NEW NASEM REQUIREMENTS FOR CALVES
This week’s blog is a summary of a presentation given by Dr. Jim Quigley during a previous webinar of the Dairy Calf and Heifer Association. Dr. Quigley is a well-known calf researcher who has helped improve the well-being of calves for more than 30 years.
Back in 2001 the National Research Council published a set of nutrient requirements for dairy cattle, including calves. This same organization now known as the National Academies of Science Engineering and Medicine (NASEM) has recently updated these requirements as the NASEM 2021.
SETTING THE STAGE
The NASEM 2021 defines a calf as any animal less than or equal to 18% of mature body weight. An animal of the Holstein breed less than or equal to 275 lbs. (125 kg) would be considered a calf.
Understanding feed intake is the most important factor to understand when calculating nutrient requirements. The 2001 NRC did not include an estimate of Dry Matter Intake (DMI). The new NASEM includes 2 different equations for DMI, one for calves in temperate and sub-tropical climates. The primary drivers of these equations include body weight of the calf, metabolizable energy (ME) intake from the liquid diet, and the age at which starter was offered.
During this same time period, Dr. Quigley and his team at Cargill also published a DMI prediction equation for calves up to 4 months of age. The primary drivers of their equations were similar to those of the NASEM equations and included the age of the calf, ambient temperature, and MEgap (ME required – ME intake from liquid) based on body weight and average daily gain of the calf.
Both equations estimate very similar intakes until about weaning time, and then they start to deviate after weaning because of the differences in which the additional feeding of fiber was considered.
CALF GROWTH
NASEM equations estimating calf growth are based upon ME-allowable gain and Metabolizable Protein (MP)-allowable gain. We can conclude that energy and protein must be in balance to prevent calves from growing too fat, or even growing slower than expected. Typically, calves will need somewhere around 50-55g of protein for every mega calorie of ME.
ME requirements are based off requirements for maintenance and gain. Maintenance involves energy used to maintain body weight, perform body functions, and maintain body temperature. Growth involves energy used for growth.
MP requirements involved a really big change in calculation. The 2001 NRC used a concept called Apparently Digestible Protein (ADP) and a concept called Biological Value to calculate requirements for protein for calves. The new 2021 requirements now use a MP system, which is more consistent to systems used for calculating requirements for older animals.
The MP model is driven on the basis ME-allowable gain, with protein requirements calculated for maintenance and the predicted growth rate. Maintenance includes net protein losses (skin, hair, urine, feces). and growth is defined as the net protein needed as a function of retained energy and body weight gain. The efficiency of which net protein is converted to metabolizable protein decreases with the age of the animal.
PROTEIN SUPPLY
Source of protein is also something that is considered in the new NASEM requirements. Newborn calves get all their MP from dietary sources such as milk or milk replacer. Once a calf begins to consume starter and the rumen bacteria begin to ferment carbohydrates, the calf is also supplied with microbial protein. Weaned calves get their MP from a combination of undegraded dietary protein and microbial protein. The change from solely utilizing dietary protein, to incorporating microbial protein is a big change for the calf.
APPLICATION
Dr. Quigley always does a fantastic job teaching how we can apply research to everyday life. He suggests putting some thought into your goals around average daily gain (ADG). Ask yourself:
- How fast should my calves be growing?
- How fast can my calves grow?
- How much am I willing to pay to get my calves to grow?
- What hurdles are in my operation that may impair growth?
Work with your nutritionist to answer these questions and to establish a feeding program that will allow you to achieve desired growth rates. Keep in mind that growth prior to weaning is driven by milk intake, and that starter and grower quality are critical.
The image featured below was created by Dr. Quigley and shows some example feeding programs and the allowable gain made possible by each one. Most of them make it possible to double birth weight by 60 days of age.
If you need help modeling or creating a calf feeding program reach out to the Cargill Calf and Heifer Specialist in your area and they can help customize a program for you.
For more information on calf related research check out Dr. Quigley’s website calfnotes.com. There is a wealth of information there that is very useful for calf raisers and consultants alike!
Written by: Mariah Gull, M.S.