Lanctôt S, Fustier P, Taherian A R, Bisakowski B, Zhao X, Lacasse P
Department of Animal Science, McGill University, Sainte-Anne-de-Bellevue, Quebec, Canada H9X 3V9.
Saint-Hyacinthe Research and Development Centre, Agriculture and Agri-Food Canada, Saint-Hyacinthe, Quebec, Canada J2S 8E3.
J Dairy Sci. 2017 Mar;100(3):2269-2281. doi: 10.3168/jds.2016-12087. Epub 2017 Jan 18.
The transition from lactation to the dry period in dairy cows is a period of high risk for acquiring new intramammary infections. This risk is reduced when the involution of the mammary gland is completed. Accordingly, approaches that speed up the involution process after drying-off could reduce the incidence of mastitis. The current study aimed to develop a biological response modifier that could be injected into cow teats to promote immune cell migration and speed up involution. Chitosan, a natural polysaccharide derived from chitin, is able to trigger host innate immunity. We developed 2 formulations made from either high- or low-viscosity chitosan. Both are liquid at room temperature but form a hydrogel at body temperature. In the first experiment, each udder quarter of 7 Holstein cows in late lactation was randomly assigned at drying-off to receive one of the following intramammary infusions: 2.5 or 5 mL of 5% (wt/vol) low-viscosity chitosan hydrogel, 5 mL of 5% high-viscosity chitosan hydrogel, or 5 mL of water. Milk (mammary secretion) samples were collected from each quarter on d -4, -1 (drying-off), 1, 3, 5, 7, and 10. Milk somatic cell counts and the concentrations of involution markers such as BSA, lactate dehydrogenase, and lactoferrin were measured in each sample. In comparison with the control, the chitosan hydrogel infusions significantly hastened the increases in somatic cell counts, BSA and lactoferrin concentrations, and lactate dehydrogenase activity in mammary secretions. No major differences between sources or volumes of chitosan were observed for the measured parameters. The compatibility of this approach with an internal teat sealant was verified in the second experiment. Each udder quarter of 8 Holstein cows was randomly assigned at drying-off to receive one of the following intramammary infusions: 5 mL of 2% low-viscosity chitosan hydrogel, 4 g of an internal teat sealant, a combination of sealant and chitosan, or 5 mL of water. Milk (mammary secretion) samples were collected from each quarter on d -4, -1 (drying-off), 5, and 10 to measure involution markers. These results suggest that chitosan hydrogel infusion hastened mammary gland involution and activate immune response, which may reduce the risk of acquiring new intramammary infections during the drying-off period. Those results were not affected by the presence of the teat sealant, showing that both approaches are fully compatible and could be used in combination.
奶牛从泌乳期过渡到干奶期是发生新的乳房内感染的高风险时期。当乳腺退化完成时，这种风险会降低。因此，在干奶后加速退化过程的方法可以降低乳腺炎的发病率。当前的研究旨在开发一种生物反应调节剂，可注入奶牛乳头以促进免疫细胞迁移并加速退化。壳聚糖是一种从几丁质衍生而来的天然多糖，能够触发宿主的先天免疫。我们开发了两种由高粘度或低粘度壳聚糖制成的制剂。两者在室温下均为液体，但在体温下会形成水凝胶。在第一个实验中，将7头处于泌乳后期的荷斯坦奶牛的每个乳房象限在干奶时随机分配，以接受以下乳房内注射之一：2.5或5 mL的5%（重量/体积）低粘度壳聚糖水凝胶、5 mL的5%高粘度壳聚糖水凝胶或5 mL水。在第-4、-1（干奶）、1、3、5、7和10天从每个象限采集牛奶（乳腺分泌物）样本。测量每个样本中的牛奶体细胞计数以及诸如牛血清白蛋白、乳酸脱氢酶和乳铁蛋白等退化标志物的浓度。与对照组相比，壳聚糖水凝胶注射显著加速了乳腺分泌物中体细胞计数、牛血清白蛋白和乳铁蛋白浓度以及乳酸脱氢酶活性的增加。在所测量的参数方面，未观察到壳聚糖来源或体积之间的重大差异。在第二个实验中验证了这种方法与内部乳头密封剂的兼容性。将8头荷斯坦奶牛的每个乳房象限在干奶时随机分配，以接受以下乳房内注射之一：5 mL的2%低粘度壳聚糖水凝胶、4 g内部乳头密封剂、密封剂和壳聚糖的组合或5 mL水。在第-4、-1（干奶）、5和10天从每个象限采集牛奶（乳腺分泌物）样本以测量退化标志物。这些结果表明，壳聚糖水凝胶注射加速了乳腺退化并激活了免疫反应，这可能会降低干奶期发生新的乳房内感染的风险。这些结果不受乳头密封剂存在的影响，表明这两种方法完全兼容，可以联合使用。
