By Gary Sliworsky
Ag rep, Emo
Cow-calf producers have tough decisions to make in choosing which heifers to keep as replacements or for herd expansion.
Is it the heaviest heifers at weaning, heifers out of favourite cows, or those out of a particular sire, etc.?
Keep in mind getting heifers bred the first year, and re-bred early each year following, is critical to profitability. Many experienced cattlemen are aware of this fact.
The following, from an article by Mark Leahy, farm management advisor with the Indian Agricultural Program of Ontario, provides another consideration when choosing replacement heifers:
Research at the University of Nebraska sheds light on the subject of choosing replacements. Data was taken from a spring calving herd over a 12-year period representing 1,019 heifer calves.
These calves were followed from birth to eight years of age.
Heifers born during the first 21 days of the calving period were heavier at weaning and breeding, and had a higher proportion cycling at the start of the breeding season than those born in the second or third calving periods.
Each calving period is 21 days. Fewer heifers born in the third calving period were pregnant at the end of the breeding season, compared to the first or second calving period.
The advantage of being born early continued with the birth of their first calves, which were five days older than the average of those born to dams from the second calving period.
The yearling replacement heifers that were bred in 2002 and 2003 averaged 58 percent born in the first calving period, 31 percent in the second, and 11 percent in the third.
Of the females that were eight years or older in 2009 and 2010, 72 percent were born in the first calving period.
There is good evidence that heifers born early in the calving season maintain an advantage that helps them to get bred early their first breeding season and remain in the herd longer.
Selection for good feet and legs, adequate milk production, desired mature weight, and other traits still are important.
Actual birthdates, or at least an idea of which 21-day period calves are born, is essential to take advantage of early-born heifer selection.
Selecting based on size alone may result in a larger framed cow herd down the road.
Dates to remember
•Nov. 5–RRFA annual dinner and general meeting, 6 p.m. social hour, Stratton Millennium Hall (tickets available from board members).