EVALUATION OF GRASS STRAW CORN JUICE SILAGE AS A RUMINANT FEEDSTUFF -DIGESTIBILITY, STRAW AMMONIATION AND SUPPLEMENTATION WITH BYPASS PROTEIN

Three experiments were undertaken to determine the feeding value of gr ass straw:corn juice silages compared to grass hay. In experiment 1 (7 0 d), the four basal diets were: 1) grass hay (GH) used as control tre atment; 2) tail fescue straw:corn juice silage (50:50 wt./wt.X(FCJ); 3 ) urea treated tall fescue straw:corn juice silage (50:50, wt./wt.(UFC J); and 4) annual ryegrass straw:corn juice silage (65:35, wt./wt.(RCJ ). Ammoniation was performed by spraying the straw with urea solution having 1% raw soybean extract (urease source) to provide 3% urea (dry matter basis). Thirty-six beef heifers (9 per treatment) were fed thes e roughages ad libitum with a concentrate supplement (1.36 kg d(-1)). Out of nine heifers allotted per treatment, four were fed individually while the remaining five were group-fed. Feed intake (FI) (kg), avera ge daily gain (ADG) (kg d(-1)) and feed efficiency (FE) (kg(-1) BWG) i n individually-fed heifers in experiment 1 were: 5.16, 0.671, 7.97; 5. 40, 0.557, 10.00; 4.84, 0.58, 8.41; and 4.54, 0.523, and 8.92 for GH, FCJ, UFCJ, and RCJ, respectively. In group-fed heifers, Fl and ADG wer e: 8.33, 0.71; 5.54, 0.564; 5.41, 0.568; and 5.92, and 0.38 for GH, FC J, UFCJ, and RCJ, respectively. No differences (P > 0.05) were observe d in any trait, except that ADG in group-fed animals on the GH treatme nt was significantly higher (P < 0.05) than in animals on the RCJ trea tment. In experiment 2 (57 d), the same animals and same roughages wer e used but supplementation was changed in the FCJ, UFCJ, and RCJ treat ments. In these three treatments, the concentrate was reduced to 682 g d(-1), and alfalfa hay was offered at 1.36 kg d(-1). The UFCJ group a lso received fishmeal at 125 g d(-1) as a source of by-pass protein. F I (kg), ADG (kg d(-1)) and FE in individually-fed heifers were: 7.99, 0.98, 8.80; 8.89, 0.81, 11.33; 7.60, 0.97, 7.87; and 7.83, 0.76 and 10 .37 for GH, FCJ, UFCJ, and RCJ, respectively, ADG was higher (P <.05) in UFCJ vs. RCJ and FE was higher (P < 0.05) in FCJ vs. UFCJ. In group -fed animals, FI and ADG (kg d(-1)) were: 8.43, 0.76; 7.19,0.67; 6.79, 0.70; and 7.14, and 0.55 for GH, FCJ, UFCJ, and RCT, respectively. AD G was higher (P < 0.05) in GH vs. RCJ. In experiment 3, 12 sheep were used to determine in vivo digestibility of the four basal feeds (witho ut supplementation) used in the first two experiments. Percent apparen t digestibility of dry matter (DM), gross energy (GE), crude protein ( CP), NDF, and ADF was: 60, 59, 45, 52, 56; 55, 56, 51, 46, 49; 59, 60, 74, 51, 57; and 55, 56, 30, 43, 50 for GH, FCI, UFCJ and RCJ, respect ively. Differences between GH and UFCJ were not significant (P > 0.05) for DM, GE, NDF, and ADF digestibilities; however, CP digestibility d iffered (P < 0.05). A similar pattern was noted between FCJ and RCJ. A ll digestibility parameters were higher (P < 0.05) in UFCJ vs. FCJ. Di gestible energy (MJ kg(-1)) was: 9.690, 9.569, 10.079 and 9.519 for GH , FCJ, UFCJ and RCJ, respectively. Feed intake was similar among the f our treatments. It is concluded that straw:com juice silages are about equal to medium quality grass hay in feeding value. Supplementation w ith alfalfa hay and fishmeal further improved performance.