The Case for Later Weaning

A recent study shows calves fed a high-volume milk ration for 8 weeks versus 6 showed better weight gain; higher starter grain and water intake before and after weaning; and exhibited fewer stress behaviors after weaning. ( Maureen Hanson )

Dairy calf weaning age is a topic of considerable ongoing debate. University of Guelph veterinary researcher Michael Steele weighed in on the subject during a presentation at the recent Dairy Calf and Heifer Association annual conference.

Steele, whose primary research focus is calf nutrition and digestive function, recommends a weaning age of at least 8 weeks. “Six-week-old calves just can’t consume enough calories to optimize the milk-feeding stage and prepare digestively for the transition to a ration of solely dry feed,” he said.

He cited a 2015 Ontario study (Eckert et al.) in which he assisted fellow researchers in comparing a 6-week milk-feeding phase to an 8-week feeding regimen. In the study:

  1. 20 female Holstein calves were randomly assigned at birth to be weaned at 6 or 8 weeks.
  2. Milk replacer was offered at 1.2 kg. (2.64 lb.) solids per calf per day in two meals until a 1-week step-down, when meals were reduced by half for a week before weaning.
  3. Free-choice starter grain, chopped oat straw, and water were offered to all calves, with intakes of each recorded daily.
  4. Body weights were measured weekly until 70 days of age.
  5. Rumen fluid, fecal and blood samples were taken and evaluated before and after weaning on days 35, 49 and 63. 
  6. Behavioral factors to assess weaning stress were observed for 1 hour, three times per week, before the second feeding of the day during the period from 2 weeks before weaning until 2 weeks after.

The researchers observed significant differences between the two groups, including:

  • Average daily gain (ADG) for the 8-week weaning group was 1.74 pounds for the week before weaning, compared to .75 pounds for the 6-week weaning group.
  • ADG for the 8-week group in the week after weaning was 2.31, versus .77 for the 6-week group.
  • The calves weaned at 8 weeks were nearly 20 pounds per head heavier at Day 70 compared to those weaned at 6 weeks.
  • From 5 to 8 weeks of age, starter and water intakes were lower for the 8-week weaning group. However, starter intake was higher in the 1 week before and after weaning for the 8-week group, and both groups were at nearly equal starter intake in the last week of the experiment.
  • In the week before weaning (the step-down phase), calves in the 6-week group spent 75% more time sucking various surfaces; 55% less time ruminating; and 36% less time lying down, than the 8-week group.

“These results are fairly significant, especially when you look at the weight gain between the two groups in the week after weaning,” Steele noted. “For calves fed a higher plane of nutrition, extending weaning from 6 to 8 weeks improves productivity, and equips calves to transition more effectively post-weaning.”

 
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