MILES CITY, Mont. – The beef industry has recommended for decades that heifers and cows need to be fed very well prior to breeding in order to maximize pregnancy rates, but new research is casting some doubt on that premise.
Over the past 10 years researchers have been conducting studies on the topic, according to Andy Roberts, animal scientist at the USDA Agricultural Research Service’s Fort Keogh Livestock and Range Research Lab in Miles City, Mont.
“The beef industry has traditionally recommended that cows be fed to a minimum body condition and heifers be fed to a recommended 60-65 percent of mature body weight (which occurs around 5-years-ofage) pre-breeding in order to achieve high pregnancy rates,” Roberts said.
In other words, the industry recommended producers meet a very high nutritional standard.
In 2001, scientists at Fort Keogh set out to determine if the industry standard was correct. With feed being one of the highest costs in raising cattle, especially in times of drought, could heifers and cows be fed less and still maintain high pregnancy rates?
Roberts said they decided to do the research because 1) the research was very old (from the 1960s); 2) there has been a great deal of genetic changes in cattle over the years; and 3) not all cows have to be at the recommended body condition prebreeding to become pregnant, Roberts said.
The scientists began the research with around 350 cows at Fort Keogh in the fall of 2001 and extended the research with about 150 of their female calves the next fall, he said. Cattle used in the research were from the Composite Herd (CGC) developed at Fort Keogh composed of 50 percent Red Angus; 25 percent Charolais and 25 percent Tarentaise.
That research has been duplicated and duplicated over the last decade and results continue to come out about the same, Roberts said.
Half of the group was fed to industry standards and half was fed less, he explained. Cows in both groups had access to as much grass on pasture as they wanted to eat while grazing. Cows grazing winter pastures were fed alfalfa hay as a supplementation based on textbook recommendations, Roberts said.
“The research has been repeated every year on all cows that got pregnant and remained in the herd over the last decade and results continue to come out about the same,” Roberts said.
Each year there were some slight differences in the results due to the fact the cows were out on pasture which varied in quality, since some years had lots of rain and the grass grew thick and hardy while in a drought year the grass could be skimpy, he said.
“Results were highly dependent on rain and grass growth,” Roberts said.
Other differences can happen when the research is applied to real-life situations, Roberts said. Cows managed to be smaller cattle may gain more efficiently than cows who are abundantly fed to be fatter cattle. When feed becomes limited, fatter cattle will be more susceptible to losing weight and be adversely affected, he explained.
The cows in the research study were fed alfalfa cake or alfalfa hay to supplement dormant forage three times a week. Cows in the industry standard group were fed an amount that would be equivalent to about 4 pounds per cow per day.
Cows not in the industry standard group were fed what was expected to be marginal levels of the same feed (equivalent to about 2.4 pounds per day), based on average quality and availability of winter feed, Roberts said.
The winter feeding treatments for the cows were started in December and ended in March, just before calving.
In a group fed to industry standards, researchers expect about 10 percent to be open after breeding.
“We knew there would be some failures no matter how they are fed,” Roberts said. “We never observed any differences between the two different levels of supplementation, with the average over the years being about 90 percent pregnant for both groups, with more than 1,000 observations per group.”
Another aspect of the research has been to look at the effect of reducing the amount of feed provided during the heifer development stage of production, Roberts said.
After weaning, all the heifers from the cow trial were put in the feedlot for a 140- day feeding trial from December through April.
Control heifers were fed to industry standards, which was about all they would eat.
Restricted heifers received 80 percent of the same diet (a mix of corn silage, alfalfa and a supplement) as controls depending on their body weight, Roberts said. A 540- pound heifer would not be expected to thrive on the same amount of feed as a 500-pound heifer.
“Over 140 days of the feeding treatment trial, the restricted heifers received 26 percent less feed than the controls depending on their weight,” Roberts said. Heifers were weighed every four weeks, so feed could be adjusted, he added.
After the end of the 140-day trial, heifers were all fed the same.
Beginning around June 1, heifers were AI’d and placed with cleanup bulls over a 46 to 62 day period, depending on the year.
If producers follow the industry standards for feeding, there should be about a 90 percent pregnancy rate after breeding, Robinson said.
“If the group runs a 90 percent pregnancy rate, that is a good rate,” he said.
Scientists at Fort Keogh found about the same pregnancy rates occurring in the limit-fed heifers as in the controls.
“The first three to four years, there was a 2-4 percent difference in the pregnancy rate. The controls had a 91 percent pregnancy rate, and the restricted-fed had an 88 percent pregnancy rate,” Roberts said.
After 10 years, they averaged the pregnancy rates and found no statistical difference between the controls and the restricted-fed cows and heifers, he said.
“It averaged over 10 years to be about an 89 percent pregnancy rate,” Roberts said.
The take-home message is there is an opportunity for producers to save some feeding costs in heifer development, he said.
It is important research because prebreeding feeding definitely affects the producers’ bottom-line, said Roberts.
Their decade-long research is so unique , he added, that it is catching national and international attention.
“We have been invited to give talks around the country and are even garnering international attention,” he said.
One of the most rewarding results is that Roberts and his colleagues have been working with Montana livestock producers, some of whom have adopted the limited feeding methods, and have found it working for their herds.
One producer has saved $40,000 in feed costs in one year, according to Roberts, adding that while he is a large producer that is feeding many cattle, it still is exciting results.
“It means a lot to me that our research can be implemented in real-life situations, and is a cost savings for our producers,” Roberts said. “That is what we are all about.”