The dairy industry has made a lot of progress in the past decade or so regarding the care and nutrition of calves. To see how far weâve come, consider the history of milk replacer. Milk replacer was developed initially as a low-cost alternative to feeding calves whole milk, utilizing cheap fat and protein sources that were not well digested by calves. Many early formulas were very low in fat (Kertz and Loften, 2013). Eventually, formulas with 20% protein and 20% fat with feeding rates of about 0.5 kg/head/day became the norm. At this feeding rate, a 20:20 milk replacer can meet the maintenance requirements of a 50 kg calf, however there is little left for growth. As a calf gains weight, her maintenance requirements increase as well, and she would need to consume dry feed in addition to milk replacer in order to continue growing. The goal of these kinds of programs was to maximize grain intake and often wean calves early. This traditional strategy of restricting nutrients in the liquid diet is effective in keeping feed costs per day low, especially since dry feed is generally much less expensive than milk replacer.
Many producers have changed to a different strategy for raising dairy calves. Instead of trying to minimize total cost/head, they are viewing calves as an investment in the future herd. There have been several studies indicating that an increase in preweaning average daily gain (ADG) is correlated with higher milk production in the first and perhaps subsequent lactations. As a result, many veterinarians and nutritionists recommend the goal of doubling birthweight by 56 days of age, which can be achieved with an ADG of about 0.70 â 0.75 kg/day preweaning. Much of this growth comes from feeding higher amounts of milk replacer or whole milk, and therefore it is common to see feeding rates more than twice the traditional 0.5 kg/day. Along with higher feeding rates, many producers feed milk replacer with higher protein levels, often above 24% crude protein (CP) as fed. The goal with these accelerated feeding programs is to ensure early growth rates are not inhibiting future milk production.
Which strategy makes the most sense economically? It seems that the traditional strategy is to minimize costs per day, whereas the accelerated growth strategy is meant to maximize growth. Nevertheless, youâre missing out if youâre only considering costs without measuring performance or vice versa. Because calves are not yet producing milk, itâs not as easy to put a value on their performance compared to lactating cows. However, you can view each kilogram of growth as a calfâs âoutput.â In order to get the best value for your feeding program, you want to utilize a program that gets you the lowest cost/kilogram of gain. To calculate your feed cost/kg gain, you need to know your feed costs and your ADG.
Accelerated feeding programs often are much more expensive per day than the traditional feeding program. However, because they are designed to provide more nutrients for growth, they often cost less per kilogram of gain. With this program, you are âdilutingâ the maintenance costs so that your costs/kg gain are reduced. See Tables 1 and 2 to see an example of how predicted growth and cost/kg gain compare with different milk replacer feeding programs.
Table 1. Predicted growth rates according to different milk replacer programs
|20:20 Milk Replacer||24:18 Milk Replacer|
|Feeding rate (kg/d)||Predicted ADG for 50 kg calf (kg/d; includes no starter intake)|
Table 2. Predicted milk replacer cost/kg gain according to different milk replacer programs
|20:20 Milk Replacer ($2.96/kg)||24:18 Milk Replacer ($3.23/kg)|
|Feeding rate (kg/d)||Predicted milk replacer cost/kg gain ($/kg; includes no starter intake)|
Itâs worth noting that the predicted growth rates in Table 1. differ between the different milk replacers depending on the feeding rate. When designing a feeding program with the goal of having a low cost/kg gain, both the feeding rate and the nutrient composition of the feed must be considered. At a low feeding rate, energy is usually the limiting nutrient. Therefore, feeding a higher protein replacer like a 24:18 will not result in higher ADG compared to a 20:20 at 0.5 kg/day. Because a 24:18 is more expensive than a 20:20, your cost/kg gain will be higher with the higher protein milk replacer at the low feeding rate.
However, at a higher feeding rate like 1.0 kg/day, protein will become the limiting nutrient if youâre feeding a 20:20. For that reason, the additional protein in the 24:18 will result in higher ADG when fed at the higher feeding rate. Even though 24:18 is more expensive per kilogram, and in effect, more expensive per head per day, the additional growth you can expect from a 24:18 at a feeding rate of 1.0 kg/day will cause your cost/kg gain to be lower than it would be with the 20:20 milk replacer.
For the sake of simplicity, the above milk replacer example does not account for additional factors that will affect calf maintenance requirements. Increased bodyweight, cold environmental temperatures, and other stressors will increase energy requirements for maintenance, therefore affecting ADG. This example also did not consider starter intake. We can assume in most cases that calves will consume less starter when fed high amounts of milk replacer compared to low amounts. Each of these factors should be considered when designing a calf feeding program. You should work with your nutritionist to determine which feeds and feeding rates will work best on your farm to result in a low cost/kg gain.
The dairy industry has made great progress in the area of pre-weaned calf nutrition and growth. With so much focus on increasing preweaning ADG, many farms have adopted accelerated feeding programs resulting in larger, healthier calves at weaning. However, it seems that less focus is on the performance of calves postweaning. One of the largest challenges with feeding high rates of milk/milk replacer is that calves may not consume much starter prior to weaning. This could put them at risk for a âpost wean slump,â in which calves grow more slowly or lose weight in the weeks following weaning. If this happens, it is detrimental to cost/kg gain. Unfortunately, many producers that invest a lot in growing calves quickly with an accelerated milk or milk replacer program often are at high risk for this post wean slump. Itâs a good idea to not only collect calf weights at weaning, but also several weeks after weaning to identify whether calves maintain an adequate ADG.
The good news is that a post wean slump often can be avoided through good management practices. Keep in mind that change is stressful for calves, so make their transitions to new feed, groups, and facilities gradual. If youâre trying an accelerated liquid feed program, you should gradually wean calves over a minimum of 14 days. Make sure calves are eating at least 1.5 kg of starter for three consecutive days before completely weaning them, and consider continuing to feed the same starter for a week or two after weaning. Make sure feed and water are kept fresh and are easily accessible after weaning. Pay attention to all the things that are new and different to a calf in the post-weaned environment and make sure they donât become an obstacle for eating and drinking. You may have to make modifications. For example, if calves are in a pen where they have to reach through slant bars to reach feed for the first time, you could hang a trough of feed on the inside of the pen for a few days to make sure calves can find feed easily after arriving in the new pen.
Measuring both your feed costs and your calf ADG to determine feed cost/kg gain will help you understand the efficiency of your calf program. If you donât know your current cost/kg gain, try calculating it to see where you are today. Any time you make changes to your calf program, evaluating that number will help you decide whether those changes are worth it or not.
Alyssa Dietrich is a calf and heifer specialist with Cargill, based in Pennsylvania. She holds a B.S. in Animal Science from Penn State and M.S. in Dairy Science from Virginia Tech. She can be reached at email@example.com.
Kertz, A. F., and J. R. Loften. 2013. Review: a historical perspective of specific milk-replacer feeding program in the United States and effects on eventual performance of Holstein dairy calves. Prof. Anim. Sci. 29:321â332
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