NUTRITION AND MANAGEMENT TO OPTIMIZE CALF HEALTH,The Journal of Farm Animal in Infectious Disease
Vol.10 No.4 2021

GROWTH, AND FUTURE PRODUCTIVITY

特別講演要旨Nutrition and Management to Optimize Calf Health, Growth, and Future Productivity
James K. Drackley
Professor, Department of Animal Sciences,
University of Illinois Urbana-Champaign, USA

The early life period is critical for getting calves off to a good start and allowing them to reach their potential
for future productivity. Colostrum management is the cornerstone of successful calf rearing. The key is to provide
an adequate quantity of high quality colostrum as quickly as possible after birth, and to ensure that stringent
sanitation procedures are followed at each step. The guideline used for many years was that calves should haveblood immunoglobulin G (IgG) concentration >10 g/L at 24 – 48 hours of age. However, many calf raisers achieve
this goal but still suffer from excessive calf morbidity. Recently an expert group established new guidelines forcolostrum adequacy (Lombard et al., 2020). The four categories based on calf blood IgG concentration areexcellent (≥25.0 g/L), good (18.0 – 24.9 g/L), fair (10.0 – 17.9), and poor (<10.0 g/L). These categories are highly
correlated with calf mortality and morbidity and provide a new standard for evaluation of colostrum management.
Part of the effect of better colostrum management results from intake of nutrients and growth factors fromcolostrum. Colostrum is a rich source of protein, fat, minerals, and vitamins compared with mature milk. The
carbohydrate and fat composition is different from mature milk. Colostrum is also rich in hormones such as insulin
and insulin-like growth factor 1 (IGF-1), cytokines, immune proteins, growth factors, and other bioactive
substances. The role of many of these compounds remains to be established, but the mother provides a host ofsignaling compounds to the calf through colostrum. Calves must consume adequate colostrum in order to be able
to take advantage of greater nutrient supply in milk or milk replacer to grow more rapidly.
Recent research has indicated that calves benefit from being fed the transition milk that follows colostrum
production. This milk still has greater concentrations of hormones and growth factors, as well as the transitioning
nutrient composition between colostrum and milk. While the logistics of this practice become difficult on larger
farms, the practice looks promising.
The amount of milk or milk replacer fed to calves has increased tremendously in the last 10 years. Calf growth
responds linearly to increasing milk allowance up to ad libitum intake, with improved feed efficiency. Research
has shown that calves exhibit signs of hunger and distress when milk intake is <8 L/d. Practices important for
feeding more milk include weaning at a later age (8 wk or later) and weaning gradually over at least a 10-day
period. Step-down programs that focus on feeding large amounts of milk early in life followed by progressive
decreases in milk volume beginning at around day 35 of age work well to smooth the transition to dry feed.
Weaning can occur when calves consume at least 1.3 kg/d of starter for 3 consecutive days. Water availability is
critical for starter intake and utilization, and should be provided from the first week of life even in cold climates.
A high quality, palatable starter concentrate should be provided to calves in small amounts from the first weekof life, and should be available for ad libitum consumption at all times. Recent research has shown that with－ 87 －

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intensified liquid feeding programs a starter with 25% (DM basis) CP provides less fat in body tissue gain andgreater growth of the critical gastrointestinal tract and liver tissues than a starter with 20% CP. A small amount of
chopped forage (2 – 5% of the starter grain) often improves overall intake and feed efficiency, but free choice
forage should not be provided until about 6 months of age. Conditions in the undeveloped rumen are not favorable
for fiber digestion until the absorptive papillae are developed, which helps to maintain the rumen pH at > 6.0.
After weaning calves should continue to receive the starter feed for ad libitum intake, with no more than 5 to
10% chopped forage included. Once calves have adjusted to the weaning transition, a grower concentrate cangradually be substituted for the starter mix.

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