Outdated sub-clover cultivars can be very problematic. They can cost autumn and winter pasture production due to growth habit, soil-borne diseases, insect attack or the fact they are oestrogenic, which affects livestock fertility.
Reduced winter feed production of up to 30% and, if oestrogenic clovers are present, long and short-term infertility lowering lambing percentages to 25–70%.
More recently bred cultivars offer better disease and insect resistance and low oestrogen content. This means improved long-term winter pasture production and animal performance.
Outdated sub-clover cultivars can result in significant pasture and/or animal underperformance. The most common losses occur because the sub-clover contains oestrogen, resulting in ewe fertility issues* and/or are susceptible to plant diseases, resulting in lower annual production.
Improvements in growth characteristics, pest and disease resistance also contribute to the widening gap between older and newer cultivars.
* Cattle are less likely to be affected, although international studies report cows fed hay containing oestrogenic clovers suffered from short-term infertility.