Following from studies on the inflammatory response to clostridial vaccines in feedlot cattle which reported a post-vaccination rise in serum Hp [20] it was decided to assess the use of the routine husbandry practice of immunising new-born lambs against infection with bacteria such as clostridia and pasteurella (Heptavac PTM) as a means to quantify the dynamic acute phase protein response. This evidence concerns the gene HP and infection.