Milk yield and quality at udder quarter level are influenced by quarter position, pathogen, and somatic cell score

Abstract

There is a paucity of information about milk composition and quality at the quarter level from complete milking of the udder, mainly because of the difficulties of sampling procedures which imply the adoption of a vacuum system connected to four independent buckets. The objective of this study was to evaluate the effect of quarter position, intramammary infection status, and somatic cells on milk yield and composition at the mammary quarter level of Simmental cows. Milk samples were collected during three consecutive days, after milking individual mammary quarters of 10 lactating cows separately, for a total of 120 quarter milk samples. Samples were analysed for composition, somatic cell count (SCC), differential SCC, and bacterial culture. Somatic cell count was log-transformed to somatic cell score (SCS) to achieve normality of distribution. Sources of variation of milk yield and quality traits were investigated using a linear mixed model which included the fixed effects of quarter position (1 to 4), pathogen presence (positive or negative), and SCS class (low, medium-low, medium-high, and high). The interaction between cow and quarter position was included as random effect. Quarter position significantly affected milk yield, with rear udder quarters yielding more milk compared to their front counterparts, but with negligible effects on milk composition. Classes of SCS influenced milk composition, in a way that quarters with high SCS had lower lactose content and higher differential SCC. This study is a contribution towards the possibility to better understand physiological processes at cow udder quarter level.

HIGHLIGHTS

• The effect of quarter position significantly affected milk yield at the quarter level.

• Rear quarters produced more milk compared to their front counterparts.

• Somatic cells significantly affected the investigated traits, except for milk yield and protein content.

Keywords:

• Milk
• udder quarter
• somatic cell
• pathogen
• cow

Disclosure statement

No potential conflict of interest was reported by the author(s).

Ethical Approval

Procedures adopted in this study do not fall into the scope of an animal ethics evaluation, as they do not reach the thresholds established in the ‘Directive 2010/63/EU (Art. 1) of the European Parliament and of the council of 22 September 2010 on the protection of animals used for scientific purposes’.

Data availability statement

None of the data were deposited in an official repository. The data that support the findings presented in this study are available from the first author or corresponding author upon reasonable request.

Additional information

Funding

This study was supported by the Ministry of Agricultural, Food and Forestry Polices (Roma, Italy) through the project “CowSens – Sensoristica applicata al miglioramento della gestione alimentare, salute animale e della produzione casearia nella vacca da latte” (CowSens ID17, CUP: C C24I19000840001). The staff of the experimental farm “Lucio Toniolo” of the University of Padova (Legnaro, Italy) is gratefully acknowledged for technical support.