Modern calf feeding is based on the success of the milk replacer program offered during the first 6 to 8 weeks of life, if only because feeding raw, natural milk remains an expensive proposition in most cases. If calves were left to their natural instincts, they would consume about 10 kilograms of milk per day, growing rapidly, efficiently and without scours. But that is seldom the case, especially with dairy calves, as milk prices remain (slightly) above those of a good quality milk replacer.
Naturally, picking the right milk replacer is the first order of business, and one can be spoiled by the wide offer of products and options. An all-dairy milk replacer is ideal, but rather expensive, whereas an all-vegetable one is inexpensive but risky as it can cause scours and slow growth. In the end, a compromise is achieved where a milk replacer depends heavy on dairy ingredients with a small contribution of mostly vegetable proteins to keep costs reasonable and quality as high as possible. Starch and wheat flour are often added for various reasons, but they are the mark of a low-cost product and require mixing temperatures that cause protein denaturation. As such, products with starch and flour should be avoided.
Having selected the right milk replacer, there are three areas that cause the most problems in the feeding of newly born calves, and when a milk replacer program is evaluated at the farm level, these are the key areas an expert will look at first glance.
1. Mixing and feeding proportions
A cow’s milk contains about 12.5 percent solids (dry matter). A dry milk replacer contains 95 percent or more dry matter, but we will assume it is 100 percent to make calculations easier. To achieve the same concentration of solids, the basic rule of thumb of 1+7=8 is often followed. In this way, adding 1 kilogram of dry milk replacer powder and 7 kilograms of warm water will create 8 kilograms of liquid milk replacer with 12.5 percent solids (1/8×100=12.5). It is often recommended to increase the level of solids for weak calves and also during the very cold months of winter. Increasing the amount of liquid milk replacer offered daily, with a constant level of solids, is discouraged as it can lead to diarrheas.
Here, everything appears easy and reasonable, but this is an area where most mistakes are made. First of all, the powder portion is rarely being weighed. Instead, it is being measured using a volumetric device like a scoop, a container or a bucket. This would be fine if the measuring was always done accurately, and if the density of the milk replacer remained constant, but this is never the case. Thus, a scoop of powder never weighs the same, and the resulting liquid milk replacer never has a constant level of solids. It does not help that feeding is done by liters (volume) per feeding, when it should be in kilograms (weight) per feeding. Of course, the density of milk is near 1 (actually it is 1.032), but a milk replacer is not the same — especially if solids fluctuate widely and ingredients like starch are being used. Thus, a second level of possible error is introduced.
Therefore, the first order of business in evaluating a calf milk replacer feeding program should be to check solids and actual amount being fed per calf.
A portable, inexpensive, thermometer is indispensable in checking temperatures. Water used for mixing a milk replacer should be warmed up to 45 degrees Celsius. Higher temperatures will denature proteins, making them less digestible for the animal, and they will also cause fat globules to fall out from their protein cover (in the so-called, fat-filled whey products), making the mixing of fats impossible, especially without the presence of a lecithin-type of product. Again, the presence of vegetable proteins and starch require higher temperatures to dissolve and come into suspension, usually up to 65 degrees Celsius, something that is counterintuitive because the use of less expensive proteins causes damage to the more expensive proteins, resulting in an overall low-quality protein profile. Starch and wheat flour, often used to replace expensive lactose and give a more creamy appearance to the liquid milk replacer, require even higher mixing temperatures, prolonged mixing times and vigorous mixing effort. Reading labels can often provide useful clues on the actual composition of several cost-effective products.
The temperature of feeding the liquid milk replacer is also important. It should be about 38 degrees Celsius (100 degrees Fahrenheit), with warmer milk causing overconsumption and colder milk causing underconsumption. It might be important to adjust temperatures during the very hot and very cold seasons, but given the fact we always offer less than 10 kilograms of liquid milk replacer, it is rather simple to keep the temperature at 38 degrees Celsius year-round, especially when multiple meals are offered.
A simple thermometer is neither expensive nor difficult to carry along during a farm visit, and checking milk replacer mixing and feeding temperatures can reveal potential problems.
3. Number of meals per day
Most calves will be fed on a two-meal daily program, with each meal roughly at 3 kilograms, giving a total of 6 kilograms of milk replacer per day. This is below their requirements, creating the need for supplementary nutrition in the form of a dry feed, and later, roughage. Feeding more meals per day (say, three) is possible and more desirable from a physiological point of view, but this will discourage intake of dry feed. And it is the goal of any successful milk replacer program to get calves consuming dry feed as soon as possible. In contrast, giving one large meal per day (all 6 kilograms in one go) is to be strongly discouraged as it can cause diarrheas, without leading to a healthy pattern of gradually increasing dry feed intake.
Toward the end of the milk-feeding period, about one week before weaning, calves should be gradually weaned off milk. This is done by either reducing the amount of milk per feeding, or, as it happens most often, by skipping one of the two meals (the same every day). An abrupt weaning is also possible, especially if calves are not moved to another pen at the same time, so that weaning stress is not compounded by other stress sources. In general, weaning can be accomplished when calves have doubled their birth weight when fed on a limited milk replacer program. This ensures they have consumed enough dry feed to develop their rumen functions and continue without the fear of falling back or scouring. Several guidelines regarding feed intake goals during the last week pre-weaning exist, but as it is difficult to measure individual feed intake on a daily basis — at least in commercial settings — body weight remains the most useful index of success.
Thus, calves fed on a program of two meals of liquid milk replacer per day, and having free access to water, dry feed and roughage of the highest quality possible should double their birth weight by the time of their weaning, which could range from 6 to 8 weeks of age.