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Evaluation of pork quality
in two J.L. Hasty, E. van Heugten, and M.T. See
Summary The effects of vitamin E supplementation (0, 75, 150, 300, and 600
mg/kg) for 6 weeks prior to slaughter on pork quality of two different
genotypes was evaluated. Berkshire pigs had improved meat quality as measured
by water holding capacity and ultimate pH compared to Hampshire pigs. Vitamin E supplementation for 6 weeks at
levels up to 600 mg/kg increased vitamin E content of loin muscle, but did
not appear to improve water holding capacity or ultimate pH in either
genotype. Introduction
Pork quality is one of the big issues facing the pork industry
today. With differing preferences
from the export and domestic market, providing the consumer with an appealing
product has become even more difficult.
The elimination of Pale Soft and Exudative (PSE) pork from the market
has become more of a challenge with the incorporation of leaner breeds into
production to help satisfy the consumers demand for a healthier and leaner
product. Environment, genetics and
nutrition all play a role in the occurrence of PSE pork. Nutritional stragies such as feeding high
levels of vitamin E have shown potential for improving pig performance early
in the grower phase (Asghar et al, 1991) and possible improvement in pork
quality. Genetics also plays a
significant role in the quality of pork that enters the market. The NPPC Terminal Line Genetic Evaluation
Program (1994), which evaluated various breeds in loin meat quality traits,
showed Berkshire breeds to have superior traits and Hampshire breeds to
produce low quality meat according to parameters measured. The objectives of this research were to:
1) evaluate the potential water holding capacity (WHC) and pH in pigs of two genotypes using the shot biopsy
technique, and 2) to evaluate the effect of feeding high levels of vitamin E
on pig performance, WHC, 24 hour drip loss, and pH. Our hypothesis was that
vitamin E would improve pork quality within the two genotypes, with the
greatest improvement in the Hampshire pigs. Materials and Methods A total of 240 pigs was used (120 Berkshire x PIC and 120 Hampshire x
PIC) and allotted within genotype to one of 5 dietary treatments based on
body weight and sex. Pigs were
housed 3 pigs per pen at the NCSU Swine Evaluation Station, Clayton, NC. The diets (Table 1) were standard corn and
soybean meal (0.83% lysine) diets with poultry fat as the fat source,
stabilized with ethoxyquin. A control
diet was formulated containing the NRC requirement of 22 mg vitamin E/kg diet
and treatment diets were supplemented with 75, 150, 300 and 600 mg vitamin
E/kg from a-tocopheryl
acetate. Pigs were allowed ad libitum
access to feed and water throughout the six-week feeding period. Body
weights, and feed intake were taken on day 0, 21, and 42. Biopsy samples were taken from the right
loin on day 42 to determine meat quality characteristics before slaughter
(Cheah et al., 1993). Pigs were
slaughtered at a commercial facility and slaughter data were taken at this
time. Lion initial pH (pHI;
the pH measured 45 minutes after slaughter), and ultimate pH (pHU;
the pH measured 24 hours after slaughter) were taken using a hand-pH
meter. WHC was measured 24 hours
after slaughter using the filter paper method (Kauffman et al., 1986). Loin samples were obtained and analysed
for vitamin E concentration. Table
1. Diets
Data were analyzed as a randomized complete block design with a
factorial arrangement of treatments using the general linear models (GLM)
procedures of SAS (1988) with factors being genotype, gender and vitamin E
level. Contrast comparisons were made
to determine the effect of vitamin E supplementation versus control and to
evaluate linear and quadratic effects of supplementation. Results and Discussion Pigs fed diets with increasing levels of vitamin E tended to have a
higher (linear effect, P < 0.10) average daily feed intake (ADF), which
was not affected by genotypes (Figure 1).
Average daily gain (ADG) was greater (P < 0.001) in Hampshire pigs
compared to Berkshire pigs, with no effect of vitamin E (Figure 2). Gain to feed ratio (G:F) was greater (P
< 0.001) in Hampshire pigs compared to Berkshire pigs. Supplementation of
vitamin E to the diet tended to decrease (P < 0.01) G:F (Figure 3).
Increasing vitamin E in the diet increased the concentration of vitamin E (P
< 0.001; linear effect, 2.02 to 5.92 mg/kg) in the loin for both
genotypes, but there was no effect of genotype (Figure 4). 
Figures 1 and 2. Effect of vitamin E and genotype on Average Daily Feed Intake and Average Daily Gain. 
Figures 3 and 4. Effect of vitamin E and genotype on Gain:Feed and day 0 pork chop vitamin E concentration. Biopsy fluid recovery tended to be higher (P < 0.01) in the Hampshire
pigs than in the Berkshire pigs, indicating that the muscle from Hampshire
pigs was less capable of retaining water. Vitamin E supplementation had no
significant effect on biopsy fluid recovery amounts and there was no
interaction between genotype and vitamin E supplementation (Figure 5). Biopsy fluid pH tended to be higher (P
< 0.10) in the Hampshire pigs, but vitamin E had no significant effect
(Figure 6). Drip loss measured 24
hours after slaughter was greater in Hampshire pigs (Figure 7), which was in
agreement with the results obtained using the biopsy procedure. Ultimate pH (pHu), was reduced
in Hampshire pigs (P < 0.001; Figure 8) compared to Berkshire pigs. These results are consistent with the
observations by NPPC (1994) indicating that Hampshire pigs have poorer meat
quality than Berkshire pigs.
Supplementation to the diet of vitamin E did not affect drip loss or
ultimate pH (Figures 7 and 8). 
Figures 5 and 6. Effect of vitamin E and genotype on biopsy fluid recovery and biopsy fluid pH. 
Figures 7 and 8. Effect of vitamin E and genotype on 24 hour drip loss and ultimate pH. References: Asghar,A., J. I. Gray,
E. R. Miller, P.K. Ku, A. M. Booren, and D. H. Buckley. 1991b. Influence
of supranutritional vitamin E supplementation in the feed on swine growth performance and deposition in different tissues. J. Sci. Food Agric. 57:19. Cheah, L. S., A. M.
Cheah, R. Lahucky, J. Mojto, and L. Kovac.
1993. Prediction of meat
quality in live pig using stress-suceptible and stress-resistant animals. Meat
Science. 34:179-189. Kauffman, R. G., G.
Eikelenboom, P. G. van der Wal, G. Nerkus, and M. Zaar. 1986. The
use of filter paper to estimate drip loss of porcine musculature. Meat Science. 18:191-200. Morgan, J.B., G.C.
Smith, J. Cannon, F. McKeith, and L. Heavner. 1994. Pork distribution
channel audit report. Pork Chain
Quality Audit, Progress Report, April
6, 1994. p. 30. NPPC. 1995.
Genetic evaluation: Terminal line
program results. National Pork Producers
Council publication, Des Moines, IA. 
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