Allometric coefficients for physical-chemical parameters of meat in a local sheep breed

With the aim to assess the kind of development of meat colour, pH, chemical composition and fatty acids content, lean meat from a sample cut, taken in correspondence of the first 4 thoracic vertebrae from 164 animals of the Cornigliese sheep breed, was analysed. The animals (104 females, 60 males) were fed with the same nutritional plan; they were between 3.6 and 80.0 months old and their body weight (BW) was between 15.90 and 111.15 kg. Prior to slaughter, the BW was recorded after 12 hours of fasting. Based on BW at slaughter, animals were assigned to one of four BW-classes, identified by means of percentiles distribution: 0-25th percentile, 15.90-50.70 kg BW (n. = 42); 25th-50th percentile, 50.71-63.22 kg BW (n. = 40); 50th-75th percentile, 63.23-75.50 kg BW (n. = 42); 75th- 100th percentile, 75.51-111.15 kg BW (n. = 40). They were slaughtered during 11 sessions. Data were analysed by ANOVA with sex, BW-class, year of birth (2013-2016) and interaction between sex and BW-class as fixed factors and slaughter session as a covariate. The relative growth of physicalchemical parameters of meat on BW was then calculated by applying the nonlinear allometric equation (y = axb). Proximate analysis revealed differences between males and females in protein and fat content at the highest BW-class, with males showing a higher protein and a lower fat content than females (P < 0.05). Meat pH was lower in males than in females until 60 kg BW (P < 0.05), then became higher, but differences were not significant (P > 0.05). Meat colour parameters were not affected by sex in the BW-classes 1 and 4 (P > 0.05), whereas in the middle phase of growth (from 50 to 75 kg BW) males showed higher values for yellowness and chroma, and from 50 to 63 kg BW, also for redness (P < 0.05). Sex related differences in fatty acids (FA) content were recorded in relation to BW-class; poly-unsaturated FA (PUFA) were higher in males than in females from 50 kg BW onward (P < 0.05). The study of allometric function revealed that females were or tended to be earlier than males (lower allometric coefficients) for all parameters, except for meat fat and lightness. Meat fat content increased faster compared to BW in females than in males (P < 0.05). Moisture, ash, pH and lightness showed negative common allometric coefficients, and must be considered as very early developing parameters. Females showed negative allometric coefficients for C10-C20 saturated FA (SFA), whereas males showed positive allometric coefficients for C10-C16 SFA, then negative coefficients. Allometric coefficients for PUFA showed significant differences between sexes, being females earlier than males (P < 0.01): PUFA deposition increased with BW, but more in males than in females. Our study showed that in Cornigliese sheep breed most of the physical-chemical parameters of meat develop differently in males and females. Due to the different deposition of PUFA in males and females in relation to BW, the optimisation of time of slaughter is suggested as it can impact the physical-chemical parameters of meat, and it might in turn affect consumers’ health.