and balancing the diet appropriately for age and type of chickens reared, etc.


Immune response Immune response data are presented in Table 2. The total NDV antibody titer showed the highest concentration in the alternative green-blue light group compared to other groups, while no difference was noted in the circulating thyroid hormones (T3) and (T4) among birds reared under different light colours. The increased concentration of NDV should protect from clinical Newcastle disease, although it may not prevent virus shedding from the trachea.


Hematological traits Hematological measurements (red blood cells, white blood cells, hematocrit value, hemoglobin and platelets) under dif- ferent light treatments are shown in Table 3. An increase in the red blood cell count was seen under the yellow light treatment with a resulting increase in the hematocrit value that was ultimately reflected in a better growth response at five weeks of age compared to the other light treatments. The improved performance under the yellow colour treatment may also be attributed to the higher platelet level found in this case, helping to improve the general condition of the bird by acting on digestion, destroying bacteria, increasing the secretion of chemicals that attract neutrophils and mono- cytes to sites of inflammation, as well as growth factors to maintain the lining of blood vessels.


Other management factors Another study was conducted to examine the performance of chickens reared under five different colour lighting schemes with three bird densities. It was shown that broilers reared under mixing blue-green light at the density of 12 bird/m2 had significant positive effects on growth performance com- pared to other lighting programmes and bird densities (see Table 4). The reduced performance under high stocking densi- ty for each light colour treatment, even with the blue-green light, may be attributed to the following factors: • A general tendency towards a reduced growth rate with increasing stocking density, not only because of the reduced feed intake under such conditions but also because of the loss of feed energy due to immunological responses and other physiological adjustments. The reduced growth rate may further be attributed to the disruption in gut micro- flora that aids in digestion, the absorption of nutrients and improvement of the intestinal micro-architecture. • High stocking density affecting the microbial profile of the litter with more toxins produced. Toxins affect the utilisation of feed nutrients for growth and other biological functions. • Increased stocking density leading to increased levels of airborne dust and hence more respiratory disease challenges which can lead to the incidence of other problems.


Green light stim- ulates the growth of birds at an early age and switching to a different light colour at 10 or 20 days of age may further stimulate growth.


In these situations, the birds may not exhibit their full produc- tion potential, especially when reared under monochromatic light conditions. The same applies to other factors which can negatively affect performance, such as poor nutrition, an adverse microclimate, disease outbreaks, or inadequate biosecurity plans.


References available on request.


Table 3 – Hematological analysis of broilers under different lighting. Treatment


Red


White light Blue light Red light


Green light Yellow light


White


Blood Cells Blood Cells (106/μL) 2.40 2.42 2.49 2.44 2.70


Growth response 763 Source: M. J. Kim and others (2013)


Table 4 – Effects of light colour and stocking density on body weight of broilers at 5 weeks.


Stocking density White (bird/m2 12 15 18


)


1,560.7 1,453.3 1,260.6


Source: R. K. Mosa and others (2015) ▶ ALL ABOUT FEED | Volume 30, No. 3, 2022 31


1,633.1 1,440.6 1,406.7


1,651.9 1,571.4 1,460.2


1,622.2 1,540.8 1,497.8


1,744.9 1,704.8 1,700.7


Red Blue Green Blue-Green


(103/μL) 1.13 0.90 1.07 0.84 0.98 769


Hematocrit Hemoglobin value (%)


26.01 26.77 27.78 26.74 29.56 743


(g/dL) 8.65 8.40 8.76 8.44 8.59 785


Platelets


(103/μL) 23.10 18.89 26.89 18.43 28.56 831


PHOTO: JAN WILLEM SCHOUTEN


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