Application of mid-infrared spectroscopy to enhance bovine milk technological traits in dairy industry

Worldwide demand for dairy products is increasing and further expansion is expected. In this scenario the improvement of the aptitude of milk to produce cheese is an attractive challenge for several European countries, especially those manufacturing high quality products (e.g. Protected Designation of Origin cheeses). One of the crucial steps of cheese making is the coagulation process that is related with yield and quality of the final product. Milk protein composition, milk coagulation properties (MCP), milk acidity (mainly titratable acidity, TA) and calcium (Ca) and phosphorus (P) contents are the most important traits involved in coagulation process. Traditionally, the determination of MCP, TA, and mineral content is time-consuming, expensive and not applicable at population level. The use of mid-infrared spectroscopy (MIRS) is a rapid and cost-effective tool for recording phenotypes at population level and it is commonly used to determine traditional milk quality traits in official milk laboratories. Lasting years the effectiveness of MIRS to predict phenotypes useful for dairy industry or for genetic purposes has been widely investigated, highlighting a growing interest for this technology. Several studies have demonstrated the potential of MIRS to predict MCP reporting quite satisfactory results (average coefficient of determination, 1-VR, of 0.70). Mid-infrared models have been implemented in several Italian laboratories to provide routine measures of MCP, and the information is mainly used by dairy factories to reward or penalize milk according to MCP. A recent study estimated (co)variance components for MCP using repeated data (n = 63,470) predicted during routine milk recording in Holstein-Friesian cows. Results indicated that genetic variation for MCP predicted by MIRS exists and thus selection at population level is feasible. The same study highlighted that several repeated measures per cow during a lactation are required to estimate reliable breeding values for MCP. Genetic correlations of MCP with production traits, milk composition, and somatic cell score were generally low. Besides MCP, MIRS has been indicated also as a tool to predict TA, and Ca and P contents, reporting 1-VR values of about 0.60 for Ca and greater than 0.70 for P and TA. Mid-infrared models were used to predict Ca and P contents, and TA in milk of about 2,500 Holstein-Friesian cows and to assess (co)variance components for these MIRS-predicted traits. Heritability estimates were 0.10, 0.12, and 0.26 for Ca content, P content, and TA, respectively; the existence of heritable genetic variation coupled with the potential to predict these components for routine cow milk testing, imply that genetic gain in these traits is indeed possible. Mid-infrared spectroscopy is a fast, large-scale, and low-cost tool for collecting phenotypes and its potential to predict MCP, milk acidity, and Ca and P contents has been demonstrated. All these new phenotypes could be used for breeding purposes to improve profitability of dairy chain.