6 Tips for Feeding High Corn Silage Rations
Dairy operations can feed cows economically with high-forage diets using corn silage as the sole source of forage. However, producers should consider several management factors when feeding high rates of corn silage.
1. Evaluate silage kernel processing. The starch in corn silage is a valuable commodity, but the kernels must be damaged sufficiently to allow complete starch digestion. Analyzing processed kernel samples can help a nutritionist estimate starch digestion in the rumen and small intestines. Analyzing fecal starch levels can determine whether poor processing is allowing starch to escape into the manure. Fecal starch levels exceeding 5% likely signal the need for an adjustment.
2. Don't overdo the starch. Starch is often considered the "villain" when cows fed high levels of corn silage don't respond as expected, experience low butterfat tests or display inconsistent manure scores. Laboratory starch analyses help nutritionists factor the effects of time in fermented storage on ruminal starch availability. From ensilage until 6 months later, starch digestibility in corn silage can increase as much as 20%. Diets formulated with 26% to 28% starch in fall may need to be closer to 23% to 25% to account for increased starch availability. High moisture corn or snaplage also will develop elevated ruminal digestion rates as storage time increases. Dry corn may be a better source in very high level corn silage diets.
3. Watch effective fiber. If the chop length is short, producers may need to find an effective fiber source, such as poor-quality hay or straw. This helps create a rumen mat matrix that stimulates cud-chewing and saliva production to buffer rumen acid production. Evaluate freshly delivered total mixed ration (TMR) and refusals after 3-4 hours in the feedbunk with a Penn State Particle Separator to determine whether adequate effective fiber (top screen) is present and whether any sorting has occurred.
4. Keep supplemental fat within reason. A review of tallow supplementation (2% of the ration) in high corn silage rations showed a tendency to reduce intake and lower fat test outcomes (cause and effect are not fully understood). We can avoid fat test problems with an understanding of the trans fatty acid theory of butterfat depression along with the ability of newer ration software to track estimates of unsaturated (especially linoleic acid) intakes.
5. Rumen bacteria provide protein. High-energy corn silage grows lots of ruminal bacteria, which the cow digests as a high-quality protein source. Producers have had success with rations containing up to 25 lbs. of dry matter (DM) from high-starch corn silage by targeting 16% to 17.5% crude protein (CP) levels and conservative levels (8% to 8.5% DM) of ruminally degraded protein to fuel bacterial needs and by paying attention to lysine and methionine levels.
6. Avoid feeding high corn silage rations to dry cows and heifers. Exclusive corn silage rations are not suitable for dry cows and heifers. Doing so often results in overweight heifers and problems for dry cows.