Carried out by scientists from AgResearch with support from Spring Sheep Dairy and funding from NZAgbiz, the research considered the use of different compositions of milk replacers in artificial rearing systems, what it means for animal performance and health, and consequently costs for the producer.

Around 200 East-Friesian male lambs were allocated to pens using a randomised experimental design and reared on one of two commercially available milk replacer formulations - one being 80 per cent casein and 20 per cent whey milk protein and 100 per cent milk fat, and the other 50 per cent casein, 40 per cent whey milk protein and 10 per cent hydrolysed wheat protein and 100% vegetable oil. The lambs were able to feed on demand from automatic feeders, with free access to grass hay also available.

Study lead author and AgResearch senior scientist Sue McCoard says the results seen in lambs fed either milk replacer were similar when it came to death rates. However significant differences were observed in growth rates, health and the need for use of antibiotics.

“Among the key findings was that feeding a milk replacer containing vegetable ingredients versus 100 per cent milk ingredients resulted in lower growth rates (242 versus 296 g/d) – with four times more lambs failing to reach the minimum weaning weight by the end of the study,” Sue says.

“The milk replacer containing vegetable ingredients was also associated with an increased incidence of health issues - notably scouring, pneumonia, pink eye, and external infections. The cost of health intervention by lamb was $17.20 per head, compared to $7.32 per head for those fed the 100 per cent milk ingredient replacer. We also saw an increased likelihood, of two and a half times, of therapeutic antibiotic use to treat health issues among those lambs reared on the milk replacer containing vegetable oil.”

“Notably, lambs fed milk replacer containing vegetable ingredients were eight times more likely to get scours and three times more likely to get pneumonia.”

“These results indicate feeding neonatal lambs in the first five to six weeks of life with milk replacer containing vegetable proteins and fats should be avoided. Improving early life nutrition through feeding of milk replacers containing 100 per cent milk-based ingredients supports growth, health, and welfare by providing protection against disease and reduces costs associated with health care. The reduction in the therapeutic use of antibiotics also contributes to meeting consumer demands for chemical-free food production and reducing the risk of antimicrobial resistance.”

The effects of different combinations of milk replacer ingredients used in this study are still to be established.

“It is clear however from this research and other studies, that investing in the right choices around the early life nutrition of artificially reared livestock is important, and has an increasingly important role in animal agriculture,” Sue says.

“It not only helps producers avoid costly animal health and welfare issues but can also provide an advantage for lifetime performance as well as reducing wastage which is important for sustainable and ethical livestock production systems.”   

You can read the full research at: https://www.appliedanimalscience.org/article/S2590-2865(21)00039-2/fulltext