Culling-associated stress and meat quality in ungulates
Date
2020-12
Authors
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Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: The purpose of this investigation was to evaluate the effects of helicopter-, day- and night-culling on the ante-mortem stress experienced by sub-adult impala (Aepyceros melampus) rams and mature blue wildebeest (Connochaetes taurinus) cows, by determining the effect of hunting method on the serum testosterone, cortisone and cortisol levels at death, and influence on meat quality parameters.
Blood samples were collected immediately post-mortem and analysed for the above-mentioned steroid hormones, and the serum levels assayed were compared to the expected diurnal secretion pattern of each hormone. During and up and to 24 hours post-mortem, the pH of the Longissimus thoracis et lumborum (LTL) was recorded at regular intervals to establish a post-mortem pH profile, which was then related to the respective meat quality parameters. The left LTL muscle was removed from the carcass for physical and proximate analysis. The physical parameters included pH, water-holding capacity, tenderness and colour, were subsequently correlated with the serum hormone levels.
The serum testosterone levels in the impala were not influenced by culling method, however, serum cortisone concentrations were higher in the night-culled impala, when compared to the helicopter- and day-culled animals. The serum cortisone and cortisol levels of night-culled impala were higher when compared to previously established baseline levels for impala. The serum glucocorticoid concentrations determined for the night-culled impala were similar to that of the helicopter- and day-culled animals, thus supporting the deviation from the established diurnal pattern in previous studies. Meat samples obtained from the night-culled impala had an increased water-holding capacity as well as were more tender than the meat samples from the impala of the other culling methods. Culling method did not influence the colour of the meat samples.
The serum concentrations of glucocorticoid hormones determined for the blue wildebeest appeared to conform to previously established diurnal patterns. Blood samples from the helicopter-culled animals were characterized by higher serum concentrations of glucocorticoid hormones than that of the day- and night-culled animals. However, the physical analysis of the meat samples indicated that helicopter-culling resulted in a high pHU, although not statistically different from the other treatment groups, a decreased water-holding capacity and lower shear force values. The day- and night-culled blue wildebeest produced meat samples similar in quality, indicating that these culling methods had no influence on ante-mortem stress of blue wildebeest.
It was observed that all the treatments resulted in high ultimate pH values, characteristic of dry, firm and dark (DFD) meat that is typically caused by chronic ante-mortem stress.
The meat obtained from the helicopter-culled blue wildebeest exhibited DFD qualities which could be attributed to chronic stress. Therefore, correlations between pH parameters and meat quality parameters were analysed. From the correlations, it was determined that with an increasing muscle pHU, there was lower L* values whilst an increasing rate of pH decline resulted in a decreased water-holding capacity.
This is the first study of its kind on impala and blue wildebeest and therefore further research is required to verify these results as all indications are that culling by helicopter, although expensive, has added advantages.
Description
Thesis (MScAgric)--Stellenbosch University, 2020.
Keywords
Meat -- Quality -- Effect of stress on, Ungulates -- Effect of hunting on, Wildlife conservation, Culling (Animals), UCTD