In the past T.E. Wittum has collaborated on articles with H.C. Voris and G.M. Rogers. One of their most recent publications is The influence of neonatal health on weaning weight of Colarado, USA beef calves☆. Which was published in journal Preventive Veterinary Medicine.
More information about T.E. Wittum research including statistics on their citations can be found on their Copernicus Academic profile page.