A performance test of pigs was conducted according to an adapted version of the ‘Kielanowski system’ in which the feeding level and the termination point of the test period were changed. A total of 119 pigs of six genotypes (participants in the Commercial Pig Evaluation in The Netherlands, 1981) averaging 22 kg weight, were fed for 17 weeks on a scheme according to days on test. The regime was such that not all the pigs could consume their total allocation of food. The fast-growing pigs were expected to be more efficient and therefore the leanest.
Forty-eight pigs consumed their total food allocation, whereas the remainder left an average of 5·89 kg food. Pigs that consumed their total allocation of food had a significantly better food conversion ratio (0·07 kg/kg; P < 0·01) and a higher daily gain (33 g/day), but they had significantly less lean (10 g/kg; P < 0·05) in their carcasses than pigs that could not consume their whole allocation. The ranking of genotypes for average daily food intake closely agreed (rs = 0·94) with the ranking in another trial with ad libitum feeding, which points to the possibility for selection on food intake capacity in the proposed system. For the other variates, the ranking correlations were moderate.
Among the pigs that consumed the total amount of food offered, a moderately strong relation (r = 0·70) was found between daily gain and lean tissue growth rate. With the system tested, it was not possible to determine leanness simply by weighing the pigs afterwards. Nevertheless, the results of the modified Kielanowski system show some interesting aspects which contribute to the design of a test system for a genetically unbiased comparison among pigs.