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High rates of milk replacer reduce digestion and growth in post-weaned calves

Kayla Aragona, Wenping Hu and Tana Dennis for Progressive Dairy Published on 23 August 2019

Feeding calves high rates of milk replacer is common practice in many parts of the U.S. High milk replacer feeding rates have resulted in increased pre-weaning average daily gain (ADG). Improved feed efficiency has also been observed, most likely due to the greater digestibility of liquid feed compared to calf starter.

However, calves fed high amounts of milk replacer have reduced intake of calf starter and therefore inadequate or delayed rumen development.

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Proper rumen development is important for calves to have a successful weaning transition. Consumption of dry calf starter containing easily fermentable carbohydrates is needed to establish rumen microbial production of propionate and butyrate, short-chain fatty acids essential for development of the rumen. Calves need to consume a sufficient amount of starter prior to the weaning transition to allow these changes in rumen microbial populations and papillae development necessary for adequate digestion post-weaning.

A trial from Provimi’s Nurture Research Center investigated the effects of feeding four milk replacer rates on digestion after weaning (Table 1).

Digestibility of dry matter and neutral detergent fiber

At 8 weeks old, digestibility of dry matter and neutral detergent fiber (NDF) declined as milk replacer feeding rate increased. At 10 weeks old, digestibility of dry matter and NDF declined as the milk replacer feeding rate increased. These reductions in digestibility extended several weeks post-weaning as a result of previously feeding milk replacer at rates over 1.5 pounds of powder daily, indicating a carryover effect of milk replacer feeding programs.

Another trial from the same research center evaluated the effects of feeding a moderate versus a high rate of milk replacer, with either a low-starch pelleted calf starter or a high-starch textured calf starter on digestion immediately post-weaning (Table 2).

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Digestibility of dry matter and neutral detergent fiber

Digestibility of dry matter and NDF was reduced, regardless of calf starter type, as a result of feeding more milk replacer.

An analysis of 10 studies conducted at the Nurture Research Center evaluated the effects of feeding moderate (1.5 pounds daily or an average of 65 pounds per calf) or high (2.3 pounds daily or an average of 107 pounds per calf) rates of milk replacer on growth and digestion during the pre-weaning and post-weaning phase. Digestibility measurements are shown in Figure 1.

Digestibility of dry mattera and neutral detergent fiber

At 8 weeks old, digestion of dry matter and NDF were lower for calves previously fed high rates of milk replacer. Digestion of dry matter and NDF was also reduced at 11 to 13 weeks old for calves previously fed the high versus moderate rates of milk replacer daily.

In these 10 expert-reviewed studies:

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  • Advantages in ADG for calves fed high rates of milk replacer were either lost or reduced compared to ADG of calves fed moderate milk replacer during the post-weaning phase.

  • Hip width change during the post-weaning phase was greater for calves fed moderate rates of milk replacer compared to those fed high rates of milk replacer pre-weaning.

  • The decreased digestibility of nutrients as a result of high rates of milk replacer largely explains the decreased ADG and hip width gain during the grower phase.

These results, in combination with up to $60 in savings per calf, indicate calves should be raised on moderate rates of milk replacer.  end mark

Wenping Hu, Ph.D., is a ruminant nutritionist for Provimi. Email Wenping Hu

Tana Dennis, Ph.D., is a calf and heifer technical support specialist for Provimi. Email Tana Dennis.

Kayla Aragona
  • Kayla Aragona

  • Calf and Heifer Specialist
  • Provimi
  • Email Kayla Aragona

Take-home points

  1. Rates of milk replacer exceeding 1.5 pounds of powder daily decreases digestion of dry matter and neutral detergent fiber (NDF) after weaning.

  2. During the post-weaning phase, pre-weaning advantages in average daily gain (ADG) for calves fed high rates of milk replacer were either lost or lower than ADG of calves fed 1.5 pounds of milk replacer powder.

  3. In light of today’s dairy economy, calves should be raised on moderate rates of milk replacer (not exceeding 1.5 pounds of powder daily), as it supports optimal digestion and growth to 4 months old.

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