Short communication: Promotion of glucagon-like peptide-2 secretion in dairy calves with a bioactive extract from Olea europaea. 
Diarrhea episodes in dairy calves involve profound alterations in the mechanism controlling gut barrier function that ultimately compromise intestinal permeability to macromolecules, including pathogenic bacteria.  Intestinal dysfunction models suggest that a key element of intestinal adaptation during the neonatal phase is the nutrient-induced secretion of glucagon-like peptide (GLP)-2 and associated effects on mucosal cell proliferation, barrier function, and inflammatory response.  Bioactive molecules found in Olea europaea have been shown to induce the release of regulatory peptides from model enteroendocrine cells.  The ability to enhance GLP-2 secretion via the feeding of putative GLP-2 secretagogues is untested in newborn calves.  The objectives of this study were to determine whether feeding a bioactive extract from Olea europaea (OBE) mixed in the milk replacer (1) can stimulate GLP-2 secretion beyond the response elicited by enteral nutrients and, thereby, (2) improve intestinal permeability and animal growth as well as (3) reduce the incidence of diarrhea in preweaning dairy calves.  Holstein heifer calves (n = 60) were purchased, transported to the research facility, and blocked by body weight and total serum protein and assigned to 1 of 3 treatments.  Treatments were control (CON), standard milk replacer (MR) and ad libitum starter; CON plus OBE added into MR at 30 mg/kg of body weight (OBE30); and CON plus OBE added into MR at 60 mg/kg of body weight (OBE60).  The concentration of GLP-2 was measured at the end of wk 2.  Intestinal permeability was measured at the onset of the study and the end of wk 2 and 6, with lactulose and d-mannitol as markers.  Treatments did not affect calf growth and starter intake.  Compared with CON, administration of OBE60 increased the nutrient-induced response in GLP-2 by about 1 fold and reduced MR intake during the second week of study.  Throughout the study, however, all calves had compromised intestinal permeability and a high incidence of diarrhea.  The GLP-2 response elicited by OBE60 did not improve intestinal permeability (lactulose-to-d-mannitol ratio) and incidence of diarrhea over the course of the preweaning period.  The response in GLP-2 secretion to the administration of OBE reported herein warrants further research efforts to investigate the possibility of improving intestinal integrity through GLP-2 secretion in newborn calves.