In the past 15 years there has been a large amount of research addressing this issue. Each study has its own objectives and differences/limitations as it relates to much of the North American dairy industry.
The three studies from Israel using low fat milk replacers containing non-milk protein in comparison to high levels of whole milk found a positive relationship (one a trend, two showed significant effects) between early life nutrition and milk production.
One study reported a decrease in age at puberty and another of these reported a decreased age at first calving with the higher levels of nutrient intake before weaning.
The differences in diet components being (by US standards) deficient in fat (12, 13, or 15% fat) of unknown fatty acid composition (Bar-Peled milk replacer contained animal and vegetable fat; fat sources were not described in the other papers) and questionable on protein level or amount of digestible protein
These issues make for a complete confounding of nutrition when compared to high levels of whole milk containing 24 to 25% crude protein with highly digestible protein sources that are of high biological value for the calf. In addition, the milk diets contained 24 to 29% milk fat that is known to be highly digestible and of high value to the calf, which makes this diet comparison valid ONLY for these specific diets.
These studies do not imply that milk replacers used in the US are not adequate for feeding dairy calves or that changing to whole milk from milk replacer will by itself impact age at puberty, calving, or lactation.
These studies do imply that poorly formulated milk replacers fed at low rates (marginal compared to NRC (2001) nutrient requirements) might be detrimental to the productivity of the animal compared to adequate to high levels of whole milk. This same effect also has been shown in the past. High incidences of disease as well as inadequate housing, management, or nutrition in young calves can have long term negative effects on production.
The four peer-reviewed studies that directly compared milk replacers more typical in the US, with similar protein and fat source quality, all met or exceeded NRC (2001) requirements for young calves. These studies compared levels of milk replacer fed and offer a more valid comparison of the real issue in question.
These studies all showed that there were no significant effects of early nutrition on lactation performance, although the Michigan study observed a tendency for improved milk production if genetic variation was included in the analysis.
In addition, there have been three abstracts published that compare similar milk replacer diets at different levels in systems done in or similar to those used in North America.
Two of the three showed no effects of early nutrition on milk production. Two additional abstracts describe studies comparing different feeding rates of whole milk. Neither study found significant effects of higher feeding rate on milk production in the first lactation.
Therefore, based on multiple peer- reviewed publications conducted by separate research groups from around the world that represented university and industry groups working together, the results clearly show that there are no effects of a standard milk replacer feeding rate as compared to an accelerated milk replacer feeding rate on milk production.
It is worth noting that increasing the feeding rate for young calves has been proven to improve growth rates and body condition of calves, particularly during the milk-feeding period. Detailed discussion of these results is beyond the scope of this review, but increasing milk replacer feeding rate can have positive impacts on calf growth with no negative impact on milk production later in life.
Calves on an accelerated feeding program must continue to be fed and managed well to maintain the growth advantage gained before weaning and to capitalize on that growth by conceiving and calving at an earlier age. However, research trials and experience on farms show that in many cases calves on an accelerated program lose their growth advantage after weaning, which calls into question the economic payback for the additional investment required for the program.
