The Corn Feed

Here are some of the latest research findings pertaining to silage and dairy production presented at the 2011 American Dairy Science Association/American Society of Animal Science Joint Annual Meeting in New Orleans, La.:

165 The Effects of Protease Enzymes and Storage on the Ensiling and Nutritive Value of Corn Silage

The objective of this study was to evaluate the effects of adding protease enzymes to chopped whole plant corn on silage fermentation and nutritive value after varying lengths of storage. Chopped and processed whole plant corn (Mycogen TMR2W726, Dow AgroScience, Indianapolis, Ind.) was harvested (36.3 percent dry matter) and ensiled without enzymes or treated with one of two different proteases (E85 or E86; AB Vista, Wiltshire, U.K.) at one times (1X) or one hundred times (100X) the manufacturer’s recommended dosage. The enzymes were mixed with a phosphate buffer and applied to chopped forage while mixing. Replicated-treated piles of forage were prepared for each enzyme treatment. Four bags of forage were vacuumed and heat-sealed for each enzyme treatment and storage time and allowed to ensile at 23 ± 2 degrees C for 45 and 150 days. The hypothesis was that in the silo, proteases would liberate starch and increase starch digestibility (Starch-D). The statistical analysis included the main effects of enzyme treatments, days of storage and their interactions. When compared with untreated silage, there was no effect of protease or length of storage (45 vs. 150 days) on pH, concentrations of crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF) or starch. At 45 and 150 days, treatment with proteases did not affect NDF-D or the concentrations of lactic acid, acetic acid or ethanol when compared with untreated silage. Ammonia-N and soluble-N (percent of CP) contents increased after ensiling compared with levels at harvest and were greater (P < 0.01) for the 100X enzyme doses when compared with untreated silage at both storage times (45 and 150 days). Starch-D (ruminal in vitro, seven hours) was 66.3 percent for freshly chopped corn plants. After 45 days of ensiling, treatment with E86 100X had greater (P < 0.01) starch-D (80.6 percent) than all other treatments except it was similar to E85 100X. After 150 days of ensiling, E85 1X (81.9 percent), E85 100X (82.9 percent) and E86 100X (88.6 percent) had greater (P < 0.01) starch-D than untreated silage (74.0 percent). Effects of the proteases on amino acid content and for longer periods of storage will be determined. The data obtained to date suggests that exogenous proteases could be used to improve in vitro ruminal starch-D in corn silages.

M352 On-Farm Dry Matter Testing to Improve Feed Delivery Precision on Dairy Farms

Silage comprises a major portion of total mixed rations (TMR) in most dairy operations. The content of the TMR that is offered to the animals differs from the intended ration. The uncertainty of rations may affect feed efficiency and consequently milk production, feed expenses and environmental losses. When silage is measured by weight, unaccounted for changes in silage dry matter (DM) content may substantially change a fed ration. The objective of this study was to measure variation in silage DM on selected dairy farms and determine the potential usefulness of an electronic method of on-farm DM analysis. A field survey of 31 Maryland dairy producers obtained data about on-farm DM analysis frequency, DM analysis methods, ration analysis frequency, feeding regimen, milk production and number of cows. Of those surveyed, 83 percent reported testing forage DM more than once per year by any method, and 63 percent reported testing DM by an on-farm method; mean number of cows was 103, and mean reported rolling herd average was 22,100 pounds. Eight surveyed producers volunteered to collect on-farm DM data for 21 days. Producers performed daily DM analysis using a Farmex 1210 electronic silage tester, recorded observations on rain events, and recorded ration changes related to the daily DM analysis. Silage samples corresponding to the on-farm DM analyses were retained, and were analyzed for DM after drying at 55 degree C followed by 100 degrees C (as standard method) and electronic tester (in-lab). There were large differences among farms in how well different methods of DM analysis compared. The difference between on-farm DM (electronic) and standard DM had a mean of 1.82 percent and SD of 4.99 percent. Ninety-five percent of observations fell within the limits of agreement (1.96 x SD ± mean) of −7.97 and 11.60 percent. The electronic method did not compare well to laboratory DM analysis for most farms.

T337 Effect of Replacement of Conventional Corn Silage With Brown Midrib Corn Silage on Behavior and Performance of Lactating Dairy Cows

Feeding forages with high neutral detergent fiber (NDF) digestibility to high-producing cows has the potential to increase feed intake and milk yield. However, highly digestible forage-based diets may negatively affect feeding behavior and ruminal fermentation. Fourteen multiparous Holstein cows (six ruminally fistulated) averaging 196 days in milk were used in a crossover design study with two-week periods (10-days adaptation, four-days collection) to determine the effect of NDF digestibility of corn silage on chewing behavior, ruminal fermentation, total tract digestibility and lactational performance. Dietary treatments consisted of 1:1 replacement (dry matter, or DM, basis) of conventional corn silage with brown midrib corn silage (BMR). The total mixed ration (TMR) contained 43 percent corn silage, 15 percent grass silage and 42 percent corn-soybean based grain mix (DM basis). The NDF content was 37.7 and 42.0 percent, the physically effective NDF (peNDF) was 35.8 and 39.6 percent, and 24-h NDF digestibility was 42.3 and 57.0 percent NDF for the conventional and BMR corn silages, respectively. Data were analyzed as a crossover design using the MIXED procedure of SAS. Cows had higher dry matter intake but lower feed efficiency when fed the BMR diet. Diet did not affect milk yield, milk composition, time spent eating or time spent ruminating. However, cows chewed less per unit of NDF and had a lower mean pH over a 24 hour period when fed the BMR diet. Highly digestible forage does not stimulate chewing to the extent that would be predicted based on standard laboratory methods, such as peNDF. Measurement of peNDF may need to be adjusted based on forage NDF digestibility since chewing response is a function of forage particle size and NDF digestibility.

222 Alternative Approaches of Replication for Estimating in Vitro Starch Disappearance

Measuring disappearance kinetics of starch and other substrates as they ferment is expensive and labor intensive because replicated serial measurements are needed. Assuming starch is 100 percent digested, rates of disappearance could be calculated theoretically from measurements at a single time by assuming that disappearance is zero at a fixed and assumed lag time. However this approach is dependent on removal of outliers and high precision in the measurement of in vitro starch digestion (IVSD). Our objective was to evaluate alternative strategies for minimizing the number of IVSD needed to measure starch disappearance rates. The IVSD of six samples of corn grain or silage (4-mm grind) were measured in quadruplicate on three consecutive days by Cumberland Valley Analytical Services, Inc. using a composite inoculum from three donors fed total mixed ration (TMR). Measurements were made at two, four, six, 12, 18 and 24 hours. Local regression (Proc LOESS in SAS) was used to detect outliers. LOESS has the advantage that not only the observations replicated within day, but also those from repeated days and serial times can be used to detect outliers. Proc NLIN of SAS was used to fit a model with a single exponential pool with discrete lag to the results. Rate and lag estimates were generated for each replicate within day. Proc MIXED of SAS was used to test day effects with random replicates. There was no difference among consecutive days for rates (P = 0.13) but a 1-hour difference in lags (P = 0.04). All 72 measurements for each feed were used to estimate the overall rate of starch disappearance, which varied from 0.114 to 0.168/h for the six corn sources. Deviations from the overall rate for each source were calculated by using four replicates within each day or two replicates from each of two days. There was no difference in deviations, absolute deviations or squared deviation for within-day or among-day rate estimates. When two replicates within day were compared with one replicate from two days there was no difference in replication approach. For consecutive-day in vitro, it appears that replications within day are as accurate as between day replicates for estimating rate.