Accelerated calf growth programs involve feeding calves large amounts of milk replacer (2-2.5 pounds/day (0.91-1.14 kg/day)) with higher protein concentrations (30% rather than 20%). Growth rates 3-5 times greater than that of traditional programs have been seen.
It is important that calves on the accelerated growth milk replacer feeding strategy do not have a slump in growth after weaning due to inadequate rumen development. Calves should be weaned only after they consume 2 pounds (0.91 kg) of calf starter for two consecutive days.
Possible benefits of accelerated calf growth include, increased long-term growth rate, improved responsiveness to hormones, improved milk production, immune system enhancement, and improved efficiency of gain. More research is needed in these areas.
Possible disadvantages of accelerated calf growth include, extra cost, more scours and health problems. Mammary development should not be inhibited.
Cornell University researchers and Milk Specialties Company (Dundee, IL, USA) have recently proposed feeding calves larger amounts of milk replacer (2-2.5 pounds/day (0.91-1.14 kg)) with higher protein concentrations (30%). This is opposed to traditional programs of 1 pound/day (0.45 kg) of 20% protein milk replacer. With this milk replacer program, growth rates 3-5 times greater than that of traditional programs have been seen. Typically, calves will gain 2 pounds/day (0.91 kg) by 2 weeks of age using the accelerated calf growth strategy.
The following is an example of a milk replacer program for accelerated growth. Milk replacer is mixed to contain 18% solids (rather than the traditional 12% solids). Calves are fed three times per day, 2-3 quarts (1.89-2.84 l)/feeding from Day 4 to Day 21 and 3-6 quarts (2.84-5.68 l)/feeding after Day 21. Milk replacer intake is reduced by 25% for the last 7-10 days prior to weaning. Calves are weaned at 28-35 days of age after they have consumed 2 pounds (0.91 kg)/day of calf starter for two consecutive days.
Since a pre-weaned calf puts down more protein per unit of gain than a weaned calf , feed efficiency is highest at this time. Increasing growth rate at this age may have long-term productivity benefits according to some experts. Cornell researchers believe nutritional requirements for the pre-weaned calf, especially protein requirements, may be underestimated by current requirement equations. However, calf raisers must recognize that changes in calf management practices are required to provide these extra nutrients in a healthy manner.
University Research Trials
In the first study conducted at Cornell, fifty-four Holstein bull calves were split up at five days of age among three treatments.
Treatments were designed to produce average daily gains of
A) 1.1 pounds/day (0.5 kg/day),
B) 2.1 pounds/day (0.95 kg/day), or
C) 3.1 pounds/day (1.4 kg/day).
An all-milk milk replacer containing 30% crude protein and 20% fat was fed at 15% DM in the first two diets and at 18% DM in the third diet. Milk replacer intake was targeted at 1.5%, 3.0%, and 4.0% of body weight for each treatment group, respectively. But, target intakes were not achieved for the third group (Treatment C ) until they weighed between 143 and 187 pounds (65-85 kg). The goal for all three treatment groups was to make sure that protein was not limiting growth. Calves were fed three times each day. Free-choice water was available but no grain was offered. A few calves from each treatment were slaughtered at 143, 187, or 232 pounds (65, 85, or 105 kg) body weight.
Significant differences (p<0.05) in DMI, Gain/Feed, and ADG were observed (see table). Young calves had difficulty drinking the milk replacer at 18% DM and it was concluded that 15% DM was more acceptable. Few health problems and scours were observed. The researchers attributed this to good management and to milk replacer manufacturing techniques. It was concluded that protein requirements are driven by energy intake of calves. To meet requirements of calves gaining more than 1.5 lbs/day (0.68 kg/day), it was suggested that a milk replacer containing 26-28% CP is needed.
Intake and ADG of Accelerated Growth Calves
|Target Growth Rate
|Daily DMI, lb
Van Amburgh et al., 2001
Intake and ADG of Accelerated Growth Calves, metric measurements
|Target Growth Rate
|Daily DMI, kg
Van Amburgh et al., 2001
The Cornell researchers, as well as Illinois researchers, were able to obtain high growth rates in the calves without excessive fattening. Growth in stature and lean mass were increased because of the high levels of protein and moderate levels of fat in the milk replacers.
In a further study by the Cornell group, it was found that high growth rates (1.5 pounds/day (0.68 kg/day)) could be maintained on both high fat (31%)/low lactose (35%) and low fat (15%)/high lactose (55%) diets formulated to contain the same amount of energy and protein. But, the low fat/high carbohydrate diets produced a leaner animal.
The high lactose diet did not result in increased scouring problems in this study.
In another Cornell study, it was shown that calves fed a 30% CP, 20% fat milk replacer at 2.4% BW as DM per day showed a greater response to an injection of bovine somatotropin (bST) at 5 weeks of age compared to calves fed a 20% CP, 20% fat milk replacer at 1.4% BW as DM per day. This could mean that conventional feeding strategies do not allow calves to show their full growth potential.
“Accelerated” vs. “Natural” vs. “Traditional” Milk Replacer Feeding Strategies
It must be recognized that traditional milk replacers mixed and fed in the typical way (8 oz. (227 grams) of a 20% protein milk replacer in 2 quarts of water twice per day) do not contain the same amount of nutrients as whole milk programs (2 quarts twice per day). Whole milk on a DM Basis contains 25-26% protein and 29-30% fat. Traditional milk replacers contain 18-22% protein and 15-22% fat on a DM Basis. So, some improvement in milk replacer nutrient content may be needed just to catch up with calves consuming whole milk. It should also be noted that studies of suckling calves documented calves consuming 6-10 meals each day and 2.5-3.5% of their bodyweight as milk dry matter. These suckling calves often attain high growth rates similar to the “accelerated” protocol. So, one may consider the “accelerated” protocol more similar to the naturally designed protocol.
Development of the Rumen to Ensure Growth Post-Weaning
Part of the reason only one pound (0.45 kg) of milk replacer has been recommended in the past is to encourage early intake of grain. There are two reasons for stimulating grain intake. First, it is usually economically advantageous to switch calves from milk replacer to calf starter as soon as possible. Second, the fermentation of carbohydrates in calf starter stimulates the growth of the rumen papillae that absorb energy from the rumen. An adequately developed rumen is important for providing the calf with energy and protein from calf starter once milk or milk replacer is no longer fed. It is clear that a higher rate of milk or milk replacer feeding will decrease calf starter intake. But, it is also known that calves can increase calf starter intake rapidly once milk or milk replacer intake is reduced.
Because it is important that calves on the accelerated growth milk replacer feeding strategy do not have a slump in growth after weaning, another study was conducted at Cornell. Calves were fed a 30% CP, 20% fat milk replacer two times per day at 2% of BW. A 26.5% CP starter was fed beginning when calves reached 220 pounds (100 kg) of body weight (at 8-9 weeks of age). At this time milk replacer was fed at 1% BW per day for one week and then 0.5% BW per day for another week and then stopped. Calves gained 0.95 pounds/day (0.43 kg) during the first week of weaning. Three weeks after the start of weaning, daily gains returned to about 2.5 pounds (1.14 kg) per day. Both heifers and bulls were used in this study and responses were similar regardless of sex. It was concluded that this weaning protocol could be used for calves on the accelerated growth milk replacer feeding strategy to avoid post-weaning growth slumps.
Older research with higher rates of milk or milk replacer feeding often had problems with post-weaning growth slumps. But, it must be recognized that these studies typically used milk replacers containing less protein resulting in less stature growth. Also, less nutrient-dense calf starters were typically fed.
Possible Benefits of Accelerated Calf Growth
Because of the limited number of days that calves are on the accelerated milk replacer program, one cannot significantly reduce age at first calving just by increasing calf growth rate. There may be long-term advantages to increasing lean body mass at this time. The following benefits may exist.
Increased growth rate early in life may increase long-term bone growth, decreasing time needed to achieve adequate breeding size. There is one Israeli study showing production improvements in the first lactation from an accelerated calf program. In this study, calves consumed more nutrients by suckling their mothers. There is also data from other species showing that better nutrition early in life may enhance responsiveness to hormones. Studies are needed to compare productivity of calves raised on traditional programs versus calves raised on accelerated programs.
Health of calves fed according to the accelerated program has been a concern of some nutritionists. This is because calves are generally healthier after weaning when they are consuming no milk. The rumen can reduce the negative effect of toxins. Fiber bulk benefits the intestine, reducing scours. Energy consumption generally increases after weaning.
On the other hand, there is some evidence that better nutrition early in life can help the immune system. Growth hormone and insulin-like growth factors (IGF-I) have a beneficial impact the immune system and better nutrition increases their levels in the body. Controlled research is needed in this area. But, some commercial heifer raisers do think that they have seen better immune responses in calves on accelerated growth programs.
3. Efficiency of Gain
Because the nutrient cost associated with maintaining the body is diluted, efficiency of gain generally increases when growth rate increases. In the Cornell study (see table), feed efficiency increased from 0.57 to 0.75 as rate of gain increased from 1.26 to 2.43 pounds/day (0.57-1.10 kg/day). It has also been shown that efficiency of protein usage decreases with age. So, it is beneficial to maximize protein consumption and lean growth at a young age.
Possible Disadvantages of Accelerated Calf Growth
Depending on weaning strategy, accelerated calf growth can cost significantly more. Cost per unit of milk replacer increases and more milk replacer must be fed each day. Furthermore, excellent growth through the weaning period will depend on an excellent (and costly) calf starter. Of course, if weaning age is reduced, the total calf raising cost may not be affected as much. More research needs to be conducted to determine if there are long-term benefits of accelerated calf growth that justify the costs.
2. More Scours and Health Problems
Many people comment that feeding more milk or milk replacer results in more scours. Grain and fiber do add bulk to the intestine and stiffen manure but the research shows that more milk or milk replacer does not result in more scours. Poor ingredient quality and manufacturing can result in more scouring. Poor environmental conditions will also reduce growth of calves on an accelerated milk replacer protocol.
3. Inhibition of Mammary Development
People are familiar with the research indicating that rapid growth can impair mammary development and reduce lifetime production. First, it must be recognized that those studies fed too much energy. They grew fat heifers instead of lean heifers. Second, it has been shown that growth rate prior to two months of age does not affect mammary development. So, fast growth of lean tissue in calves is not expected to negatively affect lifetime production.
Alternatives for Accelerated Calf Growth
Despite the one Cornell study, many nutritionists and producers still have concerns regarding rumen development in calves fed increased amounts of milk replacer. Longer term research studies are required to determine whether aggressive feeding of a high quality calf starter will result in heifers equivalent in size to those fed on an accelerated replacer program when animals are followed out to older ages.
One pound (0.45 kg) of a 20% protein/20% fat milk replacer should maintain a calf plus provide enough nutrients for the calf to gain about 0.55 pounds (0.25 kg) each day. With this program, calves should have a strong drive to eat calf starter in order to meet their energy needs for growth. Calves provided with fresh, high-quality calf starter and fresh water should increase intake rapidly and be ready to be weaned at 4 weeks of age after they have consumed 2 pounds (0.91 kg) of calf starter for two consecutive days. Often these calf starter and water needs are neglected on commercial dairy farms. So, one alternative rather than increasing milk replacer, would be to improve calf starter and water management to stimulate growth and reduce weaning age. It is important to understand that if calves are weaned before they are ready, they can be stressed, suffer from acidosis, lose weight, and possibly die. Improper weaning management can, therefore, eliminate any gains in calf growth made through either improved starter or milk replacer feeding regimes.
Phase feeding is another alternative to feeding very high levels of high protein milk replacer. With phase feeding, the amount of milk replacer fed is gradually increased up until Week 4 to provide extra nutrients for growth. For example, milk replacer could increase from 1 pound/day (0.45 kg) during Week 1 up to 1.75 pounds/day (0.80 kg) during Week 4. Then, after Week 4, milk replacer is gradually reduced to encourage calf starter intake and rumen development.
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Diaz, M.C., J.M. Smith, and M.E. Van Amburgh. 1998. Nutrient requirements and management of the milk fed calf. In: Proceedings of the Cornell Nutrition Conference for Feed Manufacturers, Rochester, NY, p. 130
Drackley, J.K. 2001. Milk feeding strategies for calves. Does Accelerated Growth make sense? Page 27 in Proceedings of the Professional Dairy Heifer Growers Association National Conference, March 22-24, 2001, Seattle, WA.
Quigley, J. 2000. Managing the preweaning nutrition program. In: Proceedings of the 41st Annual New England Dairy Feed Conference. West Lebanon, NH.
Smith, J.M., M.C. Diaz, M.E. Van Amburgh, D.E. Bauman, and M.C. Lucy. 1998. Ontogeny of the somatotropic axis in milk-fed bull calves between birth and 105 kg. Pages 119-129, Proc. Cornell Nutr. Conf., Rochester, NY.
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