Dr. Maurice Eastridge, Professor and Extension Dairy Specialist, Department of Animal Sciences, The Ohio State University
Change is ever present, including in forage harvesting conditions. Even without listening to the weather report, we know by the challenges in harvesting forages this fall, the limited days to apply manure, and the constant muddy conditions in animal lots that the amount of precipitation in the Midwest is above average. We may have already forgot how wet it was in July 2017 (Figure 1) which created difficulty in harvesting legumes and grasses, but our focus at the moment is on the challenges of the current wet conditions and its consequences. Actually for the Columbus area (data used for Table 1), the precipitation to date since April 1 is only about one inch greater than the same time period in 2017. However, since August 2018, we have experienced about 2.3 inches additional rainfall compared to 2017. Especially notable in this time period is the 5.4 inches of rain in August when corn silage harvest began in several areas.
Based on the 2018 weather conditions since August, it appears that in general the corn silage yields have been rather good (not in every situation by no means), but general comments from the field have implied some quality concerns. Some have expressed that the wet conditions delayed harvest and the plant exceeded optimal maturity. In these situations, advanced kernel maturity may result in lower starch digestibility, especially if a plant processor was not used or if proper settings were not used. Data from Cumberland Valley Analytical Services (Waynesboro, PA; https://www.foragelab.com) for corn silage were summarized over two time periods, January 2016 through July 2018 and August 2018 through November 2018 (Table 1) to look for potential changes in composition. The concentrations of DM, CP, ADF, and NDF were similar among the two populations; however, the starch digestibility was lower in fall 2018 by 5.3 percentage units and NDF digestibility tended to be lower for the same comparison. Of course, these digestibility measures do not reflect the potential magnitude of differences in total tract digestibility of these two major carbohydrate fractions, but they can reflect potential changes in digestibility and thus animal performance.
At this point in the season, the corn silage is in storage and thus if analyses indicate that digestibility may be less than typical, then the following considerations should be made:
- Can the corn silage be left in storage longer before feeding? Longer storage time may increase starch digestibility.Are there economical options for lowering the inclusion level in the diet of the corn silage with lower digestibility?
- If feeding rates are adequate for having two storage units for corn silage open, feed the lower digestibility silage to later lactation cows and growing heifers.
- With the wet field conditions and corn being in the field longer for damage to kernels, be watchful for signs of molds that produce mycotoxins.
Table 1. Analytical values for corn silage samples from the Mid-Atlantic region of the US (data from Cumberland Valley Analytical).
||August 2018 through
|NDF 30 h digestibility,%||56.2||55.4|
|Starch 7 h digestibility, %||72.7||67.4|
Figure 1. Precipitation in Columbus, OH for April through November during 2017 and 2018.