Kelley D E, Ibarbia L, Daetz R, Bittar J H, Risco C A, Santos J E P, Ribeiro E S, Galvão K N
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA.
Department of Animal Sciences, College of Agricultural and Life Sciences, University of Florida, Gainesville, Florida, USA.
Theriogenology. 2016 Jan 15;85(2):230-7. doi: 10.1016/j.theriogenology.2015.09.052. Epub 2015 Oct 8.
The objective was to decrease the reinsemination interval (RI) when dairy cows and heifers are inseminated using all timed artificial insemination (TAI) programs. Holstein cows (n = 211) and heifers (n = 153) were randomly assigned to a control or 21-day Resynch (21dRES) at 13 days after TAI. Animals in 21dRES (n = 109 cows and 77 heifers) had a progesterone device inserted on Day 13 and removed on Day 20 after TAI and ovaries scanned by ultrasonography. Animals found not to have an active CL (<15 mm) or a CL that decreased 10 mm or greater from Days 13 to 20, and to have a follicle of 12 mm or greater received GnRH and TAI on Day 21. Pregnancy diagnosis was performed on Day 32. Nonpregnant control cows (n = 102) were resynchronized immediately using Ovsynch-56, and control heifers (n = 76) were resynchronized using 5-day Cosynch starting on Day 34; therefore, cows and heifers were reinseminated on Day 42. Nonpregnant 21dRES animals that had not been reinseminated on Day 21 were resynchronized concurrently with the control animals. Pregnancy per AI (PAI) for the initial TAI was similar (P = 0.80) for 21dRES and control cows (30.3% vs. 29.4%) and heifers (49.4% vs. 51.3%). Of the nonpregnant 21dRES animals, 33 of 76 cows (43.4%) and 22 of 39 heifers (56.4%) had been reinseminated on Day 21. Therefore, the RI was decreased by 9.9 days (33.3 ± 1.0 vs. 43.2 ± 1.0 days; P < 0.001) in 21dRES cows and by 12.2 days in 21dRES heifers (30.1 ± 1.3 vs. 42.3 ± 1.3 days; P < 0.001) compared with controls. The overall resynchronized PAI was similar for 21dRES cows compared with controls (31.6% vs. 25.0%; P = 0.23). The PAI was 24.2% for 21dRES cows reinseminated on Day 21 and 37.2% for 21dRES cows reinseminated on Day 42. The overall resynchronized PAI was increased for 21dRES heifers compared with controls (57.5% vs. 32.4%; P = 0.03) because 21dRES heifers reinseminated on Day 21 had similar PAI compared with controls (43.5% vs. 32.4%; P = 0.39), but PAI was increased for 21dRES heifers reinseminated on Day 42 compared with controls (76.5% vs. 32.4%; P = 0.003). Consequently, the proportion of animals pregnant from the initial and resynchronized TAI tended to be increased in 21dRES heifers (79.0% vs. 67.1%; P = 0.09). Cost per pregnancy was decreased for the 21dRES in heifers. In conclusion, 21dRES provided a useful method to decrease the RI in cows and heifers, and to increase PAI and decrease cost per pregnancy in heifers.
目的是在奶牛和小母牛采用所有定时人工授精（TAI）程序进行授精时，缩短再输精间隔（RI）。荷斯坦奶牛（n = 211）和小母牛（n = 153）在TAI后13天被随机分配至对照组或21天再同步化处理组（21dRES）。21dRES组的动物（n = 109头奶牛和77头小母牛）在TAI后的第13天插入孕酮装置，并于第20天取出，然后通过超声扫描卵巢。发现没有活性黄体（<15 mm）或黄体在第13天至第20天缩小10 mm或更多，且有一个12 mm或更大卵泡的动物，在第21天接受促性腺激素释放激素（GnRH）和TAI。在第32天进行妊娠诊断。未怀孕的对照组奶牛（n = 102）立即使用Ovsynch - 56进行再同步化处理，对照组小母牛（n = 76）从第34天开始使用5天的Cosynch进行再同步化处理；因此，奶牛和小母牛在第42天进行再输精。在第21天未进行再输精的未怀孕21dRES组动物与对照组动物同时进行再同步化处理。21dRES组和对照组奶牛（30.3%对29.4%）以及小母牛（49.4%对51.3%）初始TAI的每人工授精妊娠率（PAI）相似（P = 0.80）。在未怀孕的21dRES组动物中，76头奶牛中有33头（43.4%）和39头小母牛中有22头（56.4%）在第21天进行了再输精。因此与对照组相比，21dRES组奶牛的RI缩短了9.9天（33.3±1.0天对43.2±1.0天；P < 0.001），21dRES组小母牛的RI缩短了12.2天（30.1±1.
