EFFECT OF BACTERIAL INOCULANTS ON THE FERMENTATION AND PRESERVATION EFFICIENCIES AND NUTRITIVE VALUE OF ALFALFA SILAGE FOR GROWING STEERS

Two silage bacterial inoculants from Pioneer HiBred International, Inc. were evaluated using second-cutting a l falfa. The Pioneer brand 1174® inoculant and a Pioneer experimental inoculant each increased the rate and efficiency of the ensiling process in both farm-scale and laboratory-scal e silos. The two inoculants increased the DM recovery in the farm-scale silos compared to the untreated silage. Steers fed the experimental inoculant-treated silage gained faster (P<. 10) (2.56 vs. 2.37 lb per day), had a 4.0% higher DM intake, and were 4.3% more efficient than steers fed the untreated silage. The 1174-treated silage supported a numericall y but not statistically better steer performance than the control silage. When the DM recovery results were combined with the feed per gain results, the silages with 1174 and experimenta l inoculant produced 5.3 and 10.5 lb more steer gain per ton of crop ensiled, respectively, than the control silage.

Financial assistance, technical support, and bacterial inoculants were provided by Pioneer 1 Hi-Bred International, Inc., Johnston, IA.

Summary
Two silage bacterial inoculants from Pioneer Hi-Bred International, Inc. were evaluated using second-cutting a l falfa.The Pioneer brand 1174® inoculant and a Pioneer experimental inoculant each increased the rate and efficiency of the ensiling process in both farm-scale and laboratory-scal e silos.The two inoculants increase d the DM recovery in the farm-scale silos compared to the untreated silage.Steers fed the experimental inoculant-treated silage gained faster (P<.10) (2.56 vs. 2.37 lb per day), had a 4.0% higher DM intake, and were 4.3% more efficient than steers fed the untreated silage.The 1174-treated silage supported a numericall y but not statistically better steer performance than the control silage.When the DM recovery results were combined with the feed per gain results, the silages with 1174 and experimenta l inoculant produced 5.3 and 10.5 lb more steer gain per ton of crop ensiled, respectively, than the control silage.

Introduction
Adding select ed strains of lactic acid bacteria (LAB) has become common practice in silage-making .Bacterial inoculants have improved silage fermentatio n quality, reduced DM losses in the silo, and increased rate and efficiency of gain in over 30 growing/ backgroundin g trials with corn and sorghum silages at Kansas State University (KAES Re-port of Progress 651, page 101).The LAB are intended to dominate the fermentation phase of the ensilin g process.Alfalfa and other legumes can be difficult to ensile because of their low sugar content and high buffering capacity.However , we have shown in numerous trials over the past 15 years that inoculants help ensure that as much of the f ermentable carbohydrates as possible are converted to lactic acid, which removes some of the risk of having a poorly preserved, low-quality silage.
The objective of this stud y was to determine the effect of two LAB inocu l ants on the fermentation, preservation, and nutritive value of alfalfa silage.

Experimental Procedures
On June 22 and 28 of 1995, second-cutting alfalfa was swathed with a mower-conditioner; field-wilted for 24 hours; and ensiled in six, 10 × 50 ft, concrete stave silos by the alternate windro w and load method.The three treatments were: 1) no additive (control), 2) Pioneer brand 1174® inoculant, and 3) a Pioneer experimental ino culant.The inoculants were applied in water solutions at the silage blowers and supplied approximately 150,000 c o lony-forming units (cfu) of LAB per gram of ensiled alfalfa.The control received only water and the carrier ingredient s contained i n the inoculants without the LAB.Nine thermocouple wires were spaced ev enly in the forage mass in each silo to measure ensiling t emperatures during the first 8 weeks of storage.On each of the 2 silo-filling days, chopped alfalfa was removed from a randomly selected load, and control and inoculated forages were ensiled in 18 PVC laboratory-scal e silos per treatment.Triplicate PVC silos were opened at 1, 2, 4, 7, 21, and 90 days postfilling.
One farm-scale silo for each treatment was opene d on Septembe r 13 and December 3 and emptie d at uniform rates during a 12-to 16week period.Samples were taken twice weekly for DM recovery calculations and chemical analyses.Each sila ge was fed to 20 steer calves in a 75-day growi ng trial (November 8, 1995to Januar y 22, 1996).The calves were housed in individual pens, and ration DM intake was measure d daily.The complete mixed rations were fed to appetite and contained 76% silage and 24% concentrate (cracked corn-based) on a DM basis.The concentra t e was formulated to provide each steer with 200 mg of Rumensin; 50 mg of T ylan; 20,000 IU of vitamin A; 3,000 IU of vitamin D ; and 150 IU of vitamin E daily.
For 5 days before the start of the growing trial, all steers were limit-fed a forage sorghum silage-base d ration to provide a DM intake of 2.0% of body weight.Steers th e n were weighed individually on 2 consecutive days.For 2 days before the final weighing, the steers were fed their respective sil age rations at a restricted DM intake of 2.0% of bod y weight.Then individual weights were taken on 2 consecutive days.
The alfalfa silages i n the six farm-scale silos in this study also were fed to 60 early-lactation Holstein cows over a 7-month period (KAES Report of Progress 771, page 26).

Results and Discussion
A summary of the p reservation and composition results for the three alfalfa silages is shown in Ta ble 1.The average DM, CP, NDF, and ADF contents for the three silages were nearly identical, and these values reflect the uniformit y of the wilted, preensiled alfalfa during the two silo-filling days.Further evidence of the uniformity of the preensiled alfalfa were results for t he numbers of epiphytic (natural occurring) LAB pe r gram of forage --alfalfa ensiled on June 23 had 1.0 × 10 cfu per gram 5 and alfalfa ensi l ed on June 29 had 1.6 × 10 cfu 5 per gram.Yeast and mo l d counts for the alfalfa on the two fillin g days were approximately 1.0 × 10 cfu per gram of preensiled alfalfa.

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Ensiling temperature results showed that silages treated with both 1174 and experimental inoculant averaged 1 to 3EF cooler than the untreated silage throughout the first 8 weeks of storage (data not shown) .These cooler temperatures for the inoculated silages are consistent with several other inoculant studies using whole-plan t corn and sorghum silages in the KSU farm-scale silos.
The fermentation profiles showed that the inoculate d silages underwent a more efficient ensiling process in both the farm-and laboratory-scal e silos tha n the untreated silages.The silages treated with 1174 and experimental inoculant were characterized by having higher lactic acid contents and lactic to acetic acid ratios; lower pH values; and lower contents of acetic acid, ethanol, and a mmonia-nitrogen contents than the untreated silages.Both inoculants also increased the rate of th e ensiling process, as evidence d by lower pH values and higher lactic acid contents at days 2 , 4, 7, and 21 postfilling for inoculated silages com pared to the untreated silages (data not shown).Both inoculants increase d the DM recovery in the farm-scale silos compare d to the control silage --1174 by 1.95 percentage units and the experimental inoculant by 3.6 percentage units.
Performanc e by the steers fed the three alfalfa silage rations is presented in Table 2. Steers fed the experimental inoculant-treated silage gained significantly faster (2.56 vs. 2.37 lb per day) , had a 4.0% higher DM intake, and were 4.3% more efficient than steers fed the untreate d silage.The 1174-treated silage supported a numerically but not statistically better steer performance than the control silage.When the DM recovery results in Table 2 are combine d with the feed per gain results (Table 2), the 1174 and experimental inoculant silages produced 5.3 and 10.5 lb more steer gain per ton of crop ensiled, respectively, than the control silage.One steer was removed from each of the three treatments because of extremely low DM intake 1 during the first 28 days of the trial.100% DM basis.

Table 2 . Performance by Calves Fed the Three Alfalfa Silage Rations
Means on the same line with different superscripts differ (P<.10).
1Each value is the mean of 6 silos opened at 90 days postfilling.2 Expressed as a percen t of the crop DM ensiled.Data are only for the three silos filled on June 23, 4