Rearing Replacements
Introduction
The optimal average daily weight gain of a dairy heifer and the optimal age at first calving are controversial issues. Producers must realize that recommendations arising from research findings resulting from work conducted under controlled conditions may not be cost-effective commercially.
Criteria to Consider Proir to Puberty
Udder tissue grows at a relatively faster rate than other body tissues until the 2nd or 3rd estrus cycle (Sejrsen et al 1982). If body growth is accelerated during this period, udder tissue can be impaired by 48% (Capuco et al 1995).
In 1989 the Agriculture Research Council (ARC) recommended that the ratio of crude protein to metabolizable energy should be 60g/Mcal for heifers 3 to 6 months of age and decreased to 50g/Mcal for heifers 6 to 12 months of age.
Take-home message |
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Do not accelerate the average daily weight gain of heifers before they have had their third estrus cycle. |
From Breeding to Calving
Optimal body weight before calving should be 1,400 lbs which means a weight of 1,250 lbs after calving. Higher weights may imply the presence of excess fat which will compromise milk yield (Van Amburgh et al 1998a & b; Grummer et al 1995).
Optimal body score at calving should be 3.0 to 3.5, body length 66-68 inches and wither height 54 to 56 inches (Hoffman 1997).
Primary goal should be to maintain an average daily weight gain of 0.77g (1.69 lbs) to 820g (1.8 lbs) (Quigley 1997).
The earlier that puberty takes place, the lighter in weight will be the heifer. Heifers light in weight at puberty cannot achieve adequate calving weights without dangerously high average daily weight gains. The same would apply in the case of small-framed heifers.
Sole Hemorrhages
It is accepted that hemorrhages in the sole are indicative of the presence of sub-clinical laminitis in an animal or group of animals (Nilsson 1963; Maclean 1971; Andersson and Bergman 1980; Greenough and Vermunt 1991; Bergsten 1994).
High sole-hemorrhage scores occurring in heifers soon after calving that have been fed high levels of concentrates in early gestation are an indicator of laminitis (Bergsten and Frank 1995).
How to Measure Sole Hemorrhages
Remove enough horn from the surface to the sole to be able to see the texture clearly.
Evaluate each of the eight claws using the following scoring system.
Sole Hemorrhages |
Score |
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0
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no hemorrhage |
0
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1
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slight hemorrhage covering a small area |
1
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|
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2
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slight hemorrhage covering a large area or a moderate hemorrhage covering a small area |
2
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|
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3
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Moderate hemorrhage covering a large area |
4
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|
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4
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Severe hemorrhage covering a small area |
8
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Final Score |
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If the score is ten or greater in an individual animal, it can be assessed as having a potential problem. If a group of heifers has an average score of ten or greater, the heifer-rearing protocol should be reviewed. |
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Age at First Calving
Heifers typically conceive at 16 months weighing 910 lb and calve at 25 months weighing 1360 lb before calving (Hoffman and Funk 1992).
Many arguments are made to justify, on economic grounds, calving as early as 22 months. (VandeHaar 1998) does not consider the risk (of reducing productivity) to be worth-while.
Can we be sure that two or three months of extra milk early in life does not shorten the average animal's life, when she is in peak production, by the same number of months?
The literature does not deal fairly with the issue that early calving may affect the useful or functional life of a herd. In many areas, the average life of dairy cows is already unacceptably short. Logically, stresses placed on a mature heifer are less likely to compromise the animal's health that would be the case in an immature heifer.
Claws probably keep growing until at least 26 months of age. Rapid increases in weight must impose mechanical strain and could account for the claw hemorrhage seen in heifers soon after calving.
Discussion
It is my experience that more producers complain today about lameness problems in heifers than they did even a few years ago.
I am convinced that in any herd in which a laminitis-like problem exists it is essential to review the status of the feet of heifers early in lactation.
It is undeniable that heifers can calve as early as 20 months of age and can flourish if everything can be guaranteed to be as controlled as it would be in a scientific experiment.
In any herd with a lameness problem, I would strongly recommend against an average daily weight gain exceeding 800 g (1.75 lb) between breeding and calving.
