www.elsevier.com/locate/fcr

Field Crops Research 100 (2007) 1–9

Effect of harvest time on yield and pre-harvest quality of semi-leafless

grain peas (Pisum sativum L.) as whole-crop forage

Giorgio Borreani a,*, Pier Giorgio Peiretti b, Ernesto Tabacco a

a Dipartimento di Agronomia, Selvicoltura e Gestione del Territorio, Universita di Torino, via L. da Vinci 44, 10095 Grugliasco (TO), Italyb Istituto di Scienze delle Produzioni Alimentari, CNR, via L. da Vinci 44, 10095 Grugliasco (TO), Italy

Received 3 November 2005; received in revised form 19 April 2006; accepted 19 April 2006

Abstract

The aim of the work was to study changes in the yield and nutritional characteristics of whole crop semi-leafless field pea over two growing

seasons in the Po plain, Italy. Samples of two cultivars (Baccara and Sidney) were collected from flowering to grain maturity. The

developmental stage, yield, dry matter (DM) content, crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), acid

detergent lignin (ADL), starch, water soluble carbohydrates (WSC), gross energy (GE), organic matter digestibility (OMD) and the net energy

for lactation (NEL) were determined at each harvest. The forage characteristics were regressed on the growing degree days (GDD) with 4.4 8Cas the base temperature. The DM yield increased with advancing maturity from 0.5 to 8.91 Mg ha�1, while the CP decreased from 261 to

159 g kg�1 DM. During the whole growth cycle the GE, OMD, NEL and milk forage units (milk FU) were almost steady. No differences were

observed between the cultivars for any of the measured parameters. At grain maturity, the crop produced over 4.0 Mg ha�1 DM of grain. The

CP, starch and WSC of the grain did not show any differences between the cultivars or years. The data showed that the nutritive quality of the

forage of the semi-leafless grain pea harvested as a whole crop for ensiling purposes did not diminish with maturity and could help improve the

self-sufficiency of dairy farms, in terms of home-grown protein forages.

# 2006 Elsevier B.V. All rights reserved.

Keywords: Growing degree days; Growth stage; DM yield; OM digestibility; NDF; Peas

1. Introduction

The European bans on feeding fish or animal protein meals

to livestock have highlighted the huge deficit in plant protein

in the EU (>75% in 2000), and have led to considerable

pressure on livestock farmers to produce home-grown

alternative forages (Wilkins and Jones, 2000), that are high

in protein and energy. Peas (Pisum sativum L.) are mainly

used for grain production throughout the world, however, this

species is sometime used alone or in combination with spring

cereals as whole-crop forage (Faulkner, 1985; Mustafa et al.,

2002). Pea seed contain a moderate amount of high quality

protein and a high level of starch, thus making this crop a

unique dual-purpose feed, rich in both energy and protein

(Cousin, 1997). Peas can offer farmers a great deal of

* Corresponding author. Tel.: +39 011 6708783; fax: +39 011 6708798.

E-mail address: giorgio.borreani@unito.it (G. Borreani).

0378-4290/$ – see front matter # 2006 Elsevier B.V. All rights reserved.

doi:10.1016/j.fcr.2006.04.007

flexibility in their cropping rotations due to their quick growth

in a short period providing forage of a high nutritive value and

palatability (Koivisto et al., 2003). Due to their relatively high

moisture content, peas are rarely harvested for hay and they

are most often ensiled as a whole crop to provide both protein

and starch sources for livestock (Mustafa and Seguin, 2004),

which allows for a minimal feeding of purchased concentrates

without adversely affecting milk yield or quality (Adesogan

et al., 2004). Mustafa et al. (2000) reported that whole pea

silages, harvested at full pod stage, can successfully replace

barley or alfalfa silage as a forage source for high yielding

dairy cows in early lactation, while Børsting and Weisbjerg

(2002) found that feeding pea silage harvested with

undeveloped seeds to dairy cows led to a lower dry matter

(DM) intake, milk yield, and milk protein yield in comparison

to perennial ryegrass silage made with a comparable crude

protein content. Date of harvest and hence stage of maturity at

which crops are harvested will greatly affect forage yield and

G. Borreani et al. / Field Crops Research 100 (2007) 1–92

quality. Several studies have reported that delaying harvesting

of pea past the flowering stage may result in significantly

greater forage DM yields (Aman and Graham, 1987; Mustafa

and Seguin, 2004). Reduction in forage and seed yield have

often been attributed to lodging, which is particularly evident

in the leafed varieties, while the semi-leafless phenotypes are

less susceptible (Koivisto et al., 2003; Uzun et al., 2005). With

grasses and leguminous forages quality forage can be

obtained by management strategies that are directed towards

cutting when the leaf to stem ratio is high (Marten et al., 1988;

Nelson and Moser, 1994). When pulses are to be used as

whole-crop forage the management strategies differ because

the grain and pod yields are also important (Salawu et al.,

2001). Selection of an optimal harvest date will require a

better understanding of the chemical changes that occur

during maturation and of the feeding value of the crop at

different stages of development (Aman and Graham, 1987).

Nutritive value has been related to accumulated growing

degree days (GDD), crop age in days, leaf to stem ratio, stand

height and codified morphological stage (Nelson and Moser,

1994). The GDD, involving the sum of daily mean

temperature above a given base temperature, is widely used

with peas to predict relative maturity during the growing

season (Bourgeois et al., 2000; Mikkelsen, 1981). A base

temperature from 0 to 5.0 8C was generally adequate for all

cultivars to compute growing degree days between sowing

and maturity, although a base temperature of 4.4 8C was often

reported to be the most satisfactory for green pea (Bourgeois

et al., 2000).

Little information can be found in the literature on the

changes in yield potential and nutritional quality during the

growth cycle of peas sown in spring and grown to be ensiled

as a whole-crop in southern Europe. The objective of this

study was to provide information on the effect of harvest

time on the pre-harvest nutritional quality and DM yield of

two cultivar of semi-leafless peas over a 2-year period in the

Po plain in Northern Italy.

2. Materials and methods

2.1. Plant material and environmental conditions

The research was carried out in the 2001 and 2002 growing

seasons in the Western Po plain near Torino (448500N, 78400E,

altitude 232 m above sea level, annual mean temperature

11.7 8C, and annual average rainfall 739 mm) on a sandy-

loam textured alluvium soil with a pH measured in water of

7.6. The sand, silt, and clay contents of the soil were 470, 440,

and 90 g kg�1, respectively at 0–30 cm depth. The organic C

was 11.8 g kg�1 and organic N was 1.45 g kg�1. Two semi-

leafless pea cultivars (Baccara and Sydney) were selected as

they were among the best known commercial lines adapted to

the area, at the time of the initiation of the study (Battini et al.,

2001). Stands were sown at 230 kg ha�1 of naked viable seed

on 21 March in 2001 and at 340 kg ha�1 on 28 February in

2002 to enable better competition with weeds. No irrigation or

fertiliser was applied after sowing. Weeds were controlled by

a post-emergence treatment using 0.9 kg a.i. ha�1 of benta-

zone in 2001. Temperature and rainfall data were collected

from a weather station approximately 60 m from the

experiment site. Herbage samples for the yield and quality

measurements were collected with a Haldrup forage plot

harvester on 12 m2 randomly located subplots with two

replicates in 30 m � 45 m main plots (two plots per cultivar).

Forage was cut to a 3–4 cm stubble height. Herbage samples

were collected four to five times at progressive morphological

stages from flowering to late seed pod stage from the middle of

May to the end of June.

At each sampling time, when pods were present, sub-

samples of 30 plants were divided into seeds and other plant

components (tendrils, stipules, stems, inflorescences and

pods), to determine the grain contribution to the DM yield.

Crops were also harvested at grain maturity (beginning of

July) to evaluate the grain and straw production and quality.

A complete nutritive analysis of the straw was only made in

2002 in order to better characterise the role of this crop

component for animal nutrition purposes.

2.2. Chemical analysis

Chemical analyses were performed on the whole-plant,

the grain and the straw samples. The whole-plant and straw

samples were chopped to a length of 20–30 mm. All samples

were immediately dried in a forced-draft oven at 60 8C, air

equilibrated, weighed, ground in a Cyclotec mill (Tecator,

Herndon, VA, USA) to pass a 1 mm screen, and stored for

qualitative analyses.

The dried samples were analysed to determine the total N,

according to the Dumas method, using a Nitrogen analyser

Micro-N (Elementar, Hanau, Germany). The crude protein

(CP) (total N x 6.25), ash by ignition to 550 8C, neutral

detergent fibre (NDF), acid detergent fibre (ADF), and acid

detergent lignin (ADL) were determined according to

Robertson and Van Soest (1981), while the sugar and starch

were determined as described in the subsequent paragraph.

Gross energy (GE) was determined using an adiabatic

calorimeter bomb (IKA C7000, Staufen, Germany), and the

organic matter digestibility (OMD) according to the two-

stage rumen fluid technique (Tilley and Terry, 1963). The

OMD values were expressed in vivo using the Goldman et al.

(1987) regression equation. Net energy, expressed as both

the net energy for lactation (NEL) and milk forage unit (milk

FU), was calculated by inserting the observed values of the

OMD and GE into the equations proposed by Andrieu and

Demarquilly (1987).

2.3. Sugar extraction and starch hydrolysis

measurements

Sugar and starch were determined using the methods

described by Rong et al. (1996) with some modifications.

G. Borreani et al. / Field Crops Research 100 (2007) 1–9 3

Table 1

Monthly and annual mean temperatures and accumulated precipitation for

the study period and the long term average

Month Temperature (8C) Rain (mm)

2001 2002 Mean

1976–2002

2001 2002 Mean

1976–2002

January 1.5 �1.7 0.7 16 6 36

February 4.8 4.1 3.3 16 149 33

March 8.7 9.4 7.7 68 55 52

April 11.1 12.0 10.9 10 64 96

May 17.9 16.2 16.0 183 153 112

June 20.1 22.1 19.6 8 81 74

July 22.3 21.6 22.0 25 129 39

Annual 12.3 12.3 11.7 480 1191 739

Approximately 8 mg of grains or 20 mg of whole plant were

rinsed four times with 80% (v/v) ethanol, using 1.0 mL

ethanol per rinse, centrifuged, and the supernatant decanted

into a graduated test tube. An anthrone reagent was added to

an aliquot containing up to 200 mg of free sugar, boiled for

20 min, and then cooled to room temperature in a cold water

bath. Absorbance was determined at 625 nm with a Unicam

Helios g spectrophotometer (Unicam, Cambridge, UK).

Total sugar contents were expressed on the basis of glucose

equivalent standards containing 0, 50, 75, 100, 150, and

200 mg glucose mL�1 80% ethanol.

The tube containing the ethanol-insoluble pellet was

placed in a 55 8C oven for 24 h to evaporate any residual

ethanol before starch hydrolysis. Distilled deionized water

(0.5 mL) was added to each tube and the starch was

gelatinized by boiling the samples for 10 min. After cooling

to room temperature, 2 U amyloglucosidase (Sigma Chemical

product A3514) and 80 U a-amylase (Sigma Chemical

product A2643) were added to each tube and incubated at

55 8C for 24 h in a 200 M acetate buffer (pH 5.0). At the end of

the incubation period, the samples were centrifuged at

16,000 � g for 10 min. The glucose released from the starch

hydrolysis was determined with a glucose Trinder reagent

(Sigma Chemical Diagnostic kit No. 315). Absorbance was

read at 505 nm and the results were compared with glucose

standards containing 0, 0.5, 1, 2.5, and 5 mg glucose mL�1

distilled deionized water. The starch concentration was

calculated by multiplying the glucose concentration by 0.9.

2.4. Statistical analysis

The data were analysed over the years and harvest maturity

through regression analysis and via an analysis of variance

(ANOVA), using the Statistical Package for Social Science (v

11.5, SPSS Inc., Chicago, IL, USA). All the chemical and

nutritional parameter analyses were performed in duplicate

and averaged for the statistical analyses. The resulting data

were averaged over the sub-plot replicates before regression

analysis and used as individual observations for ANOVA. The

data were regressed on the growing degree days (GDD) with a

4.4 8C base temperature (Mikkelsen, 1981) and on the age in

days from the seeding date, as independent variables. The

accumulated GDD was calculated using the following

formula for each year:P

{[(Tmax + Tmin)/2] � 4.4 8C};

where Tmax and Tmin are the daily maximum and minimum

temperatures, respectively, in degree Celsius. The average

temperature [(Tmax + Tmin)/2] was set equal to 4.4 8C if less

than 4.4 8C (McMaster and Wilhelm, 1997).

Linear and quadratic regressions were compared using

the Draper and Smith (1998) stepwise selection procedure to

select the best regression model at the 0.05 probability level.

The best equation for each parameter was selected using

coefficient of determination and root mean square error

(RMSE). All the determination coefficients (R2) reported in

this paper were adjusted for degrees of freedom. The

MANOVA analysis of covariance was used to verify the

equivalence of the equations for the cultivars and years. This

procedure allowed one to verify the hypothesis of

parallelism of the regression equations and, when this

was not rejected, the analysis of covariance was used to

evaluate the differences between the adjusted means. When

no differences were found a single regression line was

determined for the pooled data.

The chemical compositional data were analysed via

ANOVA, with their significance reported at a 0.05

probability level using the general linear model of SPSS.

3. Results

3.1. Weather data

The monthly means of air temperature and accumulated

rain, as well as the annual mean temperature and the annual

accumulated rain of the two experimental years from

January to July and the 27-year mean values are reported in

Table 1. The 2 years were characterised by mean

temperatures that were higher than the 27-year values,

especially in February and March. The accumulated GDD

were lower in 2002 than in 2001, due to the earlier seeding

date (28 February versus 21 March).

3.2. Morphological stage and DM yield

The effects of the cultivar and harvesting date on the DM

yield and grain proportion are shown in Table 2. The stages

considered before grain maturity were: late bud, 17 May

(Cut 1); end of flowering, 31 May (Cut 2); beginning of pod

filling, 7 June (Cut 3); advanced pod filling, 14 June (Cut 4),

and beginning of ripening, 21 June (Cut 5) in 2001; and 20%

of flowering, 15 May (Cut 1); beginning of pod filling, 3 June

(Cut 2); advanced pod filling, 13 June (Cut 3); and mid-

ripening, 20 June (Cut 4) in 2002. The physiological

maturity of the seeds was reached in 106 and 123 days from

seeding in 2001 and 2002, respectively, corresponding to

1259 and 1309 8C of GDD.

G. Borreani et al. / Field Crops Research 100 (2007) 1–94

Tab

le2

Gro

win

gd

egre

ed

ays

(GD

D),

DM

yie

ldan

dg

rain

pro

port

ion

of

the

two

cult

ivar

sin

20

01

and

20

02

Yea

r

20

01

20

02

Cu

ltiv

arC

ut

1C

ut

2C

ut

3C

ut

4C

ut

5G

rain

mat

uri

tyC

ut

1C

ut

2C

ut

3C

ut

4G

rain

mat

uri

ty

Dat

e1

7M

ay3

1M

ay7

Jun

e1

4Ju

ne

21

Jun

e5

July

15

May

3Ju

ne

13

Jun

e2

0Ju

ne

1Ju

ly

Day

sfr

om

seed

ing

57

71

78

85

92

10

67

69

51

05

11

21

23

Sta

ge

of

mat

uri

tyL

ate

bu

dE

nd

of

flow

erin

g

Beg

inn

ing

po

dfi

ll

En

dp

od

fill

Beg

inn

ing

rip

enin

g

Gra

in

mat

uri

ty

20

%

flow

erin

g

Beg

inn

ing

po

dfi

ll

En

dp

od

fill

Mid

rip

enin

g

Gra

in

mat

uri

ty

GD

D(4

.48C

)4

85

70

78

02

90

01

00

11

25

95

39

80

99

53

11

01

13

09

DM

yie

ld(M

gh

a�1)

Bac

cara

0.5

03

.66

5.4

67

.21

7.2

78

.69

1.2

84

.26

5.2

06

.18

6.6

2

Sid

ney

0.6

63

.64

4.6

57

.05

7.8

58

.91

1.5

14

.66

6.1

06

.36

7.4

1

Gra

inp

rop

ort

ion

(%D

M)

Bac

cara

00

11

25

48

48

03

94

56

46

1

Sid

ney

00

72

85

04

80

31

50

65

64

The different seeding rates in the 2 years resulted in plant

densities of 51 and 49 plants m�2 and 98 and 96 plants m�2,

for Baccara and Sidney in 2001 and 2002, respectively. The

DM yield increased with stage of maturity from 0.50 to

8.69 Mg ha�1 and from 0.66 to 8.91 Mg ha�1 in 2001 for

Baccara and Sidney, respectively and from 1.28 to

6.62 Mg ha�1 and from 1.51 to 7.41 Mg ha�1 in 2002 for

Baccara and Sidney, respectively. These increases were

obtained in 50 and 48 growing days, corresponding to 774

and 770 8C of GDD for 2001 and 2002, respectively. The

grain contribution to the DM yield was similar for the two

cultivars and reached values of 48% of the total DM in 2001

for both cultivars, and values of 61 and 64% in 2002, for

Baccara and Sidney, respectively.

3.3. Variation in DM content and nutritional quality of

the whole-plant during the growth cycle

The GDD was always a better descriptor of the change in

forage quality over the growth cycle from the beginning of

flowering to mid-ripening than the age in days from seeding.

For this reason, the following results are shown in relation to

the GDD only (Figs. 1–4).

The DM content of the herbage was low for early harvests

before flowering, with values of around 110 g kg�1, but

reachedvaluesof 191and221at advanced podfilling, and then

rapidly increased duringripening of the seed pod(Fig. 1a). The

ash content decreased with maturity from 115 to 72 g kg�1

DM for 2001 and from 84 to 67 g kg�1 DM for 2002, without

any differences between the cultivars. The CP content of the

whole plant decreased with advancing maturity with different

trends for the 2 years, both with high coefficients of

determination. No differences were observed between the

cultivars. After the beginning of pod filling, the CP was almost

constant at around a mean value of 170 g kg�1 DM for both

years (Fig. 1b). The WSC showed different trends for the years

in relation to the GDD. The values increased from 41 to

88 g kg�1 DM till the fourth cut and then decreased to

47 g kg�1 DM in the fifth cut in 2001, while it decreased with

increasing GDD from 115 to 15 g kg�1 DM, in 2002 (Fig. 2a).

The starch was directly related to the GDD with a single

quadratic regression line over the years and cultivars with

coefficient of determination greater than 0.90. The starch

values ranged from 19 to 249 g kg�1 DM with plant

development (Fig. 2b). The NDF content increased with the

same trend over the years and for the cultivars (Fig. 2c) with a

coefficient of determination of 0.904. TheADFand ADLwere

almost constant over the years for the cultivars with a mean

value of 235� 18.5 g kg�1 DM and 35.1 � 5.4 g kg�1 DM,

respectively. The GE and OMD of the herbage did not show

any significant relationship with the GDD and were almost

constant over the years and for the cultivars with a mean value

of 17.5 � 0.35 MJ kg�1 DM and of 806� 17.4 g kg�1 OM,

respectively. Consequently both the NEL and milk FU were

almost constant with a mean value of 6.80 � 0.24 MJ kg�1

and 0.955� 0.034 milk FU kg�1, respectively.

G. Borreani et al. / Field Crops Research 100 (2007) 1–9 5

Fig. 1. Dry matter (DM) (a) and crude protein (CP) (b) content of whole plant peas as a function of the growing degree days (GDD); filled symbols, 2001; empty

symbols, 2002. When no differences were found a single regression line was determined for the pooled data: (a) DM = 0.000847 GDD2 � 1.024 GDD + 445;

R2 = 0.920; RMSE = 19.7; (b) CP(2001) = 0.000172 GDD2 � 0.426 GDD + 427; R2 = 0.907; RMSE = 8.5; CP(2002) = 0.0878 GDD + 263; R2 = 0.761;

RMSE = 10.4.

Fig. 2. Water soluble carbohydrate (WSC) (a), starch (b) and NDF (c) contents of whole plant peas as a function of the growing degree days (GDD); filled

symbols, 2001; empty symbols, 2002. When no differences were found a single regression line was determined for the pooled data: (a) WSC(2001) = �0.000433

GDD2 + 0.693 GDD � 200; R2 = 0.595; RMSE = 10.7; WSC(2002) = �0.000486 GDD2 + 0.646 GDD � 100; R2 = 0.950; RMSE = 8.1; (b) Starch(2001–

2002) = 0.000186 GDD2 + 16.36; R2 = 0.914; RMSE = 16.9; (c) NDF(2001–2002) = 0.000504 GDD2 � 0.461 GDD + 409; R2 = 0.904; RMSE = 21.3.

3.4. Evolution of nutritional quality of plant

components during crop growth

The changes in the straw CP and NDF contents during

the growth cycle are reported in Fig. 3. The CP content

decreased with advancing maturity, following different

trends over the 2 years. In the period from the end of

flowering to the beginning of the pod filling stage (from

Fig. 3. Crude protein (CP) (a) and neutral detergent fibre (NDF) (b) of pea straw a

symbols, 2002. When no differences were found a single regression line was dete

RMSE = 12.7; CP(2002) = 0.000332 GDD2 � 0.904 GDD + 703; R2 = 0.924; R

R2 = 0.923; RMSE = 21.8.

700 to 800 8C of accumulated GDD) the CP content was

slightly lower than 200 g kg�1 DM, and decreased to a

mean value of 141 g kg�1 DM in 2001 and 91 g kg�1 DM

in 2002 at grain harvest (GDD from 1250 to 1300 8C)

(Fig. 3a). The NDF increased from values around

400 g kg�1 DM to higher than 500 g kg�1 DM in 2001

and 600 g kg�1 DM in 2002, respectively, at grain

harvesting (Fig. 3b).

s a function of the growing degree days (GDD); filled symbols, 2001; empty

rmined for the pooled data: (a) CP(2001) = 0.0861 GDD + 247; R2 = 0.684;

MSE = 11.1; (b) NDF(2001–2002) = 0.000494 GDD2 – 0.656 GDD + 602;

G. Borreani et al. / Field Crops Research 100 (2007) 1–96

Fig. 4. Crude protein (CP) (a), water soluble carbohydrate (WSC) (b) and starch (c) contents of pea grain as a function of the growing degree days (GDD); filled

symbols, 2001; empty symbols, 2002. When no differences were found a single regression line was determined for the pooled data: (a) CP(2001–2002) = 0.000634

GDD2 � 1.414 GDD + 1010; R2 = 0.700; RMSE = 12.4; (b) WSC(2001–2002) = 0.000911 GDD2 � 2.136 GDD + 1262; R2 = 0.973; RMSE = 6.9; (c)

Starch(2001–2002) = �0.00322 GDD2 + 7.374 GDD � 3597; R2 = 0.876; RMSE = 44.7.

The changes in grain CP, WSC and starch content during

the growth cycle are reported in Fig. 4. The crude protein

content of the grain during the filling of the seeds slightly

decreased from 286 g kg�1 DM in the first phase to a mean

value of 234 g kg�1 DM in the following maturation phases

with no differences between the years or cultivars (Fig. 4a).

The WSC content decreased faster with advancing maturity

to values of around 20 g kg�1 DM (Fig. 4b). The decrease in

WSC was coupled to an increase in starch accumulation in

the seed tissue that increased from around 250 g kg�1 DM to

values of 556 g kg�1 DM (Fig. 4c).

3.5. Nutritional quality of grain and straw at grain

maturity

The DM yield and composition of the grain and of the

straw at the end of the cycle over the years and for the

cultivars are reported in Table 3. The stands produced over

Table 3

Dry matter (DM) yield, crude protein (CP), starch content and water soluble carboh

for straw for the two cultivars at grain maturity, in 2001 and 2002

Year

2001 2002

Baccaraa Sidney Baccara

Grain

DM yield (Mg ha�1) 4.21 4.28 4.06

CP (g kg�1 DM) 249 218 246

Starch (g kg�1 DM) 553 530 577

WSC (g kg�1 DM) 20 20 22

Straw

DM yield (Mg ha�1) 4.48 4.63 2.57

CP (g kg�1 DM) 131 151 96

NDF (g kg�1 DM) 532 542 586

a Cultivar.b C: cultivar effect; Y: year effect; S.E.M.: standard error of the mean.c NS: not significant, P > 0.05.* P < 0.05

** P < 0.01.*** P < 0.001.

4.0 Mg DM ha�1 of grain for the two cultivars and years.

The crude protein, starch and WSC did not show any

differences between the cultivars or years.

Straw DM yield in 2001 was about double that of 2002,

with no differences between the cultivars. The crude protein

of the straw was higher in 2001 than in 2002 (141 g kg�1 DM

versus 91 g kg�1 DM) with slight differences between

cultivars in 2001, while the NDF was higher in 2002 and

for the Sidney cultivar. A complete nutritive analysis of the

straw was performed in 2002. No significant differences were

found between the cultivars except for the ADL values

(94 g kg�1 versus 106 g kg�1 DM for Baccara and Sidney,

respectively). The OMD, GE, NEL, and milk FU mean values

were 471� 33 g kg�1 OM, 16.5 � 0.4 MJ kg�1 DM,

3.33 � 0.26 MJ kg�1 DM, 0.47 � 0.04 kg�1 DM, respec-

tively. The residual starch and WSC values were

14.9 � 9.5 g kg�1 DM and 5.9� 1.5 g kg�1 DM, respec-

tively.

ydrate (WSC) for grain and DM yield, CP and neutral detergent fibre (NDF)

Yb C Y � C S.E.M.

Sidney

4.74 NSc NS NS 0.67

241 NS NS NS 15.7

566 NS NS NS 56.3

20 NS NS NS 2.53

2.67 ** NS NS 0.48

86 *** NS * 9.95

627 ** * NS 19.9

G. Borreani et al. / Field Crops Research 100 (2007) 1–9 7

4. Discussion

By sowing the crop in March rather than the fall,

excellent stand establishment was obtained, and the risk of

winter chill damage was minimized. The GDD was found to

give a more reliable description of the evolution of the

agronomic and nutritional parameters and to be more

independent of the sowing time than the age in days from

seeding date. This has also been observed in lucerne by Fick

et al. (1994) and in sainfoin by Borreani et al. (2003).

The crop produced a high DM yield in the 13 or 16-week

growing cycles from seeding to harvesting for the two years.

This short-term catch-crop harvested as silage would allow a

subsequent maize or soybean crop to be grown in the same

year in the Po plain environment (Tabacco, personal

communication). A DM yield higher than 5.0 Mg ha�1

was reached at the beginning of pod fill; Trevino et al. (1987)

observed halved yields at the same stage of growth in Spain,

while similar yields were observed by Mustafa and Seguin

(2004) between 8 and 10 weeks after seeding in the colder

Canadian environment, both for peas cultivated on their own

or as a pea-cereal mixture. In the UK environment, Fraser

et al. (2001) obtained 5.4 Mg ha�1 at 10 weeks from seeding

and 6.2 Mg ha�1 at 12 weeks using cv. Magnus. In our

experiment the DM yield of the crop continued to increase in

both years throughout the whole growth cycle. Sheldrick

et al. (1995) observed that delaying harvesting beyond the

flat pod stage resulted in a limited increase in DM yield

because of the senescence of the lower leaves and stems.

This difference can be partially explained by the better

standing ability of the semi-leafless pea lines than the leafed

lines, which leads to a delay of or prevents lodging of the

crop. Together with the higher DM yield, a more mature

plant can also have a higher DM content, possibly

eliminating the need to wilt the crop prior to harvest and,

thereby, potentially reducing the field losses (Fraser et al.,

2001). However, it is likely that allowing the crop to mature

to a late stage before harvesting may cause a detrimental

effect on the crude protein, fibre content and digestibility of

the crop (Van Soest, 1994). It is known that the

morphological development of the plant is the factor that

most affects the nutritive value of several grass and legume

forages (Van Soest, 1994). The large decline in the protein

and nutritive value of about 40% is attributed to the

interactive effects of the increase in fibre and lignin in the

tissues, which is more marked in stem tissue than in leaf

tissue, and to the different ratios between the plant tissue

components (Van Soest, 1994). This interactive effect is less

evident in crops where the grain contribution to the DM

yield is high (Salawu et al., 2001). In cereals (Kennelly and

Weinberg, 2003) and pulses (Panciera et al., 2003), utilized

as whole-crops, grain contribution to the total harvested DM

can reach 50% or more. In this experiment, the grain

contribution increased with advancing maturity and reached

50 and 65% after 92 and 112 days from sowing for 2001 and

2002, respectively. Koivisto et al. (2003), in the UK

environment, observed that pods of grain-type cultivars

accounted for 25% of the total mass of the plant at 80 days

after sowing. At a comparable harvesting date we observed

similar values with pods accounting for 26 and 35% of the

total plant mass, for the two experimental years.

The crop yielded from 0.9 to 1.3 Mg ha�1 of protein from

the beginning to the end of pod filling (from 10 to 14 weeks

after sowing) when harvested for silage purposes. These

values are slightly higher than those observed by Mustafa

and Seguin (2004) who harvested around 0.8 Mg ha�1 of

protein in a whole-crop pea at 10 weeks from seeding (pod

filling stage).

The NDF of the whole crop increased over the growth

cycle because, as the plant grows, the need for structural

tissue increases, and the NDF of the straw increased from

400 to more than 600 g kg�1 DM. The ADF, ADL and the

nutritive value of the whole crop pea expressed as GE, OMD

and NEL were constant over the whole growth cycle. This

can be explained by a decrease in the digestibility of the pea

straw with advancing maturity which is balanced by an

increase in grain proportion. These results are in agreement

with Mustafa and Seguin (2004) and Salawu et al. (2001),

who found that the in vitro OMD in the DM of pea/wheat bi-

crops did not appear to be significantly influenced by the

stage of maturity at harvesting. Fraser et al. (2005) also

observed no drop in digestibility for lupin (Lupinus albus)

silages harvested at four different stages of growth. Similar

results have been reported for whole maize silage where in

vitro DM digestibility was almost constant from late

flowering till advanced dough stage, due to the increase

in grain proportion (Johnson et al., 1999), while, in contrast,

Crovetto et al. (1998) observed a decrease in the in vivo

digestibility of whole-crop wheat silage and in the net

energy for lactation with advancing stage of maturity from

boot stage onwards.

In this experiment pea seeds contained an average CP of

243 g kg�1 DM that remained almost constant for the whole

growth cycle. Daveby et al. (1993) observed the same

pattern for three Swedish pea cultivars. Analyses of 1100

samples compiled over 4 years from throughout western

Canada confirmed a feed pea CP level of 239 g kg�1 DM

(Fleury, 2004). The WSC content was higher in the earlier

stages of seed development and rapidly decreased after

900 8C of GDD, corresponding to the advanced pod fill, as a

consequence of starch synthesis in the seed. Haeder (1989)

reported that synthesis of amylose and amylopectin, the two

main components of starch, increased rapidly after the first

third of seed DM is produced. The starch values of pea seeds

at harvest averaged 556 g kg�1 DM. This is higher than the

average starch values of 453 g kg�1 DM (Cerioli et al.,

1998) and 501 g kg�1 DM (Grosjean et al., 1999) measured

in extensive European surveys.

Pea straw could be a good feed alternative in beef diets,

due to its higher feed value than wheat or barley straw

(Cherriere, 2001). Pea straw has been reported to contain, on

average, 64 g kg�1 DM of CP, 695 g kg�1 DM of NDF,

G. Borreani et al. / Field Crops Research 100 (2007) 1–98

while at grain maturity we found higher value for CP and

lower values of NDF. Alternatively the straws could be

incorporated into the soil, and could contribute from 23 to

70 kg N ha�1 for the subsequent crop.

5. Conclusions

Semi-leafless grain peas seeded at the end of winter and

harvested from the middle of May to the end of June can give

high yields, providing good quality forage for ruminants and

may improve the self-sufficiency of dairy farms, in terms of

home-grown protein forages. The high DM yields,

associated with a low NDF content and a high OM

digestibility, suggest that whole crop peas should be

harvested and ensiled from the advanced pod filling stage

onwards, since semi-leafless grain peas did not show a

decline in the quality of forage with maturity.

Acknowledgements

The authors wish to thank Mario Gilardi and Mauro Gilli

(Dipartimento di Agronomia, Selvicoltura e Gestione del

Territorio) for the technical assistance in the field. Financial

support for this work was provided by the Consiglio

Nazionale delle Ricerche and by the MURST Funding

Program ‘‘60%’’. All the authors contributed equally to the

work described in this paper.

References

Adesogan, A.T., Salawu, M.B., Williams, S.P., Fisher, W.J., Dewhurst, R.J.,

2004. Reducing concentrate supplementation in dairy cow diets while

maintaining milk production with pea–wheat intercrops. J. Dairy Sci.

87, 3398–3406.

Aman, P., Graham, H., 1987. Whole-crop peas. I. Changes in botanical and

chemical composition and rumen in vitro degradability during matura-

tion. Anim. Feed Sci. Technol. 17, 15–31.

Andrieu, J., Demarquilly, C., 1987. Valeur nutritive des fourrages: tables et

prevision. In: Alimentation des ruminantes: revision des systemes et des

tables de l’INRA. Bull. Technol. 70, 61–73.

Battini, F., Ligabue, M., Marmo, N., 2001. Peas and faba beans for proteins,

alternatives for soybeans and protein flour. L’Inf. Agrario. 57 (14), 61–

65.

Borreani, G., Peiretti, P.G., Tabacco, E., 2003. Evolution of yield and quality

of sainfoin (Onobrychis viciifolia Scop.) in the spring growth cycle.

Agronomie 23, 193–201.

Børsting, C., Weisbjerg, M., 2002. Effects of whole crop pea silage and

grass silage on performance of dairy cows. In: Durand, J.L., Emile,

J.C., Huyghe, C., Lemarie, G. (Eds.), Quality Forages, Animal Pro-

ducts and Landscapes. Proceedings of the 19th General Meeting of

European Grassland Federation, La Rochelle, France, pp. 184–185.

Bourgeois, G., Jenni, S., Laurence, H., Tremblay, N., 2000. Improving the

prediction of processing pea maturity based on the growing-degree day

approach. HortSci 35, 611–614.

Cerioli, C., Fiorentini, L., Prandini, A., Piva, G., 1998. Antinutritional

factors and nutritive value of different cultivars of pea, chickpea and

fababean. In: Jansman, A.J.M., et al. (Eds.), Recent Advances of

Research in Antinutritional Factors in Legume Seeds and Rapeseed.

Proceedings of The Third International Workshop, Wageningen, The

Netherlands, pp. 43–46.

Cherriere, K., 2001. Pois, lupin et feveroles: des graines faciles a utiliser

pour nourrir porcs, volailles et ruminants. Perspect. Agric. 266, 26–29.

Cousin, R., 1997. Peas (Pisum sativum L.). Field Crop Res. 53, 111–130.

Crovetto, G.M., Galassi, G., Rapetti, L., Sandrucci, A., Tamburini, A., 1998.

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

silage. Livest. Prod. Sci. 55, 21–32.

Daveby, Y.D., Abrahamsson, M., Aman, P., 1993. Changes in chemical

composition during development of three different types of peas. J. Sci.

Food Agric. 63, 21–28.

Draper, N.R., Smith, H., 1998. Applied Regression Analysis, 3rd ed. John

Wiley & Sons, New York.

Faulkner, J.S., 1985. A comparison of faba beans and peas as whole-crop

forages. Grass Forage Sci. 40, 161–169.

Fick, G.W., Wilkens, P.W., Cherney, J.H., 1994. Modeling forage quality

changes in the growing crop. In: Fahey, G.C., Collins, M., Mertens,

D.R., Moser, L.E. (Eds.), Forage Quality, Evaluation and Utilization.

ASA-CSSA-SSSA Publishers, Madison, WI, pp. 757–795.

Fleury, M.D., 2004. Research summaries: peas in livestock diets [Online].

Available at http://www.infoharvest.ca/pcd/summaries/part007.html

(verified 12 Oct. 2005).

Fraser, M.D., Fychan, R., Jones, R., 2001. The effect of harvest date and

inoculation on the yield, fermentation characteristics and feeding

value of forage pea and field bean silages. Grass Forage Sci. 56,

218–230.

Fraser, M.D., Fychan, R., Jones, R., 2005. The effect of harvest date and

inoculation on the yield, fermentation characteristics of two varieties of

white lupin (Lupinus albus) when ensiled as a whole crop. Anim. Feed

Sci. Technol. 119, 307–322.

Goldman, A., Genizi, A., Yulzari, A., Seligman, N.G., 1987. Improving the

reliability of the two-stage in vitro assay for ruminant feed digestibility

by calibration against in vivo data from wide range of sources. Anim.

Feed Sci. Technol. 18, 233–245.

Grosjean, F., Barrier-Guillot, B., Bastianelli, D., Rudeaux, F., Bourdillon,

A., Peyronnet, C., 1999. Feeding value of three categories of pea (Pisum

sativum, L.) for poultry. Anim. Sci. 69, 591–599.

Haeder, H.E., 1989. Starch and amylose synthesis in seeds of garden and

field peas [Starke- und Amylosesynthese in Samen von Mark- und

Futtererbsen]. J. Agron. Crop Sci. 163, 217–224.

Johnson, L., Harrison, J.H., Hunt, C., Shinners, K., Doggett, C.G., Sapienza,

D., 1999. Nutritive value of corn silage as affected by maturity and

mechanical processing: a contemporary review. J. Dairy Sci. 82, 2813–

2825.

Kennelly, J.J., Weinberg, Z.G., 2003. Small grain silage. In: Buxton, D.R.,

Muck, R.E., Harrison, J.H. (Eds.), Silage Science and Technology.

ASA-CSSA-SSSA Publishers, Madison, WI, pp. 749–779.

Koivisto, J.M., Benjamin, L.R., Lane, G.P.F., Davies, W.P., 2003. Forage

potential of semi-leafless grain peas. Grass Forage Sci. 58, 220–223.

McMaster, G.S., Wilhelm, W.W., 1997. Growing degree-days: one equa-

tion, two interpretations. Agric. For. Meteorol. 87, 291–300.

Mikkelsen, S.A., 1981. Predicting the date of harvest of vining peas by

means of growing-degree-days models. Acta Hort. (ISHS) 122, 211–

221.

Marten, G.C., Buxton, D.R., Barnes, R.F., 1988. Feeding value (forage

quality). In: Hanson, A.A., Barnes, D.K., Hill, R.R. (Eds.), Alfalfa and

Alfalfa Improvement. ASA-CSSA-SSSA Publishers, Madison, WI, pp.

463–491.

Mustafa, A.F., Christensen, D.A., McKinnon, J.J., 2000. Effects of pea,

barley, and alfalfa silage on ruminal nutrient degradability and perfor-

mance of dairy cows. J. Dairy Sci. 83, 2859–2865.

Mustafa, A.F., Seguin, P., 2004. Chemical composition and in-vitro digest-

ibility of whole-crop pea and pea-cereal mixture silages grown in South-

western Quebec. J. Agron. Crop Sci. 190, 416–421.

Mustafa, A.F., Seguin, P., Ouellet, D., Adelye, I., 2002. Effects of cultivars

on ensiling characteristics, chemical composition, and ruminal degrad-

ability of pea silage. J. Dairy Sci. 85, 3411–3419.

G. Borreani et al. / Field Crops Research 100 (2007) 1–9 9

Nelson, C.J., Moser, L.E., 1994. Plant factors affecting forage quality. In:

Fahey, G.C., Collins, M., Mertens, D.R., Moser, L.E. (Eds.), Forage

Quality, Evaluation and Utilization. ASA-CSSA-SSSA Publishers,

Madison, WI, pp. 115–154.

Panciera, M.T., Kunkle, W.E., Fransen, S.C., 2003. Minor silage crops. In:

Buxton, D.R., Muck, R.E., Harrison, J.H. (Eds.), Silage Science and

Technology. ASA-CSSA-SSSA Publishers, Madison, WI, pp. 781–823.

Robertson, J.B., Van Soest, P.J., 1981. The detergent system of analysis and

its application to human foods. In: James, W.P.T., Theander, O. (Eds.),

The Analysis of Dietary Fibre in Food. Marcel Dekker, N.Y. and Basel,

pp. 123–158.

Rong, L., Volenec, J.J., Joern, B.C., Cunningham, S.M., 1996. Seasonal

changes in nonstructural carbohydrates, protein, and macronutrient in

roots of alfalfa, red clover, sweetclover, and birdsfoot trefoil. Crop Sci.

36, 617–623.

Salawu, M.B., Adesogan, A.T., Weston, C.N., Williams, S.P., 2001. Dry

matter yield and nutritive value of pea/wheat bi-crops differing in

maturity at harvest, pea to wheat ratio and pea variety. Anim. Feed

Sci. Technol. 94, 77–87.

Sheldrick, R.D., Newman, G., Roberts, D.J., 1995. Legumes for Milk and

Meat, 2nd ed. Chalcombe Publ., Canterbury, UK.

Tilley, J.M.A., Terry, R.A., 1963. A two-stage technique for the in vitro

digestion of forage crops. J. British Grassl. Soc. 18, 104–111.

Trevino, J., Centeno, C., Caballero, R., 1987. The chemical composition of

pea plant parts as related to harvesting date. Anim. Feed Sci. Technol.

16, 305–309.

Uzun, A., Bilgili, U., Sincik, M., Filya, I., Acikgoz, E., 2005. Yield and

quality of forage type pea lines of contrasting leaf types. Eur. J. Agron.

22, 85–94.

Van Soest, P.J., 1994. Nutritional Ecology of the Ruminant, 2nd Ed. Cornell

University Press, Ithaca, New York.

Wilkins, R.J., Jones, R., 2000. Alternative home-grown protein sources

for ruminants in the United Kingdom. Anim. Feed Sci. Tech. 85,

23–32.