Study of ultrasound scanning as method to estimate changes in teat thickness due to machine milking in Manchega ewes

Abstract

[EN] To assess the ultrasound technique as a method for estimating the effect of machine milking on teat thickness in Manchega ewes, this work was carried out with a twofold objective: (1) to study the most suitable ultrasound exploration frequency and the effect of the operator in applying the technique and (2) to validate the approach, comparing it with measurements taken by another method (cutimeter). Three studies were designed for this purpose. In the first of them (E1), two experiments were carried out; the first tested frequencies at 5, 7.5 and 10 MHz and the second (E2) checked frequencies at 3.5 and 5 MHz. In the second study, 2 different operators (OP) independently performed ultrasound scans on the same animals (experiment 3, E3): they chose the best ultrasound exploration image recorded on video (experiment 4, E4) and took measurements in ultrasound images of ewes (experiment 5, E5). Finally, in the third study (experiment 6, E6) we designed an experiment in which ultrasound examinations and measurements by cutimeter were performed in the same animals.

The variables measured in the ultrasound scans were teat wall thickness (TWT), teat wall area (TWA) and teat end wall area (TEWA), while the cutimeter was used to gauge teat wall thickness (11). At 10 MHz frequency it was not possible to obtain quality images of teats in ewes, so its subsequent use was ruled out. The teat canal was visible in 45%, 55% and 30% of the pre-milking images at frequencies of 5, 7.5 and 3.5 MHz, with values increasing after milking (63.4%, 77.5% and 36.3%). No significant differences were found in any of the variables (TWT, TWA and TEWA) between the measurements taken before and after milking at the 5 and 7.5 MHz frequencies. Similarly, TWT, TWA and TEWA were significantly greater (p < 0.001) at the 3.5 MHz frequency than at 5 MHz. It was concluded that frequencies of 5 and 7.5 MHz were the most suitable for estimating the teat wall changes caused by mechanical milking.

Operator experience had no effect on the ultrasound explorations performed in the field, although it did significantly influence the choice and measurement of the images.

Mechanical milking caused an increase in TWT of 0.11 cm measured by ultrasound scanning and a reduction in TT of -0.06 cm measured by cutimeter, which would indicate that ultrasound scanning is a more effective method to determine the degree of oedema and congestion caused by machine milking in ewes. In addition, we found a high correlation between TWT, TWA and TEWA with TT before and after milking.

The use of ultrasound techniques may be a useful tool to evaluate the changes that occur in teat tissue due to machine milking in Manchega breed sheep, although it would be necessary to carry out further studies to enable the development of software to choose and measure the frames automatically to help reduce the operator effect on the choice and measurement of ultrasound variables. (C) 2014 Elsevier B.V. All rights reserved.