Respiratory tract infections in dairy calves from birth to breeding age

Detection by laboratory isolation and antibody responses

Abstract

This observational study followed 30 dairy heifers from birth to breeding to identify when exposure to potential respiratory pathogens occurred. Following the standard heifer development protocol for the dairy farm studied, heifers were housed in larger group pens, termed "groupings", based upon individual growth and development. Samples were collected at each grouping to determine when potential respiratory pathogens were acquired. Nasal swabs for viral and bacterial culture, peripheral blood leukocytes for virus isolation, and sera for antibody titers were collected and assayed three times (days 0, 7 and 14) at each grouping, beginning at 24-36 hours of age. Nasal bacterial isolates included Mannheimia haemolytica, Pasteurella multocida, Histophilus somni (formerly Haemophilus somnus) and Mycoplasma spp. M. haemolytica and P. multocida were occasionally isolated in the first 24-36 hours of life. Isolation of M. haemolytica and P. multocida increased substantially in the second and fourth groupings, respectively. Bovine herpesvirus-1 (BHV-1), parainfluenza-3 virus (PI3 V), M. haemolytica and Mycoplasma spp. were isolated with increased frequency when heifers were housed with nose-to-nose contact with adult cattle, and when clinical respiratory disease that responded to treatment occurred. Heifers were vaccinated with modified live virus vaccine while in hutches and at 5-6 months of age (third and fourth groupings). Colostrum-derived antibodies to viruses had diminished by the second grouping (age 95.2ñ25.4 days), and during that time PI3 V and BHV-1 were isolated. Viral neutralizing antibody titers did not significantly increase until after the second vaccination, which may have reflected interference from maternal antibody. Calves spontaneously developed antibodies to P. multocida between the 14th day in the hutch and the second grouping, and to M. haemolytica during the second (age 95.2ñ25.4 days) and third groupings (age 134.5ñ36.1 days). In conclusion, transmission of potential respiratory pathogens was documented in young dairy heifers despite commonly accepted health management programs, including vaccination.