Effect of exogenous fibrolytic enzymes supplementation on milk production and nutrient utilization in Murrah buffaloes

The present study was conducted to evaluate the effect of commercial exogenous fibrolytic enzyme (EFE) mixture added at 1.5 and 3.0 g (cellulase 4,000 μM glucose/g/h + xylanase 7,990 μM xylose/g/min; 50:50 w/w) per kilogram of dry matter (DM) of feed on nutrient digestibility, milk production, milk composition, and some blood constituents in lactating Murrah buffaloes. Eighteen buffaloes were allotted to three dietary treatments, on the basis of milk yield (8.48, 8.52, and 8.53 kg/day) and days in lactation (68.5, 80.33, and 82.00) for 90 days. The buffaloes were fed a total mixed ration (TMR) comprising of 45% chaffed wheat straw, 15% chopped green maize, and 40% concentrate on DM basis (control group), the same TMR plus EFE at 1.5 g/kg DM (T-1 group) and the same TMR plus EFE at 3.0 g/kg DM (T-2 group) supplemented through the concentrate mixture. There was no effect of fortifying EFE mixture on DM intake and crude protein intake (grams per day) whereas total digestible nutrients intake (kilogram per day) was higher by (P < 0.05) 12.53% in T-1 group over that of control, and there was no significant difference between T-2 and control groups. The average daily milk yield and 4% fat-corrected milk (FCM) yield was higher (P < 0.05) by 12.99% and 15.17% in T-1 group as over that of control, and there was no difference between T-2 and control groups. There was no (P > 0.05) difference in blood glucose and blood urea nitrogen concentration in different experimental groups. It is concluded that supplementation of cellulase and xylanase mixture at 1.5 g/kg of DM of TMR containing wheat straw (45%), green maize (15%), and concentrate (40%) on DM basis significantly increased (P < 0.05) the average daily milk yield and FCM yield in Murrah buffaloes due to improved dietary fiber digestion.     

外源酶提高反刍动物饲料利用率的研究进展

外源酶是提高反刍动物饲料利用率的一种新型饲料添加剂。酶是微生物发酵的产物,酶制剂的生产过程其实是一个发酵过程。反刍动物饲料酶制剂来自真菌（主要是长柄木霉、黑曲霉、米曲霉）和细菌（主要是枯草芽孢杆菌）。目前市场上的外源酶添加剂可分为两大类：一类是较纯的酶制剂,是经浓缩和纯化的,含有特定的酶,并有一定的活性,通常不含活细胞,如纤维素酶和木聚糖酶;另一类是粗发酵品和一些非细菌的直接饲喂的微生物（DFM）,含有一定量的酶。     

Effects of exogenous fibrolytic enzymes on ruminal digestibility in steers fed high fiber rations

The effects of two exogenous fibrolytic enzyme products on ruminal disappearance and fermentation of oat straw-wheat middlings based diets were evaluated. Six steers (322 ± 34.4 kg body weight) fitted with ruminal cannulas were used in a 3 × 3 Latin square replicated. The treatments consisted of: 1) control, 2) Fibrozyme (2 g/kg dry matter), and 3) Promote (3 ml/kg dry matter). Both, Fibrozyme (Alltech Inc.) and Promote NET (Cargill Corp.) were sprayed as liquid onto diets and feeds 24 h before feeding. Samples of diets were ruminally incubated from 0 to 72 h. Enzymes did not change dry matter intake, average daily gain and feed conversion. Fibrozyme increased crude protein (CP) disappearance rate of diet, while Promote increased CP total disappearance. In diets, enzymes did not affect ruminal neutral detergent fiber (NDF) and acid detergent fiber (ADF) fractions. Fibrozyme and Promote did increase CP total disappearance, ADF potential disappearance and ADF disappearance rate of wheat middlings, as well as dry matter (DM) and CP total disappearance, NDF disappearance rate, ADF potential disappearance and ADF disappearance rate of oat straw. Ruminal pH values were higher with enzymes, as compared to control. Total volatile fatty acids concentration and molar proportion of acetate and butyrate were not affected by both enzymes, but molar proportion of propionate was lower and acetate:propionate ratio higher with Promote than control. Fibrozyme and Promote did increase DM and CP soluble fractions of diets, as well as, ADF potential disappearance of wheat middling and oat straw.     

Effect of exogenous xylanase on rumen in vitro gas production and degradability of wheat straw

The objective of this study was to determine effects of xylanase on in vitro gas production (GP) and in sacco degradability of wheat straw. Rumen fluid was obtained from three Mongolian native goats fitted with permanent rumen cannulas. The trial consisted of five doses (0, 0.5, 1.0, 1.5, 2.0 μL/g of substrate) of a commercial xylanase (Dyadic^® xylanase PLUS, Dyadic International, Inc., Jupiter, FL, USA). For the in sacco degradability, different levels of xylanase enzyme were added directly onto 2 g of wheat straw in nylon bags and incubated in the rumen for 3, 6, 12, 24 and 48 h to estimate degradability of wheat straw. Total GP increased (P < 0.001) at all times of incubation at intermediate levels of xylanase. Methane production had a similar pattern at 3 and 12 h of incubation; increased linearly at 24 h of incubation, and was unaffected at 6 and 48 h of incubation. Rumen NH₃‐N concentration increased linearly at 3 h and the highest values were observed with intermediate enzyme levels. All ruminal volatile fatty acids increased linearly with intermediate levels of the fibrolytic enzyme. The in sacco rate of dry matter degradation decreased linearly (P = 0.020) with increasing enzymes. Intermediate levels of xylanase improved rumen kinetic fermentation and degradability. The outcome of this research indicated that the application of xylanase enzyme could improve in vitro GP fermentation of wheat straw.     

Treatment of tropical forages with exogenous fibrolytic enzymes: effects on chemical composition and in vitro rumen fermentation

The effects of three treatments of fibrolytic enzymes (cellulase from Trichoderma longibrachiatum (CEL), xylanase from rumen micro‐organisms (XYL) and a 1:1 mixture of CEL and XYL (MIX) on the in vitro fermentation of two samples of Pennisetum clandestinum (P1 and P2), two samples of Dichanthium aristatum (D1 and D2) and one sample of each Acacia decurrens and Acacia mangium (A1 and A2) were investigated. The first experiment compared the effects of two methods of applying the enzymes to forages, either at the time of incubation or 24 h before, on the in vitro gas production. In general, the 24 h pre‐treatment resulted in higher values of gas production rate, and this application method was chosen for a second study investigating the effects of enzymes on chemical composition and in vitro fermentation of forages. The pre‐treatment with CEL for 24 h reduced (p < 0.05) the content of neutral detergent fibre (NDF) of P1, P2, D1 and D2, and that of MIX reduced the NDF content of P1 and D1, but XYL had no effect on any forage. The CEL treatment increased (p < 0.05) total volatile fatty acid (VFA) production for all forages (ranging from 8.6% to 22.7%), but in general, no effects of MIX and XYL were observed. For both P. clandestinum samples, CEL treatment reduced (p < 0.05) the molar proportion of acetate and increased (p < 0.05) that of butyrate, but only subtle changes in VFA profile were observed for the rest of forages. Under the conditions of the present experiment, the treatment of tropical forages with CEL stimulated their in vitro ruminal fermentation, but XYL did not produce any positive effect. These results showed clearly that effectiveness of enzymes varied with the incubated forage and further study is warranted to investigate specific, optimal enzyme‐substrate combinations.     

添加外源纤维水解酶对羊草体外瘤胃发酵酶活性及特性的影响

试验通过分别添加纤维素酶与木聚糖酶0,10.0与50.0 mg水平,0与24 h两个预处理时间,每个处理3个重复,体外法评价纤维素酶与木聚糖酶复合处理羊草后与瘤胃液共培养对木聚糖酶与葡聚糖酶活性及发酵特性的影响。结果表明,添加纤维水解酶能提高0与8 h培养液中木聚糖酶和内切葡聚糖酶活性以及0 h培养液中外切葡聚糖酶活性,且具有添加剂量效应。当培养至24及48 h,添加外源酶制剂并不能提高培养液中相关酶活性。外源酶制剂显著增加培养24与48 h发酵液中乙酸含量,8,24与48 h 总挥发性脂肪酸产量 (P<0.05)以及48 h累积产气量(P<0.05),但对培养期内戊酸与异戊酸含量没有影响(P＞0.05)。结果提示添加外源酶制剂能提高早期培养液中木聚糖酶和葡聚糖酶活性、增加VFA产量和改善体外瘤胃发酵特性。     

Effect of exogenous fibrolytic enzyme on ruminal fermentation and digestibility of alfalfa and rye-grass hay fed to lambs

This experiment was carried out to study the effect of a directly fed exogenous fibrolytic enzyme on intake and digestion of DM, OM, protein, NDF, ADF, and hemicellulose of alfalfa and ryegrass hay by sheep. Four diets were randomly assigned to four ruminally cannulated lambs using a 4 x 4 Latin square design, repeated in time, with a factorial arrangement (2 x 2) of diets: 1) alfalfa hay; 2) alfalfa hay + exogenous fibrolytic enzymes (enzyme); 3) ryegrass hay; and 4) ryegrass hay + enzyme. Lambs consumed more DM and OM from alfalfa than from ryegrass hay (P < 0.001). The ADF intake was not different between the hays, but NDF intake was lower for alfalfa (P < 0.001). For both hays, the enzyme increased intake of DM (P < 0.01), as well as OM and CP (P < 0.05); however, NDF and ADF intake were not changed. Alfalfa hay had higher apparent digestibility of DM, OM, and CP (P < 0.001), but lower digestibility for NDF, ADF, and hemicellulose. The enzyme increased apparent digestibility of CP, hemicellulose (P < 0.05), and NDF (P < 0.10) for alfalfa. Also, for both hays, the enzyme improved N balance because lambs retained more N (P < 0.05). The enzyme increased (P < 0.05) total VFA concentration (3 and 6 h) for both hays. Results from this trial indicate that directly fed exogenous fibrolytic enzymes may change ruminal fermentation, intake, and digestibility of forages with different nutritive value.     

In vitro gas production of foliage from three browse tree species treated with different dose levels of exogenous fibrolytic enzymes

The aim of this study was to evaluate the effect of different dose levels of exogenous fibrolytic enzymes (EFE) on in vitro ruminal fermentation kinetics and energy utilization of foliages from three browse trees (Pithecellobium dulce, Heliocarpus velutinus and Guazuma ulmifolia). Mixture of EFE product was added to the leaves of the three browse tree species at three dose levels: 0 (control), 3.5 and 7.0 mg/g of DM. Chemical composition of the foliages, including plant secondary metabolites such as total phenolics (TP), saponins (SAP) and aqueous fraction (AF), was determined. In addition, in vitro assaying of ruminal gas production kinetics was determined for the three browse three foliages treated with EFE. P. dulce had the highest crude protein content (p < 0.05), whereas G. ulmifolia had the highest content of neutral detergent fibre and SAP (p < 0.05) and H. velutinus had the lowest content of TP (p < 0.05). The interaction between tree species and dose level of EFE was significant (p < 0.05) for gas production (GP) at 24 h of incubation, parameters b and c of the accumulated GP curve, short‐chain fatty acids (SCFA) and metabolizable energy (ME). The lowest (p < 0.01) extent of accumulated GP as well as the b and c values occurred in G. ulmifolia at 0 mg EFE/g DM. P. dulce had the highest (p < 0.05) values for ME and SCFA at the highest dose of EFE. Tree species and dose level had significant (p < 0.05) effects on all parameters describing in vitro ruminal fermentation kinetics and energy utilization. Addition of EFE improved the fermentation kinetics of the browse species considered in this study.     

添加纤维素复合酶制剂对羔羊日粮营养物质消化的影响

为研究纤维素酶制剂对羔羊消化性能的影响,选取体重相近、健康断奶的萨福克羊与小尾寒羊杂交一代4月龄羔羊60只,随机分为5组,分别为对照组(CP 18.54%,DE 13.04 MJ/kg)、低蛋白日粮加酶组(Ⅰ组CP 16.44%,DE 13.04 MJ/kg,复合纤维素酶0.2%)、低蛋白日粮组(Ⅱ组CP 16.44%,DE 13.04 MJ/kg)、低能量日粮加酶组(Ⅲ组CP18.54%,DE 12.26 MJ/kg,复合纤维素酶0.2%)、低能量日粮组(Ⅳ组CP 18.54%,DE 12.26 MJ/kg).饲喂30天后,采用全收粪法收集粪样.结果表明日粮能量水平和蛋白质水平影响羔羊对日粮营养物质的消化.降低日粮蛋白或能量水平显著降低了日粮DM、CP、EE、CF的消化率以及钙、磷吸收率.比较而言,能量水平对各种养分消化率的影响更大.同时,酶制剂作用效果受日粮能量水平的影响大于日粮蛋白质水平对其的影响;低蛋白日粮加入复合纤维素酶制剂有提高粗纤维消化率的趋势(但未达到显著水平,P＞0.05),不能提高粗脂肪的消化率和钙磷的吸收率;而低日粮能量水平添加加酶制剂,可以显著提高(P＜0.05)粗脂肪的消化率、钙的吸收率,但不能提高粗纤维的消化率,也不能改善磷的吸收率.     

Effects of exogenous fibrolytic enzymes on intake,duodenal flow,and digestion in steers fed diets with whole or cracked Pima cottonseed

Abstract

This study evaluated the effects of exogenous fibrolytic enzymes on intake, ruminal fermentation, and duodenal flow and digestion of nutrients in steers fed diets with whole Pima cottonseed (WPC) or cracked Pima cottonseed (CPC). Four Holstein steers (167±5 kg body weight) fitted with ruminal and duodenal cannulas with a 4×4 Latin square in a 2×2 factorial arrangement of treatments (WPC or CPC; 0 or 15 g enzyme) were used. Steers were fed wheat flaked-based diets with 9.95% of WPC or CPC as dry matter basis. Enzymes increased molar proportion of acetate in steer fed WPC, but in those fed CPC acetate decreased. Feeding enzymes increased duodenal flow of organic matter in steers fed WPC, but not in those fed CPC. Also, enzymes increased duodenal flow of N, non-ammonia N, and intestinal digestion of N in steers fed WPC and CPC.     

Effect of fortifying concentrate supplement with fibrolytic enzymes on nutrient utilization, milk yield and composition in lactating goats

Thirty lactating Beetle‐sannen crossbred goats were randomly divided into 3 groups based on first fortnight milk yield, and then adjusted to body weights to study the effect of fibrolytic enzyme supplementation on digestibility and milk production. Goats in the control group (C) were fed 500 g of concentrate supplement (CS) without exogenous fibrolytic enzymes (control; CG) or CS fortified with cellulase and xylanases @ of 4000 and 12500 (EG₁) or 8000 and 18 750 IU/kg (EG₂), respectively. CS was offered in two equal proportions just after milking at 7 and 17 h. After feeding CS, goats were fed 1200 g of wheat straw as roughage in two equal parts at 08.00 and 18.00 hours. Milk yield was studied for 3½ months. Milking was done by hand. Changes in body weight were also recorded. After a preliminary period of 60 days of feeding, a 7‐day digestibility trial was conducted in two intervals with 5 animals from each group at a time. The increase in either wheat straw or NDF intake due to the enzyme mixture was only 3%. There was significant improvement (P < 0.05) in the diet digestibility of DM, OM, CP, NDF, ADF and total carbohydrates (TC) between the control and EG₁ and EG₂ goats. Improvements were greater (P < 0.05) in the latter group. Microbial protein (MBP) was estimated based on purine derivatives and creatinine excreted in spot urine samples. MBP increased about 10 and 15% in EG₁ and EG₂, but these values were statistically invalid. Phenomenally milk yield, fat and SNF were significantly (P < 0.001) changed with progression of lactation. On a temporal basis, fortnightly changes in FCM yield of this study could be grouped as 1 month each of first and last and 1½ of middle phase of lactation. Repeated measure analysis showed 180 to 260 mL/day of higher FCM and 16 to 20 g/day of higher SNF yield (P < 0.001) in EG₂ than control or even EG₁ during 5 to 7^th fortnight. However, no significant impact (P > 0.05) was noticed on TF. Feed intake, g/kg FCM yield was also 7% less in EG₂ than either CG or EG₁. The study concluded that apart from increased digestibility, fortification of CS with cellulase and xylanases enzymes improved FCM yield in the last quarter of lactation in goats, and improved body weights by 5% (P > 0.05). While the digestibility of the diet was higher in EG₁ and EG₂, the impact on FCM and SNF yield was noticed only on EG₂. Our study indicated that CS of lactating goats may be fortified with 8000 and 18 500 IU/kg CS in the last quarter of lactation.     

Exposure to ammoniated wheat straw as suckling calves improves performance of mature beef cows wintered on ammoniated wheat straw

We studied how exposure to ammoniated wheat straw (AWS) early in life affected the performance of 32 mature crossbred beef cows (Bos taurus) (mean BW = 615 kg) wintered on AWS. Half (16) of these cows had been exposed as suckling calves to AWS for 66 d (Exposed), while the other 16 cows had no previous exposure to AWS (Na?ve). Five years after the initial exposure, cows were stratified by BW and bred into 8 groups of 4 cows each. Exposed and Na?ve cows occurred in each group, and groups of 4 cows were randomly assigned to one of eight pens. Cows were fed in these pens for a 150-d wintering period from December to May for 3 consecutive years. All cows were allowed ad libitum access to AWS and supplemented with alfalfa hay, vitamins, and minerals. Cows and their calves grazed irrigated meadow pastures for the remainder of the year. Cow BW and body condition score (BCS) were monitored monthly during the 3-yr study. Milk production was measured monthly from June to November of each year using the weigh-suckle-weigh technique. For all 3 yr, yearly average BW (P = 0.06, 0.03, 0.07) and BCS (P=0.07,0.001,0.01)were higher for Exposed than Na?ve cows. Postpartum interval (PPI) to rebreeding, monitored using consecutive calving dates, was shorter for Exposed than Na?ve cows during yr 1 and 2 (P = 0.004 and 0.02, respectively), but similar in yr 3 (P = 0.19). Exposed cows also produced more milk than Na?ve cows during yr 1 and 2 (P = 0.04 and 0.07, respectively), but milk production was similar in yr 3 (P = 0.74). Collectively, calves exposed to AWS briefly early in life performed better as cows when reexposed to AWS from 5 to 8 yr later in life. Thus, researchers and managers should consider previous exposure to low-quality forages (LQF) when assigning cattle to studies involving the use of LQF or when considering using LQF to reduce food costs.     

氨化麦秸饲喂育肥牛的效果试验

农作物秸秆经过氨化处理后饲喂育肥牛,增重效果十分显著,养牛的经济效益也随之提高.本试验的目的在于结合氨化麦秸饲喂育肥牛的确切效果,将麦秸更加合理的利用,以促进养殖业的发展.     

饲喂麦秸对湖羊消化道上皮形态的影响

为了研究饲喂麦秸对湖羊消化道上皮形态的影响,试验选取12只40 kg左右的健康公湖羊,预饲30 d后,随机分为2组,分别饲喂麦秸和苜蓿,日粮精粗比为6∶4,试验为期4周,试验结束时于晨饲前屠宰采集瘤胃、空肠及结肠上皮组织,切片比较各组的瘤胃、空肠和结肠的上皮形态。试验结果发现,与苜蓿组相比,麦秸组显著降低了瘤胃乳头的高度和面积(P0.05),对瘤胃上皮的角质层、颗粒层、棘层和基底层厚度没有显著的影响(P0.05);麦秸组显著降低了空肠的隐窝深度(P0.05),但对空肠的绒毛高度、绒毛高度与隐窝深度的比值(V/C)没有显著的影响(P0.05);饲喂麦秸增加了结肠上皮细胞的间隙。因此,饲喂麦秸改变了湖羊消化道的上皮形态,本研究为提高麦秸在反刍动物上的应用提供了基础数据。     

小麦型日粮添加复合酶对猪生产性能的影响

河南省是全国小麦主产区 ,小麦价格常低于玉米 ,许多养殖场纷纷用小麦代替玉米喂猪。现代科学研究证明 :小麦中的抗营养因子是可溶性非淀粉多糖 (ＳＮＳＰ) ,其主要成分为阿拉伯木聚糖和β -葡聚糖 ,两者分别占小麦 (干物质基础 )的1 8%和 0 4%。根据底物组成 ,在日粮中添加相应的酶制剂 ,可以切割ＳＮＳＰ ,钝化小麦中的抗营养因子。本试验用小麦替代日粮中不同比例玉米 ,并分别添加华芬酶Ｉ型和溢多酶 838Ａ ,观察其对生长肥育猪生产性能及胴体品质的影响。1　材料与方法1 1　试猪分组　试验选用杜×长×大三元杂交猪 99头 ,公母各半 ,…     

Influence of supplementary fibrolytic enzymes on the fermentation of corn and grass silages by mixed ruminal microorganisms in vitro

This study was done to determine the effectiveness of supplementary enzymes at increasing the fiber digestion by ruminal microorganisms and to assess whether enzyme activity limits the rate of fiber digestion in ruminal digesta. In vitro comparisons of enzyme activities in two feed enzyme preparations (A and B) with enzyme activities extracted from ruminal fluid indicated that the addition of fibrolytic enzymes at the application rates recommended by the manufacturers would not be expected to increase significantly glycanase and polysaccharidase activities in ruminal fluid. Preparations A and B both increased (P < 0.001) the rate of gas production from freeze-dried corn and grass silages in in vitro incubations with ruminal fluid, but only at concentrations much higher than recommended application rates. Autoclaved controls had little or no effect. Ultrafiltration of enzyme B indicated that most stimulation was due to components >100 kDa, which is consistent with the cause of the stimulation being enzyme activity. Fibrolytic enzymes from other sources were also able to stimulate gas production: increased rates of gas production were observed in seven out of eight combinations of "cellulase" and corn or grass silage (P < 0.05). The comparison of glycanase and polysaccharidase activities with gas-stimulatory activity in the different enzyme preparations indicated that the highest correlation was between increased gas production and enzyme activity against microgranular cellulose (P < 0.05). In a wider range of fibrolytic enzyme preparations, those with endo-(beta-1,4)- or exo-(beta-1,4)-xylanase activity equal to that of preparation A did not produce similar increased rates of fermentation of corn silage when glucanase activity was low (P > 0.05). In contrast, preparations with glucanase activity similar to enzyme A gave at least as great (P < 0.05) an improvement in gas production than enzyme A, irrespective of xylanase activity. It was concluded that enzyme activity, probably a type of endo-(beta-1,4)-glucanase activity, limits the rate of fermentation of corn and grass silage in the rumen. Enzyme supplements of the type used in these experiments are unlikely to possess sufficient activity to overcome this limitation by direct application to ruminal digesta, implying that treatment of the ration prefeeding will be key to harnessing the potential of exogenous fibrolytic enzymes in ruminant nutrition.     

Net energy value of ammoniated wheat straw

Eight steers (327 kg average) were fed diets containing either nontreated or anhydrous NH3-treated wheat straw in a two-period crossover design. Intake and digestibilities of dry matter, gross energy, neutral detergent fiber, acid detergent fiber and crude protein were measured by total collection. Energy losses in urine and methane were determined. Heat production was determined by indirect respiration calorimetry on steers fed both diets and after they were fasted. Ammoniation of the straw raised its N content from .49 to 1.59% (P less than .001). Dry matter (DM) intake was increased (P less than .01) by the process from 1.0 to 1.3% of body weight. Digestibility coefficients of dry matter and energy, as well as those for fiber, were increased (P less than .001) by four percentage units or more. Crude protein digestibility, however, was depressed (P less than .001) from 67.8% to 53.5% by ammoniation. Urinary energy as a percentage of gross energy intake (GEI) was reduced (P less than .05) by NH3 treatment from 4.10 to 3.74%. Methane energy was not different (P greater than .10). Metabolizable energy was improved (P less than .001) by ammoniation, increasing from 45.2 to 50.0% of GEI. Daily heat production was higher (P less than .01) for steers consuming the ammoniated straw diet, increasing from 113.7 to 125.3 kcal/wt.75), and was due to higher metabolizable energy intake (MEI) since partial efficiency of MEI used for maintenance did not differ (P greater than .10) between diets. The higher net energy value of the ammoniated wheat straw diet (1.45 vs 1.26 kcal/g DM) was due mainly to decreased fecal loss and a slight decline in urinary loss.     

Effect of method of applying fibrolytic enzymes or ammonia to Bermudagrass hay on feed intake, digestion, and growth of beef steers

This study examined how different methods of applying a fibrolytic enzyme or ammonia affect the nutritive value of Bermudagrass hay and the performance of beef cattle. Fifty Angus x Brangus crossbred steers (mean initial BW 244 +/- 26 kg) were individually fed for ad libitum intake of a 5-wk regrowth of a mixture of Florakirk and Tifton 44 Bermudagrass [Cynodon dactylon (L.) Pers] hay for 84 d with a concentrate supplement (77% soybean hull pellets, 23% cottonseed meal (DM basis) fed at 1% of BW daily. The Bermudagrass was conserved as hay without treatment (control), with NH(3) (30 g/kg of DM), or with a fibrolytic enzyme (16.5 g/t, air-dry basis) that was applied immediately after cutting (Ec), at baling (Eb), or at feeding. Chromic oxide was dosed to steers for 10 consecutive days, and fecal Cr concentrations from the last 5 d were used to estimate apparent total tract digestibility. In situ ruminal DM degradability was measured by incubating ground (4-mm) hay samples in duplicate in each of 2 ruminally cannulated cows having ad libitum access to Bermudagrass hay and 500 g/d of soybean meal. Unlike the enzyme treatment, ammoniation increased (P < 0.001) the CP concentration and reduced (P < 0.001) NDF, hemicellulose, and lignin concentrations of hay. Total DMI was greater (P < 0.05) for steers fed hays treated with Ec or NH(3) than for those fed control hays. All additive treatments increased (P < 0.05) DM digestibility, and NH(3), Ec, and Eb treatments also increased (P < 0.01) NDF digestibility. The initial and final BW, ADG, BCS, G:F, and hip height of the steers were not affected (P > 0.05) by treatment. The wash loss fractions in hays treated with Ec and Eb were lower than that in the control hay, but the potentially degradable fraction, total degradable fraction, and the effective degradability were increased (P < 0.01) by NH(3) treatment. Application at cutting was the most promising method of enzyme treatment, and this treatment was almost as effective as ammonia for enhancing forage quality.