Abstract: Calf milk replacers (CMRs) are typically formulated from a range of lower-value milk products and may have reduced curding ability when casein proteins are absent or denatured. Whilst there are industry claims that vealer calves in Europe can be reared on such CMRs, there is no NZ data to substantiate these claims. In Experiment One, 240 calves were reared on three milk replacers.

Diet A was a curding CMR based on whole-milk powder and skim-milk powder. Diet B was a non-curding CMR based on whey and vegetable fat. Diet C was a non-curding CMR based on whey, soy and vegetable fat. A salmonella challenge occurred in the rearing facility during the first two weeks of rearing. Calves on Diet A suffered a much lower incidence of sickness than those on Diets B and C (15% vs 34% vs 61%) respectively. Mortality was also lower (1.25% vs 5% vs 5% respectively). In Experiment Two, 90 calves were fed on the same diets from four days to 13 weeks of age. There were no effects of diet on disease or mortality. Calves on Diet A, B and C had growth rates to 13 weeks of 0.63, 0.60 and 0.53 kg/day, respectively. In conclusion, rearers need to be aware that there a risk when feeding non-curding milk replacers to young calves, particularly when timely weight targets need to be achieved.

Introduction:  When calves are reared by natural suckling they receive numerous small feeds of whole milk which curds in the abomasum because of the action of rennet on casein proteins. Historically, New Zealand calf-milk replacers (CMR) have been based on whole-milk and skim-milk powders unsuitable for export. However, in Europe and the US, it has become uneconomic to rear calves on skimbased CMRs (Davis & Drackley 1998) and non-curding whey CMRs have been developed and well tested under US and European conditions.

Whilst products containing whey and vegetable proteins are widely used in Europe, there are some fundamental differences when compared to New Zealand calf rearing systems. In Europe, calves are more robust as they are at least 7-10 days old before they are on-sold from the dairy farm. Calves in New Zealand are generally only four days old at point of sale and are less resistant to environmental challenges. They also tend to be fed on a once-a-day milk feeding regime. Two experiments were undertaken to examine the performance of young calves fed curding and non-curding CMRs under New Zealand conditions.