ORIGINAL ARTICLE Effects of variety, sowing season and maturity stage on ruminal phosphorus release from whole maize stover and its morphological fractions S. X. Tang 1,2 , L. X. Sheng 1 , C. S. Zhou 1 , Z. L. Tan 1 , H. Y. Liao 3 , M. Wang 1 , Z. H. Sun 1 , X. F. Han 1 and M. A. Bamikole 4 1 Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Changsha, Hunan 410125, China, 2 Graduate University of Chinese Academy of Sciences, Beijing 100049, China, 3 Department of Mathematics and Science, Hunan First Normal College, Changsha, Hunan 410002, China, and 4 Department of Animal Science, University of Benin, Benin City, Nigeria Introduction Phosphorus (P) is an important element for rumi- nants. The P requirement of microbes in the rumen is greater than that of the host animal (Preston and Pfander, 1964). Phosphorus depletion in the rumen could rapidly decrease cellulolytic activity (Komisarczuk et al., 1986), thereby decreasing diet utilisation and animal production (Georgievskii, 1981). On the other hand, there is an environmental concern with respect to P excretion by animals (Tayo and Tan, 2007). As one important dietary Keywords maize variety, sowing season, maturity, phosphorus, maize stover Correspondence Zhiliang Tan, Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Changsha P.O. Box 10 # , Hunan 410125, China. Tel: 86-731-4619702; Fax: 86-731-4612685; E-mail: zltan@isa.ac.cn Received: 30 March 2009; accepted: 09 September 2009 Summary An in situ degradation technique was used to investigate the effects of variety, season and maturity stage on ruminal Phosphorus (P) release from whole maize stover and morphological fractions from five varieties of maize (conventional maize, CM; sweet maize, SM; waxy maize, WM; high oil maize, HOM; and fodder maize, FM). Maize plants were har- vested in 2005, 17 and 31 days after tasselling and manually separated into leaf blade, leaf sheath, stem and husk. Results showed that the values of rapidly released P fractions (a), slowly released P fractions (b), rate constant of P release for fraction b (c) and effective disappearance (ED) of P were significantly influenced by variety, sowing season and maturity stage (p < 0.05). The ED of P in whole maize stover among the varieties decreased in the following order: FM (89.8%) > HOM (87.9%) > CM (87.0%) > SM (86.9%) > WM (83.9%). Advanced matu- rity stage increased (p < 0.001) the a and ED values of P in the leaf blade and leaf sheath, but decreased (p < 0.001) these parameters in the husk. The a fraction and ED of P were higher (p < 0.001) for maize sown in spring than those sown in summer. Significant (p < 0.05) inter- actions among variety, sowing season and maturity stage were noted in the a and ED values of P. Effective disappearance of morphological frac- tion varied significantly (p < 0.001) and followed the order: stem (90.3%) > leaf sheath (88.2%) > leaf blade (85.2%) > husk (84.9%). In conclusion, most of P in maize stover could be released in the rumen. The potential pollution resulting from P excretion in faeces may be alle- viated, when maize stover is largely used as the main forage source of ruminants. DOI: 10.1111/j.1439-0396.2009.00974.x Journal of Animal Physiology and Animal Nutrition 94 (2010) e49–e58 ª 2010 Blackwell Verlag GmbH e49