Nutritive Value of Alfalfa Haylage-Dairy Waste Fiber Mixtures for Dairy Heifers1

Nutritive Value of Alfalfa Haylage-Dairy Waste Fiber Mixtures for Dairy Heifers 1 H. R. NEWMAN, JR., 2'3 E. H. JASTER, 2 G. C. F A H E Y , JR., 4 and R. P. W A L G E N B A C H s'6 University of Illinois Urbana 61801 ABSTRACT

acid detergent insoluble nitrogen. It appears that alfalfa-dairy waste fiber mixtures can be ensiled successfully but that utilization of the mixtures by dairy heifers is impaired because of either heat damage or nature of the fiber in dairy waste.

The objective was to study the influence of adding dairy waste fiber to alfalfa of two maturities on nutrient intake and digestibility by Holstein heifers. Changes associated with delayed harvest of first spring-growth alfalfa also were characterized. Spring growth of alfalfa from a common field was cut at two maturities, late bud and 50% flower. Fresh dairy waste fiber was obtained by processing manure, by a roller press liquid/solid separator, from lactating Holstein cows fed a 57% roughage diet. Alfalfa haylage was mixed and ensiled with three concentrations of dairy waste fiber (0, 20, or 40% dry matter). Thirtyfive Holstein heifers (initial weight 339 kg) consumed one of six diets (early cut control, no waste; early cut, low waste; early cut, high waste; late cut control, no waste; late cut, low waste; late cut, high waste) ad libitum in a 19-day digestion study. Delaying first harvest of alfalfa increased concentrations of stems, neutral detergent fiber, acid detergent fiber, and acid detergent lignin and decreased concentrations of leaves, total nitrogen, and calcium. Increasing dietary concentrations of dairy waste fiber decreased dry matter intakes and digestibilities and increased dietary fiber concentrations and ratios of acetate:propionate. Apparent nitrogen digestibility decreased as dairy waste fiber increased. Heat damage was in all diets with controls containing .87%

INTRODUCTION

Received November 1, 1982. I Supported by Illinois Agricultural Experiment Station -- Hatch 35-356. 2Department of Dairy Science. 319923 Upas Rd., Culver, IN 46511. 4 Department of Animal Science. s Department of Agronomy. 6 US Dairy Forge Center, 1925 Linden Drive West, Madison, WI 53706.

1983 J Dairy Sci 66:1094--1100

Dairy farms are becoming intensively automated, and producers are examining ways of reducing labor and other inputs required for farm operation. One area that has received increased interest is waste management. Conventional systems tend to be labor intensive with little or no return from the waste. Liquid or slurry systems have gained popularity because of their reduced labor requirement. There is a greater return from nutrients in waste because of conservation practices associated with slurry systems. Special interest has been placed on separating waste into a solid, fibrous fraction, which has a chemical composition similar to that of mature grass hays, and the effluent, which retains most of the fertilizer value of the original slurry. Jaster et al. (13) fed dairy waste fiber (DWF) ensiled with corn silage at 0, 15, and 30% of diet dry matter (DM) to dairy heifers. Ensiling characteristics were acceptable and DM intake increased as DWF increased while DM digestibility decreased. Staples et al. (19) fed alfalfa haylage with DWF at 0, 25, and 50% of diet DM to sheep and found that DM intake and digestibility decreased as DWF increased. Screened manure solids providing 0, 22, or 44% of dietary crude fiber did not depress milk production or DM intakes by lactating Holstein cows (17). Alfalfa is capable of supporting growth of replacement dairy heifers from 6 mo of age until the time they start milking. High quality alfalfa supports moderate milk production without supplemental concentrate feeding. Research has been extensive on alfalfa and effects of delayed cutting of spring growth

1094

ALFALFA HAYLAGE-DAIRY WASTE FIBER MIXTURES on forage quality. Spahr et al. (18) reported decreased DM intakes, milk production, and DM digestibility as cutting was delayed. Other workers (5, 8, 9) also characterized changes associated with maturation of alfalfa. Decreases of the proportion of leaves and decreases of DM intake, nitrogen (N) concentration, and nutrient digestibilities of the forage occurred with advancing maturity. Concentration of fibrous components and of proportion of stems also have increased. Dairy producers currently are faced with rising costs associated with raising replacement heifers. When harvested as a high quality silage, alfalfa provides nutrients in excess of the dairy heifer's requirements. To allow for maximal utilization of available resources, it appears feasible to feed high quality alfalfa diluted with a lower quality roughage such as DWF. Therefore, our objective was to study the influence of adding DWF to two maturities of alfalfa commonly harvested by dairy producers on nutrient intake and digestibility. Changes associated with delaying the harvest of first spring growth of alfalfa also were characterized. MATERIALS AND METHODS

" A p o l l o " alfalfa from a common 4-yr-old stand was cut on May 20, 1981, at late bud (early cut, EC) and on June 8, 1981, at 50% bloom (late cut, LC). All alfalfa was sprayed aerially for alfalfa weevil on May 8, 1981. Samples were cut by hand at harvest and separated to determine percentages of leaf:stem by methods of Fick and Holthausen (9). Alfalfa was allowed to field-cure to 45% DM without being disturbed and then field-chopped to .95 cm theoretical length with the short cut setting without recutter screen. 7 Alfalfa haylage (EC and LC) was mixed with three concentrations of fresh dairy waste fiber at 0 (control, C), 20 (low, L), or 40% (high, H) DM and stored in 100-ton capacity plastic silo bags. s Dairy waste fiber was obtained from a perforated roller liquid/solid separator that processed manure from 140 lactating Holstein cows housed on concrete lots. Cows received

7New Idea Uni-System, Davenport, IA. 8Eberhart Silo Press, Sioux City, IA. 9Total Recycle Unit, Babson Bros. Co., Oak Park, IL.

1095

approximately 16 kg of DM per head daily consisting of 27% alfalfa haylage, 30% corn silage, and 43% concentrate (17% crude protein) made up of shelled corn and soybean meal. Manure was scraped daily and pumped to a storage pit. After 1 wk of collection, a commercial liquid-solid separator with perforated rollers9 processed the slurry into a solid fraction and a liquid effluent. Processing of the manure started the day before ensiling and continued until the ensiting process was completed. Heating in the stack was prevented by mixing the DWF every 3 to 4 h prior to ensiling. Samples o f all diets were taken during the bag-filling process. Thirty-five Holstein heifers (initial weight, 339 kg) were assigned to a 2 × 3 factoral experiment and fed one of six diets (early cut control, no waste-ECC; early cut, low waste-ECL; early cut, high waste-ECH: late cut control, no waste-LCC; late cut, low waste-LCL; late cut, high waste-LCH) in a 19-day digestion trial. Feed was removed from the silo bags daily, and an attempt was made to discard s p o r e d material prior to feeding. Heifers consumed the diets ad libitum and had access to a mineral-salt block 3 h each day. Adjustment lasted 16 d a y s - a n d collection 3 days. Grab samples of feces were collected once daily during the final 3 days of the trial. Rumen fluid samples were taken via stomach tube at 18 h post feeding on day 18. Rumen fluid pH was taken immediately, and rumen fluid was acidified to pH 2 with 6 N HC1, centrifuged, and stored at - 2 0 ° C pending volatile fatty acid (VFA) analyses. Feed, feces, and unensiled samples of total herbage, leaves, stems, and DWF were cornposited, oven-dried at 55 C for 3 days, ground through a Wiley mill (2 mm screen), and analyzed for neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) by methods of Goering and Van Soest (11). Acid detergent fiber N (ADFN) was determined on all feed samples to measure protein damage from Maillard reaction (21). Cellulose concentration was determined by subtraction of ash and ADL from ADF. Nitrogen was measured by the Kjeldahl m e t h o d (3). The acid insoluble ash (AIA) marker method was used to determine nutrient digestibility coefficients (20). Total and individual volatile fatty acid concentrations were measured with a Journal of Dairy Science Vol. 66, No. 5, 1983

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NEWMAN, JR., ET AL.

TABLE 1. Least square mean composition of fresh dairy waste fiber (DWF) and unensiled samples of alfalfa cut at two maturities of spring growth and separated into total herbage, leaf, and stem fractions. Fiber fraction Item

ECT

ECLEAF

ECSTEM

LCT

LCLEAF

LCSTEM

43.5

56.5

DWF

(% DM) Leaf:stem fraction Neutral detergent fiber Acid detergent fiber Acid detergent lignin Nitrogen Crude protein Ash Calcium Potassium Magnesium Sodium

48.0

52.0

42.3

28.9

56.3

56.1

40.1

71.1

77.7

35.8

19.3

45.8

44.8

21.2

53.2

52.7

7.5 3.5 22.0 12.0 3.50 2.34 .53 .26

4.2 4.9 30.8 12.2 4.22 2.47 .98 .33

11.3 2.4 14.7 8.8 1.68 2.55 .37 .23

10.7 2.9 18.2 10.3 2.57

5.9 4.5 28.2 11.2 4.20 2.40 .55 .35

13.0 1.8 11.1 3.1 1.50 2.01 .60 .20

12.9 1.2 7.6 13.4

2.24

.62 .28

EC = early cut, LC = late cut, T = total herbage, LEAF = leaf fraction, STEM = stem fraction. DM = dry matter.

Vista 44 gas liquid c h r o m a t o g r a p h l ° according to procedures of Erwin et al. (7). Samples of unensiled feeds were analyzed for calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) by a Perkin-Elmer Model 2380 a t o m i c absorption s p e c t r o p h o t o m e t e r 11 with the wet digestion m e t h o d for plant tissue (2). Data were analyzed by analysis of variance with least significant difference used for comparing t r e a t m e n t means (12). Initial analysis of data was with the means p r o c e d u r e of the Statistical Analysis System (4). RESULTS A N D DISCUSSION

A delay of cutting alfalfa f r o m late bud stage (May 20-early cut, EC) until the 50% b l o o m stage (June 8-1ate cut, LC) increased N D F , A D F , and A D L and decreased total N (Table 1). Ferebee et al. (8) f o u n d a similar pattern when evaluating spring growth o f alfalfa in the vegetative through ripe seed stages. Following separation of leaf and stem fractions, percentages of leaf:stem were 4 8 : 5 2 for EC and 4 3 . 5 : 5 6 . 5 for LC alfalfa. Decreases of the percentage of leaf fraction with m a t u r i t y

a OVarian , Walnut Creek, CA. 11Perkin-Elmer, St. Louis, MO. Journal of Dairy Science Vol. 66, No. 5, 1983

were reported (9). Concentrations of N D F , A D F , and A D L were higher in the LC leaf and stem fractions c o m p a r e d with EC leaf and stem fractions. Higher fiber was also in the stem fractions of each m a t u r i t y (Table 1). Nitrogen was highest in the EC leaves and stems and decreased in LC leaves and stems. Higher N in the leaf fraction emphasizes the need for m a n a g e m e n t practices, which m a x i m i z e leaf retention during harvesting (15). Calcium also was c o n c e n t r a t e d in the leaves (Table 1). L o w e r Ca c o n c e n t r a t i o n in LC stems as c o m p a r e d to EC stems as well as a higher percentage of LC stems decreased c o n c e n t r a t i o n of Ca in total LC herbage. There were no marked differences of K, Mg, or Na concentrations a m o n g maturities or leaf-stem fractions (Table 1). Chemical analysis of fresh DWF is also in Table 1. A f t e r separation of solids f r o m liquids, DWF retained 72% moisture. Ash and A D L c o n c e n t r a t i o n s were relatively high, whereas N c o n t e n t was low. Dairy waste fiber contained 77.7% NDF, making it comparable in fiber c o n t e n t to low quality roughages such as mature grass hays, oat straw, or LC stems. C o m p o s i t i o n of the DWF was similar to that of the DWF used by o t h e r researchers (13, 17, 19). The buffering capacity (Bc) of plants, or

ALFALFA HAYLAGE-DAIRY WASTE FIBER MIXTURES their ability to resist pH change, is an i m p o r t a n t factor to consider in ensiling (16). Alfalfa has a high Bc (50 to 60 m e q alkali/100 g DM), which increases three to f o u r times during ensiling. The significance of feeding highly buffered silage to an animal is u n k n o w n , although it has been postulated that Bc m a y affect intake and quality of silages after exposure to air (16). Alfalfa also contains l o w water soluble carbohydrates (WSC) essential for proper f e r m e n t a t i o n . In silos i m p r o p e r l y or inadequately consolidated and sealed, high t e m p e r a t u r e will result in significant carbohydrate losses. These losses m a y be so great that insufficient fermentable WSC remain to permit adequate f o r m a t i o n of lactic acid to lower pH below the critical pH. In m o s t farm silos, considerable aerobic f e r m e n t a t i o n resulting f r o m b o t h plant and microbial e n z y m e activity takes place on the surface and sides of the silage. E x t e n t of f o r m a t i o n of this waste material is related to the efficiency with which the silo is sealed (16). F e r m e n t a t i o n characteristics of ensiled feedstuffs were ranged f r o m 5.0 (ECL) to 8.1 (LCH) (Table 2). Acid detergent insoluble N c o n t e n t of diets ranged f r o m .74 to .87%. This represented a ratio of A D I N / t o t a l N of .24 to .36. Goering (10) considered feedstuffs containing above .3%

1097

A D I N as possessing detrimental heat damage, with a normal range for u n d a m a g e d feedstuffs being .05 to .2% ADIN. Maillard-polymer f o r m a t i o n results in reduced DM and N digestibilities. Acid d e t e r g e n t insoluble N c o n t e n t was highest in both control diets (ECC and LCC) c o m p a r e d to diets containing waste. The greatest spoilage, as detected by visual observation, occurred in the ECC and LCC silages with a p p r o x i m a t e l y 40% of these diets being spoiled. Silages containing DWF had little visible spoilage and maintained a fresher, sweeter o d o r than did control silages. C o m p o s i t i o n o f ensiled feedstuffs is in Table 2. Concentrations of NDF, A D F , and A D L increased, whereas N c o n c e n t r a t i o n decreased as DWF increased. Differences (P<.05) b e t w e e n ECC and LCC o c c u r r e d for N D F , A D F , and N concentrations. No differences of N D F , A D F , ADL, or N c o n c e n t r a t i o n occurred b e t w e e n ECC and ECL. Increasing fiber c o n c e n t r a t i o n s and decreasing N c o n t e n t agree with (13, 19). Daily intakes of various dietary constituents by heifers are in Table 3. Daily feed intakes (kg DM/day) by heifers fed ECC, ECL, or LCC were similar. When daily feed intake was expressed as a percentage of body weight, intake of ECC by heifers was lower (P<.05) than that of ECL or LCC. Buchman and H e m k e n

TABLE 2. Least square mean composition after ensiling of two maturities of alfalfa with three percents of dairy waste fiber (DWF). Diet a Item

ECC

ECL

ECH

LCC

LCL

LCH

Dry matter (DM), % pH

42.1 5.1

42.6 5.0

36.8 6.3

45.4 5.1

38.3 6.3

36.5 8.1

SE

(% DM) Neutral detergent fiber Acid detergent fiber Acid detergent lignin Nitrogen Acid detergent insoluble N (ADIN) ADIN/Total N

45.0 b

48.1 b

59.5 c

54.2 d

61.4 c

67.1 e

.74

37.4 b

41.0 b

48.5 c

45.1 d

52.3 d

54.Od

.79

8.5 b 3.5 b

9.8 b 3.1 b

11.5 c 2.5 c

10.7 b 2.9 d

12.9 d 2.5 c

14.4 d 2.2 c

.25 .07

.87 .25

.74 .24

.74 .30

.87 .30

.75 .30

.79 .36

aEC = early cut, LC = late cut, C = 0% DWF, L = 20% DWF, H = 40% DWF. bcd . . . . . . ' ' means wttlam a row w~tn unlike superscripts differ (P<.05). Journal of Dairy Science Vol. 66, No. 5, 1983

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NEWMAN, JR., ET AL.

(6) a n d S p a h r et al. (18) r e p o r t e d t h a t i n t a k e o f early cut, i m m a t u r e alfalfa was h i g h e r t h a n i n t a k e of late cut, m o r e m a t u r e alfalfa. O u r DM i n t a k e results m a y be d u e to ensiling p r o b l e m s a n d n o t to v a r i a t i o n s o f q u a n t i t y o f cell wall c o n s t i t u e n t s . However, J o h n s o n et al. (14) p r o p o s e d t h a t f e e d i n g diets c o n t a i n i n g s c r e e n e d m a n u r e solids c o n t a i n i n g high cell wall cons t i t u e n t s a l t e r e d tile ability o f dairy steers a n d heifers to pass n o n d i g e s t e d f i b e r t h r o u g h t h e i r digestive tract, t h u s l i m i t i n g v o l u n t a r y i n t a k e of t h e t o t a l diet. Feed i n t a k e ( p e r c e n t a g e o f b o d y w e i g h t ) of late c u t alfalfa m i x t u r e s also d e c l i n e d as D W F increased. Staples et al. (19) i n d i c a t e d t h a t decreased i n t a k e m a y be a result o f p a l a t a b i l i t y p r o b l e m s at h i g h e r DWF. Daily dietary i n t a k e s o f NDF, A D F , a n d A D L were h i g h e r ( P < . 0 5 ) for LCC a n d LCL diets c o m p a r e d to ECC. L o w e r n u t r i e n t i n t a k e s b y heifers fed LCH were

due to l o w e r daily DM i n t a k e s a l t h o u g h f i b e r c o n c e n t r a t i o n s in t h e feed were higher. Daily i n t a k e s o f N D F in ECC a n d E C L diets were similar as a result o f increased f i b e r in t h e feed. N i t r o g e n i n t a k e s decreased as D W F in t h e m i x t u r e increased a n d as m a t u r i t y c h a n g e d . T h e DWF in t h e diets decreased ( P < . 0 5 ) DM digestibility (Table 3). M o s t d r a m a t i c a l l y a f f e c t e d was EC alfalfa diets c o n t a i n i n g waste. A p p a r e n t DM digestibility was h i g h e s t for ECC a n d d e c l i n e d 18% with a d d i t i o n o f D W F in t h e ECL diet. Dairy waste f i b e r in t h e LCL diet r e s u l t e d in a smaller r e d u c t i o n of DM digestibility (3.5%) c o m p a r e d t o LCC. A n d e r s o n et al. (1) f o u n d t h a t DM digestibility of alfalfa decreased a p p r o x i m a t e l y .28 p e r c e n t a g e u n i t s for each day of delay in c u t t i n g . U p o n exa m i n a t i o n o f DM digestibility data, we h y p o thesized that maximum growth and performance o f dairy heifers likely w o u l d be achieved if

TABLE 3. Least square mean daily feed intakes and digestibilities of dietary fractions of two maturities of alfalfa haylage ensiled with three percents of dairy waste fiber (DWF). Diet a Item Intake (% body weight)

ECC

2.23 b

ECL

2.50 c

ECH

LCC

1.94 d

2.51 c

LCL

LCH

SE

2.01 b

1.48 d

.07

(kg/day) Intake (ad libitum) Dry matter Neutral detergent fiber Acid detergent fiber Acid detergent lignin Nitrogen Digestibility Dry matter

8.1 b

7.8 b

6.2 c

7.4 b

6.8 c

4.0 d

.24

3.6 b

3.7 b

3.6 b

4.0 c

4.2 c

3.2 d

.11

3.0 b

3.2 c

3.0 b

3.3 c

3.6 c

2.7 b

.08

.7 b .28 b 69.3 b

.8 c .25 b 51.2 c

.7 b .15 c 38.8 d

.8 c .24 b 50.1 c

.9 c .18 d

.7 b .11 c

.02 .01

46.6 cd

42.2 cd

4.6

(% DM) Neutral detergent fiber Acid detergent fiber Acid detergent lignin Cellulose Nitrogen

58.7 b

38.7 c

35.4 d

43.2 e

38.2 cd

38.3 cd

.7

59.9 b

43.7 c

37.3 d

42.8 c

43.0 c

39.6 e

.7

30.8 b 68.5 b 77.9 b

12.4 c 53.6 c 66.7 c

12.3 c 45.1 d 56.7 d

3.4 d 54.8 c 56.6 d

17.4 c 52.1 ce 59.1 d

14.2 c 48.8 e 52.6 e

1.9 1.2 1.3

aEC = early cut, LC = late cut, C = 0% DWF, L = 20% DWF, H = 40% DWF. b'c'd'eMeans within a row with unlike superscripts differ (P<.05). Journal of Dairy Science Vol. 66, No. 5, 1983

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ALFALFA HAYLAGE-DAIRY WASTE FIBER MIXTURES

TABLE 4. Least square mean volatile fatty acid (VFA) concentrations in rumen fluid of heifers fed diets of two maturities of alfalfa and three percents of dairy waste fiber (DWF). Diet a Item

ECC

ECL

ECH

LCC

LCL

LCH

SE

Total VFA (mM)

91.35 b

85.20 b

97.40 b

74.35 c

67.26 d

67.96 d

2.21

Acetate (A) Propionate (P) Butyrate Isovalerate Valerate A:P ratio

66.6 b 20.7b 9.6b 1.6 b 1.5 b 3-3b

71.8 c 18.5 c 7.1c 1.6 b 1.2 b 3.9 c

75.5 d 15.5 d 5.8 d 1.0 c 1.2 b 5.0 d

74.3 d 16,8 d 6.2 d 1.5 b .9 d 4.5 d

75.3 d 16.9 d 5.3d 1.5 b .9 d 4.5 d

.67 .43 .26 .05 .06 .14

(mol/100 mol) 69.6 b 20.0 b 7.9 b 1.4 d 1.3c 3.5 b

aEC = early cut, LC = late cut, C = 0% DWF, L = 20% DWF, H = 40% DWF. b'C'dMeans within a row with unlike superscripts differ (P<.05).

animals were fed the ECC diets; however, m a i n t e n a n c e of heifers could be achieved by feeding ECL, LCC, or LCL diets. The similar DM digestibilities of ECL, LCC, and LCL by heifers indicates that the addition of 20% DWF to EC alfalfa results in a p r o d u c t similar to LC alfalfa or LC alfalfa containing 20% waste. Fiber digestibility data c o r r o b o r a t e these results. Other reports (13, 19) indicate that dietary DWE depresses digestibilities of DM, N D F , A D F , ADL, and cellulose of both corn silage and alfalfa haylage diets. Nitrogen digestibilities followed a similar pattern to fiber (Table 3). Nitrogen digestibility of EC alfalfa was decreased by 11% with addition of 20% (DM) DWF. Late cut control alfalfa and LCL had similar N digestibilities. Nitrogen digestibility of LCH was lower (P<.05) than that of LCC or LCL. A p p a r e n t N digestibility was 70.4% in vegetative stage alfalfa (5) and 63% in alfalfa similar in ceil wall c o n t e n t to ECC. Additions of DWF depressed apparent N digestibilities (19). Ruminal volatile f a t t y acid data are in Table 4. Heifers fed EC alfalfa either with or w i t h o u t waste had similar total ruminal c o n c e n t r a t i o n s (mM) of V F A . Animals fed LC material had lower total concentrations of ruminal V F A with those fed waste having less (P<.05) total V F A c o m p a r e d to those fed the control (LCC). A d d i t i o n of DWF to the diets resulted in higher (P<.05) ruminal c o n c e n t r a t i o n s ( m o l l 1 0 0 mol)

of acetate and lower (P<.05) c o n c e n t r a t i o n s o f both p r o p i o n a t e and butyrate. Isovalerate c o n c e n t r a t i o n s ranged f r o m 1.0 to 1.6 m o l / 1 0 0 mol while valerate c o n c e n t r a t i o n s ranged f r o m .9 to 1.5 m o l / 1 0 0 mol. The c o m b i n e d effects of DM intake and fiber in the diet increased the ratio of a c e t a t e : p r o p i o n a t e as DWF increased (Table 4). Higher acetate and lower p r o p i o n a t e concentrations are characteristic o f diets having high fiber concentrations (21). CONCLUSIONS

Additions of DWF to EC alfalfa reduced both DM intake and digestibility by heifers. Large reductions of DM and fiber digestion occurred when 20% (DM) DWF was added to EC alfalfa. Changes of digestibility with DWF additions to LC alfalfa were m i n o r in comparison to that for EC alfalfa. However, significant reductions of DM intake occurred when heifers were fed the LCH diet. M a x i m u m growth and p e r f o r m a n c e of dairy heifers likely w o u l d be o b t a i n e d if animals c o n s u m e d ECC diets. Heifers fed ECL and LCC diets had similar DM and fiber digestibilities. Diets of this t y p e could be useful in m a i n t e n a n c e programs. REFERENCES

1 Anderson, M. J., G. F. Fries, D. V. Kopland, and D. R. Waldo. 1973. Effect of cutting date on digestibility and intake of irrigated first-crop alfalfa hay. Agron. J. 65:357. Journal of Dairy Science Vol. 66, No. 5, 1983

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2 A n o n y m o u s . 1982. Analytical m e t h o d s for atomic absorption s p e c t r o p h o t o m e t r y . Procedure AY--5. Perkin-Elmer Corp., Norwalk, CT. 3 Association of Official Analytical Chemists. 1970. Official m e t h o d s of analysis. 11th ed. Assoc. Offic. Anal. Chem., Washington, DC. 4 Barr, A. J., J. H. Goodnight, J. P. Sail, and J. T. Helwig. 1979. A user's guide to SAS '79. SAS Inst. Inc., Raleigh NC. 5 Baumgardt, B. R., W. J. Byer, H. F. J u m a h , and C. R. Krueger. 1964. Digestion in the steer, goat, and artificial r u m e n as measures of forage nutritive value. J. Dairy Sci. 47:160. 6 Buchman, D. T., and R. W. Hemken. 1964. Ad libitum intake and digestibility of several alfalfa hays b y cattle and sheep. J. Dairy Sci. 47:160. 7 Erwin, E. W., G. J. Marco, and E. M. Emery. 1961. Volatile fatty acid analysis of blood and r u m e n fluid by gas chromatography. J. Dairy Sci. 4 4 : 1 7 6 8 . 8 Ferebee, D. B., D. O. Erickson, C. N. Haugse, K. L. Larson, and M. L. Buchanan. 1972. Digestibility and chemical composition of b r o m e and alfalfa t h r o u g h o u t the growing season. North Dakota Farm Res. 30:3. 9 Fick, G. W., and R. S. Holthausen. 1975. Significance of parts other than blades and s t e m s in leaf-stem separations of alfalfa herbage. Crop Sci. 15:259. 10 Goering, H. K. 1976. A laboratory assessment of the frequency of overheating in commercial dehydrated alfalfa samples. J. Anita. Sci. 43:869. 11 Goering, H. K., and P. J. Van Soest. 1970. Forage fiber analysis. Dep. Agric., Agric. H a n d b o o k 379, Washington, DC.

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12 Huntsberger, D. V., and P. Billingsley. 1981. Elements of statistical inference. Allyn and Bacon, Inc., Boston, MA. 13 Jaster, E. H., H. R. Newman, Jr., G. C. McCoy, C. R. Staples, L. L. Berger, a n d G. C. Fahey, Jr. 1982. Evaluation of dairy waste fiber as a roughage source for dairy heifers. J. Dairy Sci. 65:1234. 14 Johnson, W. L., F. Rodriquez, E. Oliveira, T. Mercio, and J. C. Wilk. 1982. Refeeding value of screened bovine m a n u r e solids. J. A n i m . Sci. 55:700. 15 Jorgensen, N. A., and W. T. Howard. 1981. The role of forage in midwest dairy enterprises during the n e x t ten years. Alfalfa F o r u m , Madison, WI. 16 McDonald, P., and R. Whittenbury. 1973. The ensilage process. In Chemistry and biochemistry of herbage. Vol. 3. G. W. Butler and R. W. Bailey, ed. Academic Press, Inc., London. 17 Rakes, A. H., D. G. Davenport, and J. C. Wilk. 1977. The singular and combined effects o f screened m a n u r e solid (SMS) and crude fiber in the ration of lactating dairy cows. J. Dairy Sci. 61:140. (Abstr.) 18 Spahr, S. L., E. M. Kesler, J. W. Bratzler, and J. B. Wasko. 1961. Effect of stage of m a t u r i t y at first cutting on quality of forages. J. Dairy Sci. 44:503. 19 Staples, C. R., G. C. Fahey, Jr., R. B. Rindsig, and L. L. Berger. 1981. Evaluation of dairy waste fiber as a roughage source for ruminants. J. Dairy Sci. 64:662. 20 Van Keulen, J., and B. A. Young. 1977. Evaluation of acid-insoluble ash as a natural marker in r u m i n a n t digestibility studies. J. Anim. Sci. 44:282. 21 Van Soest, P. J. 1982. Nutritional ecology of the ruminant. O & B Books, Inc., Corvallis, OR.