Carrying capacity in winter
Due to the cold winters, shorter days, and low light intensity in the Southern Cape in winter, the growth rate of ryegrass decreases to 20 to 30kg dry matter (DM) per hectare per day. This is significantly lower than the 60 to 80kg DM per hectare per day produced in spring and summer.
Only two cows per hectare can, therefore, be accommodated in winter. However, the average stocking rate on most farms that cultivate grazing under irrigation, is four to five cows per hectare. For that reason, surplus grazing in spring and summer are ensiled and used during winter to bridge the roughage shortage gap.
Below-average rainfall was recorded for the spring of 2019, which meant that considerably less silage was produced on many farms. Roughage shortages can, therefore, be expected in the winter of 2020.
Lucerne hay and silage
Two strategies are generally used to overcome roughage shortages. One is to buy in roughage such as lucerne hay and the other is to feed some form of silage.
Lucerne is expensive. It usually has to be transported over long distances and transport costs are therefore a contributing factor. In addition, smaller farms do not necessarily have the storage capacity to store bulk quantities of lucerne.
Silage, on the other hand, should preferably be available on the farm and many farmers plant maize to produce silage. However, maize silage yields were also affected by the drought.
If one decides to purchase silage, it is important to determine its moisture content and price per ton DM. As silage is a perishable product, feed-out needs to occur within one to two days once it has been exposed to air. This is why it is neither practical nor cost-effective to transport silage over long distances.
Ring feeders are generally used for both lucerne and silage, with a resulting 10 to 20% that can easily be wasted.
Starch vs high-fiber concentrates
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