Once again the brisk fall air is here, which means most cow/calf producers are busy processing and tending to new weaned calves. While weaning time usually requires all hands on deck, we can also take advantage of this time to manage the cows before they are sent back out to pasture. Practices that can be added to the to-do list this fall while cows are in the corral include pregnancy detection and body condition score.
With evolution of technology, there are now several methods of pregnancy diagnosis available for producers to choose from. Rectal palpation has been utilized for decades, and still remains as a viable way for an experienced person to physically palpate the fetus and determine the gestation length (age) of the fetus. This method is quick, requires no extra equipment and is the least cost option for producers. Another option available is transrectal ultrasonography. With this method an ultrasound machine is connected to a probe that is inserted into the rectum either by hand or using a hands-free probe extender allowing the fetus to be examined visually. Advantages of ultrasound include earlier determination of pregnancy (as early as 28 days), more accurate age determination, sex of the fetus, presence of multiple fetuses, as well as visual inspection of other structures of the reproductive tract. For optimal results, pregnancy detection via ultrasound should take place before the fetus is 4 months along. Transrectal ultrasound requires special equipment which makes it more expensive than rectal palpation; however, the value of the additional information obtained can help make more precise decisions that may be beneficial to the overall performance of the operation. Lastly, blood tests can be utilized to detect pregnancy. Blood tests measure the amount of pregnancy associated glycoproteins (PAGs) being secreted by the placenta, and are secreted from day 28 of gestation until calving. Blood samples are sent to a lab for analysis which can take a few days; therefore, it may not be the best option for a producer who wants to have the task completed in one day. In addition, if a cow was pregnant but lost the pregnancy, PAGs will remain in the blood for an extended period of time (60 days) so false positives are possible.
Determining pregnancy status of females is important for producers, not only to help them plan for calving season, but to also analyze overall reproductive efficiency of the herd. Females that are not pregnant (open) should be sorted off from the rest of the herd and either re-bred and entered into a fall-calving herd, placed on feed to add weight and value before being sold (if economically feasible) or sold immediately to decrease winter feed costs. In addition to sorting off opens, producers should also consider different management for late calving, young, and thin cows.
Body Condition Score
As cows are leaving the chute after preg-check is also a good time to estimate her body condition score (BCS). A BCS is a visual evaluation of the energy reserves of an animal. This score is based off a 1 to 9 scale, with 1 being emaciated and 9 being obese. BCS should be done several times during the year (calving, breeding, weaning) in order to determine if cows are performing efficiently or if nutritional strategies need to be adjusted. In terms of reproductive efficiency, cows perform most efficiently at a BCS of 5 to 5.5. Therefore, if a female is at a BCS less than desirable at weaning time, a nutritional plan should be implemented to get her to the appropriate score by calving time. Cows are in mid-gestation at preg-check time, which is also when the maintenance requirements are their lowest; thus, this is the most economical time to add condition. A description of each score (1-9), including pictures, can be found in the iGrow publication Basics of Body Condition Scoring.
In order for a cow to remain in the herd, she needs to contribute revenue to the operation; therefore, becoming pregnant and weaning a healthy, productive calf each to year is necessary. While there is a cost associated with implementation of these practices, they can also improve management, efficiency and overall profitability of an operation.
Source: Taylor Grussing, South Dakota State University