Complex Relationships between Milking-Induced Changes in Teat Structures and Their Pre-Milking Dimensions in Holstein Cows

SIMPLE SUMMARY: Multiple studies have investigated the relationship of teat morphology, and udder health and milkability. Nevertheless, it is crucial to examine how the dimensions of teat structures influence teat tissue changes during milking. The short-term changes in teat structures that result from machine milking are yet to be completely understood, and more studies are needed to fully understand their complexity and potential health risks to animals. We found that milking-induced changes in teat structures depended on their pre-milking size, probably because their dimensions allowed for certain fluid mechanics inside the teat after the forces were applied within the liner of specific dimensions. Furthermore, the dimensions of any teat structure affected changes in multiple other structures. We also observed that some teat dimensions showed a better reaction to milking in relation to milking-induced teat tissue changes. The results of this study could create a better understanding of milking-induced changes in teat tissue. Our findings may help create a detailed computer model for teat reaction to milking, which could be used to improve the development of milking equipment. ABSTRACT: The study aimed to explore the relationship between teat structure dimensions and their short-term reaction to milking, to find the optimal dimensions of teat structures in relation to milking-induced teat tissue changes. Teat structures (teat length, canal length, thickness at barrel and apex, wall and cistern width) were measured by ultrasonography before and after milking for 38 Holstein cows at the beginning, middle, and end of lactation. We found that milking-induced changes in teat structures significantly depended on their pre-milking size. Furthermore, we observed that some teat structures and their changes were interconnected, and some did not affect each other. For example, changes in the barrel thickness and cistern width were affected by all structures, while the canal and apex did not influence each other. We deduced that more favorable changes were observed for teats of medium length, medium barrel and apex thickness, with teat canals of medium length, but with wider cisterns and thinner walls. The results of this study may help improve research in the area of milking-induced changes in teat morphology. Our findings could help understand potential health risks to animals in relation to teat morphology, milking equipment, and machine settings.