Linking Cattle, Forage, and Tree Production in Silvopastures

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Virginia Tech

Silvopasture is the intentional integration of trees with forages and livestock. In Blackstone, Virginia a silvopasture management plan was created in a thinned, timber stand seeded with a cool-season forage mixture. Treatment pastures for this study included an open pasture, a thinned pine silvopasture, a thinned hardwood silvopasture, and a cleared and replanted new pine silvopasture. Cattle were introduced in 2017 and rotationally stocked within each pasture according to forage availability. Objectives were to determine the forage availability, forage nutritive value, and the performance of heifers in silvopasture and open pasture systems. Additionally, the new pine silvopasture was grazed to determine the effect of cattle on tree seedlings without protection. Forage availability was affected by date and year and was significantly lower in 2018 (3560 kg ha-1) versus 2017 (5350 kg ha-1). Pre-grazing forage availability was lowest in the pine and hardwood silvopastures in both years (4500 kg ha-1) compared to the open pastures (4920 kg ha-1; p < 0.0001). Date significantly influenced nutritive value, but only had date by treatment interaction in the 2017 grass crude protein and neutral detergent fiber sample. In 2017, the new silvopasture (61% TDN) had greater total digestible nutrients as compared to the open pasture and thinned hardwood silvopasture (57% TDN; p = 0.0292); there was no significant difference (p=0.3733) in total digestible nutrients in 2018 between pastures (58% TDN). In 2017, average daily gains of the heifers were greatest in the silvopastures in June (p = 0.0346). In 2018, average daily gain was lowest among silvopastures later in the summer compared to open pastures and new silvopastures (pJuly = 0.0051; pAugust = 0.0008). Remote temperature loggers were used to collect vaginal temperatures of the heifers over eight days in 2018. Silvopasture heifers had an average core temperature of 39.4 °C from 2-5 PM while heifers in the open pastures had an average temperature of 40.0 °C. A drone with a thermal camera was used to collect external hide temperatures in the morning and afternoon. Heifers in the silvopastures had lower heat loads in the afternoon while animals without shade experienced a 65% greater temperature increase between morning and afternoon when compared to the shaded animals. Silvopastures provide an opportunity to improve the welfare of grazing livestock in the summer, while improving the overall productivity and efficiency of land. Tree seedlings that were planted into pasture to create a new silvopasture experienced a 16% mortality rate while over 75% of tree seedlings had less than 50% damage after two years and would continue to produce trees with future economic and shade value. Future research should focus on how to implement silvopasture as part of a holistic grazing and management plan while continuing to evaluate cattle, forage, and tree response to silvopastures over multiple years.

silvopasture, agroforestry, shade, cattle, tree, forage, heat stress