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You Can Breed Heifers At A Lighter Weight

The market value of a weaned heifer calf and feed consumed from weaning to calving are the two biggest costs in raising replacement heifers.

So if you want to shave some cost from replacements you have to look at the feed bill. John and Adele Popp of Erickson, Man., have successfully reduced the cost of raising their replacement heifers by restricting the rate of gain so they reach 55 per cent rather than 65 per cent of their mature body weight at breeding. The savings on feed carry over for the next five or so years as these smaller-bodied heifers grow to eventually reach their full mature size. Yet their offspring retain the genetics to gain to their full potential.

The long-standing industry practice of feeding heifers to reach 65 per cent of mature body weight by breeding is based on U.S. research dating back to the early 1960s, but John says genetics have come a long way since then.

His own program began seven years ago with a trip to Nebraska to learn more about developing heifers on a restricted-feed system. Researchers with the USDA and universities in Nebraska and Montana have been studying this concept since the late 1990s. A long-term study to evaluated intergenerational effects is now in its 10th year at the Fort Keogh Livestock and Range Research Laboratory in Montana.

The Popps made it a practice to retain heifers from their own Simmental- Angus herd after finding purchased heifers didn t last more than a couple of years in their environment. Erickson is located in rolling Parkland south of Riding Mountain National Park where tame legume and grass forages are abundant and forested areas provide ample shelter for winter grazing.

Replacement heifer selection begins at birth when they have a chance to closely examine each calf, noting details such as udder, feet and leg conformation that may go unnoticed in the fall when they make the final decision. The potential replacements are identified with a notch in the dangle tag to ensure that they don t receive growth implants when vaccinated.

The Popps calving season begins in May and the heifer calves wean off at about 450 pounds at six months of age. Winter sees them bale grazing on good-quality hay free choice supplemented with four pounds of screening pellets per day. They target 1.25 to 1.5 pound of gain per day rather than the typical 1.7 to 2.0 pounds by restricting the supplement portion of the ration. As a result the heifers grow more slowly in frame size during the winter, setting them up to make efficient use of the grass on summer pasture.

The heifers weigh 700 to 750 pounds by breeding time in July when they are exposed to the bulls for 80 days. The Popps confirm pregnancies in the heifers by drawing blood samples 30 days after the bulls have been pulled. The lab test costs $4 per sample but this way open heifers can be marketed right away

rather than waiting until the herd is pregnancy checked later on.

The following winter as bred heifers, they bale graze with the cows just as they will be expected to do in the years ahead. The heifers weigh approximately 950 pounds at calving time in May.

Any heifer or cow that looks thin at any point during the winter is placed with the replacement heifers to receive the screening pellets. They also supply free-choice, trace-mineral, loose salt mixed with polysaccharide chelated minerals, which Popp prefers because 98 per cent of the mineral in this form is bioavailable to the rumen and hind gut. (For more information about the minerals,

The Popps overall objective is to save on feed. Instead of feeding 1,400-pound cows, they are feeding cows that weigh 1,250 to 1,300 pounds on average for about half of their lifespan. That s upwards of 150 pounds of cow they don t have to maintain for that amount of time.

Consuming 2.5 per cent of body weight, a 1,400-pound cow eats approximately 35 pounds a day versus just over 31 pounds for a 1,250-pound cow. If hay costs three cents a pound, that difference of four pounds a day shaves 12 cents per cow every day off the winter feed bill. For a 200-head herd, it adds up to $24 per day, or $4,320 over a 180-day winter.

It has been five years since they began developing heifers on the restricted-weight gain. In that time Adele says they haven t seen any increase in calving difficulty or decrease in the rebreeding rate compared to heifers raised to 65 per cent of their mature weight by breeding. The heifers have good milk and mothering ability. The only difference is the smaller frame size.

Similar to other commercial herds, they expect to trim three to five per cent of their breeding herd, including the heifers, each year. Otherwise, they say, they re not pushing hard enough to ensure continued genetic improvement by selecting the most productive and functional animals.

This isn t about targeting thin heifers, they stress. If feed is restricted, either by quantity or quality, to the point where it doesn t meet the heifers nutritional requirements to continue to have cell division and grow, they will become stunted and will never be able to recover from that loss, explains John, who holds a PhD in ruminant nutrition. This is why he stresses the importance of starting replacement heifers on screening pellets or grain at weaning. The supplement can easily be increased without causing digestive upsets during cold snaps in order to prevent them from slipping into a negative energy balance.

They still need to be able to function in our environment and do what we ask them to do that is, to be tough, go out and forage and raise a calf every year, he says.

He feels this restricted development technique would be efficient and cost effective for any breed or crossbred beef heifer. The important point to note is that they are reducing the weight gain on development, not cow body condition. Under no circumstances do they advocate starving heifers or cows.


The Research

Dr. Jim Wiltbank was among the earliest researchers to study breed, age and weight effects on puberty in heifers during his tenure with the USDA s former research station at Fort Robinson, Nebraska, from 1958 to 1965. He developed the long-standing guidelines for managing heifers during the period when the beef industry was shifting to calving heifers for the first time at two years of age rather than three years of age.

The next significant change wasn t until the mid-1980s when researchers discovered that bulls with larger scrotal circumferences sired heifers that reached puberty earlier than those from sires with smaller scrotal circumferences. As breeders adopted the use of scrotal circumference as a selection tool, heifers began reaching puberty at an earlier age, regardless of weight.

Today, economics are such that heifers must be able to conceive early in the calving season and continue to do so throughout their lifetimes in extensive and extended grazing systems. Some researchers believe that feeding heifers to 65 per cent of their mature body weight at first breeding may maximize pregnancy rates, however, the practice may also be propping up inefficient heifers and end up reducing overall profitability.

A three-year study, Cost-Effective Heifer Development, is investigating alternative heifer development that has the potential to decrease costs and impact future adaptability of heifers as mature breeding females in extensive grazing systems. It is being conducted by Dr. Bart Lardner at the Western Beef Development Centre s Termuende Research Ranch, near Lanigan, Sask., and Dr. Rick Funston, at the Gudmundsen Sandhills Laboratory and West Central Research a
nd Extension Centre, University of Nebraska-Lincoln.

In Saskatchewan, the study is comparing development of spring-born heifers managed in either field bale grazing or drylot pens to achieve a pre-breeding target of either 55 or 65 per cent of mature body weight. In Nebraska, heifers will be managed on either corn stalks, winter rangeland or in drylot pens. The study will determine the effects of each management system on heifer and cow reproductive efficiency, such as age at puberty, conception rate, pregnancy rate, calving interval and animal performance. The costs for each development system will also be collected.

Lardner reports that the first year results went very well, with heifers achieving targeted pre-breeding weights and performing well on pasture and during breeding season. Pregnancy rates ranged from 84 to 90 per cent in Saskatchewan and from 81 to 88 per cent in Nebraska.

Funston presented an overview of research to date on this subject at the 2007 Range Beef Cow Symposium. The paper written by Funston, his associate, Jeremy Martin, and Andy Roberts of the Fort Keogh lab, Heifer Development Then and Now, and related research are available on the University of Nebraska-Lincoln extension website (www.extension.

According to the paper, most research reports up until

the late 1980s continued to show that limiting post-weaning growth had a negative effect on age of puberty and pregnancy rates.

Around the late 1980s, reports began to reveal that the association between body weight, puberty and heifer pregnancy rate had changed. Subsequent studies indicated that delaying heifer gain until two to three months prior to breeding season reduced the amount of feed required, while calving rate, age at calving, postpar tum interval, and second-year pregnancy rate were not affected.

Evidence supporting a genetic basis for the difference between the early years and today was presented in a 1997 study. While the age and weight at puberty was similar in heifers AI sired by bulls born after 1988 compared with those sired by bulls born between 1982 and 1984, the pregnancy rates were higher in offspring from bulls born after 1988.

In 2004, Funston was involved with a study showing that heifers developed to reach either 53 or 58 per cent of mature weight prior to breeding had similar pregnancy rates from the initial breeding through the fourth breeding.

Continuing with the same herd, Martin found that extending the breeding period from 45 days to 60 days for heifers developed to weights as low as 51 per cent of mature weight at first breeding resulted in similar first-calf conception rates and no difference in second-calf conception rates than the group developed to 57 per cent of mature body weight at first breeding.

The Fort Keogh study began in the winter of 2001 with the control group of heifers fed according to industry guidelines and the restricted group fed according to body weight, which works out to about 80 per cent of the feed provided to the control group. After breeding, the groups graze together until fall when they are sorted into their original groups for the winter feeding period. Again, the restricted group receives about 20 per cent less feed.

This study indicates that age at the beginning of breeding season is more critical than body weight for a successful pregnancy. Furthermore, given a pre-breeding body weight, the cumulative pregnancy rate through the years for heifers developed in the feed-restricted program is greater than that for the control group.

In 2011, Roberts notes that restricting feed as a replacement heifer seems to have improved the efficiency of the second generation in the restricted-feed system. Cows raised in the restricted-feed program are more likely to remain in the herd until at least five years of age, which is when a cow reaches maximum production as measured by the weight of the calf at weaning. Restricted cows from full-fed dams had the lowest rate of retention until age five.

The studies at both locations have consistently shown that restricting feed during the post-weaning period reduces input costs, improves efficiency during the winter feeding period, and increases rates of gain on pasture the following summer.

While the Fort Keogh study limits the amount of feed, the Nebraska studies have restricted growth by providing a lower-quality diet. Studies are now focusing on how the timing and level of energy and/or protein feed supplements during the post-weaning period affect age at puberty and pregnancy rates.

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