猪群规模对猪群健康的影响

对于即将设立大规模生猪养殖体系的决策者们不得不考虑的一个问题：单场的规模设置为多大合适？2400头生产母猪/4800头还是20000头生产母猪？有倾向于小而美的--鸡蛋放在多个筐子里的；也有大干猛上、气吞河山的--不玩则已，动则万头母猪的。最终单场或者单点群体规模的大小由各种因素综合妥协而定，个中因素不乏：拿地成本、粪污集中处理--环保成本、运营管理成本分摊、周边关系维护成本、管理&生产效率等等，其中一个因素：猪群健康状况的维持以及疫病发生时的稳定乃至净化的成本，无论是非瘟语境下抑或是常见的仔猪流行腹泻或者蓝耳病或者口蹄疫的感染压力下，健康是效益蓝图众多个零前面的那个数字，若此数字为0则所有的效益蓝图都将化为乌有。

猪群规模大小对猪群健康的影响到底如何？本连载将从生物学原理及兽医流行病学层面，结合管理及环境相关因素，针对猪群规模的度量、猪群规模对疾病的影响等，通过统计学模型，更科学直观地剖析猪群规模与猪群健康的关系。此研究得到了丹麦农业部以及美国农业部的动植物检疫局、兽医处以及加利福尼亚戴维斯分校食用动物健康中心的资助。

猪群规模对猪群健康的影响

对于度量猪群规模的讨论，需参考一个地区的猪群密度，或猪群内的饲养密度，因为猪群密度可能与猪群规模正相关。某些国家将较大猪群密度与较大猪群规模相混杂，进而阐述猪群规模效应。关于猪伪狂犬病，除考虑猪群规模为风险因素外，还需着重考虑区域内受感染的猪群或猪只密度，现今至少有五项研究证实这一观点。研究表明，将相关管理变量和猪群密度纳入统计模型后，猪群规模效应确实不再显著。

A discussion of herd size measures would be incomplete without reference either to herd density in an area, which might also be positively correlated with herd size, or to pig stocking density within herds. Greater herd density may be confounded with larger herd size at least in some countries, such asDenmark, and therefore might in part explain the reported herd-size effects. The importance of considering the density of infected herds or pig density on an area basis in addition to herd size as risk factors for pseudorabies was recognized in at least five studies . Indeed, in one study , the effect of larger herd size was no longer evident after related management variables and density of pigs had been included in the statistical models.

很少将大栏和空间的饲养密度作为引发猪病的风险因素进行研究，其原因有很多。很难精确测量猪只密度，从分娩到育肥，数值会随着不同生产阶段发生改变。即使存在较好的度量标准，也仅适用于大栏内，而度量猪群规模时，需要对群集或过度分散进行调整，所以研究分析会很复杂。 ，猪群规模与猪只密度之间存在共线性。在14篇有关胸膜炎或肺炎病变的研究中，只有7篇在度量猪群规模时对饲养密度进行测量，从而对控制猪群的肺炎问题提出标准建议，强调最多改变20个环境变量，包括密度、空间和每栋猪舍内的猪数量。近期研究 提出，对于育肥猪的呼吸道健康，空间和地面的饲养密度是重要的预测因素。

Pen and air-space stocking density have been investigated infrequently as risk factors for swine diseases, and there a number of possible reasons for this. First, pig density is difficult and tedious to measure accurately, and the value changes with the stage of production in farrow-to-finish herds. Secondly, even if a good measure exists, measurement is usually done at the pen level and herd-level analysis is complicated by the need to correct for clustering or over-dispersion. Thirdly, there is collinearity between herd size and pig density. Of the 14 unique reviewed studies of pleuritis or pneumonia lesions , only seven evaluated a stocking density measure of herd size, yet standard recommendations for the control of pneumonia in problem herds emphasize alteration of up to 20 environmental variables, including density, air space, and pigs per building. The importance of air-space stocking density and floor-space stocking density as important predictors of respiratory health in finisher pig has been reaffirmed in recent studies .

另一项与地面、空间密度和猪群规模度量有关的因素也需考虑。多变量模型中，这些度量值可能存在共线性，这就使研究人员针对猪群规模得出一两个度量值后，便不再对其进行度量。实践中，通常采用最容易获取猪群规模的度量方式，且无论选择哪种度量方式，作者均可以假设变量间的相关性足够高，能够相互代替。不过，后一种假设不一定正确。例如，笔者估算了三种常用的猪群规模度量方式之间的两两相关系数：作为全国养猪调查的一部分，调查了美国1306个分娩至育肥式猪场，统计其母猪数量、每年生猪销售量和总存栏量。估算范围在0. 20至0.61，以此表明仅为中等线性关系。因此，多变量模型中，可采用多种猪群规模度量方法。

Another consideration relevant to the measurement of floor and air-space density and measures of herd size warrants comment. The possible collinearity of these measures in multivariable models may have dissuaded researchers from recording more than one or two measures of herd size. In practice, the most easily acquired measure of herd size is generally used and, for whatever measure is selected, authors probably assume that the variables are sufficiently highly correlated to be interchangeable. The latter assumption may not necessarily be correct. For example, we estimated pairwise correlation coefficients between three frequently used measures of herd size: the number of breeding females, the number of pigs sold per year and the total inventory of pigs for 1306 US farrow-to-finish farms studied as part of the National Swine Survey . The estimates ranged from 0. 20 to 0.61, which indicated only low to moderate linear relationships. Hence, multiple measures of herd size might be included in multivariable models.

猪群规模与生态保护、可持续发展

在养殖过程中，不仅要追求经济效益，更要注重生态保护和可持续发展。生态养殖、绿色养殖已成为我国养殖业的发展方向。猪群规模的大小直接影响到养殖场的环保成本和粪污处理。因此，在确定猪群规模时，应充分考虑环保因素，采取科学合理的养殖模式，实现经济效益与生态保护的和谐统一。

实用的解决方案

为了提高猪群健康水平，降低疫病风险，以下是一些实用的解决方案：

• 加强猪场生物安全措施，严格控制人员、车辆、物资等进出猪场，降低疫病传播风险。
• 优化猪场环境，保持猪舍通风良好、温度适宜，降低猪群发病率。
• 加强猪群健康管理，定期进行猪只体检，及时发现并治疗疾病。
• 推广生态养殖模式，减少对环境的污染，实现可持续发展。

可验证的预测

随着我国养殖业的发展，猪群规模将逐渐扩大。在未来5年内，猪群规模与养殖健康的关系将更加密切。通过科学合理的养殖管理，可以有效降低疫病风险，提高猪群健康水平，实现养殖业的可持续发展。

欢迎用实际体验验证观点

以上观点仅供参考，具体操作还需结合实际情况。欢迎广大养殖户朋友们在实践过程中，不断经验，共同推动我国养殖业的发展。