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Genomics adds a dimension for dairy heifer raising protocols

March 28, 2013 | 0 comments

What Pat Hoffman considers to the greatest change in the raising of dairy heifers during his 34 years in the field has occurred in the past couple of years. It is genomics - the prediction of expected performance and production based on genomic evaluations.

Hoffman, a University of Wisconsin Extension Service dairy scientist who conducts research at the U.S. Department of Agriculture station near Marshfield, was the leadoff speaker at the final session of the 2013 Progressive Operators seminar series at Lakeshore Technical College.

Although genomics is still in a proving stage, Hoffman considers it to be a vast improvement over such previous upgrades in heifer raising such as the realization that higher protein and butterfat content in milk replacers improved growth rates significantly.

He does not deride the protein step-up, noting that calves have the capacity to use 60-65 percent of the protein they are fed compared to about a 30-percent efficiency by lactating cows.

The various commercial pasteurizers of milk being fed to calves have also been proven to boost nutrients and improve health, Hoffman stated.

He noted that eight of nine major studies of intensified nutrition programs for dairy calves during their first eight weeks paid off with milk production increases of 1,000-3,000 pounds during the animal's first lactation.



A New Era

Hoffman doesn't propose that those practices be discarded but he believes that genomics provides a whole new era or world for raising dairy calves. "We always thought that if we practiced better husbandry in all phases we'd have better animals, better cows," he observed.

But that's like looking at the outside of a car rather than under the hood in evaluating it, Hoffman suggested. He described genomics as being comparable to looking under the hood. "Don't let genomics scare you," he advised.

Genomics can provide an accurate chromosomatic or parental identity of dairy calves shortly after birth or a few weeks afterward. This is done with the testing (minimum cost of $40) of hair follicles or an ear notch (three drops of blood were taken earlier in genomic testing), Hoffman explained.

For elite cattle in the Holstein, Jersey, and Brown Swiss breeds, an enhanced test costs more than $100.

Reliability of the animal's future performance with genomics is at a minimum of 50 percent and approaching 70 percent compared to the 20-25 percent that was common when looking at parentage traits in the past, Hoffman stated.

He said that low percentage was due in part to typical 13-15 percent error rates - even 10 percent at the Marshfield research station herd - in identification of a calf's sire for such reasons as recordkeeping errors or semen straw switches with artificial insemination.



Sire Identification

The genomics process involves the creation of a card, which indicates the expected identity of a calf's parents. The laboratory result (Pfizer's Clarifide program is a major provider) is available 30-40 days after a sample is submitted.

What the report will provide is a definite identity of the sire along with predictions for the calf's ultimate performance based on 30 pairs of chromosomes and more than three billion base pairs of genetic material, Hoffman pointed out.

Armed with that information, dairy operators could make one of several choices, he noted.

Those choices include selling the calf instead of raising it, a decision on what to do at breeding, and recognizing the possibility of such practices as egg flushing and embryo transplants, Hoffman indicated.

He acknowledged that there are ethical considerations, such as telling or not telling a potential buyer about the genomic results on the calf or heifer.

Citing the genetic traits of the existing University of Wisconsin dairy herd, Hoffman said one of the benefits of genomics is how it probes traits other than milk production. He also cautioned that genomics still has a 30 or more percent shortfall in accuracy.



Genetic Upgrades

But culling the bottom 15-25 percent of a herd's heifer calves could double or triple the rate of genetic improvement in that herd, Hoffman observed.

On the ethical and management decision points, he said his role is to provide the information while not knowing what to do or where to go with it.

The academic community is not saying where capitalism will go in making use of genomics, Hoffman stated. How it will be capitalized is a question at the moment, he observed.

One definite benefit of genomics is to prevent the mating of a sire and a dam that are both haplotype carriers, Hoffmann indicated. He explained that such matings often result in failures to conceive, early loss of embryo, or abortion.

Other elements of mating that can be addressed with genomic data are production (net merit, milk, butterfat, protein, cheese yield), inbreeding, and body stature and strength, Hoffman stated.



Calving Ages

In another aspect of dairy heifer management, Hoffman addressed "stringing" - the range age within a dairy herd of heifers when they calve. He said a wide window - in terms of months - is not a sign of good management and is certainly not good for profitability because of the extra costs of feed, labor, and housing.

Hoffman emphasized that genomics, sexed semen, and embryo transfer are not a solution for a strung-out period of calving by heifers. He said this must be addressed mainly with heat detection and related practices.

When evaluating calving age, be wary of looking at averages because they can easily be misleading if, for example, some heifers are calving at 23 months and others not until 32 months of age, Hoffman stated.



Calving Ages

As to why farms have great variances in that calving age, Hoffman said the reasons are speculative. He mentioned the possibility of fear about breeding when a heifer is too light and concerns about calving problems.

What's not in much doubt, Hoffman concluded, is that the number of days on feed controls what the calving weight is likely to be. It is not out of line to shoot for certain weights at calving but what's not acceptable is a great variance in either weight or age at calving, he remarked.

Although Hoffman prefers a heifer raising protocol that would result in calvings concentrated at about 24 months of age for reasons of efficiency, he also noted that there are differences of opinion on whether early or late calvings result in a higher number of lifetime days in milk.

On that point, Hoffman cited a recent unpublished study, which tracked differences in first lactation milk and lifetime days in milk based on the calving age.

The data shows that the top milk production in the first lactation is for calvings at 23-26 months (slightly lower for higher ages and also somewhat less for calvings at 20-22 months).

The data also showed that the older ages (28-30 months) at first calving have less lifetime days in milk, and that the earlier calving heifers have more lifetime days in milk if they are milked three times a day rather than twice.

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