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:
- 20 female Holstein calves were randomly assigned at birth to be weaned at 6 or 8 weeks.
- 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.
- Free-choice starter grain, chopped oat straw, and water were offered to all calves, with intakes of each recorded daily.
- Body weights were measured weekly until 70 days of age.
- Rumen fluid, fecal and blood samples were taken and evaluated before and after weaning on days 35, 49 and 63.
- 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.”