Mitigation of chronic heat stress in growing rabbits by hair shearing: effects on meat quality traits and heat-shock proteins expression

Introduction: Heat stress (HS) represents a major challenge for rabbit production, particularly in regions characterized by high environmental temperatures. The present study investigated the impact of hair shearing on the meat quality traits of growing rabbits exposed to chronic HS conditions. Methods: A total of 150 weaned Pannon Ka rabbits were equally divided into three experimental groups (50 animals/group) and allocated into two rooms. In the first room, a temperature of 20 degrees C was applied and the control group (unsheared, CON) was housed. In the second room, a temperature of 28 degrees C was applied and two groups of rabbits were housed: an unsheared heat-stressed group (HET) and a sheared group (SHR). At slaughter (12 weeks of age), both hind legs (HL) and longissimus thoracis et lumborum (LTL) muscles from 15 carcasses per treatment were collected for physicochemical analyses, sensory evaluation, and heat-shock protein (HSP) expression analysis. Results: Heat stress affected rabbit bone development by decreasing both femur length (P<0.05) and weight (P<0.01). HS also reduced redness and yellowness of the biceps femoris muscle (P<0.01) and increased LTL lightness (P<0.05). Moreover, HS increased LTL meat protein (P<0.05) and ash (P<0.01) contents while reducing lipid content (P<0.05). In contrast, sensory traits of rabbit meat were not affected by HS. Hair shearing partially mitigated most of the observed changes, with sheared rabbits generally showing intermediate values for most traits, except for LTL moisture content, which was the lowest (P<0.05). Gene expression analysis revealed a higher induction of HSP70_1b (P<0.05) and HSP70_8 (P<0.05) in the HET group compared with the CON group, whereas no significant differences were observed in the SHR group compared with either of the other groups. No significant differences were detected in the expression of HSP90 family members. Discussion: Overall, the study confirmed that HS impacts carcass and meat quality of rabbits and that hair shearing can be considered an effective low-cost strategy to alleviate part of the negative effects caused by chronic HS conditions. Hair shearing is particularly applicable in rural production rather than in industrial contexts where this practice would represent a significant labor cost.