D'Eath, R. B. 2002. Individual aggressiveness measured in a resident intruder test predicts the persistence of aggressive behaviour and weight gain of young pigs after mixing. Appl. Anim. Behav. Sci. 77:267-283.
Dudink Suzan, Helma Simonse, Inge Marks, Francien H. de Jonge and Berry M. Spruijt. 2006. Announcing the arrival of enrichment increases play behaviour and reduces weaningstress- induced behaviours of piglets directly after weaning. Appl. Anim. Behav. Sci. 101:86-101.
Ekkel, E. D., B. Savenije, W. C. P. Schouten, V. M. Wiegant and M. J. M. Tielen. 1997. The effects of mixing on behavior and circadian parameters of salivary cortisol in pigs. Physiol. Behav. 62:181-184.
Forbes, J. M. 1995. Voluntary food intake and diet selection in farm animals. CAB International, Wallingford, Oxon, UK
Fraser, D., J. J. R. Feddes and E. A. Pajor. 1993. The relationship between creep feeding behavior of piglets and adaptation to weaning: effect of diet quality. Can. J. Anim. Sci. 74:1-6.
Gardner, J. M., I. J. H. Duncan and T. M. Widowski.. 2001. Effects of social "stressors" on belly-nosing behavior in early-weaned piglets: is belly-nosing an indicator of stress? Appl. Anim. Behav. Sci. 74:135-152.
Glatz, P. C. 2001. Effect of different lighting sources on behavior and growth of weanling pigs. Asian-Aust. J. Anim. Sci. 14:280-287.
Gonyou, H., E. Beltranena, D. Whittington and J. Patience. 1998. The behavior of pigs weaned at 12 and 21 days of age from weaning to market. Can. J. Anim. Sci. 78:517-523.
Haskell, M. F., M. T. Wemelsfelder, M.T., Calvert S. Mendl, Lawrence, A.B. 1996. The effect of substrate-enriched and substrate impoverished environments on the diversity of behavior in pigs. Behavior. 133:741-761.
Hessel, E. F., K. Reiners and A Van den Weghe. 2006. Socializing piglets before weaning: Effects on behavior of lactating sows, pre- and postweaning behavior, and performance of piglets. J. Anim. Sci. 84:2847-2855.
Hicks, T. A., J. J. McGlone, C. S. Whisnant, H. G. T. Kattesh and R. L. Norman. 1998. Behavioral, endocrine, immune, and performance measures for pigs exposed to acute stress. J. Anim. Sci. 76:474-483.
Hotzel Maria, Jose, Luiz Carlos Pinheiro Machado F, Fernando Machado Wolf, Osmar Antonio, Dalla Costa. 2004. Behaviour of sows and piglets reared in intensive outdoor or indoor systems. Appl. Anim. Behav. Sci. 86:27-39.
Jeon, J. H., S. C. Yeon, S. Kim, D. H. Kim and H. H. Chang. 2006. Assessment of the non all-in all-out system and the all-in allout system for sows and their suckling piglets. Asian-Aust. J. Anim. Sci. 19:909-914.
Johnson, A. K., J. L. Morrow-Tesch and J. J. McGlone. 2001. Behavior and performance of lactating sows and piglets reared indoors or outdoors. J. Anim. Sci. 79:2571-2579.
Kojima, M., H. Hosoda, Y. Date, M. Nakazato, H. Matsuo and K. Kangawa.. 1999. Ghrelin is a growth hormone releasing acylated peptide from stomach. Nature 402:656-660.
Main, R. G., S. S. Dritz, M. D. Tokach, R. D. Goodband and J. L. Nelssen. 2004. Increasing weaning age improves pig performance in a multisite production system. J. Anim. Sci. 82:1499-1507.
Mateo, R. D., J. L. Morrow, J. W. Dailey, F. Ji and S. W. Kim. 2006. Use of $\delta$-aminolevulinic acid in swine diet: effect on growth performance, behavioral characteristics and hematological/immune status in Nursery pigs. Asian-Aust. J. Anim. Sci. 19:97-101.
Nakazato, Masamitsu, Murakami, Noboru, Date, Yukari, Kojima, Masayasu, Matsuo, Hisayuki, Kangawa, Kenji and Shi Matsukura. 2001. A role for ghrelin in the central regulation of feeding. Nature 409:194-198.
Olesen, L. S., C. M. Nygaard, T. H. Friend, D. Bushong, D. A. Knabe, K. S. Vestergaard and R. K. Vaughan. 1996. Effect of partitioning pens on aggressive behaviour of pigs regrouped at weaning. Appl. Anim. Behav. Sci. 46:167-174.
Pettigrew, J. E., L. J. Johnston, G. C. Shurson and J. D. Hawton. 1994. Feeding nursery pigs. Proceedings, Pre-Conference Nutrition Seminar, American Associaiton of Swine Practitioners, Rosemont, IL, pp. 1-36.
Salfen, B. E., J. A. Carroll and D. H. Keisler. 2004. Effects of exogenous ghrelin on feed intake, weight gain, behavior, and endocrine responses in weaning pigs. J. Anim. Sci. 82:1957-1966.
Tammy, M. Donaldson, Ruth C. Newberry, Marek Spinka and Sylvie Cloutier. 2002. Effects of early play experience on play behavior of piglets after weaning. Appl. Anim. Behav. Sci. 79:221-231.
Tan, S. S. L. and D. M. Shackleton. 1990. Effects of mixing unfamiliar individuals on the growth and production of finishing pigs. Anim. Prod. 52:201-226.
Tolle Virginie, Marie-Helene Bassant, Philippe Zizzari, Frederique Poindessous-Jazat, Catherine Tomasetto, Jacques Epelbaum and Marie-Therese Bluet-Pajot. 2002. Ultradian rhythmicity of ghrelin secretion in relation with GH, feeding behavior, and sleep-wake patterns in rats. Endocrinol. 143:1353-1361.
Worobec, E. K., I. J. H. Duncan and T. M. Widowski. 1999. The effects of weaning at 7, 14, and 28 days on piglet behaviour. Appl. Anim. Behav. Sci. 62:173-182.