Dairy July 1999 HARVESTING CORN SILAGE FOR MAXIMUM NUTRIENT YIELD Dr. Jim Tomlinson Dairy Nutritionist, MSU Corn grown as a silage crop for lactating cow rations is a common practice on many Mississippi dairy farms. Corn grown for silage yields more energy per acre than any other forage. For many years, it was thought that the higher grain yield a corn variety produced, the nutritional value of that variety as silage was also higher. However, we have learned from research in recent years that this concept is not correct. The digestibility of the corn silage dry matter and fiber components is more directly related to quality than is grain yield. Most dairymen now select corn varieties to plant for silage production based on dry matter yield, fiber (ADF and NDF) levels and digestibility. The factors outlined below can have a direct effect on the quality and nutritional value of corn silage.   Stage of Maturity - At one time the recommended stage of maturity was called the hard dough or hard dent stage of maturity. We now refer to the optimal stage of maturity as between the one-half and three-fourths milk line in the corn kernel. These two recommendations are actually very similar, so the only difference is the terminology used. Dry matter yield, energy yield, and digestibility are maximized at this stage of maturity. Silage cut at this stage of maturity will also optimize anaerobic fermentation and minimize losses in the silo. Since it obviously takes time to harvest a silage crop, it is advantageous to plant varieties with varied days to maturity so the entire silage crop can be harvested at or near the optimal stage of maturity. Also, start harvest at the front end of maturity (one-third to one-half milk line so that most of the crop is harvested at the one-half to three-fourths milk line stage of maturity.   Moisture Level -The optimal level of moisture for corn silage is 65 to 70 percent. This moisture level coincides with the optimal stage of maturity (one-third to one-half milk line). Maximum dry matter intake by lactating dairy cows is also achieved at this moisture level. Obviously, if corn is harvested earlier than the one-third milk line, the moisture level will be above 70 percent and significant nutrient losses will occur in seepage. Conversely, if corn is harvested later than the three-fourths milk line, the moisture level will be less than 65 percent resulting in poorer packing, more heat production during fermentation (carmelization), and increased corn kernel passage in the manure. Wet corn silage tends to be higher in butyric acid (stinky smell), dry corn silage tends to be higher in acetic acid (vinegar smell) and "correct" moisture silage tends to be high in lactic acid (sweet smell) and low in both acetic and butyric acids. Based on the numerous corn silage sample analyses we have reviewed, most producers tend to harvest corn too early (above 70% moisture) than too late (below 65% moisture). Corn silage stored in a trench or bunker silo should be cut near 70% moisture for better packing and fermentation. Corn silage stored in an upright silo should be cut near 65% moisture because of the increased downward pressure due to the height of the silo.   Length of Cut - Many producers tend to cut corn silage too fine at or near 1/4 inch Theoretical Length of Cut (TLC). While this TLC results in more compaction in the silo, the fiber is not nearly as effective as it should be in the cow's rumen. The recommended TLC for harvesting corn as silage is ? - 1/2 inch. This TLC allows adequate effective fiber for normal rumen function and prevents higher incidence of disorders such as acidosis, displaced abomasum, and decreased dry matter intake. You can measure the TLC by measuring the cut width of the cob and/or stalk. A Penn State Particle Separator can be used if available. If newer equipment such as a processor (roller mill) is used when chopping corn silage, the TLC should be 3/4- 1 inch. The brand of equipment, number of knives, roller setting, etc. will dictate the TLC because all components of the corn plant are both cut and crushed (rolled). Note: It is important to keep the knives sharp on your forage harvester to achieve the correct TLC. As a rule of thumb, always remember that TLC also means Tender Love and Care, so treat your cows with TLC for their benefit which translates to increased benefit to you. In summary, forage is the basis of your feeding program. If corn silage is the primary forage, harvesting at the correct stage of maturity, moisture level and length of cut will result in higher nutritional quality. High quality corn silage requires less concentrate ingredient supplementation resulting in a lower feed cost per hundred pounds of milk. If those of us in MSU Dairy Extension can be of assistance to you, please contact us. SUMMER FLY CONTROL Dr. Fred Lehman, Leader Extension Veterinary Medicine Flies, lice and mange are irritating, external parasites of cattle. Fly infestations are significant because they can limit production by focusing the cattle's attention on swatting and scratching rather than on eating. Summer is the time when flies threaten cattle's performance. In heavy infestations, losses in the lactating herd can result in decreased milk production and increased mastitis. Flies can also transmit anaplasmosis. In heifers, fly infestations can result in less than expected weight gain as well as increased incidence of pink eye or conjunctivitis. Flies can also cause mastitis in heifers. There are two types of flies that create a nuisance for cattle. Flies such as face flies and horn flies, must consume the host's blood or body fluids (such as eye secretions) for nourishment. Heavy infestations can result in significant blood loss. Adults lay their eggs in fresh manure where the larvae can feed until they reach adulthood and subsequently parasitize the animal host. They cannot complete their life cycle without fresh, undisturbed manure. For this reason, face flies and horn flies are not found frequently on animals that are confined to free stalls or tie stalls because the fresh manure is constantly disturbed or removed. Rather, they are found on heifers, dry cows, or lactating cows in operations where pasture forage is utilized as a major portion of their nutrient intake and the manure patty remains intact. The second type and most obvious fly found around the dairy is the house fly. These are commonly called "filth flies" because they lay their eggs in decaying material such as grain, silage and old manure. Although houseflies do not consume blood or body fluid, they can transmit mastitis and threaten milking parlor sanitation. Control options for these two categories of pests vary slightly because of the location of egg deposition. The use of larval growth inhibitors such as VigilanteÆ and RabonÆ can be part of a control program for face flies and horn flies. Initiation of treatment early in the season may limit buildup. Horn flies can actively fly or be moved by the wind for neighbor's cattle to have maximum effect. Treatment for adult flies should begin when the fly count is greater than 200 per animal. Treatment prior to that time may not be cost effective and contribute to early insecticide resistance. Approved insecticides in the form of tags, sprays, or pour-ons can then be used to reduce the adult house fly or horn fly populations. Pour-on endectocides such as avermectins can be used to provide short-term adult fly control; however, only Eprinex(r) is approved for use in lactating cows. If possible, rotation of products with different classes of insecticide is thought to reduce the speed at which resistance is developed. Other tools for fly control include premise sprays and parasitic wasps. Removal of decaying material and prevention of spills is still a key factor in minimizing fly buildup. Fly control is important for the hygiene and health of the herd. An integrated pest control program that includes larval treatment, adulticides, premise control, waste management, and a bid dose of persistent management is most likely to result in satisfactory control. If you need more information on fly control please call the Animal & Dairy Sciences Dept. or the College of Veterinary Medicine at Mississippi State University. HONOR ROLL HERDS* Dairy County No. Cows Lbs ECM** 2X/3X RHA Milk RHA Fat RHA Prot DOT G&B DAIRY LINCOLN 38 83.5 2X 17044 677 620 05/04/99 MACTOC FARM OKTIBBEHA 206 83.1 2X 26211 984 830 05/20/99 STEWARD FARM INC TATE 373 70.9 2X 22771 824 727 05/17/99 DAVID ROBINSON & SONS RANKIN 134 69.8 2X 20634 721 634 05/21/99 COASTAL PLAIN EXP STA NEWTON 154 64.1 2X 20901 773 666 05/10/99 MELVIN NICHOLSON NEWTON 127 64.0 2X 23013 782 734 05/12/99 MILTON & TERRY JEFCOAT JONES 234 62.2 2X 20742 723 652 05/18/99 GURNEY'S DAIRY FARM AMITE 228 61.3 2X 18799 711 610 05/20/99 THOMPSON BROTHERS MARSHALL 132 60.1 2X 19577 699 625 05/06/99 BRAD BEAN AMITE 243 59.7 2X 20676 775 666 05/06/99 ROWZEE JERSEY FARM NEWTON 150 59.5 2X 16985 771 642 05/22/99 TURNIPSEED DAIRY MONROE 451 58.5 2X 19979 746 633 05/24/99 KNIGHTS DAIRY FARM JONES 142 58.3 2X 19956 698 653 05/17/99 LEON BARDWELL DAIRY LINCOLN 54 55.5 2X 17861 582 562 05/01/99 JAY PAUL HOOVER NOXUBEE 176 55.4 2X 17652 0 0 05/18/99 FREEMAN DAIRY PIKE 123 55.3 2X 19588 650 660 05/17/99 JIMMY TUCKER & SONS PIKE 203 55.2 2X 16055 611 513 05/04/99 ELWAYNE MAST NOXUBEE 172 55.1 2X 18156 677 576 05/20/99 A L BOYD JR WALTHALL 79 55.1 2X 19826 647 626 05/04/99 CLEMMER & HILL DAIRY TIPPAH 179 55.1 2X 19466 672 609 05/26/99 SUMMERS DAIRY MARION 54 53.9 2X 18455 660 574 05/10/99 CAL MAINE FOODS DAIRY HINDS 1587 53.6 3X 19876 720 638 05/22/99 DANNY WALTER SISCO LINCOLN 101 53.3 2X 17297 512 555 05/16/99 MAX & TAMMY STINSON WALTHALL 267 53.2 2X 15663 580 498 05/17/99 J & J JERSEY JONES 11 52.4 2X 16962 727 627 05/19/99 * Top 30 herds enrolled on supervised DHIA testing programs by test day energy corrected milk. ** ECM = (.3246 x test day milk) + (12.86 x test day lbs fat) + (7.04 x test day lbs protein) OPEN LETTER TO THE DAIRY INDUSTRY OF MISSISSIPPI Most of you have probably heard of my new position as Head of the North Mississippi Research and Extension Center. Even though I am really excited about this position and its many opportunities, I still have deep concern for the dairy industry of Mississippi. It has been a great privilege for me to work with the dedicated people involved in the Mississippi dairy industry. I was born on a dairy farm, owned a dairy farm for 10 years and have spent almost 18 years of my life working professionally with the industry. It has been my whole life and it will continue to be a major interest of mine in the future. There is one dairy at Holly Springs that is part of the North Mississippi Research and Extension Center. My efforts to support the dairy industry are not stopping now. I am just changing roles. I wish I could thank each of your personally for your support in the past. The success of any of our past educational programs has been because of you. I urge you to continue this support because these programs contribute to the viability of the Mississippi dairy industry. Even though the number of dairies is declining, the needs for educational support continues and sometimes even at a higher level due to larger dairies and more businesslike approaches to management. Please remember that I am still available to the dairy industry. I look forward to working with you in the future. Continue to use the support of the Mississippi State University Experiment Station, Extension Service and College of Veterinary Medicine for your needs. Reuben Moore Head, North Mississippi Research and Extension Center Continue to Page Two

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