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Maize silage is probably the most popular and most used roughage source for dairy cows in South Africa. This is because of yield per hectare, energy as it contains maize, being a fodder bank, ease of use and palatability. However, quality is crucial which is determined by factors such as compaction, aerobic stability and organic matter losses. The question is, do farmers make good quality maize silage for their cows? The authors of the study cited below decided to do a survey to establish the status on South African farms.
They collected maize silage samples randomly from 45 silage bunkers in different parts of the country. At each bunker, three core samples were taken with a 110 mm silage corer in the middle of the bunker, spaced 1 m apart. Each core sample was taken at three depths: 0‐10 cm, 10‐20 cm and 20‐40 cm (Three core samples at 3 depths, meaning 9 samples in total). Compaction of the different layers was determined using the weight and volume of each core sample. The three core samples were then pooled for each depth, a representative sample taken, which was sealed in a plastic bag, kept cool and later frozen pending analysis. At analysis, the dry matter (DM), pH and ash content were determined. Also, a representative sample of 300 g from the 20‐40 cm pooled sample was loosely placed in a 2 litre plastic container with several holes on its sides to determine aerobic stability. This silage sample was exposed to air for 5 days and then frozen. Thereafter the DM, pH and ash content was determined to estimate organic matter (OM) losses. The DM, pH, ash, total digestible nutrients (TDN), crude protein (CP), starch, neutral detergent fibre (NDF), lactic acid, acetic acid, propionic acid and butyric acid of each pooled silage sample taken at 20‐40 cm in the bunker were then determined. Furthermore, the chop length of the silage was recorded. This was done by measuring the particle length of 10 chopped maize stems using a ruler.
The composition mean (the deviation from the mean is given as a percentage) of 45 maize silages were: DM 32.2% (14.9%), pH 3.9 (5.4%), TDN 69.3% (8.8%), CP 9.3% (17.3%), starch 24.1% (31.8%), NDF 44.0% (12.5%), lactic acid 4.9% (34.3%), acetic acid 3.9% (46.2%), propionic acid 0.27% (63%) and butyric acid 0.02% (error too large to give). The average compaction of the 20‐40 cm layer was 726 kg silage/m3 (8.3%) with a minimum of 409 kg/m3 and maximum of 934 kg/m3. The compaction in the top 10 cm of bunkers was 433 kg/m3 (27.9%), but the worst compaction was only 238 kg/m3 compared to the best compaction in the top layer of 703 kg/m3. The average OM loss in the top 10 cm layer was 14.5% (148%); the highest OM loss was 90.4% and the best maize silage bunker had no OM losses. The average OM loss in silages exposed to air for five days was 12.6% (90.5%). The most stable maize silage had no organic matter losses after 5 days of aerobic exposure, whereas 58.3% of OM was lost in the least stable silage. The average pH of silage increased from 3.85 before aerobic exposure to 5.58 after 5 days of exposure. The pH of the most stable silage did not increase whereas the pH of the least stable silage increased to 8.48. The average chop length was 9.7 mm (23.5%), the shortest chop length being 5.3 mm and the longest 15.0 mm. The DM content of a large portion of the maize silages was below 30%, indicating too early ensiling resulting in maize silage with a lower starch and energy content.
Conclusions: It is clear that there is much scope for improvement. Maize silage should be ensiled at 35% DM and much more emphasis should be put on compaction of the top layer to improve aerobic stability.
Reference:
R. Meeske & R. Venter, 2016. Composition, compaction, aerobic stability and organic matter loss of maize silage on South African farms. In: Proc. of the 49th SASAS Congress, Abstract 16.