El 0-Foraging Around, Lancaster Farming, Saturday, February 22, 2003 GRAZING BEHAVIOR OF COWS ON PASTURE Warren J. Parker, Lawrence D. Muller, Steven L. Fales, and Marvin H. Hall Penn State Grazing studies at Penn State with high producing cows on pasture show that the inability of the cow to harvest enough forage during the time available for grazing is an im portant factor limiting milk production. This is especially true if the dry matter (DM) content of hergabe is low, such as for fresh wet spring growth which may contain only 12-16 percent DM. For example, a cow with a forage intake re quirement of 30 lbs. DM/day has to eat 200 lbs. of wet pas ture if the DM content is 15 percent! The demands that are placed on the dairy cow to eat this quantity of forage can be more fully appreciated if they are expressed in terms of grazing behavior. 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I ; ~ Canton, , * I ( ,1 j ‘ ' * * 11 1 Xa i\l\W by the amount of time spent grazing, the rate at which pas ture is taken into the mouth, and the amount of herbage taken with each bite. This can be written more simply as; Intake = grazing time x biting rate x bite size These variables, which have been quantified by grazing be havior studies (mainly in the British Isles and France), show that grazing time for dairy cows ranges from 420-700 minutes/day (7.0-11.6 hours) with a median of around 510 minutes/day (8.5 hours). The amount of time spent grazing increases as the amount of pas ture decreases, which is why high producing cows need to be provided with pastures at least five inches tall. Grazing time is also influenced by sward structure (e.g. how dense the pasture is), daylight hours, and the level of milk production. The rate of biting for dairy cows is in the range 55-54 bites/minute. 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Under pasture grazing only, dairy cows usually consume less than 3 percent of the bodyweight as DM, but in high producing cows this may be in creased to the equivale of 3.4 percent bodyweight. This sug gests that high producing Hol steins have a potential milk production of about 60 pounds per day if high quality pasture was the sole source of energy. This corresponds to the con sumption of 295 pounds/day of fresh herbage with a DM den sity of 15 percent, or an aver age bite size of 0.023 ounces DM. At a bitesize of 0.022 ounces/day, the cow would need to spend 584 minutes/day grazing to achieve a 44-pound DM intake. Grazing time will in crease in high producing cows. A French study, for example, found that cows rotationally grazed on i2Ni Sup#r-Ffo«t Suspension • Patented cutterbar flotation system with dual suspension the cutterbar reacts to obstacles independent of the rest of the machine • Lower ground pressure improves reliability and reduces crop stubble damage • Tool-free cutting height adjustment ryegrass and producing 45-77 pounds milk/day increased grazing time by 12 minutes for each 2.2 pound increase in milk production. The grazing behavior calcu lations have important practi cal applications. First, they broadly define the physical constraints in DM intake of pasture by dairy cows and clearly show that some supple mentation with high energy concentrates is required in high-producing herds on pas tures even if “ideal” herbage Project Grass Northeast Spring Meeting Set BLOOMSBURG (Columbia ter County. Tim will profile Co. Project Grass Northeast dairy grazing economic data will have its spring education- from Maryland. He will also al meeting on April 16. The update the group on new de meeting will begin at 10:30 velopments in the forage seed a.m. in the large meeting room industry, of Penn State Cooperative Ex- After lunch the group will tension in Columbia County, tour the beef farm owned and The office is located on Saw- operated by Greg and Deb mill Road near Lightstreet. Farr, Millville. The morning speaker will be For more information call Tim Fritz, agronomist for Dave Hartman at (570) King’s Agri-Seeds in Lancas 784-6660. to moot your every mood. Land Pride Rotary Cutters' offer fast, clean, dependable mowing and have been extensively tested to ensure operating safety. Our cutters are designed with safety in mind and have been tested using rugged industry standards. High blade tip speeds assure a clean cut in a variety of field conditions and standard stump jumpers and safety guards keep you up and running. With Land Pride, you’re assured a product that delivers top quality performance. Detlan Equipment, Inc. 141 East Main St. Silverdale, PA 18962 215-257-5177 Thomas L. Dunlap Rt. 220, Mam St. Exit Jersey Shore, PA 17740 570-398-1391 Eckroth Bros Farm Equip. Rd 2, Box 24A New Ringgold, PA 17960 570-943-2131 Eckroth Equipment Co. 4910 Kernsville Rd. Orefield, PA 18069 610-366-2095 C ; iW^aiMp^qm •V.V.V.'.ViV.V.V.V»V»V»V«'»V«V*%V.V* could be offered throughout the grazing season. Second, they emphasize the importance of grazing man agement in providing high quality pastures to the lactat ing dairy cow so that she is able to take large bites of her bage. The pasture research at Penn State is therefore taking cow behavior into account when ration programs and grazing management systems are being developed for high producing dairy cows. Pennsylvania Hines Equipment Stoltzfus Farm RT. 220, Belwood, PA Service 814-742-8171 Keller Brothers R 7 Box 405 Lebanon, PA 17042 717-949-6501 and 1950 Frultville Pike Lancaster, PA 17601 717-569-2500 Lehigh Ag Equipment, Inc. 6670 Ruppsville Rd., Allentown, PAIBIO6 610-398-2553 800-779-3616 M.S. Yearsley & Sons West Chester, PA 610-696-2990 Pikeville Warren County Equipment Inc. Service Center IRD 2, Oysterdale Road 228 Route 94, Oley, PA 19547 lair town, N J 610-927-6277 . . 908-362-6916 Cochranville, PA 610-593-2407 Stouffer Bros Inc. 1066 Lincoln Way West Chambersburg, PA 17201 717-263-8424 Valley Ag Turf 817 Tobias Road Halifax. PA 17032 717-362-3132 New Jersey Rodio Tractor Sales North White Horse Pike Hammonton, N.J. 08037 609-561-0141 *v*v*v VsVVVV
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