Submitted to: Sheep and Goat Research Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2003
Publication Date: 12/31/2003
Citation: Turner, K.E., Neel, J.P. 2003. Quebracho tannin influence on nitrogen balance in small ruminants and in vitro parameters when utilizing alfalfa forage. Sheep and Goat Research Journal, 18:34-43. Interpretive Summary: Grazing livestock are not efficient utilizers of plant protein. Secondary compounds such as tannins found in specific plants can improve protein-use in livestock fed high forage diets. High protein alfalfa hay was supplemented with varying levels of a commercial source of plant tannin (i.e. quebracho) in feeding studies with sheep and goats and laboratory studies to evaluate nitrogen output and ammonia production. Including 1.5 to 3% quebracho tannin with alfalfa hay fed to small ruminants resulted in more fecal nitrogen being excreted by sheep and goats compared to no quebracho tannin supplementation. We also observed decreased ammonia concentrations when the higher concentrations of 1.5 and 3% quebracho tannin were added to alfalfa hay and incubated with rumen fluid in the laboratory compared to no quebracho tannin; this indicated less protein breakdown in the rumen of livestock. These results suggest that plant tannin addition to livestock diets have the potential to improve protein- use in sheep and goats. This work is useful to livestock nutritionist trying to develop supplements to protect protein from breakdown in the rumen to improve livestock performance. It will benefit farmers by helping to refine livestock feeding and grazing strategies that improve nitrogen- use in livestock and shift nitrogen excretion to a slower release fecal nitrogen form in order to reduce excessive nitrogen being returned to the environment.
Technical Abstract: Condensed tannins found in specific plants can improve N-use efficiency in ruminants. Feeding studies using small ruminants and laboratory experiments were conducted to evaluate the effect of quebracho tannin (QT) supplementation to alfalfa hay diets on nitrogen use, organic matter and fiber disappearance, and in vitro ammonia production. In two separate feeding trials, sheep [Exp. 1; 12 crossbred wether lambs (avg wt 47.7 kg)] or goats [Exp. 2; 12 crossbred Boer wether kids (avg wt 32.7 kg)] were randomly assigned to one of four dietary treatments replicated three times. Lambs or kids were offered chopped alfalfa (Medicago sativa L.) hay supplemented with QT at 0, 0.75, 1.5, or 3% of the total dry matter intake. Sheep and goats offered diets containing 1.5 and 3.0% QT had higher (P < 0.05) fecal N excretion (g/d) than animals offered the 0 and 0.75% QT. As a result of greater fecal nitrogen loss, overall nitrogen digestibility was slower in sheep (P < 0.07) and goats (P < 0.05) offered the higher QT compared to 0 and 0.75% QT supplemented animals. Serum urea nitrogen was 11% lower in QT supplemented goats compared to goats offered no QT. Calculated in vivo NDF digestibility was lower (P < 0.10) in lambs offered 1.5 and 3% QT diets when contrasted with lambs offered 0 and 0.75% QT. At 48 h, IVOMD decreased quadratically(P < 0.05) with QT addition. At 96 h, %NDF remaining decreased quadratically (P < 0.07) with QT additions. In vitro ammonia concentrations at 6 and 12 h were lower (P < 0.0 5) in tubes containing 1.5 and 3% QT when contrasted with tubes containing 0 and 0.75% QT. Further investigation is needed to define QT concentrations that allow optimal N and fiber utilization when ruminants are offered high protein, low energy diets or when grazing high quality pastures.