Sync Est | Beef Magazine

Heat synchronization is commonly used in the artificial insemination industry.

Normally we don’t talk about synchronization with natural service operations. However, it can still be a very useful management technique in natural service situations.

A frequently asked question is, “Can my bull breed each cow or heifer effectively if they all come into heat at the same time?”. The answer is yes. Bulls should be experienced, around 3+ years, have a BCS of at least 6 and have a scrotum circumference of at least 34 cm. The bull should also have passed a breeding suitability test. If the bull possesses all these qualities, he can sire eleven cows a day.

The economic impact of synchronization is evident when you bring a potload of calves to market. Larger groups of cattle of the same type and size bring in more money. The difference in value between calf-sized calf groups and smaller groups can be seen almost daily in sales across the state and across the US. The table above shows the potential of different sized calves born to unsynchronized cows and outlines the calf weights between calves born in the first cycle and calves born in subsequent cycles. Apparently, calves born in a shortened calving season are more uniform in size and weight.

For example, during the week of October 26, 2021, two groups of steers of the same breed and color with similar management were sold on the same day at the same auction. A group of fourteen steers weighed 588 pounds and fetched 150.50 per hundredweight (cwt) for a total value of about $885 per head.

Another group of ninety steers weighed 589 pounds and made 164.25 per cwt. That’s a total value of about $967 per head. That’s a difference of $82 per head just because you have a lot of calves.

One of the ways to make your herd of calves more similar in weight is through synchronization, whether you use artificial insemination (AI) or natural breeding. In this article we will discuss heat synchronization in natural breeding programs. Three protocols that we will discuss in detail and the pros and cons are: 1. Prostaglandins. 2. MGA and 3. Use of CIDRs

Prostaglandins end the normal cycle and allow the cow to ovulate and start a new cycle. Using prostaglandins is the cheapest and lowest way to synchronize estrus in your herd. Prostaglandin protocols are approved for use in adult cows and heifers. Cows only have to be sent through the barn once and the drug is relatively cheap.

However, when using prostaglandins in cattle, they found ineffectiveness in anoestrous cows (not in heat) and prepubescent heifers (not sexually mature). For prostaglandins to be effective, cattle must have a body condition score of at least 5 and show signs of heat.

The protocol for using prostaglandin is that you bring your bull out at the normal time (day zero) and the females are given a prostaglandin injection on day four. Below is a chart that explains when to steer and prostaglandin doses to achieve your desired calving date.

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MGA (melengesterol acetate) is a product that can be fed as a supplement and contains progestin. MGA is labeled for heat suppression in heifers and is not approved for use in adult cows.

Heifers must be fed MGA for fourteen consecutive days, and after ten days of withdrawal, heifers start estrus two to six days later. This will be a subfertile heat and heifers should not be bred. The bull should be driven out with the heifers after the tenth day of waiting. MGA can be a good option for cattle producers without a cattle treatment facility.

MGA application can be challenging as each heifer needs to be fed half a milligram of MGA daily for a fortnight for it to work. Careful management of the feeding grounds must be carried out. If you have ravenous eaters, you may consider separating them to ensure other heifers have a chance to consume the half milligram per day. Below is a table describing when MGA should be fed and the sire should be handed in at the desired calving date.

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Using a CIDR is another way to synchronize heat. CIDRs are vaginal inserts that contain progesterone. They work by mimicking a corpus luteum. The CIDR produces a small amount of progesterone that prevents estrus from occurring.

CIDRs are inserted and removed from the cow seven days later. The bull can be delivered to the females on the seventh day when the CIDR is drawn, and the females should be in heat one to ten days later.

Using CIDRs is the most expensive option and requires the woman to be sent down the chute twice to insert and remove the CIDR. However, this is the most effective tool for initiating oestrus in women and may be effective in women who do not cycle and/or are thin (less than a body condition score of 4).

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Heat synchronization in natural breeding beef programs can have a positive impact on the bottom line for Ohio cattle producers by allowing producers to market calves of the same type and size in the sales pen. Heat synchronization also helps producers save time and energy by shortening the calving season. As a producer, consider which method of heat synchronization is most appropriate for your cattle operation.

Source: Ohio State University, which is solely responsible for the information provided and is fully owned by the source. Informa Business Media and any of its affiliates are not responsible for the content of this information resource.

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