Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2017
Publication Date: 8/3/2017
Publication URL: http://handle.nal.usda.gov/10113/5863775
Citation: Halvorson, J.J., Kronberg, S.L., Hagerman, A.E. 2017. Effects of dietary tannins on total and extractable nutrients from manure. Journal of Animal Science. 95:3654-3665.
Interpretive Summary: Tannins are naturally occurring phenolic compounds, produced by plants, that are widely distributed in the plant kingdom including crops and forages. While plant tannins are known to influence ruminant nutrition less is known about their influence on manure quality. The objective of this research was to examine the effects of dietary tannins on the composition and the total outputs of nutrients in manure. We conducted a feeding trial with sheep to determine if intake of Sericea lespedeza (Lespedeza cuneate, a condensed tannin source), at 0, 10, 20, or 40% of the ration, would affect concentrations of total carbon, nitrogen, phosphorus, boron, and other nutrients in manure, and patterns of total excretion when fed with alfalfa. When sericea was added to the animal’s rations, average daily manure production increased from 40 to 50% of the ration dry weight. The concentrations of total carbon, nitrogen, and boron in manure, daily manure outputs, and manure/feed ratios for each element also increased. Concentrations of water-extractable nitrogen decreased with added sericea, and accounted for a smaller proportion of the total nitrogen in manure, but with greater manure outputs, no significant variations of daily outputs occurred. Variations in concentrations of extractable boron in manure were small, and daily outputs increased together with manure mass, but the proportion of soluble boron in manure decreased. Manure concentrations and daily outputs of phosphorus (P2O5) were not significantly affected by different rations. Conversely, concentrations, daily outputs, and proportions of water-extractable phosphorus were all significantly increased by sericea. This study provides useful baseline information about the nutrient content of sheep manure and indicates that dietary tannins can significantly alter manure quality and quantity that must be accounted for in integrated crop livestock systems.
Technical Abstract: The effects of condensed tannins on N dynamics in ruminants have been a topic of research for some time, but much less work has focused on their impacts on other nutrients in manure A 4 × 4 Latin square sheep trial was used to determine if intake of sericea lespedeza (Lespedeza cuneata; SL; a condensed tannin source), at 0, 10, 20, or 40% of the diet, would affect concentrations of nutrients in manure and patterns of total excretion when offered with alfalfa (Medicago sativa; ALF). With SL additions, average daily manure production increased linearly (P <= 0.01), from 40 to 50% of the diet mass, on a dry matter basis. The concentrations of total C, total N, soluble P, total and soluble Na, total and soluble S, total and soluble Mn, and total and soluble B in feces increased (P <= 0.05) while soluble N, total Ca, total and soluble Mg, soluble Zn, total and soluble Fe, total and soluble Cu decreased (P <= 0.02). Total P, total and soluble K, soluble Ca, and total Zn were unaffected. Comparing diets containing 0-40% SL, average daily outputs of total C, total N, soluble P, soluble K, total and soluble Na, and total Mn increased linearly (P <= 0.01) by 42.0, 71.2, 93.3, 45.2, 111, 148 and 52.4 percentage points, respectively. Total K, total and soluble S, soluble Mn, and total and soluble B increased quadratically (P <= 0.02) by 26.1, 52.3, 26.7, 147, 100 and 19.5 percentage points, respectively. Conversely, outputs of soluble Zn and total Fe decreased linearly (P <= 0.01), by -51.5 and -24.8 percentage points, while total Ca, total and soluble Mg, soluble Fe, and soluble Cu decreased quadratically (P <= 0.05) by -15.7, -12.3, -40.0, -89.9, and -60.3 percentage points, respectively. Outputs of soluble N, total P, soluble Ca, total Zn, and total Cu remained unchanged (P >= 0.14). Ratios of manure outputs to feed inputs for C, N, K, and B increased (P <= 0.02) but those for P and Mg were unchanged (P >= 0.10). Ratios of soluble to total manure outputs (S:O) increased (P <= 0.01) for P, Ca, Na, Mn; decreased (P <= 0.05) for N, S, Mg and Zn, Fe, Cu and B; and were unaffected by treatment (P >= 0.16) for K. Decreasing S:O ratios are consistent with the formation of complexes that adsorb these nutrients to insoluble fiber fractions of manure and could thus affect mineralization rates. This study suggests that dietary tannins, found in forages like SL, can significantly alter the concentrations, total excretion rates and throughput efficiency of nutrients in manure.