Producers need to provide nutritious feed at the correct time, check body condition and cull those that have problems
SAN DIEGO, Calif. — Fertility and successful pregnancies are the most valuable production traits in a beef operation, says a University of Florida researcher.
“Managing for pregnancy is extremely important,” said Cliff Lamb, who runs a research station in Florida with 300 cows that must have a calf every 365 days.
“We want a cow to ovulate as quickly as possible after giving birth within 20 to 40 days after. Well fed cows should ovulate 50 days after giving birth.”
Cows should calve without assistance if they are to stay in the herd.
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Those with dystocia problems tend to have lower pregnancy rates of up to 10 to 15 percent.
The cows must also provide enough milk for calves to reach their genetic potential and must have a calm disposition.
“One crazy cow makes the rest of the herd crazy,” Lamb said during an education session National Cattlemen’s Beef Association convention in San Diego in January.
He said the pregnancy rate was 85 percent when he took over the research centre. He increased this to 92 percent by improving nutrition and following basic management principles.
The calving interval was shortened, and cows that could not make the grade were culled.
He said nutrition is important for fertility, but the first step is to make sure basic needs are met first.
“When you are feeding animals, the very first thing you have to worry about is feeding for maintenance or basal metabolism.”
Basic feed is needed for cattle to stay alive. Nutrition must then provide energy for activity, growth, lactation and developing a fat cover for energy reserves.
“We have to meet all those other factors before reproduction is met.”
Lamb said mid-gestation is the best time to start manipulating nutrition. Cows need more nutrition for body maintenance and rapid fetal growth during the last trimester, and the fetus may gain up to three-quarters of a pound per day.
Good feed is also needed after calving for lactation and to help the cow recover.
Well-fed cows should ovulate 50 days after giving birth, but it could take them 90 to 120 days before they start their estrus cycle if they are not fed well. Underfed cows may undergo multiple estrus cycles without ovulating.
After weaning the cow can start to gain weight again.
This is when body condition score should be evaluated.
The lowest score is given when the shoulder, ribs and the backbone are visible and means the cow is emaciated.
A moderate score is given when the 12th and 13th ribs are not visible.
A cow in good condition has covered ribs and sponginess around the tail head.
Cows that carry the right amount of weight may be able to push a calf out easier, compared to a thin one that may not have the energy to go through the birthing process.
Lamb said producers don’t check body condition scores enough, but studies have found that thin cows have much lower pregnancy rates. They take at least 89 days to start cycling again compared to those in good condition, which are less than 60 days.
“The condition at which cows calve dictate how soon those cows will come back into heat and get pregnant,” he said.
“Even though you have a cow that is in good condition at calving, if she loses one condition score, it could take 133 days to start cycling.”
The cow may have to gain 260 lb. from weaning until calving, which means gaining 2.2 lb. per day.
The easiest time to do that is right after weaning because it is not easy for a lactating cow to gain two lb. a day.
Gaining the weight before calving means they can then gain more slowly after weaning as they move into winter.
“What we do to a cow during pregnancy affects calf development throughout its life,” he said.
Not getting enough to eat affects the fetus’s muscle fiber and fat development.
As well, calves reach puberty sooner when their dams are supplemented with protein.
Heifers also have improved follicle development of the ovary, which equates to longevity in the herd.
Heifers at Lamb’s research centre are developed slowly at a rate of one-half to three-quarters of a pound per day, which is increased to two lb. per day 75 to 90 days before breeding.
However, their weight needs to be monitored because pregnancy rates will fall if they gain too much or too little.
Heifers exposed to high protein forage or grain supplement gain more during the development phase. It is more expensive to use high protein forage for heifer development, but pregnancy rates are higher among those receiving more protein.
Opinions vary about body weight at puberty.
Some say 60 to 65 percent of mature body weight can work at the start of breeding, while others suggest 50 to 55 percent of mature body weight.
Lamb said there is value in both ideas, but most producers do not know the mature body weights of their cows.
