Abstract:

The aim of this experiment was to study the effects of stubble height and harvest time on the nutritional components and mycotoxin content of silage made from maize （Zea mays ‘Yu Qingyu No. 3’） as well as in vitro rumen fermentation parameters for beef cattle. The overall aim of this research is to provide a theoretical support for improving the feed value of silage maize. The silage maize cultivar ‘Yu Qingyu No. 3’ was cut to five different stubble heights （20， 30， 40， 50， and 60 cm） and harvested at four different stages （1/4， 1/2 and 3/4 milk line stage， and dough stage）， a total of 20 treatments were tested， each replicated three times. According to the five-point sampling method， 10 silage maize plants in each stubble height treatment group were harvested at each harvest period. The harvested plants were crushed and then the fibers were cut to about 1 cm in length， and ensiled in a silage tank for 90 days. After ensiling， samples were analyzed for nutritional components， mycotoxin content， and in vitro rumen fermentation parameters for beef cattle. The results showed that： 1） The crude protein （CP）， crude ash （Ash）， acid detergent fiber （ADF）， and neutral detergent fiber （NDF） contents and gross energy （GE） all differed significantly among the stubble height treatments and among the harvest period treatments （P<0.05）. At a stubble height of 40 cm， the gross energy content showed a trend of initial increase and then decrease with the delay of the harvest time， reaching the maximum value at the 3/4 milk line stage. 2） The zearalenone （ZEN） and aflatoxin （AFs） contents in the maize differed significantly among the stubble height and harvest period treatments （P<0.05）. At a stubble height of 50 cm， the zearalenone content showed a trend of initial decrease and then increase with the delay of the harvest date， reaching the minimum value at the 3/4 milk line stage. 3） In the in vitro fermentation analyses， the concentrations of acetic acid， propionic acid， and butyric acid at 24 and 48 hours differed significantly between the stubble height and the harvest time treatments （P<0.05）. At the stubble height of 30 cm and harvest at the 3/4 milk line stage， the concentration of propionic acid reached the maximum value after 48 hours of in vitro fermentation， while the concentration of butyric acid was lowest at 24 hours and showed a pattern of initial decrease followed by an increase with delayed harvest. In summary， to produce high-quality silage， the maize cultivar ‘Yu Qingyu No. 3’ should be cut to a stubble height of 30-50 cm and harvested at the 3/4 milk line stage.

Key words: stubble height, harvest period, beef cattle, nutritional components, mycotoxin, fermentation parameters