# Assessment of Milk Quality in Skopelos Goats Under Low- and High-Input Farming Systems
## 4 Discussion
The decrease in lactose content during lactation has been previously attributed to changes in prolactin activity. While prolactin plays a crucial role in stimulating lactose synthesis by enhancing the activity of enzymes involved in its production, its regulatory effects may decline as lactation progresses [52]; this, combined with the increasing metabolic demand for lipid synthesis and energy production in the mammary gland, may contribute to the observed reduction in lactose concentration over time [53]. Farming systems do not affect TSs in milk. However, as is the case with protein and lactose content, TSs decrease progressively during lactation. In the present study, milk pH ranged from 6.65 to 6.75, with no significant differences across farming systems or years, similarly to what has been previously reported in other studies [16; 54; 55; 56]. The pH remained stable during early and mid-lactation. However, a significant pH increase was observed at the end of lactation similarly to what has been reported by [PERSON] et al. [57]. The EC in milk is influenced by the presence and concentration of electrically charged ions, including sodium (Na\({}^{+}\)), potassium (K\({}^{+}\)), chloride (Cl\({}^{-}\)), and calcium (Ca\({}^{2+}\)) [58]. These ions are crucial in determining the milk's ability to conduct electrical current, making EC a useful parameter for evaluating milk composition and under health. The PCA (Figure 1a, Table 1) demonstrated that the variations in SCC and TBC were reflected in the EC values, indicating that milk with a higher bacterial and SCC content also tends to have increased EC, likely due to under inflammation and compromised milk quality. Since SCC and TBC are key indicators of under health, their influence on EC suggests that monitoring conductivity alongside these parameters provides a comprehensive assessment of milk quality, and EC is a commonly used parameter for detecting subclinical mastitis [10; 59; 60], while the refractive index and Brix values offer insights into the TSs content of milk [61]. Using these physical parameters as rapid assessment point-of-service tools could enhance monitoring practices, facilitating the early detection of health issues and milk quality optimization. SCC and TBC are key indicators of milk quality, under health, and hygiene practices [62; 63]. The results of this study indicate that both SCC and TBC were significantly higher in the extensive farming system compared with the intensive system (Table 1), findings which are in agreement with other studies [12; 15]. These elevated levels may be partially attributed to hand milking, which is more susceptible to contamination, as well as generally less-controlled milking environments. It is also well established that non-infectious factors, such as management practices, significantly influence SCC and TBC levels in goats [43; 64; 65; 66]. High SCC values are commonly associated with subclinical mastitis and reduced milk shelf life, while elevated TBC can compromise milk safety and restrict marketability due to regulatory limits. The lactation stage also had a strong and consistent effect on milk quality. SCC progressively increased from the first to the fourth stage (\(p<0.001\)), likely reflecting cumulative stress on the mammary gland, a factor known to elevate SCC levels [43; 62; 65; 67]. TBC was highest during early lactation, possibly due to the presence of colourst residues and/or a greater susceptibility to contamination. This may also be influenced by environmental factors such as rainfall and high humidity, particularly since the first LS occurred in February, a month typically associated with elevated humidity levels. In addition to the LS, regional environmental differences between the farming systems may have influenced SCC and TBC outcomes.