Effect of pre-slaughter handling and transport stress on meat pH, colour, and water-holding capacity in goats

Introduction

While the science of pre-slaughter stress has been studied extensively in cattle, pigs, and poultry, the goat the most important meat-producing ruminant in sub-Saharan Africa has received comparatively little attention [1,2] . This contrast is striking given that goats in East Africa typically endure harsher pre-slaughter conditions than cattle: longer walks to collection points, rougher handling by untrained personnel, and extended transport in overcrowded vehicles along unpaved roads [3] . The physiological mechanism linking stress to meat quality is well established. Acute stress activates the hypothalamic-pituitary-adrenal axis, elevating circulating cortisol, and simultaneously triggers catecholamine release that accelerates glycogenolysis in skeletal muscle [4] . If glycogen is depleted before slaughter, insufficient lactic acid accumulates post-mortem, and the ultimate pH of the meat remains above 6.0 rather than declining to the normal range of 5. 4-5.7. This high-pH meat, termed DFD (dark, firm, dry), has a darker colour due to increased mitochondrial oxygen consumption, reduced water-holding capacity despite its high pH, and shorter shelf life because the elevated pH favours microbial proliferation [5,6] . Transport duration and handling quality are the two most influential pre-slaughter stressors, but their relative contributions and potential interactions in goats have not been characterised in a controlled factorial design [7] . Published goat meat quality data come predominantly from observational abattoir surveys that confound transport distance with handling intensity, making it difficult to isolate the effect of either factor [8,9] . This research was designed to address this gap through a 2 x 2 factorial experiment crossing transport duration (short versus long) with handling quality (calm versus rough) in male Boer goats.

Three objectives guided the work: 1) to quantify the independent and interactive effects of transport duration and handling quality on post-mortem pH decline, colour, and water-holding capacity; 2) to measure pre-slaughter stress biomarkers (cortisol, CK, lactate) and correlate them with meat quality outcomes; and 3) to determine the incidence of DFD meat under each treatment combination.

Material and Methods

Material

One hundred and twenty male Boer goats aged 12-14 months and weighing 28-34 kg were sourced from three commercial farms within 200 km of Nakuru, Kenya. Animals were selected based on uniform body condition score (3.0-3. Values are mean (SD). Different superscript letters within a column indicate significant differences (p<0.05, Tukey HSD). Pre-slaughter stress biomarkers showed a clear gradient across treatment groups (Table 1). Serum cortisol was highest in the long-transport/rough-handling group (52.4 ng/mL) and lowest in the short-transport/calm-handling group (17.6 ng/mL), a threefold difference. Creatine kinase, a marker of muscle damage from physical exertion and bruising, followed the same pattern. Two-way ANOVA confirmed significant main effects of both transport duration (p<0.001 for all biomarkers) and handling quality (p<0.01), with a significant interaction for cortisol (p=0.034), indicating that rough handling amplifies the stress response more in long-transport animals than in shorttransport animals.

Meat quality parameters at 24 hours post-mortem (Table 2) reflected these stress differences. Ultimate pH was 5.58 in the short/calm group and 6.14 in the long/rough group, with a significant transport-by-handling interaction (p=0.012). Lightness (L*) decreased as stress increased, falling from 40.2 in short/calm to 33.1 in long/rough, consistent with the darker appearance of high-pH meat. Drip loss and water-holding capacity were both adversely affected, with the long/rough group showing 68% higher drip loss and 81% larger press fluid area than the short/calm group.

Discussion

The finding that 31.7% of long-transport goats produced DFD meat is consistent with field data from Miranda-de la Lama et al. [7] , who reported 28% DFD incidence in goats transported more than 4 hours in Mexico. It is considerably higher than the 5-12% DFD rate seen in cattle under similar transport durations [5] , suggesting that goats may be more susceptible to transportinduced glycogen depletion, possibly because their smaller body size results in greater surface-area-to-volume heat loss and higher mass-specific metabolic rates during transit [2] . The significant interaction between transport and handling is a novel finding for goats. In cattle, Grandin [10] reported that handling quality and transport distance had additive but noninteractive effects on bruising and cortisol. The present data suggest that goats exposed to prolonged transport arrive at the abattoir in a physiologically depleted state that makes them disproportionately vulnerable to additional handling stress during unloading and lairage. This interaction has practical implications: investing in handler training may yield greater returns in operations with long supply chains than in those serving local markets. The cortisol-pH correlation of 0.72 aligns with published values for sheep (R-squared = 0.68; Broom [4] ) and supports the use of ante-mortem cortisol as a carcass sorting tool. However, cortisol measurement requires laboratory analysis and is impractical for real-time abattoir decisions. Blood lactate, measurable with a handheld analyser, showed a weaker but still significant correlation with ultimate pH (r = 0.61) and could serve as a more accessible proxy for identifying high-risk animals that might benefit from extended lairage.

Conclusion

This research set out to quantify the independent and interactive effects of transport duration and handling quality on goat meat quality using a controlled factorial design. The investigation was motivated by the high incidence of DFD goat meat reported at East African abattoirs and the absence of controlled experimental data to guide mitigation strategies.

The key findings are that transport duration is the primary determinant of post-mortem pH decline and DFD incidence, that handling quality significantly modulates this relationship, and that the combination of long transport with rough handling produces commercially unacceptable meat in nearly one-third of carcasses.

Acknowledgement

Acknowledgements Contributions not qualifying for authorshipThe authors thank the abattoir manager and the animal handlers who participated in the calm-handling training sessions, and the farm managers who supplied the experimental animals.

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