THE EFFECT OF TEMPERATURE ON QUALITY CHARACTERISTICS IN TIMOTHY (PHLEUM-PRATENSE L) GENOTYPES

Improving the nutritive value of timothy (Phleum pratense L.) through breeding is dependent on selecting for genetic traits which directly c ontribute to ruminant digestibility. The identification of these trait s is the goal of many forage researchers. The objectives of this resea rch were to evaluate the leaf and stem digestibility of six timothy ge notypes under different temperature conditions using two methods of es timating digestibility. Correlations between leaf and stem digestibili ty were not significant, suggesting that separation of these component s is nessessary to clearly evaluate genotypic differences. Temperature had an important effect on digestibility, particularly for the stem f raction. Isolating leaf from stem and evaluating genotypes individuall y across temperatures may permit the identification of more simple gen etic factors which control digestibility in timothy. Genotypic differe nces were observed at all temperatures. The rumen fluid digestion resu lted in a much greater range within and among genotypes for both stem and leaf fractions. Genotypes tended to follow the same trends with re spect to temperature using both techniques suggesting that only a port ion of the dry matter digested by rumen fluid is available to the cell ulases used in these experiments. Lignin content was measured for two of the most variable genotypes and the results showed that while level s increased with higher growth temperature, differences between genoty pes are more pronounced at 10-degrees-C for both leaf and stem.