- Responses to maternal GH or ractopamine during early-mid pregnancy are similar in primiparous and multiparous pregnant pigs. Gatford, K.L., De Blasio, M.J., Roberts, C.T., Nottle, M.B., Kind, K.L., van Wettere, W.H., Smits, R.J., Owens, J.A. J. Endocrinol. (2009)