Effect of protein supplementation on low-quality forage utilization and nitrogen balance by lambs drinking saline water

J. I. ARROQUY,; LOPEZ, A.; A. JUAREZ SEQUEIRA

Congreso; Annual Meeting of ASAS ADSA; 2016

The aim of this study was to access the effect of protein supplementation on intake, digestion, and N utilization in lambs fed a low-quality hay (Panicum maximum; 6.4% CP, 79.5% NDF, 54.3% ADF) and drinking high-salt water. Twenty Hampshire lambs (n = 4; 31 ± 4 kg BW) allocated to in individual cages in a ten treatments by two period (10 × 2) trial. Treatments consisted (2 × 5 factorial) of two water qualities (WQ; low salt, LS; 442 mg/L of total dissolved solids (TDS) and 108 mg/L sulfate; and high salt, HS; 8358 mg/L TDS and 6363 mgL sulfate) and fve soybean meal levels (SBM , , 0.50, 0.75, and 1.00% BW/d). Supplemental SBM × WQ interactions were signifcant for forage OM intake (FOMI P= 0.04), total OM intake (TOMI; P = 0.04), whereas there was only a tendency for total tract digestibility OM intake (TTDOMI; P = 0.07). On average, HS had lower FOMI (P < 0.01; 33.0 vs. 26.1 g/kg BW0.75), TOMI (P < 0.01; 42.2 vs. 35.3 g/kg BW0.75), and TTDOMI (P = 0.01; 23.6 vs. 21.3 g/kg BW0.75) than LS, while SBM levels did not signifcantly affect FOMI (P = 0.86) and TOMI (P = 0.25). In contrast, TTDOMI linearly increased in response to SBM (P < 0.01). There wasno SBM × WQ interaction for water intake (P = 0.60), which tended to respond to SBM levels (P = 0.07) in linear fashion (P < 0.01), but was not affected by WQ (P = 0.39). There was no SBM × WQ interaction for total tract OM digestibility(TTOMD; P = 0.69). SBM linearly increased TTOMD (P < 0.01), and LS had lower TTOMD than HS (P < 0.01; 55.4 vs.59.3% for LS and HS, respectively). Nitrogen balance was not affected by SBM × WQ interaction (P > 0.12), but N utilization (N-retained/N-intake ratio; P < 0.01) was. Regardless of WQ, we observed that SBM exerted a quadratic and linear response for N utilization (P = 0.01) and balance (P < 0.01). In LS, N balance and N utilization became positive at 0.25%of SBM, but in HS were positive only at the two greatest level of SBM (0.75 and 1.00%). In conclusion, according to our results lambs fed low-quality forage require greater levels of protein supplementation to maximize total digestible OM intake, N balance, and N utilization when they drink high-salt water compared to those drinking low-salt water.