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What's the impact of dietary protein on heifer growth and milk yield?

20 April 2021

Protein feeding strategies to help lower the carbon footprint and financial costs of heifer rearing are the focus of a new trial involving Nottingham University and Mole Valley Farmers.

The CIEL-funded project will look at the impact of protein nutrition on pubertal heifers from 12 to 15 months of age. Lowering dietary crude protein using British-sourced feeds and following the impact of pubertal feeding through to milk production makes it a world-first.

“The potential impact of protein type on heifer growth and subsequent milk yield is not widely understood and has not been investigated in the UK with high genetic merit animals,” says Mole Valley Farmers’ Head of Nutrition, Dr Chris Bartram, who instigated the research work. “Recent work has suggested that feeding higher levels of Digestible Undegradable Protein (DUP) may be beneficial, which is an area we want look at in more detail.”

With the industry working towards being Net Zero by 2040 and the environment coming into sharp focus as part of the Government’s Path to Sustainable Farming Transition Plan, there’s never been a more important time to tackle the environmental impact of heifer rearing.

Dr Jean Margerison, Associate Professor of Ruminant Nutrition at Nottingham University, believes protein feeding in particular needs to be addressed considering soya’s potential impact on the environment. This is coupled with the fact cattle can secrete over 45% of the protein they eat.

She believes the answer lies in making better use of homegrown forage and balancing it with quality, British-sourced proteins to help achieve good heifer growth rates, first calving age and maturity, whilst lowering feed protein imports. Thinking about the quality and degradability of dietary protein, rather than crude protein content alone, is key to hitting target growth rates and performance, and is one of the main areas being looked at in the study.

“We may also get better mammary development as a result of the higher DUP and thus metabolisable protein (MP) supply. It is possible that the improved amino acid supply will also benefit growth, lean tissue and mammary gland development,” Jean adds.

She says the pubertal stage is one of the most important growth stages that affects mammary gland development and subsequent function. The first comes in the first 12 weeks of age, which is where most previous research has focused. Such research has shown every 100g of average daily gain pre-weaning is worth 200kg more milk over the first three lactations.

Getting protein feeding right in the pubertal stage should lead to greater milk yields when heifers enter production and better feed conversion efficiency. The fact they enter milk production quicker and are more productive should also be a big plus. More importantly their maturity and weight at first calving ensures better fertility, lower claw related disorders and lower replacement rates.

Jean adds: “Investing in the optimum nutrition for the heifer has a significant effect on lifetime yield and farm profit. It also has a potential major impact on farm carbon footprint. It must be a priority for all dairy farmers.”


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