Table 3. Conception rates of Holstein heifers and cows receiving in vitro-produced Japanese Black embryos 7 to 9 days after natural estrus, categorized by month.
| Month of embryo transfer | Heifers |
Cows |
All |
||||||
|---|---|---|---|---|---|---|---|---|---|
| n | LSM (%) | SDEM (%) | n | LSM (%) | SDEM (%) | n | LSM (%) | SDEM (%) | |
| January | 90 | 53.4 | 5.5 | 170 | 28.1 | 3.6 | 260 | 40.0 | 3.4 |
| February | 110 | 44.8 | 5.0 | 245 | 32.6 | 3.1 | 355 | 38.4 | 2.9 |
| March | 124 | 52.9 | 4.7 | 232 | 36.0 a | 3.3 | 356 | 44.3 | 2.9 |
| April | 140 | 55.9 | 4.4 | 278 | 35.7 a | 3.0 | 418 | 45.4 a | 2.7 |
| May | 104 | 53.8 | 5.1 | 221 | 35.5 | 3.4 | 325 | 44.1 | 3.1 |
| June | 84 | 55.3 | 5.7 | 206 | 38.3 a | 3.5 | 290 | 46.4 a | 3.4 |
| July | 100 | 44.9 | 5.2 | 218 | 21.5 b | 2.9 | 318 | 31.9 b | 2.9 |
| August | 141 | 53.8 | 4.4 | 322 | 34.1 | 2.8 | 463 | 43.4 | 2.6 |
| September | 115 | 47.5 | 4.9 | 311 | 38.1 a | 2.9 | 426 | 42.5 | 2.8 |
| October | 143 | 58.9 | 4.3 | 331 | 40.3 a | 2.8 | 474 | 49.4 a | 2.7 |
| November | 134 | 48.9 | 4.5 | 346 | 34.5 | 2.7 | 480 | 41.5 | 2.6 |
| December | 122 | 51.8 | 4.8 | 309 | 39.2 a | 2.9 | 431 | 45.3 a | 2.8 |
Conception rates are expressed as LSM ± standard error derived from GLIMMIX analysis. LSM, least-squares mean; SDEM, standard error of mean; reported using the SAS GLIMMIX procedure. a, b P < 0.05 within the same column.