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ARS Home » Plains Area » Mandan, North Dakota » Northern Great Plains Research Laboratory » Research » Publications at this Location » Publication #195761
Title: EFFECT OF RESTRICTED FORAGE INTAKE ON RUMINAL DISAPPEARANCE OF BROMEGRASS HAY AND A BLOOD MEAL, FEATHER MEAL, AND FISH MEAL SUPPLEMENT

Author
item Scholljegerdes, Eric
item LUDDEN, P - UNIVERSITY OF WYOMING
item HESS, B - UNIVERSITY OF WYOMING

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2005
Publication Date: 9/1/2006
Citation: Scholljegerdes, E.J., Ludden, P.A., Hess, B.W. 2006. Effect of restricted forage intake on ruminal disappearance of bromegrass hay and a blood meal, feather meal, and fish meal supplement. Journal of Animal Science. Vol. 83-2146-2150.

Interpretive Summary: Tabular values used in balancing beef cattle diets for metabolizable protein often originate from cattle that are fed for ad libitum consumption. Using these values to balance metabolizable protein supply for cattle fed severely restricted (below maintenance requirements) quantities of forage may not be appropriate because intake restriction can alter the extent of ruminal protein digestion. Limited data are available on the evaluation of ruminally undegraded protein of dietary ingredients for cattle fed restricted amounts of forage and protein supplements. Therefore, we conducted two experiments to evaluate the ruminal disappearance of bromegrass hay and a supplement high in ruminally undegradable protein using in situ bag techniques. Protein degradation of the forage was not influenced by restricted dietary intake. However, effective ruminal degradation rate of hay protein decreased as level of forage intake increased and subsequently, the amount of supplemental protein escaping ruminal degradation also increased with increasing levels of forage intake. Therefore, caution must be exercised when using tabular values for ruminally undegradable protein when formulating diets for cattle consuming restricted levels of forage.

Technical Abstract: Two experiments were conducted to determine in situ disappearance of bromegrass hay and a ruminally undegraded protein (RUP) supplement in beef cattle fed restricted amounts of forage. Six Angus crossbred cattle (BW = 589 ± 44.4 kg; three steers and three heifers) fitted with ruminal cannulas were fed chopped (2.54 cm) bromegrass hay (8.9% CP) at one of three percentages of maintenance intake (30, 55, or 80%; one steer and one heifer per treatment). In both experiments, the cattle were allowed 7 d for diet adaptation followed by 3 d of sample collection. In Exp 1, in situ bags (50 _m pore size) containing 4.1 g of bromegrass hay (OM basis) were inserted into the rumen and subsequently removed at 3, 6, 9, 12, 15, 18, 24, 36, and 48 h after insertion. Nonlinear regression models were used to determine the rapidly solubilized protein Fraction A, the potentially ruminal degradable protein Fraction B, the ruminally undegraded protein Fraction C, and protein degradation rate. Intake level did not affect (P = 0.15 to 0.95) forage protein remaining after in situ incubation or Fractions A, B, and C; however, effective ruminal degradation of hay protein tended to increase quadratically (P = 0.12) as forage intake increased. In Exp 2, 4.2 g (OM basis) of an RUP supplement (6.8% porcine blood meal, 24.5% hydrolyzed feather meal, and 68.7% menhaden fish meal) formulated to provide equal amounts of metabolizable protein across all levels of hay consumption was evaluated in a similar manner as in Exp 1. The undegraded protein fraction of the supplement did not differ (P = 0.16 to 0.74) across treatments at 3, 6, 9, and 18 h; however, increasing forage intake resulted in a linear increase (P ' 0.06) in undegraded protein remaining at 12, 15, 24, 36, and 48 h. Dietary treatment had no affect (P = 0.30) on protein Fractions A, B, or C; however, protein degradation rate of the supplement decreased linearly (P = 0.03) as forage intake increased. Therefore, effective ruminal degradation of the supplement decreased linearly (P = 0.01) from 50.8 to 40.9% as forage intake increased from 30 to 80% of maintenance. Corresponding estimates of supplement RUP were 49.2, 56.5, and 59.1% for the 30, 55, and 80% of maintenance intake treatments, respectively. Restricting dietary intake can decrease the quantity of dietary protein that escapes ruminal degradation. Tabular estimates of RUP may not be appropriate for formulating diets to balance metabolizable protein in beef cattle consuming limited quantities of forage.