Ma. Faust et al., GENETIC AND ECONOMIC-ANALYSES OF SOW REPLACEMENT RATES IN THE COMMERCIAL TIER OF A HIERARCHICAL SWINE BREEDING STRUCTURE, Journal of animal science, 71(6), 1993, pp. 1400-1406
Commercial-level sow replacement rates were investigated for a 10-yr p
lanning horizon using a stochastic life-cycle swine production model.
A three-tiered breeding structure was modeled for the production of ma
rket hogs in a three-breed static crossing scheme. Growth and reproduc
tive traits of individual pigs were simulated using genetic, environme
ntal, and economic parameters. Culling was after a maximum of 1, 5, or
10 parities in commercial levels within 1- and 5-parity nucleus and 1
-, 5-, and 10-parity multiplier combinations. Yearly changes and avera
ge phenotypic levels were computed for pig and sow performance and eco
nomic measures. For growth traits, greater commercial level response w
as for systems with higher sow replacement rates, 110 to 115% of lowes
t response. Phenotypic changes in net returns ranged from $.85 to 1.01
-pig-1-yr-1. Average growth performances were highest for systems with
greatest genetic trend. Highest kilograms-sow-1-year-1 finished was f
or 10-parity commercial alternatives. System differences in total cost
s and returns per pig resulted primarily from differences in replaceme
nt costs. Removal of the gilt system from analyses often reduced range
s among systems for economic measures by more than 70%. Systems with t
he lowest commercial replacement rates were most profitable. Within th
ese systems, those with higher genetic change had highest net returns.
For high replacement rates, no more than 175% of market value could b
e paid for gilts, but with lower sow replacement rates commercial unit
s could justify as much as 450%.