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A study of protein and amino nutrition of growing pigs.
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2004-08-01
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Lynch, P.B., O'Connell, M.K., Lawlor, P.G., O'Doherty, J.V., A study of protein and amino nutrition of growing pigs, End of Project Report, Tegasc, 2004.
Abstract
Protein nutrition of the pig is concerned primarily with supplying the amino acid
requirements for fast, efficient growth and development of a lean carcass. In addition,
surplus protein contributes to a high level of nitrogen excretion in manure which is a
problem in complying with the Nitrates Directive. Metabolism of the excess protein /
nitrogen in the pig involves creation of urea and this process depresses the efficiency of
energy utilisation. As the pig grows, its requirement for individual amino acids falls but
the optimum ratio changes. Providing a diet with the correct levels and balance of the
principal amino acids is expected to improve performance.
Improvements in genetics and changes in management such as slaughter weight require
that the amino acid requirements be reassessed periodically. The objective of this study
was to examine response of pigs to variation in dietary lysine in several weight ranges
with the concentrations of the other principal amino acids held constant.
Entire males had superior FCR to females in all trials except 15 to 30kg, but differences
in dietary lysine requirements did not occur until the finishing stage. At heavier
weights, response of male and female pigs began to diverge at lysine concentrations
greater than 10.7 g/kg (ADG) and 9.7 g/kg (FCR).
There appeared to be a need to increase the threonine to lysine ratio in the diet from
0.60 to 0.70 when lysine concentration was reduced from 12.0 to 9.5 g/kg as weight of
the pig increased.
Providing the same mean lysine content (11.1 g/kg) to pigs from 38 to 97 kg in a series
of five diets declining in lysine concentration compared with a single diet did not affect
performance, or reduce N excretion. However, lowering the overall mean lysine
concentration from 11g/kg to 10.0 g/kg reduced overall N excretion by 13 %, without a
negative effect on pig performance. Pigs which were offered a low lysine diet in the
early stage of growth exhibited a compensatory response during realimentation on a
high lysine diet but it was not sufficient to equal the overall performance of pigs
previously offered a lysine-adequate diet. Nitrogen excretion was reduced by 23 % while the low lysine diet was fed in the initial period but there was no residual effect on
N excretion during realimentation.