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To assess the impact of automatic milking systems (AMS) on the different aspects of milk production a research projectinvolving both commercial and experimental dairy farms with different AMS and different management was started. Thispaper reports the results of a follow-up study on primiparous cows focused on assessing some markers to be used tomonitor udder and teat health. Heifers were included after calving and sampled for at least 12 months. Quarter milk samplesand teat measurements were taken to assess: intramammary infection (IMI) frequencies, somatic cell counts (SCC),teat thickness changes, teat skin and apex conditions. The study included 28 cows in herd A and 27 in herd B for a totalnumber of 2344 samples. Overall, teat apex and skin conditions were maintained along the lactation. Teat skin conditionstended to decrease because of the accumulated number of milkings while lactation proceeded, but at a largelyacceptable level in both herds. Teat apex conditions showed a decrease. Teat thickness changes displayed different patternsin the two herds, probably because of the different type of AMS, but in both cases a trend to decrease in thicknesscould be observed. The application of AMS in herd B, free from contagious pathogens, did not influence the frequency ofIMI and the SCC. In herd A, characterized by the presence of Staphylococcus aureus IMI, the frequency of IMI showeda progressive increase, very likely as a consequence of the spread of infections during milking. Teat skin had no associationwith the frequency of IMI. Teat thickness changes outside values considered as physiological proved to be associatedwith decreased conditions in the teat apex score in herd A, but not in herd B. However, a decrease in teat apex scoreproved to be associated with an increase in IMI frequency in both herds. The results of this field trial confirm that AMShave no negative impact on IMI incidence, SCC and teat tissue conditions when the initial cow health status and overallherd management are good. In the presence of contagious pathogens, and when cows have more than 300 days in milk(DIM) the frequency of negative outcomes significantly increases and the proper control measures should be taken.

Several milk components related to immune defences (lysozyme, lactoferrin and γ-globulins, γ-G) and to inflammation (somatic cell counts, SCC; N-acetyl-β-glucosaminidase, NAGase; albumin) were considered. Forty-one quarters and 685 samples of 24 cows were included in the study; among them 534 samples were defined as negative (78·0%), 93 as diseased (13·5%) and 58 (8·5%) as subclinical. The pattern of each milk component in quarters always negative during the follow-up period was evaluated by a mixed model. Statistical analysis showed that days in milk (DIM), age (primiparous, pluriparous), herd and the interaction between herd and days in milk significantly influenced all the markers, with very few exceptions. A subset of samples including the negative quarters before the first outcome of an infection or a subclinical mastitis and the samples from quarters always negative was also selected. The analysis showed that herd, DIM and health status had a significant influence on most markers. Overall, primiparous cows were confirmed to have higher levels of most of the markers than pluriparous cows. The presence of a herd effect on non specific immune defences in fully negative quarters implies that when the mechanisms behind their release are fully elucidated, it might be possible to modulate them. Udder tissues were confirmed as an important source of some immune components, as supported by the inconsistency between SCC mean values and NAGase, lysozyme and lactoferrin values. Overall, quarters with high levels of NAGase, lysozyme and γ-G, exposed to bacteria, did not develop subclinical mastitis. Hence, invading pathogens could induce the development of subclinical IMI when these components and γG are in low concentration. [ABSTRACT FROM AUTHOR]