Effect of Field Pea Level on Intake, Digestion, Microbial Protein Sythesis, Ruminal Fermintation, and Fill in Beef Cattle Fed Forage Based Diets
J.J. Reed, G.P. Lardy, M.L. Bauer, J.S. Caton, T.C. Gilbery
our ruminally and duodenally cannulated crossbred beef steers (397 ± 55 kg initial BW) were used in 4 x 4 Latin square to evaluate the effects of increasing level of field pea supplementation on intake, digestion, microbial protein synthesis, ruminal fermentation, and fill in steers fed moderate quality (8.0% CP; DM basis) grass hay. Diets, offered ad libitum twice daily, consisted of grass hay and four field pea supplements (23.4% CP; 0, 0.9, 1.8, and 2.7 kg daily; DM basis). Steers were allowed free access to water and trace mineralized salt blocks and were adapted to diets for 9 d. On d 10 to 14, intakes were measured. Field pea and grass hay were incubated in situ, beginning on d 10, for 0, 2, 4, 8, 12, 16, 24, 36, 48, 72, and 96 h. Ruminal fluid was collected and pH recorded at –2, 0, 2, 4, 6, 8, 10, and 12 h post-feeding on d 13. Duodenal samples were taken for three consecutive days beginning on d 10 in a manner that allowed for a collection to take place every other hour on a 24 h clock. Linear, quadratic, and cubic contrasts were used to compare increasing field pea level. Total DMI (kg/d and % BW; P = 0.03), OMI (g/d and % BW; P = 0.01), and N intake (P = 0.001) increased linearly while forage DMI decreased linearly (kg/d, P = 0.04; %BW, P = 0.06) with increasing level of supplementation. Ruminal pH (P < 0.001), stomach NDF disappearance (P = 0.02), and field pea in situ DM disappearance (P = 0.05) decreased linearly and apparent total tract NDF disappearance tended to decrease linearly (P = 0.09) with increasing field pea supplementation. Total ruminal VFA, apparent total tract OM digestion, bacterial N flow, true N disappearance in the stomach, and apparent total tract N disappearance increased linearly (P < 0.03) with increasing field pea supplementation. No significant treatment effects were observed for ruminal DM fill (P = 0.82), ADF intake (P = 0.16), true stomach OM disappearance (P = 0.39), apparent intestinal OM digestion (P = 0.36), stomach ADF disappearance (P = 0.17), apparent total tract ADF disappearance (P = 0.35), or in situ DM disappearance of forage (P = 0.46). Due to affects on forage intake and ruminal pH, field peas appear to act like cereal grain supplements in high forage diets.
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