EFFECTS OF MELATONIN ON PHYSIOLOGICAL RESPONSES OF BROILER CHICKENS TO CONTINUOUS LIGHTING, HEAT AND ROAD TRANSPORTATION STRESSES DURING THE HOT-DRY SEASON
EFFECTS OF MELATONIN ON PHYSIOLOGICAL RESPONSES OF BROILER CHICKENS TO CONTINUOUS LIGHTING, HEAT AND ROAD TRANSPORTATION STRESSES DURING THE HOT-DRY SEASON
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Date
2012-11
Authors
SINKALU, Victor Olusegun
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Abstract
Experiments were performed with the aim of determining the impact of heat and
transportation stresses on the behavioural, physiologic responses and performance of
broiler chickens, administered with melatonin during the hot-dry season in the Northern
Guinea Savannah zone of Nigeria. Broiler chicks were assigned randomly into three
groups, comprising 100 chicks each. Group I was raised under natural photoperiod of 12
h light and 12 h darkness, without melatonin supplementation. Group II was kept under
24-h continuous lighting, without melatonin administration. Group III was raised under
24-h continuous lighting, with melatonin supplementation at 0.5 mg/kg per os, via
drinking water. Melatonin was administered once daily for 56 consecutive days at 17:00
h from 2nd April to 29th May, 2010. The weekly mean temperature-humidity index
recorded inside the poultry house was lowest at week 4 of the study, with the value of
48.60 ± 0.08 oC, but highest at week 1, with the value of 53.48 ± 0.97 oC (P < 0.0001).
On day 42, the mean value of body weight of 2420 ± 50 g/bird was obtained in group III
birds, while values recorded in groups I and II broilers were 1470 ± 30 g/bird and 1907 ±
38 g/bird, respectively. Dry-bulb temperature was negatively, but significantly (P < 0.01)
correlated with feed consumption in groups I (-0.633), II (-0.597) and III (-0.615) broiler
chickens. The Giemsa’s, Leishman’s and Wright’s staining methods, successfully used in
the laboratory for the first time in the present study, showed broilers’ heterophils,
lymphocytes, eosinophils, monocytes and basophils. The least erythrocyte, haematocrit,
haemoglobin and mean corpuscular volume, but highest values of red cell distribution
width were obtained in group I birds. The highest heterophil:lymphocyte ratio was
obtained in group II birds. The significantly (P < 0.05) highest value of mean corpuscular
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haemoglobin was obtained in group III. The overall mean hourly rectal temperature value
of 41.50 ± 0.02 oC, obtained in the group I birds was significantly higher (P < 0.001) than
the value of 41.14 ± 0.04 oC recorded in group III, but lower than that of 41.65 ± 0.02 oC
obtained in group II birds. The diurnal variation in osmotic fragility of erythrocytes from
the birds was highest in group II broilers, followed by those in group I and lowest in the
group III broiler chickens. The overall value of 21.83 ± 1.01 % for panting obtained in
group III birds was significantly (Kruskal Wallis Test = 17.45; P < 0.0001) lower than the
values of 69.72 ± 6.77 % and 67.87 ± 7.19 %, recorded in birds from groups I and II,
respectively. The post-transportation malondialdehyde concentration of 2.99 ± 0.20
μmol/ml and 2.57 ± 0.21 μmol/ml recorded in groups II and III, respectively were
significantly (P < 0.05) higher than the corresponding pre-transportation values.
Aspartate aminotransferase, alanine aminotransferase, creatine kinase and alkaline
phosphatase activities rose significantly (P < 0.05) after transportation in all the groups.
However, the activities of the endogenous enzymes, with the exception of super oxide
dismutase in group III birds, were not significantly (P > 0.05) altered by road
transportation. The trend of results obtained demonstrated that melatonin administration
to broiler chickens enhanced their growth and productivity. It is concluded that melatonin
administration alleviated the deleterious effects of continuous lighting and heat stress on
broilers. Its oral administration prior to road transportation may enhance the survival and
health status of broiler chickens in the tropical zones of the world.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE
STUDIES, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA.
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF
THE DEGREE OF DOCTOR OF PHILOSOPHY IN VETERINARY
PHYSIOLOGY
DEPARTMENT OF PHYSIOLOGY,
FACULTY OF VETERINARY MEDICINE,
AHMADU BELLO UNIVERSITY,
ZARIA, NIGERIA
NOVEMBER, 2012
Keywords
EFFECTS OF MELATONIN, PHYSIOLOGICAL RESPONSESBROILER CHICKENS, CONTINUOUS LIGHTING, HEAT AND ROAD TRANSPORTATION, STRESSES, HOT-DRY SEASON