Zootechnical evaluations of the adaptive capacity of native cattle breeds to climate change under different farming conditions

Climate change is increasingly impacting livestock farming by reducing animal productivity, compromising animal welfare and health, and causing economic losses. As a consequence, mitigating the negative effects of rising temperatures requires farmers to adopt several management strategies, such as upgrading farm facilities (e.g., fans, sprinklers, and shading structures), along with higher operating costs associated with increased water use for cooling and electricity consumption for ventilation systems. In this context, cattle farming is among the most affected, since high-producing cows are particularly vulnerable to heat stress (HS), due to the genetic selection for milk yield (which increases metabolic heat production), and due to the greater feed intake (more digestion-related endogenous heat). Current HS research has mainly focused on Holstein cows, but different studies have shown a different HS responses among distinct high producing cows breed. In this context, based on the hypothesis that local breed may have higher thermotolerance due to environmental adaptation, the aim of this thesis was to evaluate HS response in Sicilian local breeds, specifically Cinisara and Modicana cow and to evaluate potential nutritional strategies to mitigate the negative effects of HS in dairy cows. The first part of the research assessed thermotolerance in Cinisara cows managed under semi-extensive systems during summer, by monitoring temperature-humidity index (THI), rectal temperature (RT), milk yield (MY), and milk composition. The results demonstrated that Cinisara cows were able to tolerate higher THI levels compared to high-producing breeds such as Holstein. Indeed, both RT and MY were affected only when THI exceeded 77. Below this threshold, RT, milk quantity and quality were only slightly affected by THI. Moreover, Cinisara cows exhibited higher RT during the afternoon hours, but within the physiological range and with a slight diurnal variation. These findings suggested that Cinisara has effective resilience to high temperatures, likely due to its genetic background and long-term adaptation. The second part of this thesis focused on Modicana cows, evaluating the effects of increasing THI on milk performance and on oxidant-antioxidant plasma markers. Across different THI classes (55, 68, 71, 80), Modicana cows showed no differences in MY, and for milk quality, except for milk fat levels. However, reactive oxygen metabolites (ROM) significantly increased, whereas 4 paraoxonase (PON), advanced oxidation protein products (AOPP), and β-carotene, significantly decreased. At the same time, HS reduced plasma glucose and non-esterified fatty acids (NEFA), and increased monocytes. The findings of this study indicate that, despite being considered a resilient breed – showing no significant reduction in MY – also local breed can experience oxidative and metabolic strain under high thermal load, highlighting the need to adopt strategies that preserve physiological stability during HS events. The final part of this thesis explored a nutritional approach to mitigate HS effects by supplementing Fleckvieh cows with rumen-protected dry grape extract (Nor-Grape BPO), rich in low–molecular weight polyphenols. Under naturally occurring HS conditions (THI > 72), supplemented cows exhibited improved performance and physiological responses compared with cows without supplementation. Indeed, supplemented cows showed better thermoregulation, reflected by lower RT and reduced heavy breathing. Immune-metabolic responses improved as well, with higher plasma zinc and myeloperoxidase, reduced haptoglobin, enhanced neutrophil and monocyte phagocytic activity, and modulated inflammatory cytokines during peak HS. These findings demonstrated that inclusion of Nor-Grape BPO offers a promising nutritional strategy to counteract the negative effects of HS in dairy cows.