Editor’s note: This article is a continuation of the information presented in the last issue titled “Cow comfort: Body condition score (BCS).”

Recommendations for BCS management
It is recommended that cows be scored at calving, during their first postpartum exam, when bred, when checked for pregnancy, some time during late lactation and at dry-off. Nutritionists feeding groups of cows should determine the average BCS of each feeding group. Body condition should be the final word on the energy content of the diet, rather than the computer-predicted energy value of the ration. If the cows are too thin during early lactation, adjust the energy content of the diet upward and focus on ways to increase dry matter intake.

Determine if metabolic problems are extreme and may be causing the weight loss. Late-lactation cows use energy for body reserves more efficiently than dry cows (75 percent vs. 60 percent efficiency). So it is recommended that cows be put on condition during mid to late lactation (after 75 to 100 days in milk) and achieve the desired calving BCS of 3.5 at that time, rather than during the dry period. If cows are too heavy in late lactation, reduce the energy content of the diet immediately rather than putting them on a diet during the dry period.

When feeding cows as a group, it is important that the group have a fairly uniform BCS. If they do not, there is most likely a problem. Perhaps some cows are experiencing severe metabolic problems which reduce dry matter intake early in their lactation. Perhaps cows are not being fed a true total mixed ration (TMR). For example, cows may be sorted or they are being offered hay separately. Perhaps there are hoof and leg problems that limit some cows from getting to the feed bunk. There may be severe reproductive problems causing some cows to stay in a particular group longer than they should – they will be getting fat while others in the group are milking well and getting the nutrients that they need.

If the group is not uniform, it is difficult to design the ration to feed all cows properly. Most likely, the compromise will have to be that some cows do not receive a ration with adequate nutrient density while others get too much. The cows receiving too much will get fat and waste consumed nutrients.

Early lactation
We know that a significant amount of the energy a high-producing cow uses to make milk in early lactation comes from her body fat reserves. Weight losses of one to one-and-a-half kilograms per day, are not uncommon during the first 100 days in milk. Forty-five grams of mobilized fat can support about three kilograms of milk. Many herds will average 0.5 body condition loss by 30 days in milk. A good goal is not to exceed 0.5 body condition loss during that time.

It is critical that cows do not exceed one point of body condition loss by 30 days in milk. Cows with excessive body condition losses will have irregular heats, longer time to first ovulation and may fail to conceive. These cows will also be less persistent in milk production.

Cows with a BCS over 3.75 at two weeks prior to calving are more prone to having depressed intakes, weight loss, fatty liver, ketosis, high non-esterified fatty acid (NEFA) levels, calving and reproductive problems. When a cow loses body fat reserves, especially two weeks before and after calving, the liver takes up fat and processes it. Fatty liver and ketosis can then develop.

In a Michigan study, eight percent of dry cows with a BCS of less than 4.0 had health problems while 17 percent of cows with a BCS of more than 4.0 had health problems. In another study, cows that had a BCS of 4.0 or greater at dry-off were 2.5 times more likely to have reproductive problems.

Even if one could avoid the health and reproductive problems associated with fat cows, it is inefficient to put excessive weight on (>3.75 BCS) during late lactation and the dry period, then have to take it off after calving. It takes energy for the cow to process body fat and then to mobilize it for later use.

Dry period
It is not recommended to put over-conditioned cows on a diet at dry-off due to the risk of fatty liver. It is inefficient but acceptable to put body condition on during the dry period if it is needed to achieve a BCS of 3.5 at calving. Total body weight should increase during the dry period.  EL