Effect of growth rate on pork eating quality
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Research partners: BPEX Pork Chain Unit (University of Bristol) and BPEX Pig Development Centre (University of Leeds)
Industrial partners: Tulip Supply group
Project duration: April 2006 – March 2008
Variability in the pig herd is one of the most challenging aspects of modern pig production. The producer’s key objective for age and weight uniformity at the moment of slaughter is compromised by variations in the growth rate of individual animals. Understanding how this intrinsic variation affects the quality of the end product should help the British pig industry to meet consumer expectations for consistent and high quality pork.
The main objective of this study was to investigate both objectively as well as subjectively whether pig growth rate has an impact on pork quality. Instrumental analysis and trained taste panel were used for the objective and subjective assessment respectively.
Two carcase weights (90 and 100 kg live weight) were considered in the study addressing the concern that increasing weights, combined with the use of boars, may result in a higher incidence of boar taint. The study also investigated whether the occurrence of a period of interrupted growth, probably due to infection, has a detrimental effect on tenderness and boar taint incidence.
A total of 225 Large White x Landrace pigs of both genders were fed ad libitum. Pigs were subdivided into three categories, according to their growth rate:
- Fast growing pigs: 0.68 kg/d (average growth rate between weaning and finishing)
- Slow growing pigs: 0.54 kg/d (average growth rate between weaning and finishing)
- Interrupted growth: 0.49 kg/d (average growth rate between weaning and finishing)
The results showed that growth rate had a marked effect on pork quality. Fast growing pigs of both genders produced more tender pork as measured instrumentally (toughness as shear force measurement).
At 110 kg live weight the growth rate effect on tenderness was significantly greater (p< 0.001) than at 90 kg live weight (p< 0.5).
No evidence was found to support the theory that slow growing or ‘interrupted growth’ males had higher boar taint levels as measured instrumentally (HRGC)1. Nevertheless, fast growing males had significantly higher concentration of both boar taint compounds: androstenone (p< 0.5) and skatole (p< 0.01).
Carcase weight (90 vs 110 kg) did not have a significant effect on androstenone and skatole levels in male pigs.
Subjective assessment of the growth rate effect on pork quality was performed by a 10-member taste panel on loin steaks from the heavier pig group (slaughtered at 110 kg live weight). Fast growing males produced significantly more tender (p< 0.01) and juicy (p< 0.5) pork than slow growing males. The overall liking score was also significantly greater (p< 0.5) in fast growing in comparison with slow growing males.
No differences recorded in terms of abnormal flavour or abnormal odour of fat between fast and slow growing males. In females, taste panel assessment under the same conditions also indicated that juiciness and overall liking were significantly higher (p< 0.001 and p< 0.5 respectively) in the fast growing pigs.
Conclusion
The overall conclusion from this study was that the growth rate of pigs fed ad libitum had a substantial impact on pork quality. In particular:
- Fast growing pigs produced more tender and juicy pork than slow growing pigs
- At 110 kg the growth rate effect on tenderness was significantly greater than at 90 kg
- Overall liking score at 110 kg was significantly higher in fast than in slow growing pigs
- There is no evidence that slow or interrupted growth increase boar taint prevalence
- Levels of boar taint compounds were higher in fast growing males, but sensory analysis did not reflect a detriment effect on flavour