Provision of Additional Cup Drinkers Mildly Alleviated Moderate Heat Stress Conditions in Broiler Chickens.

Sixty-four broilers of a commercial strain in a 2 × 2 factorial design with two environmental conditions: normal (N; 20°C, 50% RH) or MHS (30°C, 70% RH for 6 h/day for 3 consecutive days), and two drinker treatments; standard (B; a bell drinker/pen) or additional (A; as B + two cup drinkers). Each treatment had 16 birds with half of them implanted with temperature-ID chips to estimate the change in core body temperature (ΔCBT). Comb (CT) and feet (FT) temperatures were measured with atemperature probe, behavior was recorded with digital cameras, daily weight gain, feed intakes and litter moisture content (LMC) were also monitored. Data were subjected to General Linear Model (GLM) analysis. MHS broilers had greater ΔCBT, CT, and FT and more time spent panting and drinking compared to N broilers. Provision of additional cup drinkers reduced ΔCBT but enhanced heat loss from the comb and feet. At 6HS, MHS birds showed a tendency to spend more time drinking from the cup drinkers compared to N birds without compromising LMC. MHS suppressed feed intake and not weight gain.

Elevated levels of the stress hormone, corticosterone, cause 'pessimistic' judgment bias in broiler chickens.

Pessimistic judgment biases, whereby humans or non-human animals interpret ambiguous information negatively, are hypothesised to be one of the suite of adaptive changes that comprise the vertebrate stress response. To test this hypothesis, we asked whether experimentally elevating levels of the glucocorticoid stress hormone, corticosterone, in broiler chickens produced a pessimistic judgment bias. We trained young chickens to discriminate a stimulus (paper cone) placed at two locations in an arena, one associated with reward (mealworms) and one with punishment (air puff). During seven days of non-invasive administration of either corticosterone or vehicle control, we tested the birds' responses to the cone placed at ambiguous locations between the trained locations. Corticosterone-treated birds were more likely than controls to respond as if punishment was likely when the cone was placed near to the punished location. The degree of this 'pessimism' was associated with smaller relative spleen weight, which is a documented consequence of chronic stress in chickens. We conclude that changes in corticosterone levels in chickens are sufficient to cause a specific change in decision making, dubbed 'pessimism', whereby corticosterone-treated birds showed an increased expectation of punishment in the face of ambiguous information. Pessimism could be a useful welfare indicator in chickens.

Ultrasonographic evaluation of the pre-pubertal development of the reproductive tract in beef heifers.

To study the development of the reproductive tract in heifers, the ovaries, uterus, cervix and vagina were examined by transrectal ultrasonography every 2 weeks, from 2 to 60 weeks after birth. First ovulation occurred at 63.7 +/- 1.1 weeks of age. Ovarian dimensions increased rapidly from 2 to 14 weeks of age, and increased again after 34 weeks of age (P<0.05). The size of the largest ovarian follicles increased from 8 to 14 weeks of age, from 38 to 42 weeks of age, and finally from 52 to 60 weeks of age (P<0.05). The number of follicles > or =3 mm in diameter tended to increase from 6 to 14 weeks of age (P<0.10) and increased significantly from 6 to 60 weeks of age (P<0.05). Mean numerical pixel values of the ovarian images decreased from 4 to 26 weeks of age, and then rose to 44 weeks of age (P<0.05). Diameter of the uterine body, cervix and vagina increased from 2 to 20-24 weeks of age, and again after 32 weeks of age (P<0.05). Mean numerical pixel values for the uterus and vagina decreased initially (uterus: 4-8 weeks and vagina: 6-22 weeks of age) and then increased (uterus: 14-42 weeks and vagina: 22-32 weeks of age; P<0.05). Pixel heterogeneity showed a consistent peak at 20-22 weeks of age for the uterus, cervix and vagina (P<0.05). In summary, in the heifer calf, the marked growth of the reproductive tract in the first few months of age, and prior to first ovulation, reflects phases of increased ovarian follicle (> or =3 mm in diameter) numbers and size. Ultrasonographic image analysis revealed patterns of numerical pixel values and heterogeneity that may be useful in determining important stages of growth and differentiation of the reproductive system.