Developmental history and stress responsiveness are related to response inhibition, but not judgement bias, in a cohort of European starlings (Sturnus vulgaris)

Judgement bias tasks are designed to provide markers of affective states. A recent study of European starlings (Sturnus vulgaris) demonstrated modest familial effects on judgement bias performance, and found that adverse early experience and developmental telomere attrition (an integrative marker of biological age) both affected judgement bias. Other research has shown that corticosterone levels affect judgement bias. Here, we investigated judgement bias using a modified Go/No Go task in a new cohort of starlings (n = 31) hand-reared under different early-life conditions. We also measured baseline corticosterone and the corticosterone response to acute stress in the same individuals. We found evidence for familial effects on judgement bias, of a similar magnitude to the previous study. We found no evidence that developmental treatments or developmental telomere attrition were related to judgement bias per se. We did, however, find that birds that experienced the most benign developmental conditions, and birds with the greatest developmental telomere attrition, were significantly faster to probe the learned unrewarded stimulus. We also found that the birds whose corticosterone levels were faster to return towards baseline after an acute stressor were slower to probe the learned unrewarded stimulus. Our results illustrate the potential complexities of relationships between early-life experience, stress and affectively mediated decision making. For judgement bias tasks, they demonstrate the importance of clearly distinguishing factors that affect patterns of responding to the learned stimuli (i.e. response inhibition in the case of the Go/No Go design) from factors that influence judgements under ambiguity

Physiological responses and performance of broiler chickens offered olive leaf extract under a hot humid tropical climate

This study was designed to determine the effects of olive leaf extract (OLE) supplementation in the drinking water on growth performance, hematological parameters, plasma triiodothyronine and malondialdeyde, superoxide dismutase, and rectal temperature of broiler chickens under a hot-humid tropical climate. Two hundred and forty Arbor acre broiler chickens were used for this experiment and were allotted to four treatments comprising four replicates of 15 birds each. The birds were offered OLE per liter of water at various levels (0, 5, 10, or 15 mL) in a completely randomized design. Rectal temperature (RT), hematological indices, weight, weight gains, feed consumed, feed conversion ratio, and plasma triiodothyronine (T3) were the parameters measured. The results obtained showed that the plasma T3 of the birds offered 15 mL OLE was higher (P < 0.05) than those of the birds in the other treatment groups. Significant differences (P < 0.05) were observed in the feed intake (DFI), total feed intake (TFI), final weight (FW), total weight gain (TWG), and feed conversion ratio (FCR) among treatments. The DFI, TFI, FW, TWG, and FCR of broilers offered 15 mL OLE were significantly (P < 0.05) better than those offered the 10 mL and 5 mL levels. It was concluded that inclusion of 15 mL of OLE enhanced the performance of broiler chickens during the hot dry season