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Lysine, Crude Protein Nutrition for Finishing Pigs

by 5m Editor
1 March 2011, at 11:04am

NORTHERN IRELAND, UK - Feed costs may be reduced by lowering dietary crude protein (CP) content but it is essential that the “ideal protein“ content of a diet is maintained and this requires supplementation with expensive amino acids. It is also crucial to ensure that sufficient CP is supplied to drive efficient growth, writes Elizabeth Ball.


Elizabeth Ball investigates optimum lysine and protein levels in diets for finishing pigs.

“Ideal protein“ is the provision of essential amino acids in exactly the proportions required by the pig and as lysine is the most limiting amino acid in pig diets, other amino acids are supplied in proportion to lysine. Previous work at AFBI Hillsborough has established that pigs between 30-40 kg require at least 0.98 per cent total lysine but more research is needed to define the lysine requirements of older pigs. Reducing the CP and lysine content (and subsequently the content of other amino acids) has the potential to lower feed costs and reduce nitrogen excretion to the environment. However, this is not a sustainable practice if pig performance is adversely affected. Therefore, the aim of this research was to examine the effect of offering diets differing in lysine and CP content on the performance of finishing pigs.

The work was conducted at AFBI Hillsborough using the unique AFBI/PCM (Preferred Capital Management) research facility. There were four experimental dietary regimes offered to pigs from approximately 40-118 kg:

0 40 - 80 kg 80 kg - Finish
Regime 1 Diet 1 (18% CP and 1.1% lysine) Diet 1 (18% CP and 1.1% lysine)
Regime 2 Diet 1 (18% CP and 1.1% lysine) Diet 2 (16.7% CP and 0.8% lysine)
Regime 3 Diet 3 (18% CP and 0.95% lysine) Diet 3 (18% CP and 0.95% lysine)
Regime 4 Diet 3 (18% CP and 0.95% lysine) Diet 2 (16.7% CP and 0.8% lysine)

Results and conclusions:

  • There was no difference in the performance of pigs between 40 and 80 kg when they were offered diets with either 1.1 per cent or 0.95 per cent lysine.
  • A diet containing 0.8 per cent lysine and 16.7 per cent CP was adequate to maintain performance of pigs from 80 kg to finish. However, it must be noted that feed intake of these pigs was higher than that of pigs offered the diets containing 1.1 per cent or 0.95 per cent lysine and 18 per cent CP.
  • A two-stage dietary regime (0.95 per cent lysine → 0.8 per cent lysine) can be offered to pigs from 40 kg to finish without any reduction in performance.
  • The two-stage dietary regime would reduce feed costs but the cost of capital investment to operate the two-stage regime needs to be considered.