Directory UMM :Data Elmu:jurnal:A:Animal Feed Science and Technology:Vol81.Issue3-4.Oct1999:

Animal Feed Science and Technology
81 (1999) 249±264

Use of lentil screenings in the diets of early weaned
lambs and ewes in the second trimester of pregnancy
K. Stanforda,*, G.L. Wallinsa, B.M. Leesb, H.-H. MuÈndelc
a

Alberta Agriculture, Food and Rural Development, Agriculture Centre, Bag 3014, Lethbridge, Alberta,
Canada T1J 4C7
b
Westco, Broxburn Agro Centre, RR 8-32-26 Lethbridge, Alberta, Canada T1J 4P4
c
Agriculture and Agri-Food Canada, Research Centre, Box 3000, Lethbridge, Alberta, Canada T1J 4B1
Received 28 December 1998; received in revised form 7 May 1999; accepted 15 June 1999

Abstract
Commercial lentil screenings (LS) were substituted for barley grain and canola meal, and the
resulting experimental diets (0, 12.5, 25 and 33% LS; 17±18% CP dry matter) were evaluated in situ and
in digestibility and feedlot studies using Romanov  Suffolk lambs. Mature Suffolk, Dorset and
Rambouillet ewes were used to evaluate LS or whole barley as protein/energy supplements for ewes in

mid-gestation receiving barley silage diets. Lentil screenings included 53.4% lentils, 10.6% weed seeds,
8.27% chaff and dust, with the remainder being a mixture of field peas, barley, wheat and canola. For the
lamb trial, the control diet consisted of 62% barley, 12.5% canola meal and 20% alfalfa (as fed), while
for the ewe study, the control diet consisted of barley silage with a salt-mineral supplement. Comparing
dietary constituents in situ, the rates of protein and dry matter (DM) disappearance were 5±6-fold lower
(p < 0.05) and effective ruminal degradability of protein (EDCP) was also lowest (p < 0.05) for LS as
compared to alfalfa or barley. Digestibilities of DM, organic matter (OM) and neutral detergent fibre
(NDF) as well as N retention (% of N intake) linearly decreased (p < 0.001) with increasing dietary LS.
In the lamb feeding trial, average daily gain (ADG; p < 0.01), feed intake (p < 0.01) and feed conversion
efficiency (p < 0.05) were all linearly reduced with increasing dietary LS, although such reductions
were not significant for ewe lambs. Reduced lamb performance with LS was likely related to antinutritional factors and the reduced digestibility of LS. Valuing LS at 50% the cost of barley,
incorporation of up to 25% LS in feeder lamb diets would be cost effective. In the ewe feeding study,
although weight gains over the 50 days of feeding were highest (p < 0.05) in barley-supplemented and
LS-supplemented as compared to control ewes, LS-supplemented ewes had fewer (p < 0.05) lambs born
per ewe and reduced (p < 0.05) weight of lambs weaned breeding per ewe as compared to control ewes.
Consequently, supplementation of barley silage diets with LS may not be beneficial for ewes in midgestation. # 1999 Elsevier Science B.V. All rights reserved.
Keywords: Lentil; Screenings; Feeding value; Digestibility; Sheep
*

Corresponding author. Tel.: +403-381-5150; fax: +403-382-4526

E-mail address: stanford@em.agr.ca (K. Stanford)
0377-8401/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 9 9 ) 0 0 0 9 2 - 9

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K. Stanford et al. / Animal Feed Science and Technology 81 (1999) 249±264

1. Introduction
Lentils (Lens culinaris) have been recognized as one of the most complete and
cheapest sources of vegetable protein for humans (Vidal-Valverde et al., 1994). Lentil
seed is low in crude fibre (range 1.4±5.9%; Savage, 1988) and contains an average of
25% protein, 56% carbohydrate and 1% fat (Urbano et al., 1995). Agronomically, lentils
are able to tolerate frost after emergence and resistant to high temperatures and drought
(Savage, 1988). Due to these aforementioned factors and as a result of the promotion of
lentil cultivation by the International Centre for Agricultural Research in Dry Areas
(ICARDA), world production of lentils increased by 72% during the 1980s (Frias et al.,
1996). In Canada, lentil production has also expanded in the last 30 years. Although
lentils were not commercially cultivated in Canada prior to 1969, Canada is now, along
with Turkey, the world's leading exporter of lentils (Anonymous, 1997).

Increased cultivation has led to greater availability of non-food-grade lentils for use in
livestock diets. Lentils affected with ascochyta blight (Ascochyta lentis) and/or frostdamaged have been previously evaluated for use in pig diets (Bell and Keith, 1986;
Castell and Cliplef, 1988). Lentil screenings are another source of lentils for livestock
feed. Screenings are a byproduct of seed cleaning and consist of a mixture of the crop in
question, cereal grains, weed seeds, chaff and dust (Darroch et al., 1990). Screenings are
attractive for use in ruminant diets (McAllister et al., 1999) due to their low cost, which
for lentil screenings in western Canada averages half that of feed barley.
In the raw, unprocessed form, all grain legumes contain a variety of anti-nutritional
factors (Paduano et al., 1995). Some of the weed seeds present in screenings may also
contain anti-nutritional factors (Darroch et al., 1990). Consequently, ruminant diets would
be the major use for lentil screenings due to the ability of rumen microbes to adapt to
(Birnbreier and Hilliger, 1993) or partially detoxify (Tukur et al., 1993) some factors such
as alkaloids which would impair the performance of monogastrics. Although the use of
lentil screenings in ruminant diets has not previously been addressed, ewes in the Middle
East commonly receive 20% of their winter diet as lentil straw which includes broken
branches, pod walls and leaflets (Erskine et al., 1990). In order to further study the use of
lentil byproducts in sheep diets, the present series of experiments examined the in situ
DM and CP degradation kinetics of lentil screenings, the apparent digestibility of lentil
screenings, substitution of lentil screenings for barley and canola meal in the diets of
early-weaned feeder lambs and the use of lentil screenings as a protein/energy

supplement for ewes in mid-gestation.

2. Materials and methods
2.1. Diets
A composite 4 kg sample of screenings from the Laird variety of lentils (LS) was
collected over an eight week period from a commercial lentil contractor/seed cleaning
plant in Lethbridge, AB and a 250 g subsample was manually sieved to determine
botanical composition (Table 1). Upon arrival at the Lethbridge Research Centre, the LS

K. Stanford et al. / Animal Feed Science and Technology 81 (1999) 249±264

251

Table 1
Botanical composition by weight and proximate analysis of lentil screenings used in the present study
Botanical composition

Proximate analysis (% by weight)

Cultivated crops

Lentils, whole
Lentils, broken
Peas, broken
Barley
Wheat
Canola
Total

37.18
16.66
5.80
4.70
8.89
7.77
81.00

Weed seeds
Stinkweed (Thlaspi arvense)
Wild oats (Avenua fatua)
Canary grass (Phalaris arundinacea)

Lamb's quarters (Chenopodium album)
Wild buckwheat (Polygonum convulvulus)
Dandelion (Taraxacum officinales)
Unidentified weeds
Total

3.97
3.27
1.76
0.51
0.60
0.05
0.40
10.56

Other
Chaff and dust
a

dry matter (%)

organic matter (DM basis)
crude protein (DM basis)
neutral detergent fibre (DM basis)
acid detergent fibre (DM basis)
tannina (DM basis)

90.4
89.3
22.7
29.4
16.1
1.4

8.46

Tannin expressed as catechin equivalents.

were hammermilled to pass through a 3 mm screen and subjected to proximate analysis
(Table 1) prior to incorporation into four completely pelleted experimental diets for the
lamb study (Table 2). For the lamb study, LS were incorporated at rates of 0% (control),

12.5%, 25% and 33% (dry matter basis), replacing barley and canola meal. Diets for
pregnant ewes consisted of barley silage (Table 3) top dressed with either whole barley,
LS, or not supplemented (control). Ewes were fed the experimental diets for 50 days,
after which all ewes received loose alfalfa hay supplemented with whole barley for the
last trimester of pregnancy and during lactation.
2.2. Experiment 1: in situ disappearance
For two weeks prior to, and during the two days of the in situ study, two ruminally
cannulated Jersey steers (470 kg) were offered a diet consisting of 50% alfalfa : timothy
cubes (70 : 30; 13% CP) and 50% of the 33% LS experimental diet. Dried, pre-weighed
nylon bags (10 cm  11 cm; 53 mm pore size) containing 3.0 g of each dietary constituent
(rolled barley, pelleted alfalfa or LS) or pelleted diets (20% LS or 33% LS) were placed
in the rumen of each steer. Three bags of each samples type were removed from each
steer after 2, 4, 8, 12, 24, 48 and 72 h of ruminal incubation. Dry matter disappearance
not attributable to microbial digestion was estimated by incubating bags in water at 378C
for 2 min. Bag washing and calculation of DM disappearance were performed as
described by McAllister et al. (1990). Residues from the triplicate bags were pooled for N
analysis.

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K. Stanford et al. / Animal Feed Science and Technology 81 (1999) 249±264

Table 2
Ingredients (as fed) and composition (DM basis) of experimental diets for lambs
Lentil screenings content of diet (%)
0 (Control)

12.5

25

33

625
125
200
0
10
8
13

10
5
4
0.25
0.13

560
65
200
125
10
8
13
10
5
4
0.25
0.13

500

0
200
250
10
8
13
10
5
4
0.25
0.13

420
0
200
330
10
8
13
10
5
4
0.25
0.13

89.64
90.18
18.71
34.52
17.27
1.12

89.56
90.25
17.58
36.44
18.41
0.88

89.12
90.81
17.07
31.84
17.83
0.86

89.91
89.41
18.04
29.77
17.52
0.94

ÿ1

Ingredients (kg t )
Barley grain
Canola meal
Alfalfa, suncured
Lentil screenings
Molasses, beet
Canola oil
Sheep minerala
Calcium carbonate
Maxi-Pelb
Dicalcium phosphate
Vitamin A, D, Ec
Deccoxd
Analysis
Dry matter (%)
Organic matter (%, DM basis)
Crude protein (%, DM basis)
Neutral detergent fibre (%, DM basis)
Acid detergent fibre (%, DM basis)
Acid detergent insoluble N (%, DM basis)
a

Containing: 93.1% NaCl, 1.25% Mg, 0.9% Zn, 0.94% Mn, 0.13% Cu, 0.003% Se, 1.25% S, 1.25% K, 1.25%

Fe.

b
c
d

Feed pellet binder (Mountain Minerals, Lethbridge, AB).
Containing 10 000 IU gÿ1 Vitamin A, 1250 IU gÿ1 Vitamin D, and 10 IU gÿ1 Vitamin E.
Containing 60 g kgÿ1 decoquinate (RhoÃne-Poulenc Canada, Mississauga, ON).

Digestion kinetics of DM and CP were determined without correction for microbial
protein using the equation of érskov and McDonald (1979):
p ˆ a ‡ b…1ÿeÿct †

(1)

where p is the proportion of DM disappearance at time t (%), a the soluble fraction, b the
slowly digestible fraction, c the fractional rate of disappearance of b and t the duration of
Table 3
Composition (DM basis) of ewe experimental dietsa

Analysis
Dry matter (%)
Crude protein (%, DM basis)
Neutral detergent fibre (%, DM basis)
Acid detergent fibre (%, DM basis)
a
b

Barley silageb

Barley grain

Lentil screenings

31.5
11.8
56.5
33.4

90.4
12.6
22.7
16.2

91.0
22.4
30.2
16.4

Also included free choice 2 : 1 (Ca : P) sheep mineral and cobalt-iodized NaCl.
pH 4.2.

K. Stanford et al. / Animal Feed Science and Technology 81 (1999) 249±264

253

ruminal incubation (h), with the constraint that a + b  1. The constraints a, b, and c were
calculated using the NLIN procedure of the SAS Institute Inc. (1993). Effective rumen
degradability of CP (EDCP) was estimated using the equation of érskov and McDonald
(1979):
EDCP ˆ a ‡

bc
k‡c

(2)

with an estimated solid outflow from the rumen (k) of 5% hÿ1 (Windschitl and Stern,
1988). Means were compared using the LSMEAN option of SAS (SAS Institute Inc.,
1993).
2.3. Experiment 2: apparent digestibility
In a replicated 3  3 Latin square with three 21-day periods, six Romanov±Suffolk ram
lambs (initial weight 25.0  0.1 kg) were used to evaluate voluntary feed intake and
digestibility of the control, 12.5% and 33% LS diets. For the first 14 days of each period,
lambs were individually penned. Orts were removed and weighed on a daily basis, and
10% more feed offered each day than was consumed the previous day. Ad libitum intake
was then calculated over five days and the lambs fed at 95% ad libitum for the last nine
days of the period. During the last seven days of each period, lambs were moved to
metabolism crates for daily collections of faeces and urine. Acid (45 ml of 8N H2SO4)
was added each morning to the urine collection jugs to prevent volatization of ammonia
from the urine. Faeces and urine were subsampled daily (10%), composited over each
period and stored at ÿ308C until analysed.
2.4. Experiment 3: lamb feeding trial
Forty-seven Romanov  Suffolk lambs were used to evaluate the four experimental
diets (Table 2) in an individual feeding trial. The lambs (initial weight 26.5  0.2 kg,
initial age 62  5 days) were blocked by sex and liveweight and allocated to pens using
randomized block design. Access to water and pelleted diets was provided on an ad
libitum basis throughout the study. Once daily, lambs were fed 5% more than their
estimated consumption for the previous day. Orts were collected and weighed weekly.
Lambs were weighed weekly and shipped for slaughter after reaching 45 kg.
2.5. Experiment 4: ewe feeding trial
Fifty days after being exposed to rams, 93 mature Dorset, Suffolk and Rambouillet
ewes (age 2±6 year) were weighed, condition scored on a five-point scale where
1 = emaciated and 5 = obese (Scheer, 1987), blocked by breed, weight and age and
allocated to group pens (n = 6) using a randomized block design. All ewes received a base
diet of 7 kg per head barley silage (Table 3). One-third of the ewes (2 pens) received
only the base diet, another third received the base diet topdressed with 250 g per head per
day LS, while the remaining one-third received the base diet topdressed with 250 g per
head day whole barley. Throughout the study, water and salt/mineral supplement were

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K. Stanford et al. / Animal Feed Science and Technology 81 (1999) 249±264

available ad libitum to the ewes. Ewes were fed once daily, with sufficient bunk space to
allow each ewe immediate access to the fresh feed. Ewes received the experimental diets
for 50 days and were then weighed and condition scored. Fifty days after the end of the
feeding period, the ewes began lambing. Lambing data (proportion of ewes lambing,
prolificacy and lamb birthweight) and lamb weaning weights at age 60 days were
recorded.
2.6. Chemical analyses
Silage samples were freeze dried in a Virtris 25 XL Sentry (Virtris, Gardiner NY)
before subsequent analysis. The remaining feed and faecal samples were dried at 1058C
for 24 h to determine DM and ashed in a muffle furnace at 5008C for 5 h to determine
OM. Excluding silage samples, faeces and feed were dried at 558C for 48 h before
analyses for NDF and N. Faeces and feed were ground through a 1 mm screen for
analysis of NDF and ground for 3 min in a Wig-L-Bug1 Amalgamator (Crescent Dental,
Lyons IL) prior to N analysis in a Carlo±Erba1 NA 1500 Carbon±Nitrogen elemental
analyser (Carlo±Erba Srumentazione, Rodano, Milan, Italy). The procedure of Van Soest
et al. (1991) was used to determine NDF, but was modified by adding a-amylase to feed
samples to solubilize starch and facilitate filtering. Tannin content of lentil screenings
was determined by use of the vanillin±HCL method and expressed as catechin equivalents
(Price et al., 1978).
2.7. Statistical analyses
Data were analysed using the regression (REG) and general linear model (GLM)
procedures and means compared using the least-squares mean (LSMEAN) option of SAS
(SAS Institute Inc., 1993). For the digestibility trial, the model included lamb, diet, period
and period  diet interaction. Data for the individual feeding experiment were analysed
with sex, diet, and diet  sex interaction included in the model with initial weight as a
covariate. Breed, age, diet and two-way interactions were included in the model for
analysis of the ewe feeding study after pen effects were found to be non-significant.

3. Results
3.1. Experiment 1: in situ disappearance
Lentil screenings were resistant to protein and DM disappearance in the rumen
compared to alfalfa pellets, rolled barley or pelleted diets containing 25% or 33% LS
(Table 4). Lag time was 7.4 h before onset of protein digestion in LS, while digestion was
immediate for other dietary constituents and complete diets. The soluble DM and protein
fractions of LS were reduced 3±4-fold (p < 0.05) compared to all other dietary
constituents or complete diets evaluated. The reduced soluble fractions of LS were
mirrored by slowly degradable fractions of protein and DM that were higher (p < 0.05)
for LS than those of alfalfa, rolled barley, or either of the complete diets. Likewise, the

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K. Stanford et al. / Animal Feed Science and Technology 81 (1999) 249±264
Table 4
In situ degradation kinetics of DM and CP in dietary constituents and complete diets in steersa
Dietary constitutentsg
alfalfac

barleyd

Complete dietsb,g
LSe

SEMf

level of screenings (DM)
25%

33%

Slowly degradable fraction(%)
Protein
48.27 a
DM
47.51 a

70.60 b
70.66 b

95.35 c
95.65 c

52.38 ab
52.00 ab

49.18 ab
48.85 ab

4.37
7.11

Soluble fraction(%)
Protein
23.59 b
DM
22.40 b

20.64 b
19.52 b

4.02 a
4.00 a

25.51 b
24.93 b

21.65 b
21.48 b

1.67
4.29

Rate of disappearance(% hÿ1)
Protein
7.01 b
DM
7.90 b

21.2 d
18.0 c

1.19 a
1.20 a

10.04 bc
10.25 bc

13.82 c
13.55 bc

1.43
2.83

22.01 a

60.52 c

57.70 c

4.23

Effective ruminal degradability (%)
Protein
35.70 b
77.40 d
a

Lag time 7.4 h for protein disappearance in LS, 0 h for other dietary constituents and complete diets.
Control diet contained (as fed): 75% barley + 20% alfalfa.
c
Pelleted alfalfa.
d
Rolled barley grain.
e
Lentil screenings.
f
Standard error of the mean.
g
Within a row, means followed by different letters differ (p < 0.05).
b

rates of protein and DM disappearance were reduced 5±6-fold (p < 0.05) for LS compared
to those of alfalfa, the dietary constituent with the next lowest rates of protein and DM
disappearance. Effective ruminal degradability of protein (EDCP) was also lowest
(p < 0.05) for LS compared to the other dietary constituents or complete diets.
The low rate/extent of all measures of LS, DM and CP disappearance was not apparent
for the complete diets evaluated (25% and 33% LS, respectively). Generally, the in situ
degradation kinetics of DM and CP in the complete diets were intermediate to those of
rolled barley and pelleted alfalfa. The slowly degradable and soluble fractions of CP and
DM for both complete diets did not differ from those of pelleted alfalfa or rolled barley.
For both complete diets, rate of DM disappearance was intermediate to that of alfalfa and
rolled barley. Rate of protein disappearance was highest in rolled barley (p < 0.05),
followed by the 33% LS diet which in turn had a higher rate of protein disappearance than
alfalfa (p < 0.05), with the 25% LS diet equal in rate of protein disappearance to alfalfa
and the 33% LS diet . Effective ruminal degradability of protein was highest for rolled
barley (p < 0.05) followed by both complete diets which had higher EDCPs than alfalfa
(p < 0.05).
3.2. Experiment 2: apparent digestibility
The ram lambs used in the digestibility trial found LS to be palatable as DM intake
linearly increased (p < 0.05) with increasing LS content of the diets (Table 5). However,

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K. Stanford et al. / Animal Feed Science and Technology 81 (1999) 249±264

Table 5
Effect of level of lentil screenings in diets on nutrient digestion and N metabolism in lambs
SEMa

Level of lentil screenings
in diet
0% (control) 12.5%
ÿ1

DM Intake (g day )
Digestibility (%)
Dry matter
Organic matter
Acid detergent fibre
Neutral detergent fibre
N Intake (g per day)
Urinary N (g per day)
N digested (%)
N digested (g per day)
N retained (g per day)
N retained (% of N intake)
N retained (% of N digested)

Effect of level of
screeningsb

33%

linear

quadratic

*

NS

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

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

1330.5

1478.0

1523.9

57.9

68.3
69.8
26.0
42.2
39.7
9.7
70.3
27.1
5.5
14.0
20.4

68.2
69.7
31.7
46.4
41.5
8.7
69.3
28.5
7.0
17.0
24.8

63.2
64.9
23.8
26.9
43.9
12.0
68.6
27.8
1.9
4.6
7.3

0.7
0.6
2.0
1.2
1.7
0.6
1.1
1.3
0.7
1.7
2.1

a

Standard error of the mean.
Control diet contained (as fed): 62.5% barley grain + 12.5% canola meal + 20% alfalfa.
*
Significant at p < 0.05; ** Significant at p < 0.01; *** Significant at p < 0.001; NS: Not significant,
(p > 0.05).
b

digestibilities of DM, organic matter (OM) and neutral detergent fibre (NDF) linearly
decreased (p < 0.001) with increasing dietary LS. Significant quadratic effects for DM
(p < 0.05), OM (p < 0.05) , acid detergent fibre (ADF; p < 0.05) and NDF (p < 0.001)
digestibilities with level of dietary LS, indicated that reductions in digestibilities as
compared to those of control lambs were minor or non-existent with 12.5% dietary LS
and severe for lambs receiving the 33% LS diet.
Although N intake, urinary excretion of N and measures of N digestion were not
affected by the level of lentil screenings in the diet, N retention measures (g per day, % of
N intake and % of N digested) were all linearly reduced (p < 0.01, p < 0.001, p < 0.01,
respectively) with increasing dietary LS. Significant quadratic effects (p < 0.01) were
also evident for LS level on N retention. Generally, N retention measures were reduced at
least twofold for lambs receiving the 33% LS diet as compared to control lambs, while N
retention of lambs receiving the 12.5% LS diet was moderately elevated as compared to
that of control lambs.
3.3. Experiment 3: lamb feeding trial
Average daily gain, feed intake and feed conversion efficiency were reduced for ewe
lambs as compared to ram lambs (Table 6). When all lambs in the study were considered,
initial weight and final weight did not vary according to the level of LS in the diet,
although average daily gain and feed intake linearly decreased (p < 0.01) with increasing
dietary LS and feed conversion (feed per gain) linearly increased with increasing dietary
LS. In contrast, when growth performance data were analysed by sex, level of dietary LS

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K. Stanford et al. / Animal Feed Science and Technology 81 (1999) 249±264
Table 6
Effect of level of lentil screenings in feedlot diets for lambs on growth performance
Parameters

Level of lentil screenings in diet (DM basis)

Effect of level
of screeningsa

0% (control)b 12.5%

25%

33%

SEMc

L

Number of lambs
Initial wt (kg)
Final wt (kg)
Average daily gain (g)
Feed intake (g DM per day)
Feed conversion (feed per gain)

11
27.0
44.1
347
1405
4.2

12
26.5
44.3
291
1377
4.8

12
26.1
43.3
291
1343
4.7

12
26.4
42.1
236
1172
5.1

±
0.2
1.3
17
48
0.2

±
NS
NS
***
**
**

Rams
Average daily gain (g)
Feed intake (g DM day)
Feed conversion (feed per gain)

427
1516
3.5

330
1421
4.3

317
1372
4.4

240
1074
4.7

21
75
0.2

**
**

Ewes
Average daily gain (g)
Feed intake (g DM per day)
Feed conversion (feed per gain)

268
1294
4.9

253
1333
5.4

264
1315
5.0

235
1269
5.5

21
62
0.2

NS
NS
NS

*

a

Linear effect, no quadratic effects were significant (p > 0.05).
Control diet contained 62.5% barley grain, 12.5% canola meal and 20% alfalfa.
c
Standard error of the mean.
*
Significant at p < 0.05; ** Significant at p < 0.01; *** Significant at p < 0.001; NS: Not significant
(p > 0.05).
b

did not affect any growth performance traits of ewe lambs. For ram lambs, the effects of
level of lentil screenings on growth performance traits were similar to the effects noted
for when both rams and ewes were considered.
3.4. Experiment 4: ewe feeding trial
Ewes in the three treatment groups did not differ in initial condition score, initial
weight or final weight (Table 7), although final condition score was higher (p < 0.05) for
ewes receiving supplemental barley than the control or LS-supplemented ewes. When
weight gain over the 50 days of the feeding study was considered, unsupplemented
control ewes gained an average of 100 g, while barley and LS-supplemented ewes had
higher (p < 0.05) gains of 1.84 and 2.04 kg, respectively.
The proportion of ewes lambing and lamb birthweight did not differ between the
treatment groups. Prolificacy, the number of lambs born ewe per lambing, was lower
(p < 0.05) in the LS-supplemented group than it was for the control- or barleysupplemented ewes. Lamb weaning weight at age 60 days was lower (p < 0.05) for the
barley-supplemented ewes than for the other two treatment groups. The weight of lambs
weaned ewe per breed was lower (p < 0.05) for LS-supplemented ewes as compared to
control ewes, while the equivalent measurement for barley-supplemented ewes was
intermediate to those of the control and LS-supplemented ewes.

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K. Stanford et al. / Animal Feed Science and Technology 81 (1999) 249±264

Table 7
Effects of supplementation in the second trimester of pregnancy with lentil screenings or barley grain on ewe
weight and condition score and subsequent lambing performancea
Barley silage
(control)

Silage + 150 g
barley grain

Silage + 150 g
lentil screenings

SEMb

Pregnancy ewe weight and condition
Number of ewes
Initial condition score
Final condition score
Initial weight (kg)
Final weight (kg)
Weight gain (kg)

31
3.3
3.2 a
90.3
91.3
0.1 a

31
3.4
3.4b
90.9
93.3
1.84 b

31
3.3
3.2 a
87.4
90.5
2.04 b

±
0.07
0.05
2.5
1.8
0.7

Lambing and weaning data
Proportion ewes lambing
Prolificacy (lambs born per ewe)
Lamb birthweight (kg)
Lamb weaning weight (kg)
Lamb weaned per ewe bred (kg)

95.8
1.9 b
4.9
22.1 b
32.6 b

90.6
2.0 b
4.7
20.4 a
28.4 ab

89.4
1.a
4.9
23.1 b
26.4 a

4.0
0.1
0.7
0.8
2.1

Treatment

a
b

Within a row, means followed by different letters differ (p < 0.05).
Standard error of the mean.

3.5. Costs of feeding lentil screenings
For the lamb feeding study, actual 1997 and 1998 feed costs kg per gain are shown in
Table 8, along with estimates for feed costs in 1999. Although costs for feed ingredients
fluctuate widely, using 1997 and 1998 costs and estimates for 1999, in all cases the leastcost feeder lamb diet contained 25% LS. For the ewe feeding study, costs of feeding LS
would have two components: (1) actual ewe feed costs during mid-pregnancy; (2) loss of
income from reduction in lamb crop compared to unsupplemented controls. Assuming a
market value of early-weaned feeder lambs of Can$ 2.00 per kg liveweight,
Table 8
Cost of gain estimates for lamb feedlot diets in which barley and canola meal are replaced with lentil screenings
(LS).
LS in diet
(%, as fed)

1997 cost of gaina
(Can$ kgÿ1)

1998 cost of gainb
(Can$ kgÿ1)

1999 cost of gainc
(Can$ kgÿ1)

0% (control)
12.5%
25%
33%
Predicted least-cost diet (% LS)

0.497
0.503
0.435
0.451
25

0.430
0.396
0.391
0.412
25

0.430
0.410
0.420
0.460
25

a
Based on actual values at the time of the study, fall 1997 where barley = Can$ 140/t, canola meal = Can$
235/t and lentil screenings = Can$ 90/t.
b
Based on actual values, fall 1998, where barley = Can$ 115/t, canola meal = Can$ 140/t and lentil
screenings = Can$ 75/t.
c
Assuming low-priced barley at Can$ 90/t, canola meal at Can$ 157/t and lentil screenings at Can$ 60/t.

K. Stanford et al. / Animal Feed Science and Technology 81 (1999) 249±264

259

supplementing ewes in mid-gestation with barley or LS would potentially result in lost
lamb income of Can$ 8.40 and Can$ 12.40 per ewe, respectively, and an additional feed
costs of approximately Can$ 2.00 and 1.00 per ewe compared to unsupplemented ewes.

4. Discussion
4.1. In situ disappearance
As 40% of LS consisted of lentil fragments, pea fragments, fine weed seeds, chaff
and dust (Table 1), LS were not ground before in situ incubations to prevent excessive
loss of DM from the bags. It was expected that the cereal grains and intact lentils present
within LS would have been sufficiently battered by the seed cleaning process, that they
along with the lentil and pea fragments would have been accessible to microbial
degradation. Microbial colonization of feed grains has been demonstrated (McAllister et
al., 1990; Wang et al., 1999) to proceed once the pericarp is broken. The barley used in
situ was whole, and only lightly rolled to break the pericarp. Similarly, the pericarp of an
estimated 80% of lentils in the LS used in situ was also broken. Although lentils had a
higher surface area and equivalent weight to barley kernels (data not shown), LS were
highly resistant to microbial attack. As microbial digestion of complete diets containing
LS, was not inhibited to the same extent as that of 100% LS, damage to the lentil pericarp
may not be enough to promote microbial colonization. Consequently, LS should be
hammer milled to a particle size of 3 mm or less, or ground to promote digestion by
rumen microbes.
In the present study, the most abundant weed seed (by weight) in LS was stinkweed
(Thlaspi arvense) which contains high levels of glucosinolates (7±8% on DM basis;
Beames et al., 1986). Glucosinolates are metabolized in the rumen to form isothiocyanate
which can lead to gastric upset, reduced palatability of feed, depressed growth, goitre and
anaemia (Cheeke, 1998). Blackshaw and Rode (1991) found stinkweed seed resistant to
digestion in the rumen, retaining 98% viability after 12 h rumen incubation. Other
constituents of LS which would be resistant to microbial digestion in situ would include
whole canola (Wang et al., 1997) and inorganic matter (dust and small stones).
In addition to effects of processing, the minor changes in soluble fractions of CP and
DM, rates of disappearance of CP and DM and EDCP values observed for complete diets
containing 20% or 33% LS as compared to 100% LS may also be due to a dilution of the
antinutritional/microbial digestion-resistant factors of LS. Unless a threshold level is
reached for an antinutritional factor, effects on microbial fermentation would likely be
minimal (Paduano et al., 1995), especially when exposure to the factor was of relatively
short (14 days) duration.
4.2. Apparent digestibility
Reduction in digestibilities of DM, OM and NDF with increasing dietary LS could be
partly attributed to the previously discussed anti-nutritional factors in LS and also to the
inherent indigestibility of some of the components of LS. Due to the low digestibility

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K. Stanford et al. / Animal Feed Science and Technology 81 (1999) 249±264

(43±46%) of lentil straw (Erskine et al., 1990), lentil chaff likely has a low digestibility.
The digestibility of many of the weed seeds present in LS is also likely low based on the
in situ study of Blackshaw and Rode (1991). The DM, OM and ADF digestibility values
reported by Tait et al. (1986) for sheep receiving 30% refuse screenings are in accord with
those of the present study for the 33% LS diet. The refuse screenings used in the study of
Tait et al. (1986) likely contained many of the weeds present in LS and had levels of
inorganic matter and ADF similar to those of LS.
In a study comparing N retention on diets consisting of legume seeds (pea, fenugreek,
faba bean, common vetch, lentil), sheep were in negative nitrogen balance for the lentil
diet, but retained 1.46±4.37 g N per day on non-lentil diets (Guada-Vallepuga, 1972).
Although no lambs in the present study had a negative nitrogen balance, N retention was
lowest for lambs receiving the 33% LS diet. The reduced N retention with increased
dietary LS was not due to elevated levels of acid detergent insoluble N (ADIN) in the LS,
as ADIN levels were comparable among all diets (Table 2). Bell and Keith (1986)
attributed a reduced digestibility of CP for pigs receiving lentil diets to possible
enzymatic trypsin inhibitors. As trypsin inhibitors are digested and rendered ineffective
by rumen microbes (Maynard et al., 1979), other factors must have caused the negative
nitrogen balance of the sheep in the study of Guada-Vallepuga (1972).
Lentils have been recognized (Bhatty et al., 1976; Savage, 1988) as having limiting
levels of sulfur-containing amino acids such as methionine and cysteine. Lentils also
contain significant amounts of tannins (0.27±0.40% expressed as catechin equivalents;
Davis, 1981) which are detoxified by methylation, further limiting the availability of
cysteine and methionine (Savage, 1988). Relative to pigs or cattle, sheep have a high
requirement for sulfur-containing amino acids, particularly cysteine, in order to support
wool growth (Russel, 1992). Consequently, N retention may be impaired in sheep
consuming a high proportion of lentils due to restricted availability of cysteine and
methionine. Lentil screenings in the present study had tannin concentrations of 1.4%
(expressed as catechin equivalents), higher than those reported by Davis (1981), but likely
due to differences in methodology between studies (Reed, 1995). Tannin concentrations
of 1.4% have been reported to reduce N digestion in sheep but would have to be increased
fourfold to elicit a similar reduction in fibre digestion (Min et al., 1998). Accordingly, the
reduced digestibility of NDF with increasing dietary LS is likely due to factors other than
tannins present in LS.
4.3. Lamb growth trial
The impaired N retention and lowered digestibilities of DM, OM and NDF with
increasing dietary LS for lambs were consistent with the linearly decreased ADG and
reduced feed conversion efficiency with increasing LS for individually-fed lambs on the
growth trial. One difference noted between the digestibility and growth trials was in feed
intake. Feed intake was linearly reduced with increasing dietary LS (p < 0.01) for lambs
on the growth trial, but increased with dietary LS on the digestibility trial. Dietary
preferences of sheep are known to be highly individual (Phy and Provenza, 1998) and the
six rams on the digestibility trial might have found LS more palatable than did the 47
lambs in the individual feeding study. Additionally, it has been established (Provenza,

K. Stanford et al. / Animal Feed Science and Technology 81 (1999) 249±264

261

1995) that variable lengths of time are required based on post-ingestive feedback in order
to set ruminant feed intake/preferences.
Although all diets in the individual feeding study had a CP content of 17% or greater
on a DM basis and CP content of the diets should have not been limiting according to
NRC recommendations (NRC, 1985) the CP available for rapidly growing ram lambs
may have been limited by the anti-nutritional/digestion-resistant factors in LS. In contrast
to ram lambs, the growth performance of ewe lambs was not affected by level of dietary
LS. Likely, the lower growth rate of ewes (251  21 g per day) compared to rams
(330  21 g per day) and consequently lower CP requirement of the ewe lambs were
responsible for the lack of effect of LS on ewe lamb growth performance.
4.4. Ewe feeding study
The higher weight gain of ewes supplemented during the 50-day feeding period with
barley grain or LS compared to control ewes would be expected due to the increased
density of energy and protein in barley grain and lentil screenings compared to 31.5%
DM barley silage. However, the reduction in prolificacy of lentil-supplemented ewes
compared to control ewes was not anticipated. The second trimester of pregnancy is the
period of maximum growth and development of the placenta (Mellor, 1983). Perhaps
anti-nutritional factors in the LS impaired the development of the placenta and led to
embryonic mortality in the LS-supplemented ewes. Another possible explanation may be
the inverse relationship established by Parr et al. (1993) between feed intake and plasma
progesterone concentration of pregnant ewes. Provided the nutritional requirements of the
ewes are met, additional protein or energy supplements in mid-pregnancy may be
detrimental to ewe prolificacy. Hatfield et al. (1998) found that ewes which had received
a low level (68 g per day protein or 136 g per day energy) of supplements in midpregnancy had reduced numbers of lambs born per ewe as compared to unsupplemented,
grazing ewes.
As ewes are able to supply more milk to a single than a twin (Peeters et al., 1992;
Ramsey et al., 1998), weaning weight was lower for lambs of barley as compared to LSsupplemented ewes. The trend toward both lower birthweights and marginally higher
prolificacy was likely responsible for the reduced lamb weaning weight of barleysupplemented as compared to unsupplemented ewes. Lower birthweight has a negative
impact on lamb survival (Schoenian and Burfening, 1990; Russell et al., 1992), which
could have reduced the weight of lambs weaned per ewe bred for the barleysupplemented as compared to the unsupplemented ewes.
Weight of lambs produced annually for each breeding ewe has been recognised as the
economic trait that is most important to commercial sheep enterprises (Ercanbrack and
Knight, 1998). Supplementing ewes in the second trimester of pregnancy with either
barley or LS did not improve lamb production per ewe, and in the case of LSsupplemented ewes, the weight of lambs weaned per ewe exposed was significantly lower
(p < 0.05) compared to unsupplemented ewes. Based on the results of this study, the
utility of protein and/or energy supplementation to adequately nourished ewes in the
second trimester of pregnancy is questionable. Although the cause of the reduced
prolificacy of ewes receiving LS in mid-gestation is unknown, LS of similar composition

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K. Stanford et al. / Animal Feed Science and Technology 81 (1999) 249±264

to that of the present study should not be used as a protein/energy supplement for ewes in
the second trimester of pregnancy receiving barley silage-based diets.

5. Conclusions
As with many byproduct feeds, lentil screenings vary in composition. Nutritional value
would be influenced by the level of weed seeds and other contaminants (dust, rocks,
insects) present in the LS. Lentil screenings similar in composition to those used in our
studies represent a valuable feed resource for early-weaned lambs, although for
maximum lamb performance, LS should not exceed 25% of the diet. In contrast,
supplementing barley silage diets of ewes in mid-pregnancy with LS was detrimental to
ewe productivity, while supplementing ewes with barley was not beneficial. Consequently, the use of protein or energy supplements during mid-pregnancy is questionable,
provided that the ewes enter a rising plane of nutrition during the last trimester of
pregnancy.

Acknowledgements
The authors wish to thank Westco for the donation of the lentil screenings, the Western
Canadian Sheep Research Committee for funding this study and the Canada-Alberta
Livestock Research Trust for provision of the lambs and ewes. Recognition is also due to
Andy, Brian and Ray of the LRC Sheep Crew for their excellent feeding and care of ewes
and lambs on this study. Thanks also to Wendi Smart for her skilful technical assistance
and to Walt Strand of Strand Suffolks for suggesting the topic of lentil screenings.

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