Grass Straw in. Cattle and Sheep. Finishing Rations. Technical Bulletin 140. Oregon State University Corvallis, Oregon.

Transcription

1 Grass Straw in Finishing Rations Cattle and Sheep IF Technical Bulletin 140 V AGRICULTURAL EXPERIMENT STATION Oregon State University Corvallis, Oregon n November 1977

2 Grass Straw in Finishing Rations for Cattle and Sheep

3 Contents I. Feeding Trials with Steers _-. 4 Experiment 1. Straw meal and pellets, Experiment 2. Chemically treated straw, Experiment 3. Chemically treated straw varieties (Yearlings, 1975) Experiment 4. Treated and weathered cubes (Calves, ) Experiment 5. Fall calves and yearlings, II. Feeding Trials with Sheep Use of ryegrass straw in lamb finishing rations Experiment 1. Pelleted rations Experiment 2. Cubed rations _ Digestibility of Annual Ryegrass Straw Conclusions AUTHORS: D. C. Church, professor of ruminant nutrition, and W. H. Kennick, associate professor of meat science, Oregon State University, Corvallis. ACKNOWLEDGMENTS: The Field Burning Committee provided materials and funding to partially support the research. Personnel at the Straw Utilization Center provided expertise and made cubes and pellets. The authors thank them for their contributions. Mention of a trademark, code name, or proprietary product is for identification purposes only. This reference does not constitute a guarantee or warranty of the product nor imply its approval to the exclusion of other suitable products. 2

4 Grass Straw in Finishing Rations for Cattle and Sheep D. C. CHURCH and W. H. KENNICK ABSTRACT Weanling steer calves or yearling steers were fed growing and/or finishing rations containing varying amounts of grass straw in a series of experiments. The data demonstrate that rations with 30 to 35 percent annual rvegrass straw resulted in very satisfactory rates of gain. Finishing rations with 12 to 15 percent straw were equal to more typical rations with less roughage. Straw treated with 4 percent sodium hydroxide resulted in higher consumption and improved gain and feed efficiency without any problems in animal health. When fall calves or yearling steers were fed finishing rations with 40 percent grass straw, performance on the average was not at a satisfactory level. In studies with fattening lambs, pelleted rations with 60 percent annual, ryegrass straw produced satisfactory gains. Lambs were fed rations which had been cubed and then crumbled. They contained 50 percent plain or hydroxide-treated straw. Performance was not satisfactory, although it was considerably better on the hydroxide-treated straw. Digestibility studies with lambs indicated total digestible nutrients of about 41 percent (dry basis) for untreated annual ryegrass straw and about 46 percent for straw treated with hydroxide. The use of straw for cattle feed is hardly a new topic, but the use of relatively high levels of grass straws in growing and finishing rations has received much less publicity. However, the surplus of grass and cereal straws, coupled with higher costs of other common feed ingredients, has stimulated research on animal feeding studies. As feedstuffs, straws have several disadvantages. Most grass straws are low in protein, with average values ranging from about 3 to 8 percent (dry basis). There may be a much wider range in protein content (Youngherg and Vough, 1977, Oregon State Univ. Ext. Serv. Spec. Rept. 473), depending on the origin of the straw, fertilization and harvesting practices, and the amount of weathering before harvest. In addition to the low protein content, the limited amount of published evidence shows that digestibility of the energy in grass straw is low, 3

5 primarily because of the high content of fibrous carbohydrates (cellulose, hemicellulose) and relatively high levels of lignin. Furthermore, this type of material is digested slowly by ruminant animals. The combination of low digestibility and slow digestion greatly restricts the amount of feed animals can consume and the nutritional value they can obtain from it, As a result of their poor nutrient content, straws are normally used to it better advantage when fed to beef cows or other classes of animals that have low to moderate requirements for energy and protein. In the feedlot, adding some bulky material of this sort to high concentrate rations provides a more suitable physical texture without any appreciable effect on daily gain, although feed conversion normally will be reduced. When prices of concentrates are relatively high in relation to the price of beef, it is often desirable to increase the amount of roughage in the ration. Increased roughage feeding usually results in less trouble with cattle going off feed, but increasing amounts eventually will result in reduced rates of gain and a longer feeding period, so overall costs may or may not be reduced by using excessive amounts of straw or other low quality roughage. The surplus of grass straw in western Oregon and other localities and legal restrictions on burning have stimulated interest in utilizing more straw in animal feeds. Use of straw is now more feasible because of improved harvesting and processing technology. Consequently, a number of experiments have been carried out at Oregon State University to evaluate the use of grass straws in growing and finishing rations. These experiments are described in the remainder of this bulletin. 1. FEEDING TRIALS WITH STEERS Experiment 1. Straw meal and pellets, Weanling steer calves from the I7xperiment Station herd were used in these experiments. For comparative Ipurposes, two lots ( 10 head) were fed high concentrate growing rations an d conventional finishing rations that were 15 and 5 percent roughage, res pectively (Table 1). Calves received the growing ration from an initial average weight of 600 pounds to an average weight of about 840 pounds and tlien were switched to the finish- ing ration until the cattle were slaughtered at a final weight of about 1,050 pounds. The experimental rations were fed as shown: 4 Pen no. Rations 1,2 High concentrate growing ration (no. 1); conventional finishing ration (no. 2) 3,4 High straw pellet (no. 3), conventional finishing ration (no. 2) 5,6 High straw pellet (no. 3), straw finishing ration (no. 5) 7,8 High straw meal (no. 4), conventional finishing ration (no. 2) 9,10 High straw meal (no. 4), straw finishing ration (no. 5)

6 Table 1. Steer rations (Experiment 1, ) Ration number Ration ingredients 3* Alfalfa hay, ground..._ Alfalfa hay, coarse ground Crass hay, coarse ground Ryegrtss straw, ground Barley, steamrolled Corn, steamrolled Beet pulp, shredded Molasses Mustard seed, ground -.---_ Tallow Urea Wheat millrun Limestone Salt, trace minimal 4 5 Tricophos _ Antibiotic premix (TM-10) 1 1 Vitamin A premix (2 million IU/lb.) pounds per ton S , ,000 2,000 2,000 2,000 2,000 Ration nutrients Crude protein, percent Estimated TDN, percent 71.1 Calcium, percent.457 Phosphorus, percent * Ration no. 3 was pelleted. In each instance, the cattle were shifted from the growing ration to the finishing ration when the lots averaged about 840 pounds. The high straw pellet (50 percent straw) was included because adequate information shows that cattle and sheep can utilize more straw or other poor quality roughage in pelleted rations. These animals (pens 3-6) were then finished on a conventional ration (no. 2) or on a finishing ration (no. 5) that contained 12.5 percent straw. Animals in the other pens (7-10) were started on a high straw meal grower (no. 4, 25 percent straw) and were then shifted to the conventional ration or the straw finishing ration. Information on ration content of crude protein, estimated total digestible nutrients (TDN), and calcium (Ca) and phosphorous (P) content is given in Table 1. All steers were implanted with 36 mg of Ralgro at the beginning of the experiment and again when they weighed 820 to 840

7 pounds. When individual animals reached the weight of 1,050 pounds or the Choice grade, they were slaughtered at the OSU Meat Science Laboratory. In all instances, daily gain for the total period and feed conversion were calculated using a final weight obtained by dividing carcass weight by 0.6. This procedure is used because cattle on high roughage diets generally have a low dressing percentage and a large amount of fill (feed, water) in the stomach and gut. On a more typical finishing ration, cattle should dress at about 60 percent of their carcass weight. Data on cattle performance (Table 2) indicate that 50 percent straw in the pelleted ration (no. 3) was too much for maximal rate of gain. There was some problem in maintaining good quality pellets since straw does not pellet well. As a result, there was some problem with fines (small feed particles mixed with pelleted feed), and this nearly always reduces consumption. Calves fed the high straw meal ration (no. 4, 25 percent straw) gained more rapidly than steers on the pelleted ration and at the same rate as steers on the conventional ration, indicating that this amount of straw can be well utilized. Rations of this type are less apt to cause problems such as bloat or digestive disturbances than rations with more concentrate, particularly if the straw is chopped rather than ground in a hammermill. Nutrient dilution with straw may be expected to result in less efficient feed conversion, but the change in this case was of a minor nature. The cattle finished on the 12.5 percent straw ration (no. 5) also performed very well, as indicated by gains in the second half of the feeding period (Table 2)-3.15 pounds per day for the lot initially fed the high straw meal ration and 2.94 pounds per day for those initially fed the high straw pelleted ration. The overall performance was 3.04 pounds per day for all lots finished on the straw rations as compared to 3.12 pounds per day for those finished on the control. Based on our feed mill prices in January 1974, the cheapest gain was produced by cattle fed the high straw meal ration (no. 4) and finished on the conventional ration (no. 2). The straw finisher (no. 5) cost less initially, but a shift in grain prices resulted in it costing more per pound than any of the others. These feed costs might not be representative of costs in another year. Carcass data did not indicate any appreciable differences in these cattle, regardless of the ration combinations used. Cattle on the different straw rations consumed an average of 2.5 to 6.2 pounds of straw per day (about a 150-day feeding period). Of course, some were getting straw only during the first feeding period (those finished on the control ration). Although of a limited nature, this study gives some indication of the potential for using straw in beef finishing rations. 6

8 Table 2. Performance of steers fed rations containing ryegrass straw (Experiment 1, ) Rations Daily gain (lbs.) Feed per Avg Feed TDN fed* day straw con- con- Treatment (no.) 1st half 2nd half Total (lbs.) day (lbs.). version version Control 1-2 High straw pellet, control High straw pellet, straw finisher High straw Meal, control finisher High straw,meal, straw finisher 4-,5 Cost per lb.,(cents) Pellets initially Meal initially Finished on ration no Finished on ration no See Table 1 for rations. Rations no. 1 and no. 2 are more or less conventional starter-finishing, no. 3 contained 50 percent ryegrass straw and was pelleted, no. 4 contained 25 percent straw, and no. 5 contained 12.5 percent straw.

9 Experiment 2. Chemically Treated Straw, Weanling steer calves were used again in this study and were fed the following rations during the growing-finishing phases: Untreated straw 50 percent pelleted straw; 25 percent pelleted straw 35 percent straw meal growing ration; 15 percent straw finisher 25 percent straw meal growing ration; 15 percent straw finisher Hydroxide-treated straw 35 percent straw meal growing ration; 15 percent straw finisher 25 percent straw meal growing ration; 15 percent straw finisher The rations were similar to those used in the previous year. In addition to the straw, which was from annual ryegrass, the rations were made up of barley, corn, molasses, wheat millrun, alfalfa, cottonseed meal, and hydrolyzed feather meal; lesser amounts of tallow, urea, and salt along with mineral and vitamin A supplements; and an antibiotic premix. Management of the cattle was the same as in the previous year. The intent in this experiment was to feed a somewhat higher level of straw than was used in the previous year and to compare untreated straw to straw that had been treated with sodium hydroxide (lye). The straw used in the meal rations was provided by the Straw Utilization Center. The untreated straw was chopped, molasses was added, and the mixture was then cubed (1.5-in. cubes). With the hydroxide-treated straw, the straw was chopped, sprayed with a 30 percent solution of sodium hydroxide so that the final product contained 4 percent sodium hydroxide by weight, and the material was then cubed. This process results in some swelling of the straw fibers and some degree of increased solubility, which increases digestibility by ruminant animals. When the rations were mixed, the cubes were broken up by putting them through a hammermill with the screen removed. Results of this trial (Table 3) with the pelleted ration were similar to those of the previous year for daily gain, although feed conversion was somewhat lower. Cattle fed the untreated straw, particularly the rations with 35 percent straw meal initially, gained at a satisfactory rate (3.10 lbs./day). Treating the straw with hydroxide improved the gain by 0.4 pound per day during the growing period and by about 0.25 pound per day for the total feeding period. Feeding the sodium hydroxide-treated straw for the total feeding period resulted in an 8 percent improvement in rate of gain and a 6.1 percent improvement in feed conversion. Treated straw had no effect on ribeve marbling but resulted in slightly less back fat. Surprisingly, the higher level of straw (35 percent) in the growing rations resulted in greater daily gain with both the untreated and the 8

10 CD Table 3. Pe rformance data on steers (Experiment 2, ) 1st 2nd Rations period period Untreated straw Pelleted (50-25 percent) percent meal percent meal Hydrxide-treated straw percent meal percent meal 'Treatment means Daily gain (lb./day) Daily feed consumed Feed con- Carcass (lbs.) version (lb s. DM / lb. M ar bl ing Back fat Total* As fed basis Dry basis gain) scoref (inches) Untreated straw meal Treated straw _ percent straw percent straw * 2nd period and total gains calculated from carcass weight f 11 = small minus; 10 = slight plus..52..

11 hydroxide-treated straw, and feed conversion was 5.8 percent greater. The greater rate of gain and improved feed conversion by cattle on the 35 percent straw rations may have been because more corn was included in these rations. In the 25 percent straw rations, beet pulp and wheat millrun were substituted for the corn with the intent of providing a comparable energy level in both rations, and it may be that the 35 percent straw rations with corn were higher in available energy. Overall, this experiment demonstrated that hydroxide treatment resuits in a slight increase in feed consumption with some improvements in rate and efficiency of gain. Pelleting rations with 50 to 25 percent straw does not appear to be feasible because neither rate nor efficiency of gain was improved enough to warrant the added processing costs. Experiment 3. Chemically Treated Straw Varieties (Yearlings, 1975) In this experiment, yearling steers from the Eastern Oregon Experiment Station at Burns were divided into three groups and fed the following rations: Ration no. 1 Ration no. 2 Ration no percent sodium hydroxide-treated bentgrass straw 30 percent sodium hydroxide-treated annual ryegrass straw 30 percent sodium hydroxide-treated tetraploid ryegrass straw The growth response of these steers (Table 4) was quite variable as indicated by the range in daily gain. The higher values for steers on each treatment indicate that the rations were satisfactory for some steers to make a high rate of gain, but some steers did very poorly. In comparison with the ration that contained annual ryegrass straw, the bentgrass straw ration resulted in a very slight increase in daily gain 10 Table 4. Performance data on yearling steers (Experiment 3, 1975) Straw source,' 30 percent of rations Tetraploid Item Bentgrass Annual ryegrass ryegrass Number of steers _ Average daily gain (lbs.) Range in daily gain (lbs.) Daily feed consumption (lbs. DM/day) Feed conversion (lbs. DM/lb. gain) --- Carcass marbling scoref ---- Back fat (inches) _- _ -- * All straws were treated with sodium hydroxide. f 10 = slight plus

12 (+ 2.0 percent) but less efficient feed conversion (-7.4 percent). The less efficient gain may have been because the steers fed the bentgrass ration were slightly fatter, as indicated by the increased amount of backfat. The tetraploid ryegrass straw ration resulted in less gain (-6.8 percent) and also less efficient gain (-9.6 percent) than did annual ryegrass straw. These steers also had slightly more backfat than those consuming annual ryegrass straw. Overall, the performance. of these cattle was too variable to make any firm conclusions about the relative value of the different straws. Experiment 4. Treated and Weathered Cubes (Calves, ) In this experiment weanling calves were fed rations with approximately 40 percent annual ryegrass straw during the entire feeding period. The rations contained I percent urea during the first half of the period and no urea during the finishing period; otherwise, there was no change in ration composition. The remainder of the rations was made tip of wheat, barley, molasses, alfalfa, feather meal, tallow, and small amounts of antibiotic and vitamin A premixes. The only experimental treatment was that the straw was treated in three different ways: Ration no. 1. Ration no. 2. Ration no percent annual ryegrass straw 40 percent hydroxide-treated straw cubes (reground) 40 percent weathered and treated cubes (reground) In ration no. 2, the cubes were treated with the standard 4 percent of hydroxide before cubing. With the weathered straw, the cubes were treated with about 2 percent hydroxide. The weathered straw was ineluded because some feeders believe that cattle will consume larger amounts of weathered straw than of comparable unweathered straw. The straw cubes were reground by a hanunermill with the screen removed, and the straw was then mixed with other ration ingredients. The various straws were supplied by the Straw Utilization Center. Data on performance of the cattle (Table 5) show that feeding either the hydroxide-treated or the weathered and hydroxide-treated straw resulted in improved rate of gain (about 6 percent increase). Feed conversion improved slightly with the hydroxide-treated straw (2.7 percent) but not with the weathered and treated straw. The carcasses of cattle on the different treatments were similar with regard to marbling and amount of back fat or kidney fat (not shown). Although it is difficult to make comparisons from year to year, the rate of gain on these animals was considerably less than in the previous years when less straw was fed, particularly during the finishing period. We 11

13 Table 5. Performance data on steer calves (Experiment 4, ) tem hopped Rations, 40 percent straw Hydroxidetreated Weathered and hydroxidetreated Number of steers Average daily gain (lbs.) Daily feed (lbs. of DM) Feed conversion (lbs. DM/lb. gain) Marbling score* Back fat (inches) = small minus. would have to conclude that 40 percent grass straw is too much for finishing weanling steers if maximal rate of gain and feed conversion are desired. Experiment 5. Fall Calves and Yearlings, The experimental cattle for this study came from the Eastern Oregon Experiment Station at Burns. The yfdarling steers were put in the feedlot at Corvallis in mid-august. Cattle iin two pens (1,2) had been fed 2.5 pounds of barley per day while on ciested wheatgrass pasture. Animals in the other two pens (3,4) had been l )astured on irrigated alfalfa or clover pasture and fed about 6 pounds of barley per day. Two pens of fall calves (5,6) were placed in the feedlot in m id-august. These calves had been fed about 0.5 pound of barley per day while on crested wheatgrass pasture. Calves in the other two pens (7,8) went into the lot in early November after being on irrigated pasture at Burns. The cattle were divided into pens so one pen from each of the previous treatments was on ration no. 1 and one pen was on ration no. 2. The no. 1 ration (fed to cattle in pens 1, 3, 5, 7) contained 37.5 percent annual ryegrass straw supplemented with cottonseed meal. The remainder of the ration was made up of barley, molasses, tallow, and alfalfa hay plus mineral, vitamin A, and antibiotic supplements. The second ration (no. 2) was similar to the first except that dried poultry waste (185 lbs.) and feather meal (40 lbs.) were substituted for 225 pounds of cottonseed meal per ton of feed. Both rations were processed, mixed, and cubed by the Straw Utilization Center. The cubing machine was an experimental model based on a South African design. It produced 2-inch cubes. The tuber appears to have con- 12

14 siderable merit because it requires considerably less energy for the cubing process than more typical tubers now on the market. No unexpected problems were encountered with these rations. The cattle ate the cubes well with minimal waste. A few days of adaptation were required for the cattle to adjust to ration no. 2. This was readily accomplished by starting animals on ration no. 1 and gradually shifting them to ration no. 2. Some of the data from the trial are shown in Table 6. For the yearlings, gain tended to be greater on the no. 2 ration (dried poultry waste - feather meal, DPW-FM), but this was not the case for the fall calves. Feed conversion, when based on dry matter consumed, was less for the no. 2 ration for both yearlings and fall calves. When gains for all lots receiving rations no. 1 or no. 2 were averaged, there was no difference in daily gain but feed conversion was decreased by using DPW-FM in place of the cottonseed meal. The decrease in feed conversion amounted to a reduction of 9.33 percent. Table 6. Performance data on yearling and fall-bom steers (Experiment 5, ) Item Yearlings Ration no. Fall calves Ration no. Initial weight (lbs.) _ Daily dry matter consumption (lbs.) Daily gain (lbs.) Feed conversion (lbs. DM/lb. gain) _ Kidney fat (percent) Marbling score' Back fat (inches) Ration Means No. 1 No. 2 Daily gain (lbs.) Feed conversion (lbs. DM/lb. gain) * 4 = slight, 5 = small. Since the change in protein supplements was the only difference between rations no. 1 and no. 2, it is possible to calculate the value of the protein substitutes accurately. At the time the trial began, cottonseed meal cost about $180 per ton. If the mixture of DPW and FM is worth percent of cottonseed meal, then the mixture should be worth

15 Experiment 1. Pelleted Rations Data were not available on rations which included pelleted grass straw; consequently, an experiment was designed and carried out to evaluerties of the mixture since it is almost impossible to make good pellets ate high levels of straw with two protein supplements. The rations that were used in this experiment are shown in Table 7. The control ration (no. 1) contained 50 percent annual ryegrass straw. The other ingredients, such as barley and molasses, are more or less standard items. Some wheat millrun was added to enhance the binding prop- from $ per ton (90.67 percent x $180). Feather meal, which cost $220 per ton at that time, supplied 17.7 percent of the mixture and cost $ Thus, the DP«' would be valued at $ per ton ($ ). If the feather meal was priced at $300 per ton, a current price, then the dried poultry waste was worth $ per ton if the cottonseed meal price remained the same. In terms of rate of gain, the performance of the cattle in this experiment was not particularly good, although the feed conversion was reasonable for a ration with 40 percent roughage. Data for comparable cattle are not available, but younger cattle on a similar ration that was not cubed gained at a slightly lower rate and with slightly poorer feed conversion. Consequently, it is reasonable to conclude that cubing improved the performance of cattle in this experiment. II. FEEDING TRIALS WITH SHEEP Use o f Rye grass Straw in Lamb Finishing Rations Straw is not commonly fed to sheep in many areas and only very rarely has it been used in finishing rations for lambs. The reason, of course, is that straw is not especially palatable to sheep and is not highly digestible. As a result, the animal does not obtain much energy from the straw and performance is apt to he poor. Poor quality roughages such as straw can be used in larger amounts when rations are pelleted. The reason for this is that the roughage is more dense after pelleting, particle size is smaller, and animals like the physical texture of pellets. The material passes through the stomach more rapidly, thus allowing greater consumption. Experiments with pelleted rations made up of alfalfa, barley, and molasses or similar ingredients have shown that maximum gain can be achieved when pelleted rations contain about 25 to 30 percent concentrate. Feed conversion may be improved with more concentrate, but gain normally will not be any greater. 14

16 Table 7. Ration composition of high straw pelleted rations (Experiment 1, 1973) Ingredient Ration number :3 lbs. lbs. lbs. Ryegrass straw, ground ,200 1,200 1,200 Alfalfa hay, ground Barley, ground Wheat millrun Molasses, cane Soybean meal Urea Mineral supplement Antibiotic (TM-10) -. TOTAL Estimated composition Crude protein (percent) Calcium (percent) Phosphorus (percent) ,001 2,354-2,172 2,048-2, Rations with greater amounts of soybean meal or urea were fed for three weeks and the others for the remaining feeding period (maximum of 49 days). rations that contain high percentages of roughage such as straw. Ruminant animals normally will not eat much of the fines unless forced to do so, and this results in reduced food consumption. No supplemental protein was added to the control ration and the crude protein level (8.1 percent) is definitely too low for maximal lamb performance on rations containing much less roughage. This ration, as well as the others, was processed and pelleted into one-half-inch pellets at the OSU Experimental Feed Mill. Ration no. 2 contained the same ingredients as ration no. 1 except soybean meal was added to increase the protein level. Enough soybean meal was added initially to bring the protein level to 13.4 percent for the first three weeks. For the remainder of the feeding trial, the amount of soybean meal was reduced to give a ration with about 11 percent protein. Similarly, ration no. 3 contained added urea to give 13.4 and 10.9 percent rations. After addition of the soybean meal in ration no. 2, straw made up 51.0 to 55.2 percent of the ration; in ration no. 3, straw made up 58.6 to 59.2 percent of the ration. The lambs used in this experiment were typical of western Oregon feeder lambs. Most were Suffolk or Suffolk cross wether lambs. Some had lung worms. All lambs were drenched with Thibenzole before the experiment began and all lambs had been shorn recently. Lambs were al-

17 lotted to treatment on the basis of body weight. There were 20 or 21 lambs on each ration. Data on gain and feed conversion are shown in Table 8. In this table, gain and feed conversion are shown on the basis of live weight and as calculated when using a final weight obtained by dividing carcass weight by 0.5. The value of 0.5 was used because a rather typical carcass yield for a lamb when slaughtered is about 50 percent of live weight. Lambs consuming high roughage rations normally have a tremendous fill in the stomach and gut as compared to lambs fed rations with moderate amounts of roughage or good quality roughage. Thus, if actual final weight is used in calculations, it tends to exaggerate the gain and greatly improve feed conversion. Consequently, the data derived by using carcass weights are probably more realistic values. Lambs fed ration no. 1 gained less and had the poorest feed converwhen gain was calculated using carcass weights. Thus, even though sion of the three groups (Table 8). The differences in gain were not statistically different because of the variation within the different treatments. This poor response is a reflection of inadequate protein consumption. In addition, more lambs (four) did very poorly on this particular ration. When the basal ration (no. 1) was supplemented with soybean meal (ration no. 2), gain was improved appreciably and feed conversion was much better. Supplementing with urea improved gain and feed conversion, but less than with soybean meal. There were no appreciable differences in carcass quality, as most lambs graded USDA Choice. On the basis of the prevailing feed prices (1973), the costs of gain were: ration no. 1, $21.38; ration no. 2, $24.55; and ration no. 3, $16.90 the Table 8. Lamb performance Performance data of lambs fed pelleted high straw rations (Experiment 1, ) Daily gain (lb.! day ) Live basis _ Carcass basis* All lambs.258 Very poor doers out.304 (4) Average feed per day (lbs.) 4.21 Feed convention (lbs.) Live basis) 9.00 Carcass basis Ration number (0).334(l) Final live weight was calculated by dividing carcass weight by 0.5. Numbers in parentheses indicate number of very poor doers. 16 3

18 urea-fed lambs did not do as well as those supplemented with soybean meal, the cost was much less. Unfortunately, no comparative data are available on similar lambs fed more typical finishing rations. However, these costs would have been very competitive at that particular time and the results suggest that moderate to medium levels of straw could well be used in pelleted rations for finishing lambs. Experiment 2. Cubed Rations An experiment was initiated in the summer of 1976 to evaluate high straw rations for finishing western Oregon lambs. The composition the rations is shown in Table 9. A ration containing 30 percent ground barley of and 70 percent chopped alfalfa hay was used for comparative purposes. The other rations contained 50 percent straw or processed straw. Dried whey was added as a binder, cottonseed meal as a source of supplemental protein and phosphorus, and barley was added for additional energy. Table 9. Rations fed to experimental lambs (Experiment 2, 1976) Ingredient Ration number (percent composition) Alfalfa hay Barley, ground _ _ Dried whey Cottonseed meal Limestone Untreated perennial ryegrass straw Defiberized ryegrass straw 8.0 Hydroxide-treated ryegrass straw 50.0 Sodium hydroxide (lye) was added as a 30 percent solution, equivalent to 4 percent hydroxide of the weight of straw. A simplified cubing machine (an experimental model produced by the California Pellet Mill Co. based on a South African design) was available for making 2-inch cubes, and all rations were mixed and cubed with this machine by Straw Utilization Center personnel. The cubes, although of a satisfactory size for cattle, were too large for the lambs or, if some of the concentrate was inadequately mixed, they were too hard. Consequently, the cubes were put through a forage harvester to break them up without further reducing particle size of the processed feed. It was necessary to hammermill part of the rations during the latter part of the feeding trial. When this was done, consumption was reduced. In ration no. 2, untreated perennial rvegrass straw was added at a level of 50 percent of the total ingredients. In ration no. 3, part of the

19 straw (8 percent of total ration) was replaced by defiberized straw. This material was produced by moistening and heating the straw and then grinding it in a machine that contained a rotating disk. After passing between the disks, the straw is then dried or mixed wet with the remainder of the straw before grinding and mixing. This process breaks up the cells of the straw and should result in increased digestibility by the lambs. It also increased the bulk density of the cubed feed by 15 to 20 percent. In ration no. 4, the straw was treated with a 30 percent solution of sodium hydroxide (lye). The amount was equivalent to adding 4 percent of the dry weight of the straw. A number of different reports have shown that this process increases digestibility by a substantial amount, sometimes as much as 50 percent. The lambs used in this experiment were fairly typical of western Oregon feeder lambs. A mixture of wethers and ewe lambs, most of them Romney or Romney x Suffolk crosses, was used. They ranged in weight from 47 to 90 pounds, with an average of about 71 pounds. Some of the lambs had lung worms. Before the experiment started, all lambs were drenched with Thibenzole for stomach worms and shorn. Lambs were randomly allotted to pens and pens to rations. There were two pens of 12 or 13 lambs on each ration. Lambs were weighed at weekly or biweekly intervals, and they were topped out when judged to be fat enough to grade Choice. The lambs were slaughtered and processed at the OSU Meat Sciences Laboratory, where data were collected on carcass weights, fat cover over the loin, and percent kidney fat. Some of the data collected on the lambs are shown in Table 10. The performance of the lambs on the alfirlfa-barley mixture was rather disap- gain more than 0.4 pound per day pointing. It was anticipated they woiild on this ration, but consumption wa., low and performance suffered as a result. Moisture damage to the hay from a damp summer harvest is a likely cause of the low consumption, although precautions were taken to dry the ration after cubing. Differences in gains between the three straw rations (nos. 2, 3, 4) were not statistically different because of the great variability within the different treatments. Lambs on the untreated straw (no. 2) gained less and had the poorest feed conversion. This type of performance was anticipated because the digestibility of straw is low and the lambs simply could not eat enough to gain at a high rate. A few lambs did very well, as indicated by the upper level on range in liveweight gain (0.463 lb./day). The addition of 8 percent defiberized straw resulted in a slight improvement in gain and an improvement in feed conversion, but the improvement would not be nearly enough to pay for this type of processing. Treating the straw with lye resulted in the best gains (avg lb./day), 18

20 Table 10. Performance data on lambs finished on high straw rations (Experiment 2, 1976) Live weight (lbs.) Cold carcass Daily gain* Avg. feed Feed conver- consump- S1o11 Back Roughage source No. of weight Days on tion lbs. DM/ fat fat in rations lambs Initial Final* (lbs.) feed Avg. Range (lbs.) 11). gain) (in.) (percent) Kidney Alfalfa Untreated ryegrass straw Straw and defiberized straw Hydroxide -treated straw Final weight was calculated from carcass weight by dividing by 0.5; daily gain was calculated using data obtained in this manner. This procedure eliminates wide differences in stomach and gut fill that are common on rations of this type.

21 the highest gain of any individual lamb (0.617 lb./day), and a considerable improvement in feed conversion. There was not much difference in thickness of back fat. The straw-fed lambs had less back fat than the controls (alfalfa-barley), but their carcass weights were lower also. Kidney fat was less in lambs on ration no. 2 (untreated straw). No unusual problems were encountered with this ration or any of the others, although water consumption was much higher by lambs receiving the lye-treated straw. Several lambs had rectal prolapses, but there was no indication they were caused by any particular ration. Ingredient Table 11. Costs of rations fed to lambs (Experiment 2, 1976) * Prices as of July Unit cost' $/cwt Alfalfa Barley, ground :20 Cottonseed met! Dried whey Limestone Unrteated perennial ryegrass straw Defiberized ryegrass straw Hydroxide-treated ryegrass straw ,6 Cubed bulk density - lb./cf Total ingredient cost $/cwt $/tor Estimated production cost $/ton Total cost at plant $/ton Feed conversion (lbs. feed/lb. gain) ---- Ingredient cost of gain ($/lb. ) Ration number ($/cwt) Feed costs and cost per pound of gain (Table 11) were rather high. With a more normal feed conversion for the alfalfa-barley mixture, feed costs per pound of gain would have been 45 to 50 cents. The poor feed conversion plus the rather poor gains resulted in very high costs for all of the rations containing straw, particularly the two not containing hydroxide-treated straw. There was a fair amount of waste, so the feed conversion values are exaggerated. In the previous experiment in which a 60 percent straw ration was pelleted, feed conversion for the ration with adequate protein was better than any of these rations except the hydroxide-treated straw. Less waste may have been one reason. 20

22 It is likely that an amount of 20 to 30 percent grass straw would be more suitable for use with lambs. A recent report from Washington (Hackett et al., J. Animal Sci., 41:335) gave data on lambs fed pelleted rations containing 100 percent alfalfa; 75 percent alfalfa, 25 percent wheat straw; 50 percent alfalfa, 50 percent wheat straw; and 25 percent alfalfa, 75 percent wheat straw. Daily gains reported were, respectively: 0.37, 0.31, 0.19, and 0.18 pound per day. This indicates that 25 percent wheat straw could be used in pelleted rations for lambs without causing much reduction in daily gain. It also seems feasible to utilize some hydroxide-treated straw at a 20 to 30 percent level in finishing rations. This ration produced rather good results as compared to the others, and it has been demonstrated that hydroxide-treated straw improves digestibility to a greater degree than untreated straw. Overall, the feasibility of using hyroxide-treated straw will depend upon processing costs and the total cost as compared to alternates such as alfalfa hay. III. DIGESTIBILITY OF ANNUAL RYEGRASS STRAW Since only a limited amount of inormation has been published on the digestibility of grass straws, a digestion trial was conducted to evaluate three annual ryegrass products. Studies were conducted using a cubed sodium hydroxide-treated product and a cube made with the addition of 5 percent molasses, the same cubes fed to steers in the experiments discussed previously. Both of these products were provided by the Straw Utilization Center. The third product was chopped ryegrass straw. Sheep (or cattle) will not normally eat a maximum of poor quality roughage when fed alone, so a mixture of about 50 percent straw and 50 percent alfalfa hay was used. This mixture was fed to lambs in metabolism crates and data were obtained on digestibility. More detailed information will be reported later on the complete digestion trial. The analytical data on the three straws are shown in Table 12. Note that crude protein was lowest for the chopped straw and highest for the hydroxide-treated straw. Other reports often show that hydroxide treatment tends to result in lower crude protein content. Although the chopped straw was also obtained from the Straw Utilization Center, these values suggest that these straws were somewhat different in composition prior to treatment and that the hydroxide-treated straw may have been of slightly higher quality. Digestibility data obtained by feeding the mixture of straw and alfalfa show that dry matter digestion was improved considerably by treating the straw with sodium hydroxide. Crude protein digestion also 91

23 Table 12. Item Analytical values and digestion coefficients for the three annual ryegrass straw products Analytical values Dry matter (percent) Crude protein" (percent) Acid detergent fiber (percent) Digestion coefficients Dry matter (percent) Crude protein (percent) Total digestible nutrients (TDN) Hydroxide- Chopped Cubed with treated straw molasses and cubed (percent) Values are on 100 percent dry matter basis. Values calculated from digestible energy data. was improved with this treatment. In regard to protein, these results differ from some of the published data on other types of low quality roughage since this kind of treatment is more apt to reduce protein digestibility. \\'hether this is typical of ryegrass straw or a peculiarity of this particular experiment remains to be seen. Cubing resulted in a slight (not statistically different) depression in TDN digestibility. This might be anticipated since the addition of a material such as molasses sometimes decreases fiber digestibility, depending on the amount added (about 5 percent molasses in this case). Treatment of straw with hydroxide improved TDN content to 46 percent. This is typical of responses seen with most low quality roughages that have been treated with hydroxides or acids. The digestibility coefficients shown in Table 12 were calculated by subtracting the contribution of the alfalfa hay in the mixture. Generally, combining feeds such as straw with alfalfa enhances digestibility of the straw. Consequently, the values shown in Table 12 are undoubtedly higher than if the straw had been fed alone. However, the mixture was fed because it is not a common practice to feed only straw. IV. CONCLUSIONS 1. Cattle-feeding experiments with untreated annual ryegrass straw demonstrated that weanling calves performed in a very satisfactory manner when fed growing rations containing 25 percent chopped straw and finished on a ration with 12.5 percent straw. Calves fed pellets containing 50 percent straw did not gain nearly as well. 22

24 2. Weanling calves fed growing rations with 35 percent annual ryegrass straw and finished on a ration with 15 percent straw performed at a satisfactory level. When sodium hydroxide-treated straw was used in the rations, daily gain was increased by 0.4 pound per day during the growing phase and by about 0.25 pound per day during the total feeding period. Pelleted growing rations with 50 percent straw again did not support very high rates of gain, but 25 percent straw in a pelleted ration was satisfactory. On the whole, pelleting rations of this type are probably too costly for finishing cattle. 3. When yearling steers were fed rations with 30 percent hydroxide- treated bentgrass, annual ryegrass, or tetraploic rvegrass straw, daily gain and feed conversion were reduced in lots fed the tetraploid. However, results were too variable to make predictions and the fastest gaining steer was fed the ration with tetraploid ryegrass. 4. Steer calves were fed rations with about 40 percent annual ryegrass straw during the entire growing-finishing period. The lowest level of gain (2.59 lbs./day) resulted when the straw was chopped. Hydroxide treatment of straw increased daily gain to 2.74 pounds per day and improved feed conversion slightly' Feeding weathered and hydroxidetreated straw did not improve performance over the standard hydroxide treatment. 5. Fall calves or yearlings were fed rations with 40 percent annual rvegrass straw supplemented either with cottonseed meal or a mixture of dried poultry waste and feather meal. Daily gain was rather poor ( lbs./day). There were no differences in gains of cattle fed the different supplemental protein sources, but the cottonseed meal allowed somewhat better feed conversion. 6. Lambs fed pelleted rations containing about 60 percent annual ryegrass straw performed at a satisfactory level when the ration was supplemented with soybean meal (0.41 lb./day). When supplemental protein was not fed, rate of gain was reduced (0.30 lb./day), and the addition of urea increased gain slightly (0.33 ])./clay). Supplemental protein improved feed conversion considerably (from 9.00 to lbs. feed/ lb. gain). 7. Lambs were fed rations containing 50 percent perennial ryegrass straw that was untreated or treated with sodium hydroxide, and a combination of untreated and defiberized straw. Performance in terms of daily gain and feed conversion was reasonably satisfactory for those animals fed the ration with hydroxide heated straw (0.39 lb. gain/day and 9.7 lbs.

25 wi. mar.. = r feed/lb. gain). The other rations resulted in reduced rate of gain, very poor feed conversion, and high cost of gain. 8. Digestibility studies with straw indicate a TDN value of about 41 percent (dry basis) for untreated chopped annual ryegrass straw when fed with alfalfa. Treatment with hydroxide increased the TDN value to 46 percent. 24