Determining Pregnancy in Cattle John R

B-1077 DeterminingDetermining PregnancyPregnancy inin CattleCattle Texas Agricultural Extension Service • Zerle L. Carpenter, Director The Texas A&M University System • College Station, Texas Acknowledgments The authors express appreciation to Dr. Bruce Carpenter, Dr. Ron Gill, Dr. Randall Grooms, and Dr. Joe Paschal for their review of this publication and their suggestions regarding its content. Editor: Elizabeth Gregory, Assistant Professor and Extension Communications Specialist Determining Pregnancy in Cattle John R. Beverly Professor and Associate Vice Chancellor for the Agriculture Program and L. R. Sprott Professor and Extension Beef Cattle Specialist Determining pregnancy in cattle is an impor- You can see the economic importance of calf tant management tool. The ability to determine crop and its interaction with weaning weight pregnancy can allow you to make timely culling even more clearly in Table 2. decisions, focusing the resources of your opera- Clearly, break-even prices decrease as calf tion on sound, reliable breeders. With experi- crop and weaning weight increase. This is true ence, you can determine the age of the fetus, under any annual operating cost per cow. which will allow you to predict expected calving dates and plan for the necessary labor at Management Practices to Improve calving time. Pregnancy determination can also Production help you manage feeding to better meet the high nutritional demands of gestation, calving, The challenge for cow-calf producers is to lactation, and rebreeding. use management techniques that stimulate pro- Knowledge of expected calving dates can also duction without drastically increasing operating be an advantage when marketing bred replace- costs. You can improve weaning weight through ment heifers. Potential buyers often want to a number of methods, including: purchase females whose calving dates coincide ■ Internal parasite control. with those of their present herd. ■ Use of growth stimulants. Increasing Herd Productivity ■ Using sires with the genetic potential for increased growth. A cow-calf producer’s economic returns ■ Providing adequate herd nutrition, which depend largely on the percent calf crop and the will also help optimize reproduction. weaning weight of the calves to be sold. You can compute your calf crop percentage by Another effective and inexpensive way to dividing the number of calves raised to weaning improve reproduction is through annual preg- age (7 months) by the number of cows in your nancy testing and culling of subfertile cows. herd at the start of the breeding season. Not every open cow can be culled, because of market conditions and forage availability. When Percent Calf Crop and Weaning Weight culling is possible, the repeat breeder cows, those that have never calved, and inconsistent Table 1 shows the cost per pound of calf pro- calvers should go first. If you follow this prac- duced for various production levels, with an tice annually and your cows are under other- operating cost of $250 per cow per year. To wise good management, pregnancy rates will determine the required level of production for increase. Not only that, but Table 3 shows that this example, take an arbitrary selling price of the increases in the pregnancy rate in Texas test 70 cents per pound and locate the break-even herds were sustained at an acceptable level. point in Table 1. You will find that, for this example, weanling calves weighing 400 pounds Visual observation is also important in culling require a 90-percent calf crop to break even. If decisions. Some pregnant cows should be culled only a 60-percent calf crop is produced, then on the basis of age, or conditions of the udder, the cost per pound of calf is 34 cents higher feet, legs, and teeth that make them poor breed- than the 70 cents market value. Calves weighing stock. The decision to cull an open cow may ing 450 pounds break even at an 80-percent calf also depend on her reproductive history. A crop, and 500-pound calves break even at mature cow that has consistently calved approximately a 70-percent calf crop. throughout her life and is unexpectedly found open can be retained in the herd. Research indi- cates that this is an acceptable option, especial- Table 1. Production Cost Per Pound of Calf — ly if replacement costs are higher than the cost $250 Per Cow Operating Cost. of retaining the open cow. Nevertheless, if this Weaning weight (lb.) 550 500 450 400 350 same cow is again found open later in life, you Calf Crop (%) 5501 500 450 400 350 should remove her from the herd. 100 45.52 50.0 55.6 62.5 71.4 Culling decisions may also depend on the 90 495 450 405 360 315 animal’s monetary value. You can retain highly 50.5 55.6 61.7 69.4 79.4 valued registered females that fail to conceive 80 440 400 360 320 280 until some or most of their initial cost is recov- ered. This strategy is prudent as long as these 56.8 62.5 69.4 78.1 89.3 animals are free of abnormalities of the repro- 70 385 350 315 280 245 ductive tract and have previously produced at 64.9 71.4 79.4 89.3 100.2 an economically acceptable level. 60 330 300 270 240 210 75.8 83.3 92.6 104.1 119.0 Palpating to Determine Pregnancy 1Top figures indicate pounds of calf produced per cow. The following is a description of pregnancy 2Bottom figures relate the cost per pound of calf, cents. determination. This determination, called palpation, is made by inserting the arm into the rectum and feeling the reproductive tract for pregnancy indications. Table 2. Break-Even Prices at Various Levels of Production and Annual Costs of Production. Calf crop Annual costs per cow (%) Weaning weight (lb.) Pounds of calf per cow $250 $275 $300 90 500 450 $.561 $.61 $.67 80 450 360 $.69 $.76 $.83 70 400 280 $.89 $.98 $1.07 60 375 225 $1.11 $1.22 $1.33 1Breakeven prices per pound of calf, dollars. Equipment Table 3. Effects of Annual Pregnancy Testing and Culling of Subfertile Cows on Little equipment is needed in palpation. The Subsequent Herd Fertility. individual doing the palpating should wear a protective plastic sleeve that covers the arm and Percent Pregnant by Year hand up to the shoulder. The sleeve guards 12345 against disease and prevents irritation of the arm. Use a rubber band on your upper arm to Herd hold the plastic sleeve in place. Use an obstetri- 1 7597969398 cal lubricant or mineral oil to make entry into 2 64568489-- the rectum easier. Don’t use soap or detergents as a lubricant, since both are irritants. Plastic 3 5966799285 sleeves may tear after several uses, reducing 4 859094---- protection. If the sleeve tears, replace it before 5 82949393-- palpating the next animal. 6 7476869498 The chute for holding the animal during pal- 7 4989928989 pation should allow her to stand in a normal Sprott and Carpenter, 1994; Unpublished data. position. It should have a front wall or gate and 2 a bar just above the animal’s hocks in the rear that endocrine glands located in other parts of (Figure 1). This bar keeps the cow from kicking the body, particularly the brain, are also and protects the palpator. Include an entrance involved in the sexual cycle. Figure 2 is a gener- gate in the chute at the rear of the animal to al diagram of the reproductive tract. allow the palpator to enter and exit easily. The vulva is the external portion of the Provide a gate to swing across the crowding reproductive tract and can be seen as two chute and fasten in front of other animals com- prominent lips. The size of the vulva may vary ing behind the palpator. You may use squeeze with age of the animal and between breeds. chutes, but catching the cow’s head is not nec- Brahman-influenced females usually have a essary for this procedure. larger vulva than do cattle of English and European breeds. The next portion of the tract (moving right to left, as shown in Figure 2) is the vagina, and it serves as a receptacle for semen during natural mating. It is a thin-walled structure and is not Figure 1. Chute arrangement for restraining cows. easily felt during palpation. Palpation alone takes only a few seconds. The The urinary bladder (not shown in Figure speed of pregnancy determination depends on 2) is located underneath the vagina and may the management of the cows as they come extend beyond the pelvic brim and slightly into through the chutes, the stage of pregnancy, and the body cavity, particularly when it is full of the palpator’s experience. Under ideal condi- urine. During urination, the bladder empties tions, an experienced palpator can examine sev- through a small opening (urethral orifice) on the eral hundred head of cattle in a normal working floor of the vagina, eventually exiting the body day. However, the process is much slower if the through the vulva. palpator has to help bring the cattle into the The cervix is a thick-walled structure chute or climb over the chute wall to get attached to the vagina. It is composed of con- behind the animal to palpate her. nective tissue, which feels much like gristle. To ensure the safety of the animals and the Because of its thickness and firm feel, the palpator, you must practice certain precautions: cervix is a good landmark for orientation while you are palpating. The internal walls of the ■ Restrain the animal so she cannot jump cervix are folded and protrude toward the exte- over the side of the chute or kick the pal- rior of the reproductive tract.

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