## 1 Introduction  
Maize (_Zea mays_) and sorghum (_Sorghum bicolor_) are major worldwide crops and are largely used as feed in livestock farming [1]. A useful method in forage production is the use of arbuscolar mycorrhizal fungi (AMF). These fungi, which form symbiotic relationships with about 80% of herbaceous plant species, including many important crops, have near global distribution [2]. Arbuscolar mycorrhizal fungi decrease plant water stress and increase the acquisition of minerals [2]. Higher levels of phosphorus, nitric oxide, indole-3-acetic acid, sucrose, and glucose in roots are correlated with AMF development [3]. In exchange for these benefits, plants supply AMF with large amounts of carbohydrates [4]. Therefore, AMF can speed up plant growth and reduce fertilizer and water requirements, with economic and ecological advantages. It has been reported that seed inoculation of sorghum and maize forage by AMF, coupled with reduced fertilizer use, generates higher profitability per hectare (+F732 and 6670 for sorghum and maize, respectively), and increases net energy (+0.60 and 0.24, respectively) and energy use efficiency (+0.85 and 0.53, respectively) in cattle and buffalo nutrition without affecting milk yield [5]. Although seed inoculation with AMF does not affect the quality of forage, it influences the chemical composition of silage in terms of increased biomass, proteins, and dry matter [5]. Other studies have reported that mycorrhizal plants have different volatile organic compound (VOC) emissions compared to nonmycorrhizal plants, because arbuscular mycorrhizal fungi can strongly influence the metabolism of their host plants [6; 7]. Particularly, emissions of the green leaf volatile (Z)-3-hexenyl acetate and other plant defensive volatile compounds, like terpen, were 63% lower in mycorrhizal compared to nonmycorrhizal _Plantago lacelata L_. after an insect herbivore attack [7]. In fact, at the beginning of the process, AMF seem to be able to regulate the methyleryththird phosphate (MEP) pathway of defense-signaling cascades in the plant, and reduce the generation of defense compounds [8]. This occurs because a strong induction of transcript levels of two of the pivotal enzymes of the MEP pathway takes place [9; 10]. Another study investigated the effects of AMF on the VOC profile of sorghum (_Sorghum bicolor_) roots. Plants were grown in pots inoculated with either _Gomus mosesea_ or _Gomus intraradices_ to form mycorrhiza with the roots. The quantity and type of resulting volatiles were dramatically altered by the presence of AMF. Generally, AMF induce plants to emit more alcohols, alkenes, ethers, and acids, but fewer linear-alkanes compared to control plants inoculated with sterile inoculum [11]. There are no studies in the scientific literature about a possible effect of AMF feeds on milk quality and composition. Milk fat is an important source of nutrients and energy, but it is also crucial, together with VOCs, to the flavor of milk. The fatty acids (FAs) and VOCs of fresh raw milk arise from both animal metabolism and the type of feed. In particular, VOCs are transferred from fodder to milk via the organism (through the lungs or the rumen), or are formed in the organism (in the rumen and/or by metabolic processes in the liver or mammary gland) [12; 13]. It has been demonstrated that the first absorption route is the faster one [14; 15]. Some studies have reported that the forage type affects the FAs, VOCs, and organoleptic properties of milk [16; 17; 18; 19]. The most volatile free FAs and other VOCs, such as ethyl esters, aldehydes, nitrogen compounds, ketones, alcohols, and dimethylsulphone, represent the main aromatic constituents of milk, and their quantitative differences can explain the different odors that characterize raw milk from different species [20; 21; 22]. Although the FAs, VOCs, and organoleptic properties in milk have been widely studied in relation to forage type, so far no study has aimed to verify FAs and VOCs in milk when cattle are fed mycorrhizal forage.