Nitrogen Excretion at Different Stages of Growth and its Association with Production Traits in Growing Pigs

Nitrogen excretion changes substantially during growth, according to new research from a multinational group in Europe. Improvement of feed efficiency was the most effective wy to reduce nitrogen excretion in this trial.
calendar icon 5 July 2012
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The objectives of a study published recently in Journal of Animal Science were to determine nitrogen loss at different stages of growth and during the entire growing period and to investigate the associations between nitrogen excretion and production traits in growing pigs, according to Mahmoud Shirali of SAC in Scotland and co-authors there and at Wageningen University in the Netherlands, The Roslin Institute in Scotland and PIC International Group in Germany.

Data from 315 pigs of an F2 population which originated from crossing Pietrain sires with a commercial dam line were used.

Nitrogen retention was derived from protein retention as measured using the deuterium dilution technique during different stages of growth (60 to 90kg, 90 to 120kg and 120 to 140kg). Pigs were fed ad libitum with two pelleted diets containing 17 per cent (60 to 90kg) and 16.5 per cent (90 to 120 and 120 to 140kg) crude protein.

Average daily nitrogen excretion (ADNE) within each stage of growth was calculated on the basis of the accumulated difference between average daily nitrogen intake (ADNI) and average daily nitrogen retention (ADNR).

Least ADNE, nitrogen excretion per bodyweight gain (NEWG) and total nitrogen excretion (TNE) were observed during growth from 60 to 90kg. In contrast, the greatest ADNE, NEWG and TNE were found during growth from 120 to 140kg.

Statistical analyses indicated that gender, housing type, the ryanodine receptor 1 (RYR1) gene and batch influenced nitrogen excretion (P<0.05) but the degree and direction of influences differed between growth stages.

Gender differences showed that gilts excreted less nitrogen than barrows (P<0.05), which was associated with decreased feed conversion ratio (FCR; feed:gain) and lipid:protein gain ratio.

Single-housed pigs showed reduced nitrogen excretion than group–housed pigs (P<0.05).

In comparison to other genotypes, pigs carrying genotype NN (homozygous normal) at the RYR1 locus had the least nitrogen excretion (P<0.05) at all stages of growth except from 60 to 90kg.

The residual correlations indicated that NEWG and TNE have large positive correlations with feed conversion ratio (r=0.99 and 0.91, respectively) and moderate negative correlations with average daily gain (r=-0.53 and -0.48, respectively), for the entire growing period.

Improvement in feed conversion ratio, increase in average daily gain and reduction in lipid:protein gain ratio by one phenotypic SD reduced TNE per pig by 709g, 307g and 211 g, respectively, over the entire growing period.

Shirali and co-authors conclude from their results that nitrogen excretion changes substantially during growth, and it can be reduced most effectively by improvement of feed efficiency and, to a lesser extent, through the improvement of bodyweight gain or body composition or both.


Shirali M., A. Doeschl-Wilson, P.W. Knap, C. Duthie, E. Kanis, J.A.M. van Arendonk and R. Roehe. 2012. Nitrogen excretion at different stages of growth and its association with production traits in growing pigs. J. Anim. Sci., 90(6):1756-1765. doi: 10.2527/jas.2011-4547

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June 2012
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