GROWTH AND FEEDING CHARACTERISTICS OF THREE BREEDS OF SWINE AND THEIR CROSSES

Abstract

Data from 200 hogs, representing all possible two-breed and purebreed crosses of Minnesota No. 1 (M), Pietrain (P), and Yorkshire (Y) breeds and two sexes, barrows (1) and gilts (2), were recorded following slaughter at four developmental stages (22.5 kg, 45.0 kg, 67.5 kg, and 90.0 kg liveweight). The objectives were to examine: (a) breed and sex effects on allometric growth coefficients (AGC) and lean tissue growth rates (LTGR); (b) breed differences for feed efficiency on a live animal basis (GF) and lean tissue basis (LTGF); (c) heterosis and differences between reciprocal crosses for these traits; and (d) the relationship between live animal growth rate and LTGR. Breed differences were: P × P(2) < [M × M(1,2) = P × P(1) = Y × Y(1,2)] for AGC and (P = Y)> M for LTGR, GF, and LTGF. Differences (P < 0.05) between barrows and gilts were found in the P × P and Y × P crosses for AGC but none were found for LTGR. Heterosis estimates for LTGR increased in magnitude with stage of development, but were stable when expressed on a percent basis, and differences between reciprocal crosses remained constant. Heterosis estimates were found to be significant (P < 0.05) for AGC and GF but not for LTGR. Significant (P < 0.05) differences between reciprocal crosses were reported for GF and LTGF but not for AGC. Live animal growth rate was found to be a good predictor of LTGR with R2 ranging from 0.65 to 0.84. Key words: Allometric growth coefficients, feed efficiency, breed differences, heterosis, reciprocal differences, swine