<p>  Broiler chickens are routinely exposed to various conditions, such as heat stress and stocking density, which may negatively influence their welfare status. This study examined the influence of a commercially available proprietary phytogenic feed additive (Probiotech International, Inc.) on welfare measures, environmental measures, productivity, body temperature, and behavior of commercial broiler chickens. Two flocks (Trials 1 & 2) utilized a total of 1,650 Ross 708 broilers housed in two separate rooms with floor pens at Purdue University’s ASREC Poultry Unit. </p> <p>  Trial 1 birds (n = 750) were divided into 20 separate pens (5 pens/treatment): PHD: phytogenic supplementation and raised at standard industry stocking density (37 kg/m²), PLD: phytogenic supplementation and raised at a lowered stocking density (27 kg/m²), CHD: control diet and raised at standard industry stocking density, and CLD: control diet and raised at a lowered stocking density. Due to the aromatic properties of the phytogenic additive, PHD and PLD birds were housed in one room and CHD and CLD birds were housed in another room. The feed supplement was mixed in at an inclusion rate of 0.25 g/kg. Phytogenic supplementation began at 15 d, coinciding with feeding the grower diet, and continued until 42 d when the study concluded. Heat stress was applied to all birds from 30 to 32 d, where the peak temperature did not exceed 34.4ºC. Welfare measures (gait, footpad dermatitis, hock burn, and feather cleanliness) and litter quality were assessed at 27 d and 39 d. Ammonia concentrations were measured at 35 d and 39 d. Productivity (body weight, feed intake, and feed conversion ratio) was measured weekly. Body temperature via thermography of the eye surface was collected at 29, 32, and 34 d. Behavior data were collected at the following periods for 2 continuous days: 23-24 d (Period 1), 31-32 d (Period 2), and 36-37 d (Period 3). </p> <p>  Trial 2 birds (n = 900) were assigned to 25 separate pens (5 pens/treatment) with the same groups as Trial 1, with an additional group (MHD): control diet, housed in the same room as PHD and PLD birds, and raised at standard industry stocking density. Phytogenic supplementation was provided as in Trial 1. Heat stress was again applied to all treatments from 30 to 32 d, where the peak temperature did not exceed 31ºC. Welfare measures and litter quality were collected at 27 d and 38 d. Ammonia concentrations were measured at 27, 31, and 38 d. Productivity was measured from 15 d to 27 d (grower phase), and 27 d to 38 d (finisher phase). Body temperature via cloacal temperature recording occurred at 29, 31, and 33 d. </p> <p>  Welfare data and litter quality were analyzed using PROC LOGISTIC (SAS 9.4); productivity data were analyzed using PROC MIXED (SAS 9.4); behavior data were analyzed using PROC GLIMMIX (SAS 9.4); and eye surface temperature, cloacal temperature, and ammonia concentration were analyzed using a nested mixed model found in the afex package using R (version 4.2.1) and R Studio (R Foundation for Statistical Computing). All statistical differences were considered significant when P < 0.05. Results of Trial 1 indicated that phytogenic supplementation significantly influenced hock burn and feather cleanliness, body weight and feed conversion ratio, ammonia concentration, as well as Period 1 sitting, Period 2 drinking, preening, standing, and wing spreading, and Period 3 drinking, preening, sitting, standing, and walking behaviors. Results of Trial 2 indicated that diet had no effect on any measured parameter. The variation in results suggests that factors such as stocking density or management strategies influenced the measured parameters, rather than diet alone. More research is needed to understand the specific effects of phytogenic feed additives, social and environmental stressors and whether phytogenic feed additives can improve bird performance and welfare under longer heat stress periods.</p>

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