title: Intake, digestion, and N metabolism in steers fed endophyte-free, ergot alkaloid-producing endophyte-infected, or nonergot alkaloid-producing endophyte-infected fescue hay.
abstract: A digestion and N balance trial was conducted to compare effects of traditional endophyte-infected (E+), endophyte-free (E-), and nontoxic endophyte infected (NE; MaxQ; Pennington Seed, Inc., Madison, GA) Jesup tall fescue (Festuca arundinacea Schreb.) hay on digestion and N retention in steers. Hay composition (DM basis) was as follows: E+ (10.8% CP, 59.9% NDF, and 29.4% ADF), E- (11.8% CP, 58.5% NDF, and 28.4% ADF), and NE (11.6% CP, 58.6% NDF, and 28.3% ADF). Eight Polled Hereford steers (initial BW 240 +/- 9 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 restricted intake (based on the animal with the lowest ad libitum intake for the square) and a 5-d fecal and urine collection. Water intake (20.2 L/d) and urine output (7.40 L/d) did not differ (P > 0.10) during the collection period. Plasma prolactin concentration was less (P < 0.05) for steers on the E+ hay (8.83 ng/mL) than for those on the E- hay (18.03 ng/mL) and intermediate for steers on the NE hay (12.65 ng/mL). Endophyte-infected hay differed (P < 0.05) from E- and NE in ad libitum DMI (5.02 vs. 5.62 and 5.61 kg/d, respectively) and ad libitum DMI as a percentage of BW (1.86 vs. 2.06 and 2.06%, respectively). Restricted DMI during the fecal and urine collection was lower (P < 0.05) for E+ hay than for E- (5.04 vs. 5.24 kg/d), and NE was intermediate (5.19 kg/d). Dry matter digestibility was lower (P < 0.05) for E+ compared with E- and NE (62.3 vs. 67.0 and 65.9%, respectively). Digestibility of ADF was lower (P < 0.05) for E+ than for E-, and was intermediate for NE (61.5, 66.0, and 63.9%, respectively). There were no differences for NDF, cellulose, or hemicellulose digestibilities among hay types. Crude protein digestibility was higher (P < 0.05) for E- and NE than for E+ (54.3 and 52.5 vs. 48.1%, respectively). Nitrogen retention was lower (P < 0.01) for E+ than for E- or NE (15.6 vs. 22.7 or 23.0 g/d, respectively). Hay type did not influence plasma urea N, urine urea N output, or urine urea N as a percentage of urinary N. 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- hays with similar chemical composition. Hay from NE and E- fescue had nearly identical composition, and did not differ for any variable measured.
authors.affiliation: Department of Animal Science, North Carolina State University, Raleigh, 27695-7621, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Matthews
authors.forename: M H
authors.initials: MH
authors.lastname: Poore
authors.forename: G B
authors.initials: GB
authors.lastname: Huntington
authors.forename: J T
authors.initials: JT
authors.lastname: Green
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001806:Blood Urea Nitrogen; D001831:Body Temperature; D002417:Cattle / Q000502:physiology*; D004044:Dietary Proteins / Q000378:metabolism; D004063:Digestion / Q000502:physiology*; D004326:Drinking / Q000502:physiology; D004435:Eating / Q000502:physiology*; D004876:Ergot Alkaloids / Q000096:biosynthesis; D004879:Ergotamines / Q000032:analysis; D031751:Festuca / Q000737:chemistry / Q000145:classification / Q000382:microbiology*; D006999:Hypocreales / Q000378:metabolism; D008297:Male; D009584:Nitrogen / Q000378:metabolism*; D011388:Prolactin / Q000097:blood; D013696:Temperature; D014508:Urea / Q000652:urine; D014554:Urination
chemical_list: D004044:Dietary Proteins; D004876:Ergot Alkaloids; D004879:Ergotamines; C076760:ergovaline; D014508:Urea; D011388:Prolactin; D009584:Nitrogen