasted calves or refed calves. We conclude that fasting enhanced the ability of calves to produce IFN, and this did not result from increased IBR virus replication.

Seventeen calves (Angus, Hereford, and Angus-Hereford crosses) weighing 120-200 kg, were starved for 3 days and inoculated intranasally with a strain of IBR virus after 1 day or 3 days of food deprivation. Although clinical signs of disease were mild in all calves, the signs appeared more severe than those reported by others using the same strain of virus possibly due in part to the use of intranasal inoculation by aerosol vs instillation. Neutralizing antibody response after virus inoculation did not differ beween groups. Of the 17 calves, 16 developed significant increases (seroconversion of 4-fold increase in titre) in IBR serum antibodies. Serum neutralizing antibodies in 3 calves at inoculation did not prevent them from excreting substantial amounts of virus for ? 5 days after virus inoculation. Lymphocytes from fasted and nonfasted calves had similar (essentially negative) blast transformation responses, except 1 fasted seropositive calf (sensitised animal) that had a high stimulation index. Some dehydration was observed in fasted calves, indicated by significant increase in haematocrit. In only 1 group did serum cortisol levels rise significantly, mean values peaking at the end of fasting at the time of inoculation; thereafter, mean values tended to decline. Although the 3-day fast significantly affected some serum and blood components, it did not adversely affect the immune response of calves. One fasted calf developed a significant cell mediated immune response to inactivated IBR virus during infection. It is concluded that acute nutritional deprivation may not necessarily increase the susceptibility of calves to viral infections nor adversely affect their immune response after vaccination. This report represents a portion of a dissertation submitted by the senior author to the graduate faculty of the University of Missouri in partial fulfillment of the requirements for the PhD degree. The authors thank Gary Krause and Mark Ellersieck for aid in statistical analysis and Gerald Buening for help in lymphocyte transformation tests.