Elsevier

Meat Science

Volume 150, April 2019, Pages 85-92
Meat Science

An evaluation of environmental, intrinsic and pre- and post-slaughter risk factors associated to dark-cutting beef in a Federal Inspected Type slaughter plant

https://doi.org/10.1016/j.meatsci.2018.12.007Get rights and content

Abstract

The objective was to determine the risk factors associated to dark-cutting in bovine carcasses. The study was conducted at a Federal Inspection abattoir located in northeastern Mexico. A random sample of 394 animals at slaughter was used. A total of 26 explanatory variables were evaluated; the analysis included environmental, animal-specific, and management factors both at pre- and post- slaughter periods. Only four variables were statistically significant within the final logistic regression model (P < .001). The frequency of dark-cutting carcasses was 13.45%. Lairage time was directly proportional to the percentage of risk for dark-cutting beef. Improper desensitization also increased the frequency of carcasses with this anomaly. Backfat thickness and the 24-h pH differential of the carcasses were inversely proportional to the risk for dark-cutting beef. An interesting finding was that risk factors for DFD meat are present in all stages of the slaughter process and thus to effectively address this problem an integral evaluation is needed throughout the slaughter process.

Introduction

The growing demand for proteins of animal origin has led to a considerable increase in the number of animals slaughtered worldwide (Blokhuis, Keeling, Gavinelli, & Serratosa, 2008). As a result of this larger quantities of cattle are handled in a shorter amount of time negatively affecting animal welfare and meat quality (Adzitey & Nurul, 2011; Malmfors & Wiklund, 1996). When inadequate animal management is used before slaughter, muscle glycogen is consumed due to the stress to which it is subjected (Lahucky, Palanska, Mojto, Zaujec, & Huba, 1998; Lawrie & Ledward, 2006) this leads to metabolic and hormonal changes in the muscle of the live animal, altering color (dark meat) and pH (> 5.8) in the post-mortem muscle due to a low production of lactic acid in the carcass, a defect known as dark-cutting beef (Hughes, Clarke, Purslow, & Warnerd, 2017; Jacob, Pethick, & Chapman, 2005). As a consequence, meat shelf life is reduced, and meat characteristics become less acceptable to the consumer (Huff-Lonergan & Lonergan, 2005; Viljoen, de Kocka, & Webbb, 2001; Wulf, Emnett, Leheska, & Moeller, 2002), causing economic loss to producers (Holdstock et al., 2014; Leyva-García, Figueroa-Saavedra, Sánchez-López, Pérez-Linares, & Barreras-Serrano, 2012; Scanga, Belk, Tatum, Grandin, & Smith, 1998).

Dark-cutting beef, also called Dark, Firm and Dry (DFD) meat, is associated with long transport distances for cattle and reduced availability of space in the vehicles where the cattle is transported (Campo, Brito, Soares De Lima, Hernandez, & Montossi, 2010; Ferreira et al., 2006), type of cattle acquisition (Ferguson, Warner, Walker, & Knee, 2007; Stevenson, Knee, Philpotts, & Warner, 1996), as well as the presence of stress elements (unknown noises and smells, mixing animals, mounts, new social hierarchies) in waiting pens and the corridors where the animals are steered to the stunning box (Arik & Karaca, 2017; Chen, Arsenault, Napper, & Griebel, 2015; Ferguson & Warner, 2008; Llewelyn, Border, & Allerton, 2002). The use of harmful instruments in the drive to the stunning box has also been reported as a risk factor (Perez-Linares, Figueroa-Saavedra, & Barreras-Serrano, 2006; Sotelo, Perez-Linares, Figueroa-Saavedra, Barreras-Serrano, & Sanchez-Lopez, 2008). Improper desensitization increases the likelihood of the presence of DFD meat, given that the animal is able to perceive pain during exsanguination (Chulayo, Bradley, & Muchenje, 2016; Önenç & Kaya, 2004). Extreme environmental conditions have also been associated to the presence of this quality problem (Gregory, 2010; Kadim et al., 2004; Knee, Cummins, Walker, & Warner, 2004).

Some intrinsic characteristics (racial origin, sex, age, weight) contribute as predisposing factors to stress and therefore to the presence of DFD meat; Bos indicus cattle have been associated to DFD due to their nervous temperament (O'Neill, Webb, Frylinck, & Strydom, 2006; Voisinet, Grandin, O'Connor, Tatum, & Deesing, 1997). Intact males are more exposed to stressful conditions such as fights and other social behavior than females or castrated males (Jones & Tong, 1989; Mach, Bach, Velarde, & Devant, 2008). Older animals and those with higher body weight have presented darker carcasses (Arik & Karaca, 2017; Hopkins, Stanley, Martin, Toohey, & Gilmour, 2007; Mahmood, Basarab, Dixon, & Bruce, 2016a).

The post-slaughter stage can also be associated to the presence of dark-cutting carcasses. The muscle-to-meat conversion process is influenced by the relationship between the rate of pH decrease in the carcass and its temperature (Marsh, Ringkob, Russell, Swartz, & Pagel, 1987; Melody et al., 2004). This relationship is directly responsible for the meat's final pH and color (Kim, Warner, & Rosenvol, 2014; Page, Wulf, & Schwotzer, 2001) the problem has been also related to certain carcass characteristics, such as its weight and the backfat thickness, as well as the space allowance for carcasses in the cold room (Hargreaves, Barrales, Peña, Larraín, & Zamorano, 2004; Lonergan, Zhang, & Lonergan, 2010; McGilchrist, Alston, Gardner, Thomson, & Pethick, 2012).

Studies such as those mentioned above have been carried out to establish an association between the presence of DFD meat and the factors evaluated; however most of them have examined this relationship by evaluating the factors in an individual and isolated manner, which does not allow to analyze the joint effect of factors or their interactions, as well as establishing any increase in the risk for the presence of DFD meat. Therefore, the objective of this study was to evaluate, by means of a logistic regression analysis, the association between environmental, intrinsic and pre- and post-slaughter risk factors with the presence of dark-cutting meat in bovine carcasses.

Section snippets

Materials and methods

The study was performed between November 2016 and August 2017 in a slaughter plant located in northeastern Mexico. The study was evaluated and approved by the Veterinary School Bioethics Committee.

In Mexico slaughterhouses are regulated either by municipal authorities or by the federal government. If the latter is the case, the plant is classified as Federal inspected type (FIT) and therefore must apply a standardized slaughter procedure that is federal mandated, follow stricter regulation and

Results

It was estimated that the incidence of DFD meat in the population considered in this study was 13.45%.

The description of the quantitative and categorical explanatory variables is presented in Table 1, Table 2. The observed frequencies of animals with visible lesions, fallen during the drive to the stunning box and of Bos indicus racial origin were very low, so these 3 variables did not form part of the group of factors included in the analysis within the multiple logistic model.

Of the 23

Discussion

The presence of DFD meat in different regions of Mexico has been fluctuating in recent years, with percentages of affected carcasses ranging from 8.15 to 47.63 (Leyva-García et al., 2012; Perez-Linares et al., 2006; Sotelo et al., 2008). The frequency found in the present study (13.45%) is at the bottom of this range; however, in general, in the last decade the country has experienced a growing trend for DFD meat. As a region the problem is not only Mexican; in Canada and the US, neighboring

Conclusion

Only four of the evaluated variables had explanatory value within the mathematical model used to predict the percentage of dark-cutting beef; however, each of them are of different types: the waiting time in the pen is part of the pre slaughter handling, the effect of improper desensitization is part of the stage immediately prior to slaughter, which infers an animal welfare problem in this period. Backfat thickness is intrinsic to cattle and the pH differential is part of the post-mortem

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declarations of interest

None.

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