Abstract
The validity of apparent faecal digestible crude protein and total, apparent faecal or ileal digestible amino acid intakes (lysine, threonine and methionine) as animal performance predictors was evaluated on the basis of digestibility coefficients obtained from the literature and performance and carcass parameter data from five different experiments on growing pigs. Correlations and regression equations were calculated between daily digestible crude protein or amino acid intakes and the performance and carcass parameters of the pigs. No connection was found between digestible crude protein intake and the performance of the pigs. The correlations were highest between different lysine intakes and daily gain (DG) (r = 0.808-0.867, p < 0.001). Ileal digestible lysine intake correlated with the performance of the pigs better than did intakes of total or faecal digestible lysine. The feed conversion ratio (FCR) (p < 0.05), and the thickness of back (BF) (p < 0.001) and side fat (SF) (p < 0.001) correlated highly with ileal digestible lysine intake. The correlations between these parameters and total or faecal digestible lysine intakes were lower but also significant (total lysine: BF p < 0.001, SF p < 0.01 and faecal digestible lysine: BF p < 0.01, SF p < 0.05). The regression equations agreed well with the coefficients of correlation. Ileal digestible lysine intake explained changes of performance and carcass parameters better than did intakes of total and faecal digestible lysine. The study confirms the advantage of using ileal digestibility coefficients of amino acids for detecting differences in the supply of amino acids from different feeds.
Highlights
The practical formulation of swine diets in Finland is usually based on the total supply of essential amino acids and digestible crude protein from dietary ingredients
Linear regression equations were calculated with the REG procedure, using the digestible crude protein or amino acid intakes as independent variables and the different performance and carcass parameters as dependent variables
Partial correlation coefficients were calculated with the CANCORR procedure between the protein or amino acid intakes and the lean in valuable cuts (LVC) or LC in order to eliminate the effect of year from the correlations, because the carcass dissection procedure was changed at the beginning of 1989, resulting in an average 2% increase in carcass lean content
Summary
The practical formulation of swine diets in Finland is usually based on the total supply of essential amino acids (lysine, threonine and sulphur containing amino acids) and digestible crude protein from dietary ingredients. Wide variation is found in the digestibility of protein and amino acids between different feed ingredients determined either at terminal ileum or in faeces (Jdrgensen et al 1984, Sauer and Ozimek 1986, Knabe et al 1989). Comparisons have been made between the ileal and faecal digestibilities of amino acids in different feeds (Jorgensen et al 1984, 1985); the apparent faecal digestibility of amino acids usually gives higher values than does ileal digestibility and may overestimate the amount of amino acids available for protein synthesis. Microbial fermentation and protein synthesis in the large intestine modify the amino acid composition of faeces as compared with the undigested dietary protein residue (Mason 1984)
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