Simulating the Effects of Beef Cattle Stocking Rate on Bermudagrass Forage Growth and Stocker Gain as Influenced by Climate Variability and Management Strategy
In the southern United States, beef cattle production on pastures is a key economic activity. Here, bermudagrass [Cynodon dactylon (L.) Pers.] is a commonly used warm-season perennial grass for pastures. Stocking rate (SR) is a key management variable affecting forage growth and animal performance. Climate variability is a major environmental phenomenon significantly impacting agriculture in this region. Because of complex relationships between grazing systems and the environment and due to the lack of an effective investigative tool, the impacts of SR on bermudagrass forage growth and beef cattle (stocker) performance as influenced by climate variability and soil moisture condition in this region are unknown. Using a forage-animal interface model and the historical weather data spanning 76 years (1950-2025) collected at Overton, Texas, this study assessed the effects of: 1) SR on bermudagrass herbage mass (HM), the grazed HM per unit of pasture (GHM_P) and animal (GHM_A), and the seasonal weight gain (SWG) and average daily gain (ADG) of stockers as influenced by El Ni？o-Southern Oscillation (ENSO) and soil moisture condition in this region; and 2) drought on these variables as influenced by SR. Simulations were performed for 456 scenarios, comprising 76 years × 3 SRs (5, 8, and 11 hd？ha？1) × 2 moisture conditions (rainfed and irrigated). Results showed that the effect of SR on GHM_P, GHM_A, SWG, and ADG each was significant under all ENSO phases and moisture conditions (p < 0.05). However, the SR effect on HM was significant only under irrigated conditions. In significant cases, the values of HM and GHM_P increased, whereas those of GHM_A, SWG, and ADG decreased with an increase in SR. The influence of moisture condition on the SR effect was significant, whereas the influence of ENSO was not. Results further showed that, regardless of SR, the HM loss due to drought increased exponentially with an increase in drought severity. The drought-induced losses of GHM, SWG, and ADG showed similar trends. But the losses became more evident with an increase in SR.
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