Physiological and haematological responses of broiler chickens offered cold water and vitamin C during hot-dry season
The effects of cold water and vitamin C on broilers’ rectal temperature (RT), respiratory rate (RR) and haematological parameters were evaluated during dry season. Two hundred and sixteen 4-week-old Anak 2000 broilers fed ad libitum were offered either water at ambient temperature (29.5oC; ORD) or cold water (8.0oC; COLD) to which either 0 (-C) or 500 mg vitamin C per litre water (+C) was added to give four treatment groups (ORD-C, ORD+C, COLD-C and COLD+C) from week 5 to 8 of age. There were 3 replicates with 18 birds per replicate. RT and RR were taken for three days weekly at 16.00 h. Blood was sampled weekly for haematological, plasma biochemical and triiodothyronine analyses. Data on RT, RR, packed cell volume (PCV), red blood cell (RBC), haemoglobin concentration (Hb), mean corpuscular haemoglobin concentration (MCHC), mean corpuscular haemoglobin (MCH), mean corpuscular volume (MCV), white blood cell (WBC), heterophil (HET), lymphocyte (LYM), eosinophil (EOS), monocyte (MON), heterophil:lymphocyte ratio (H:L), plasma K+, Na+, glucose (GLU), protein (PRO) and tri-iodothyronine (T3) were subjected to ANOVA using least squares method. Water temperature had significant (P<0.01) effect on RT and RR. Cold water lowered RT and RR of the birds compared with water at ambient temperature. Similarly, vitamin C in drinking water caused decrease in RT (P<0.001) and RR (P<0.01) compared to ordinary water. Water temperature had no significant (P>0.05) effect on MCHC, MCH, MCV, LMY, EOS, plasma K+, Na+, GLU, PRO and T3. But cold water significantly lowered MON (P<0.05) and increased PCV (P<0.001), RBC (P<0.001), Hb (P<0.001), WBC (P<0.001), HET (P<0.01) and H: L (P<0.05) when compared with water at ambient temperature. Addition of vitamin C significantly increased LYM (P<0.05) and H:L (P<0.05) but decreased HET (P<0.05) when compared with birds that received no vitamin C. Vitamin C had no significant (P>0.05) effect on PCV, RBC, Hb, WBC, MCHC, MCH, MCV, plasma K+, Na+, GLU, PRO and T3. There were significant (P<0.01) interactions between water temperature and vitamin C on HET, LYM and H: L. Broiler chickens offered ORD+C had significantly lower HET and H: L than those offered ORD-C, COLD-C and COLD+C. However, the LYM was highest in ORD+C birds. High HET and H:L, and low LYM are indicators of heat stress in poultry. In conclusion, cold water and vitamin C were effective in reducing broilers’ RT and RR in the afternoon during hot-dry season. Either of the two may improve the well-being of broilers during dry season.
Keywords: cold water; vitamin C; rectal temperature; respiratory rate; broilers