Discipline: Animal Science
Data on mature weight (MWT) and external body measurements [i.e. body length (BL), heart girth (HG), midriff girth (MG), flank girth (FG), withers height (WH), head length (HL), head width (HW)] of 1,315 goats listed in the Philippine Goat Breed Registry were analyzed using a linear mixed model that included the fixed effects of sex (X) and random effects of the sire breed (Sj) dam breed (Dk), and sire breed x dam breed interaction (SDjk).
Estimates of general combining ability (GCA) were highest in the Boer (for MWT, HG, MG, FG, HL, and HW) and Saanen (for BL and WH). The lowest GCA estimates were found in the Native goats for all traits studied. Specific combining ability (SCA) was also computed based on the random interaction effects of the sire and dam breeds used in a specific cross.
The predicted mature weight in the Boer, Saanen, Nubian, and Native goats was 46.8 kg, 44.1 kg, 42.4 kg and 25.1 kg for bucks and 40.2 kg, 37.4 kg, 35.8 kg and 18.4 kg for does, respectively. External body measurements were also found to be significantly greater (P<0.01) in the Boer, Nubian, and Saanen pure breeds compared to the Native stocks. Among the crosses, Nubian x Saanen cross (NUxSA) was heaviest at 36.1 kg and 29.4 kg for bucks and does, respectively. Saanen x Native (SAxNA) goats had the lowest mature weight of 26.3 kg and 19.6 kg for bucks and does, respectively. The mature weights and body measurements in Nubian x Native (NUxNA), high grade Nubian (HGNUB) or 87.5% NUbian-12.5% Native, and Boer x Nubian (BOxNU) were intermediate to the NUxSA and SAxNA crosses.
Average heterosis, defined as the relative superiority of a mating combination over the mid parent values was -4.91%, -1.64%, -2.06%, -1.76%, -1.54%, -1.44%, -2.14%, and -1 .26% for MWT, BL, HG, MG, FG, WH, HL and HW, respectively. The low and negative heterosis values may imply that mature weight and external body measurements are traits strongly influenced by additive gene effects and that their improvement through selection may be a beUer strategy under Philippine conditions. The advantage of crosses over the native stock in terms of mature weight was highest in the HGNUB (49.58%), intermediate in NUxNA (18.79%), and least in SAxNA (5.74%). The advantage over Native goats for external body measurements ranged from 9.24 to 23.98%, 5.10 to 10.49% and -9.10 to 6.28% in the HGNUB, NUxNA and SAxNA crosses, respectively.