However, research trials by AgResearch and other organisations around the world have demonstrated the lifetime performance impacts of investing in calf feeding practices write Drs. Sue McCoard and Ajmal Khan, the Animal Nutrition and Physiology Team, AgResearch Limited, New Zealand.

Feed can impact the calf’s development (e.g. calf growth, health and welfare, body composition) but also the later in life (e.g. amount and quality of milk produced by dairy heifers and meat and carcass quality by dairy-beef animals), and even their environmental footprint.

Newborn calves rely exclusively on milk to provide the nutrients and energy required to grow and develop during the first few weeks of life. At birth, the rumen has little functionality. Physical, metabolic and microbial development of the rumen is required for a calf to transition from liquid (milk) to solid feeds. Therefore, careful attention to feeds and feeding management is essential to provide the best opportunity for a calf to survive and perform in artificial calf rearing systems.

There are many different “milk” options available: whole milk from the vat, transition milk (from the second to eighth milking after calving) and milk replacer. Whole milk, by nature, provides all the nutrients growing calves need but it may not always be possible or cost-effective to use whole milk. Transition milk may be a good alternative if stored correctly to avoid microbial contamination.

A wide range of milk replacers are also commercially available, and while they can be similar to milk, they do vary in quality and thus price. The best quality milk replacers are those made from 100 percent milk proteins (casein-dominant to support curd formation in the abomasum) with little to no vegetable fat. Young calves are less effective at digesting vegetable proteins and fats, and whey proteins do not curd, meaning lower growth rates are common when milk replacers include these ingredients.

The amount and duration of milk feeding also influences calf growth. In general, increasing milk allowance improves calf growth, health and wellbeing. AgResearch trials suggest that feeding calves at least 20 percent of their birth weight – i.e. eight litres (L) a day for a 40 kilogram (kg) calf – will result in good calf performance. The percentage-based volume, rather than a set volume, helps to avoid underfeeding as calves’ birth weights vary.

Calves start consuming solid feeds in the first two weeks after birth and the intake increases over time to support rumen development. A functional rumen enables a calf to transition from liquid to solid feed diets. Rumen development is influenced by solid feed intake and its fermentation by rumen microbes, the time of introduction of solid feeds, the age at weaning, and the weaning methods.

Calves are commonly fed grain-based starter feeds to support rumen development. However, AgResearch trials have demonstrated that calves can be reared exclusively on good-quality forage with no negative effects on lifetime growth, health, meat yield and quality. Including forage in the diet of calves fed starters can also improve rumen development and promote solid feed intake around weaning.

Transitioning from milk to solid feeds, and between different solid feeds (e.g. starter to pasture) should be done gradually over two weeks to enable the calf to adjust to the new diet. This will help to avoid growth checks and animal health issues. This careful transition is especially important for calves fed high milk volumes (> eight L/day) as high milk intake can suppress solid feed intake.

Recommendations from recent research to help improve calf rearing practices include:

• Whole milk is natural but transition milk and high-quality milk replacers are good alternatives
• Feed calves a minimum of 20 percent of their birth weight, preferably split into at least two feeds a day
• Feed milk warm, that’s less than 40 degrees Celsius
• Ensure all equipment used for milk feeding is thoroughly cleaned after each feed to reduce infectious disease incidence in calves
• Wean off milk gradually over two weeks, no earlier than eight weeks of age and only when calves are consuming solid feed and showing rumination behaviour
• Consider not just the cost but the quality of feeds (both for milk and solid feeds)
• Solid feeds (forages and concentrates) should be introduced from one week of age and be freely available before weaning
• Gradual transitions between feed types should occur over two weeks