Jc. Greeff et al., PRELIMINARY GENETIC-PARAMETERS OF GROWTH DURING DIFFERENT GROWTH PHASES IN SHEEP, South African journal of animal science, 23(2), 1993, pp. 57-60
Twenty-four sets of full-sib ram lambs, each born from a different sir
e, were kept individually in pens and hand-reared from birth up to 50
kg live mass. Feed intake and mass of each lamb were determined every
third day. Growth curves [ln(mass) against ln(cumulative feed intake)]
were plotted for each lamb. Three growth phases could be identified.
Very low heritabilities (h2) were calculated for feed conversion ratio
in the second and third phases whereas the h2 in Phase I was 0.32 +/-
0.40. Heritability of average daily gain (ADG), estimated with least
squares means and regression methods, was 0.40 and 0.39 in Phase I, 0.
68 and 0.48 in Phase II, and 0.26 and 0.18 in Phase III. Heritability
of the Kleiber ratio followed the same trend but was generally higher.
Only the product-moment correlations between feed conversion, ADG and
the Kleiber ratio within the same growth phase, differed significantl
y from zero (P < 0.01). Genetic and phenotypic correlations between tr
aits over phases, were low and insignificant.