玉米青貯的切割長度對泌乳期奶牛的影響

1、Crop Processing and Chop Length of Corn Silage:Effects on Intake, Digestion, and Milk Production by Dairy CowsM. A. Bal, 1R. D. Shaver, 1A. G. Jirovec,K. J. Shinners, 2and J. G. Coors 3University of Wisconsin, Madison 53706ABSTRACTEffects of corn silage crop processing and chop length on intake, dig

2、estion, and milk production were evalu-ated. Corn silage treatments were harvested at one-half milkline stage of maturity (65%whole-plant moisture content and at 0.95-cm theoretical length of cut with-out processing (controlor 0.95-, 1.45-, or 1.90-cm theo-retical length of cut with processing at a

3、1-mm roll clearance. Twenty-four multiparous Holstein cows av-eraging 71d in milk at trial initiation were in a repli-cated 4×4Latin square design with 28-d periods; one square was comprised of ruminally cannulated cows for rumen measurements. Corn silage treatments were fed in total mixed rati

4、ons containing 50%forage (67%corn silage and 33%alfalfa silage and 50%corn and soybean meal based concentrate (drymatter basis. Dry matter intake (25.9vs. 25.3kg/dand milk (46.0vs. 44.8kg/d and fat (1.42vs. 1.35kg/dyields were higher for the processed corn silage treatments compared with the control

5、 corn silage. Within the processed corn silage treatments, there were no chop length effects on intake, milk production, or milk composition. Chewing activity was not different among the four corn silage treatments averaging 12h/d.Total tract digestion of dietary starch was lower for control corn si

6、lage (95.1%compared with ne,medium, and coarse processed corn silage treat-ments, which averaged 99.3%.Total tract digestion of dietary NDF was reduced for ne-processedcorn silage compared with control corn silage and coarse-processed corn silage (28.4%vs. 33.9and 33.7%,respectively. Processing corn

7、 silage improved dry matter intake, starch digestion, and lactation performance. Under the conditions of this study and with theoretical lengths of cut ranging from 0.95to 1.90cm, length of chop effects were minimal in processed corn silage.(Key words:corn silage, processing, particle size, milk pro

8、ductionReceived November 3, 1999. Accepted February 1, 2000.Department of Dairy Science. 2Department of Biological Systems Engineering. 3Department of Agronomy. 2000J Dairy Sci 83:126412731264Abbreviation key:FPR =ne-processedcorn silage, MPR =medium-processed corn silage, CPR =coarse-processed corn

9、 silage, TLC =theoretical length of cut, WPCS =whole-plant corn silage.INTRODUCTIONRecently, interest in the feeding of processed (rolledcorn silage to lactating dairy cows has increased. Cur-rently, crop processors are available on both self-pro-pelled and pull-type harvesters. Research in North Am

10、erica has shown that processing whole-plant corn silage (WPCS improves total-tract starch digestion in dairy cows (4and beef steers (22and milk production by dairy cows (13.Satter et al. (24summarized WPCS processing trials for response in milk production, and found 0.5kg/dhigher milk production for

11、 processed compared with unprocessed WPCS. In two studies (4,22, total-tract starch digestion was increased 5per-centage units for processed compared with unprocessed WPCS diets.There has been little research to evaluate effects of WPCS chop length on lactation performance and diges-tion by dairy co

12、ws. Kuehn et al. (16saw no DMI or milk production difference between long (0.87cm or short (0.32cm theoretical length of cut (TLC unpro-cessed WPCS. Stockdale and Beavis (28evaluated ne,medium, and coarse TLC unprocessed WPCS, and re-ported no differences in milk production or apparent total-tract n

13、utrient digestion. Feeding trials that have evaluated chop length effects in processed WPCS are lacking.The objectives of this experiment were to evaluate the effects of processing WPCS and chop length of processed WPCS on intake, digestion, and milk production by dairy cows.MATERIALS AND METHODSPio

14、neer corn hybrid 3563(PioneerHi-Bred Interna-tional, Des Moines, IA was harvested as WPCS at one-half milkline stage of maturity with an experimental pull-type harvester ttedwith on-board rollers. Corn silage treatments were harvested at 0.95cm TLC with-out processing (control,or 0.95-cm (neprocesse

15、d;PHYSICAL FORM OF CORN SILAGE AND MILK PRODUCTION1265FPR , 1.45-cm (mediumprocessed; MPR , and 1.90-cm (coarseprocessed; CPR TLC with processing at a 1-mm roll clearance. The four WPCS treatments were harvested in 1d, and they were stored in separate 2.7-m diameter silo bags. Alternate loads of eac

16、h WPCS treatment were sampled at the bagger to determine moisture content; preensiling moisture content of WPCS treatments was similar, averaging 66%.Twenty-four multiparous Holstein cows were ran-domly assigned to treatments in a replicated 4×4Latin square design with 28-d periods. Four cows i

17、n one square were ruminally cannulated to allow measure-ment of ruminal pH, VFA, mat consistency, and in situ nutrient disappearance from Dacron bags. The rst 14d of each period were for diet adaptation, and sampling occurred during d 15to 28of each period. Cows aver-aged 71DIM (range:44to 99d at tr

18、ial initiation. All cows were injected with bovine somatotropin (Posilac,Monsanto Company, St. Louis, MO every 14d starting on d 1of the experiment. The corn silage treatments, alfalfa silage, and concentrate mix comprised 34, 16, and 50of diet DM, respectively, and were fed as TMR once daily. Diets

19、 were formulated to contain 17.5%CP (DMbasis and to meet or exceed NRC (21require-ments for minerals and vitamins. Dry matter content of WPCS treatments and alfalfa silage were measured weekly using 60°C forced-air oven for adjustment of as-fed ratios of diet ingredients. The amounts of TMR off

20、ered and refused were recorded daily. Cows were fed ad libitum, and diet refusals were maintained at approximately 10%.The WPCS treatments, alfalfa si-lage, and concentrate mixture were sampled on d 15and 22of each period and each was composited by period for nutrient analysis. Refusal samples were

21、collected on d 26to 28of each period and composited by cow within period. Feed and refusal composites were dried for 48h in a 60°C forced-air oven and ground to pass a 1-mm Wiley mill screen (ArthurH. Thomas, Philadel-phia, PA. Samples were analyzed for DM, OM, and CP (2,ADF (10,NDF using -amyl

22、ase (Sigmano. A3306; Sigma Chemical Co., St. Louis, MO and sodium sul te (30,and lignin (30.Starch was measured on feed and refusal composites as follows. 1 Aliquots (0.1g were weighed into duplicate 35-ml Pyrex glass centrifuge tubes, 20ml of distilled water was added to each tube, and tubes were v

23、ortexed. 2 -Amylase (100µl; Sigma no. A3306; Sigma Chemical Co., St. Louis, MO was added to each tube and tubes were held for 1h in a 93°C water bath (tubeswere vortexed every 15min during this incubation. 3 Tubes were cooled for 15min and vortexed three times within the rst 10min, then pa

24、rticles were allowed to settle to the bottom of the tubes. 4 Supernatant (1ml was transferred to a new 35-ml Pyrex glass centrifuge tube and then 8ml Journal of Dairy Science Vol. 83, No. 6, 2000of 0.1M sodium acetate buffer (pH4.75 and 50µl of amyloglucosidase (Sigmano. A3514; Sigma Chemical C

25、o., St. Louis, MO was added to each tube. 5 Tubes were incubated in a 60°C water bath for 30min (tubeswere swirled every 10min before adding 16ml of dis-tilled water to each tube to bring the volume to 25ml. 6 Glucose oxidase (Sigmano. 510-A; Sigma Chemical Co., St. Louis, MO was assayed with 0

26、.5ml of sample from each sample tube and absorbance was read with a micro-assay plate reader at 450nm. A pure corn starch sample (Sigmano. S-4126; Sigma Chemical Co., St. Louis, MO was included in each run to check starch recovery, and sample values were adjusted for starch recovery in that run. Ave

27、rage pure starch recovery within nine runs was 100.2±2.5%.The WPCS treat-ments were analyzed for pH, lactic acid, and VFA as described by Muck and Dickerson (20.The particle size of WPCS treatments and their corresponding TMR was determined in duplicate using an oscillating screen par-ticle sep

28、arator according to American Society of Ag-ricultural Engineers standard S424(1.Cows were milked twice daily, and production was recorded at each milking. Milk samples taken from a.m. and p.m. milkings on three consecutive days during wk 3(d15, 16, and 17 and 4(d22, 23, and 24 of each period were an

29、alyzed for milk fat, CP, MUN, and lactose by infrared analysis (AgSourceMilk Analysis Labora-tory, Menomonie, WI. Milk composition was calculated as an average of a.m. and p.m. samples using the pro-portion of daily production at that milking as a weighting factor. Body weights were recorded for thr

30、ee consecutive days at the start of trial and on d 26to 28of each period.Twenty-four hour ruminal in situ DM and starch dis-appearance of WPCS treatments were determined in the ruminally cannulated cows on d 27of each period. In situ bags were made of Dacron polyester cloth (25×35cm, 52±5&

31、#181;m pore size. The WPCS treatments were each incubated with triplicate bags per cow and matching incubation WPCS with diet WPCS by cow and period. Twenty-ve grams of DM was weighed into each bag (30mg/cm2, sample size to surface area ratio and incubated without drying or grinding at 2h after the

32、morning feeding (1000h for 24h. To minimize sampling error for these as-fed samples, a large sample size was used, each treatment was incubated in tripli-cate in each cow, and the treatments were remixed between each subsampling. In situ bags were placed in a nylon laundry bag and positioned in the

33、ventral ru-men. Duplicate blank bags were incubated in each laun-dry bag to correct for in ux of DM into the sample bags. In situ bags were washed in a commercial washing machine with cold water for two cycles of 12min each (5.Bags and residue were then dried at 60°C for 48hBAL ET AL.1266to det

34、ermine DM disappearance. Residues were then composited for each WPCS by period and analyzed for starch as described previously to measure starch disap-pearance.Ruminal uid was sampled immediately before the morning feeding (0800h and at 3, 6, 9, and 12h after feeding on d 25of each period. Samples w

35、ere taken from ve different locations in the rumen via the can-nula using a custom made metal lter probe and pH was determined (twinpH meter Model B-213, Spectrum Technologies Inc., Plain eld, IL. Duplicate 10-ml sam-ples of rumen uid were acidi ed with 0.2ml of 50%H 2SO 4and frozen until analysis f

36、or VFA. These samples were prepared for analysis as follows:1 Sample tubes were thawed and centrifuged at 2000×g , 4°C for 15min. 2 Supernatant (1ml was transferred into a microfuge tube, 0.2ml of 25%metaphosphoric acid was added, and the mixture was vortexed before incubating at room temp

37、erature for 30min. 3 Supernatant was trans-ferred into a GLC sample vial for analysis by using GLC (Varian2100, Sunnyvale, CA with GP 10%SP-1200/1%H 3PO 4on 80/100Chromasorb WAW column packing (Supelco,Bellefonte, PA. Separate duplicate 10-ml samples of rumen uid were acidi ed with 0.2ml of 50%trich

38、loroacetic acid solution and frozen until analysis for ammonia concentration. These samples were centrifuged at 1400×g , 4°C for 20min and the supernatant was diluted 1:10with distilled water. Four milliliters of reagent A (50mg of sodium nitroprusside, 8.25g of sodium tungstate, and 11ml

39、of 90%liqui ed phenol per liter and reagent B (25g of disodium phos-phate, 5g of reagent grade sodium hydroxide, and 50ml of 5.25%sodium hypochlorite per liter were added to 100µl of ruminal uid. Tubes were incubated at room temperature for 1h and absorbance was subse-quently read at 625nm as d

40、escribed by Sievert and Shaver (27.Ruminal mat consistency was measured in the rumi-nally cannulated cows 5h after the morning feeding (1300h on d 26of each period. The method described by Welch (31was used for this measurement. Three replicate measurements for each cow by period were taken at 30-mi

41、n intervals. Times spent eating and ru-minating were measured during the last day of each period by recording the chewing action of each cow every 5min for 24h.Total-tract nutrient digestibilities were measured us-ing La as an external marker. Lanthanum solution (12was sprayed onto a wheat middlings

42、 carrier. Each cow received 114g of wheat middlings labeled with 1g of La solution that was mixed in the TMR on d 18through 28of each period to provide 35mg/kgof La in total diet DM. Fecal grab samples were collected daily at 0800, 1400, and 2000h during the last 3d of each period.Journal of Dairy S

43、cience Vol. 83, No. 6, 2000One gram of Yb solution (25was sprayed onto 500g (DMbasis of each WPCS treatment to estimate solids passage rate. The labeled WPCS was fed to each rumi-nally cannulated cow according to its respective diet immediately before the morning feeding (0800h on d 25of each period

44、. Fecal grab samples were collected before dosing and at 12, 18, 24, 36, 48, 60, and 72h after dosing. Samples were dried in a forced-air oven at 60°C for 96h and then ground to pass a 1-mm Wiley mill screen. The fecal samples taken to determine total-tract nutrient digestibilities were composi

45、ted for each cow by period, ground to pass a 1-mm Wiley mill screen, and analyzed for DM, OM, CP, ADF, NDF, and starch as described previously. The fecal concentration of La was determined in duplicate by direct current plasma emission spectroscopy (7after dry-ashing at 500°C for 16h. Total-tra

46、ct nutrient digestibilities were calculated from La and nutrient concentrations in diet (ortsad-justed and feces. Solids passage rate was determined by regressing the natural logarithm of Yb concentration from the declining portion of the fecal excretion curve versus time.Data were analyzed by using

47、 the general linear mod-els procedure of SAS (23for a replicated Latin square design. The model used for the lactation performance data was:Y ijkl =µ+P i +S j +C k (Sj +T l +(SPji +(STjl +e ijklY =dependent variable, µ=population mean, P i =effect of period i, S j =effect of square j,C k (

48、Sj=effect of cow k nested within square j, T l =effect of treatment l,(SPji =interaction of square j and period i,(STjl=interaction of square j and treatment l, ande ijkl=residual error, normally and indepen-dently distributed.All terms were tested using the residual mean square error. Square ×

49、period and square ×treatment terms were not signi cant. Therefore, they were removed from the model and pooled with the residual error. A contrast statement was also included to test the processing effect (controlvs. FPR, MPR, and CPR. Ruminal pH and VFA data were analyzed using PROC MIXED of S

50、AS (18for repeated measures; time was used as a repeated measure with rst-order auto regressive covariance structure. All mean comparisons were by least signi -cant difference method after a signi cant (P <0.05 treatment effect.PHYSICAL FORM OF CORN SILAGE AND MILK PRODUCTION1267RESULTS AND DISCU

51、SSIONSilage and Diet Composition and Particle Size Chemical composition and fermentation characteris-tics of WPCS treatments are presented in Table 1(datanot statistically analyzed. Moisture content of WPCS was at a desirable level for good silage fermentation, digestibility, and lactation performan

52、ce (3;it averaged 65%,with little variation among treatments. Both NDF and ADF concentrations were lower for FPR and MPR silages compared with control and CPR silage (36to 38%vs. 41%NDF and 21to 22%vs. 24%ADF. Starch concentration (27.3%was highest for FPR silage. It is unlikely that this variation

53、in ber and starch concen-trations among treatments was related to harvest prac-tices, because the eld was subdivided into quadrants for harvest with an equal portion of each quadrant har-vested for each treatment, the harvest was completed in one day, and the same height of cutter head was used for

54、the harvest of all treatments. Variation in ber and starch concentrations among treatments was possi-bly due to more uniform sampling of the ne chopped, processed WPCS. Sudweeks et al. (29reported lower ADF and NDF concentrations (3and 7%units, respec-tively for ne (0.62-cmTLC vs. coarse (1.91-cmTLC

55、 chopped WPCS. Lower ber but higher starch concen-trations for processed versus unprocessed WPCS were reported by Rojas-Bourrillon et al. (22.Lactate concen-tration and pH were indicative of a desirable silage fermentation (19.Lactate and acetate concentrations were higher for FPR silage (5.05and 1.

56、29%of DM versus an average of 4.69and 1.11%of DM, respec-tively, for control, MPR, and CPR silage. This could be due to greater packing density and carbohydrate availability for the processed (22,ne-chopped (28WPCS. The high propionate concentration (0.4to 0.5%of DM was partially related to the appl

57、ication of a Table 1. Chemical composition and fermentation characteristics of whole-plant corn silage treatments. 1Item0.420.500.390.521Control corn silage was unprocessed and had a 0.95-cm theoretical length of cut (TLC;FPR =ne processed corn silage (0.95-cmTLC with 1-mm roll clearance, MPR =mediu

58、m processed corn silage (1.45-cm TLC with 1-mm roll clearance, and CPR =coarse processed corn silage (1.90-cmTLC with 1-mm roll clearance.Journal of Dairy Science Vol. 83, No. 6, 2000buffered propionic acid preservative (Ultra-Curb,Kemin Industries, Des Moines, IA to the silo face of each WPCS treat

59、ment during feed-out.The ingredient and nutrient composition of experi-mental diets is presented in Table 2(datanot statisti-cally analyzed. Diet nutrient concentrations are pre-sented on an orts-adjusted basis. Dietary CP concentra-tion was 0.6%units lower than as formulated because of lower than anticipated CP content of the soybean meal. Diet NDF concentration for control (24.3%and CPR (24.6%was at the minimum NRC (21allowance. This was a function of the relatively low WPCS and alfalfa silage NDF concentrations and our