The Effects of Feeding Corn Silage that was Exposed to Air for Five Days With or Without Yeast Cell Walls on Production Parameters in Early Lactation Holstein Cows.

Abstract

Proper silage management is important in reducing excessive spoilage due to air exposure. The objective of this study was to compare the effects on production of feeding silage that was exposed to air for five days and Yeast Cell Walls (YCW) to Holstein cows. Forty-eight early lactation cows were randomly assigned at calving to one of four treatment diets within parity. Diets included: Diet 1 corn silage blended into a TMR (CON), 2) CON with added Yeast Cell Walls (CON+YCW), 3) silage that was exposed to air for five days blended into a TMR (EXP), 4) EXP with added Yeast Cell Walls (EXP +YCW). Cows were started on trial at 21 days in milk (DIM). Cows received the same silage type for the duration of the experiment, but switched YCW treatment at the experimental midpoint (45 d). CON corn silage was stored in a covered trench silo for the length of the study. EXP silage was taken from the same trench silo and piled under a covered shelter for 5 days before being blended into the TMR based on prior DM change. Blood and rumen fluid samples were collected on days 30, 44, 75, and 89 of the experiment and analyzed for parameters important for health and production. There were no significant differences in %CP, %ADF, and Mcal/kg NEL for treatment diets. Milk yield (35.87, 36.72, 36.58 and 37.07 kg/d), DMI (23.18, 22.09, 23.44, and 23.88 kg DM), % fat (3.23, 3.22, 3.22, and 3.18%), fat yield (1.16, 1.17, 1.16, 1.19 kg), %CP (2.86, 2.87, 2.80, and 2.79%), and protein yield (1.03, 1.05, 1.02, and 1.03 kg) were not significantly different among CON, CON+YCW, EXP, and EXP+YCW, respectively (P > 0.10). Acetate: propionate ratio was not significantly different among treatments CON, CON+YCW, EXP, EXP+YCW, respectively (2.4, 2.3, 2.4, and 2.3; P > 0.10). Concentrations of blood urea nitrogen (BUN) (19.8, 20.2, 21.0, and 22.8 mg/dl), rumen ammonia (10.7, 10.9, 9.9, and 9.8 mg/dl), as well as rumen pH (6.9, 6.8, 6.9, and 6.8) were not significantly different among treatments CON, CON+YCW, EXP, and EXP

+YCW, respectively (P > 0.10). DMI and dietary % CP was significantly lower in the EXP silage (P < 0.10). Concentrations of BUN (19.9 vs 21.5 mg/dl; P < 0.01) were significantly different for CON and EXP silage, respectively. The addition of YCW significantly lowered acetate concentration (59.03 vs 57.56 mol/100 mol; P < 0.10). Dual-Flow continuous culture fermentors were used to conduct an in vitro experiment. Ruminal fluid was obtained from a non-lactating Holstein cow and transferred into four fermentors which were fed the four treatment diets from the in vivo experiment. The in vitro experiment was repeated twice and lasted four five days. Control silage suppressed acetate production while increased the production of propionate and butyrate. Addition of YCW to the CON and EXP treatment diets suppressed methane, acetate, butyrate and total VFA production while increased the concentration of propionate.

(Key words: silage, mannanoligosaccharide, fermentors)