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New insights on feeding post-weaned dairy heifers

Tamilee D. Nennich and Tana S. Dennis for Progressive Dairyman Published on 18 January 2016

Nutrition of dairy heifers is often talked about as a whole without referring to the age and growth stage of the heifer. Even though there is a lot of focus placed on feeding milk-fed calves, little research information is available regarding the best strategies for feeding post-weaned dairy heifers.

It is important to keep in mind that calves recently weaned have very different nutrient requirements from year-old and bred heifers, and need to be fed differently.

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Starter intake does help to promote the growth and development of the rumen in calves, but making an assumption that weaned calves are fully functional ruminants is not correct. Therefore, continuing to pay close attention to how post-weaned heifers are fed will allow for the rumen to continue to develop and will maximize the growth and development of these heifers.

As feed costs are the greatest expense for raising dairy heifers, nutritional strategies to encourage growth and development while improving feed efficiency are beneficial for both the animals and heifer raisers.

Paying close attention to the diets of post-weaned heifers helps to make sure they are growing at a rate to ensure they will be ready for breeding and are efficiently utilizing the diets they are fed. Recently conducted research studies continue to show the importance of feeding post-weaned heifers quality, grain-based diets as a way to increase growth and improve feed efficiency.

Feed delivery methods

Dietary composition is an important aspect of feeding heifers, but the delivery method can also have an impact. A study was conducted to evaluate the effects of feeding heifers a TMR, feeding them concentrate and hay side-by-side in a feedbunk (SBS) or feeding grain in a bunk and hay in a feeder (HF) on growth and intake of post-weaned heifers.

Delivering feed using HF resulted in heavier heifers than heifers fed using SBS and TMR, respectively, over the course of the study. Heifer weights at the conclusion of the grower period were 605, 576 and 575 pounds for HF, SBS and TMR, respectively.

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During the grower period, heifers fed using HF averaged 1.1 pounds per day more dry matter intake (DMI) compared with SBS and TMR. However, heifers fed using a TMR consumed more feed daily from day 63 to the conclusion of the study.

The results of this study suggest that, along with responses in average daily gain (ADG), component-fed heifers maintained intake and weight gains when transitioning to a new diet, while TMR-fed heifers caught up in terms of ADG and efficiency toward the end of the transition period and throughout the grower period. This study indicates that there may be a certain point during the growth of a heifer when it is ideal to be able to switch over to feeding a TMR.

Dietary grain and forage levels

In many dairy systems today, calves are fed grain-based starters free-choice within a few days of birth and don’t receive hay until after weaning. The timing as to when calves should begin to receive forage, the type of forage they should receive, and how much of that forage they should be given is still of some debate.

Research conducted at Purdue University looked at different concentrate-to-forage ratios to help determine the best strategy for feeding post-weaned dairy heifers.

Heifers began the study when they were approximately 330 pounds and 4.5 months old and were assigned to diets containing 40, 60 or 80 percent concentrate (on a dry matter basis) for 56 days before abruptly being switched to a common diet that was 40 percent concentrate.

In this study, increasing grain inclusion from 40 to 80 percent of the dietary dry matter resulted in an increase in bodyweight (Table 1).

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weight, skeletal measurements and intake of prepubertal dairy heifers

ADG was improved overall for heifers fed 80 percent concentrate during the treatment period – though following a diet change, ADG was improved for heifers previously fed 40 or 60 percent concentrate compared to heifers fed 80 percent. Frame growth exhibited similar responses to those observed for bodyweight and ADG.

Feed costs per pound of DMI during the study averaged $0.11, $0.12 and $0.13 for heifers fed 40, 60 and 80 percent concentrate during the treatment period. Feed costs per pound of ADG were lowest for heifers fed 60 percent concentrate over the duration of the study, although they were statistically similar to the feed costs for heifers fed 80 percent concentrate.

This study demonstrated that feeding higher grain levels to post-weaned dairy heifers can improve growth and can actually decrease the cost of gain over higher-forage diets.

In addition, it reinforced that heifers fed high grain levels can be negatively impacted by abrupt changes to higher-forage diets, with the heifers on the 80 percent concentrate treatment showing a definite decline in intake when they were switched to a 40 percent concentrate diet that took some time to recover from (data not shown).

Feeding hay or ensiled forages

Forages are an important component of heifer diets. However, little research has looked at how well post-weaned dairy heifers are able to utilize ensiled forages as compared to dry forages. A study was done to evaluate the performance of post-weaned dairy heifers fed either dry hay or baleage.

In this study, heifers fed a diet containing either 40 percent of their dietary dry matter as hay or baleage for a 28-day transition period had improved ADG, and the increase in ADG continued when heifers were fed the dry hay at 60 percent of the dietary dry matter for an additional 56-day grower period (Table 2).

bodyweight, intake and feed efficiency of prepubertal dairy heifers

Interestingly, the DMI of the heifers during the transition period was not decreased; thus, the decreased gain was not a result of lesser intakes. During the grower period, the DMI was decreased for heifers fed baleage, although there was still an overall tendency for improved feed efficiency for heifers fed dry hay.

The results of this study indicate that feeding ensiled forages to post-weaned dairy heifers may result in reduced growth and decreased feed efficiency. In this study, the heifers fed hay were apparently able to better utilize the forage in their diet.

Although measurements of rumen development were not determined in this study, it may be possible that the rumen of the post-weaned heifers was still undergoing development and the ensiled forage was not able to be fully utilized at that point in their development.

Conclusions

Using the best feeding strategies for post-weaned dairy heifers allows heifers to continue to meet their growth potential while reducing costs per pound of gain and reducing the overall costs of raising dairy heifers. Continuing to feed heifers high levels of grain post-weaning provides them with a digestible source of nutrients that facilitates growth and improves feed efficiency.

At young ages, heifers appear to continue to need readily available energy sources as their rumen continues to develop. Realizing that post-weaned heifers are still developing and are not yet ready to be fed like cows facilitates an understanding that specific feeding strategies need to be developed to allow for optimal growth and development of these heifers.  PD

Tamilee Nennich is a dairy nutrition specialist with Famo Feeds, Inc. Email Tamilee Nennich. Tana S. Dennis is a Ph.D. candidate at Purdue University and a calf and heifer nutritionist at Provimi North America.

References omitted due to space but are available upon request. Click here to email an editor.

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