10.25394/PGS.9117131.v1
Melissa K Davis
Melissa K
Davis
Meat Quality of Turkeys Affected by Heat Stress and Immune Challenge Conditions, and the Relationship Between Meat Quality and the Social Index
Purdue University Graduate School
2019
heat stress
immune challenge
vaccine
pecking
behavior
turkey
meat quality
Animal Growth and Development
Agricultural and Veterinary Sciences not elsewhere classified
2019-10-16 17:57:08
Thesis
https://hammer.purdue.edu/articles/thesis/Meat_Quality_of_Turkeys_Affected_by_Heat_Stress_and_Immune_Challenge_Conditions_and_the_Relationship_Between_Meat_Quality_and_the_Social_Index/9117131
<p>Heat stress (HS)
and immune challenges (IC) are just two of the many stressors poultry can
experience in commercial settings that can have an effect on bird welfare and
final product quality after harvest. Individual animals vary greatly in their
responses to stressors, which can further influence product quality. The
overall goal of this study was to examine the relationships among stress,
behavioral characteristics and meat quality of commercial turkeys. The first
objective of this study was to
determine if the heat stressed or immune challenged turkeys experienced greater
negative effects on overall meat quality compared to a control group. The
second objective of the study was to determine if the frequency of
nonaggressive pecking behaviors among the birds was related to final meat
quality<a>. A total of 92 commercial male, beak-trimmed turkeys were
used in two trials (in time replicates) with a total of 15 rooms and 4-7 birds
per room. There were two to three rooms experiencing each treatment at a time. </a>The heat stressed (HS) treatment subjected the birds to an ambient temperature
of approximately 29 °C, depending on the room’s humidity, and lasted 120
minutes before returning to the normal temperature range. The immune challenge
(IC) treatment consisted of inoculating the birds with a live vaccine for
hemorrhagic enteritis virus. The control (CON) group was not subjected to heat
stress or an immune challenge. <a>The birds were rotated
every two weeks starting at 10 weeks of age so that each group experienced each
of the three treatments in a balanced Latin square design. The last treatment
period was at 14 weeks of age.</a> Birds were harvested at the Purdue Boiler Maker Butcher Block where several
meat quality measures (feather retention force, pH, color, fatty acid
composition and drip loss, among others) were recorded. There were no
significant differences in fatty acid composition (<i>P</i> > 0.05) across treatment groups for any of the 38 fatty acids
tested. There were also no significant differences in percent protein (<i>P </i>< 0.05) among treatment groups.
Initial pH values were significantly different between treatment groups (<i>P</i> < 0.01), which corresponded with
the significant differences in other meat quality attributes such as lightness
(L*) and shear force (tenderness) values. Results indicate that even a short
heat stress period lasting for 120 min can affect certain aspects of meat
quality. Similarly, vaccination with hemorrhagic enteritis vaccine one week
prior to slaughter also affects some meat quality measures.</p>
<p>To examine the relationship
between non-aggressive pecking behavior and meat quality, turkey behavior was
video-recorded at 14 weeks of age prior to any of the treatments that week.
Video footage was analyzed to determine the number of aggressive and
non-aggressive pecks given and received by each bird in the room. Aggression
occurred too infrequently to be able to examine the relationship between
aggression and meat quality. Therefore, analyses were only performed using
non-aggressive pecking behavior. From these data, turkeys were given a rank
that was calculated by dividing the number of non-aggressive pecks given by the
number of non-aggressive pecks received. Ranks were standardized for the number
of turkeys in each room. A cluster analysis was performed to categorize the
birds into low, medium, and high groups based on their frequency of pecking. Clusters
were tested to verify that they were significantly different from one another.
Once each turkey had been assigned to a cluster, meat quality measures were
compared among clusters to determine the relationship between non-aggressive
pecking and meat quality. There was a trend (<i>P</i> < 0.10) for L* (lightness) and drip loss to differ among
clusters; however, post hoc analysis did not reveal any significant
differences. There were no significant differences (<i>P </i>> 0.05) among clusters for any other meat quality attributes.
Therefore, turkeys’ tendency to perform and receive non-aggressive pecks does
not seem to have an effect on the meat quality attributes tested in this study.
Research with other species has indicated a relationship between other behavioral
characteristics such as aggressive interactions, fear responses, social rank,
body weight, and meat quality; therefore, future research examining other
behavioral traits will be valuable in examining factors that can influence
turkey meat quality.</p><div><div><div>
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