ISSUE FOCUS FEED & ADDITIVE MAGAZINE February 2026 41 The Quantity distributed must provide the calf with a sufficient immune load to establish protection. A newborn calf requires an intake of minimum 200 g of IgG in its first meal. This is typically achieved by feeding a volume equivalent to 10% of the calf’s body weight (BW), which makes approximately 4 liters for a 40 kg Holstein calf. Feeding only 2 liters has been shown to result in significantly lower serum IgG status and increased incidence of scours. While a second feed of 2 liters is recommended within 12 hours, providing more than 12% BW in a single feed may cause gastric disorders without necessarily increasing serum IgG levels2. Quickness is one of the most critical factors because the calf's intestinal permeability to large molecules like antibodies decreases exponentially after birth. IgG absorption is highest within the first two hours of life (approaching 30%) and drops to nearly zero after 20 hours. Simultaneously, the quality of colostrum in the udder degrades quickly: there is a 25% loss of IgG concentration by the second milking (12 hours) and a 50% loss after 24 hours3. sQueaky clean management focuses on hygiene to prevent the calf from ingesting pathogens before its immune system is established. Scientific standards require colostrum to have a total bacterial count below 100,000 CFU/mL and less than 10,000 CFU/mL for E. coli. High bacterial loads directly interfere with the efficiency of antibody absorption across the intestinal wall. Finally, Quantifying involves verifying the success of passive immunity transfer by measuring serum protein levels in the calf ideally, between 24 to 48 hours of age, or up to 7 days maximum. A good transfer is marked by serum IgG levels ≥ 18.0 g/L or a Serum Total Protein (STP) ≥ 5.8 g/dL (Brix ≥ 8.9%)4. BIOLOGICAL IMPORTANCE OF IMMUNITY TRANSFER Unlike many species, cattle’s placenta is impermeable to large proteins, including immunoglobulins. Consequently, calves are born without immune defences and no circulating antibodies to protect them from environmental pathogens. They depend entirely on the passive immunity transferred via colostrum to survive environmental challenges in the first weeks of life until their own immune system becomes entirely functional at approximately 3 to 4 weeks of age. When the consumption of colostrum is not of the right quality or quantity, it may lead to Failure of Passive Transfer (FPT), defined as serum IgG levels below 10 g/L. It can have significant economic and health consequences, especially on the long term. Research indicates that calves with poor immunity transfer are 4.3 times more likely to die before weaning and are significantly more susceptible to Figure 1. Colostrum "5Q's" rule Using a refractometer is recommended, visual assessment is unreliable. Deliver minimum 200g of lgG in the first meal. Absorption efficiency drops significantly after the 2nd hour of life & is close to zero after 20h. Bacterial contamination physically blocks lgG absorption across intestinal wall. Check the success of immunity transfer by measuring serum protein level between 24 to 48h of life, up to 7 days maximum. 1. QUALITY 2. QUANTITY 3. QUICKNESS 4. SQUEAKY CLEAN 5. QUANTIFYING 50 g/L min lgG 10% BW ratio ≥8,9% Brix ≥18 g/L Serum lgG ≥5,8 g/dL Serum protein Birth Total count < 100 000 CFU/mL E.Coli < 10 000 CFU/mL Critical (6h+) Optimal (0-2h) 4 Liters 40kg calf 2 Liters 2nd feeding ≥ 22% Brix Minimum ≥ 28% Brix Excellent
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