The target body condition score (BCS) at calving is 3.25 for dairy cows, with an acceptable range of 0.25 above or below this point.
Figure 1, right, shows the effects of under-conditioning, including low milk yield and anoestrus, while over-conditioning will cause milk fever and ketosis.
The rule of thumb is that every half a condition score (0.5 BCS), equating to approximately 25kg in bodyweight, that a cow is below target at calving results in a 225-litre drop in milk production in the following lactation and reduced fertility.
Take stock of your herd early to make changes in time.
The following points will help you decide how and when to act:
* Herd average BCS is not particularly useful for herd management. Focus instead on using BCS of individual animals and make decisions on a cow-by-cow basis.
* Check the body condition score of the herd at least 14 weeks before the beginning of the calving season.
* Write down expected calving date for each cow.
* Assign each cow to a management plan to meet target BCS using one or more of the tools available. Batch cows according to cow condition.
* Internal parasites and lameness have a negative impact on the cow's ability to achieve target BCS.
Implement a parasite control programme and treat any lame cows in the herd.
Managing cow condition
The main tools for BCS management during the dry period are:
1.Feed intake and quality
Feed energy (UFL) intake drives BCS gain in the dry period. In the dry period, poor quality silage has a double effect of poor dry matter intakes and low energy content.
The aim should be to maximise energy intake from silage. Check the quality of your forage and aim to feed grass silage of 68pc dry matter digestibility (DMD) to the dry cow.
Supplementation of the dry cow will be driven by BCS, length of the dry period and forage quality. Guidelines on supplementation rates during the dry period based on forage quality and BCS are outlined in Table 1, left.
As a guide, cows at condition score 2.5 need 12 weeks dry and, if being fed 68DMD silage, need 1kg of supplementary meal.
2.Dry period length and days in milk
At the standard 60-75 days dry, cows at BCS 2.75 drying off and eating reasonable quality (68-70 DMD) silage will be at target BCS calving down. Allow at least 30 extra days dry where BCS and/or silage quality are below target.
This would mean drying off in late October for early February calving, mid-late November for March calving and mid-December for April calving.
Table 2, below, outlines when cows need to be dried off, depending on the required length of the dry period.
For example, if expected calving date is February 1, thin cows that need 12 weeks dry, should be dried off by November 2.
Siobhan Kavanagh is an animal nutrition specialist with Teagasc.