Abstract
We predicted the potential profitability increase of Japanese Black cattle (Wagyu) at cow-calf fattening farms by the use of planned mating, based on DNA testing of QTL alleles, to increase Beef Marbling Standards (BMS) scores and carcass weight (CW). The following assumptions and scenarios were adopted. (1) Q (excellent) to q (ordinary) allele additive substitution effect : 1.0 for BMS score (ΔBMSQTL) and 20 kg for CW (ΔCWQTL). (2) A rise of \150/kg in dressed carcass price when the BMS score increases by 1 (ΔCWPBMS). (3) CW = 440 kg (CW). (4) Price of CW (CWPU) : \1,900/kg. (5) The DNA typed sires (QQ type) were used to breed dams (Hardy-Weinberg population). (6) The age at first calving and the productive lifetime of dams (N : number of dams) were 3 and 8 (or 9) years, respectively. (7) The replacement rate for cows was ⅙N. Calves not for replacement (⅚N) and cows over 8 (or 9) years (⅙N) were moved for fattening and slaughter. (8) The planned time horizon (T) was 15 years. (9) Priority sequence of dams for slaughter : qq→Qq→QQ. (10) Frequency of the Q allele in the population = 0.1, 0.3, 0.5, 0.7, 0.9. [Scenario 1] : Sires were known for DNA type (QQ) : CTYP = \0, SEM ≥ \0. [Scenario 2] : Sires were DNA typed and selected (QQ) : CTYP > \0, SEM ≥ \0. [Scenario 3] : Dams were DNA typed, CTYP > \0 and sires were known for QQ type : CTYP = \0, SEM ≥ \0. To increase profitability, the Q allele frequency in population, SEM, and the number of T are more important than CTYP and R (s/d). The Q allele frequency is required to be less than 0.6∼0.7 for the BMS score and less than 0.4∼0.5 for CW in order to retain around \10,000 of ΔVind on the condition that the cost of DNA diagnosis, including patent fees, is \5,000/head or less and that the semen price difference is \10,000/head or less. In addition, it is more effective to use planned mating for dams and sires (Scenario 3) than those of sires (Scenarios 1 & 2) based on information on QTL alleles if the Q allele frequency for the BMS score is in the range of 0.5∼0.7 at over 6 year (T) or if it is over 8 year (T) for CW to retain around \10,000 of ΔVind.
