Rotational Stocking of Tifton 85 Bermudagrass and Supplementation Level Effects on Performance of Replacement Dairy Heifers

Use of Tifton 85 bermudagrass [Cynodon dactylon (L.) Pers. X C. transvaalensis Burtt Davy] has increased in pasture-based dairies in the southeastern United States relative to other warm-season grasses. A 2-yr study was conducted to evaluate rotational stocking for two grazing rest periods (RP; 14 and 21 d) and two supplementation rates (SUP; 0.64% [low] and 0.96% [high] of heifer [Bos taurus] body weight) on pasture characteristics and animal performance. Across all treatments, pastures with 14-d RP had greater (P < 0.05) crude protein (CP) concentration and in vitro organic matter digestibility (IVOMD) than pastures with 21-d RP (174 vs. 161 g kg(-1) and 624 vs. 602 g. kg(-1), for CP and IVOMD, respectively). Herbage allowance was less in high than low SUP pastures (0.59 vs. 0.67 kg dry matter (DM) kg live weight (LW)(-1), respectively). In 2010, average daily gain (ADG) was not affected by SUP (0.62 vs. 0.63 kg d(-1) for heifers fed low and high amounts of SUP, respectively) or by RP. However, in 2011 ADG was greater (P = 0.07) for heifers fed high compared to low amounts of SUP (0.61 vs. 0.51 kg d(-1), respectively). Although heifer ADG approached the industry target of 0.7 kg, results suggest forage allowance of < 1 kg DM kg(-1) animal LW limited daily gains. The nutritive value data support the conclusion that Tifton 85 possesses high nutritive value and is suitable for use in pasture-based systems for raising replacement dairy heifers if adequate forage allowance is maintained.