Monday, May 1, 2017

Variation in Growth Rates, Preweaned Calves

The University of Minnesota included 102 heifer calves in a feeding trial. They compared growth and behavior among group-fed calves on an organic dairy. The calves were fed whole milk with Skellerup peach teat feeders either once a day or twice a day for a total of 6 L (6.3 quarts) daily. (13% solids, 4.2% fat, 3.3% protein).

The NRC calf model projects the estimated gain for calves about 81 pounds in a 60F environment with this ration (6.3 quarts daily) at 1.4 pounds per day (protein limited ration, lots of leftover energy with this high fat milk). Calves had a 19% protein calf starter available free-choice.

The variation among calves was evident at 60 days of age:

Holstein calves -                                             low = 0.55kg/day, high = 0.97kg/day [1.2 - 2.1 lbs/day]
HolsteinXMontbeliardeXViking Red -          low = 0.4 kg/day, high = 1.07kg/day [0.9 - 2.4 lbs/day]
HolsteinXJerseyXNormandeXViking Red - low = 0.5kg/day, high = 0.98kg/day [1.1 - 2.2 lbs/day]

The once-a-day calves achieved 85 percent doubling their weight by 60 days. The twice-a-day fed calves achieve 96 percent doubling their weight by 60 days.

When I used a sample of Holstein calves for which I had individual growth rates to compare rate of gain by sire I found that about one-third of the variation could be tied to the sire.

The messages for me are:

1. Expect lots of variation in gain among calves that receive the same care under the same farm conditions. There will be "laggards" (low growth rate) among every group of calves.

2. Given variation the most effective way to get better gains from the "laggards"is to raise the level of nutrition for the entire population.

Reference: Kienitz, M.J., and Others, "Growth, behavior, and economics of group-fed calves fed once or twice daily in an organic production system." Journal of Dairy Science 100:3318-3325. March 2017 

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