The optimal heifer-calving age

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A growing body of research-based evidence suggests there is an ideal age to freshen first-calf heifers. The “magic” number: 23 to 24 months.

Dr. Jim Quigley, Technical and Research Manager with Provimi North America, shares his rationale for this conclusion in a recent issue of his CalfNotes.com newsletter. He says age at first calving (AFC) has been shown in a wide range of studies – both in the U.S. and internationally -- to have a strong influence on a heifer’s ability to make milk. The trend is true in both the first lactation and over her lifetime.

As further evidence, he cites a recent University of Wisconsin study that evaluated the records of 69,145 Holstein cows that calved in 2005. The researchers evaluated the effect of AFC on both first-lactation milk yield and lifetime milk production. They divided the animals into four data sets:

1) 3X milking and rolling herd average (RHA) = 12,750 kg (3X-H)

2) 3X milking and RHA = 11,250 kg (3X-M)

3) 2X milking and RHA = 11,250 kg (2X-M)

4) 2X milking and RHA = 9,250 kg (2X-L)

The following table shows the significant difference in lifetime milk production that occurred when heifers were calved either before or after the optimal window of 23 to 24 months.

AFC, mo.

3X-H, kg

Diff, kg

3X-M, kg

Diff, kg

2X-M, kg

Diff, kg

2X-L, kg

Diff, kg

20

38,545

1,784

33,142

-622

30,211

-2,040

25,156

-2,397

21

38,107

1,346

32,229

-1,535

31,190

-1,061

26,393

-1,160

22

36,655

-106

33,764

0

31,709

-542

26,464

-1,089

23

36,761

0

33,032

-732

32,251

0

27,015

-538

24

36,486

-275

31,332

-2,432

32,078

-173

27,553

0

25

35,846

-915

31,714

-2,050

31,978

-273

26,819

-734

26

35,506

-1,255

31,254

-2,510

31,293

-958

26,917

-636

27

34,780

-1,981

29,821

-3,943

30,415

-1,836

26,449

-1,104

28

33,989

-2,772

29,360

-4,404

30,696

-1,555

25,764

-1,789

29

32,889

-3,872

28,640

-5,124

29,710

-2,541

26,241

-1,312

30

33,110

-3,651

27,835

-5,929

29,717

-2,534

25,029

-2,524

Based on this data, Quigley provides an example of a 3X herd with a rolling herd average of 28,109 pounds of milk that calves its heifers around 28 months of age. In addition to the additional expenses for feeding and housing those heifers for an additional three to four months, that herd would sacrifice approximately 6,111 pounds of milk over each animal’s lifetime. At $23.00/cwt., lost milk income per heifer would total $1,386.00. 

To read the full text of Quigley’s Calf Note, “Calf Note 180 – A Milk Production ‘Penalty,’ follow this link: http://www.calfnotes.com/pdffiles/CNlatest.pdf



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