Monitoring Energy Status Can Boost Margins

NWF Technical Manager Tom Hough explains why regularly measuring and recording body condition score (BCS) should be an essential management technique this winter.

With most cows now housed on full winter diets, dairy farmers are beginning to see the consequences of the last forage season. Grass silages are generally poorer feed value than those made in 2006 while maize crops are generally disappointing. Yet with better milk prices, dairy farmers will be keen to push for higher outputs.

The challenge is getting the most from high yielding cows and it is going to be essential to ensure they spend as little time in negative energy balance as possible. For this reason dairy farmers would be wise to invest a little time every month condition scoring cows and reacting to what they find out.

Negative energy balance can manifest itself in a number of ways but is typically summed up as cows just aren’t performing. Energy balance is simply the difference between the energy the cow consumes from the diet and the energy she needs for maintenance, milk production, pregnancy and growth. Negative energy balance is where the demands of the cow outstrip the energy she can consume and the physiological response is to mobilise body tissues and to lose weight There are limits to how much condition a cow can, or should lose and excess loss can have significant consequences.

It is inevitable that modern Holsteins will be unable to consume enough energy to meet the demands of early lactation and so fall into negative energy balance. This typically lasts for the first eight weeks of lactation but can extend to as far as week 20. Consequences of negative energy balance can include:

• educed levels of fertility
• Low peak yields and poor lactation persistency
• Disappointing milk proteins
• An increased number of problems around calving

Managing energy balance and body condition is a year round task and requires regular body condition scoring and adjustment to the diet as required. The aim is to manage cows so that they don’t lose too much condition in early lactation, but also don’t gain too much from mid lactation to calving, while ensuring all changes are gentle. The rate of change in body condition can be just as important as the actual body condition scores. For example, cows should not be expected to gain condition during the dry period.

When you condition score a cow you are assessing the amount of subcutaneous fat on the cow, allocating cows to one of five scores (see table) and most importantly, you are gauging how much it is changing through lactation. As such, cow groups should be condition scored monthly to expose any BCS faults within your herd.

To condition score a cow, stand directly behind her to score both the tailhead and loin areas. Score the tailhead by feeling the amount of fatness. This gives a better estimate than visual inspection alone because the set of the tailhead and thickness of coat can be deceptive. Score the loin in a similar way using the same hand when the cow is relaxed. Score the cows from 1 (thin) to 5 (grossly fat), assessing the scores to the nearest half point. Most cows will be between scores 2.0 and 3.5.

It is important to be consistent about how and when you condition score cows. It should be done each month by the same person using the same hand and cows should be scored at five set times: mid to late lactation, drying off, at calving, 4 weeks post calved and at peak lactation – 90 days post calved.

Now I know plenty of farmers who say they condition score cows regularly, but I know very few who do it consistently and record the results to understand the trends within their herds. And it is this that is important.

The target is to keep cows within a set of guidelines based on stage of lactation so that they don’t get too thin but also aren’t allowed to get too fat. While thin cows suffer from low milk proteins, poor fertility and less persistent lactations, overly fat cows also have fertility problems, are more prone to calving difficulties, have poor appetite in early lactation and suffer excessive condition loss post calving.

Working with vet Bill May of Lambert, Leonard and May and Dr John Allen of Frank Wright Ltd, we have developed a simple system, the NWF BCS monitor, to help farmers assess and interpret the condition of their cows. By condition scoring cows at the correct times and recording the results it gives a meaningful picture of what is happening in your herd.

The system simply requires five groups of cows to be scored each month with the results entered onto a spreadsheet. When entered, averages are automatically calculated and plotted onto a graph giving target scores by stage of lactation. If cows fall outside this range then management action can be taken to correct the position, remembering to do this gradually over time, avoiding sudden changes which themselves can affect performance.

The graph shows a typical problem in a high yielding herd. The cows are a little thin at drying off, and as cows should not be expected to gain condition in the dry period, they calve down again at below the target BCS. During lactation, the cows lose condition a bit too quickly and so remain below target for the whole lactation and are still below target when they dry off again. As the cows can not draw on significant body reserves as they are in below target condition, they will fail to peak as expected and lactation persistency will be poor. Fertility will also suffer due to poor BCS.

Armed with this information it is possible to develop a management plan to address the problems. Overall the aim should be to increase energy intakes to offset the low condition. Feeding should be increased in early lactation to reduce BCS loss at this time. Mid and late lactation diets should be reviewed to encourage an increase in condition so cows dry off at the target score. Dry cow feeding appears OK but should be monitored to ensure cows calve down at the target score.

The time to start condition scoring cows is now. Don’t wait until you think you have a problem. It is always cheaper and more effective to prevent problems occurring than to correct them once they exist while improvements in yield this winter will give margins a timely boost.