PSX-33 Effect of supplementing different proportions of sericea lespedeza with alfalfa silage on intake, digestibility, and nitrogen balance in sheep

Abstract

Abstract Dietary manipulations to include tannins can change the proportion and amounts of N excreted in the urine and feces as well as improve N-use efficiency in ruminants. This study was conducted to investigate effects on animal digestion parameters of adding different proportions of sericea lespedeza hay (SL) to alfalfa silage. Alfalfa was harvested in June 2018 at 75% bloom, chopped, and then packed at 55% moisture into plastic-lined bins and allowed to ensile for 3 months. Alfalfa silage was either offered alone or mixed with 9, 18, or 27% SL on a DM basis. These diets were offered randomly for ad libitum consumption to 16 ewes (41.8 ± 4.61 kg BW) in a randomized complete block design experiment with 2 periods to provide 4 observations per treatment per experimental period, each consisting of a 14-d dietary adaptation period followed by 5 d of total fecal and urine collection. Data were analyzed using PROC MIXED of SAS and orthogonal linear and quadratic trend analyses were tested. Digestibility (%) of DM and OM and digestible DM and OM intake (g/kg BW) decreased linearly (P < 0.05) with increasing SL addition to the diet. Digestibility of NDF and ADF decreased linearly (P < 0.01) with increasing SL, and apparent absorption (%) of N decreased linearly (P < 0.05) with increasing SL in the diet. Urinary N excretions (g/d) tended (P = 0.10) to decrease linearly while fecal N (g/day) tended to increase (P = 0.10) linearly with increasing SL proportion in the diet. In this study, supplementation with sericea lespedeza as a tannin source to alfalfa silage decreased forage digestibility and digestible organic matter intake and did not positively influence nitrogen use. The study was supported in part by USDA-ARS specific cooperative agreement 58-3655-4-052 and by USDA NIFA grant 2018-67019-27804.