PSXI-26 Nutragen and Smart Shading improved feedlot performance of <i>Bos indicus</i>-influenced cattle fed in tropical environment

Abstract The magnitude of deleterious consequences derived from heat stress on performance is often disregarded in tropical feedlots operations. Structural enhancement such as proper shading design (Smart Shading) may mitigate heat load, likewise specific feed additives as Nutragen. Thus, the study examined the impact of shade access (3 m2/animal) and NutraGen [9 g/100 kg body weight (BW)] supplementation on feedlot performance of Bos indicus (predominantly Nellore) cattle in a tropical environment (Altair, Sao Paulo, Brazil; Latitude -21.31) from January to April 2020 (spring to summer, 88 d of feeding period). Uncastrated yearling bulls (n = 96), weighing 355.99 ± 1.02 kg at 24 mo of age were divided into four pens, each equipped with electronically monitored feed bunks and scales to measure DMI (kg/d) and water intake (WI, L/d) individually. The ADG (kg/d), feeding efficiency (FE), and meal size (MS, kg/meal) were calculated posteriorly. A complete randomized design with a 2 x 2 factorial arrangement was used, and treatments were: non-supplemented and no shade (NN), non-supplemented and shade (NS), supplemented and without shade (SN), and supplemented and with shade (SS). Air temperature and humidity, irradiance solar, radiant temperature, wind and direction speed, and rain were recorded continuously. All analyses were performed in SAS 9.4, and the experimental unit was the animal. To summarize environment variables, an environmental index (In_Comfort Index, InC) was developed using Principal Components (HPPRINCOMP Procedure) combined with an unsupervised learning algorithm (k-means, HPCLUS Procedure) to build on membership function value analysis (ranging from 0 to 1, the higher, the greater heat stress). Generalized Additive Models (GAM Procedure) were used to visualize the relationship between animal performance, days on feed and InC, while GLM Procedure and Tuckey (P &amp;lt; 0.01) were utilized for variance analyses (significant main effects interactions). The SN presented the least DMI (10.28 kg/d), especially during initial 30 d, compared with 11.66, 11.64 and 11.06 kg/d, for NN, SS and NS, respectively (Figure 1). When InC was above 0.65, DMI decreased greatly in pens without shade. The WI increased accordingly to the increase of InC, greater in pens without shade (NN and NS) 42.7 and 42.21 L/d (respectively), while SS presented the least (32.92 L/d). The SN presented the greatest ADG (1.73 kg/d) compared with SS (1.68 kg/d), NS (1.63 kg/d) and NN (1.60 kg/d). Additionally, all treatments presented decreased ADG pattern when InC was superior to 0.75. Regarding FE, SN were more efficient (0.18) the entire experimental period, while the other treatments presented similar FE. The NN and SS presented larger MS (2.03 and 2.02 kg/meal, respectively) compared with the other treatments (NS = 1.89 and SN = 1.76 kg/meal). In conclusion, Nutragen supplementation and the provision of shade enhanced feedlot performance of Bos indicus-influenced bulls during the warmer period of the year in tropical area.