THE RESPONSE OF BROILER CHICKEN TO DIET DILUTED WITH WHOLE WHEAT AT DIFFERENT AGES

Nitrate concentration in the soil at the start of the growing season is high because of mineralization of organic N during autumn and the addition of N fertilizer. It may be useful to exploit this N as much as possible. Therefore, nitrate uptake, assimilation and dry matter production among a range of barley cultivars were examined in a series of experiments utilizing a hydroponic system. Seedlings were grown at two rates of nitrates, i.e., 0 and 1.0 mM and the experiments lasted for 20 or 26 d. Significant genetic differences in growth and nitrate uptake were identified. The cultivars ʹSkiffʹ and ʹFranklinʹ consistently produced large seedlings which took up large quantities of nitrate from solution whereas ʹStirlingʹ, ʹSchoonerʹ and ʹTriumphʹ produced small seedling and took up small amounts of nitrate. However, apart from differences based on seedling vigor, there was evidence that a group of cultivars which had the Victorian cultivar Research as a common parent was more efficient physiologically in assimilating nitrate. For comparable amounts of nitrate taken up from solution, total dry matter production in this group of cultivars was consistently greater than the other cultivars examined. Results from this work established that genetic differences in nitrate uptake exist between cultivars which in most cases were related to the size of the plant, especially the root system. However, the importance of greater nitrate uptake by the seedling and consequently of early growth, to grain yield was not clearly established because early vigor was not always early beneficial to yield.