Cattle performance and production when grazing bermudagrass at two forage mass levels in the Southern Piedmont

¹ USDA-Agricultural Research Service, J. Phil Campbell Sr. Natural Resource Conservation Center, Watkinsville, GA 30677

^* To whom correspondence should be addressed. E-mail: afranz{at}uga.edu.

	Abstract

Performance and production of growing cattle (Bos taurus) on 'Coastal' bermudagrass [Cynodon dactylon (L.) Pers.] pasture are affected by forage allowance, but possible interactions with fertilizer nutrient source (i.e., inorganic vs. organic) and time have not been well described. We evaluated 3 nutrient sources with equivalent N rates [inorganic, crimson clover (Trifolium incarnatum L.) cover crop plus inorganic, and chicken (Gallus gallus) broiler litter] factorially arranged with 2 residual forage mass levels [grazing to maintain high (4,528 ± 1,803 kg/ha) and low (2,538 ± 1,264 kg/ha) forage mass] on cattle stocking density, ADG, and BW gain during 5 consecutive summer grazing seasons. Across grazing seasons, residual forage mass and nutrient source both affected response variables, but interactions between these variables were rarely significant (P < 0.10). Across grazing seasons and nutrient sources, increasing grazing pressure to maintain lower forage mass reduced ADG (0.67 vs. 0.88 kg/d; P < 0.001), but increased BW gain/ha (726 vs. 578 kg/ha; P < 0.001) due to higher stocking density (8.7 vs. 5.8 steers/ha; P < 0.001; mean BW of growing Angus steers of 212 kg). Inorganic fertilization led to greater stocking density than other nutrient sources (8.2 vs. 6.8 steers/ha; P < 0.001), because of greater forage production. Stocking density to achieve the 2 targeted forage mass levels was widely different during initial grazing seasons of the study, but nearly similar at the end of 5 yr. Cattle performance tended to decline with time during each grazing season under both residual forage mass levels, perhaps as a result of declining forage quality, because performance was positively associated with grazing season precipitation under high forage mass. Steer BW gain/ha was greater (P < 0.05) with lower forage mass early in the grazing season of all years, but not necessarily later in the grazing season. Steer BW gain/ha was also greater (P < 0.05) with lower forage mass during early years of the study, but similar during later years of the study. Significant variations in cattle performance and production with time confirmed short-term seasonal effects, but suggested that long-term effects may also be of importance in maintaining productivity and environmental quality of grazed pastures.

Key Words: broiler litter, cattle production, daily gain, grazing pressure, inorganic fertilizer, stocking density