The Effects of Traditional Endophyte, Endophyte-free, and Novel Endophyte (MAXQ) Jesup Tall Fescue Hay Consumption on Digestion and Nitrogen Retention in Steers.

Abstract

A digestion and nitrogen balance trial was conducted to compare the effects of traditional endophyte-infected (E+), endophyte-free (E-), and novel-endophyte (NE) (MaxQ™) Jesup tall fescue (Festuca arundinacea Schreb.) hay on digestion and N retention in steers. Hay composition was as follows: E+ (10.8% CP, 59.9% NDF, 29.4% ADF), E- (11.8% CP, 58.5% NDF, 28.4% ADF), and NE (11.6% CP, 58.6% NDF, 28.3% ADF). Eight Polled Hereford steers (average initial BW ±SD 240 ±24 kg) were used in a replicated, 3 x 3 Latin square design, with an extra steer allotted to each square. Steers were fed ad libitum for 14 d followed by a 9 d adaptation to a restricted intake (based upon the animal with the lowest ad libitum intake for the square), and a 5 d fecal and urine collection. Endophyte-infected differed from E- and NE (P < 0.01) in ad libitum DMI (4.99 vs 5.64 and 5.67 ± 0.040 kg/d, respectively) and differed (P < 0.005) in ad libitum DMI as a percentage of BW (1.83 vs 2.07 and 2.09 ± 0.024%, respectively). There were no differences among diets during the digestion trial for restricted DMI (4.99 ± 0.055 kg/d), water intake (20.22 ± 1.131 L/d), and urine output (7.40 ± 0.650 L/d). Plasma prolactin concentrations were lower (P < 0.05) for steers on the E+ diet (7.76 ng/ml) versus those on the E- diet (18.57 ng/ml). The plasma prolactin concentrations for the steers on the NE diet (13.14 ng/ml) were not different from those on the E+ or the E- diets. Dry matter digestibility for E+ was lower (P < 0.05) than E- and NE (62.0 vs 67.4 and 66.6 ± 0.95%, respectively). Organic matter digestibility was also lower for endophyte-infected (P = 0.05) compared to E- and NE (64.9 vs 69.4 and 68.6 ± 0.89%, respectively). There were no differences for NDF, ADF, and cellulose digestibility among hay types. Crude protein digestibility was higher (P < 0.05) for E- and NE when compared to E+ (54.7 and 53.2 vs 47.4 ± 1.09%, respectively). Nitrogen retention was lower for E+ than E- (P < 0.06) or NE (P < 0.07) (14.4 vs 22.1 or 21.7 ± 1.90 g/d, respectively). Results from this study indicate that E+ tall fescue hay was lower in ad libitum DMI, DM digestibility, and N retention, than NE or E- and hay from NE and E- did not differ for any characteristic evaluation.