Nutrition of Autumn-calving Dry Cows30 September 2014
Advisers at Teagasc offer timely advice for an autumn calving herd, foregrounding body condition score and mineral balance.
Concentrate on these two things and it should be 'relatively straightforward', although it may be useful to follow these pointers.
- Cows should be in BCS 3.0 to 3.25 at calving. This greatly reduces healthproblems around calving (milk fever, ketosis, displaced abomasum), and improves milk yield and fertility. A common mistake is to underestimate BCS so make sure you know the targets and monitor cows regularly.
- For an eight-week dry period, 9-10kg DM of moderate quality grass is adequate in the early dry period. Where cows are at risk of excess BCS gain, allocate grass little-and-often. If grazing behind the milking herd, allowing dry cows back over re-growths increases energy intake so back-fences are important
- Don't worry too much about gut fill until the last two weeks before calving, tight grazing is not a problem before then. Introduce some stemmy silage/haylage as extra forage at that stage.
- Trace minerals (e.g., selenium, iodine) and vitamins are required in tiny quantities and can be supplied either as boluses or dusted minerals. Major minerals (e.g., magnesium (Mg), P) are needed in larger quantities and will need to be supplied daily. Check that all mineral requirements are being covered.
- Magnesium status has a major effect on milk fever. Up to 0.4 per cent Mg in the total diet is recommended for dry cows, which means 15-20g of added magnesium per cow per day. Make sure that your dry cow mineral is supplying this. Sweetened Cal- Mag (around 20g per hd) can be offered in addition to the standard dry cow mineral if necessary.
- High potassium in forage interferes with magnesium uptake which can lead to subclinical milk fever and retained afterbirths. Avoid lush pasture, bales from surplus paddocks, and first cut silage with heavy slurry applications, during late pregnancy.