Accelerated Feeding Programs

For Heifer Calves.

What are the Potential Benefits of Accelerated Feeding Programs for Dairy Replacement Heifer Calves?

Summary:

The way dairy replacement heifers are raised has a major impact on their future milk production and health.
New research has found that calves fed twice as much whole milk or CMR than conventional feeding rates had improved growth rates and feed efficiency with consequent improvements in fertility and first-lactation milk yields averaging 450 – 900kg milk and subsequent lactations.
Calves fed higher rates of milk or CMR had a higher resistance to pre-weaning diseases.

Introduction:

Conventional calf-rearing systems historically have restricted the amount of milk or milk replacer fed during the first few weeks of life in an effort to encourage solid feed intake and to speed up the development of the rumen in preparation for transitioning to pasture at an early age to keep the costs of rearing as low as possible.

Little thought has been given to the possibility that early feeding practices could influence subsequent productivity when these calves grow into lactating cows.

Accelerated milk feeding involves feeding up to twice as much milk or CMR during the pre-weaning phase of a young calf with growth rates similar to suckled calves with consumption of 2.5 – 3.5% of body weight as milk dry matter while offering a starter meal or pellet until satisfactorily transitioning to a grass only diet.

Although many people have long recognized that a strong correlation exists between calf nutrition and rates of disease, we have only recently had data to illustrate the importance of this relationship. With the plethora of new data published in the last 5 to 10 years it has been hard to avoid the realization that we have been significantly underfeeding dairy heifers for a long time and that more biologically relevant planes of nutrition provide multiple benefits.

To accomplish this goal, several new technologies have gained popularity, including novel milk replacers, automated calf feeding systems, and the acidification of milk fed ad libitum. In addition, many farmers have simply chosen to increase the volume of milk or milk replacer they feed to their calves. All of these have largely been introduced to assist dairy producers that wish to feed for higher preweaning growth rates.

New research:

Over the last several years, demonstrations of the remarkable improvements in growth and feed efficiency that are obtained by feeding greater quantities of milk or milk replacer have stimulated renewed interest in early calf nutrition.

One of the most exciting current areas of research concerning accelerated feeding has documented long-term effects of early nutrition on subsequent productivity.

Cell division and growth. The nutrient supply regulates the cell division rate in the early growth phase, so that organ development and thus the performance of the dairy cow in later life is “programmed” via the intensity of feeding. This effect is called metabolic programming.

Calves that are reared with a limited nutrient supply may reach the desired size at a later stage due to compensatory growth, but this does not have a positive effect on subsequent performance. This is due to the fact that this subsequent growth takes place in the subsequent cell growth phase and not during the primary cell division phase. The compensatory growth therefore helps to correct the body weight, but has no impact on the organ systems, the development of which is primarily influenced in the first weeks of life.

As more and more lactation data become available for calves fed differently after birth, it is becoming clear that improved growth rates and early nutrition translate into greater milk production.

How can a higher milk yield be explained as a result of intensive calf feeding? During the first 50 days of life, intensive self-multiplication of cells takes place in the inner organs, whereas in the later rearing phase, growth takes place through cell enlargement.

*Organ mass in g/kg liveweight, (Geiger et. al., 2016)*

Positive maturation of organs in calves. The results of an American study at the University of Blacksburg illustrate the effects of metabolic programming.

Content of the study:
Two trial groups were fed either restrictively or intensively over a period of 8 weeks.

Result:
The intensively fed calves were, by the 8th week of life, 24.5 kg heavier than the restrictively fed animals.
A comparison of selected organs showed a significantly higher organ mass per live weight kg in the intensively fed calves.

Conclusion:
This means that certain organs generate a higher cell growth in relation to the whole body during an intensive nutrient supply.

Mammary gland development: Other studies show that the mammary gland of the heifer in the period from 3 to 9 months of age is faster than that of the rest of the body and that feeding higher rates of milk pre-weaning result in:

A significantly greater mass of mammary gland parenchyma in calves fed a higher plane of nutrition, pre-weaning.
Mammary fat pad development is also significantly greater.
Overall mammary gland development of dairy heifer calves is positively affected by providing a higher pre-weaning feeding plane.

*Udder and mammary gland tissue in g (Soberon and Van Amburgh 2017)*

Soberon and Van Amburgh (2017) were able to prove the effect of metabolic programming on the development of udder tissue.

Content of the study: Feeding trial with two trial groups, one of which was fed restrictively with 0.6 kg milk replacer powder/day and the other fed intensively with 1.3 kg milk replacer powder/day.

Result: The results of the histological examination clearly show that on the 54th day of life, in comparison to the restrictively fed animals, the intensively fed animals exhibited udder and mammary gland tissue that was significantly larger.

Higher milk yield through ad libitum calf feeding? Numerous scientific studies have confirmed the importance of intensive rearing and the associated higher profitability in dairy cattle farming. It essentially comes down to a change in attitudes in practice. Investments in a new-born calf, especially in the first weeks of life, are always worthwhile.
The table shows the link between the higher daily gains during the first 35 day feed phase and the higher milk yield in the 1st lactation.

Other studies have also shown that pre-weaning average daily gain is positively correlated with first lactation milk yield. For example, one study showed that for every 1kg increase in preweaning average daily gain, heifers produced 850 kg more milk in their first lactation and 235 kg more milk for every 1 Mcal of ME intake above maintenance.

These findings are supported by a meta-analysis that reported an average improvement in first-lactation milk yield are in the range of 450kg to 900kg of milk.

Data also indicate that calves fed at a higher plane of nutrition are more resistant to disease than calves on more conventional milk feeding programs. In another study, calves fed an accelerated milk feeding program designed for more preweaning growth (28% protein, 20% fat) maintained hydration, had faster resolution of diarrhoea, had increased BW gain, and showed better feed conversion after experimental challenge with Cryptosporidium parvum than calves fed conventional milk replacer (20% protein, 20% fat).

The available evidence suggests that improvements in health are due to improved overall nutritional status rather than to any specific alterations in immune system characteristics or function.

So, what is accelerated milk feeding?

Traditionally, calves have been fed limited amounts of milk or milk replacer (typically 8 to 10% of birth BW) which allows for maintenance requirements only and up to about 0.25 kg/d ADG with starter offered for ad libitum consumption from the first week of life.

This amount of liquid feed is much lower than ad libitum intakes, which are in the range of 16 to 20% of BW or 2 to 2.5% of BW as dry solids. As starter intake increases, typically doubling every week, enough nutrients are consumed to allow calves to begin to grow rapidly. To supply sufficient nutrients for growth NZ has some of the most complex meals in the world, which in itself has a cost but is necessary to make up for deficiencies in milk feeding.

The restricted liquid feeding approach arose in an attempt to stimulate early intake of starter and to minimize input costs of higher-value feed. In addition, early milk replacers were of poor quality and were not well utilized by calves at higher feeding rates.

A contrasting approach is the accelerated feeding system, which allows calves much greater intakes of liquid feed during early life, closer to “natural” conditions in which calves would have ad libitum access to milk. Milk feeding rates are approximately twice those of conventional systems.

An easy rule of thumb is to provide 1.5% of BW as milk solids during the first week of life, then 2% of BW from the second week of life until the week before weaning, when a step-down or gradual weaning program over a three week period is adopted.

Intake of starter meal/pellets lags calves fed on conventional systems but increases at approximately the same rate once the amount of liquid is cut back. To avoid or minimize growth slumps around weaning, calves are not weaned until they are consistently eating 1kg of starter meal/pellets daily.

As shown below, the major difference in growth rate is in the first 2 to 3 weeks of life, and after that, growth rates generally are parallel. Accelerated feeding programs using whole milk can also be successful.

Figure 1. Example of differences in early growth between calves fed on a conventional limit-feeding program (milk replacer powder fed at 1.25% of birth BW; calves weaned at 35 days) or on an accelerated (intensified) program where milk replacer was fed at 2% of birth BW for wk 1, then 2.5% of BW at wk 2 during wk 2-5. Calves had access to water and starter from wk 1 of life and were weaned at d 42.

Note: It is important that calves must have adequate early colostrum intake to be able to efficiently use additional nutrients from milk intake. In addition, calves undergoing adaptation to stressors such as transport also may be less able to utilize high amounts of milk solids intake in early life.

Factors:

Whole milk contains about 5.37 Mcal ME/kg of solids (18% fat on a DM basis), which means that a 45-kg calf requires about 325 g of milk solids, or 2.6 kg of whole milk (about 2.5 L) just for maintenance. Because most milk replacers are lower in fat content than whole milk, they have less ME per unit of solids (4.6 to 4.7 Mcal/kg). Consequently, a 45-kg calf requires about 380 g of milk replacer (about 3.0 L as fed) for maintenance. Amounts of milk solids consumed above maintenance is used for growth.

The amount of crude protein (CP) required in the calf’s diet as a percentage of dry matter (DM) is very low for maintenance but increases as rate of gain increases. CP content of the diet appears to approach a plateau at about 28% of the DM, which is not unlike the CP content of whole milk solids (about 26% on a DM basis).

To make this program successful the milk replacer must have a higher protein content. Traditional milk replacers usually only contain about 20% protein, while accelerated replacers have 26-28% protein to match whole milk. Feeding more of a conventional milk replacer will not provide the proper amount of protein and energy to the calf.

With an increase of protein in the diet, there is an increase of lean tissue development. The higher protein content is necessary in meeting the nutritional needs of the growing animal. This is what makes the calves grow at a more rapid rate.

These relationships highlight the importance of matching dietary protein and energy intakes with the expected growth performance of the calf. For example, feeding twice as much of a conventional milk replacer with 20% CP does not provide enough protein for lean tissue growth, and the surplus energy will be converted to fat.

Conversely, feeding a high-protein milk replacer (e.g., 28% CP) designed for “accelerated growth” at conventional feeding rates of 454 to 568 g/d provides excess protein to the calves, which cannot be used for additional growth because energy is limiting. In this case, the excess protein will be degraded and the nitrogen excreted in urine.

It is also important to make sure the fat content is not too high, or the calves won’t efficiently gain lean body tissue or muscle. Generally, the fat content should not exceed 20%. The diet should also be more concentrated. Traditional milk replacers usually have less than 14% solids, and accelerated calves should be fed about 16 to 20% solids.

Care needs to be taken to ensure that the osmolality of concentrated milk replacer does not exceed 650 mOsm/L which could potentially slow abomasal emptying and facilitate bacterial fermentation in the abomasum (abomasal bloat). (Raw bovine milk typically has an osmolality of approximately 275 to 285 mOsm/L). Although exact recommendations for total solids are difficult to find in the published literature, in general abomasal bloat problems are often seen with total solid well above 15% (osmolality values over 650 mOsm/L).

Several feeding strategies can minimize the effect of more concentrated milk or milk replacer products on gastrointestinal health. For example, regularly estimating the nutrient density of milk by checking the percentage of total solids as it is being fed to calves helps prevent osmolality from getting extremely high and helps diagnose milk replacer mixing problems.

Brix refractometers can be used and have been shown to provide a rapid and fairly accurate method for estimating milk total solids.

Another strategy is to feed smaller volumes of milk more frequently. As farms feed large volumes (4 L or more) of concentrated milk or milk replacer meals in a single feeding, this exacerbates the negative effect on abomasal emptying. Feeding smaller volumes (2–3 L) multiple times per day has helped minimize the occurrence of bloat in some herds.

This approach is often made more practical by the use of automated calf feeding systems. Maintaining regular feeding schedules and making sure milk or milk replacer is warm also anecdotally appear to help reduce the incidence of abomasal bloat, although the exact effect on abomasal emptying is unclear.

The mixing of this replacer is especially important, and trained staff should do this job very carefully. It is also important to keep the amount of solids in this mixture consistent.

Intermediate feeding:

Feeding programs have been developed that are intermediate in nature to accelerated and conventional programs. These moderately aggressive programs call for liquid intakes between those in conventional and accelerated programs. These programs are reported to result in less slump in growth around weaning and fewer digestive upsets in calves than more aggressive liquid feeding programs while still providing improved nutritional status during the critical first 2 to 3 weeks.

Milk replacers designed for use in intermediate programs usually contain 24 to 26% CP and are fed at 1.5 to 1.75% of BW. While easier to implement, they do not fully capitalize on the early growth potential. These programs may be more easily implemented with transported or colostrum-deprived calves than are more aggressive accelerated programs.

Fortified milk feeding:

Fortified milk is the addition of calf milk replacer to whole milk. This provides a high energy, high protein feed in a smaller volume than would otherwise be required to achieve a similar nutritional content if using whole milk or calf milk replacer alone.

High protein and energy allows optimal growth rates to be achieved without the need to feed high volumes of milk and can help overcome the challenges associated with high volume feeding programs which rely on feeding 20-25% body weight in milk volume daily.

Whole milk is about 12.7% dry matter which is made up of protein, fat, lactose and minerals. In comparison, fortified milk can be fed at 14-19% dry matter, containing more energy and protein than an equivalent volume of whole milk alone.

Careful consideration of the frequency of feeding, the calf milk replacer used and the mix rate at which it is added to whole milk as the consumption of large volumes of fortified milk in a single feed can result in diarrhoea and/or abomasal bloat.

The protein and fat concentration of the milk replacer contribute to the overall total solids concentration of the fortified milk feed and differences in these will result in a difference in overall total solids for the same mix rate. For example, 75g of a 20:20 (20% protein, 20% fat) milk replacer added to 1L of whole milk (estimated total solids of 12.7%) will result in overall total solids of 18.8%. However, if the same mix rate is used with a 28:22 (28% protein, 22% fat) milk replacer, the overall total solids will be 19.6%.

Whole milk from Jersey cows tends to be higher in total solids and this needs to also be considered before starting a fortified milk feed programme.

What are the downsides to

accelerated milk feeding programs?

Cost is obviously the biggest issue. Even if a farmer can benefit in the future, costs to raise accelerated calves increase, and it may not be easy for the farmer to make the transition.
It is important to understand that calves will be consuming a considerable amount of milk, and the amount of calf starter intake will be significantly less. In other words, more money will be spent on milk or milk replacer. But it is also known that calves can increase calf starter intake rapidly once milk or milk replacer intake is reduced. Also, a calf starter with a slightly higher protein content is recommended. This will most likely be more expensive than traditional calf starter.
Another disadvantage regards the digestive health of the calf. When a calf is on an accelerated feeding program, they will sometimes appear unhealthy and will have an abnormal manure consistency. Due to a more liquid based diet, calf faeces may appear to be loose. This is normal. It is incredibly important to have a knowledgeable staff that realizes that this change is expected.
The intake of starter is necessary in stimulating rumen development. Weaning is probably the most crucial part of this program. If not weaned properly, problems can occur with rumen development and post weaning growth reduces to match conventional feeding. Because the heifer is consuming a high amount of protein and solids in the milk or replacer, feed intake of calf starter is dramatically decreased. Because of this decrease, the rumen of accelerated dairy calves is not as developed as it should be when it is time to wean. This is what makes this process crucial at this stage. Calves should be eating 1kg starter per day consistently before weaning off milk.

Considerations:

Farmers considering this method must understand the costs pay themselves off over time with proper management. With a proper accelerated milk feeding program and feeding to potential post weaning, farmers will be able to maintain a healthy group of heifers, breed heifers earlier, obtain more milk from each lactation, and potentially increase their overall profit.

Accelerated feeding programs are not for every farmer and should not be attempted if the farm does not have a strong overall replacement heifer feeding program.

References: https://ruminants.lifestartscience.com/calf-to-heifer/higher-pre-weaning-feed-intake-improves-mammary-gland-development. https://dairy-cattle.extension.org/feeding-pre-weaned-calves-for-future-production. The Potential Benefits of Accelerated Feeding Programs for Dairy Calves. University of Kentucky. College of Agriculture. Accelerated Calf Feeding Yields More Milk During First Lactation. Ryan Leiterman. http://www.crystalcreeknatural.com. Fortified milk lifts calf growth rates – Oz study. Gemma Chuck The Vet Group in Victoria. Australia. Comparison of accelerated calf rearing programs. Lesley Irvine, Mark Freeman & Thomas Snare. Tasmanian Institute of Agriculture.

Ad-libitum-feeding-in-calves-as-much-as-the-calf-wants. https://www.josera-agriculture.com/

Download the Accelerated Feeding Programs for Heifer Calves PDF.