Optimizing Forage Quality in Corn Silage

Transcription

1 Optimizing Forage Quality in Corn Silage Dr. Kim Cassida

2 What is Forage Quality?

3 Quality Changes During Fermentation 1 day 7 days 42 days 360 days Short aerobic phase until O is used up Anaerobic bacteria ferment nonstructural carbohydrates in forage, so sugars and pectin, fermentation acids (primarily lactic) Low ph (target <4.0) ultimately kills most bacteria and prevents spoilage by other bacteria, fungi, and clostridia. L. buchneri survives low ph and converts lactic to acetic acid Proteolytic bacteria survive at low ph and continue to break down protein, SP Breakdown of proteins around starch granules leads to starch digestibility. The more mature the corn the greater this effect.

4 How ensiling time affects Starch Figure 5. Concentration and 7-hr in vitro digestibility of starch in 4 corn hybrids: 68% moisture normal (open square), 68% moisture BMR (open triangle), 59% moisture normal (closed square), and 59% moisture BMR (closed triangle). (Bedrosian et al., 2012)

5 MICHIGAN STATE UNIVERSITY Key Points Stover (55-60% of the crop DM) NDFD controls gut fill and thus drives DMI NDFD is driven by lignin content Lignin increases with corn maturity Grain (40-45% of the crop DM) Starch drives energy value of corn silage Starch content increases with corn maturity Mature corn starch is less digestible Starch digestibility can be increased by processing and fermentation time Cows that eat more usually milk more If DMI is limited, better digestibility increases milk

6 How much is improvement in forage quality worth? 1. Always compare how much it will cost to get the improvement to how much that extra milk is worth 2. Potential extra costs Land value/rental Seed cost Extra fertility or pesticides Processing costs (custom rates, new processor, part replacement, fuel) Storage costs for aging your silage inventory

7 Growing for Quality: BMR Genetics

8 What is BMR? Brown MidRib Genetics Naturally occurring mutation in corn, sorghum, and pearl millet Six different genes In corn, only BM1 and BM3 important Meta-analysis derived from 48 different studies (Ferraretto & Shaver, 2015) lignin by 0.9 points (45%) total tract NDF digestibility by 6% total tract starch digestibility by 1.5% DMI 2.0 lb/day milk 3.3 lb/day milk protein 0.11 lb/day No change for milk fat lb/day ( fat test) Photo: Wisconsin Corn Agronomy Save the BMR corn for the cows milking 60+ lb/day! Ensile separately.

9 What is Lignin? Lignin is a phenolic secondary compound found in plant cell walls Cell walls consist of a framework of cellulose and hemicellulose strands in a matrix of lignin Lignin is required for plant function & survival Gives rigidity and strength to cell wall Provides resistance to attack by pests & diseases Contributes to normal growth patterns Enhances water transport in plant by reinforcing xylem vessels May help reduce water content of cell walls NDF (Cell Wall) NDF Solubles Protein Sugar Starch Fat Pectin Organic acids Cellulose, LIGNIN, Hemicellulose

10 Common Criticisms of BMR corn #1. Yield drag BMR yields ~10% less on DM/acre basis Drag may be mostly due to poor drought tolerance Should you care about yield drag? Cow performance is a function of both intake and quality, therefore Minimize yield drag effect on milk check by selecting varieties with high Milk2000 value for Milk lb/acre You will still need to adjust acreage because cows will eat more of the better forage while they are making more milk

11 Common Criticisms of BMR corn #2. Lodging Weaker stalk and less root Use stacked varieties to prevent insect damage to stalk and root Maintain K fertility for stalk strength Reduce seeding density to encourage thicker stalks consult your seed supplier for optimum seeding density Lodging solely due to BMR trait is actually rather rare

12 Common Criticisms of BMR corn #3. Lack of pest & disease resistance Choose varieties with proven disease resistance Maintain good K fertility for pest resistance Plant BMR corn on the best ground to reduce stress Use stacked varieties for insect resistance Apply fungicides if needed

13 Common Criticisms of BMR corn #4. Less starch? NO. Amount of starch is not different (Ferarretto and Shaver, 2015) BMR corn starch is slightly less digestible (Ferraretto & Shaver, 2015). Reason unknown.

14 Chopping for Quality: Moisture, Chop Length, & Kernel Processing

15 How Moisture Affects Quality Too wet Clostridial (butyric acid) fermentation reduce DMI, sick cows Increased leachate discharge (shrink) lost nutrients Just right! Corn processes easily and packs densely Rapid lactic acid fermentation for excellent quality Minimum shrink ~10% Too dry Hard dry kernels are more difficult to process Hard to pack reduced density too much oxygen Poor fermentation (not enough acid) Heating (wrong bacteria & low thermal mass) reduced protein digestibility increase DM shrink

16 How Moisture Affects Quality 1. As corn matures Moisture, kernels harden Fiber digestibility of stover amount & digestibility of Starch Energy source for cow shifts from fiber/sugar to starch Nutritive value peaks at ½ milkline (Allen et al., 2003) 2. Ideal harvest moisture depends on type of silo Bunkers/piles 65-70% Bags 60-70% Upright 60-65% Upright oxygen-limiting 50-60%

17 Particle Size affects Forage Quality Small particles pack and ferment better save nutrients and reduce shrink Big particles provide physically effective fiber (pendf) increase rumination, Increase saliva production, Increase milkfat reduce SARA and displaced abomasums

18 Particle size is quantified two ways 1. Theoretical Length of Cut (TLOC): determined by knife spacing Typical TLOC recommendations: 3/8 for unprocessed corn 1/2 to 3/4 for processed corn 2. Corn Silage Processing Score (CSPS) i.e. kernel processing Determined by roll gap spacing % of starch passing through a 4.75-mm screen (0.19-in) >70% Optimal 50-70% Adequate or Normal <50% Inadequate

19 Kernel Processing Kernels should be broken into small pieces to increase surface area - nick, crack or split is not as good (Shinners & Holmes, 2013)

20 The Kernel Processing Trade-off As roll gap gets smaller Processor has to work harder Components wear out faster More fuel is used Harvest cost increases

21 Kernel Processing Kernel Damage >90% of kernels damaged Kernels Damaged, % Schuler, UWisc 50 3/8" TLC 3/4" TLC Unprocessed 0.04" 0.12" 0.20" Processed - Roll Spacing (3/4" TLC) Set TLOC at 3/4-inch and roll gap at 0.08 to 0.12 inches (2-3 mm)

22 Kernel Processing What About Shredlage? unique processor that allows greater TLOC while maintaining kernel processing 2 studies have been published Ferarretto and Shaver, 2012 Vanderwerff et al., 2015 Key Findings no effect on sorting, DMI, rumination, or milkfat, hence no net improvement for pendf rumen and total tract starch digestibility Inconsistent effect on milk and 3.5% FCM cost of silage production

23 Kim Cassida MSU Forage Connection, Questions? Kim Cassida

24 Packing for Quality

25 Silage Density Density is a function of packing Packing is a function of moisture, chop size, and tractor weight 1. Wetter corn is easier to pack 2. Smaller chop size is easier to pack 3. Need at least 800 lb packing wt per ton/hr delivered Well-packed silage 1. Reduces porosity & excludes air for better fermentation that reduces shrink 2. Fits more silage into your bunker, reducing storage costs At low densities, shrink may be 17-20% Target DM density lb DM/ft 3 = bulk density lb wet/ft 3 (at 65% moisture) Estimated bulk density as you fill = lb delivered/volume filled

26 Progressive Wedge Method Angle packing face at o or 1 ft rise per 3 ft run Spread layers no more than 6-12 deep before packing Apply extra packing to last layers Get sections filled, packed, and sealed within 3 days Seal as you go