Effect of maceration on nitrogen fractions in hay and silage

Transcription

1 maceration on nitrogen fractions in hay and silage Y. R. Agbossamey 1, P. Savoie 2,3, and J. R. Seoane 1 1 Département des sciences animales, Université Laval, Québec, Canada G1K 7P4; 2 Agriculture et Agroalimentaire Canada, Soils and Crops Research and Development Centre, Université Laval, Québec, Canada G1K 7P4. Contribution no. 584, received 9 January 1998, accepted 19 May Agbossamey, Y. R., Savoie, P. and Seoane, J. R maceration on nitrogen fractions in hay and silage. Can. J. Anim. Sci. 78: An intensive mechanical conditioning treatment, referred to as maceration, was applied at mowing to alfalfa or timothy in order to enhance drying rate, reduce wilting time and possibly reduce respiration losses and proteolysis. In 1995, a laboratory trial was conducted using two levels of force (1750 and 3500 Newton) and five levels of conditioning: a control (no conditioning), one passage, three passages, five passages and seven passages through two steel knurled rolls. All forages were dried in a controlled environment at 30 C and conserved as hay. The level of force did not affect the chemical composition of the forages obtained. However the nitrogen (N) fractions were affected by the level of maceration. As the level of conditioning increased, the soluble N fractions (A and B1) of both forages decreased (P < 0.001). Meanwhile, the slowly degradable N fraction (B3) increased linearly (P < 0.001) in timothy and quadratically (P < 0.003) in alfalfa. The fraction of unavailable N (fraction C) also increased linearly (P < 0.01) with intensity of maceration. In 1996, alfalfa was conditioned in the field at four intensity levels: a control (rubber roll-conditioning), one passage, two passages, and three passages through a full-size mower-macerator with three knurled rolls. The alfalfa dried under poor climatic conditions with alternating rain and sunshine and was conserved as silage at 30% dry matter (DM) after a 40-h wilt or as hay after a 90-h wilt. Neutral detergent fibre (NDF), acid detergent fibre (ADF), and ash contents increased linearly (P < 0.001) with the level of maceration; the increase was greater in hay than in silage. The non protein nitrogen (fraction A) decreased (P < 0.001) while fraction B3 and unavailable N (fraction C) increased (P < 0.001) with level of maceration. The results suggest that maceration decreases the extent of proteolysis during conservation and preserves a higher proportion of the slowly degradable N (escape nitrogen). Key words: Forage, maceration, chemical composition, nitrogen fractions Agbossamey, Y. R., Savoie, P. et Seoane, J. R Effet du surconditionnement sur les fractions azotées du foin et de l ensilage. Can. J. Anim. Sci. 78: Un surconditionnement mécanique intense a été appliqué lors de la fauche de la luzerne et de la fléole des prés dans le but d accélérer la vitesse de séchage, de réduire le temps de fanage et de réduire possiblement les pertes dues à la respiration et à la protéolyse. En 1995, une expérience a été menée au laboratoire en utilisant deux niveaux de force (1750 et 3500 Newton) et cinq niveaux de conditionnement: un témoin (aucun conditionnement), un passage, trois passages, cinq passages et sept passages du fourrage à travers deux rouleaux broyeurs. Les fourrages ont été séchés à 30 C dans un environnement contrôlé et ont été conservés sous forme de foin. La force appliquée au surconditionnement n a pas affecté la composition chimique des fourrages. Toutefois, le niveau de surconditionnement a affecté les fractions azotées des fourrages. Au fur et à mesure que l intensité du conditionnement augmentait, les fractions d azote soluble (A et B1) diminuaient dans les deux fourrages. Cependant, la fraction lentement dégradable (B3) a augmenté de façon linéaire (P < 0,001) chez la fléole et de façon quadratique (P < 0,003) chez la luzerne. La fraction azotée non dégradable (C) a augmenté aussi de façon linéaire (P < 0,01) suite au surconditionnement. En 1996, quatre niveaux de conditionnement ont été appliqués à la luzerne fraîche au champ: un témoin (conditionnement conventionnel avec des rouleaux de caoutchouc), un passage, deux passages et trois passages à travers un mécanisme à trois rouleaux broyeurs. La luzerne a séché dans des conditions climatiques médiocres avec alternance de pluie et d ensoleillement et a été ensuite conservée sous forme d ensilage à 30% de matière sèche après 40 h de fanage, ou sous forme de foin après 90 h de fanage. Les teneurs en fibres NDF et ADF et en cendres ont augmenté de façon linéaire (P < 0,001) avec le niveau de surconditionnement, l augmentation étant plus marquée pour le foin que pour l ensilage. La fraction d azote non protéique (A) a diminué (P < 0,001) tandis que l azote faiblement dégradable (fraction B3) et l azote non disponible (fraction C) ont augmenté (P < 0,001) avec le niveau de surconditonnement. Les résultats suggèrent que le surconditionnement diminue le degré de protéolyse durant la conservation des fourrages et protège une forte proportion de l azote lentement dégradable dans le rumen. Mots clés: Fourrages, surconditionnement, composition chimique, fractions azotées Application of heat during wilting or during ensiling has been shown to reduce proteolysis in forages (Charmley and Veira 1990a,b). Steam treatment at 85 C for 1 min and heating at 100 C for 2 min inhibited protease activity and reduced protein catabolism in the silo, thus resulting in increased efficiency of microbial protein synthesis in the 3 To whom correspondence should be addressed. psavoie@grr.ulaval.ca. 399 rumen (Charmley and Veira 1990a). Furthermore, heat treatment of silages increased true protein, decreased ammonia N, and increased N utilization in lambs (Charmley and Veira 1990b). Other studies have shown that the use of Abbreviations: ADF, acid detergent fibre; ADIN, acid detergent insoluble nitrogen; CF, crude fibre; DM, dry matter; NDF, neutral detergent fibre; NPN, non-protein nitrogen; TCA, trichloroacetic acid

2 400 CANADIAN JOURNAL OF ANIMAL SCIENCE heat increases the escape protein fraction of alfalfa and the acid detergent insoluble N fraction (ADIN), which may reach 17% of total N in hay (Broderick et al. 1993; Yang et al. 1993). In normal feeds, ADIN ranges from 3 to 15% of total N (Van Soest 1994). The critical value of ADIN is considered to be between 12 and 15%; above this range, heat damage of silages generally occurs (Mahanna 1997). An intensive mechanical treatment of forages, such as maceration, has been shown to increase field drying rate (Savoie et al. 1993) and to improve fermentation characteristics of silage (Charmley et al. 1997). Thus, maceration could be an alternative to heat application in order to optimize N utilization by ruminants without increasing unavalaible N. Maceration increased intake and digestibility of alfalfa and timothy hays fed to cattle and sheep (Hong et al. 1988; Petit et al. 1994). Kraus et al. (1997) observed that, after 8 to 10 h of conditioning, the rate of respiration of severely treated alfalfa increased rapidly to approximately twice the initial rate of the unconditioned forage. The sudden increase of CO 2 production may be due to improved microbial activity or enhanced availability of soluble carbohydrates after an incubation or lag time. Thus, intense maceration affects the rate of biochemical reactions taking place in the plant. The present experiments were conducted to study the effect of roll force and level of maceration on the chemical composition and the N fractions of hay and silage treated under laboratory and field conditions. MATERIALS AND METHODS Sites, Harvest of Forages and Macerating Procedure EXPERIMENT 1. Timothy (Phleum pratense) and alfalfa (Medicago sativa L.) were mowed in the summer of 1995 with a sickle bar mower without conditioning at the Normandin Research Farm in northern Québec. A field of each species was divided into three replications. Timothy was cut at the stage of early heading on 21 June and alfalfa was cut on 28 June at the stage of 10% bloom. After mowing, the fresh forage was transported to the laboratory for treatment with an experimental stationary macerator described by Savoie et al. (1996). Five conditioning treatments were applied: a control (forage without any conditioning), one passage, three passages, five passages and seven passages through two steel-knurled rolls. Two different forces were applied by spring loading to the 600-mmwide upper roll of the macerating apparatus: 1750 or 3500 Newton. Forages were dried during a 4-d period by changing the temperature to simulate field conditions as follows. A 1-kg representative sample of each treatment was spread out on a metallic grate and dried in a controlled environment. To simulate good natural drying condition, the temperature of the growth chamber was adjusted at 30 C during 12-h followed by 2-h at 20 C and then turned off during the night. The same drying procedure was repeated for the next three days. EXPERIMENT 2. Alfalfa (Medicago sativa L.) was mowed at 10% bloom on 14 June 1996 at the Lennoxville Research Station in southern Québec. A 1.0-ha field was divided into eight blocks and each block was randomly assigned to one of the following treatments: 1) a control hay (one passage through rubber rolls), 2) lightly macerated hay (one passage through three knurled steel rolls), 3) moderately macerated hay (two passages), 4) intensely macerated hay (three passages), 5) a control silage (conventional mowing-conditioning), 6) lightly macerated silage (one passage through three knurled steel rolls), 7) moderately macerated silage (two passages), 8) intensely macerated silage (three passages). Field drying conditions were poor during the first 48 h with alternating rain and sunshine but became excellent during the next two days. Precipitation was 0.2, 2.8 and 0.2 mm d 1 on 14, 15 and 16 June, respectively. Solar radiation was 15.6, 20.1, 29.3, 23.8, and 30.9 MJ m 2 d 1 on 14 to 18 June, respectively. Silage was harvested after 43 to 48-h of wilting at 62 to 72% moisture while hay was harvested after 92 h of wilting at 11 to 14% moisture. Silages were stored in 204-L steel drums protected in the interior with two plastic bags. Pressure was applied to the material at three different times before sealing each drum to obtain a wet density similar to average densities observed in tower silos (densities in drums ranged between 300 and 370 kg m 3 ). Physical and Chemical Analyses Compressibility of freshly conditioned forage was determined according to the procedure described by Savoie et al. (1996) and expressed as the wet density (kg m 3 ). The freshly mowed forage was compressed in a cylinder under a pressure of 6.45 kpa. Prior to chemical analysis, silage samples were freezedried and all forage samples were ground through a 1-mm screen (Wiley mill, Standard Model 3, Arthur H. Thomas Co., Philadelphia, PA). Dry matter content was determined by weight difference following oven-drying at 105 C for 24 h. Crude protein (N 6.25) was measured by the Kjeldahl procedure (method No , Association of Official Analytical Chemists [AOAC] 1990) using a Kjel-Foss apparatus (model 16210, A/S N, Foss Electric, HillerØd, Denmark). Ash was measured by incineration at 600 C overnight (method No [AOAC 1990]) in a muffle furnace (Model F-A 1730, Thermolyne Corporation, Dubuque, IA). Samples were also analyzed for ADF (method No [AOAC 1990]) and crude fibre (method No [AOAC 1990]) using a Tecator apparatus (Fibertec System, model 1010 Heat Extractor, Höganäs, Sweden). Neutral detergent fibre was determined by the procedure of Van Soest et al. (1991). Insoluble nitrogen remaining in NDF and ADF residues was determined using the Kjeldahl procedure. Protein N was measured as trichloroacetic acid (TCA) insoluble N according to the method of Siddons et al. (1979). Nonprotein N was considered to be the difference between total N and protein N. Insoluble N in a borate-phosphate buffer was measured according to the method of Krishnamoorthy et al. (1982) modified by Roe et al. (1990). Soluble N in the borate-phosphate buffer was considered to be the difference between total N and insoluble N (Krishnamoorthy et al. 1982). Total N was fractionated according to Sniffen et al. (1992) into

3 AGBOSSAMEY ET AL. MACERATION AND N FRACTIONS OF FORAGES 401 Table 1. force against the upper roll and intensity of maceration (number of passages through two rolls) on dry matter of fresh forage and density after the compressibility test (exp. 1) Force of 1750 Newton Force of 3500 Newton Item 0 z SEM y passage x Timothy Dry matter (%) NS Density (kg m 3 ) L Alfalfa Dry matter (%) NS Density (kg m 3 ) L z Number of passages through two macerator rolls; 0 is the control treatment. y Standard error of the mean (n = 3). x L=linear effect of passage; NS=nonsignificant (P > 0.10); quadratic effect of passage and main effect of force were not significant. fractions A + B1 which are soluble in borate-phosphate buffer, fraction A (NPN, soluble in TCA solution), fraction B1 (insoluble in TCA solution but soluble in borate-phosphate buffer), fraction B2 (N insoluble in borate-phosphate buffer minus N insoluble in a neutral detergent solution), fraction B3 (insoluble N in neutral detergent minus insoluble N in acid detergent) and fraction C (acid detergent insoluble N, unavailable N). Fractions B1, B2 and B3 are considered as protein N; they are respectively highly degradable, intermediately degradable and slowly degradable in the rumen according to the classification of Sniffen et al. (1992). All values for the different N fractions were expressed as percent of total N. Statistical Analyses The experimental data were analyzed using the General Linear Models procedure of SAS Institute, Inc. (1985). All data of exp. 1 were subjected to an analysis of variance according to a complete block design with three replications (Steel and Torrie 1980) and a 2 5 factorial arrangement of treatments (two levels of force and five numbers of passages between the macerating rolls). For exp. 2, all data were analyzed as a completely randomized design by analyses of variance and according to a 4 2 factorial arrangement (four levels of maceration and two methods of conservation, silage or hay). Treatment sums of squares were partitioned to provide orthogonal contrasts (Steel and Torrie 1980) to determine the type of response (linear, quadratic, cubic or quartic, according to the experimental design). RESULTS AND DISCUSSION Forage Compressibility In exp. 1, fresh forage density was not affected by the force applied to the rollers but increased linearly (P < 0.001) with the intensity of maceration for both species while dry matter remained relatively constant (Table 1). As the number of passages through the rollers increased, density, averaged for both levels of force, increased from 138 to 322 kg m 3 for timothy and from 189 to 428 kg m 3 for alfalfa. Density of alfalfa was higher than that of timothy, which is in agreement with findings of Seoane et al. (1981, 1982) who noted that the volume occupied by timothy was significantly higher than that occupied by alfalfa. These results are also in agreement with those reported by Savoie et al. (1996) who observed a good correlation between compressibility and the intensity of mechanical conditioning of fresh forage. Similar results were obtained in the second experiment (data not presented). The density of alfalfa increased linearly (P < 0.001) and values were 202, 217, 334, and 412 kg m 3 for conventional mowing-conditioning, light, moderate, and intense maceration, respectively. Changes in Chemical Composition EXPERIMENT 1. The chemical composition of timothy and alfalfa was generally not affected, either by macerating roll force or by macerating intensity (number of passages through rolls). Values reported in Table 2 represent averages of three replications and two forces levels. Maceration is known to increase leaf loss in alfalfa with little effect on timothy (Hong et al. 1988; Chiquette et al. 1994; Petit et al. 1994, 1997). However, in the controlled environment, no loss of dry matter was detected during drying and the effect of maceration on CP, NDF, and ADF was nonsignificant. Maceration caused a slight decrease of crude fibre in timothy only (27.2 vs. 28.4%). Charmley et al. (1997) also observed no significant change in the main chemical components of alfalfa after maceration followed by drying in a controlled environment and ensiling in laboratory silos. Total nitrogen averaged 2.19% of timothy DM and 2.70% of alfalfa DM. The nitrogenous fractions of timothy and alfalfa hays were not affected by force but were affected by intensity of maceration (Tables 3 and 4). As maceration intensity increased, the N fraction soluble in a borate buffer (fraction A + B1) decreased linearly (P < 0.001) from 37 to 31% of total N for timothy (Table 3) and from 50 to 37% for alfalfa (Table 4). The rapidly degradable protein fraction (B1) also decreased linearly (P < 0.002) with increasing maceration in timothy but not in alfalfa. Values obtained for fraction B1 in this experiment were higher than those observed by Fox et al. (1990) who reported values of only 1% for legume hay and silage. High values of fraction B1 may be explained by the short time period between cutting and the onset of drying in a controlled environment. In fresh forages, fraction B1 represents a large part of the soluble protein while in conserved forages, this fraction is small because of its conversion into non-protein N (Sniffen et al. 1992). The effect of intensity of maceration on the intermediately degradable protein fraction (B2) was different for each

4 402 CANADIAN JOURNAL OF ANIMAL SCIENCE Table 2. intensity of maceration (number of passages through two rolls) on chemical composition of timothy and alfalfa hays dried in the laboratory z (exp. 1) Maceration intensity Item 0 y SEM x passage w Timothy Crude protein (%) NS NDF (%) NS ADF (%) NS Crude fibre (%) Ash (%) NS Alfalfa Crude protein (%) NS NDF (%) NS ADF (%) NS Crude fibre (%) NS Ash (%) NS z All values on dry matter basis. y Number of passages through two macerator rolls; 0 is the control treatment. x Standard error of the mean (n = 6). w NS=nonsignificant (P > 0.10). Table 3. intensity of maceration (number of passages through two rolls) on nitrogen fractions of timothy hay z (exp. 1) Maceration intensity Item 0 y SEM x passage w A + B1 v L A Q B L B L B L C L z All values on total nitrogen basis. y Number of passages through two macerator rolls; 0 is the control treatment. x SEM=standard error of the mean (n = 6). w L=linear effect, Q=quadratic effect, NS=nonsignificant (P > 0.10). v A+B1= N soluble in borate buffer; A= N soluble in TCA and in borate buffer; B1= N soluble in borate buffer and insoluble in TCA; B2=borate buffer insoluble N neutral detergent insoluble N [B2+B3+C (B3+C)]; B3=neutral detergent insoluble N acid detergent insoluble N [B3+C (C)]; C=acid detergent insoluble N. forage. Fraction B2 decreased with increasing maceration in timothy (Table 3) but it increased in alfalfa (Table 4). This suggests that the type of protein contained in fraction B2 of grasses reacts differently to maceration compared with the type of protein contained in fraction B2 of legumes. Similar results were obtained after freezing by Kohn and Allen (1992). They observed that the B2 fraction of bromegrass decreased markedly from 39.9 to 30.0% after freezing at 25 C for 24 h, while the same fraction in alfalfa showed a small increase of 3.8%. Intensity of maceration affected the slowly degradable protein fraction (B3) and the non-degradable nitrogen fraction (C) of both forages. Fraction B3 increased from 20 to 29% in timothy and from 3 to 7% in alfalfa. Meanwhile, fraction C increased from 4.5 to 6.2% in timothy and from 7.7 to 8.8% in alfalfa as the level of maceration increased. The increase in fraction C was considerably lower than values found by Yang et al. (1993) and Broderick et al. (1993) using heat to increase net escape protein of forages. Compared with the control, macerated forages were darker in colour and the visual difference increased with the level of maceration. Colour of the plant material may help understand the changes observed in the nitrogen fractions. Kohn and Allen (1992) observed that frozen samples were darker in colour compared to fresh forage. They suggested that enzymes may be activated by peroxide produced when plant cells are damaged during freezing and thawing. These enzymes may create strong bonds between proteins and carbohydrates that are acid stable. Therefore, the acid detergent fraction (fraction C) would increase, as observed in the present study. Ajibola et al. (1980) also studied colour changes following maceration of forages. They noted that maceration reduced considerably light reflectance and increased absorptivity of solar energy compared with control forage. An increase of absorptivity of solar energy could decrease proteolysis and explain the lower levels of soluble protein observed when forages undergo maceration. EXPERIMENT 2. Dry matter content averaged 87.6% for hay (Table 5). The DM contents were 34.6, 28.0, 38.3 and 33.7% for control, lightly, moderately, and intensely macerated silages, respectively (Table 5). The difference in DM of

5 AGBOSSAMEY ET AL. MACERATION AND N FRACTIONS OF FORAGES 403 Table 4. intensity of maceration (number of passages through two rolls) on nitrogen fractions of alfalfa hay dried in the laboratory z (exp. 1) Maceration intensity Item 0 y SEM x passage w A + B1 v L A Q B NS B L B L, Q C L z All values on total nitrogen basis. y Number of passages through two macerator rolls; 0 is the control treatment. x SEM=standard error of the mean (n = 6). w L=linear effect, Q=quadratic effect, NS=nonsignificant (P > 0.10). v A+B1= N soluble in borate buffer; A= N soluble in TCA and in borate buffer; B1= N soluble in borate buffer and insoluble in TCA; B2=borate buffer insoluble N neutral detergent insoluble N [B2+B3+C (B3+C)]; B3=neutral detergent insoluble N acid detergent insoluble N [B3+C (C)]; C=acid detergent insoluble N. Table 5. storage method (hay or silage) and intensity of maceration (number of passages through three rolls) on chemical composition of alfalfa dried in the field z (exp. 2) Hay Silage Probability y Item 0 x SEM w S P S P L Q DM (%) NS NS CP (%) NS 0.01 NS NS NDF (%) NS NS ADF (%) NS NS Cell content (%) NS NS Ash (%) NS NS z All values on dry matter basis, except of dry matter. y S= storage method effect; P= main effect of passage; L=linear effect of passage; Q=quadratic effect of passage; NS=nonsignificant (P > 0.10). x Number of passages through three macerator rolls. w Standard error of the mean (n = 8). silages is explained partly by differences in the field wilting time: the four silage plots were mowed between 19:00 and 21:00 h on 14 June and harvested between 13:00 and 20:00 on 16 June. The four hay plots were harvested between 14:00 h and 15:00 h on 18 June. Silages had higher levels of protein and cell contents and lower NDF and ADF than hay (P < 0.001). Such differences have been previously observed (Petit et al. 1985) and may be due in part to higher leaf loss when harvested for hay and in part to fibre hydrolysis when conserved as silage. The NDF, ADF, and ash contents increased linearly (P < 0.001) with intensity of maceration. These results agree with those of Hong et al. (1988) who observed higher NDF and ADF contents in shredded hay than in a control. Maceration increased fibre content and decreased CP content of alfalfa hay possibly because of a greater leaf loss during drying, handling, and storage (Hong et al. 1988). The detrimental effect of maceration on forage quality increased with the level of conditioning. However in the present study, chemical composition of lightly macerated hay was not significantly different from the chemical composition of the control hay. High levels of NDF and ADF in the field study were probably accentuated by the loss of soluble material during rainfall. Alfalfa nitrogen fractions were significantly modified by the method of conservation and by intensity of maceration in the field (Table 6). Non-protein N (fraction A) was significantly higher (P < 0.001) in silage than in hay, while protein fractions (B1, B2, and B3) were higher in hay. The high level of NPN in silage results from prolonged proteolysis due to high moisture conditions. Intense maceration produced a linear decrease in fraction A of hay and silage. Fraction A decreased from 26% in control to 11% in 3 macerated hay; and from 55 to 37% in silage. Meanwhile, fraction B1 increased with intensity of maceration (P < 0.001). Therefore, maceration decreased the NPN (fraction A) and increased the soluble protein fraction (B1) in hay and silage, which indicates a decrease in proteolysis. These results agree with those of Charmley et al. (1997) who observed that TCA insoluble N concentration was higher in macerated silage than in a nonmacerated control; the effect was more important in wilted than in unwilted silage. The effect of maceration on fraction B2 was different depending on the method of conservation. Fraction B2 decreased from 46.4 to 42.0% of total N in hay, but increased from 31.9 to 40.1% in silage, thus resulting in a significant interaction between the method of storage and the maceration level or number of passages (P < 0.001, Table 6). Maceration produced a linear increase (P < 0.001) of fraction B3, from 9.2 to 21.8% in hay and from 4.2 to 8.1% in silage (Table 6). There was also an increase of unavailable N (fraction C) under moderate (2 ) and intense (3 ) maceration compared with the control. Maceration increased linearly (P < 0.002) the fraction C and the effect was more important in hay than in silage. Furthermore, unavailable N was higher in hay than in silage (11.9% versus 8.4%). These findings do not agree with those of Fox

6 404 CANADIAN JOURNAL OF ANIMAL SCIENCE Table 6. storage method (hay or silage) and intensity of maceration (number of passages through three rolls) on nitrogen fractions in alfalfa dried in the field (exp. 2) Hay Silage Probability x Item 0 z SEM y S P S P L Q A + B1 w NS NS A NS NS B NS 0.02 NS B NS NS B NS C NS NS z Number of passages through three macerator rolls. y Standard error of the mean (n = 8). x S= storage method effect; P= main effect of passage; L=linear effect of passage; Q=quadratic effect of passage; NS=non significant (P > 0.10). w A+B1=N soluble in borate buffer; A=N soluble in TCA and in borate buffer; B1=N soluble in borate buffer and insoluble in TCA; B2=borate buffer insoluble N neutral detergent insoluble N [B2+B3+C (B3+C)]; B3=neutral detergent insoluble N - acid detergent insoluble N [B3+C (C)]; C=acid detergent insoluble N. et al. (1990) who reported that ensiling forages increases fraction C. On the other hand, Merchen and Satter (1983) observed that the amount of unavailable N in alfalfa was higher in 66% DM silage compared to silages containing 29 and 40% DM. Control and lightly macerated hays had a similar content of fraction C (10.5% of total N); this level has been commonly reported for early bloom alfalfa hay in several studies (Fox et al. 1990; Kohn and Allen 1992; Sniffen et al. 1992). The increase in the unavailable N fraction was not as high as that observed after heat treatment of forages (Broderick et al. 1993; Yang et al. 1993). CONCLUSION Under controlled laboratory conditions, maceration did not affect fibre content of forage. In the field, moderate maceration did not affect fibre content but intense maceration increased fibre content and potentially decreased the nutritive value of forages. Nitrogen fractions were affected by the level of maceration both in the controlled environment and in the field. Maceration decreased the soluble N fraction and increased the proportion of slowly degradable N (escape nitrogen). This effect was greater in hay than in silage. ACKNOWLEDGEMENTS The authors acknowledge the collaboration and the technical assistance of A. Roy and J. Bricault at Université Laval. They also wish to thank the staff at the Normandin Research Farm. This project was supported in part by a grant from the Matching Investment Initiative of Agriculture and Agri- Food Canada in cooperation with MacDon Industries and Falher Alfalfa Ltd and in part by the Natural Sciences and Engineering Research Council of Canada. Ajibola, O., Koegel, R. and Bruhn, H. D Radiant energy and its relation to forage drying. Trans. ASAE (Am. Soc. Agric. Eng.) 23: Association of Official Analytical Chemists Official methods of analysis. 15th ed. AOAC, Washington, DC. Broderick, G. A., Yang, J. H. and Koegel, R. G steam heating alfalfa hay on utilization by lactating dairy cows. J. 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