1. Heat Detection in the Cow Floron C. Faries, Jr., DVM, MS Professor and Extension Program Leader Texas AgriLife Extension Service Texas A&M System College Station, TX 77843 http://extensionvetmed.tamu.edu

2. The Mechanics of Estrus The basics of the estrous cycle Why a cow cycles

4. Duration of heat: 1 day (6-30 hrs) Heat Estrus Days between cycles: 20 days No heat Out of heat Between heats Diestrus

5. Cycling Estrous cycle is 21 days (18-24 days) Not cycling Anestrus (no heat)

7. Cow in heat for 1 day Follicle and egg Cow out of heat for 20 days CL develops for 5 days Mature CL for 11 days CL regresses for 4 days Cow comes in heat after CL regresses

8. Age cattle should cycle (puberty) English breeds: 12-13 months Continental breeds: 14-15 months Brahman: 14-18 months Cross breeds: puberty at least 1 month earlier

9. Determination of Timing for A.I. Early Stage of Heat Bawling and walking Butting, trailing and mounting other cows Swollen vulva with redness inside Little if any, clear mucous discharge Cervix is open Uterus is rigid

10. Middle Stage of Heat Complacent and restless Very red and swollen vulva Abundant, clear mucous discharge Slightly matted hair on tail head Rides other cows Ridden by other cows Stands to be mounted (in standing heat)

11. Late Stage of Heat Mount other cows May still be ridden but will not stand Nervousness disappear Vulva swelling and mucus decrease Mucus becomes slightly rubbery Hair on tail head becomes matted

12. Ovulation occurs 14 hours (range 6 to 18 hours) after standing heat ends Slightly bloody mucous discharge occurs about 24 to 48 hours after standing heat ends

13. Proper timing to increase conception rates Heat checks by an observer are 15 to 30 minute durations Repeated 3 to 4 times a day Breed the cow 8 to 12 hours after first mounting (standing heat) When standing heat begins in the morning, breed at night When standing heat begins at night, breed in the morning

14. Health Concerns Non-diseases Persistent heat Persistent follicle Persistent no heat/anestrus Persistent CL Embryonic/fetal deaths Stress Malnutrition

15. Infertility Stress Malnutrition Low reproductive tract scores Low body condition scores Uterine trauma

16. Diseases Embryonic/fetal deaths Vibriosis Trichomoniasis Neosporosis Brucellosis IBR BVD Hemophilus Infertility Uterine infections