While some farms have been able to capture a decent wedge at the end of the autumn, many have eaten pasture as fast as it has grown. It is not uncommon to find spring calving herds heading into the dry period with low pasture covers, cows 0.2BCS behind last season and needing to winter on the milking platform.
First, get a feed budget done quickly and determine where you sit. The small silver lining is that many farms have better supplement reserves this winter. We are looking at a cold and hopefully, drier winter ahead, which will reduce growth rates but also reduce wastage rates of pasture and supplements fed. Use conservative growth rates for your area and apply wastage rates of 15% for pasture, hay and bailage fed and of 30% or more for maize silage fed out in the paddock.
A 500kglwt cow of BCS 4.3 at dry-off with 9 weeks until PSC will require 120MJME per day to gain BCS at 0.5/month and grow her calf. This equates to allocations of 12kgDM at 11MJME with 10-15% wastage. The same cow with only 4 weeks until PSC will only put on 0.1 to 0.2BCS per month if fed to the same level.
The energy content of pastures we have sampled in Kaiaua, Waerenga, Rangiriri, and Mangatawhiri over the late autumn are consistently returning MJME/kgDM values beginning with a 10, not an 11. This will increase the allocations required to gain BCS.
If you have a feed pad, use it, and reduce your supplement wastage. Limit daily pasture allocations and hold the round out to meet pasture cover targets at PSC without damaging paddocks through on-off grazing.
For farms without a feed pad and unable to get cows away, be prepared for a tricky period ahead. At a typical stocking rate of 2.5c/ha, with average pasture covers of 1800kgDM/ha, pre-grazing mass of 2200kgDM/ha, and residuals of 1400, a grazing interval of 65days will see pasture allocations of 5kgDM/c/d. At average winter growth rates of 18kgDM/ha/d a surplus of 5.5kgDM/ha exists.
Average pasture cover should lift over the next 65 days to 2150kgDM/ha. Supplementation rates will need to be 8kgDM/c/d (520kgDM/c before calving) at an average wastage figure of 20% to make cow targets.
A round of 45 days will provide another 2kgDM/c/d of pasture and save 130kgDM in supplement per cow, but pasture covers will remain below 1900 by PSC. A round of 85 days will drop pasture allocations by 0.5kgDM/c/d and allow covers to reach 2250kgDM by PSC. However, another 45kgDM of supplement will be required for cows to make BCS targets or cows will calve 0.25 of a BCS lighter. The increased grazing intensity may also damage paddocks compromising the coming season.
BCS and pasture cover targets exist for the good reason that they have been shown to optimize health and production in the early part of next season. It is worth trying to meet them. However, if the winter is looking tight, start on a 65-day rotation with supplementation allocations of >6kgDM/c/d. Feed out supplements when and where wastage will be limited to get the biggest bang for your buck.
And, if you just need to throw some ideas around with one of our team, do it early.
Dr David Hawkins, Farm Vet in the South of our practice