Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, and.
J Dairy Sci. 2013;96(12):7630-9. doi: 10.3168/jds.2013-6723. Epub 2013 Oct 4.
An important part of reproductive management programs on dairy farms is identification of nonpregnant cows and early re-insemination to achieve higher pregnancy rates. The objective of this study was to compare the effect on reproductive performance and pregnancy loss of 2 pregnancy diagnosis protocols: (1) pregnancy diagnosis performed 31±3 d after artificial insemination (AI) by ultrasonography (ULTRA), and (2) resynchronization started 31±3 d after AI but with pregnancy diagnosis performed 38±3 d after AI by palpation per rectum (PALP). Cows were randomly allocated into 1 of the 2 management programs. For cows enrolled in ULTRA, the initial pregnancy diagnosis (P1) was performed by transrectal ultrasonography at 31±3 d after AI, and nonpregnant cows were enrolled in the Ovsynch protocol for resynchronization of ovulation to receive timed AI (TAI). For cows enrolled in PALP, the Ovsynch protocol for resynchronization of ovulation to receive TAI was initiated at 31±3 d after AI regardless of pregnancy status, with the initial pregnancy diagnosis (P1) performed by palpation per rectum at 38±3 d after AI. For both groups, reconfirmation of pregnancy was performed by palpation per rectum at 63±3 d after AI (P2). Cows were inseminated after detection of estrus by use of activity monitors at any time during the study. Two levels of activity were used as a reference for cows AI after detection of estrus based on activity: an activity level of ≥2 when a cow was coded in DairyComp 305 (Valley Agricultural Software, Tulare, CA) as open (nonpregnant) and an activity level of ≥3 when the pregnancy status of the cow was unknown. Our findings showed that the odds of pregnancy loss cows in ULTRA was 2 times higher between P1 and P2 compared with that of cows in PALP. Furthermore, pregnancy diagnosis method (ULTRA vs. PALP) did not have a significant effect on the Cox proportional hazard of pregnancy at P2. The occurrence of assisted parturition, metritis, or retained placenta was associated with a reduced hazard of pregnancy at P2. An economic analysis was performed by simulating a 1,000-cow commercial dairy herd using a decision support tool to estimate the net present value (NPV; $/cow per yr) from using the 2 different pregnancy diagnosis methods. The analysis revealed minor differences in NPV between the programs, depending on the cost to perform ULTRA or PALP. In summary, we observed no difference in the reproductive performance and only a minor and fluctuating economic difference when using either PALP or ULTRA for pregnancy diagnosis of dairy cows.
奶牛场繁殖管理计划的一个重要部分是鉴定未怀孕的奶牛，并进行早期再配种，以提高受胎率。本研究的目的是比较 2 种妊娠诊断方案对繁殖性能和妊娠损失的影响：（1）人工授精（AI）后 31±3 d 通过超声（ULTRA）进行妊娠诊断，（2）AI 后 31±3 d 开始同步发情，但通过直肠触诊（PALP）在 AI 后 38±3 d 进行妊娠诊断。奶牛被随机分配到 2 种管理方案之一。对于接受 ULTRA 的奶牛，初始妊娠诊断（P1）在 AI 后 31±3 d 通过直肠超声进行，如果未怀孕，则将其纳入 Ovsynch 方案进行排卵同步，以接受定时人工授精（TAI）。对于接受 PALP 的奶牛，无论妊娠状况如何，在 AI 后 31±3 d 开始 Ovsynch 方案进行排卵同步，并在 AI 后 38±3 d 通过直肠触诊进行初始妊娠诊断（P1）。对于两组，在 AI 后 63±3 d 通过直肠触诊进行妊娠再确认（P2）。在研究期间的任何时间，通过活动监测器检测到发情后，奶牛即可进行配种。基于活动，使用 2 个活动水平作为奶牛发情后 AI 的参考：当奶牛在 DairyComp 305（Valley Agricultural Software，Tulare，CA）中被编码为开放（未怀孕）时，活动水平为≥2，当奶牛的妊娠状况未知时，活动水平为≥3。我们的研究结果表明，与 PALP 组相比，ULTRA 组在 P1 和 P2 之间的妊娠损失牛的怀孕几率高 2 倍。此外，妊娠诊断方法（ULTRA 与 PALP）对 P2 时的妊娠 Cox 比例风险没有显著影响。助产分娩、子宫内膜炎或胎衣滞留的发生与 P2 时妊娠的风险降低有关。通过使用决策支持工具模拟 1000 头商业奶牛场进行经济分析，以估计使用两种不同妊娠诊断方法的净现值（NPV；每头奶牛每年的美元）。分析结果表明，这两个方案之间的 NPV 差异很小，这取决于进行 ULTRA 或 PALP 的成本。总之，当使用 PALP 或 ULTRA 对奶牛进行妊娠诊断时，我们观察到繁殖性能没有差异，只有微小且波动的经济差异。
