FORAGE QUALITY OF MAIZE GENOTYPES SELECTED FOR EXTREME FIBER CONCENTRATIONS

An understanding of the factors and relationships affecting whole plan t digestibility is needed to improve the nutritional quality of maize (Zea mays L.) forage. The objectives of this study were to: (i) determ ine the ranges among 24 maize genotypes for fiber composition and dige stibility of stover and whole plant forage, and (ii) determine the rel ationships between fiber composition and digestibility. Twenty-four S- 0.1 families (S-0-derived families in S-1) exhibiting a range in neutr al detergent fiber (NDF) and lignin at mid-flower, were testcrossed to two commercial inbred lines (FR23 and LH74) to form two groups of F-1 hybrids. A third experimental group was created by self pollinating t he S-0.1 families to form S-0.2 families. These germplasms were evalua ted in three Wisconsin environments. Ranges in S-0.2 family means for fiber and digestibility were: NDF, 439 to 582 g kg(-1) for the whole p lant and 579 to 654 g kg(-1) for the stover; and in vitro true digesti bility (TVTD), 714 to 820 g kg(-1) for the whole plant and 689 to 757 g kg(-1) for the stover. Narrower ranges were observed among LH74 and FR23 testcrosses. For S-0.2 families, correlation coefficients for sto ver IVTD with stover NDF and lignin were -0.76 and -0.85, respectively . Correlation coefficients for whole plant IVTD with stover IVTD and l ignin of S-0.2 families were 0.44 and -0.49, respectively. The results of this study show that (i) significant variation exists for nutritio nal quality traits of the stover and whole-plant forage and (ii) stove r quality is an important factor influencing whole-plant nutritional q uality within the germplasm studied.