MICROBIAL INOCULANT EFFECTS ON IN SITU RUMINAL DRY MATTER AND NEUTRAL DETERGENT FIBER DISAPPEARANCE OF CORN SILAGE

Transcription

1 MROBAL NOULANT EFFETS ON N STU RUMNAL DRY MATTER AND NEUTRAL DETERGENT FBER DSAPPEARANE OF ORN SLAGE Kathryn E. owles and Michael R. Murphy TAKE HOME MESSAGES Addition of an inoculant blend improved the conservation and feeding value of silage from a hybrid that contained 40% dry matter (60% moisture) at harvest, but not for a second hybrid that contained 34% dry matter (66% moisture) at harvest. Silage inoculants may be more effective for silages with high dry matter contents. NTRODUTON Microbial silage inoculants can improve conservation and digestibility of corn silage. This experiment was designed to evaluate the efficacy of a prototype microbial inoculant on composition and in situ ruminal dry matter () and neutral detergent fiber disappearance (NDF) of corn silage. MATERALS AND METHODS Two different corn hybrids ( and ) were harvested as whole plant corn forage at 1/8 to 1/3 milk line at a theoretical chop length of 0.95 to 1.25 cm using a forage harvester (model 1285; Gehl, West Bend, W). Two representative samples of chopped corn from each hybrid were retained for nutrient analysis (Table 1). One gram of each experimental inoculant was weighed into a clean container and mixed with one liter of clean water. For inoculation, forage was placed in a heavy plastic garbage bag. One of two treatments was applied: a control (no inoculant) or a blend of Lactobacillus buchneri and L. casei (Pioneer Hi-Bred, a DuPont Business, Johnston, A). noculant liquids were applied at a rate of 2 ml/kg of fresh forage using a syringe while hand-mixing the forage. Eight silos were prepared, in plastic food storage bags holding about 600 g of wet material, for each hybrid-inoculant combination. Air was evacuated, silos were heat sealed, and then stored at room temperature. At days 60 and 120 post ensiling, 16 silos chosen at random were opened (4 from each hybridinoculant combination). Samples from day 60 were analyzed for nutrients, ph and volatile fatty acid concentrations. Three lactating Holstein cows with ruminal cannulas were used to determine disappearance of and NDF from ensiled samples. The cows average weight was 1433 ± 176 lb. Milk production averaged 0 ± 19 lb. ows, housed in individual tie stalls, had free choice access to a totally mixed ration based on corn silage, alfalfa silage, ground corn, and soybean meal with fresh feed provided once daily at :00 AM. Nitrogen-free polyester bags containing 60 and 120-day samples also were placed in a mesh bag that was suspended within the rumen and incubated for 24 or 48 hours. When withdrawn from the rumen, bags were rinsed first with 8

2 cold water and then washed for 2 min in a washing machine on the rinse cycle. Bags containing residues from digestion were dried and analyzed for and NDF to calculate disappearance of and NDF during ruminal digestion. RESULTS AND DSUSSON Although was drier at harvest than (Table 1), crude protein, neutral detergent fiber, acid detergent fiber, nonfiber carbohydrate, ash, and ph of the two chopped forages were similar. Silages from the two hybrids differed in their response to the inoculant blend after 60 days of fermentation (Table 2). The percentages of, nonfiber carbohydrate, acetic acid, and propionate increased more when the blend of Lactobacillus buchneri and L. casei was applied to than when it was applied to. n contrast, the content of neutral detergent fiber, lactic acid, and lactic acid:acetic acid decreased more when the inoculant blend was applied to than when it was applied to. Ruminal degradation of the silages was influenced by hybrid, inoculant, ensilage time (either 60 or 120 days), and time in the rumen. The disappearance in the rumen of after 60 days of ensilage was 6% higher for the inoculant blend than for the control (Figure 1); whereas, it was 4% lower for. After 120 days of ensilage, disappearance of was 6% higher for the inoculant blend than for the control; whereas, it was unchanged for. The interaction of hybrid, inoculant, and time in the rumen also indicated that the inoculant blend enhanced disappearance in the rumen (Figure 2; and 7% at 24 and 48 hours, respectively) compared to the control for. Neutral detergent fiber disappearance in the rumen of after 60 days of ensilage was 1% higher for the inoculant blend than for the control (Figure 3); however, neither inoculant nor time of ensilage affected the NDF disappearance of. After 120 days of ensilage, NDF disappearance in the rumen of was still 14% higher for the inoculant blend than for the control. Differences in the composition and ruminal degradation of corn silages indicated that the inoculant blend improved the conservation and feeding values of the hybrid that was 40% (60% moisture) at harvest but not those of the hybrid that was 34% (66% moisture) at harvest. 9

3 Table 1. haracteristics of whole corn plant hybrids ( and ) at harvest. tem SEM 1 ontrast, % P, % of NDF, % of ADF, % of NF, % of Ash, % of ph Standard error of the mean. Table 2. omposition of silage from two corn hybrids ( and ) ensiled for 60 days after treatment with one of two inoculants (control or a blend of Lactobacillus buchneri and L. casei (Pioneer Hi-Bred, a DuPont Business, Johnston, A). ontrasts 1 tem ontrol Blend ontrol Blend SEM 2 H H x, % < P, % of < ADF, % of NDF, % of NF, % of Ash, % of ph Lactic acid, % of < Acetic acid, % of LA:AA Propionate, % of < < < Butyrate, % of Total acids, % of < H = hybrid, = inoculant. 2 Standard error of the mean. 3 Lactic acid:acetic acid.

4 % +6% +6% digested, % Hybrid (H) P < noculant () P < 0. Opening time P < HxxO P < Silage fermentation time, days Figure 1. n situ dry matter disappearance of silage from two corn hybrids ( or ) ensiled for either 60 or 120 days after treatment with one of two inoculants (control or a blend of Lactobacillus buchneri and L. casei (Pioneer Hi-Bred, a DuPont Business, Johnston, A). 11

5 % +14% NDF digested, % % +17% 5 0 Hybrid (H) P < 0.13 noculant () P < 0.02 Opening time P < 0.12 HxxO P < Silage fermentation time, days Figure 2. n situ neutral detergent fiber disappearance of silage from two corn hybrids ( or ) ensiled for either 60 or 120 days after treatment with one of two inoculants (control or a blend of Lactobacillus buchneri and L. casei (Pioneer Hi-Bred, a DuPont Business, Johnston, A). 12

6 Dry matter digested, % Hybrid by noculant by Time nteraction (P =.03) +% ontrol noc ontrol noc Rumen incubation time, hours +7% Figure 3. n situ dry matter disappearance at 0, 24, or 48 h in the rumen of silage from two corn hybrids ( or ) treated with one of two inoculants (control or a blend of Lactobacillus buchneri and L. casei (Pioneer Hi-Bred, a DuPont Business, Johnston, A). 13