Abstract. High stocking density (HSD) and heat stress (HS) caused by climate change can
lower blood homeostasis and negatively impact the behavioral traits of animals. The
objective of this study was to explore the influence of stocking densities on
behavioral traits, blood parameters, immune responses, and stress hormones in
meat ducks (Cherry valley, Anas platyrhynchos) exposed to HS. A total
of 320 meat ducks were assigned to four groups with different stocking
densities using a randomized complete block design. The ducks were then reared for 42 days.
The assigned density groups were as follows: (1) control group (CON,
three birds m−2, normal environmental heat conditions); (2) low stocking
density (LSD, three birds m−2, heat stress conditions); (3) medium stocking
density (MSD, four birds m−2, heat stress conditions); and (4) high
stocking density (HSD, six birds m−2, heat stress conditions). To induce
HS, the environment of the poultry house was set to a temperature of 34±2∘C with a relative humidity of 70 % from 11:00 to 16:00 for the finisher period (from day 22 to day 42 of the rearing period).
Concentrations of blood triacylglycerol, total cholesterol, low-density
lipoprotein cholesterol (LDL-C), aspartate aminotransferase (AST), and
alanine aminotransferase (ALT) were higher in the HS groups compared with
the CON group, with HSD showing the highest levels (P < 0.05).
The concentrations of high-density lipoprotein cholesterol (HDL-C) and glucose were lower in the HSD groups than in the
CON group (P<0.05). Red blood cell (RBC) and platelet (PLT) counts were
lower in HS groups compared with the CON group, with the HSD group displaying the lowest
counts (P<0.05). Blood pH values were also higher in the HS groups than
in the CON group, with the highest values observed in the HSD group (P<0.05).
Concentrations of blood
pCO2, HCO3, and TCO2 were higher in the HS groups than in the CON group, with
HSD showing the lowest levels (P<0.05). The concentration of
PO2 was higher in CON than in any of the HS groups, with the lowest levels found in the HSD
group (P<0.05). The concentrations of blood IgG and
corticosterone were increased in the HS groups compared with the CON group (P<0.05). Animal behavioral trait scores were also higher in HS groups
than in the CON group (P<0.05); these scores were the highest in the HSD group.
Overall, animal behavioral traits, blood biochemical parameters, and immune
responses in meat ducks exposed to heat stress were highest in the HSD group, but
not significantly different between the LSD or MSD groups.
Effect of stocking density on behavioral traits, blood biochemical parameters and immune responses in meat ducks exposed to heat stress
