- Achieving BCS targets at calving is important for future performance.
- Take action mid- to late lactation to help cows hit BCS targets at calving.
- Use all information available to determine suitable dry-off dates for individual cows and view dry-off as a gradual reduction of the milking herd.
There’s a strong link between individual cow body condition score (BCS) and herd reproductive performance. Cows that calve too thin (less than BCS 5.0 for mature cows, and less than 5.5 for first- and second-calvers), generally take longer to start cycling after calving. This can reduce submission rates and conception rates, negatively affecting 6-week in-calf rates and not-in-calf rates.
Hitting BCS targets
Aim to have less than 15 percent of your herd above target, and less than 15 percent below. To meet targets at calving, consider each cow’s BCS and calving date when you’re determining her management through late lactation and dry-off date. Once-a-day (OAD) milking and preferential feeding can help increase BCS gain in late lactation; however, the most effective way to gain BCS is to dry off cows and feed them appropriately.
How to choose dry-off dates
Picking a cow’s dry-off date depends on the amount of BCS she must gain to achieve target at calving; her predicted calving date; the amount and type of feed she’ll be offered during the dry period; and for some cows, her milk volume and quality and her contribution to the bulk tank somatic cell count. Avoid chasing the small volumes being produced late in this lactation at the expense of next lactation’s performance.
Remember to consider what feed is available, including pasture cover and the quantity and quality of crops and supplements.
Also consider the amount and type of feed a dry cow can consume on a daily basis, and the amount of BCS she can gain each month (a sensible amount is usually 0.5 BCS unit/month). Cows often gain no BCS in the first seven to 10 days of the dry period and gain very little in the month prior to calving. That means there are about 30 to 40 days during the dry period where cows gain no BCS.
With early-aged pregnancy testing information, we have an accurate predicted calving date to work backwards from when determining her appropriate dry-off date.
Calculations to determine dry-off dates are provided in the table below or use the DairyNZ dry-off-date calculator (dairynz.co.nz/bcs-strategies). Note: for the mammary gland to ‘reset’ itself, all cows, even if they’re at target BCS, should have a dry period of at least 42 days.
This article was originally published in Inside Dairy February 2020