Improvements of in situ degradability of grass hay, wet brewer’s grains, and soybean meal with addition of clay in the diet of Holstein cows

Abstract

Clay-based feed additives have been widely examined as tools for combating the negative impacts of both aflatoxin (AF) infected feedstuffs as well as subacute ruminal acidosis (SARA). The objective of this study was to determine the ruminal degradability of feedstuffs in response to 3 concentrations of dietary clay in lactating dairy cows. Treatments were: no clay (CON), 10, or 20 g/kg of dietary DM as clay (EcoMix®, UMG, Ukraine). Samples (8 g) of dried alfalfa hay (AH), grass hay (GH), wet brewer’s grains (WBG), ground corn (GC), corn silage (CS), or soybean meal (SBM) were placed into polyester bags (3 replicates per feed) and incubated for 0, 2, 4, 8, 12, 48, 72, or 96 h in 3 rumen-cannulated cows fed one of three treatments. Recovered bags were analyzed for DM, aNDF, ADF, starch, CP for all feedstuffs, and total fatty acids (TFA), saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) for GH, WBG, and CS. Soluble (S), digestible (D), and undigested (U) fractions; and fractional rate of digestion (Kd) and effective degradability (ED), were estimated for each feedstuff, treatment, and cow combination. Statistical analysis was preformed using the MIXED procedure of SAS. Grass hay S of DM exhibited a quadratic treatment effect (CON = 1.4, 10 g/kg = 1.7, and 20 g/kg = 1.2 g/kg). There was an increase in WBG D of DM as concentration of clay in the diet increased (CON = 5.9, 10 g/kg = 6.6, and 20 g/kg = 7.6 g/kg). There was a quadratic treatment effect for DM S (CON = 2.6, 10 g/kg = 3.4, and 20 g/kg = 1.5 g/kg) and ED (CON = 4.8, 10 g/kg = 5.7, and 20 g/kg = 3.9 g/kg) of SBM. There was a decrease in SBM S of starch (CON = 6.3, 10 g/kg = 4.7, and 20 g/kg = 3.3 g/kg) and an increase in SBM D of starch (CON = 7.7, 10 g/kg = 7.7, and 20 g/kg = 8.2 g/kg) as concentration of clay in the diet increased. There was an increase in GH D of SFA (CON = 3.4, 10 g/kg = 7.8, and 20 g/kg = 9.1 g/kg DM) and a decrease in both GH U (CON = 6.0, 10 g/kg = 1.9, and 20 g/kg = 0.0 g/kg DM) and Kd (CON = 0.07, 10 g/kg = 0.03, and 20 g/kg =0.01 h−1) of SFA as concentration of clay in the diet increased. There was a decrease in WBG S of SFA as concentration of clay in the diet increased (CON = 0.8, 10 g/kg = 0.4, and 20 g/kg = 0.3 g/kg). Corn silage D of TFA exhibited a quadratic treatment effect (CON = 7.3, 10 g/kg = 3.3, and 20 g/kg = 4.5 g/kg). In conclusion, the addition of clay at 10 g/kg of total dietary DMI maximized S for GH and SBM DM as well as ED for SBM. Also, the addition of clay at 20 g/kg of total dietary DMI maximized degradability of SFA for GH.