Assessing the potential of Spirulina Platensis as a protein source and its effect on feed intake, growth performance, carcass yield, internal organs sizes and meat quality of boschveld and potchefstroom koekoek chicken breeds

A thesis submitted in fulfilment of the requirements for the degree of masters of science in agriculture (Animal science)

The potential of Spirulina platensis (SP) as a protein source to replace soybean meal and its effect on feed intake, growth performance, carcass yield, internal organ sizes and meat quality was determined. A 12 weeks feeding trial was conducted using 72 unsexed Boschveld and Potchefstroom Koekoek chickens. The chickens were fed with commercial starter crumbles from day 1 to week 4. At week 5 of age, the chickens were randomly assigned to one of four dietary treatments which were as follows; 0%SP, 5%SP, 10%SP and 15%SP of dried Spirulina platensis powder as a replacement of soybean meal, with six replicates per treatment and three per breed. The feeding experiment excluding brooding period lasted for 12 weeks. Feed intake data were collected daily, and live weights were taken weekly for growth performance. The results showed that feed intake responded negatively to increase in Spirulina inclusion level. Chickens on treatment 0%SP had higher weights (P˂0.05) which was not affected (P˃0.05) by the breed. The breed significantly affected (P˂0.05) average daily gain (ADG) where BV had a higher ADG compared to PK. The feed conversion ratio was highest (P˂0.05) in chickens on diet 10% SP; with a mean value of 1.03 and the lowest in 0% SP with the value of 0.98. Birds on diet 0%SP recorded the highest (P<0.05) protein efficiency ratio PER (0.91) while those on diet 15%SP had the least PER (0.57). The results showed that dietary treatment x breed interactions did not (P˃0.05) affect the gizzard, spleen, heart, liver and intestines weights and carcass yield. However, the breed of the chicken affected the spleen size, in which Potchefstroom Koekoek chickens recorded heavy spleen weight (P˂0.05) than Boschveld. Treatment diets significantly ii influenced (P˂0.05) breast muscle and thigh weight of the chickens. The treatment diets affected (P˂0.05) the coliform and Lactobacillus counts of the cecum. The coliform counts decreased significantly with an increase in Spirulina inclusion in the diet while Lactobacillus counts increased significantly with increasing level of Spirulina in the diet. The inclusion of Spirulina in the grower diet did not (P˃0.05) influence the meat physiochemical quality of the chickens but compromised some eating quality parameters such as flavor and initial and sustained juiciness. A prominent chicken flavor (P˂0.05) was recorded in chickens fed the control diet while chickens fed Spirulina had less chicken flavor. In conclusion, increasing Spirulina level in the diets negatively affected feed intake, body weights, PER, breast muscle and thigh weights and chicken flavor of the meat. Increasing Spirulina in the diets also resulted in high FCR, increased Lactobacillus counts and reduced coliforms. Based on these results, it is therefore best if only up to 5% Spirulina can be included in the diets for indigenous chickens. However, Spirulina was found to have high protein content but its inclusion at high levels negatively affected feed intake, meat flavor and acceptability of the meat. There is need to further investigate lower inclusion levels of Spirulina platensis and their effect on chicken production parameters and meat quality