Feature JANUARY 2020 www.irishfarmersmonthly.com Supplying calves with enough energy for growth Liam Gannon of Volac Ireland examines the best way to ensure your calf gets the right nutrients in the cold weather Calves use their feed in lots of ways. First, they must maintain their normal body functions (e.g. digestion, respiration), then they use energy to keep themselves warm and fight disease, and finally energy left over can be used for growth. All calves must be fed at least twice a day (under the Calves Welfare Directive 2008/119/EC) – during the first three to four weeks of life, starter intake is minimal, so the energy available to the calf is directly proportionate to the supply of milk or milk replacer being supplied twice daily. A healthy 45-kg calf in a warm (15 to 25°C), low disease environment will require approximately 380g milk powder for maintenance alone1. Only the milk solid balance above 380 g can be used for growth. However, the amount of energy needed to keep themselves warm and support their immune system, and thus the amount leftover for growth is highly dependent upon the environmental temperature and the health of the calf. During periods of cold weather, calves require more energy to keep warm - if calves are not fed enough milk, growth rates will plummet, and they will become more susceptible to diseases. During the first 3 weeks of life, calves are very susceptible By four weeks of age, calves are more robust and will not ‘feel the cold’ until temperatures drop below 6 to 10°C. Older calves are more likely to be eating calf starter, driving rumen development and a functional rumen produces its own heat which helps to keep the calf warm3. How much extra milk does a calf need during cold weather? Young calves (<3 weeks of age): During the first three to four weeks of life, when starter intake is minimal, the energy available to the calf is directly proportionate to the supply of milk or milk replacer. Therefore, the best way to maximise energy intake is to feed them more milk at least twice a day. Based on a milk replacer containing 19.8 ME MJ/kg DM, a calf will require an extra 55g of milk powder per day for each 5°C drop in ambient temperature below 20°C, to maintain the same growth rate as when its warmer (see Table 1). For example, at a temperature of 10°C, a calf will need an extra 110 g of milk powder – i.e. if a calf is normally fed 625 g milk powder per day, it will need a total of 735 g milk powder per day (625 + 110 g) to continue to grow at the same rate as when the temperature was 15 to 25°C. Older calves (assuming they are eating starter) require additional energy to maintain growth when temperatures drop below 10°C - an extra 55g of milk replacer per day is needed for each 5°C drop in temperature below 10°C (see Table 1). Increasing the amount of milk solids offered can be achieved by either increasing the concentration of the calf milk replacer (e.g. from 125 g per litre to 150 g per litre) or by increasing the volume fed per day (e.g. from 5 to 6 litres), or by increasing the number of feeds per day. Example: Normal feeding rate: 5 litres per day mixed at 125g per litre = 625g milk powder per day Ambient temperature drops to 10°C: increase the amount of milk solids by 110 g per day How to increase milk solids by 110 g per day: 1. Feed 5 litres per day (2.5 L twice daily) mixed at 150g per litre = 750g milk powder per day OR 2. Feed 6 litres per day (3 L twice daily) mixed at 125g per litre = 750g milk powder per day THE ENERGY BANK BALANCE A healthy calf in a warm, low disease environent hads more energy available for growth Only the balance above will drive growth 380g 380g Immune system Keeping warm Digestion, respiration etc Source: Volac 18 to the cold. Temperatures only have to drop to below 10 to 15°C for a young calf to require more feed to maintain their body temperature, grow and remain healthy. Young calves are prone to heat loss because of their high surface area to body weight ratio and they also have poor insulation (i.e. thin skin and subcutaneous fat)2. Furthermore, they will not yet be ruminating so less heat is generated by digestion.