It is well known that newborns require colostrum and there is increasing interest in the systemic effect of feeding bovine colostrum (BC) to adult humans. However, there are no reports of systematic evaluations into the impact of colostrum on the canine immune response. Thus the aim of this study was to assess the effect on canine immune response of using BC as a dietary supplement. The study involved twenty-four dogs with a mean age 2.5 years, randomised into two groups. During the 'pre-test' phase, lasting eight weeks, both groups were fed a nutritionally complete diet and given a canine distemper virus (CDV) vaccine at the end. During the subsequent test phase, lasting forty weeks, a 'test group' was switched to a diet supplemented with 0.1% spray-dried BC, whilst a ‘control group’ remained on the original diet. Vaccine-specific plasma IgG levels were used to assess the dogs’ response to the CDV vaccine. IgA levels in faeces provided a measure of gut-associated lymphoid tissue response and temporal temperature gel electrophoresis was used to evaluate gut microbiota. The findings showed dogs in the test group when compared with those in the control group had: significantly higher vaccine response; higher levels of faecal IgA and significantly increased gut microbiota diversity and stability. The conclusion from this study is that using BC as a dietary supplement significantly affects immune response in dogs.