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Description:
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The objectives of this study were : 1 ) compare botanical diet composition , diet quality , and forage intake of Angora and Spanish goats foraging sand shinnery oak (oak ) during the summer of 1986 in west Texas , 2 ) monitor blood levels of tannic acid equivalent (TAE ) and urea nitrogen (BUN ) in goats grazing oak range , 3 ) determine digestibility and nitrogen balance as a function of different levels of oak in the diet , and 4 ) determine the effect of oak resin and phenol fractions on deterring consumption . Esophageally -fistulated wether goats were used . Intake was estimated using the total fecal output : indigestibility ratio . Spanish goats selected (P >0 .05 ) more oak and forbs , and less grasses than Angora goats . Goats increased (P <0 .05 ) oak consumption from June (31 % ) to August (55 % ) , but decreased (P <0 .05 ) dietary forbs from 23 to 5 % . Condensed tannins in oak was 35 .9 mg /g throughout the study . TAE was higher (P >0 .05 ) in Spanish (1 .6 ug /mi ) than in Angora goats (0 .8 ug /ml ) , and declined (P >0 .05 ) as the summer progressed . TAE was not detected in blood serum of goats in the metabolism trials . Dietary digestibility was similar between breeds , and it declined (P <0 .05 ) as the season progressed . Dietary crude protein (CP ) , neutral detergent fiber (NDF ) , acid detergent fiber (ADF ) , and lignin levels were similar between breeds , and remained constant throughout the study . BUN was not different between breeds , increased (P >0 .05 ) as the summer advanced , but decreased (P <0 .05 ) with increased oak levels in the rations . Organic matter intake (OMI ) increased (P <0 .05 ) as the season progressed . OMI was 0 .9 , 1 .2 , and 1 .4 % of body weight for Angora , and 0 .9 , 1 .5 , and 1 .8 % for Spanish goats in June , July , and August , respectively . Apparent digestibility of organic matter , CP , NDF , and ADF decreased (P <0 .05 ) as oak levels increased in the rations . With increased dietary oak levels , fecal nitrogen increased (P <0 .05 ) and urinary nitrogen decreased (P <0 .05 ) . Also , digestible and retained nitrogen declined (P <0 .05 ) with increased levels of dietary oak . Relative consumption of alfalfa pellets was not affected when treated with ether extract compounds of oak . Goats ate less alfalfa pellets treated with methanol (P <0 .10 ) than untreated pellets . |