在巴西牛犊系统中推荐的产卵和开始固定时间人工授精(FTAI)协议之间的最短间隔为30d,基于Bostaurus女性子宫复旧特征和子宫疾病发生率的研究。Nelore的子宫疾病,如亚临床子宫内膜炎的患病率有限(B.indicus)奶牛早在产牛后28d。我们假设Nelore奶牛最早可以在产后20d(DPP)接受FTAI协议,并且仍然可以获得令人满意的繁殖结果。这项研究在FTAI方案开始时根据DPP评估了5,258头Nelore母牛(n=1,703头初产和3,555头多产)的妊娠率。在FTAI记录奶牛身体状况评分(BCS),FTAI后~30d进行妊娠诊断。在FTAI协议启动时,按DPP对奶牛进行等值排名,并根据5d间隔进行分类(例如,≤15DPP,16到20DPP,21到26DPP,直到牛的DPP≥76)。数据在奇偶校验内进行了分析,以奶牛为实验单位和正交多项式对比(线性,二次,或立方)使用每个DPP类的平均DPP生成。在两个议会中,FTAI的奶牛BCS随着DPP的推进而线性下降(P≤0.01)(例如,初产妇4.79、4.00和3.73,在分类为≤15DPP的多胎母牛中,分别为4.95、3.70和3.23,36到40DPP,≥76DPP,分别)。FTAI的妊娠率受到DPP的二次影响(P<0.01)。在初产母牛中,怀孕率增加到36到40DPP(60%),保持在这个水平附近,直到51到60民进党,然后随着民进党的推进而减少,而分类为21至25DPP的母牛表示令人满意的结果(41.5%)。在多胎母牛中,怀孕率增加到46到50DPP(70.8%),保持在这个水平附近,直到56到60DPP,然后随着民进党的推进而减少,而分类为21至25DPP的母牛也表达了令人满意的结果(63.6%)。总的来说,当FTAI方案在30至60DPP内启动时,本文评估的初产和多胎Nelore母牛经历了最佳怀孕率,尽管早在21DPP启动FTAI方案时观察到了合理的结果.因此,在Nelore雌性中,产卵和开始FTAI方案之间的间隔可以缩短10d,并且仍然可以获得可接受的妊娠率,这对在每年繁殖季节之前或期间产牛的奶牛具有重要价值。
The shortest interval between calving and initiation of fixed-time artificial insemination (FTAI) protocols recommended in Brazilian cow-calf systems is 30 d, based on research that characterized uterine involution and incidence of uterine disorders in Bos taurus females. Prevalence of uterine disorders such as subclinical endometritis is limited in Nelore (B. indicus) cows as early as 28 d after calving. We hypothesized that Nelore cows can receive an FTAI protocol as early as 20 d postpartum (DPP) and still experience satisfactory reproductive results. This study evaluated pregnancy rates in 5,258 Nelore cows (n = 1,703 primiparous and 3,555 multiparous) according to DPP at the initiation of the FTAI protocol. Cow body condition score (BCS) was recorded at FTAI, and pregnancy diagnosis was performed ~30 d after FTAI. Cows were ranked within parity by DPP at the initiation of the FTAI protocol and classified according to 5-d intervals (e.g., ≤15 DPP, 16 to 20 DPP, 21 to 26 DPP, until cows with ≥76 DPP). Data were analyzed within parity, using cow as experimental unit and orthogonal polynomial contrasts (linear, quadratic, or cubic) generated using the mean DPP of each DPP class. In both parities, cow BCS at FTAI decreased linearly (P ≤ 0.01) with the advance of DPP (e.g., 4.79, 4.00, and 3.73 in primiparous, and 4.95, 3.70, and 3.23 in multiparous cows classified as ≤15 DPP, 36 to 40 DPP, ≥76 DPP, respectively). The pregnancy rate to FTAI was affected quadratically (P < 0.01) by DPP for both parities. In primiparous cows, the pregnancy rate increased until 36 to 40 DPP (60%), remained near this level until 51 to 60 DPP, and then decreased with the advance of DPP, whereas cows classified as 21 to 25 DPP expressed satisfactory results (41.5%). In multiparous cows, the pregnancy rate increased until 46 to 50 DPP (70.8%), remained near this level until 56 to 60 DPP, and then decreased with the advance of DPP, whereas cows classified as 21 to 25 DPP also expressed satisfactory results (63.6%). Collectively, primiparous and multiparous Nelore cows evaluated herein experienced optimal pregnancy rates when the FTAI protocol was initiated within 30 to 60 DPP, although reasonable outcomes were observed when the FTAI protocol was initiated as early as 21 DPP. Hence, the interval between calving and initiation of the FTAI protocol can be shortened by 10 d in Nelore females and still yield acceptable pregnancy rates, which can be of great value to cows that calve immediately prior to or during the annual breeding season.