To vets of a certain age the term mangelwurzel will stir memories of outrageous accents, country yokels and combine harvesters. But the mangelwurzel has a much longer history than a niche 1970s pop group. The mangelwurzel is a cultivar of Beta vulgaris, the common beet. The history of the crop goes back to the mid-18th century when special yellow-fleshed varieties which kept well were separated out for the first time as fodder beet. Further development led to larger root size and increased productivity. However despite it being perfectly edible, fodder beet never became a popular food for humans but remained principally a winter feed for livestock.
Although it was commonly grown as a food crop the use of fodder beet was limited by toxicity concerns, especially in relation to oxalate toxicity – with over 3 kgDM/day being considered a ‘killing’ dose. However, in recent years the use of fodder beet has increased exponentially especially in systems where grazed grass forms a major part of the diet.
This change started when Dutch dairy farmers introduced fodder beet to New Zealand as an alternative to brassicas for feeding to dry dairy cows in winter. Yields were high which meant that fodder beet could be strip grazed resulting in intake levels above the so-called killing dose. Stock losses were high – which seemed to support the suggestion that oxalate toxicity meant that fodder beet intakes need to be limited. However, farmers who persisted with fodder beet found that only a percentage of animals fed high levels of fodder beet died and that the cattle that survived did extremely well.
Research by Lincoln University showed that the losses were not due to oxalate toxicity but due to rumen acidosis. This recognition lead to the development of protocols for transitioning cows on to fodder beet which meant that cows could safely graze very high intakes of fodder beet. Within 10 years the amount of fodder beet on dairy farms and related properties grew from <50 to over 60 000 hectares. In New Zealand, fodder beet is being increasingly used in lactating dairy cows in autumn, on beef farms, and, when collected and chopped, on sheep farms.
The rapid rise of fodder beet as a food for livestock, even though beets and their roots have been fed to livestock for over 1500 years, has a lot of interesting lessons for the veterinarian. These include:
- Just because something is old doesn't prevent it becoming popular, especially if new ways can be found to use it. A similar example would the use of disinfectants to treat mastitis — disinfectants were our primary treatment for mastitis prior to antibiotics and increased scrutiny of antibiotic use has meant that disinfectants are once again of interest.
- Strip grazing of fodder beet would never have been suggested by ‘experts’. The use of fodder beet was driven by farmers trying to find an alternative to crops they were not happy with. They then stuck with the crop when problems occurred because it was their choice to feed it in the first place. This probably wouldn't have happened if it was an expert-driven trial.
- Just because something is popular doesn't mean it's simple. Lots of cows in New Zealand get acidosis on fodder beet every year, despite protocols for preventing acidosis being widely available. This is down to insufficient care and attention.
- Acidosis is much more common on New Zealand dairy farms than before the fodder beet revolution. This has highlighted the lack of an evidence-based approach to acidosis by many veterinarians with many sick cattle being treated with sodium bicarbonate and magnesium products which do not alter pH, but do exacerbate osmolarity problems. This reminds us that as a profession we do need to critically assess our approaches and to not just do ‘what we have always done’.
So like succulents in the garden centre, mangelwurzels have made a comeback. Unlike succulents which probably will be back to their normal long-term level of popularity in 5–10 years, it is likely that mangelwurzels are here to stay as a key part of the rotation of cattle farms. It's ironic that their return is coincident with that of a talking scarecrow to prime-time television. Hopefully, we won't also see the return of smocks, pitchforks, and Mummerset accents.