Resource Allocation in a Breeding Program for Phosphorus Concentration in Maize Grain

Abstract

When beef cattle (Bos taurus) are fed grain of maize (Zea mays L.) in which the concentration of phosphorus (P) exceeds the animal's need for this element, the excess P is excreted in the feces. Spreading this manure on cropland increases the potential for P pollution of surface waters by run‐off. Experiments were undertaken to determine the relative magnitudes of genotypic and nongenotypic variances of P concentration in maize grain (P‐Gr) to assess the ability to select maize genotypes in which this trait more closely matches the dietary need of beef cattle. Genetic variability was found in a population developed from a cross of Illinois High Protein (IHP) × Illinois Low Protein (ILP). Because of few low P‐Gr segregates, the IHP × ILP population was not considered a good breeding source for this trait. Nongenetic sources of variance were significant but small compared with genotypic variances. Broad‐sense heritability (H) for P‐Gr among S1 family means in the IHP × ILP population was estimated at 0.82. This high value suggested that this trait would respond to selection. A comparison of mean values of S1 families selected on the basis of performance in 2000 or in 2001 alone to those selected on the basis of 2‐yr data suggested that the loss in efficiency resulting from selecting on 1‐yr data would be only approximately 5%.