1. HEAT DETECTION CHAPTER 3
In this section we will be learning about a critical component to the success or failure of an A.I. program. Follow along in your manual beginning on page Feel free to ask questions and to take notes as we discuss this most important component.

2. What is Heat? Also Known as Estrus
Is the Period of Sexual Receptivity of Open Cows and Heifers
Normally Occurs Every 18 to 24 Days
Remember every cow is an individual, so focus on the range not the number of days.

3. Why Heat Occurs Egg Develops in Cow’s Ovary Egg Released
Produces Estrogen
Estrogen Causes Changes in Reproductive, Circulatory and Nervous Systems
These Changes are Observed as Signs of Heat
Egg Released
Progesterone is Secreted From Yellow Body (Corpus Leutum)
Yellow Body Develops at Site of Collapsed Follicle
Progesterone Suppresses Egg Development and Heat Signs for 3 Weeks or Duration of Pregnancy
As we discussed in the Physiology section, the heat cycle is controlled by two hormones, Estrogen and Progesterone. Estrogen causes the external signs of heat to occur, making A.I. possible. Progesterone keeps her from coming into heat for the duration of a pregnancy, or if not pregnant, for about days.

4. When is Cow Fertile? Only Occurs When an Egg Has Been Ovulated
Released From an Ovary
Occurs 10 to 14 Hours After Heat Ends
Heat Lasts 8 to 18 Hours
For Highest Fertility Insemination Should Occur in Later 2/3rds of Heat
About 24 Hours After Cow Enters in Standing Heat
Sperm Needs Time in Reproductive Tract Before Capable of Fertilization
Sperm Survives About 24 Hours in Reproductive Tract
Obviously a pregnancy can occur only when an egg is present for the sperm to fertilize. Knowing that the egg is released after the external signs of heat such a standing to be mounted end, and that the sperm will last about 24 hours in the female, we want to breed her in the latter 2/3rds of heat to increase our odds for pregnancy.

5. When to Inseminate
Here we see that sperm are viable for 24 hours and that it takes them 8 hours of that time to reach the oviducts where fertilization will occur. Note that the egg is released at the end of the heat and will be viable for about 8 hours. This diagram illustrates the logic for breeding in the latter part of the heat. We want the egg to be present when both it and the semen are at high levels of viability.

6. Primary Heat Sign Surest Sign of Heat is
Female Stands to be Mounted by Another Animal
Known as Standing Heat
Best Sign of a Cow’s Fertile Period
Cows in Heat Group Together and Mount Each Other
A female that stands to be mounted is positively in heat. Understanding that cows that are coming into heat, in heat, and going out of heat, tend to group together helps improve detection by narrowing the search. Remember the one that stands is in heat for sure, the one jumping may or may not be in. She may be coming in, or going out.

7. Secondary Heat Sign 1 Mounting other cows
Cows in Heat Try to Ride Females Not in Heat
REMEMBER, Only Cows Standing for Mounting are in Heat
Cows That Ride May or May Not be in Heat
Which one of these cows is in heat? We can bet the house on the one standing, the one jumping I’d like more signs before being sure. Let’s look at some signs that could confirm it.

8. Secondary Heat Sign 2 Roughened Tailhead
After Standing to be Ridden Hair on the Tailhead is Rough or Rubbed Off
Easier to Notice During Winter When Hair is Longer
Muddy Forefeet of Rider Animal May Leave Marks on Lower Hips, Sides or Shoulders
Rough hair,or in some cases the hair rubbed off the tail head can be an indication that she was ridden, this is where the logic for tail chalking and heat aids such as the Kamar came from. If mud is present, you may see it on the flanks and hips of the animal that has been ridden.

9. Secondary Heat Sign 3 Friendly
Cows in Heat May do the Following to Other Cows:
Follow
Stand Beside
Put Their Head on Backs or Rumps
Sometimes They will Sniff, Nuzzle and Lick
Unusually friendly, she’s trying to attract a mate.

10. Secondary Heat Sign 4 Nervous and Restless
Cows Become Nervous and beller More Than Usual
Signs of Restlessness
Walk in Search of a Bull
Pace the Fence
Pay Close Attention to People Working Nearby
When in heat the cow looks for the bull to mate with, this is why she bawls more, paces, and watches with interest anything that moves.

11. Secondary Heat Sign 4
Dairy Producers Can Identify Approaching Heat by:
Alert, Bright-eyed, Nervous Appearance
Drop in Milk Production
A drop in milk production can occur because of the increase in her activity, instead of eating and resting she will be on the move trying to find a mate.

12. Secondary Heat Sign 5 Clear Mucus From Vagina
Mucus Hangs in Strings From the Vulvar Opening
May Also be Smeared on the Tail or Buttocks
During Heat Reproductive Tract Secretes Stringy, Clear Mucus
Looks Like Egg White
Another sign of heat is clear mucus.

13. Secondary Heat Sign 6 Changes to the Vulva
Vulvar Lips Look Moist and Slightly Swollen
Cow Not in Heat Has Dry, Finely-Wrinkled Vulvar Lips
Subtle changes occur to the vulva, a cow in heat will look a bit swollen and moist, the hairs around the vulva will be matted. The inside of the lips will be a brighter pink because of the increased blood flow. These signs are easier to observe in dairy cattle because they are confined, however, they occur in the beef cow too.

14. Prior Heat Sign Bloody Mucus Sign of Earlier Heat
Not a Consistent Sign
Often Observed Between Second and Fourth Days Regardless of Whether Cow Has Settled
Bloody Discharge is NOT a Sign of Heat
Simply Means Animal Was in Heat Several Days Ago
Watch for Next Heat Cycle in About Days
Bloody mucus is sometimes observed. This is a positive sign that the cow was in heat. It usually occurs 2 or three days after the heat. When observed mark your calendar. It is not an indication of pregnancy.

15. Time of Heat Traditional Dairy or Beef Herds
Cornell University Study Reported:
22% of Cows Show Heat Signs Between 6 a.m. and Noon
Between Noon and 6 p.m. the Percent Exhibiting Heat Signs Dropped to 10%
The Percent Increases to 25% Between 6 p.m. and Midnight
This validates the logic for watching for heats early in the morning and late in the afternoon or early in the evening.

16. Length of Heat Confinement Housing
Recent data From Virginia Tech Institute Indicates:
Estrus Expression is Getting Shorter
Both Mounts and Length of Expression
This is likely because of management practices effecting the cows environment, such as, 3x a day milking, feed push up times, etc. In these situations more intense heat detection is needed.

17. Some Heat Detection Aids
Heat Watch © System
Pedometry
Chin-ball Marker
Androgenized Animals
Kamar ® Heatmount Detector
Tail Chalking
Records
Checklists
Milk Progesterone Tests
Heat detection aids range from High-Tech to simple chalk. Pages 3-5 to 3-9 of your manual have the specifics on these.

18. Heat Watch© System Electronic Heat Mount Detection System
Electronic, Pressure Sensitive Transmitters are Glued to Tailhead
When Animal is Mounted Trasmitter Activated
Sends Electronic Signal to Receiver
Receiver Sends Signal to Buffer for Storage
HeatWatch Software Downloads Data From Buffer
Producer Can Keep Information as Long as Desired
Historical Data Can be Used to Track Mounting Habits of Animal for Future Breeding Decisions
The transmitter sends info to the receiver to be viewed on a computer.

19. Heat Watch© System Product Offers:
Twenty-four (24) Hours a Day / 365 Days of the Year Monitoring Heat on Enrolled Animals
Can be Used on Cows and Heifers
Measures Actual Mounts
Not Just Walking Activity
Does Not Need Expensive Parlors or Gates
Shows When Mounting Starts to the Minute
Provides the ultimate, 24-hour observation. Pin points onset of estrus, and counts the number of mounts.

20. Heat Watch© System
This is what the patch containing the transmitter looks like.

21. Pedometry Mounted on Leg or Around Neck of Animal
Measures the Activity of Animal
Secondary Sign of Heat
Animals in Heat Have Higher Body Movements Than When Not in Heat
Information Can be Automatically Downloaded
Historical Information is Helpful when Interpreting Activity Based Information
A leg band or a neck chain with a transponder are the most frequent types of these. When in heat remember that the cow becomes restless, paces, etc. this is what is measured. It is then compared to a normal amount of activity to make a decision as to heat or not.

22. Chin-ball Marker Worn Beneath Detector Animal’s Chin
Consists of Dye Reservoir With Steel Ball Valve
Attached to a Strong Leather Halter
When Detector Animal Mounts Cow Device Acts Like a Ballpoint Pen
Leaves a Mark on the Cow’s Back and Rump
The Chin-ball is a halter with a paint reservoir. When the animal wearing it mounts the animal in heat a paint mark is left on the in heat animal. There is a learning curve to reading the marks.

23. Chin-ball Marker
Here you see the Chin-ball Halter, and a marker animal mounting with one on.

24. Androgenized Animals Females Injected or Implanted With Testosterone
Synthetic Male Hormone
Stimulate Females Into Showing Male-Like Behavior
Cows That Loose a Calf, Open Cows and Cull Cows are Excellent Candidates
Marker animals can be female or altered males. Androgenized cows are treated with testosterone and work very well, reducing the danger of having a bull with the herd.

25. Kamar ® Heatmount Detector
Plastic Device Glued to the Tailhead
Use on Cows Eligible for Breeding During Next 21 Days
Prolonged Pressure from Mounting Animal Turns White Detector Red
At Least 3 Seconds of Full Weight are Necessary to Change Detector’s Color
Means a Cow Must Stand to be Mounted
The Kamar has been around for a long time and helps to identify cows that have stood to be mounted for at least 3 seconds. Make sure that there is nothing for the cow to rub on to reduce false readings.

26. Tail Chalking Tail Chalking is Used in Larger Dairies
Chalk is Applied to Tailhead of All Animals
Chalk is Applied Daily
Animals Riding the Cow in Standing Heat Will Smear or Rub Off the Chalk
Must Become Skilled in Interpreting the Marks
Tail chalking also works to ID cows that have been standing. It takes time to learn to read the marks. Was the chalk rubbed from riding, or licked off, etc?

27. Tail Chalking
Freshen chalk daily for best results.

28. Records
A Good Record Keeping Program is Economical for Both Dairy and Beef Producers
Dairy Herds
Recording Heat Detection and Insemination Information
Barn Charts, Individual Cow Record Cards and Heat Expectancy Charts Can be Used
Beef Herds
Identify Cattle and Record Insemination Information
Allows for Easier Heat Detection and Better Overall Herd Management
Beef Herd Record Book and Heat Detection Record Book Can be Used
How can you determine progress without them? Records help spot trends and allow managers to be proactive.

29. Checklists
Use Heat Detection Checklists as Part of Herd Health Program
A 24-Day Checklist Should List All Open Cows
Listed Cows Should be More Than 30 Days Fresh
At Least 85% of Listed Cows Should be Observed in Heat
Having a checklist helps keep things on track. Knowing what cows to watch and when to watch them will improve the number of heats caught.

30. Checklists
Here’s a check list example. (discuss with class)

31. Milk Progesterone Tests
Measures Progesterone Level in Milk
Progesterone is at Low Level Just Before, During and Just After Heat
Progesterone Levels Indicated by a Color Reaction
Lower Level = Greater Reaction
Used together with observation, it confirms heats. To get pregnant the cow must be in heat.

32. Errors in Heat Detection
This chart illustrates the percent of cows that were not in heat when these signs of heat were observed.

33. When to Inseminate - Dairy
Cows May Show First Heat Period 2-6 Weeks After Calving
That Doesn’t Mean Cow is Ready for Insemination
Cow’s Uterus Takes at Least 40 days to Completely Recover From a Previous Pregnancy
If There Were Complications After Calving Uterus Will Need More Time to Heal
Give her time to repair, breeding too soon will not improve pregnancy rates.

34. A.M - P.M. vs. Once-A-Day
Studies Have Found Cattle Can be Inseminated Over a 24 Hour Span With Acceptable Fertility
Fertility Was the Same for Cattle Inseminated Once-A-Day or By the A.M.-P.M. Rule
Good Calving Rates Can be Obtained by Inseminating Cattle Over a 24 Hour Interval After First Heat Observation
Optimum Time for Insemination Was Hours After Detection of Heat
Estrus is a random Event
95% of Cows Ovulate Between 17 and 38 Hours After Standing Heat Starts
A.M.-P.M. meant that if the cow was observed in heat in the morning she was bred in the afternoon, and vice versa if she was observed in the afternoon. Today we know that once-a-day insemination is just as effective, if used with good heat detection practices.