Undersupply of Protein to Suckler Cows: What Are the Implications?

The available forage, climatic conditions and the measures for reducing ammonia emissions can adversely affect protein supplies for suckler cows. What is the impact on the weight and intake of the cows and their calves?

A lower protein content of the diet may have implications for the weight and intake of suckler cows and their calves. Agroscope has set up a trial to study the impact of an undersupply of protein on two different breeds of cow, Limousine and Angus.

Short-term undersupply of protein

As part of the study, the protein supplies for suckler cows were reduced by 15% to 40% with respect to the recommendations for a period of 25 days. The protein-deficient ration consisted of 45% to 50% maize silage and extenso hay with no protein supplement. During the following period, protein supplies were rebalanced with protein-rich supplements.

Implications for zootechnical parameters

During the period of protein-deficient feeding the cows lost over 20 kg live weight and a 10% decline in intake with respect to that of the control group was observed. The impact was more marked in Angus cows, with their higher milk-production potential, than in the Limousines. The calves of the undersupplied cows had a lower average daily weight gain during this period and ingested more hay. The calves’ intake behaviour indicates a hay-for-milk substitution effect.

Potential for resilience

After a 25-day reduction period, protein supplies were rebalanced. During the weeks that followed, the cows partially made up their weight-gain and intake deficits. The Limousines regained weight more rapidly than the Anguses, showing a greater potential for resilience. However, the calves of both breeds, which were monitored beyond the experimental period until weaning at 10 months, still lagged behind their conspecifics in terms of live weight.  


  • A protein supply around 40% too low with respect to the recommendations quickly results in major effects on the forage intake and weight of both suckler cows and their calves.
  • The higher the milk-production potential of the cows, the greater the implications are.
  • Based on their weight trends, Limousine cows are more resilient than Anguses.
  • During a growth period in which they are highly dependent on the milk production of their mothers, neither Limousine nor Angus calves were able to catch up completely with calves from mothers fed according to their needs in terms of weight at the time of weaning.
  • Maize-silage-based rations require the use of a protein supplement that is adequate in both quantitative and qualitative terms.
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