Effect of Stage of Maturity at Harvest on Nutritive Value of Combine-Type Grain Sorghum Silage

The relative feeding value of RS610 combine-type grain sorghum cut at three stages of maturity was determined. Average silage dry matter percentages were milk to dough stage, 25.3; dough, 27.4; and hard seed, 34.6. There was a decrease in crude fiber and an increase in NFE with each more advanced stage of maturity. The per cent of dry matter represented by seed doubled between the first and third silage stages. A switchback milk production study with 18 cows was conducted in 1964 and repeated in 1965. A Latin-square digestion trial with six bred heifers was conducted each year. Daily silage dry matter intake by the lactating cows increased with each more advanced stage of maturity. The 2-yr average was 1.64, 1.80, and 1.96kg per 100kg body weight daily. However, there was no significant difference in average daily FCM production or milk fat test either year. The digestion coefficients for crude protein decreased significantly with advancing maturity in both studies. In the 1965 trial there was a significant reduction in digestibility of crude fiber with increased maturity and a nonsignificant trend toward lower digestibility of dry matter, crude fat, and gross energy. Nitrogen-free extract digestibility appeared to increase slightly with increased maturity of the silage crop.