Sows-Gilts Stocking Rates and Their Environmental Impact in Rotationally Managed Bermudagrass Paddocks

Abstract

Ground cover maintenance and nutrients management are key elements to reduce the environmental impact of outdoor swine production. The objective of this study was to determine the effects of sows-gilts stocking rates on vegetative ground cover and soil nutrient concentrations in rotationally stocked bermudagrass (Cynodon dactylon L. Pers) pastures. Three stocking rates (10, 15 and 25 sows-gilts ha−1) were compared during three 8-week grazing periods. Increasing the stocking rate from 10 to 25 sows-gilts ha−1 decreased the ground cover of the paddocks from 65 to 48%, and increased soil nutrient concentrations (ammonium 47%; nitrate 129%; phosphorus 53%; zinc 84%; and copper 29%).

A Comparison of Stocking Methods for Pasture-Based Growing-Finishing Pig Production Systems

“…As a consequence of foraging pigs activity, mainly rooting, ground cover endured damage [ 53 ]. As in previous studies [ 14 , 15 , 16 ], the sites where pigs tended to congregate, such as resting, feeding and wallowing areas, showed a greater impact. In the present study, however, at the end of the 12-week grazing periods the ground cover was over 66%, greater than the ground cover (8% to 27%) reported by Kongsted and Jakobsen for pigs grazing (338 m 2 pig −1 , 30 pigs ha −1 ) a multispecies pasture including grass—clover and forage herbs for a similar period of time [ 53 ] and greater than the final ground cover recorded for bermudagrass pastures [ 16 ].…”

“…As soil bulk density increases as a result of pig trampling, it could be reasonable to assume that pigs under continuous stocking, being free to use the whole area at will, would tend to concentrate their activity in already-used areas, thus increasing their bulk density. Pigs tend to concentrate in areas adjacent to shelters, feeders and drinkers and patch-perpetuating behavior has been previously observed [ 15 ]. Similarly, Bordeaux et al reported greater bulk density in pastures managed with pigs under a stationary scheme, compared to the bulk density of paddocks where service structures (shelter and water) were moved weekly [ 18 ].…”

“…Soil bulk density was greater deeper in the soil, while humic matter concentrations and exchangeable acidity showed higher values in the topsoil layer (0 to 15 cm). These differences could be attributed to the deposition of manure and organic matter to the surface of the ground [ 15 ]. The addition of organic matter has also been related with lessened bulk density [ 40 ].…”

“…The concentration of NO 3 − , P, K, S, Mn, Zn, Cu, Na and Fe varied among the soil layers with greater values found in the top 0 to 15 cm layer for most of the nutrients but for Fe which presented higher values on the bottom strata of the explored soil profile (15 to 30 cm). Previous studies have reported vertical displacement of soil nutrients [ 15 , 36 , 43 ]. Grazing pigs deposit dung and urine on the surface of the paddocks.…”

“…Pietrosemoli and Green advocate for management of grazing pigs that focus on the main impacts that this animal species could have on pastures [ 4 ]. This implies that minimizing ground cover disappearance [ 13 , 15 , 16 ], decreasing the damage to the soil structure [ 17 , 18 , 19 ], reducing buildup of soil nutrients [ 8 , 15 , 16 , 20 ] and enhancing soil nutrients distribution [ 9 , 13 , 15 , 16 , 21 ] should be taken into consideration when designing the pasture management plan.…”