Oosthuizen Nicola, Melo Gabriela D, Seidel George E, Stewart R Lawton, Rowden Larry, Lamb Graham C, Fontes Pedro L P
Department of Animal Science, Texas A&M University, College Station, TX 77843-2471, USA.
Department of Biomedical Sciences, Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins, CO 80523, USA.
Transl Anim Sci. 2021 Apr 7;5(2):txab062. doi: 10.1093/tas/txab062. eCollection 2021 Apr.
To determine effects of delaying the injection of prostaglandin F (PGF) and fixed-time artificial insemination (TAI) in the 14-d CIDR-PG protocol, 1,049 Angus heifers at six locations were enrolled in a completely randomized design. Within location heifers were randomly assigned to one of two treatment groups: 1) PG16 ( = 518), heifers received a controlled internal drug release (CIDR) insert on d 0 for 14 d, a 25-mg injection of PGF 16 d after CIDR removal (d 30), and a 100-µg injection of gonadotropin-releasing hormone concurrent with TAI 66 ± 2 h later; or 2) PG17 ( = 531), heifers were treated the same as PG16, however, PGF was administered 17 d after CIDR removal (d 31), and heifers were TAI 66 ± 2 h later. Estrus detection patches were applied to a subset ( = 482) of heifers at the time of PGF administration and were examined for activation at TAI. Dominant follicle diameter was determined via transrectal ultrasonography at PGF administration and TAI in a subset of heifers ( = 116). Transrectal ultrasonography was performed to determine pregnancy rates to TAI (PR/AI) between 30 and 45 d after TAI. Estrus expression prior to TAI differed by treatment where PG17 heifers had greater ( < 0.01) expression of estrus than PG16 heifers (57.8 ± 6.1% vs. 43.4 ± 6.1%, respectively). Nevertheless, dominant follicle diameters at PGF and at TAI were similar ( ≥ 0.59) between PG16 and PG17 heifers. In addition, PR/AI did not differ ( = 0.29) between PG16 and PG17 treatments (50.5 ± 3.2% vs. 45.7 ± 3.1%, respectively). Results of this experiment indicate that delaying the injection of PGF and TAI in the 14-d CIDR-PG protocol increased estrus expression prior to TAI yet did not improve fertility in beef heifers.
为了确定在14天的CIDR-PG方案中延迟注射前列腺素F（PGF）和定时人工授精（TAI）的效果，六个地点的1049头安格斯小母牛被纳入完全随机设计。在每个地点内，小母牛被随机分配到两个处理组之一：1）PG16（n = 518），小母牛在第0天接受一个可控内部药物释放（CIDR）装置，持续14天，在CIDR取出后16天（第30天）注射25毫克PGF，并在66±2小时后与TAI同时注射100微克促性腺激素释放激素；或2）PG17（n = 531），小母牛的处理与PG16相同，然而，PGF在CIDR取出后17天（第31天）给药，小母牛在66±2小时后接受TAI。在注射PGF时，对一部分（n = 482）小母牛应用发情检测贴片，并在TAI时检查其是否激活。在一部分小母牛（n = 116）中，在注射PGF和TAI时通过经直肠超声检查确定优势卵泡直径。在TAI后30至45天进行经直肠超声检查以确定TAI的妊娠率（PR/AI）。TAI前的发情表现因处理不同而有所差异，其中PG17小母牛的发情表现比PG16小母牛更强烈（P < 0.01）（分别为57.8±6.1%和43.4±6.1%）。然而，PG16和PG17小母牛在注射PGF时和TAI时的优势卵泡直径相似（P≥0.59）。此外，PG16和PG17处理之间的PR/AI没有差异（P = 0.29）（分别为50.5±3.2%和45.7±3.1%）。本实验结果表明，在14天的CIDR-PG方案中延迟注射PGF和TAI可增加TAI前的发情表现，但并未提高肉牛小母牛的繁殖力。
