Interaction Between Variety And Maturity Stage Of Kernels To Affect Silage Fermentation Characteristics Of High Oil Corn Stalks And Their Feeding Value To Growing Cattle

Three experiments were conducted to determine the effect of interaction between variety and maturity stage of kernels on silage fermentation characteristics of high oil com (HOC) stalks and on their feeding values to growing cattle. The treatments included corn variety (HOC115, HOC601, HOC647, normal 3138 or specific silage corn variety) and maturity stage of kernels (2/4,3/4 and 4/4 milk line; ML).In Experiments 1, microorganism counts in pre- and post-ensiling corn stalks of 4/4 ML maturity stage, stalk silage fermentation characteristics, chemical composition and in vitro digestibility of four high oil com varieties (HOC 115, HOC298, HOC601 and HOC647) were determined. Significant difference in the number of Lactobacillus and yeasts of pre- and post-ensiling stalks was found among the four varieties. With the latest maturity stage, there was a higher pH value and lower lactic acid concentration for HOC115 and HOC601. In contrast, increasing maturity stage of kernels of HOC 298 and HOC 647 resulted in a declined pH values and an increased lactic acid concentration. With advancing maturities, there were a tendency in an increased content of WSC (P<0.01), decreased contents of CP and ether extract (P<0.01), with exception of CP of 298 (PXX05), which had no significant change (P>0.05) with maturity stage. Advancing maturity stage of kernels significantly increased starch content (P<0.05) of stalk silage of HOC115, HOC 298 and HOC 647. As progressive maturity of kernels, the content of fiber fraction (NDF, ADF and lignin) of stalk silage was increased (P<0.01) for HOC115 and HOC601, but not for HOC298 and HOC647. The content of calcium of stalk silage had a decreased tendency with advancing maturity stage of com kernels, but the content of phosphate was less affected by the maturity stage. With progressive maturity of stalk silage, the DM and NDF digestibility, 48 h gas production and gas production rate (P<0.01) were decreased for HOC115 and HOC601, but increased (P<0.01) for HOC298 and HOC647.The purpose of Experiment 2 was to compare the nutritional value of stalk silage of HOC 115, normal corn variety 3138 and a specific silage corn variety. Significant difference was found for the count of Lactobacillus and yeasts (P<0.01) in pre- and post-ensiling stalks among the three varieties. For the variety of 3138, with increasing maturity, there was a declined lactic acid concentration and a increased pH value. Less contents of WSC, ether extract, starch (P<0.01) and crude protein (P<0.05), but higher contents of NDF, ADF and lignin (P<0.01) were also found with progressive maturity stage of com kernels. Advancing the maturity stage of com kernels seemed to decrease (P<0.05) phosphorus content of the stalk silage, but not affect the calcium content (P>0.05). In contrast to 3138, the specific silage com variety showed more contents of WSC and starch (P<0.01), less contents of CP and ether extract (P<0.05) with advanced maturity stage of com kernels. As maturity increased, the digestibility of DM and NDF, 48 h gas production and gas produced rate (P<0.01) decreased gradually for 3138, but quadraticly increased for the specific silage corn variety.In Experiment 3, a growing trial using 60 Jinnan yellow steers and an in situ study were conducted to investigate the effect of whole-plant silage of HOC115 and Tangkang No.2 (another normal corn variety) on growing performance and their dry matter and fiber digestibility. The result was that the digestibility of DM, NDF and ADF of HOC115 was much lower (P<0.05) than Tangkang No.2, whereas DM intake of the silage of HOC115 was much higher (P<0.01) than Tangkang No.2. However, there was no significant difference (P>0.05) in daily gain rate and feed conversion between the two silage diets.