Forage Systems Redce Winter Feeding Period Develop a pastre system that best fits yor sitation. by Gerald Evers @ There are times dring the year when the prodcer mst emphasize the plant, and other times when he or she mst emphasize the animal. PHOTO BY SHAUNA ROSE HERMEL Livestock reqire some form of feed every day. Growing or stored forages (grasses, legmes, forbs and browse) are sed to spport livestock throghot the year. Rminants (for-stomached animals) sch as cattle, sheep and goats can tilize lowerqality or more fibros forages than monogastrics (single-stomached animals) sch as pigs. Forage systems are year-rond programs to provide sfficient ntrients to meet as mch of the animal s reqirements as possible to prodce meat, milk or fiber. Discssion of forage systems here, however, will be limited to beef cattle in the sotheastern United States, where Bermda grass and Bahia grass are the main smmer grasses. Managing a pastre for grazing livestock is more difficlt than growing a grain or fiber crop like corn or cotton. When growing a grain or fiber crop, the prodcer is concerned with the welfare of only one organism, the plant. In a grazing sitation, the prodcer is concerned with two organisms, the plant and the animal. Therefore, the prodcer mst nderstand the growth and development of both. Both mst be managed to provide efficient and economic animal performance. There are times dring the year when the prodcer mst emphasize the plant, and other times when he or she mst emphasize the animal. This plant-animal interface is a dynamic, always-changing system. The ntritive level in forage will vary with the class of forages, plant matrity and season. The amont of forage varies with management level, season and npredictable climatic conditions. To frther complicate matters, the ntritive reqirements of livestock vary with age and physiological stage (for example, yong growing animal, cow nrsing a calf or dry cow). Forage distribtion Unfortnately, prodction of warmseason and cool-season forages is not niform dring the growing season in a normal year, mch less in an abnormal year. Abot half of the annal yield of warmseason perennial grasses, sch as Bermda grass, normally occrs in a two-month period from early May throgh early Jly. Growth is poor from mid-jly throgh mid- September becase of high temperatres and sally lower rainfall. annal grasses sch as ryegrass, rye, wheat and oats prodce some forage in late fall, very little from late December throgh mid-febrary, and have 196 ANGUSJornal Agst 2008
a large prodction peak in spring. From 75% to 90% of annal clover prodction depending on species occrs in March, April and May. Part of the problem with grazing pastres is not total annal forage yield bt neven forage distribtion dring the year. Excess forage prodction from warm-season perennial grasses in May throgh early Jly can be harvested as hay. Becase of poor hay drying conditions in March and April, the peak forage prodction of cool-season annal pastres is best tilized by adding extra animals or harvesting part of the excess forage as silage or haylage. Althogh lower in ntritive vale than other forage classes (see Fig. 1), warm-season perennial grasses are the predominant forages grown in the sothern U.S. They are welladapted to the mild winter and hot smmer temperatres and will srvive smmer droghts. The grazing season is sally from sometime in April ntil the first frost. The challenge to the forage prodcer is to maintain the highest ntritive vale possible by keeping these grasses in a yong, growing stage with a high percentage of leaf. A fertilization program based on an annal soil test is the most efficient and economical way to maintain vigoros grass growth. forages are higher in qality than warm-season forages and can meet the ntritional reqirements of all classes of livestock (see Fig. 1). More than a million acres of annal ryegrass are grown in Texas each year becase it is easy to establish, tolerates close grazing and is adaptable to a wide range of soil types. However, it is less prodctive dring the fall and winter than rye, wheat, barley or oats. If grown in an area with annal rainfall of less than 30 inches (in.), irrigation will be necessary to obtain good annal ryegrass yields. The other cool-season annal grasses (rye, wheat, barley or oats) shold not be grazed shorter than 3 in. to maintain forage growth. winter pastres are best tilized for growing animals with high ntrient needs, sch as stocker calves and replacement heifers. Ntritive vale of plants The ntritive vale of forages is based on the level of energy, protein, etc., and its availability to the digestive system of the animal. Based on digestibility, forages can be divided into the following five categories: 1. warm-season perennial grasses; 2. warm-season annal grasses; 3. cool-season perennial grasses; 4. cool-season annal grasses; and 5. cool- and warm-season legmes. Fig. 1: Digestibility percent ranges for several forage classes Total digestible ntrients, % 80 75 70 65 60 55 50 45 40 annals Sdan grass, millets Bahia grass, Bermda grass, blestems Sorce: H. Lippke and M.E. Riewe, Angleton, Texas. As percent digestible dry matter (DDM) increases, animal performance in terms of weight gain, milk prodction, weaning weight and conception rate increases. In general, cool-season grasses are higher in Bromegrass, fesce, orchard grass, timothy annals Barley, oats, rye, ryegrass, wheat Legmes Alfalfa, clovers, cowpeas Fig. 2: Digestibility percent ranges for several forage grops and reqirements of different classes of livestock Digestible dry matter, % 80 75 70 65 60 55 50 45 40 annals annals Bahia grass, Bermda grass, blestems Bromegrass, fesce, orchard grass, Sdan grass, timothy millets Sorce: H. Lippke and M.E. Riewe, Angleton, Texas. Barley, oats, rye, ryegrass, wheat Legmes Alfalfa, clovers, cowpeas Steer, 350 Steer, 500 Cow-calf Dry cow DDM than warm-season grasses, annals are higher than, and legmes are higher than grasses (see Fig. 2). Within each forage class, plant matrity CONTINUED ON PAGE 198 Agst 2008 n AngsJornal n 197
Forage Systems Redce Winter Feed Period CONTINUED FROM PAGE 197 is the major inflence on ntritive vale. Ntritive vale is highest in new growth and decreases with plant age. One reason is that leaves are more digestible than stems and the percent leaves in the available forage decreases as plants matre and become stemmier. The second reason is that the digestibility of both leaves and stems decreases with matrity. Cell contents are 98% digestible and inclde carbohydrates, protein, triglycerides and glycolipids. Cell walls are mainly composed of celllose, hemicelllose and lignin bt are only 45%-75% digestible. Abot 70% of yong plant cells are highly digestible cell contents and 30% partially digestible cell wall. As the plant matres, the cell wall thickens with age by adding more fiber and lignin to where the cell wall acconts for 80% of the cell and, therefore, is less digestible. As forage plants matre, yield increases bt protein and digestibility (ntritive vale) decrease (see Figs. 3a, 3b). A compromise between yield and ntritive vale is to ct Bermda grass between three and for weeks for horses and dairy cattle and between five and six weeks for beef cattle. There is also a seasonal inflence on digestibility of warm-season perennial Fig. 3a: Effect of matrity on dry matter digestibility and yield of Bermda grass DDM, % 65 60 55 50 45 40 35 30 0 2 3 4 5 6 7 Week Sorce: W.G. Monson, Tifton, Ga. Fig. 3b: Effect of matrity on protein percentage and yield of Bermda grass Protein, % 15 13 11 9 7 DDM, % Yield Protein, % Yield 5 1 2 3 4 5 6 7 Week Sorce: W.G. Monson, Tifton, Ga. 6 5 4 3 2 1 6 5 4 3 2 Yield, lb./acre x 1,000 Yield, lb./acre x 1,000 The challenge to the livestock prodcer is to maintain the pastre sward in a yong growth stage that contains a high percentage of leaves, bt has sfficient leaf area to intercept a high percentage of snlight. grasses. Ntritive vale is the highest in the spring and then decreases as temperatre increases, reaching a low point in late Jly and Agst (see Fig. 4, page 199). Digestibility improves with cooler atmn temperatres. The challenge to the livestock prodcer is to maintain the pastre sward in a yong growth stage that contains a high percentage of leaves, bt has sfficient leaf area to intercept a high percentage of snlight. A sward height of 5-8 in. is appropriate for most sod-type grasses sch as Bermda grass, Bahia grass and Dallis grass. The prodcer mst have an nderstanding of the animal reqirements and ntritive vale of forages to manage pastres properly. Animal reqirements The general types of beef operations inclde cow-calf, raising replacement heifers and stocker/backgronding operations. One, two or all three of these operations may occr on pastre on the same farm or ranch. The segment of the beef cattle enterprise with the largest amont of variation in ntritional needs reqired dring the year is cow-calf prodction. Dring the 12-month cycle of prodction, a beef cow goes from low ntritional demands when not prodcing milk to high ntritional demands after calving and to several stages of moderate ntritional reqirements (see Fig. 5, page 199). Energy (TDN, total digestible ntrients) and protein priorities of a cow after calving are: cow srvival, maintenance and prodcing milk for the calf, and rebreeding. Knowing these priorities, or management shold be to make high-qality forages available to cows early in lactation if we are to maximize milk prodction and rebreeding. Approximately two months after calving, a cow will reach her peak lactation, or maximm level of milk prodction. 198 ANGUSJornal Agst 2008
Fig. 4: Inflence of season on digestibility of continosly grazed sod grass at Overton, Texas, sampled at two-week intervals Nonlactating, matre beef cows reqire low levels of ntrition to maintain body condition. Excess energy is converted to fat, which can be sed later when ntritive vale of the forage diet is less than the cow reqires. Fall-calving cows will have calves weaned in May-Jne, allowing the cows most of the smmer to regain the body condition lost dring lactation. Optimm weaning time for late winter- and spring-born calves is no later than September to allow the cows to regain some body weight before winter. Stocker programs place weaned calves on pastre to gain an additional 200 ponds (lb.)-300 lb. before going to the feedlot. The smaller the calf, the higher the ntrient vale of the diet mst be. Only cool-season pastres of smallgrains, ryegrass and clover have sfficient ntritive vale for 350- to 500-lb. calves to prodce average daily gains (ADGs) of p to 2-3 lb. per day for a five- to six-month grazing season. Tifton 85 Bermda grass can prodce average daily gains of abot 1.5 lb. on fall-born calves dring the smmer. More than 90% of the nitrogen (N), phosphors (P), potash and most other ntrients that are in the forage consmed by livestock passes throgh the animal and enters the soil in the rine and feces. This recycling of ntrients from the forage, throgh the animal and to the soil where they can be taken p by the plant roots to enhance forage growth mst be maximized to redce fertilizer needs. Livestock mst be grazing on pastre as mch of the year as possible. Legmes, like clovers, vetch and alfalfa, have the ability to se nitrogen from the air if the legme plant roots are infected by the appropriate Rhizobim bacteria. This free nitrogen comes at a cost of adding lime and other ntrients to grow the legme. However, if the legmes are only grazed so that the ntrients are recycled, maintenance fertilization after the establishment year shold be low. Matching animal reqirements to forage prodction and ntritive vale Fig. 2, page 197, shows the ntrient reqirements of several physiological stages of beef cattle across ranges of DM digestibility of forage classes. We will begin with a cow-calf operation sing only warmseason perennial grasses. It can be Bermda grass, Bahia grass, or some other warmseason perennial grass. Peak forage prodction normally occrs DDM, % 80 70 60 50 40 30 Coastal Bermda grass Common Bermda grass Pensacola Bahia grass 20 4-23 5-21 6-16 7-16 8-13 9-10 10-8 11-15 Date Sorce: Dble, 1970. Fig. 5: Total digestible ntrients (TDN) of three cow sizes for the year TDN, lb./day 20 18 16 14 12 Peak lactation 10 8 1 2 3 4 5 6 7 8 9 10 11 12 Months since calving 1,000-lb. cow 1,200-lb. cow 1,400-lb. cow Sorce: NRC, 1996; Appendix Tables 21-23. in May and Jne, with the best ntritive vale in spring (see Fig. 6, page 200). Becase the beef cow s highest ntrient needs occr after calving, when she is at maximm lactation and needing to rebreed, preferred calving time is Febrary-March (abot two months before peak ntritive vale). Weaning calves in early fall will allow the cow to gain some weight before first frost and match her period of low ntritional needs with the winter feeding period. A minimm of two pastres is reqired, with the designated hay pastre being from 25% to 50% of the total pastre acreage. In March-April, cows and their calves have access to both pastres. Abot May 1, the hay meadow shold be fertilized according to a Weaning soil test, and all the cows shold be placed on the other pastre. From late April to early Jly, one to two hay cttings are taken from the hay meadow with normal rainfall. It is important to harvest hay by early Jly when the ntritive vale of the grass is still high (see Fig. 4). Another advantage is that a pond of nitrogen applied in late April will prodce more ponds of forage than if applied dring the smmer when temperatres are higher and rainfall is lower. Cows and calves can graze both pastres after the last hay harvest ntil mid- September when forage growth rate is low. Abot mid-september the calves cold CONTINUED ON PAGE 200 Agst 2008 n AngsJornal n 199
Forage Systems Redce Winter Feed Period CONTINUED FROM PAGE 199 be weaned and the hay meadow fertilized with 60-70 lb. nitrogen per acre to prodce a fall hay ctting that is to be stockpiled and grazed in late fall when hay feeding is normally initiated. Sfficient hay shold have been made from the one to two hay cttings to carry the dry cows throgh the winter. A general gideline for northeast Texas is to have three large rond bales [5 6 foot (ft.)] per cow. The main disadvantage of this system is that calves are weaned and sold in early fall when calf prices are sally at their lowest. However, the cost per pond of calf gain shold be low becase cow wintering costs are low since she is not nrsing a calf dring most of the winter feeding period. A more advanced forage system is where part of the warm-season perennial grass acreage is overseeded with an annal ryegrass-clover mixtre (see Fig. 7, page 204). This system reqires a minimm of three pastres. A hay meadow (abot 40% of open pastre), a pastre to be overseeded with ryegrass-clover (abot 40% of open pastre), and a third pastre sed for feeding hay and calving (abot 20% of open pastre). The hay meadow shold never be overseeded with annal ryegrass since ryegrass grows throgh May and delays growth of the warm-season perennial grass. This reslts in the loss of the early hay ctting when warm-season grass growth and ntritive vale are the highest. With abot 40% of the pastreland sed as a hay meadow, one hay ctting abot Jne 1 with a yield of two and half large rond bales per acre shold be sfficient. If droght eliminates or redces the first hay ctting, a second hay ctting can be taken in early Jly. Ryegrass-clover grazing can sally begin sometime in Febrary in east Texas. forages have higher ntritive Fig. 6: Utilizing a warm-season perennial grass (Bermda grass, Bahia grass, etc.) with a two-pastre system Growth rate Mar Apr May Jn Jl Ag Sep Oct Nov Graze Graze April, Jly-Nov. A pond of nitrogen applied in late April will prodce more ponds of forage than if applied dring the smmer when temperatres are higher and rainfall is lower. Graze Hay May-Jne vale than warm-season forages, so the most digestible forage for the year in this system occrs from Febrary throgh April. Cows shold calve in December-Janary so their peak ntrient needs (after calving) match that of the ryegrass-clover growing period in March and April. These calves can be weaned in Jly or Agst before calf prices reach their normal low and allow the dry cow a longer grazing period before the first frost to gain weight and improve body condition score (BCS). An additional benefit of this system is a shorter winterfeeding period, which redces the amont of hay needed. Calving in winter dring harsh weather may increase calf death losses. Another disadvantage of this system is the dependence on fall rainfall to grow a standing hay crop and establish the ryegrassclover. Cows calve dring the winter on the calving pastre. When ryegrass-clover reaches a height of abot 6-8 in., cows with calves can be moved from the calving pastre to the ryegrass-clover pastre. If winter pastre is limited, cow-calf pairs can limitgraze the ryegrass and clover two hors per day or for hors every other day. Cows shold be able to graze the ryegrass-clover fll-time, beginning in mid-march dring the peak ryegrass-clover growing period. When the ryegrass-clover matres in May, it may take some time for the warm-season perennial grass to come back, especially if rainfall is limited in April and May and the stocking rate is redced for good seed prodction for volnteer reseeding of the ryegrass and clover. Cows can be moved back to the calving pastre, which accmlated grass while the cows were on ryegrass-clover pastre. Following the last hay harvest, cattle can also have access to the hay meadow. The sccess of this system is dependent on fall rainfall to grow a fall standing hay crop and establish ryegrass and clover. It is important to have a hay barn of some type to store excess hay in case of dry falls. If kept dry, hay will last for more than 8-10 years. Having hay stored nder a roof will redce the risk of a dry fall on this pastre system. Rotational grazing can still be practiced by sbdividing the hay meadow and ryegrassclover pastres. Smmary Two pastre systems have been presented as models for yor beef cattle operation. No two beef cattle operations are exactly alike. CONTINUED ON PAGE 204 200 ANGUSJornal Agst 2008
Forage Systems Redce Winter Feed Period CONTINUED FROM PAGE 200 They vary in soil, climate, size, prodcer goals and amont of time available to manage the operation. Each prodcer mst develop a pastre system that best fits his or her sitation. Important factors in developing a good forage system are desire, knowledge of livestock ntrient reqirements and forage management, and patience. Editor s Note: Gerald Evers is a Texas AgriLife Research forage management scientist based at the Texas AgriLife Research and Extension Center at Overton. Fig. 7: A three-pastre forage system consisting of a hay meadow, pastre for overseeding with ryegrass and clover, and a winter feeding/calving pastre (2-3 acres/cow) Pastre Jan Feb Mar Apr May Jne Jly Ag Sept Oct Nov Dec Hay meadow, 40% 2 hay cttings Hay if Standing hay crop needed Overseeded Graze Available grazing Seed ryegrass ryegrass-clover, 40% ryegrass-clover and clover Grazing pastre, 20% Feed hay Available for grazing 204 n AngsJornal n Agst 2008