Effects of crystalline amino acid supplementation to the diet on odor from pig manure

¹ Animal Sciences Group, Wageningen-UR, Bornsesteeg 59, 6708 PD Wageningen PO Box 17 The Netherlands; Department of Animal Sciences, Hue University of Agriculture and Forestry, Vietnam
² Animal Sciences Group, Wageningen-UR, Bornsesteeg 59, 6708 PD Wageningen PO Box 17 The Netherlands

^* To whom correspondence should be addressed. E-mail: andre.aarnink{at}wur.nl.

	Abstract

The objective of this study was to determine effects of specific crystalline AA supplementation to a diet on odor emission, odor intensity, odor hedonic tone, and ammonia emission from pig manure, and on manure characteristics (pH, ammonium-N, total nitrogen, sulfurous, indolic and phenolic compounds and VFA concentrations). An experiment was conducted with growing pigs (n = 18) in a randomized complete block design with 3 treatments in 6 blocks. Treatment groups were 1) 15% CP basal diet with 3 times the requirement of sulfur-containing AA (14.2 g/kg diet, as fed basis); 2) basal diet with 2 times the requirement of Trp, and Phe+Tyr (2.9 and 20.4 g/kg diet, as fed basis, respectively); and 3) basal diet with AA supplementation to levels sufficient for maximum protein gain. Pigs with an initial BW of 41.2 ± 0.8 kg were individually penned in partly slatted floor pens and offered a daily feed allowance of 2.8 x maintenance requirement for NE (293 kJ/BW^0.75). Feed was mixed with water, 1/2.5 (w/w). Feces and urine of each pig was allowed to accumulate in separate manure pits under the slatted floor. After an adaptation period of 2 wk, and after cleaning the manure pits, manure was subsequently collected. In the wk 5 of the collection period, separate samples were collected directly from each manure pit for odor, ammonia, and manure composition analysis. Air samples were analyzed for odor concentration, and for hedonic tone and odor intensity above odor detection threshold. Results showed that supplementing crystalline S-containing AA in surplus of the requirement increased odor emission (P < 0.001) and odor intensity (P < 0.05), and reduced odor hedonic tone (P < 0.05) from air above the manure pits. Supplementing crystalline Trp, Tyr, and Phe in surplus of recommended requirements did not affect odor emission, odor intensity, or odor hedonic tone. Regardless of dietary treatment, all pigs had similar performance levels. No differences were observed in ammonia emission from manure of pigs fed different levels of AA supplementation (P = 0.20). In order to reduce odor from pig manure, dietary S-containing AA should be minimized to just meet recommended requirements.

Key Words: crystalline amino acids, diet, growing pig, odor