Challenges in measuring moisture content of feeds

Abstract

Accurate determination of the moisture (water) content in individual feed ingredients and mixed feeds is critical throughout the feed industry. Most analytical methods used to determine apparent water content of feedstuffs are empirical, estimating water by evaporation and loss of weight on drying (oven drying methods). These methods differ greatly in effectiveness, resulting in bias. Bias associated with measuring the water content of feedstuffs is a concern not only because of the lack of confidence in the moisture value itself, but also because moisture determinations affect accurate quantification and expression of other nutrient values. Methods for determining moisture in feeds have frequently been borrowed from the cereal, forage, or other applications without validating the extension of the method. Methods such as Karl Fischer titration measure water by direct comparison to a calibration standard for water and can be used as reference methods for the evaluation of empirical methods. The objective of this paper is to review methods for determining moisture, review comparisons among moisture methods for various feedstuffs, make recommendations for a reference method, and make general recommendations toward improving the results of moisture testing. The need to evaluate and improve moisture methods and standardize practices in laboratories is evident from this study. It also is evident that the methods appropriate for a specific feed ingredient or feed should not be extended to all feeds without proper validation to the new matrices. Part of the validation for empirical methods should be comparison to Karl Fischer or other the direct methods. It also is recommended that the results obtained using oven methods not be termed "moisture;" rather, they should be termed "loss on drying," and the drying conditions should become part of the term.

Effects of drying methods on nitrogen and energy concentrations in pig feces and urine, and poultry excreta1

“…Determining the moisture content of feeds can be accomplished by multiple methods (Thiex and Richardson, 2003), and in swine experiments feeds have been dried at moderate (60°G, Stein et al, 2006) and high (95°G, Goebel and Stein, 2011) temperatures. Howev-er, obtaining a representative sample to adhere to the AOAG method 930.15 (AOAG, 2005) requiring only 2 g may be difficult.…”

Use of moisture meter on the post-harvest loss reduction of rice

“…Indeed, Thiex and Richardson (2003) proposed that the term "weight loss on drying" should be substituted for the term "moisture" when discussing feeds. Perkins (1943) noted that 4 to 7% more dry matter was lost from corn silage by 100° C drying than by toluene distillation.…”

“…Fox and Fenderson (1978) found that DM of corn silage was underestimated by 8% and 11% by oven drying at 60 and 100° C, respectively. As discussed by Thiex and Richardson (2003), chemical water content should be measured by the Karl Fischer titration method.…”

Determinação do teor de umidade em grãos empregando radiação micro-ondas

“…Além disso, o teor de água interfere diretamente no valor econômico dos produtos, pois os grãos são comercializados, normalmente, por peso (RAY et al, 1992). Os métodos para determinação da umidade em grãos consistem, normalmente, na retirada de água dos alimentos por aquecimento, em que o teor de umidade pode ser calculado através da diferença de peso inicial e fi nal das amostras (THIEX & RICHARDSON, 2003;MENDONÇA et al, 2007;VUATAZ et al, 2010). Segundo BRASIL (2009), o método ofi cial de determinação de umidade em grãos emprega a perda por dessecação em estufa (LOD, do inglês loss on drying), empregando 105±3°C durante 24h.…”