Calculate body condition based on time of calving
Tuesday December 15 2009
Guidelines for feeding suckler cows are based on a fairly simple principle -- feed to body condition score in relation to the stage of the production cycle.
There are ideal body condition scores to aim for during the various stages throughout the year, depending on whether the cows are spring-calving or autumn-calving. Body condition scoring involves regular assessment of the body condition of individual cows and calculation of the herd average. The appropriate body condition score varies with the stage of the production cycle. The table (right) gives a guide to recommended condition scores for autumn and spring-calving cows.
The figures in the table refer to herd averages, and indicate that the herd body condition scores for both autumn and spring calvers should move in the range of 2.0-3.0 or slightly higher. Obviously, individual cows will be 0.5-1.0 scores outside this range. Having cows much above condition score 3.0 is wasteful and increases calving difficulty if they are over-fat. However, the bigger loss occurs with cows that are under 2.0 at calving or mating.
Research by Prof Michael Diskin shows that cows that are under 2.0 at calving will be up to three weeks slower going back in-calf, and where there are a significant number of cows in a herd under 2.0 at calving, the calving interval (period between calvings) will not be maintained at close to the 365-day target. There are always the one or two exceptional cows in a herd that are at, or close to, condition score 2.0 around calving and still maintain high reproductive performance.
Ideally, the autumn calvers should be at, or somewhat above, condition score 3.0 at calving and should not lose more than 0.5 of a condition score up to mating. Once the cow is settled in-calf, a further 0.5 condition score can be lost with no adverse effect on production or fertility. The feed requirement of autumn calvers depends on condition score at calving and the level of milk production. If the cow is at condition score 2.5 at calving, she cannot afford to lose any condition up to mating.
In energy terms, a 600kg cow requires 5.5 UFL (units of energy) for maintenance (equivalent to 5.5kg of standard barley or 36kg silage at 20pc DM and 68pc DMD). Each litre (1kg) of milk requires about 0.45 UFL. The feed requirement of a suckler cow giving five litres of milk is about 45kg of silage at 68pc DMD plus 1.0kg of concentrates a day. A cow giving 10 litres of milk a day would need 3kg meal with the 45kg of silage to stay at the same body condition. The milk yield of beef cows is usually five to eight litres a day in the first three months of lactation. First-cross Friesian suckler cows are likely to give 8-10 litres of milk a day and will lose more condition in early lactation than their more beef-type comrades if fed the same diets.
In practical terms, relatively good silage -- ad-lib -- and 1-2kg of meal a day up to mating should keep adequate condition on autumn calvers. Cows that calve at condition score 3.0 or better can lose 0.5 of a score up to mating, which is equivalent to saving about 1kg of meal a day. Therefore, if your cows are at condition score 3.0 at caving rather than 2.5, you will save 1kg of meal a day. High-quality silage is much more important for autumn calvers than spring calvers -- eg silage of 75pc DMD, fed ad lib to lactating suckler cows, is capable of providing maintenance (no condition loss or gain) plus eight litres of milk a day.
Once the cow is settled in-calf, further loss -- back to condition score 2.0 -- is acceptable, which could represent a reduction in the meal allowance of 1kg/day in the 8-10-week period before turnout. It is more efficient to divert meal feeding towards the calves while indoors than feeding the cow.
High-quality silage has adequate protein for a suckler cow giving 6-8 litres of milk. As digestibility falls, both energy and protein intake also fall. On lower-quality silage, feed a 16pc crude protein ration. Each five-unit drop in DMD from 70pc requires an increase in the meal input of about 1kg/day. A post-calving mineral of about 100g/cow/day should be fed on the silage, or as part of the concentration ration.
- Liam Fitzgerald
Irish Independent
