Evaluation of crude annual parturition rate estimates in a small-holder African ruminant farming system
Evaluation of crude annual parturition rate estimates in a small-holder African ruminant farming system
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DOI：
10.1017/s1751731109990280
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发表时间：
2009-10-01
期刊：
影响因子：
3.6
通讯作者：
Lancelot, R.
中科院分区：
文献类型：
--
作者：
Lesnoff, M.;Lancelot, R.
已经提出了许多参数来评价热带养殖系统中的家畜繁殖性能。在热带自由放养和小养殖者系统中，如果不进行昂贵的实地调查，就无法单独观察繁殖周期，其中一个参数是如果雌性在种群中度过一整年，则生殖雌性预计的平均分娩次数(H)。一种常用的估计h的方法是使用比率h(C)=m/T，即所谓的年粗分娩率，其中m是观察到的分娩次数，T是生殖雌性在一年中存在的总时间。本文用六种估计方法来估计h，其中T是准确的观察到的存在时间(h(C1))，或用月、季、半年和一年的平均值或生殖群体规模的最终规模(h(C2)到h(C6)来近似)。数据来自对塞内加尔广泛的农牧系统中的牛和小反胃动物群的长期跟踪(数据记录在动物一级)，总体上h由h(C1)正确估计。然而，h(C1)对相互竞争的风险(例如，生殖雌性的死亡、出售和屠宰)很敏感，当雌性在分娩高峰期之前或期间密集撤出时，h(C1)具有严重的偏见。粗率的可靠性从h(C2)到h(C6)逐渐降低，与用于近似i的信息的退化相对应。这种下降对牛(所有方法都具有可接受的可靠性)比对小型反刍动物低得多。在比较的方法中，观察到HC6的可靠性较低，我们不建议将其用于小型反刍动物。方法采用h(C5)和h(C6)两种方法，根据农户对过去12个月中发生的人口统计事件的回顾，进行快速横断面回顾调查。研究表明，这种调查和估计h(C5)和h(C6)会产生严重的偏颇结果。在全球范围内，年度分娩率可能会有很大的变化，这取决于根据短期数据估计的12个月期间，即使有精确的羊群跟踪调查，也必须谨慎地考虑
Many parameters have been proposed for evaluating livestock reproduction performances in tropical farming systems. In tropical free-ranged and small-holder systems, where reproduction cycles cannot be individually observed without expensive field surveys, one of these parameters is the average number of parturitions (h) expected by reproductive female, if the female spends the whole year in the herd. A frequent approach for estimating h is to use the ratio h(c) = m/T so-called 'crude annual parturition rate, where m is the observed number of parturitions and T is the total time of presence of the reproductive females in the herd during the year The bias encountered when h is estimated by hc was evaluated in this paper Six methods of estimation were used, where T was the exact observed time of presence (h(c1)) or approximated by monthly, quarterly, half-yearly and yearly averages or final size of the reproductive herd size (h(c2) to h(c6)). Data came from long-term follow-up of cattle and small-ruminant herds (with data recorded at animal level) in extensive agro-pastoral systems in Senegal, In general h was correctly estimated by h(c1). Nevertheless h(c1) was sensitive to competing risks (e.g. deaths, sales and slaughtering of reproductive females) and was seriously biased when intensive withdrawals of females occurred before or during the parturition peak. Reliability of crude rates progressively decreased from h(c2) to h(c6), corresponding to the degradation of information used for approximating I This decrease was much lower for cattle (for which all methods had acceptable reliability) than for small ruminants. Among the compared methods, the lower reliability was observed for hc6 that we do not recommend for small ruminants. Methods h(c5) and h(c6) are currently used in rapid cross-sectional retrospective surveys based on the recall of the farmers on the demographic events which occurred in the herd over the last past 12 months. The study has showed that such surveys and estimates h(c5) and h(c6) can generate seriously biased results. More globally, annual parturition rates can be highly variable depending on the 12-month periods considered Annual parturition rates estimated on short-term data, even with precise herd follow-up surveys, must be considered cautiously