繁育工作中的查情公猪

　　尽管养猪业已广泛采用人工授精技术，猪场里仍然会使用“诱情公猪”。他们的作用是帮助决定何时给母猪进行人工授精。事实上，公猪可以刺激发情母猪的一种特异性的性行为反应，提示母猪已经准备好配种。这个时间段被称为发情期。公猪气味在发情检测中的重要性早在60年代就已被人们所认识，事实证明，公猪气味所带来的嗅觉刺激是提高发情期雌性动物背压试验中发情检测率的关键因素(Signoret,1975)。而触发发情期雌性动物的性行为，传递公猪发出的性信息的分子被称为信息素。

公猪唾液中第三种信息素的最新发现

　　雄烯酮是Patterson在1968年发现的，是第一种被发现的公猪信息素。该物质是从性成熟公猪的脂肪中分离出来的，因为这种化合物在同年龄的阉公猪和母猪中不存在，这与公猪肉特有的腥味有关。雄烯酮及其代谢衍生物雄烯醇被证实是由颌下腺释放到公猪唾液中的，因为它们在交配行为过程中会发出特有的气味。Melrose(1971)和Reed(1974)最终证实了这些分子作为信号传递信息素的潜力，证明了这些分子可以促进发情期雌性动物的静立反射。最近，美国得克萨斯理工大学的科学家对公猪和母猪唾液中的嗅觉分子进行了广泛的化学研究，发现公猪唾液中有3种独特的分子：除雄烯酮和雄烯醇外，还有喹啉。McGlone等人(2019年)证实，与单一或二元公猪特异性信息素溶液相比，使用雄烯酮、雄烯酮和喹啉3个分子制备的喷雾是诱导背压试验产生最大性行为反应的最有效的溶液。三分子缔合能有效地增加静立反射，这被认为是发情监测的金标准。喹啉对刺激第二类性行为，如耳朵竖立和兴奋的叫声等，具有重要作用。这项工作证实了公猪信息素是雄烯酮、雄烯醇和喹啉的标志性混合物，其中每种化合物都会引起部分行为反应，但这种混合物会引起协同行为反应。

三分子公猪信息素喷雾剂的实际应用

　　我们最近设计了一个实验来比较三分子公猪信息素喷雾剂在商业条件下对断奶母猪繁殖性能的影响。一组使用公猪信息素配合播放公猪叫声来刺激母猪，另一组使用一头成熟公猪进行发情检测。三分子公猪信息素组与公猪组的排卵母猪发情率基本相同，略有差异，这与早期文献报道的公猪的气味和声音触发发情母猪静立反射的功效一致(Signoret 1970)。信息素组的发情检测率略低的原因是由于缺乏视觉刺激和触觉刺激所致。此外，得益于不间断的B超诊断，我们能够评估每头母猪排卵的准确时间。然后我们可以证实大多数的授精发生在排卵前24小时内，这被认为是最好的授精窗口。两组的授精时间没有差异。这些观察结果与两组的生育率和多产率结果相关，产仔率为93%，总产仔数为15。

三分子公猪信息素提高抵御ASF的生物安全性

　　在非洲猪瘟肆虐之际，实施生物安全措施从未如此重要，事实证明，三分子公猪信息素在很大程度上有效地控制了ASF在中国的传播。在农场一级，减少将ASF病毒引入畜群风险的最重要干预措施之一是避免从不安全的来源购买动物。事实上，购买的动物可能是ASF病毒携带者，并且是农场暴发的源头。最近出现的ASF病毒新毒株导致非洲猪瘟的慢性症状，更可能影响母猪繁殖性能，使得检测更加复杂，并在全球范围内影响对购买动物质量的信任。在这种情况下，购买公猪进行发情检测是将ASF带到农场的风险。此外，诱情公猪需要与母猪通过鼻对鼻的接触传递信息素，并有效的刺激发情，因此造成诱情公猪迅速传播ASF病毒的风险。而且该途径是传播ASF病毒最早和最有效的途径之一，同时也使公猪在农场成为ASF病毒高效传染源。在这种情况下，公猪信息素可被视为一种替代购买的公猪进行发情检测的生物安全工具，从而隔绝了将ASF病毒带到农场的风险。与内部培养更新诱情公猪相比，该解决方案在养殖场更易实施，自养公猪淘汰率更高，且至少10个月才能合格投入使用。

三分子公猪信息素，提高发情母猪检出率

　　2021年初，有一项针对中国客户的关于母猪查情的调查。超过100位顾客参与了这项调查。毫不奇怪，当农场有公猪存在时，发情检测并没有被认为是一个主要的挑战。共有95%的受访者认为发情检测并不困难，因为他们认为母猪有明显的行为特征。然而，当与他们谈及后备及头胎，二胎猪等青年母猪，是否与多胎次母猪一样容易鉴别时，82%的人承认青年母猪确实存在问题。疑似发情或发情不明显对生产力的影响是众所周知的，96%的人同意疑似发情或发情不明显会在一定程度上导致错过母猪发情期，98%的人同意发情期更清晰的开始点有助于确定第一次人工授精的时机。换言之，在青年母猪中，很难观察到明显的发情迹象，这影响了我们中国客户的人工授精计划的成功。

　　在欧洲，拥有良好繁殖成绩的农户甚至顶级猪场都报告说，它们在配种过程中遇到了类似的障碍。我们已经报道了与后备和头胎母猪发情有关的病例。目前，有报道称，喷洒这种三分子公猪信息素，并结合公猪以及标准模拟技术进行发情检测，可以有效地最大限度地提高发情检测的能力，对不同遗传背景的青年母猪有明显的益处。特别是对后备母猪来说，最大限度地进行发情检测是一个特别重要的问题，因为它验证了母猪的情期状态。这可能会对农场的经济效益产生严重影响，因为它可以防止因错误地认为后备猪处于乏情状态而淘汰的发生。

三分子公猪信息素提高繁殖成绩

　　此外，三分子公猪信息素喷雾剂不仅有助于了解母猪是否处于发情，是否需要人工授精，而且还有助于改善母猪授精的时机。在这里，改进的发情检测程序将提供一个更好的指示，何时进行授精。这可能会提高全球农场授精的成功率。背后的原因很简单:准确得测定母猪发情启动时间，可以帮助每个农场有更多的信心来发展和执行一个标准的配种计划。它特别降低了育种者过早授精的风险，从而确保妊娠率，并可能有助于在最佳时机进行授精，以改善产仔数。有趣的是，McGlone等人(2019年)报告了一项实验的结果，该实验将使用三分子公猪信息素结合公猪刺激的母猪的繁殖性能与在美国商业条件下仅使用公猪查情的母猪的繁殖性能进行了比较。涵盖大约4000头母猪分布在12个商业农场中，存栏从大约450头到6000头母猪不等。在发情检测期间，三分子公猪信息素提供了最大化的性刺激，可使受胎率提高3%，产仔数增加0.46头。有趣的是，研究人员注意到，头三胎母猪的幼崽数量增加了0.88头。这些结果证实了三分子公猪信息素喷雾剂对繁殖性能的促进作用。

结论

　　综上所述，最新研究发现在公猪唾液中一种叫做喹啉的新分子的存在。这种分子已被证明对发情期雌性动物中表现出性信息素效应，并与公猪唾液中已知的其他信息素起协同作用。在没有查情公猪的情况下，三分子公猪信息素喷雾剂用于发情检测和成功授精的功效是我们对配种工作重新思考定位的一个机会，特别是当畜群健康管理方案需要减少对公猪的依赖性时。在正常的配种工作中，用三分子公猪信息素喷雾剂在公猪刺激的基础上最大限度地提高发情检测率，还可以通过提供及时的发情鉴定的机会来提高母猪的繁殖性能，并在更好的时间内进行配种。

Why a three boar pheromone spray can become a routine breeding tool on farm in China

The smelly partner for reproduction

　　Despite the widespread adoption of artificial insemination in the pig industry, few boars (called teaser boars) are still present on farm. Their role is to help farmers decide when to inseminate female pigs. Indeed, the presence of the boar triggers in sows ready for breeding, a specific sexual behaviour that indicates that she is ready for breeding. This period is called heat or estrus. The importance of boar odor in heat detection has been known since the 1960’s. It was indeed demonstrated that the olfactive stimuli with boar odor was key to increase the heat detection rate in estrus females during back pressure test. (Signoret, 1975). The molecules conveying the sexual message emitted by the boar that triggers the sexual behaviours in estrus females are called pheromones.

Recent identification of a 3rd pheromone in the boar saliva

　　Androstenone was the first pheromone identified by Patterson in 1968 and was isolated from the fat of sexually mature boar because this compound did not exist in the barrows and sow of the same age, which was related to the special fishy smell of pork. Androstenone and its metabolic derivative androstenol were then identified to be emitted by the submaxillary gland into the boar saliva due to their characteristic smell as noticed during mating behaviours. Melrose (1971) and Reed (1974) finally confirmed the potential of these molecules to act as signaling pheromones by demonstrating that these molecules were facilitating the adoption of the still standing reflex in estrus females. Recently, US scientists from Texas Tech University performed extensive chemistry on boar and sow olfactive molecules in saliva and learned that 3 molecules were unique to the boar saliva: quinoline had to be considered in addition to androstenone and androstenol. McGlone et al. (2019) confirmed that these 3 molecules together in a spray were the most potent solution to induce the maximal sexual behavioural response to back pressure test among boar- single or binary boar-specific pheromones solution prepared with androstenone, androstenol and quinoline. The 3 molecules association was effective at increasing the still standing reflex which is considered as the golden standard for heat detection. Quinoline was important to increase secondary sexual behaviours such as ear pricked behaviors and sexual vocalisation. This work confirmed boar pheromone as a signature mixture of androstenone, androstenol and quinoline where each compound elicits a partial behavioural response but the mixture causes the synergistic behavioural responses.

Field use of the 3 boar pheromone spray

　　We recently designed an experiment to compare the effectiveness of the 3 boar pheromone spray for weaned sows breeding under commercial conditions. One group of sows were exposed to boar pheromone in combination with a boar grunt audio play and another group was exposed to a fence-line live mature boar for heat detection. Heat was detected in 91% of ovulating sows in the 3 boar pheromone group, which was aligned with early literature reporting the efficacy of smell and sound of boar in triggering the postural standing reaction in estrus sows (Signoret, 1970). At the same time, heat was detected by the boar in 100% ovulating sows. The decrease in heat detection rate in the pheromone group was attributed to the absence of visual stimulation and degraded tactile stimulation. In addition, thanks to frequent ultrasonography diagnostics, we were able to assess exact timing for ovulation in each sow. We could then verify that most of the inseminations occurred within 24 hours before ovulation, which is reputed to be the best fertilisation window. No difference was observed in insemination timings between groups. These observations correlated with satisfying fertility and prolificacy results in both groups, with 93% farrowing rate and 15 total born.

Three boar pheromones to improve biosecurity against ASF

　　In times of devastating African Swine Fever (ASF), implementation of biosecurity measures has never been so important and it has been proven as largely effective in controlling the spread of the disease in China. At the farm level, one of the most important interventions to reduce the risk of introducing ASF virus into the herd is to avoid purchasing animals from unsafe source. Indeed, purchased animals may potentially be ASF virus carriers and be the source of an outbreak on farm. The recent emergence of ASF virus mutants causing chronic form of ASF that is more likely to impact sow reproduction is making detection even more complicated and globally affects trust in the quality of purchased animals. In this context, bringing teaser boars on farm for heat detection is a risk to bring ASF on farm. In addition, what makes a good teaser boar - makes the risk of spreading the ASF virus even more rapidly since teaser boars are effective at stimulating estrus females when they transmit pheromones by nose-to-nose contact. This route is one of the earliest and most effective to spread ASF virus as well, making the teaser boar a great risk to rapidly spread ASF virus on farm. In this context, boar pheromones could be seen as a biosecurity tool for farmers by offering an alternative to purchased boars for heat detection activities, thus limiting the risk of bringing the ASF virus on farm. This solution is also fast to implement on farm, contrary to the production self-replacement teaser boars from the pig flow which requires raising several boars for at least 10 months before qualification.

Three boar pheromones to maximise heat detection

　　In early 2021 a survey with our customers in China focusing on the challenges of heat detection was conducted. More than 100 customers were involved. Not surprisingly, heat detection was not perceived as a major challenge when teaser boars are present on farm. A total of 95% of the respondents considered that heat detection was not difficult, most probably because they thought of sows with clear behaviour signs. However, when asking them if detecting heat in young breeders, that is to say gilts and sows with few parities, was as easy as in older ones, 82% acknowledged that young breeders were causing specific problems. The impact on productivity of doubtful heats was well-known since 96% agreed with the idea that doubtful heat is a risk to miss heat in case of short heat and 98% agreed that clearer onset of estrus would help to position the first insemination. In other words, clear estrus signs in young breeders can be difficult to observe, which impacts the success of the insemination program according to our Chinese customers.

　　In Europe, operations with good breeding results and even top farms are reporting similar hurdles in their reproduction routines. Gilts and parity 1 sows were repeatedly cited as breeders with “difficult heats”. At present, spraying the three boar pheromones has been reported to be effective at maximising heat detection in conjunction with stimulation with live mature boars, with clear benefits in young breeders from various genetic background. For gilts, maximising heat detection is of a particular importance since it validates the cycling status of the breeder. This can strongly impact the economic performance of the farm since it can prevent from deciding to cull gilts based on the erroneous impression that the breeder is in anestrus.

Three boar pheromones to optimise breeder herd performance

　　In addition, more than only helping to know if a breeder is in heat and has to be inseminated, the potential of the 3 boar pheromone spray could lie in improving the timing at which the breeder will be inseminated. Here the improved heat detection procedure will give a better indication of when to inseminate. This could increase the global success of insemination programs on farm. The reasons behind are simple: a clear onset of estrus is an opportunity to develop and execute a standard breeding program with more confidence. It particularly decreases the risk of inseminating breeders too late, thus securing pregnancy rate and helping to position inseminations at the best timing to improve litter sizes. Interestingly, McGlone et al. (2019) reported the result of an experiment comparing the reproductive performance of sows exposed to three boar pheromones on top of live boar exposure to the performance of sows exposed to the live boar only under US commercial conditions. About 4000 sows spread over 12 commercial operations with inventory ranging from approximately 450 to 6000 sows were included in the study. Spraying the three boar pheromones to maximise sexual stimulation during heat detection tended to improve conception rate by 3% and increased litter size by 0.46 piglets. Interestingly, the researcher noticed a particularly high increase in litter size in young breeders of 0.88 extra piglets born from parity 1 to parity 3 sows. These results confirmed how the 3 boar pheromone spray can stimulate reproductive performance.

Conclusion

　　Recent work on the signature mixture of boar-specific saliva molecules has revealed the presence of a new molecule called quinoline. This molecule has been demonstrated to show a sexual pheromone effect in estrus females and to act synergistically with the other pheromones already known to be present in boar saliva. The efficacy of the 3 boar pheromone spray for heat detection and successful insemination in the absence of a live boar is an opportunity to rethink the breeding processes, particularly when a solution to decrease dependency on live boars is desirable for herd health management. Under the normal pig breeding situation, maximising heat detection with the triple boar pheromone spray on top of live boar stimulation has in addition the potential to improve pig reproductive performance by offering an opportunity to timely detect heat and to breed them at better timelines as well.

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