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Managing the weaning transition of growing heifers

Tana Dennis and Xavier Suarez Published on 24 November 2015

Successful heifer-rearing programs are often only judged by high growth rates to weaning and average ages at first calving. However, heifer management during weaning, transition and immediately post-weaning is often overlooked.

Consideration of drastic changes in rumen function and digestive development during this time is crucial to a successful weaning transition to avoid post-weaning “slumps” in growth and efficiency.

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Evaluation of the liquid feeding program is key to planning for a successful weaning transition. There are several schools of thought regarding milk feeding programs. With each one, the goal is to develop healthy replacement heifers that reach their genetic potential for milk production in a cost-effective manner.

However, some programs place a heavy emphasis on growth performance to 56 days old, which is typically the time at which milk is removed from a calf’s diet.

These programs encourage aggressive feeding rates in excess of 2 pounds of solids per calf per day, which has been shown to reduce calf starter consumption when compared to calves fed less aggressive liquid programs. Calves are generally weaned when starter consumption reaches 2 pounds per day for two or three consecutive days.

In a conventional liquid feeding program where 1 pound of solids is fed per calf daily, by the time calves consume 2 pounds of starter per day, they have already consumed a significant accumulated amount of starter.

In conventional programs, calves consume approximately 60 pounds of starter in their first six weeks of life, and over the next two weeks, they typically consume another 50 pounds, totaling approximately 110 pounds of starter in their first 56 days of life.

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In aggressive liquid programs, calves don’t consume much starter until the weaning transition begins, but once it does, starter consumption increases quickly. Calves can be eating 2 pounds per day in just a few days, but the accumulated consumption would be too low.

For example, in several published trials, calves on aggressive milk replacer programs will consume 30 to 40 pounds of starter in their first six weeks of life but still consume approximately 50 pounds over the next two weeks, like calves fed conventional programs.

Because starter intake is so low in their first six weeks of life, the digestive capacity in aggressively fed calves may not be developed enough to efficiently utilize dry feeds when using this criteria.

When compared to traditional and moderate milk replacer feeding programs, digestibility of total dietary dry matter at 56 days old has been shown to decline about 12.5 percent for calves fed an aggressive milk replacer program (Table 1).

milk replacer feeding programs

Click here or on the image above to open it at full size in a new window. (PDF, 716KB)

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This reduction in diet digestibility immediately post-weaning may partially explain the post-weaning “slump” often seen with aggressive liquid feeding programs.

Rumen capacity may be restricted due to less dry feed consumption in aggressively fed calves, which would limit retention time in the rumen and increase passage rate, thereby reducing starter digestibility.

Based on the research with conventional, moderate and aggressive milk-feeding programs, a more appropriate metric would be to have calves consuming at least 100 pounds of starter from birth to 56 days old to ensure a successful weaning transition.

However, it is difficult for the producer to measure total starter intake from birth to 56 days old. Researchers are currently working on tools that will assist the producer to assess starter intake with aggressive milk feeding programs.

As generally practiced with the transition period of a cow, gradual steps should be employed with the weaning transition for the calf. Once milk or milk replacer is removed from the diet, calves should remain in individual or group housing for seven to 14 days to monitor health and starter intake before moving to larger groups.

Once calves are moved into larger post-weaning groups (eight to 10 per group is recommended), continue to provide a texturized, high-starch grower feed with chopped hay until 4 to 6 months old. Target growth rates post-weaning should be 2 to 2.2 pounds per day of average daily gain in order for heifers to attain at least 300 pounds of bodyweight by 4 months old.

It has been common practice to restrict grain intake to approximately 6 to 8 pounds per day with free-choice access to hay. However, this restricts intake of more digestible grains in favor of less digestible forages, which can limit growth potential of heifers following weaning.

It is also essential that forage particle length is reduced for growing calves, as the rumen is still growing in size, and digestive capacity and longer particle lengths can limit feed intake.

Quality and digestibility of hay provided should be moderately high, ranging from 15 to 16 percent crude protein and less than 60 percent neutral detergent fiber on an as-fed basis. Another strategy is to offer a mix of chopped forage and calf grower free-choice.

Chopped forage should be 5 to 10 percent of the diet depending on its quality (5 percent when using straw and 10 percent when using grass hay). Alfalfa hay should be avoided as stems can often be unpalatable and easily sorted out, resulting in wasted forage and an unbalanced diet.

Forage proportion should be increased after 4 months old to prevent overconditioning. From 300 pounds to puberty, average daily gain should be targeted to 1.8 pounds to ensure reaching 55 percent of mature bodyweight at breeding and prevent fat deposition in the mammary gland.

Once heifers reach 6 months old, feeding a TMR using fermented forages would be appropriate for the remainder of the rearing period.

While growth in bodyweight and frame to weaning can be indicative of a successful milk feeding program, factoring performance during the weaning transition and growth from birth to 4 months old may give a better indication of the overall success of a heifer-rearing program.  PD

Tana Dennis and Xavier Suarez are calf and heifer nutritionists for Provimi North America. Dennis works primarily in Pennsylvania, New York and New England. She can be contacted by email. Suarez primarily works in Wisconsin, Minnesota and eastern South Dakota. He can also be contacted by email.

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