Cognitive performance for 2 strains of broiler birds in homogenous and mixed grouping system

Sixty-day-old chicks from the commercial broiler strain, Vencobb, and 60-day-old backyard Vanaraja chickens, were selected as experimental birds for assessing learning and cognitive performance. Learning and cognitive ability were assessed on the basis of maze trial performance, self-recognition trial (SRT), detour trial (DT), tonic immobility (TI) trial, serum leptin concentration, and encephalization quotient (EQ). The mazes were prepared by using locally available cardboard, papers, and bamboo strips. Three maze trials—T maze trial, Y maze trial, and radial maze trial—were performed. Birds were trained from the second to 10th day for maze tests. The maze test schedules started from 11th day, and data were taken 11th-17th day, 25th-31st day, and 39th-45th day in trial I, trial II, and trial III schedules, respectively. The response of birds to different maze tests and performance in different cognitive trials were assessed on the basis of latency in time to acquire the food and complete the tasks. At the end of the trials, serum leptin concentration was assayed. EQ was calculated by Jerison's formula and Cuvier's formula. Vencobb birds showed a better response to different cognitive and learning trials. In T maze trials, the Vencobb variety performed significantly better (P < 0.05) than Vanaraja birds (trial I, P = 0.001; trial II, P = 0.001; and trial III, P = 0.01). Vencobb birds, when housed in group with Vanaraja birds, performed significantly (P < 0.05) worse in trial I (P = 0.012), trial II (P = 0.020), and trial III (P = 0.045). In the Y maze trial, homogeneously housed Vencobb birds performed significantly better (P < 0.05) than did Vanaraja birds (trial I, P = 0.04; trial II, P = 0.01). Vanaraja birds performed significantly (P < 0.05) better when they were homogeneously housed than mixed housed (trial I, P = 0.10; trial II, P = 0.001; and trial III, P = 0.008). There was significant improvement (P < 0.05) in the performance of Vencobb birds with advancement of age from trial I to trial II in all cases (homogenous group, P = 0.012; mixed group, P = 0.010). Similarly, significant (P < 0.05) improvement in performance was observed in homogeneously housed Vanaraja birds (trial I-II, P = 0.012; trial II-III, P = 0.040) and mixed housed Vanaraja birds (trial I-II, P = 0.042; trial II-III, P = 0.021). In the case of the R maze trial, Vencobb birds (homogenous) performed significantly (P < 0.05) better as compared with Vanaraja birds (homogenous) in all 3 trials (trial I, P = 0.01; trial II, P = 0.001; and trial III, P = 0.03). In homogeneous housing system, the performance of Vencobb birds was significantly better (P < 0.05) than Vanaraja birds in SRT (trial I, P = 0.01; trial II, P = 0.001; and trial III, P = 0.001), whereas Vanaraja birds performed significantly better (P < 0.05) than Vencobb birds in the DT (trial I, P = 0.05; trial II, P = 0.05; and trial III, P = 0.07) and TI trial (trial I, P = 0.02; trial II, P = 0.05; and trial III, P = 0.04). In the SRT test, Vanaraja birds performed significantly better (P < 0.05) in mixed housing than in homogeneous groups (trial II, P = 0.01; trial III, P = 0.01). Vencobb birds showed a significant improvement (P < 0.05) from trial I to trial II in homogeneous and mixed housing (P = 0.04 and P = 0.02). In mixed housing, significant improvement (P < 0.05) in the performance of Vanaraja birds was seen from trial I to trial II (P = 0.001). In DT, homogeneous Vencobb birds (trial I) performed significantly worse (P < 0.05) as compared with mixed grouped birds (P = 0.05). In case of Vanaraja birds, mixed housed birds showed significantly (P < 0.05) better performance than did homogeneous birds (P = 0.001) in trial I. In the TI trial, there was significant improvement (P < 0.05) in the performance from trial I to trial II in homogeneous Vencobb (P = 0.04) and mixed Vanaraja birds (P = 0.05). The EQ maximum was 2.31 in intelligent or superior birds and 1.85 in dull birds. The cognitively superior Vencobb birds showed a significantly higher level of serum leptin concentration than did the dull birds (0.78 ± 0.12 vs. 0.42 ± 0.08 ng/mL, P = 0.02), a result similar to that in Vanaraja birds (1.03 ± 0.13 vs. 0.62 ± 0.06 ng/mL, P = 0.01). It may be concluded that the genetics of the birds affects cognitive and learning ability. Mixed group housing negatively affects the cognitive abilities of birds. Jerison's formula is more highly correlated with brain weight than the traditional Cuvier's equation. With the advancement of age, spatial memory involved in gathering and processing improves.