Propionic acid-based additive with surfactant action on the feeding value of rehydrated corn grain silage for dairy cows performance

Eighteen Holstein cows with 218 & PLUSMN; 106 days in milk (mean & PLUSMN; SD) and average daily milk yield of 22 & PLUSMN; 7.6 kg (mean & PLUSMN; SD) were assigned to six 3 x 3 Latin squares to evaluate the effects of using a propionic acid-based additive with surfactant action (MycoflakeTM; Kemin South America, Indaiatuba, SP, Brazil) at the ensiling of rehydrated corn grain on its nutritional value and animal performance. Dry ground corn grain (998 & mu;m) was rehydrated to reach 400 g/kg fresh matter of moisture, with or without the additive, and ensiled in 200-L plastic drums. Treatments were prepared as follows: rehydrated corn grain silage (RCGS) stored for 30 d as a negative control (30CON), RCGS stored for 60 d as a positive control (60CON) and RCGS treated with MycoflakeTM at 2 L/t and stored for 30 d (30MYC). The animals were offered a total mixed ration containing 399 g/kg whole-plant corn silage, 98 g/kg Tifton haylage, 207 g/kg RCGS (according to treatment), 98 g/kg citrus pulp, 173 g/kg soybean meal and 25 g/kg mineral-vitamin mix in total diet dry matter (DM). Ruminal DM disappearance (DMD) of RCGS was evaluated in situ using two canulated Holstein cows after 12, 24 and 48 h of incubation. Total tract apparent digestibility (TTAD) of nutrients was determined using the indigestible neutral detergent fiber content as a marker measured after 288 h of incubation in a canulated Holstein cow. Although no change in soluble protein content was observed for the 30MYC silage, its NH3-N content was greater than 30CON in both DM (P = 0.01) and total N (P = 0.02) basis, and did not differ from 60CON. The proportion of NH3-N in soluble N of 30MYC was the highest compared to both 30CON (P = 0.02) and 60CON (P < 0.01). The 30MYC RCGS presented lower geometric mean particle size and greater surface area than both 30CON (P < 0.01) and 60CON (P < 0.01). Although the pH of 30MYC RCGS did not differ from 30CON and 60CON, its lactic acid content (11.9 g/kg DM) was greater than both 30CON (9.28 g/kg DM; P = 0.05) and 60CON (8.10 g/kg DM; P = 0.01). No changes in ruminal DMD were observed for 30MYC RCGS against 30CON. There were no changes on dairy cows performance fed the 30MYC RCGS against 30CON. Cows fed 30MYC RCGS presented a different pattern of sorting behavior against 30CON and 60CON, resulting in lower intake of physically effective fiber than both 30CON (P = 0.01) and 60CON (P = 0.02), although no effect on ruminating and chewing activities was observed. No effect on TTAD of nutrients was observed for cows fed 30MYC RCGS against 30CON. MycoflakeTM hampered the formation of aggregates in RCGS, and did not enhance proteolysis. Despite changes in sorting behavior, the additive did not affect performance of dairy cows.