Growth curves of pigs from six genetic lines were estimated linearly (making use of on-test and off-test weights at ca 35 and 93 kg, respectively) and curvilinearly (making use of these and midtest weights at ca 63 kg). The degree of curvilinearity (D E V N % ) was quantified as the difference between actual mid-test weight and its linear prediction, expressed as a percentage of the latter. D E V N % showed line means from -5 to -2 % , with within-line standard deviations from 9 to 11 % . In the fastest-growing three lines, D E V N % showed h2 values (estimated with a sire-dam model) close to zero while the h2 of linear daily gain (LDG) ranged from 0 .1 3 to 0.21; in the slower-growing three lines, h2 values of LDG and D E V N % were of the same magnitude, ranging from 0.13 to 0.26 and from 0.1 6 to 0.35, respectively. Mean metabolic body weights MBW over the growth trajectory as estimated from on-test and off-test weight only and from these plus midtest weight showed within-line correlation coefficients of ca 0.93. It is concluded that the degree of curvilinearity of the growth curve is a heritable trait in some of the lines. This has implications for the w ay M B W has to be accommodated in selection criteria that attempt to aim for net feed efficiency.

P. W Knap, H. AM van der Steen

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 19. Selection and quantitative genetics; growth; reproduction; lactation; fish; fiber; meat., , 193–196, 1994
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