Effect of the stage of maturity on the nutritive value of whole crop wheat silage

Livestock Production Science 55 (1998) 21–32

Effect of the stage of maturity on the nutritive value of whole crop wheat silage G.M. Crovetto*, G. Galassi, L. Rapetti, A. Sandrucci, A. Tamburini Istituto di Zootecnia Generale, Facolta` di Agraria, Via Celoria 2, 20133 Milan, Italy Received 23 May 1997; accepted 3 February 1998

Abstract An in vivo digestibility and calorimetric experiment was performed on eight adult wethers to determine the digestibility and net energy content of wheat silages obtained from whole plants cut at different stages of maturity. Wheat (Triticum aestivum L., var. Eridano) was harvested at the boot (B), midbloom (MB), milk (M) and dough (D) stages of maturity. The wethers were fed ad libitum in a 4 3 4 latin square digestibility trial. Each collection period lasted eight days with 3 3 24 h-cycles of respiration trials (indirect calorimetry in respiration chambers). In vitro organic matter digestibility (IVOMD) was determined on dried samples of whole wheat cut from the same field at 10 different stages between boot and dough. Silage quality parameters were optimum for all stages. DM, OM and energy intake were significantly higher in the first and last stages of maturity (B and D) than in the medium stages (MB and M). DM, OM and energy digestibility decreased significantly from B to M stage but did not change between the last two stages. In contrast, CF, NDF and ADF digestibility decreased significantly with maturity. IVOMD had a quadratic trend of variation as a function of the stage of maturity, similar to the in vivo data, with the lower value at the M stage. Metabolizability (q 5 ME / GE) followed the same trend of energy digestibility. NE l decreased with increasing stage of plant growth but the difference was significant only between the first stage and the last three stages. The nutritive values of the whole-crop wheat silages was very high for the B stage and decreased with successive stages of maturity (7.74, 6.41, 5.69 and 5.39 MJ NE l / kg DM at the B, MB, M and D stages). In contrast, DM yield was minimum at the B stage (3.3 t / ha) and increased with increasing maturity up to 9.6 t / ha at the D stage. As a consequence, a satisfactory compromise between yield and nutritive value would involve harvesting whole-crop wheat just before the milk stage.  1998 Elsevier Science B.V. Keywords: Wheat silage; Energy metabolism; Digestibility; Plant maturity

1. Introduction In recent years the need to reduce feed costs has led many farmers in Northern Italy to apply a double *Corresponding author. Tel.: 139 270600159; fax: 139 270638083; e-mail: [email protected]

cropping system with maize as the summer crop and Italian ryegrass (Lolium Multiflorum Lam.) or a cereal grain (barley, triticale, wheat, oat, rye) as the winter crop for ensiling before sowing the maize. Wheat (Triticum aestivum L.) has a good potential due to its very high dry matter (DM) yield, often higher than Italian ryegrass, and its high DM content

0301-6226 / 98 / $19.00  1998 Elsevier Science B.V. All rights reserved. PII: S0301-6226( 98 )00125-0

22

G.M. Crovetto et al. / Livestock Production Science 55 (1998) 21 – 32

(28–30%) already at the milk stage of grain maturity. This, combined with a good content of water soluble sugars, allows ensiling without wilting with clear advantages in terms of less risk of soil and Clostridia contamination, smaller nutritive losses and simpler harvesting procedures. The data obtained in a previous digestibility and calorimetric experiment (Succi et al., 1993) on whole crop wheat silage (WCWS) at the dough stage showed a high net energy content for lactation (NE l 5 5.76 MJ / kg DM). Moreover, an in situ degradability trial showed that wheat silage, harvested at the milk-dough stage, had a higher rumen degradability of DM and NDF than other winter cereals, although it was lower than Italian ryegrass (Tamburini et al., 1995). The NDF content of wheat remains fairly constant during maturation (Arieli and Adin, 1994) due to the increasing starch deposits. This suggests that the voluntary intake and digestibility of wheat may not change significantly during maturation, allowing a long interval for cutting without adverse effects on the quality and the nutritive value of the forage. Unfortunately, the results of studies concerning the influence of the stage of plant growth on digestibility and nutritive value of WCWS are scarce and not consistent. Some authors have reported no relationships between DM digestibility and maturity (Arieli and Adin, 1994), while others have found DM digestibility to decrease with increasing growth stage (McCullough and Sisk, 1967; Cannel and Jobson, 1968; Adogla-Bessa and Owen, 1995b). Moreover few data are available in the literature on the energy value of WCWS and its variation with maturity (Adesogan, 1996). The aim of the present work was to determine the effect of plant maturity on the nutritive value of WCWS.

2. Materials and methods The forage tested in the trial was produced on a farm in the province of Lodi, 30 km south of Milan. Wheat (Triticum aestivum L., Eridano var.) was sown on 15th October 1994 and harvested at four stages of maturity: boot (B; 28th April 1995; 21.1% DM), midbloom (MB; 5th May 1995; 24.0% DM),

milk (M; 23rd May 1995; 31.1% DM) and dough stages (D; 5th June 1995; 37.9% DM). All wholeplant forages were direct cut, in four adjacent field plots measuring 140 3 5 m, chopped to a length of 2–3 cm, weighed, sampled for DM analysis and ensiled in 120-l silos with the addition of a commercial bacterial inoculant (Lactobacillus plantarum; 10 9 cells / kg forage). Eight adult Bergamasca wethers, with an average bodyweight (BW) of 89.8 kg, were paired and fed the wheat silages ad libitum in a 4 3 4 latin square digestibility trial. The wethers were allocated to individual metabolic cages to determine apparent digestibility; each digestibility trial consisted of a preliminary period of 15 days followed by a collection period of eight days. The animals were fed twice daily; before feeding, orts were collected and weighed. Samples of the silages fed and the orts were collected daily for the determination of DM content in a forced ventilation oven at 608C for 72 h. Pooled samples of each item, for each collection period and each animal were used for analysis. Faeces and urine were collected daily and sampled. Two sub-samples of urine were obtained by the addition of different preservatives: for nitrogen and energy determinations, the first sub-sample was acidified with 10% – on a weight basis – of a solution containing 10% (v / v) H 2 SO 4 ; for the determination of chemically bound CO 2 (required to calculate total CO 2 production and C balance), formalin (20 ml / l urine) was added to the other sub-sample. Chemical analyses of feed, orts, faeces and urine were performed in accordance with the Italian Scientific Association for Animal Production recommendations (ASPA Commissione Valutazione Degli Alimenti, 1980). Samples of silages were analysed for organic acids and ammonia N in order to correct the DM content according to Dulphy and Demarquilly (1981). Gross energy (GE) of all samples was determined in an adiabatic calorimeter (JKA 4000): urine samples were placed in polyethylene bags, freeze dried and then burnt in the calorimeter (Nijkamp, 1969, 1971). The C content of all samples was determined immediately after the calorimetric determination, by passing the gas stream from the bomb calorimeter through a suitable set of absorption tubes to bind CO 2 (Nijkamp, 1969, 1971). Measurements of the respiratory exchanges were

G.M. Crovetto et al. / Livestock Production Science 55 (1998) 21 – 32

recorded by using two open-circuit respiration chambers as described by Crovetto (1984). During the collection period, each of the four pairs of wethers were confined in the respiration chamber for four days in order to obtain three 24-h cycles of respiratory exchanges. Total heat production (HP) was determined by indirect calorimetry using an equation from Brouwer (1958): HP (kJ / d) 5 16.18 O 2 1 5.02 CO 2 2 5.99 N 2 2.17 CH 4 , where gas volumes (l / d) are expressed at standard conditions and N (g / d) is the urinary nitrogen. Net energy for maintenance (NE m ) was calculated as a function of metabolizable energy (ME) and metabolizability (ME / GE) according to Van Es (1978): NE m 5 ME(0.554 1 0.287ME / GE). Net energy for lactation was computed according to Van Es (1978): NE l 5 ME(0.4632 1 0.24ME / GE). NE l was also expressed as UFL (feed energy unit corresponding to 7.1128 MJ of NE l ). The UFL concentrations were also calculated with INRA equations (INRA, 1978, 1988). Protein and fat depositions were computed according to Brouwer (1965) as follows: protein deposition 5 retained N6.25; fat deposition 5 (retained C 2 retained N3.25)1.304. Samples of whole crop wheat forages from the same field were harvested at ten different stages of maturity and dried in a forced draught oven at 608C for 72 h; these were used for the determination of the IVOMD according to Tilley and Terry (1963). Data were analysed by ANOVA using a GLM procedure (SAS / STAT, 1994). The following model was applied to the data obtained from each individual wether: Yijk(t ) 5 m 1 Si 1 A ij 1 Pk 1 T (t ) 1 e ijk

(1)

where: Yijk ( t) 5dependent variable; m5general mean; Si 5square effect (i51, 2); A ij 5animal effect within square ( j51, 4); Pk 5period effect (k51, 4); T (t ) 5 stage of wheat maturity effect (t51, 4); e ijk 5 residual error. Data obtained from each pair of animals (methane, HP, ME, NE and retained energy) were analysed with the following model: Yij(t ) 5 m 1 Bi 1 Pj 1 T (t ) 1 e ij

(2)

where: Yij ( t) 5dependent variable; m5general mean; Bi 5pair of animals effect (i51, 4); Pj 5period effect

23

( j51, 4); T (t ) 5stage of wheat maturity effect (t51, 4); e ij 5residual error.

3. Results and discussion

3.1. Chemical composition and fermentation parameters Table 1 shows the chemical composition of the WCWS. DM content rose from 19.7% for the boot to 36.0% for the D stage while CP content decreased with increasing stage of maturity (from 12.7 to 7.9% DM). Crude fibre (CF), NDF and ADF contents were fairly constant in the first three stages with a reduction in the D stage, while lignin progressively increased from the B to the D stage. This general lack of variation of fibre concentrations in whole crop wheat from flowering to milk stage has already been reported by other authors (Weinberg et al., 1991; Arieli and Adin, 1994). Starch was low in the first three stages but increased noticeably in the last one. Ammonia N (as a percentage of total N) was higher in the B and D

Table 1 Chemical composition of the wheat silages used in the trial Stage of maturity

B

MB

M

D

DM (% as fed) $ OM (% DM) CP (% DM) EE (% DM) CF (% DM) NDF (% DM) ADF (% DM) Lignin (% DM) Soluble sugar (% DM) Starch (% DM) NSC (% DM) Carbon (% DM) GE (MJ / kg DM) N-NH 3 (% total N) Lactic acid (% DM) Acetic acid (% DM) Propionic acid (% DM) Butyric acid (% DM) pH

19.7 93.1 12.7 5.4 29.6 57.5 34.9 3.8 1.2 2.3 17.5 47.2 20.56 7.1 4.1 1.3 0.09 0.02 3.60

22.4 94.4 9.8 4.5 31.1 59.4 34.6 4.7 1.6 2.6 20.7 46.1 19.73 4.8 4.3 0.8 0.14 0 3.55

29.0 93.8 8.3 3.1 28.9 59.4 35.0 4.6 1.3 2.7 23.0 45.9 19.72 6.4 4.0 1.2 0.18 0 3.60

36.0 94.4 7.9 2.7 26.7 48.7 31.0 6.2 1.1 18.8 35.1 44.2 18.82 8.9 3.5 1.1 0.07 0 3.80

B5Boot stage; MB5midbloom stage; M5milk stage; D5dough stage. $ DM content was corrected according to Dulphy and Demarquilly (1981).

G.M. Crovetto et al. / Livestock Production Science 55 (1998) 21 – 32

24

silages than in the others. Lactic acid content was always high while other organic acids were low for all silages and there were no notable differences between the stages of maturity. Ether extract (EE), carbon and GE decreased with maturity stage. GE contents were very high for all the stages. In particular, the last stage had a higher GE content in comparison with the value reported by the INRA (1988) for a similar maturity stage, probably due to the lower ash content; the value obtained in this study agrees with that of a trial performed previously on a WCWS of the same stage of maturity (Succi et al., 1993). Adesogan (1996), working with WCWS cut at 37.6% DM and a stage of maturity quite similar to our D stage, obtained a GE content of 19.6 MJ / kg DM, which is higher than the value obtained in the present trial.

3.2. Intake and in vivo digestibility Daily DM and organic matter (OM) intakes were 49.4, 37.9, 40.7, 49.7 (S.E.M.52.80) and 45.4, 35.3, 38.0, 46.4 (S.E.M.52.60) g / kg BW 0.75 for B, MB, M and D stages, respectively. The values were significantly higher (P,0.01) in the first and last stages (B and D) than the intermediate stages (MB and M). This trend agrees with results for DM intake obtained by Bolsen and Berger (1976) and by Bolsen et al. (1976) in some trials with wether lambs and was partially consistent with the observations of Mannerkorpi and Brandt (1993), although their experiment was performed on silages harvested at later stages of growth (from middle milk stage to yellow ripeness). In contrast, McCullough and Sisk

(1967), in a feeding trial with growing heifers, reported a decrease of DM intake with maturity. DM intake in all four stages was low in comparison with our previous study (Succi et al., 1993). Energy and nitrogen intakes followed the same trend as OM intake. DM, OM, carbon and faecal energy losses progressively increased, often significantly, with stage of plant maturity. Faecal losses of nitrogen and urinary losses of nitrogen, carbon and energy decreased from the boot to the milk stage and then increased again. Faecal losses of NDF and ADF increased significantly with maturity. Apparent digestibility (Table 2) of all parameters decreased with stage of wheat maturity: the B and MB stages had very high digestibility coefficients which were significantly different from the M and D stages. In contrast, no significant differences were revealed between the digestibilities of the M and the D stage silages, except for CF, NDF and ADF. Furthermore, the digestibility of the fibre fractions showed a strong reduction mainly between the M and the D stage. Digestibility coefficients for energy varied from 74.7 for the B stage to 60.2 for the D stage, values which were intermediate between the DM and OM digestibility values. The relative constancy of DM, OM and energy digestibility values in the last two stages of maturation can be explained by the compensatory effects of the increasing proportion of high digestible carbohydrates in the ears and the decreasing digestibility of the remaining plant fractions. The trend of decreasing DM and OM digestibility

Table 2 In vivo digestibility (%) of the wheat silages used in the trial Stage of maturity DM OM N C EE CF NDF ADF Energy

B 73.4 75.6 74.8 74.6 74.0 75.9 71.8 72.6 74.7

MB 67.1 68.9 61.4 67.0 71.3 68.5 65.5 67.7 67.5

M 59.2 61.4 55.8 61.1 61.8 52.5 52.9 53.0 61.2

D 59.6 62.0 53.5 60.4 57.2 29.9 34.5 34.5 60.2

S.E.M.

B vs. MB

B vs. M

B vs. D

MB vs. M

MB vs. D

M vs. D

0.76 0.68 1.21 0.42 3.11 3.77 1.68 1.35 0.71

*** *** *** *** NS NS ** * ***

*** *** *** *** ** *** *** *** ***

*** *** *** *** *** *** *** *** ***

*** *** ** *** * ** *** *** ***

*** *** *** *** ** *** *** *** ***

NS NS NS NS NS *** *** *** NS

B5Boot stage; MB5midbloom stage; M5milk stage; D5dough stage. * P,0.05; ** P,0.01; *** P,0.001.

G.M. Crovetto et al. / Livestock Production Science 55 (1998) 21 – 32

values with growth stage of wheat confirms the results obtained by other authors (McCullough and Sisk, 1967; Cannel and Jobson, 1968; Adogla-Bessa and Owen, 1995b). Bolsen and Berger (1976) in one trial with lambs obtained higher DM digestibility values with rations based on boot and dough wheat silages than with a ration containing milk stage silage but in another trial they did not register any variation in DM or CP digestibility of the ration with the maturity of the wheat. In both trials the digestibility of the crude fibre in the rations significantly decreased as plant maturity increased. In a trial with lactating cows treated with markers, Arieli and Adin (1994) observed no relationship between DM, OM and CP digestibility and maturity, but they did obtain, in agreement with our results, a reduction of the apparent digestibility and in situ degradability of NDF between flowering and the end of the milk stage. ¨ In contrast, Sudekum et al. (1995) reported a slight but significant increase in DM and OM digestibility from the late milk to hard dough stage when steers and wethers were fed at maintenance level, but digestibility values did not change with maturity when intake was ad libitum. Adesogan (1996) reported that the in vivo digestibility of OM and energy, measured at maintenance, was lower for WCWS cut at 51.6% DM than WCWS cut at 37.6% DM, but the digestibility coefficient increased again in the last cut (63.2% DM); however, the chemical composition and stage of maturity of the wheat silages studied in that experiment were quite different from those in the present work. The energy digestibility of a WCWS, cut at 37.6% DM (Adesogan, 1996) and at a stage of growth similar to our last product (D), was higher than the value obtained in the current trial (66.3 vs. 60.2%). The digestibility values for DM, OM and energy in the D stage silage of the present trial were slightly lower than the data obtained in a previous experiment on a wheat silage in an analogous stage of maturity (Succi et al., 1993); nevertheless, it is important to consider that the chemical composition of the dough stage silage previously studied was intermediate between the M and D silages of the present trial. The energy digestibility of wheat silage at the milk-dough stage of grain maturity reported by the

25

INRA (1988) is only 55%, which is much lower than the values for the M and D stages in the present study (61.2 and 60.2%, respectively).

3.3. In vitro digestibility The IVOMD determined on the ten forage samples had a quadratic trend of variation as shown by the equation in Fig. 1 (R 2 50.94). The minimum predicted value was achieved at the milk stage of grain maturity. IVOMD had a similar trend to the in vivo data, but both the actual and predicted in vitro values were generally higher than the in vivo values, particularly in the last phase when the in vivo results tended to become stable while the IVOMD values tended to increase again. This discrepancy can probably be explained, on one hand, by the effect of ensiling of forages tested in vivo and, on the other hand, by the influence of the intake level on in vivo OM digestibility: in fact, the significant increase of DM and OM intakes from M to D stage silages probably caused a depression of in vivo OM digestibility. Tremblay et al. (1995) found IVOMD values comparable to those of the present study at the same stages of plant growth, but with a clear trend of decreasing digestibility with stage of growth. In contrast, Adogla-Bessa and Owen (1995a) observed a slight tendency towards increasing in vitro digestibility with plant maturity.

3.4. Energy utilisation Table 3 reports the energy utilisation of the four wheat silages. When the results were expressed as a percentage of GE intake (GEI), faecal energy losses increased with stage of maturity, with the differences being significant between the first three stages but not between M and D stages. As a consequence, DE (% GEI) registered a progressive and significant decrease from stage B to M, with a stasis in the last step. It should be underlined that DE, if expressed in terms of metabolic liveweight (MW5BW 0.75 ), was higher in stage D than in stages MB and M, probably because of the higher feed intake. Urinary energy losses (% GEI) tended to decrease with plant maturity, mainly in the later stages, in correlation with the reduction of the silage CP content. A similar trend

26

G.M. Crovetto et al. / Livestock Production Science 55 (1998) 21 – 32

Fig. 1. Relationship between date of harvesting and in vivo and in vitro OM digestibility of the wheat tested in the trial.

was observed for methane energy losses (% GEI), which fell slightly from the B to D stage although the differences were never significant. ME showed a trend similar to DE independently of whether it was expressed in kJ / BW 0.75 d 21 or as a percentage of GEI. Heat production, when expressed as an absolute value, followed the same trend as GEI, with the highest value for treatment B and minimum values for the two intermediate cuts; however, when expressed as a percentage of ME, heat expenditure associated with silage B was significantly lower than the other treatments. As a consequence, RE was positive only for the B stage. Information in the literature concerning the variation of energy utilization of WCWS with plant maturity is very scarce. The only data appears to have been reported by Adesogan (1996) for wheat silages cut at later stages of maturity than forages of the present trial. In comparison with our last stage (D), the first stage ‘‘control’’ of year one reported by Adesogan (1996) had similar losses of urine (4.1 vs. 3.8% GE) and methane energy (6.8 vs. 7.2% GE), but a higher metabolizability (ME / GE50.544 vs. 0.493) and ME (10.9 vs. 9.3 MJ / kg DM). These differences are consistent with those reported for energy digestibility. Despite the fact that the NDF

and ADF contents of the WCWS studied by Adesogan (1996) were similar to those of our stage D, it is probable that the different genetic and climatic conditions led to a lower lignin content. In fact, the NDF digestibility reported by Adesogan was much higher than the value obtained in the current work (58.5 vs. 34.5%).

3.5. Nutritive value The energy content of the four wheat silages, expressed as MJ / kg DM, are reported in Table 4. DE decreased significantly from B to D stage. ME and NE l (expressed as UFL / kg DM) also fell with increasing stage of plant growth but the differences were significant only between the first and the last three stages. The nutritive values were very high, especially for the boot stage (1.09 UFL / kg DM). The feed value of the D stage wheat silage (0.76 UFL / kg DM) was similar to but slightly lower than the value (0.81 UFL / kg DM) obtained in a previous trial with wheat silage at the same stage of maturity (Succi et al., 1993). The INRA (1988) suggests a much lower nutritive value for WCWS at the milkdough stage (0.64 UFL / kg DM), but this is consistent with the low GE content and the low energy

Table 3 Energy utilization of the wheat silages used in the trial Stage of maturity a

B 21

MB

M

D

S.E.M.

B vs. MB

B vs. M

B vs. D

MB vs. M

MB vs. D

M vs. D

746.3

806.3

938.0

55.80

**

**

NS

NS

*

NS

Faecal energy (FE)a (kJ / kg MW d 21 ) (% GEI)

255.4 25.3

251.9 32.5

307.4 38.8

367.4 39.8

21.66 0.71

NS ***

* ***

*** ***

NS ***

** ***

* NS

Digestible energy (DE)a (kJ / kg MW d 21 ) (% GEI)

762.8 74.7

494.4 67.5

498.8 61.2

570.6 60.2

37.69 0.71

*** ***

*** ***

*** ***

NS ***

NS ***

NS NS

Urinary energy (UE)a (kJ / kg MW d 21 ) (% GEI)

58.0 5.8

42.9 5.8

34.7 4.3

36.1 3.8

2.07 0.24

*** NS

*** ***

*** ***

* ***

* ***

NS NS

Methane gas energy (MGE)b (kJ / kg MW d 21 ) (% GEI)

76.6 7.5

54.0 7.3

59.3 7.4

67.4 7.2

3.18 0.22

* NS

* NS

NS NS

NS NS

NS NS

NS NS

Metabolizable energy (ME)b (kJ / kg MW d 21 ) (% GEI)

630.6 61.5

399.3 54.6

405.0 49.5

467.6 49.3

45.65 1.35

* *

* *

NS *

NS NS

NS NS

NS NS

Heat production (HP)b (kJ / kg MW d 21 ) (% GEI) (% ME)

552.3 54.8 89.3

458.0 59.6 108.1

457.7 57.2 116.7

476.7 52.2 105.8

17.28 2.18 1.78

* NS *

* NS **

* NS *

NS NS NS

NS NS NS

NS NS *

Retained energy (RE)b (kJ / kg MW d 21 ) (% GEI) (% ME)

78.3 6.7 10.7

258.7 25.0 28.1

252.7 27.8 216.7

29.1 22.9 25.8

29.28 1.53 1.78

NS * *

* * **

NS * *

NS NS NS

NS NS NS

NS NS *

G.M. Crovetto et al. / Livestock Production Science 55 (1998) 21 – 32

1018.2

GE intake (GEI) (kJ / kg MW d )

B5Boot stage; MB5midbloom stage; M5milk stage; D5dough stage. * P,0.05; ** P,0.01; *** P,0.001. a Data computed individually (n532). b Data computed by pair (n516).

27

28

Stage of maturity a

Gross energy (GE) (MJ / kg DM) Digestible energy (DE)a (MJ / kg DM) Metabolizable energy (ME)b (MJ / kg DM) km Net energy for maintenance (NE m )c (MJ / kg DM) Net energy for lactation (NE l )d (MJ / kg DM) UFL e (No. / kg DM)

B

MB

M

D

S.E.M.

B vs. MB

B vs. M

B vs. D

MB vs. M

MB vs. D

M vs. D

20.61 15.39 12.67 0.73 9.26 7.74 1.09

19.80 13.37 10.80 0.71 7.66 6.41 0.90

19.75 12.09 9.77 0.70 6.81 5.69 0.80

18.78 11.33 9.26 0.70 6.44 5.39 0.76

0.028 0.141 0.266 0.004 0.227 0.190 0.027

*** *** * * * * *

*** *** ** * ** ** **

*** *** ** * ** ** **

NS *** NS NS NS NS NS

*** *** * NS NS NS NS

*** *** NS NS NS NS NS

B5Boot stage; MB5midbloom stage; M5milk stage; D5dough stage. * P,0.05; ** P,0.01; *** P,0.001. a Data computed individually (n532). b Data computed by pair (n516). c NE m 5MEk m 5ME(0.55410.287ME / GE). d NE l 5MEk l 5ME(0.463210.24ME / GE). e 1 UFL57.1128 MJ NE l

G.M. Crovetto et al. / Livestock Production Science 55 (1998) 21 – 32

Table 4 Energy content of the wheat silages used in the trial

Stage of maturity

B

Carbon balance C intake a (g / kg MW d 21 ) C faecal losses a (g / kg MW d 21 ) C urine losses a (g / kg MW d 21 ) C-CH 4 losses b (g / kg MW d 21 ) C-CO 2 losses b (g / kg MW d 21 ) C retention b (g / kg MW d 21 )

23.35 5.87 1.24 1.04 13.40 1.86

Nitrogen balance N intake a (g / kg MW d 21 ) N faecal losses a (g / kg MW d 21 ) N urine losses a (g / kg MW d 21 ) N retention a (g / kg MW d 21 )

MB

M

D

S.E.M.

B vs. MB

B vs. M

B vs. D

MB vs. M

MB vs. D

M vs. D

17.53 6.03 0.97 0.73 10.69 0.04

18.72 7.15 0.75 0.80 10.65 20.39

21.94 8.55 0.78 0.91 12.28 20.79

1.283 0.461 0.043 0.043 0.321 0.862

** NS *** * * NS

** * *** * * NS

NS *** *** NS NS NS

NS NS ** NS NS NS

* ** ** NS NS NS

NS * NS NS * NS

1.17 0.30 0.67 0.20

0.59 0.25 0.46 20.12

0.56 0.24 0.31 0.00

0.67 0.30 0.37 20.02

0.057 0.016 0.016 0.050

*** * *** ***

*** ** *** **

*** NS *** **

NS NS *** NS

NS * ** NS

NS ** ** NS

Protein deposition a (g / kg MW d 21 )

1.22

20.72

0.00

20.09

0.315

***

**

**

NS

NS

NS

Fat deposition b (g / kg MW d 21 )

1.59

0.12

20.61

20.86

0.750

NS

NS

NS

NS

NS

NS

B5Boot stage; MB5midbloom stage; M5milk stage; D5dough stage. * P,0.05; ** P,0.01; *** P,0.001. a Data computed individually (n532). b Data computed by pair (n516).

G.M. Crovetto et al. / Livestock Production Science 55 (1998) 21 – 32

Table 5 Carbon and nitrogen balance of the wheat silages used in the trial (on kg MW)

29

30

G.M. Crovetto et al. / Livestock Production Science 55 (1998) 21 – 32

estimated for silage B (20.51 MJ / kg DM; 26.6%) and overestimated for the other silages, particularly for the milk and dough stages (11.15 and 11.13 MJ / kg DM; 120.2 and 121.0%, respectively). The data in Table 6 indicate that harvesting wheat at the D stage is more convenient in terms of NE yield; in fact, the higher DM yield compensated for the low nutritive value. However, for a double cropping system, the entire NE yield per hectare from both the wheat and maize silages must be considered. Increasing wheat maturity gave a higher NE yield for the winter cereal but a lower NE yield from the maize silage. Assuming that under the Po plain climatic and agronomic conditions, each day of delay in sowing the maize reduces maize silage yield by about 100 kg DM / ha, the predicted NE yield per hectare remains fairly constant for the four stages considered. Nevertheless, in the climatic conditions of Northern Italy, delaying the maize harvest to the end of September or October increases the risks of plant disease and consequently reduces the forage quality and nutritive value. Moreover, the choice of harvesting wheat at the dough stage penalises the fibrous components of the forage and increases the dietary non structural carbohydrates (NSC) content. After these considerations, for a double cropping system, we recommend cutting whole crop wheat between the midbloom and the milk stage of maturity, depending on local weather conditions.

digestibility of the wheat silage reported by the French tables.

3.6. Carbon and nitrogen balance Table 5 shows C and N balances expressed as g / kg MW. As expected from the energy utilization data, protein and fat depositions were only positive for the B stage and were significantly different from the other stages. In the last two stages, the N balances were close to zero while the C balances, and consequently fat deposition, were strongly negative. In contrast, fat deposition in the MB stage was slightly positive while N balance was negative, due to the high urinary N losses.

3.7. DM and NEl yield DM yield per hectare (Table 6) increased with crop growth stage, but DM yields for all stages were lower than expected because of adverse weather conditions (drought) and the yields can be considered acceptable only for the last two stages. The higher energy content of the silages in the first two stages was insufficient to compensate for the lower DM yield. The nutritive value (NE l ) of the wheat silages calculated with INRA (1988) equations was under-

Table 6 DM, NE for lactation (NE l ) and feed energy units (UFL) yield of the wheat silage Stage of maturity

B

MB

M

D

DM yield (kg / ha)

3359

5009

6945

9601

NE al (MJ / kg DM) (MJ / ha)

7.74 26 009

6.41 32 098

5.69 39 517

5.39 51 701

NE bl (MJ / kg DM) (MJ / ha)

7.23 24 273

6.76 33 880

6.84 47 476

6.52 62 625

UFL a (No. / kg DM) (No. / ha)

1.09 3657

0.90 4513

0.80 5556

0.76 7269

UFL b (No. / kg DM) (No. / ha)

1.02 3413

0.95 4763

0.96 6675

0.92 8805

B5Boot stage; MB5midbloom stage; M5milk stage; D5dough stage. a Data obtained in the present trial. b Data calculated according to INRA (1978), (1988).

G.M. Crovetto et al. / Livestock Production Science 55 (1998) 21 – 32

4. Conclusions Wheat silage had a similar chemical composition and nutritive value to Italian ryegrass and barley silages (Succi et al., 1993, 1995; Crovetto et al., 1996). The high nutritive value suggests that wheat silage could be successfully used in dairy cow rations. Moreover the high DM content and the good level of water soluble sugars allow ensiling without wilting with an advantage in terms of reduced risks of soil and Clostridia contamination and a simplified harvesting process. The energy value of WCWS decreased with stage of maturity while DM yield per hectare rose. The higher energy content of the silages in the first two stages in comparison to the last stages was insufficient to compensate for the lower DM yield: therefore NE l or UFL yield per hectare of the wheat at the dough stage was double that of the boot stage. Nevertheless, in a double cropping system (winter cereal and maize) the earlier harvesting dates of the immature stages allow earlier sowing and a higher UFL yield of maize; this effect can balance the UFL losses from the wheat crop, at least from the midbloom stage of maturity. Furthermore, sowing the maize earlier could reduce the weather and disease risks to the maize crop at harvest. In conclusion the data obtained in the present study suggest that, as a compromise between yield and quality, for a double cropping system, the most convenient stage of maturity for harvesting whole crop wheat for silage is between the midbloom and the milk stage.

Acknowledgements The authors are indebted to Dr. Giuseppe and Dr. Giovanni Devizzi, owners of the farm La Pagnana of Castiraga Vidardo (Lodi) for their kind assistance. This research was supported by the Italian National Research Council, special project RAISA, subproject No. 3, paper No. 2973.

References Adesogan A.T., 1996. Prediction of the nutritive value of whole crop wheat. Ph.D. Thesis, University of Reading, Reading, UK.

31

Adogla-Bessa, T., Owen, E., 1995. Ensiling of whole-crop wheat with cellulase–hemicellulase based enzymes. 1. Effect of crop growth stage and enzyme on silage composition and stability. Anim. Feed Sci. Technol. 55, 335–347. Adogla-Bessa, T., Owen, E., 1995. Ensiling of whole-crop wheat with cellulase–hemicellulase based enzymes. 2. Effect of crop growth stage and enzyme on silage intake, digestibility and live-weight gain by steers. Anim. Feed Sci. Technol. 55, 349–357. Arieli, A., Adin, G., 1994. Effect of wheat silage maturity on digestion and milk yield in dairy cows. J. Dairy Sci. 77, 237–243. ASPA Commissione Valutazione Degli Alimenti, 1980. Valutazione degli alimenti di interesse zootecnico. 1 Analisi chimica. Zoot. Nutr. Anim. 6, 19–34. Bolsen, K.K., Berger, L.L., 1976. Effect of type and variety and stage of maturity on feeding values of cereal silages for lambs. J. Anim. Sci. 42, 168–174. Bolsen, K.K., Berger, L.L., Conway, K.L., Riley, J.G., 1976. Wheat, barley and corn silages for growing steers and lambs. J. Anim. Sci. 42, 185–191. Brouwer, E., 1958. On simple formulae for calculating the heat expenditure and the quantities of carbohydrate and fat metabolized in ruminants from data on gaseous exchange and urine N. In: Proc. 1st Symp. Energy Metabolism. E.A.A.P., pp. 182– 194. Brouwer, E., 1965. Report of sub-committee on costants and factors. In: Proc. 3rd Symp. Energy Metabolism of Farm Animals. E.A.A.P., publ. 11, pp. 441–443. Cannel, R.Q., Jobson, H.T., 1968. The relationship between yield and digestibility in spring varieties of barley, oats and wheat after ear emergence. J. Agric. Sci. 71, 337–341. Crovetto, G.M., 1984. Apparecchiature e correzioni richieste per il calcolo del calore animale usando il metodo della calorimetria indiretta a circuito aperto. Zoot. Nutr. Anim. 4, 279–297. Crovetto, G.M., Tamburini, A., Rapetti, L., Galassi, G., Succi, G., 1996. Valore nutritivo di insilati di loiessa (Lolium Multiflorum Lam.): confronto tra il doppio taglio e il taglio unico. Zoot. Nutr. Anim. 22, 59–67. ` Dulphy, J.P. and Demarquilly, C., 1981. Problemes particuliers ´ aux ensilages. In: Demarquilly, C. (Ed.), Prevision de la Valeur Nutritive des Aliments des Ruminants. INRA, Versailles, pp. 81–104. INRA, 1978. Alimentation des ruminants. INRA, Paris, 622 pp. INRA, 1988. Alimentation des bovins, ovins et caprins. INRA, Paris, 476 pp. Mannerkorpi, P., Brandt, M., 1993. Feeding value of whole-crop wheat silage for ruminants related to stage of maturity and cutting height. Arch. Anim. Nutr. 45, 89–100. McCullough, M.E., Sisk, L.R., 1967. Influence of stage of maturity at harvest and level of grain feeding on intake of wheat silage. J. Dairy Sci. 50, 705–708. Nijkamp, H.I., 1969. Determination of the urinary energy and carbon output in balance trials. Zeit. Tierph., Tierer. Futtermitt. 1, 1–9. Nijkamp, H.I., 1971. Some remarks and recommandations concerning bomb calorimetry. Zeit. Tierph., Tierer. Futtermitt. 2, 111–121.

32

G.M. Crovetto et al. / Livestock Production Science 55 (1998) 21 – 32

SAS / STAT, 1994. Release 6.10. SAS Institute Inc., Cary, NC. Succi, G., Crovetto, G.M., Tamburini, A., Rapetti, L. and Galassi., G., 1993. Determinazione dell’energia netta dell’insilato di frumento raccolto alla maturazione cerosa della granella. In: Proc. 47th National Meeting of the Italian Society of Veterinary Science (S.I.S.Vet.), pp. 1733–1737. Succi, G., Crovetto, G.M., Tamburini, A., Rapetti, L. and Galli, A., 1995. Nutritive value of barley silage. In: Proc. 11th National Meeting of the Scientific Association of Animal Production (A.S.P.A.), Grado (GO), pp. 245–246. ¨ ¨ H., Brandt, M., Rave, G., Stangassinger, Sudekum, K.-H., Roh, M., 1995. Comparative digestion in cattle and sheep fed wheat silage diets at low and high intakes. J. Dairy Sci. 7, 1498– 1511. Tamburini, A., Rapetti, L., Crovetto, G.M., Succi, G., 1995. Rumen degradability of dry matter, NDF and ADF in Italian

ryegrass (Lolium multiflorum) and winter cereals silages. Zoot. Nutr. Anim. 21 (Suppl.), 75–80. Tilley, J.M.A., Terry, R.A.J., 1963. A two-stage technique for the in vitro digestion of forage crops. J.B. Grassl. Soc. 18, 104– 144. Tremblay, G.F., Pageau, D., Surprenant, J., Petit, H.V., Drapeau, ´ et du stade de coupe R., 1995. Effet de la fertilization azotee sur le rendement, la composition chimique et la digestibilite´ in ´ ´ ` vitro des cereales plantes entieres. Ann. Zootechnol. 44 (Suppl.), 45. Weinberg, Z.G., Ashbell, G., Hen, Y., Harduf, Z., 1991. Ensiling whole wheat for ruminant feeding at different stages of maturity. Anim. Feed. Sci. Technol. 32, 313–320. Van Es, A.J.H., 1978. Feed evaluation for ruminants. (1) The system in use from May 1977 onwards in the Netherlands. Livest. Prod. Sci. 5, 95–107.