The body condition of cows after calving can sometimes be surprising. The 150 pounds or so of calf and fluids are gone and it becomes much easier to see the amount of condition, or lack there of, along the back of the cow and over the hooks. Long winter hair coats can also compound the problem of accurate body condition evaluation. What are the options when body condition at calving is below target?
If these cows go to grass and there is a sufficient quantity of forage available, they may gain over a pound a day depending on milk production potential. Under conditions of slow forage growth and/or high forage moisture content, energy intake will be much lower. Using the BRANDS ration formulation program with cool season pasture as the forage, cow weight gain approaches zero when forage intake is 80% of predicted. So very early in the season cows may be just maintaining weight rather than gaining. Continuing to provide hay early in the grazing season can help, although palatability differences between the hay and new grass often makes the effort seem wasted.
Cows must be in a positive energy balance or gaining some weight before they will begin cycling again after calving. If winter feed quality has not produced the desired body condition in cows then an additional week to ten days on grass before bulls are turned out may provide a big benefit to cow reproduction. More cows will begin cycling in that time period and stand a better chance of conceiving the first 21 days of the breeding season. While calving will start a few days later the following year, normal variation in actual gestation length will lessen the effect. In addition, if bulls have been selected for low birth weight, gestation length tends to be shorter as well.
Many systems for synchronization of estrus incorporate some type of progesterone (CIDR, MGA) exposure to induce females that are not yet cycling to cycle. While this type of treatment will not work on cows that are still too deep in anestrous, i.e. too thin or too close to calving, it will induce those that are close to resumption of normal cycles. Bull exposure and 48 hour calf removal are other management options that will induce non-cycling cows to cycle. Natural service sires at normal cow to bull ratios should have no trouble covering cows with these types of induction treatments alone.
Don’t forget the importance of having bulls in good body condition before the start of the breeding season as well. They will expend a lot of energy as soon as the breeding season starts and need the condition to do so. Good risk management for bulls includes a breeding soundness exam before turnout.
When over half of the herd has a body condition score less than 5, delaying the start of the next breeding season has the potential to keep the herd calving in a tighter group. Leaving bulls out longer may result in the same number becoming pregnant but calving will last much longer. Have you ever heard anyone say the calving season was over too soon?
Effect of low body condition at AI on pregnancy rate to AI in KSU herds
Three university herds were used in a synchronization trial in 2002 and the herds varied in body condition at the start of the synchronization protocol. The table below shows the CCU herd with an average body condition score of 4.8 at breeding and only 45% were considered to be cycling at the start of treatments. The other two herds had body condition scores just over 5 and close to 80% cycling. The AI pregnancy rates directly reflected the cow body condition score and was lowest for the CCU herd.
Source: Sandy Johnson, livestock specialist, Kansas State University Extension