Extended Weaning Influences Digestion Efficiency
How long is the weaning period? Three days, 7 days or 10 days or 14 days?
The authors suggest that when calf starter grain intakes increase rapidly from 100-200g/day to more than 1,000g/day in 5 to 7 days (short weaning period) digestion is compromised. They conclude the digestion rates are low enough to leave the heifers short on energy and protein to maintain preweaning rates of structural growth.
"A recent comparison of weaning over 7 or 14 days to complete weaning by 8 weeks reported greater organic matter digestibility at 12 weeks for calves weaned over 14 days." (Dennis, 2017 abst.)
"It is known that calves fed a large amount of milk replacer will have lower digestibility of starter postweaning than calves fed moderate amounts of milk replacer and this difference in digestion appears to persist for at least 4 week." (Dennis 2017 p9003) [emphasis added]
Evidence is piling up that longer weaning periods for calves fed large amounts (for example, 2 pounds or 1 kg MR, 8 to 10 quarts of whole milk daily) of milk replacer/milk need time once they begin consuming calf stater grain (concentrate) to develop efficient digestive processes in their rumens. Dennis, Hill and others are suggesting 2 weeks rather than 7 days as a more appropriate step down period.
I used 2 week-long weaning period with my own calves (roughly 35-49 days). I did not observe negative trends at the end of milk feeding. I kept them in individual housing for one more week. for close observation. During the first week post-weaning I wanted the weaned calves to be active, bright-eyed and actively eating their calf starter grain and eager to eat the small amount of hay in their grain bucket. Then around 56 to 60 days they moved into group pens (5 per pen).
Dennis suggests a 4 week adaptive period is required to full adaptation of the rumen to a grain-based ration. I did not have that long. I don't know if I should have seen some issues the last week in individual housing and the first 3 weeks my calves were in transition pens. But, I treated very few calves for pneumonia, they spent a lot of time running around in their out-door pens (16' x 32') and ate well over 5 lbs (somewhat more than 2kg) grain daily. Unfortunately, although I had weaning weights I was not collecting any measurements (weight, height) after weaning - that is, in the transition grower phase.
Refernces: Dennis, T.S., and Others, "Effects fo egg yolk inclusion, milk replacer feeding rate, and low-starch (pelleted) or high-starch (texturized) starter on Holstein calf performance through 4 months of age." Journal of Dairy Science 100: 8995-9006. Dennis. T.S. and Others, "Effects of previous milk replacer feeding program on calf performance and digestion through 4 months of age." Journal of Dairy Science 100 [E-suppl 2:301] Abstract. 2017.