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Spineless cactus (Opuntia ficus indica f. inermis) and oldman saltbush (Atriplex nummularia L.) as alternative supplements for growing Barbarine lambs given straw-based diets
Small Ruminant Research 51 (2004) 65–73
Spineless cactus (Opuntia ficus indica f. inermis) and oldman saltbush (Atriplex nummularia L.) as alternative supplements for growing Barbarine lambs given straw-based diets H. Ben Salem a,∗ , A. Nefzaoui a , L. Ben Salem b a
INRA-Tunisie, Laboratoire des Productions Animales et Fourragères, Rue Hédi Karray, 2049 Ariana, Tunisia b Office de l’Elevage et des Pˆ aturages, Rue Alain Savary, 1002 Tunis, Tunisia Accepted 12 May 2003
Abstract Atriplex nummularia L. foliage (atriplex) and Opuntia ficus indica f. inermis pads (cactus) have been used as alternative N and energy supplements, respectively. Twenty-four Barbarine lambs (7-month-old, 19.5 ± 0.5 kg BW) were allotted into four homogeneous groups and housed in individual crates. Each group received barley straw ad libitum and was supplemented on fresh weight basis with either barley grains (0.2 kg) and soybean meal (0.18 kg) (BS); or barley grains (0.2 kg) and atriplex (1.7 kg) (BA); or cactus (3.5 kg) and soybean meal (0.18 kg) (CS); or cactus (3.5 kg) and atriplex (1.7 kg) (CA). Urea was added to make 2 diets iso-nitrogenous. Animals were adapted for experimental conditions for 15 days before starting the 60-day growth trial. At the end of the growth trial, animals were housed in metabolic cages for total faecal collection during 10 consecutive days. Replacing soybean meal by atriplex had no effect on straw DMI (P > 0.05). However, sheep fed cactus consumed less straw than those given barley. Crude protein digestibility was high (71–74%) and similar (P > 0.05) among diets. Diets BS, BA and CS had the same organic matter and fibre (NDF and ADF) digestibilities, which were significantly lower than those of diet CA. Nitrogen retention was high for all diets ranging between 9 and 12 g per day. Difference in N balance among diets was ascribed to the different amount of N consumed, since N loss was quite similar among dietary treatments. Urinary excretion of allantoin and microbial N supply were highest in sheep fed cactus-containing diets (8.3 and 11.4 g microbial N/kg DOMI, respectively, with CS and CA diets) as compared to barley-containing diets (3.5 and 3.2 g microbial N/kg DOMI, respectively, with BS and BA diets). Daily gain of lambs averaged 119, 108, 81 and 59 g, respectively, for diets CS, BS, CA and BA (P < 0.05). These results suggest that in presence of soybean meal as N source, cactus may replace barley grains without any effect on growth rate (P > 0.05). The lowest growth recorded in sheep receiving atriplex (CA; BA) may be ascribed to the high level of soluble N in this shrub species. In practice, growth rate (81 g per day) obtained without use of classic costly concentrate feeds (barley grains and soybean meal), which were replaced by cactus and atriplex (CA diet), would satisfy smallholders when considering feeding cost. © 2003 Elsevier B.V. All rights reserved. Keywords: Atriplex nummularia; Opuntia ficus indica f. inermis; Barley grains; Soybean meal; Alternative supplements; Barbarine lambs
1. Introduction ∗
Corresponding author. Tel.: +216-71-230024; fax: +216-71-752897. E-mail address: [email protected] (H. Ben Salem).
The use of multipurpose trees and shrubs has become an alternative way to feed ruminants in harsh environments (FAO, 1992; Topps, 1992). In arid and
0921-4488/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0921-4488(03)00186-X
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semi-arid zones of Tunisia and many other countries in Western Asia and North Africa, feed nutrients for small ruminants are provided mainly by cereal crop residues and natural pastures, which generally do not meet nutrient requirements for meat production (Nefzaoui, 1997). The use of concentrates is a common option, that farmers adopt to supplement poor quality roughages. Advantages of energy and N supplements on the nutritive value of straw-based diets and sheep growth have been demonstrated in numerous studies. However, concentrate feeds are often costly and in seasonal and/or limited supply. Therefore, the use of appropriate alternative feed supplements should be encouraged to provide animals reared in harsh conditions with main nutrients to balance diets and reduce their cost. Sheep husbandry play a key role in agriculture production in numerous countries. In Tunisia, about 45% of red meat production are provided by sheep. This country is home to ca. 4.1 millions of ewes, about 60% of which are local Barbarine breed (Nacef, 2001). This fat tail breed is widespread in central and southern Tunisia where harsh conditions prevail. Compared to other breeds, Barbarine sheep may mobilise body reserves to withstand in under-nutrition conditions and valorise better local available feed sources (Atti and Bocquier, 1999). The literature reports several fodder shrubs and trees which may replace partially or totally concentrate feeds without decreasing digestion and growth performance of sheep and goats. Ondiek et al. (2000) concluded that Leucaena leucocephala and Gliricidia sepium foliage could contribute as N sources in compounded diet supplements without any detrimental effects on production in dairy goats. Liu et al. (2001) confirmed that mulberry (Morus alba) leaves could be used as a protein supplement to ammoniated rice straw diet to fully substitute for rapeseed meal given to sheep. Atriplex nummularia L. and Opuntia ficus indica f. inermis are two browse species widely established in the arid and semi-arid zones of Tunisia. The establishment of about 6 00 000 ha of spineless cactus, A. nummularia, A. halimus and Acacia cyanophylla plantation was scheduled in the national strategy of rangeland rehabilitation, which started in 1990. These multipurpose plant species withstand drought conditions and grow on marginal soils (Le Houérou, 2000). Cactus is distinctly characterised by a high water use efficiency. Pads of this plant species are covered
with a layer of wax and a thick epidermis which stop water evaporation (Nobel and Bobich, 2002). The high level of salt in atriplex roots and foliage confers to this halophyte species a high osmotic pressure in cellular sap. This phenomenon reflects a physiological adaptation of this plant species to water scarcity (De Kock, 1980). Both cactus and atriplex produce high amounts of consumable biomass and may provide the livestock with an evergreen fodder bank. Ben Salem et al. (2002c) claimed that A. nummularia and spineless cactus are two complementary feed sources. Indeed, the foliage of the former species is high in CP, ash, and salt but low in energy. However, cactus pads contain high levels of soluble carbohydrates, ash, Ca and K but they are low in CP and fibre. Of particular interest is the water richness of cactus pads (80–90%), which may overcome the problem of watering animals in harsh environments and dilute the high salinity of A. nummularia foliage. Ben Salem et al. (2002b) showed that lambs on cactus-based diets supplemented with N source as either A. nummularia foliage or urea-treated straw grew at the same rate. Reducing the use of common concentrate feeds through several alternative feed sources (e.g. feed blocks, browse foliage, etc.) has become a challenging research field. An experiment was therefore performed to study the replacement value of A. nummularia (atriplex; N-rich shrub) and O. ficus indica f. inermis (cactus; energy-rich shrub) for soybean meal and barley grains, respectively, for sheep fed straw-based diets. A growth trial followed by a metabolism trial was carried out.
2. Material and methods 2.1. Animals and management The study was carried out on a farm belonging to the Pasture and Livestock Agency (Office de l’Elevage et des Pˆaturages) at Jebibina during the summer season (June–August 1996). The study area is located in Central Tunisia, semi-arid zone, with a mean annual rainfall of 390 mm. Twenty-four Barbarine male lambs (7-month-old, 19.5 ± 0.5 kg BW) were randomly divided into four groups. Each group consisted of six animals. The lambs were housed in a well-ventilated cement-floored barn having individual feeding facilities (indoor’s temperature 29.7 ± 4.2 ◦ C). All sheep
H. Ben Salem et al. / Small Ruminant Research 51 (2004) 65–73
were drenched (Synanthic, 2.2 ml/10 kg live weight) against internal parasites before the onset of experiment and kept under strict hygiene and uniform management throughout the experiment.
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individually. Lambs of control group (BS) were fed as per INRA (1988) requirements so that they should grow at a rate of 100 g per day. 2.3. Growth trial
2.2. Feeds and feeding Consumable parts (leaves and twigs) of A. nummularia L. (oldman saltbush) and current-year pads of O. ficus indica f. inermis (spineless cactus) were harvested daily at 06:00 h and distributed to animals in the same day. Cactus pads were cut into slices with a manual chopper then given to animals. The atriplex and cactus plantations were established in 1981 and 1965, respectively. All the lambs received barley (Rihane variety) straw ad libitum (i.e. about 1.2 times the previous day’s intake) as basal roughage. Each group was supplemented with either barley grains and soybean meal (diet BS); or barley grains and atriplex (diet BA); or cactus and soybean meal (diet CS); or cactus and atriplex (diet CA). Urea, CaCO3 and CaHPO4 were supplied to render diets iso-nitrogenous and balanced for calcium and phosphorus. Composition of the above diets is given in Table 1. Weighed quantities of experimental feeds were offered daily at 09:00 h after removal of residues, if any. Clean and fresh drinking water was offered ad libitum once a day to all animals
Table 1 Formulation of experimental diets distributed to lambs (fresh weight basis) Feeds
Barley straw Barley grains (kg) Soybean meal (kg) O.F.I. f. inermisb (kg) A. nummularia (kg) Urea (g) CaCO3 (g) CaHPO4 (g)
Dietsa BS
BA
CS
CA
Ad libitum 0.2 0.18 – – – 5.0 5.6
Ad libitum 0.2 – – 1.7 – 2.5 8.1
Ad libitum – 0.18 3.5 – 3 1.4 6.5
Ad libitum – – 3.5 1.7 3 – 7.1
a BS: barley straw ad libitum supplemented with barley grains and soybean meal; BA: barley straw ad libitum supplemented with barley grains and atriplex; CS: barley straw ad libitum supplemented with spineless cactus and soybean meal; CA: barley straw ad libitum supplemented with spineless cactus and atriplex. b O.F.I. f. inermis: O. ficus indica f. inermis (spineless cactus).
Body weight was recorded on 15:00 h in fasted animals before feeding and watering for two consecutive days at the beginning and the end of the 60-day experimental period. Daily feed intake was controlled throughout the trial. Animals were adapted to housing conditions for a week and received a common diet of oat hay ad libitum and 400 g barley. They were then adapted to the dietary treatments for 15 days before starting the experimental feeding. 2.4. Metabolism trial A metabolism trial of 10 days duration, involving quantitative collection of feeds, refusals, faeces and urine was performed at the end of the growth trial in order to assess the apparent digestibility of diets, N balance and microbial N synthesis. The lambs were acclimatised in the metabolism cages for 5 days prior to faecal collection. Faeces voided and urine excreted during 24 h were weighed. Representative samples of feeds, refusals and faeces were daily prepared and dried at 105 ◦ C for DM determination. Other representative samples of each animal over the entire collection period were bulked, sampled and ground to pass through 1 mm sieve and stored pending laboratory analysis. The complete output of urine was collected into 100 ml of 10% sulphuric acid solution (v/v). Representative aliquots of urine from individual animals were immediately stored in a freezer (−20 ◦ C) until analysed for N and allantoin. 2.5. Analytical methods Ground samples of feeds, refusals and faeces were analysed for DM, ash, and CP (AOAC, 1984), NDF, ADF and acid detergent lignin (ADL) (Van Soest et al., 1991). Mineral extracts of feed samples were prepared (AOAC, 1984) and analysed for Ca, Mg, K, Na, Zn, Fe, Cu and Mn after a wet digestion with a mixture of nitric, sulphuric and perchloric acids using an atomic absorption spectrophotometer (Unicam 919). Phosphorus in feed samples was determined colori-
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metrically, using molybdovanadate reagent (AOAC, 1984). Bulked samples of urine were analysed for Kjeldahl N (AOAC, 1984) or diluted (1/30) and allantoin was measured colorimetrically as described by Chen and Gomes (1992). The concept of the method is that allantoin is first hydrolysed under weak alkaline condition at 100 ◦ C, to allantoic acid which was also hydrolysed to urea and glyoxylic acid in a weak acid solution. The glyoxylic acid reacted with phenylhydrazine hydrochloride to produce a phenylhydrazone derivative of the acid. The product formed an unstable chromophore with potassium ferricyanide. The colour was read at 522 nm on a UV spectrophotometer (Spectronic 601).
Data were subjected to analysis of variance and statistical significance among treatment means was determined by Duncan’s multiple range test using GLM (general linear model) procedures of SAS (1987). The following contrasts were used to compare the mean effects of feed supplements: • S versus A: mean effect of soybean meal versus mean effect of atriplex; • B versus C: mean effect of barley grains versus mean effect of cactus. 3. Results 3.1. Feed characteristics
2.6. Calculations and statistical analysis Urinary excretion of allantoin (Y, mmol per day) was used to calculate microbial purines absorbed (X, mmol per day) from the equation: Y = 0.84X + (0.150W 0.75 e−0.25X ), where W is the animal live weight (kg). Microbial N supply (g per day) was calculated from the relationship: 70X/(0.83 × 0.116 × 1000), where 70 is the N content of purines (mg N/mmol), X is as defined above, 0.83 is the assumed digestibility of microbial purines, 0.116 is the ratio of purine N/total N in mixed rumen microbes and 1000 converts mg to g (Chen and Gomes, 1992).
Table 2 shows the composition of experimental feeds. Barley straw and cactus were lowest in CP. Both atriplex and cactus were high in ash. Cactus and atriplex were highest in Ca and Na, respectively. 3.2. Feed intake and daily gain (growth trial) Average intake of straw and diet (60 days) and live weight changes by lambs during the growth trial are given in Table 3. Straw DM intake was low among dietary treatments. Lowest consumption of straw was recorded on sheep given cactus. Replacing barley grains with cactus, and soybean meal with atriplex
Table 2 Chemical composition of feeds
Dry matter (g/kg) Organic matter (g/kg DM) Crude protein (g/kg DM) NDF (g/kg DM) ADF (g/kg DM) ADL (g/kg DM) Ca (g/kg DM) P (g/kg DM) Na (g/kg DM) K (g/kg DM) Mg (g/kg DM) Cu (mg/kg DM) Fe (mg/kg DM) Mn (mg/kg DM) Zn (mg/kg DM) a
Barley straw
Barley grain
Soybean meal
A. nummularia
O.F.I. f. inermisa
868 948 34 764 467 95 4.4 1.2 2.6 16.4 1.0 6.1 160.7 36.7 18.3
859 976 141 289 67 12 0.8 2.2 0.2 7.8 1.1 2.4 40.4 11.6 22.3
883 931 465 370 109 50 3.1 7.1 3.0 25.9 2.4 17.8 299.8 26.9 48.3
286 745 178 445 225 102 13.6 1.8 47.0 28.9 8.4 13.0 285.1 56.5 47.0
177 762 46 338 168 52 52.1 1.0 0.6 26.0 10.9 6.5 170.8 248.9 31.0
O.F.I. f. inermis: Opuntia ficus indica f. inermis (spineless cactus).
H. Ben Salem et al. / Small Ruminant Research 51 (2004) 65–73
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Table 3 Feed intake and daily gain during the growth trial of Barbarine lambsa Basal diet: barley straw ad libitumb Barley soybean Dry matter intake (g per day) Straw 435 a Barley 178 Soybean meal 157 Atriplex – Cactus – Diet 770 d Daily gain (g) 108 a
S.E.M.
Barley atriplex
Cactus soybean
Cactus atriplex
399 b 178 – 378 – 955 c 59 c
262 c – 157 – 577 995 b 119 a
207 d – – 356 499 1062 a 81 b
3
5 2
Contrastsc S versus A
B versus C
∗∗∗
∗∗∗
∗∗∗
∗∗∗
∗∗∗
∗∗
Means in the same line with different letters are different (P < 0.05). Supplements: BS, barley soybean; BA, barley atriplex; CS, cactus soybean; CA, cactus atriplex. c S vesus A: average effect of soybean meal versus average effect of atriplex; B versus C: average effect of barley versus average effect of cactus. ∗∗ P < 0.01. ∗∗∗ P < 0.001. a
b
decreased straw intake (P < 0.05). However, total DM intake was higher in sheep given alternative supplements as compared to those receiving common concentrate feeds. All sheep gained weight. Association of soybean meal to either barley grains or cactus per-
formed the highest daily gain (108 and 119 g per day, respectively). Irrespective to the energy source (i.e. barley and cactus), replacing soybean meal by atriplex decreased growth rate. Lowest gain was obtained with BA diet.
Table 4 Feed and water intakes during the metabolism trial of Barbarine lambsa Basal diet: barley straw ad libitumb
DMI (g per day) Straw Barley Soybean meal Atriplex Cactus Diet DMI (g/kg W0.75 ) Straw Diet Water consumed Litre/kg DMI Litre/kg W0.75
S.E.M.
Barley soybean
Barley atriplex
Cactus soybean
Cactus atriplex
514 a 178 157 – – 849 d
469 b 178 – 486 – 1088 b
398 c – 157 – 618 1016 c
321 d – – 486 618 1375 a
43.6 a 72.1 d 3.05 a 0.219 b
42.8 a 99.4 b 2.92 a 0.290 a
33.4 b 85.2 c 1.30 b 0.111 c
28.8 c 123.0 a 1.50 b 0.183 b
S versus A
B versus C
6
∗∗∗
∗∗∗
6
∗∗∗
∗∗∗
∗
∗∗∗
∗∗∗
∗∗∗
nsd
∗∗∗
0.5 0.8 0.07 0.006
Means in the same line with different letters are different (P < 0.05). Supplements: BS, barley soybean; BA, barley atriplex; CS, cactus soybean; CA, cactus atriplex. c Refer to Table 3 footnote. d Non-significant effect. ∗ P < 0.05. ∗∗∗ P < 0.001. a
b
Contrastsc
∗∗∗
∗∗∗
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H. Ben Salem et al. / Small Ruminant Research 51 (2004) 65–73
Table 5 Apparent digestibility and feeding value of diets in Barbarine lambsa Basal diet: barley straw ad libitumb Barley soybean
S.E.M.
Barley atriplex
Cactus soybean
Cactus atriplex
Diet digestibility (%) DM 67.1 b OM 69.5 b CP 72.7 NDF 68.3 b ADF 61.2 bc Cellulose 66.4 ab
68.1 68.2 71.3 68.2 59.9 64.5
66.6 71.0 71.2 68.8 65.7 76.9
72.1 75.4 72.8 73.5 70.3 75.2
Intake (g/kg W0.75 ) Digestible OM Digestible CP
64.0 b 7.9 a
47.5 d 7.2 b
b b b c c
b b b b a
59.0 c 6.9 b
a a
0.4 0.4 0.5 0.5 0.7 1.3
a a ab
74.7 a 7.8 a
Contrastsc S versus A
B versus C
∗∗
nsd
ns ns ∗
ns ns
0.5 0.1
∗∗∗
ns ∗
∗∗∗ ∗∗
∗∗∗
∗∗∗
∗∗∗
ns
Means in the same line with different letters are different (P < 0.05). Supplements: BS, barley soybean; BA, barley atriplex; CS, cactus soybean; CA, cactus atriplex. c Refer to Table 3 footnote. d Non-significant effect. ∗ P < 0.05. ∗∗ P < 0.01. ∗∗∗ P < 0.001. a
b
3.3. Feed intake and diet digestibility (metabolism trial)
soybean meal by atriplex increased water consumption, expressed as litre per kilogram metabolic weight, by sheep (P < 0.001). Table 5 reports apparent digestibility of diets. All dietary treatments exhibited similar CP digestibility, which was above 70%. Supply of cactus and atriplex resulted in the highest DM, OM, NDF and ADF digestibility of the diet. Replacing soybean meal by atriplex had no effect on nutrient digestibility. Intake of digestible OM increased when common supplements
Feed and water intakes are given in Table 4. Irrespective of supplements, DM intake of barley straw was low (29–44 g/kg W0.75 ). Similarly to the growth trial, replacing barley grains with cactus decreased straw intake, the lowest straw intake was obtained with the CA diet. Lambs given cactus consumed less water than those on cactus-free diets (P < 0.05). Replacing Table 6 Nitrogen balance and microbial synthesis in Barbarine lambsa Basal diet: barley straw ad libitumb
N intake (g per day) Faecal N (g per day) Urinary N (g per day) Retained N (g per day) Urinary allantoin (mg/kg W0.75 ) Microbial N (g/kg DOMI)e
S.E.M.
Barley soybean
Barley atriplex
Cactus soybean
Cactus atriplex
18.7 5.1 4.2 9.4 32.0 3.5
18.7 5.6 5.6 7.5 28.4 3.2
20.0 5.8 4.7 9.5 48.3 8.3
20.7 4.7 3.8 12.2 56.7 11.4
c ab b b b b
c a a c b b
b a ab b a a
a b b a a a
Means in the same line with different letters are different (P < 0.05). Supplements: BS, barley soybean; BA, barley atriplex; CS, cactus soybean; CA, cactus atriplex. c Refer to Table 3 footnote. d Non-significant effect (P > 0.05). e Microbial nitrogen supply expressed as g/kg digestible organic matter intake (DOMI). ∗ P < 0.05. ∗∗∗ P < 0.001. a
b
Contrastsc S versus A
0.06 0.10 0.18 0.16 4.1 1.2
B versus C
∗
∗∗∗
nsd ns ns ns ns
ns ns
∗∗∗ ∗∗∗ ∗∗∗
H. Ben Salem et al. / Small Ruminant Research 51 (2004) 65–73
(barley grains and soybean meal) were replaced with cactus and/or atriplex. Digestible CP intake was not changed with cactus provision. Atriplex supplemented diets (BA and CA) exhibited the highest digestible CP intake. 3.4. Nitrogen balance and microbial synthesis N balance and microbial N supply are given in Table 6. Sheep receiving barley grains with soybean meal or atriplex consumed the same amount of N. However, N intake was highest when straw was supplemented with cactus combined with soybean meal or atriplex. There was no specific variation of N loss either in faeces or urine among dietary treatments. The increase of N losses in sheep receiving barley and atriplex as compared to those on BS was offset when cactus replaced barley grains and combined with soybean meal or atriplex. N retention was high among the four diets. Simultaneous supply of cactus and atriplex resulted in the highest N retention. Within an energy source (barley grains or cactus) allantoin excretion was similar for soybean meal and atriplex supplemented diet (P > 0.05). Urine of lambs receiving cactus contained substantially high amount of allantoin than those given barley grains (P < 0.001). The same trend was noted for the efficiency of microbial N supply.
4. Discussion There is a battery of information on how classic concentrate feeds (barley, soybean and rapeseed meals, wheat bran, mixed concentrate feeds, etc.) affect animal response on low quality roughages (Doyle et al., 1988; Chen et al., 1992; Dixon and Egan, 2000). However, very little is known about the replacement value of shrub foliage for these concentrate feeds and how intake, digestion and sheep performance are affected. The limited and irregular availability of common concentrate feeds and their high cost are considered by smallholders among the main problems for the development of the livestock sector. Having suitable shrub plantations that withstand harsh conditions and improve livestock performance without great need for concentrate feeds is a challenging option for farmers.
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Data reported in the current work and in our previous studies (Ben Salem et al., 2002a,b,c) showed that the contribution of common roughages and concentrate feeds in sheep diets could be reduced through the use of cactus pads and saltbushes (atriplex) without any detrimental effect on sheep growth. In this study, replacing barley grains and/or soybean meal by cactus and/or atriplex, respectively, decreased straw intake in the growth and metabolism trials. In agreement with Dixon and Egan (2000), this trend may be the result of substitutive effects. Crude protein in soybean meal was about 2.6 times that in atriplex foliage and ME in barley grains was about 1.5 times that in cactus pads. Moreover, cactus was substantially lower in DM than barley grains. Therefore, to have diets balanced for energy and N, great amounts of alternative supplements have to be distributed to animals. Therefore, cactus- and/or atriplex-containing diets would be bulky as compared to BS diet. Even though, this study denotes the lack of negative effect of cactus and/or atriplex provision on diet digestibility, which remained as high as that of the control diet (i.e. supplemented with barley grains and soybean meal). Diet containing both cactus and atriplex exhibited highest apparent digestibility of OM, NDF and ADF. The complementary role of these two range species in sheep feeding was demonstrated earlier by Ben Salem et al. (2002a,b) and reviewed by Ben Salem et al. (2002c) and Nefzaoui and Ben Salem (2002). Salt present in high level in atriplex foliage could be diluted by the high amount of water stocked in cactus pads. Moreover, atriplex may overcome N and fibre deficit in cactus while the latter plant species provides energy in the form of soluble carbohydrates. Owing to its low DM content and richness in soluble carbohydrates, one would expect cactus to have a similar effect than molasses on straw intake and digestion in sheep. However, this hypothesis was rejected by Ben Salem et al. (1996). These authors showed that provision of graded levels of spineless cactus (0, 150, 300, 450 and 600 g DM) for sheep did not decrease straw intake, increased the amount of digestible OM and CP intakes and improved rumen fermentation. In contrast to the classic effect of molasses, rumen pH was not decreased with cactus supply. The abundance of mucilage and mineral salts in cactus pads may enhance salivation, thus maintain pH in the normal range (6.5–7).
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Variation of N balance among dietary treatments is likely the result of the different amounts of N consumed by lambs since there was no consistent trend of N losses either in faeces or urine. Our findings suggested that cactus-containing diets promoted microbial activity better than those on barley-containing diets. This trend is reinforced with urinary excretion of allantoin and consequently with microbial N supply. This is likely the result of increased amount of DOMI rather than to the type of supplement per se. It is well documented that in the presence of adequate protein in the diet the amount of N synthesised by micro-organisms increases with the level of energy supplied (Chen et al., 1992; Balcells et al., 1993). Of particular interest is the similar amount of allantoin in urine and the level of microbial N obtained in lambs given barley grains with soybean meal or atriplex. On the basis of AFRC (1993) equation (ME intake MJ per day = 0.0157 × DOMI), the ME intakes of lambs on diets BS, BA, CS and CA were 8.77, 10.99, 11.07 and 13.0 MJ per day, respectively. According to the daily maintenance allowance of ME for growing sheep (live weight 20 kg) estimated to 3.8 MJ (McDonald et al., 1981), it is clear that sheep on the four dietary treatments had sufficiently high intakes to meet ME requirements for maintenance and gain, which was above 50 g per day. Diets were balanced not only for energy and N but also for Ca and P. Irrespective to the energy source, lambs given soybean meal performed better than those receiving atriplex. Although they were expected to consume the same amount of N, differences in the quality of N in these feeds may account for this trend. Ben Salem et al. (2002a) showed that about 70% of total N in atriplex foliage was in the soluble form, therefore and in contrast to soybean meal, the amount of true protein and by-pass protein should be low in atriplex. One adverse consequence of supplying the rumen with more than optimal concentrations of ammonia-N is the energetic inefficiency incurred in converting ammonia to urea for excretion. The advantage of supplying adequate energy and protein is shown in the BS diet, which had a high BW gain. This observation can be attributed to the type of protein and its degradability and also possibly to the lack of synchrony between N release through protein degradation and energy availability. This results in reduced efficiency of rumen ammonia utilisation by the microbes leading to excess ammonia
being absorbed into the blood stream and lost in urine as urea, which is consistent with the increased urinary N excretions by animals on BA. Increased daily gain in sheep given CA as compared to those on BA may be the result of synchronised supply of energy as sugar from cactus and N from atriplex. Moreover, cactus intake may have contributed to a continued dilution and excretion of salt in atriplex foliage.
5. Conclusions Under West Asia and North Africa conditions a wide variety of shrub species offers an economical alternative to costly energy and protein supplements. This should encourage widespread introduction of shrub and tree species for eco-regeneration and as nutrient-rich fodder in waste lands. The pattern of growth and nutrient utilisation observed in this study indicates that supplementation of poor quality roughages with spineless cactus and atriplex had a positive impact on sheep gain, and more interestingly that these browse species may reduce the use of costly concentrate feeds, thus alleviate feeding cost. Association of soybean meal with cactus instead of barley resulted in highest growth rate (ca. 120 g per day), and diet cost should be considerably decreased as compared to barley–soybean meal combination (ca. 110 g per day). The farmer could be satisfied by a daily gain of 80 g when common concentrate feeds (i.e. barley and soybean meal) are totally removed from the diet of lambs and replaced by cactus and atriplex, provided that these range species provide similar amounts of energy and N as by barley grains and soybean meal.
Acknowledgements This work was conducted with the financial support of ‘Secrétariat d’Etat à la Recherche Scientifique et à la Technologie (SERST-Tunisie)’ and the Pasture and Livestock Agency (Office de l’Elevage et des Pˆaturages-Tunisie). References Agricultural Food and Research Council (AFRC), 1993. Energy and protein requirements of ruminants. An Advisory Manual
H. Ben Salem et al. / Small Ruminant Research 51 (2004) 65–73 prepared by the AFRC Technical Committee on Responses to Nutrients. CAB International, Wallingford, UK, 159 pp. AOAC, 1984. Official Methods of Analysis, 14th ed. Association of Official Analytical Chemists, Washington, DC, 1141 pp. Atti, N., Bocquier, F., 1999. Adaptation des brebis Barbarine à l’alternance sous-nutrition-réalimentation: effets sur les tissus adipeux. Ann. Zootech. 48, 189–198. Balcells, J., Fondevila, M., Guada, J.A., Castrillo, C., Surra, J.C.E., 1993. Urinary excretions of purine derivatives and nitrogen in sheep given straw supplemented with different sources of carbohydrates. Anim. Prod. 57, 287–292. Ben Salem, H., Nefzaoui, A., Abdouli, H., Ørskov, E.R., 1996. Effect of increasing level of spineless cactus (Opuntia ficus indica var. inermis) on intake and digestion by sheep fed straw-based diets. Anim. Sci. 62, 293–299. Ben Salem, H., Nefzaoui, A., Ben Salem, L., 2002a. Supplementation of Acacia cyanophylla Lindl. foliage-based diets with barley or shrubs from arid areas (Opuntia ficus indica f. inermis and Atriplex nummularia L.) on growth and digestibility in lambs. Anim. Feed Sci. Technol. 96, 15–30. Ben Salem, H., Nefzaoui, A., Ben Salem, L., 2002b. Supplementing spineless cactus (Opuntia ficus indica f. inermis) based diets with urea-treated straw or oldman saltbush (Atriplex nummularia L.). Effects on intake, digestion and growth. J. Agric. Sci. 138, 85–92. Ben Salem, H., Nefzaoui, A., Ben Salem, L., 2002c. Opuntia ficus-indica f. inermis and Atriplex nummularia L. Two complementary fodder shrubs for sheep and goats. Acta Hortic. 581, 333–341. Chen, X.B., Gomes, M.J., 1992. Estimation of Microbial Protein Supply to Sheep and Cattle Based on Urinary Excretion of Purine Derivatives. An Overview of the Technical Details. Occasional Publication 1992. International Feed Resources Unit, Rowett Research Institute, Aberdeen, 19 pp. Chen, X.B., Abdurrazak, S.A., Shand, W.J., Ørskov, E.R., 1992. The effect of supplementing straw with barley or unmolassed sugar-beet pulp on microbial protein supply in sheep estimated from urinary purine derivative excretion. Anim. Prod. 55, 413– 417. De Kock, G.C., 1980. Cultures d’arbustes fourragers résistants à la sécheresse (Establishment of drought-resistant fodder shrubs). In: Le Houérou, H.N. (Ed.), Les fourrages ligneux en Afrique. Etat actuel des connaissances (Woody fodder species in Africa. Current knowledge). Centre International pour l’Elevage en Afrique. Addis Abeba, Ethiopie, pp. 387–396. Dixon, R.M., Egan, A.R., 2000. Response of lambs fed low quality roughage to supplements based on urea, cereal grain, or protein meals. Aust. J. Agric. Res. 51, 811–821. Doyle, P.T., Dove, H., Freer, M., Hart, F.J., Dixon, R.M., Egan, A.R., 1988. Effects of a concentrate supplement on the intake and digestion of a low-quality forage by lambs. J. Agric. Sci. Camb. 111, 503–511.
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Food and Agriculture Organization (FAO), 1992. Legume trees and other fodder trees as protein sources for livestock. In: Speedy, A., Pugliese, P.L. (Eds.), Proceedings of the FAO Expert Consultation held at the Malaysian Agricultural Research and Development Institute (MARDI) in Kuala Lumpur, Malaysia, 14–18 October, 1991. FAO, 339 pp. INRA, 1988. In: Jarrige, R. (Ed.), Alimentation des bovins, ovins et caprins. INRA (Institut National de la Recherche Agronomique), Paris, 476 pp. Le Houérou, H.N., 2000. Use of fodder trees and shrubs in the arid and semi-arid zones of West Asia and North Africa: history and perspectives. In: Gintzburger, G., Bounejmate, M., Nefzaoui, A. (Eds.), Fodder Shrub Development in Arid and Semi-arid zones. Proceedings of the Workshop on Native and Exotic Fodder Shrubs in Arid and Semi-arid Zones, vol. II, 27 October–2 November 1996, Hammamet, Tunisia. ICARDA, Aleppo, Syria, pp. 9–53 and viii + 293–697. Liu, J.X., Jun, Y., Yan, B., Yu, J.Q., Shi, Z.Q., 2001. Effects of mulberry leaves to replace rapeseed meal on performance of sheep feeding on ammoniated rice straw diet. Small Rumin. Res. 39, 131–136. McDonald, P., Edwards, R.A., Greenhalgh, J.F.D., 1981. Animal Nutrition, 3rd ed. Longman, New York, 479 pp. Nacef, N., 2001. Livestock sector in Tunisia. Agric. Rev. 45, 25– 27 (in Arabic). Nefzaoui, A., 1997. Crop–livestock integration through better use of feed resources in Tunisia. In: Haddad, N., Tutwiler, R., Thomson, E. (Eds.), Improvement of Crop–Livestock Integration Systems in West Asia and North Africa. Proceedings of the Regional Symposium on Integrated Crop–Livestock Systems in the Dry Areas of West Asia and North Africa, 6–8 November 1995, Amman, Jordan. ICARDA, Aleppo, Syria, pp. 64–76 and xi + 572 + 40. Nefzaoui, A., Ben Salem, H., 2002. Forage, fodder, and animal nutrition. In: Nobel, P.S. (Ed.), Cacti: Biology and Uses. University of California Press, pp. 190–210. Nobel, P.S., Bobich, E.G., 2002. Environmental biology. In: Nobel, P.S. (Ed.), Cacti: Biology and Uses. University of California Press, pp. 57–74. Ondiek, J.O., Tuitoek, J.K., Abdulrazak, S.A., Bareeba, F.B., Fujihara, T., 2000. Use of Leucaena leucocephala and Gliricidia sepium as nitrogen sources in supplementary concentrates for dairy goats offered rhodes grass hay. Asian-Aus. J. Anim. Sci. 13, 1249–1254. SAS, 1987. User’s Guide: Statistics, 6th ed. Statistical Analysis Systems Institute, Cary, NC. Topps, J.H., 1992. Potential, composition and use of legume shrubs and trees as fodder for livestock in the tropics. J. Agric. Sci. Camb. 118, 1–8. Van Soest, P.J., Robertson, J.B., Lewis, B.-A., 1991. Methods for dietary fibre, neutral detergent fibre, and non-starch carbohydrates in relation to animal nutrition. J. Dairy Sci. 74, 3583–3597.
Spineless cactus (Opuntia ficus indica f. inermis) and oldman saltbush (Atriplex nummularia L.) as alternative supplements for growing Barbarine lambs given straw-based diets H. Ben Salem a,∗ , A. Nefzaoui a , L. Ben Salem b a
INRA-Tunisie, Laboratoire des Productions Animales et Fourragères, Rue Hédi Karray, 2049 Ariana, Tunisia b Office de l’Elevage et des Pˆ aturages, Rue Alain Savary, 1002 Tunis, Tunisia Accepted 12 May 2003
Abstract Atriplex nummularia L. foliage (atriplex) and Opuntia ficus indica f. inermis pads (cactus) have been used as alternative N and energy supplements, respectively. Twenty-four Barbarine lambs (7-month-old, 19.5 ± 0.5 kg BW) were allotted into four homogeneous groups and housed in individual crates. Each group received barley straw ad libitum and was supplemented on fresh weight basis with either barley grains (0.2 kg) and soybean meal (0.18 kg) (BS); or barley grains (0.2 kg) and atriplex (1.7 kg) (BA); or cactus (3.5 kg) and soybean meal (0.18 kg) (CS); or cactus (3.5 kg) and atriplex (1.7 kg) (CA). Urea was added to make 2 diets iso-nitrogenous. Animals were adapted for experimental conditions for 15 days before starting the 60-day growth trial. At the end of the growth trial, animals were housed in metabolic cages for total faecal collection during 10 consecutive days. Replacing soybean meal by atriplex had no effect on straw DMI (P > 0.05). However, sheep fed cactus consumed less straw than those given barley. Crude protein digestibility was high (71–74%) and similar (P > 0.05) among diets. Diets BS, BA and CS had the same organic matter and fibre (NDF and ADF) digestibilities, which were significantly lower than those of diet CA. Nitrogen retention was high for all diets ranging between 9 and 12 g per day. Difference in N balance among diets was ascribed to the different amount of N consumed, since N loss was quite similar among dietary treatments. Urinary excretion of allantoin and microbial N supply were highest in sheep fed cactus-containing diets (8.3 and 11.4 g microbial N/kg DOMI, respectively, with CS and CA diets) as compared to barley-containing diets (3.5 and 3.2 g microbial N/kg DOMI, respectively, with BS and BA diets). Daily gain of lambs averaged 119, 108, 81 and 59 g, respectively, for diets CS, BS, CA and BA (P < 0.05). These results suggest that in presence of soybean meal as N source, cactus may replace barley grains without any effect on growth rate (P > 0.05). The lowest growth recorded in sheep receiving atriplex (CA; BA) may be ascribed to the high level of soluble N in this shrub species. In practice, growth rate (81 g per day) obtained without use of classic costly concentrate feeds (barley grains and soybean meal), which were replaced by cactus and atriplex (CA diet), would satisfy smallholders when considering feeding cost. © 2003 Elsevier B.V. All rights reserved. Keywords: Atriplex nummularia; Opuntia ficus indica f. inermis; Barley grains; Soybean meal; Alternative supplements; Barbarine lambs
1. Introduction ∗
Corresponding author. Tel.: +216-71-230024; fax: +216-71-752897. E-mail address: [email protected] (H. Ben Salem).
The use of multipurpose trees and shrubs has become an alternative way to feed ruminants in harsh environments (FAO, 1992; Topps, 1992). In arid and
0921-4488/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0921-4488(03)00186-X
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semi-arid zones of Tunisia and many other countries in Western Asia and North Africa, feed nutrients for small ruminants are provided mainly by cereal crop residues and natural pastures, which generally do not meet nutrient requirements for meat production (Nefzaoui, 1997). The use of concentrates is a common option, that farmers adopt to supplement poor quality roughages. Advantages of energy and N supplements on the nutritive value of straw-based diets and sheep growth have been demonstrated in numerous studies. However, concentrate feeds are often costly and in seasonal and/or limited supply. Therefore, the use of appropriate alternative feed supplements should be encouraged to provide animals reared in harsh conditions with main nutrients to balance diets and reduce their cost. Sheep husbandry play a key role in agriculture production in numerous countries. In Tunisia, about 45% of red meat production are provided by sheep. This country is home to ca. 4.1 millions of ewes, about 60% of which are local Barbarine breed (Nacef, 2001). This fat tail breed is widespread in central and southern Tunisia where harsh conditions prevail. Compared to other breeds, Barbarine sheep may mobilise body reserves to withstand in under-nutrition conditions and valorise better local available feed sources (Atti and Bocquier, 1999). The literature reports several fodder shrubs and trees which may replace partially or totally concentrate feeds without decreasing digestion and growth performance of sheep and goats. Ondiek et al. (2000) concluded that Leucaena leucocephala and Gliricidia sepium foliage could contribute as N sources in compounded diet supplements without any detrimental effects on production in dairy goats. Liu et al. (2001) confirmed that mulberry (Morus alba) leaves could be used as a protein supplement to ammoniated rice straw diet to fully substitute for rapeseed meal given to sheep. Atriplex nummularia L. and Opuntia ficus indica f. inermis are two browse species widely established in the arid and semi-arid zones of Tunisia. The establishment of about 6 00 000 ha of spineless cactus, A. nummularia, A. halimus and Acacia cyanophylla plantation was scheduled in the national strategy of rangeland rehabilitation, which started in 1990. These multipurpose plant species withstand drought conditions and grow on marginal soils (Le Houérou, 2000). Cactus is distinctly characterised by a high water use efficiency. Pads of this plant species are covered
with a layer of wax and a thick epidermis which stop water evaporation (Nobel and Bobich, 2002). The high level of salt in atriplex roots and foliage confers to this halophyte species a high osmotic pressure in cellular sap. This phenomenon reflects a physiological adaptation of this plant species to water scarcity (De Kock, 1980). Both cactus and atriplex produce high amounts of consumable biomass and may provide the livestock with an evergreen fodder bank. Ben Salem et al. (2002c) claimed that A. nummularia and spineless cactus are two complementary feed sources. Indeed, the foliage of the former species is high in CP, ash, and salt but low in energy. However, cactus pads contain high levels of soluble carbohydrates, ash, Ca and K but they are low in CP and fibre. Of particular interest is the water richness of cactus pads (80–90%), which may overcome the problem of watering animals in harsh environments and dilute the high salinity of A. nummularia foliage. Ben Salem et al. (2002b) showed that lambs on cactus-based diets supplemented with N source as either A. nummularia foliage or urea-treated straw grew at the same rate. Reducing the use of common concentrate feeds through several alternative feed sources (e.g. feed blocks, browse foliage, etc.) has become a challenging research field. An experiment was therefore performed to study the replacement value of A. nummularia (atriplex; N-rich shrub) and O. ficus indica f. inermis (cactus; energy-rich shrub) for soybean meal and barley grains, respectively, for sheep fed straw-based diets. A growth trial followed by a metabolism trial was carried out.
2. Material and methods 2.1. Animals and management The study was carried out on a farm belonging to the Pasture and Livestock Agency (Office de l’Elevage et des Pˆaturages) at Jebibina during the summer season (June–August 1996). The study area is located in Central Tunisia, semi-arid zone, with a mean annual rainfall of 390 mm. Twenty-four Barbarine male lambs (7-month-old, 19.5 ± 0.5 kg BW) were randomly divided into four groups. Each group consisted of six animals. The lambs were housed in a well-ventilated cement-floored barn having individual feeding facilities (indoor’s temperature 29.7 ± 4.2 ◦ C). All sheep
H. Ben Salem et al. / Small Ruminant Research 51 (2004) 65–73
were drenched (Synanthic, 2.2 ml/10 kg live weight) against internal parasites before the onset of experiment and kept under strict hygiene and uniform management throughout the experiment.
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individually. Lambs of control group (BS) were fed as per INRA (1988) requirements so that they should grow at a rate of 100 g per day. 2.3. Growth trial
2.2. Feeds and feeding Consumable parts (leaves and twigs) of A. nummularia L. (oldman saltbush) and current-year pads of O. ficus indica f. inermis (spineless cactus) were harvested daily at 06:00 h and distributed to animals in the same day. Cactus pads were cut into slices with a manual chopper then given to animals. The atriplex and cactus plantations were established in 1981 and 1965, respectively. All the lambs received barley (Rihane variety) straw ad libitum (i.e. about 1.2 times the previous day’s intake) as basal roughage. Each group was supplemented with either barley grains and soybean meal (diet BS); or barley grains and atriplex (diet BA); or cactus and soybean meal (diet CS); or cactus and atriplex (diet CA). Urea, CaCO3 and CaHPO4 were supplied to render diets iso-nitrogenous and balanced for calcium and phosphorus. Composition of the above diets is given in Table 1. Weighed quantities of experimental feeds were offered daily at 09:00 h after removal of residues, if any. Clean and fresh drinking water was offered ad libitum once a day to all animals
Table 1 Formulation of experimental diets distributed to lambs (fresh weight basis) Feeds
Barley straw Barley grains (kg) Soybean meal (kg) O.F.I. f. inermisb (kg) A. nummularia (kg) Urea (g) CaCO3 (g) CaHPO4 (g)
Dietsa BS
BA
CS
CA
Ad libitum 0.2 0.18 – – – 5.0 5.6
Ad libitum 0.2 – – 1.7 – 2.5 8.1
Ad libitum – 0.18 3.5 – 3 1.4 6.5
Ad libitum – – 3.5 1.7 3 – 7.1
a BS: barley straw ad libitum supplemented with barley grains and soybean meal; BA: barley straw ad libitum supplemented with barley grains and atriplex; CS: barley straw ad libitum supplemented with spineless cactus and soybean meal; CA: barley straw ad libitum supplemented with spineless cactus and atriplex. b O.F.I. f. inermis: O. ficus indica f. inermis (spineless cactus).
Body weight was recorded on 15:00 h in fasted animals before feeding and watering for two consecutive days at the beginning and the end of the 60-day experimental period. Daily feed intake was controlled throughout the trial. Animals were adapted to housing conditions for a week and received a common diet of oat hay ad libitum and 400 g barley. They were then adapted to the dietary treatments for 15 days before starting the experimental feeding. 2.4. Metabolism trial A metabolism trial of 10 days duration, involving quantitative collection of feeds, refusals, faeces and urine was performed at the end of the growth trial in order to assess the apparent digestibility of diets, N balance and microbial N synthesis. The lambs were acclimatised in the metabolism cages for 5 days prior to faecal collection. Faeces voided and urine excreted during 24 h were weighed. Representative samples of feeds, refusals and faeces were daily prepared and dried at 105 ◦ C for DM determination. Other representative samples of each animal over the entire collection period were bulked, sampled and ground to pass through 1 mm sieve and stored pending laboratory analysis. The complete output of urine was collected into 100 ml of 10% sulphuric acid solution (v/v). Representative aliquots of urine from individual animals were immediately stored in a freezer (−20 ◦ C) until analysed for N and allantoin. 2.5. Analytical methods Ground samples of feeds, refusals and faeces were analysed for DM, ash, and CP (AOAC, 1984), NDF, ADF and acid detergent lignin (ADL) (Van Soest et al., 1991). Mineral extracts of feed samples were prepared (AOAC, 1984) and analysed for Ca, Mg, K, Na, Zn, Fe, Cu and Mn after a wet digestion with a mixture of nitric, sulphuric and perchloric acids using an atomic absorption spectrophotometer (Unicam 919). Phosphorus in feed samples was determined colori-
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metrically, using molybdovanadate reagent (AOAC, 1984). Bulked samples of urine were analysed for Kjeldahl N (AOAC, 1984) or diluted (1/30) and allantoin was measured colorimetrically as described by Chen and Gomes (1992). The concept of the method is that allantoin is first hydrolysed under weak alkaline condition at 100 ◦ C, to allantoic acid which was also hydrolysed to urea and glyoxylic acid in a weak acid solution. The glyoxylic acid reacted with phenylhydrazine hydrochloride to produce a phenylhydrazone derivative of the acid. The product formed an unstable chromophore with potassium ferricyanide. The colour was read at 522 nm on a UV spectrophotometer (Spectronic 601).
Data were subjected to analysis of variance and statistical significance among treatment means was determined by Duncan’s multiple range test using GLM (general linear model) procedures of SAS (1987). The following contrasts were used to compare the mean effects of feed supplements: • S versus A: mean effect of soybean meal versus mean effect of atriplex; • B versus C: mean effect of barley grains versus mean effect of cactus. 3. Results 3.1. Feed characteristics
2.6. Calculations and statistical analysis Urinary excretion of allantoin (Y, mmol per day) was used to calculate microbial purines absorbed (X, mmol per day) from the equation: Y = 0.84X + (0.150W 0.75 e−0.25X ), where W is the animal live weight (kg). Microbial N supply (g per day) was calculated from the relationship: 70X/(0.83 × 0.116 × 1000), where 70 is the N content of purines (mg N/mmol), X is as defined above, 0.83 is the assumed digestibility of microbial purines, 0.116 is the ratio of purine N/total N in mixed rumen microbes and 1000 converts mg to g (Chen and Gomes, 1992).
Table 2 shows the composition of experimental feeds. Barley straw and cactus were lowest in CP. Both atriplex and cactus were high in ash. Cactus and atriplex were highest in Ca and Na, respectively. 3.2. Feed intake and daily gain (growth trial) Average intake of straw and diet (60 days) and live weight changes by lambs during the growth trial are given in Table 3. Straw DM intake was low among dietary treatments. Lowest consumption of straw was recorded on sheep given cactus. Replacing barley grains with cactus, and soybean meal with atriplex
Table 2 Chemical composition of feeds
Dry matter (g/kg) Organic matter (g/kg DM) Crude protein (g/kg DM) NDF (g/kg DM) ADF (g/kg DM) ADL (g/kg DM) Ca (g/kg DM) P (g/kg DM) Na (g/kg DM) K (g/kg DM) Mg (g/kg DM) Cu (mg/kg DM) Fe (mg/kg DM) Mn (mg/kg DM) Zn (mg/kg DM) a
Barley straw
Barley grain
Soybean meal
A. nummularia
O.F.I. f. inermisa
868 948 34 764 467 95 4.4 1.2 2.6 16.4 1.0 6.1 160.7 36.7 18.3
859 976 141 289 67 12 0.8 2.2 0.2 7.8 1.1 2.4 40.4 11.6 22.3
883 931 465 370 109 50 3.1 7.1 3.0 25.9 2.4 17.8 299.8 26.9 48.3
286 745 178 445 225 102 13.6 1.8 47.0 28.9 8.4 13.0 285.1 56.5 47.0
177 762 46 338 168 52 52.1 1.0 0.6 26.0 10.9 6.5 170.8 248.9 31.0
O.F.I. f. inermis: Opuntia ficus indica f. inermis (spineless cactus).
H. Ben Salem et al. / Small Ruminant Research 51 (2004) 65–73
69
Table 3 Feed intake and daily gain during the growth trial of Barbarine lambsa Basal diet: barley straw ad libitumb Barley soybean Dry matter intake (g per day) Straw 435 a Barley 178 Soybean meal 157 Atriplex – Cactus – Diet 770 d Daily gain (g) 108 a
S.E.M.
Barley atriplex
Cactus soybean
Cactus atriplex
399 b 178 – 378 – 955 c 59 c
262 c – 157 – 577 995 b 119 a
207 d – – 356 499 1062 a 81 b
3
5 2
Contrastsc S versus A
B versus C
∗∗∗
∗∗∗
∗∗∗
∗∗∗
∗∗∗
∗∗
Means in the same line with different letters are different (P < 0.05). Supplements: BS, barley soybean; BA, barley atriplex; CS, cactus soybean; CA, cactus atriplex. c S vesus A: average effect of soybean meal versus average effect of atriplex; B versus C: average effect of barley versus average effect of cactus. ∗∗ P < 0.01. ∗∗∗ P < 0.001. a
b
decreased straw intake (P < 0.05). However, total DM intake was higher in sheep given alternative supplements as compared to those receiving common concentrate feeds. All sheep gained weight. Association of soybean meal to either barley grains or cactus per-
formed the highest daily gain (108 and 119 g per day, respectively). Irrespective to the energy source (i.e. barley and cactus), replacing soybean meal by atriplex decreased growth rate. Lowest gain was obtained with BA diet.
Table 4 Feed and water intakes during the metabolism trial of Barbarine lambsa Basal diet: barley straw ad libitumb
DMI (g per day) Straw Barley Soybean meal Atriplex Cactus Diet DMI (g/kg W0.75 ) Straw Diet Water consumed Litre/kg DMI Litre/kg W0.75
S.E.M.
Barley soybean
Barley atriplex
Cactus soybean
Cactus atriplex
514 a 178 157 – – 849 d
469 b 178 – 486 – 1088 b
398 c – 157 – 618 1016 c
321 d – – 486 618 1375 a
43.6 a 72.1 d 3.05 a 0.219 b
42.8 a 99.4 b 2.92 a 0.290 a
33.4 b 85.2 c 1.30 b 0.111 c
28.8 c 123.0 a 1.50 b 0.183 b
S versus A
B versus C
6
∗∗∗
∗∗∗
6
∗∗∗
∗∗∗
∗
∗∗∗
∗∗∗
∗∗∗
nsd
∗∗∗
0.5 0.8 0.07 0.006
Means in the same line with different letters are different (P < 0.05). Supplements: BS, barley soybean; BA, barley atriplex; CS, cactus soybean; CA, cactus atriplex. c Refer to Table 3 footnote. d Non-significant effect. ∗ P < 0.05. ∗∗∗ P < 0.001. a
b
Contrastsc
∗∗∗
∗∗∗
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H. Ben Salem et al. / Small Ruminant Research 51 (2004) 65–73
Table 5 Apparent digestibility and feeding value of diets in Barbarine lambsa Basal diet: barley straw ad libitumb Barley soybean
S.E.M.
Barley atriplex
Cactus soybean
Cactus atriplex
Diet digestibility (%) DM 67.1 b OM 69.5 b CP 72.7 NDF 68.3 b ADF 61.2 bc Cellulose 66.4 ab
68.1 68.2 71.3 68.2 59.9 64.5
66.6 71.0 71.2 68.8 65.7 76.9
72.1 75.4 72.8 73.5 70.3 75.2
Intake (g/kg W0.75 ) Digestible OM Digestible CP
64.0 b 7.9 a
47.5 d 7.2 b
b b b c c
b b b b a
59.0 c 6.9 b
a a
0.4 0.4 0.5 0.5 0.7 1.3
a a ab
74.7 a 7.8 a
Contrastsc S versus A
B versus C
∗∗
nsd
ns ns ∗
ns ns
0.5 0.1
∗∗∗
ns ∗
∗∗∗ ∗∗
∗∗∗
∗∗∗
∗∗∗
ns
Means in the same line with different letters are different (P < 0.05). Supplements: BS, barley soybean; BA, barley atriplex; CS, cactus soybean; CA, cactus atriplex. c Refer to Table 3 footnote. d Non-significant effect. ∗ P < 0.05. ∗∗ P < 0.01. ∗∗∗ P < 0.001. a
b
3.3. Feed intake and diet digestibility (metabolism trial)
soybean meal by atriplex increased water consumption, expressed as litre per kilogram metabolic weight, by sheep (P < 0.001). Table 5 reports apparent digestibility of diets. All dietary treatments exhibited similar CP digestibility, which was above 70%. Supply of cactus and atriplex resulted in the highest DM, OM, NDF and ADF digestibility of the diet. Replacing soybean meal by atriplex had no effect on nutrient digestibility. Intake of digestible OM increased when common supplements
Feed and water intakes are given in Table 4. Irrespective of supplements, DM intake of barley straw was low (29–44 g/kg W0.75 ). Similarly to the growth trial, replacing barley grains with cactus decreased straw intake, the lowest straw intake was obtained with the CA diet. Lambs given cactus consumed less water than those on cactus-free diets (P < 0.05). Replacing Table 6 Nitrogen balance and microbial synthesis in Barbarine lambsa Basal diet: barley straw ad libitumb
N intake (g per day) Faecal N (g per day) Urinary N (g per day) Retained N (g per day) Urinary allantoin (mg/kg W0.75 ) Microbial N (g/kg DOMI)e
S.E.M.
Barley soybean
Barley atriplex
Cactus soybean
Cactus atriplex
18.7 5.1 4.2 9.4 32.0 3.5
18.7 5.6 5.6 7.5 28.4 3.2
20.0 5.8 4.7 9.5 48.3 8.3
20.7 4.7 3.8 12.2 56.7 11.4
c ab b b b b
c a a c b b
b a ab b a a
a b b a a a
Means in the same line with different letters are different (P < 0.05). Supplements: BS, barley soybean; BA, barley atriplex; CS, cactus soybean; CA, cactus atriplex. c Refer to Table 3 footnote. d Non-significant effect (P > 0.05). e Microbial nitrogen supply expressed as g/kg digestible organic matter intake (DOMI). ∗ P < 0.05. ∗∗∗ P < 0.001. a
b
Contrastsc S versus A
0.06 0.10 0.18 0.16 4.1 1.2
B versus C
∗
∗∗∗
nsd ns ns ns ns
ns ns
∗∗∗ ∗∗∗ ∗∗∗
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(barley grains and soybean meal) were replaced with cactus and/or atriplex. Digestible CP intake was not changed with cactus provision. Atriplex supplemented diets (BA and CA) exhibited the highest digestible CP intake. 3.4. Nitrogen balance and microbial synthesis N balance and microbial N supply are given in Table 6. Sheep receiving barley grains with soybean meal or atriplex consumed the same amount of N. However, N intake was highest when straw was supplemented with cactus combined with soybean meal or atriplex. There was no specific variation of N loss either in faeces or urine among dietary treatments. The increase of N losses in sheep receiving barley and atriplex as compared to those on BS was offset when cactus replaced barley grains and combined with soybean meal or atriplex. N retention was high among the four diets. Simultaneous supply of cactus and atriplex resulted in the highest N retention. Within an energy source (barley grains or cactus) allantoin excretion was similar for soybean meal and atriplex supplemented diet (P > 0.05). Urine of lambs receiving cactus contained substantially high amount of allantoin than those given barley grains (P < 0.001). The same trend was noted for the efficiency of microbial N supply.
4. Discussion There is a battery of information on how classic concentrate feeds (barley, soybean and rapeseed meals, wheat bran, mixed concentrate feeds, etc.) affect animal response on low quality roughages (Doyle et al., 1988; Chen et al., 1992; Dixon and Egan, 2000). However, very little is known about the replacement value of shrub foliage for these concentrate feeds and how intake, digestion and sheep performance are affected. The limited and irregular availability of common concentrate feeds and their high cost are considered by smallholders among the main problems for the development of the livestock sector. Having suitable shrub plantations that withstand harsh conditions and improve livestock performance without great need for concentrate feeds is a challenging option for farmers.
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Data reported in the current work and in our previous studies (Ben Salem et al., 2002a,b,c) showed that the contribution of common roughages and concentrate feeds in sheep diets could be reduced through the use of cactus pads and saltbushes (atriplex) without any detrimental effect on sheep growth. In this study, replacing barley grains and/or soybean meal by cactus and/or atriplex, respectively, decreased straw intake in the growth and metabolism trials. In agreement with Dixon and Egan (2000), this trend may be the result of substitutive effects. Crude protein in soybean meal was about 2.6 times that in atriplex foliage and ME in barley grains was about 1.5 times that in cactus pads. Moreover, cactus was substantially lower in DM than barley grains. Therefore, to have diets balanced for energy and N, great amounts of alternative supplements have to be distributed to animals. Therefore, cactus- and/or atriplex-containing diets would be bulky as compared to BS diet. Even though, this study denotes the lack of negative effect of cactus and/or atriplex provision on diet digestibility, which remained as high as that of the control diet (i.e. supplemented with barley grains and soybean meal). Diet containing both cactus and atriplex exhibited highest apparent digestibility of OM, NDF and ADF. The complementary role of these two range species in sheep feeding was demonstrated earlier by Ben Salem et al. (2002a,b) and reviewed by Ben Salem et al. (2002c) and Nefzaoui and Ben Salem (2002). Salt present in high level in atriplex foliage could be diluted by the high amount of water stocked in cactus pads. Moreover, atriplex may overcome N and fibre deficit in cactus while the latter plant species provides energy in the form of soluble carbohydrates. Owing to its low DM content and richness in soluble carbohydrates, one would expect cactus to have a similar effect than molasses on straw intake and digestion in sheep. However, this hypothesis was rejected by Ben Salem et al. (1996). These authors showed that provision of graded levels of spineless cactus (0, 150, 300, 450 and 600 g DM) for sheep did not decrease straw intake, increased the amount of digestible OM and CP intakes and improved rumen fermentation. In contrast to the classic effect of molasses, rumen pH was not decreased with cactus supply. The abundance of mucilage and mineral salts in cactus pads may enhance salivation, thus maintain pH in the normal range (6.5–7).
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Variation of N balance among dietary treatments is likely the result of the different amounts of N consumed by lambs since there was no consistent trend of N losses either in faeces or urine. Our findings suggested that cactus-containing diets promoted microbial activity better than those on barley-containing diets. This trend is reinforced with urinary excretion of allantoin and consequently with microbial N supply. This is likely the result of increased amount of DOMI rather than to the type of supplement per se. It is well documented that in the presence of adequate protein in the diet the amount of N synthesised by micro-organisms increases with the level of energy supplied (Chen et al., 1992; Balcells et al., 1993). Of particular interest is the similar amount of allantoin in urine and the level of microbial N obtained in lambs given barley grains with soybean meal or atriplex. On the basis of AFRC (1993) equation (ME intake MJ per day = 0.0157 × DOMI), the ME intakes of lambs on diets BS, BA, CS and CA were 8.77, 10.99, 11.07 and 13.0 MJ per day, respectively. According to the daily maintenance allowance of ME for growing sheep (live weight 20 kg) estimated to 3.8 MJ (McDonald et al., 1981), it is clear that sheep on the four dietary treatments had sufficiently high intakes to meet ME requirements for maintenance and gain, which was above 50 g per day. Diets were balanced not only for energy and N but also for Ca and P. Irrespective to the energy source, lambs given soybean meal performed better than those receiving atriplex. Although they were expected to consume the same amount of N, differences in the quality of N in these feeds may account for this trend. Ben Salem et al. (2002a) showed that about 70% of total N in atriplex foliage was in the soluble form, therefore and in contrast to soybean meal, the amount of true protein and by-pass protein should be low in atriplex. One adverse consequence of supplying the rumen with more than optimal concentrations of ammonia-N is the energetic inefficiency incurred in converting ammonia to urea for excretion. The advantage of supplying adequate energy and protein is shown in the BS diet, which had a high BW gain. This observation can be attributed to the type of protein and its degradability and also possibly to the lack of synchrony between N release through protein degradation and energy availability. This results in reduced efficiency of rumen ammonia utilisation by the microbes leading to excess ammonia
being absorbed into the blood stream and lost in urine as urea, which is consistent with the increased urinary N excretions by animals on BA. Increased daily gain in sheep given CA as compared to those on BA may be the result of synchronised supply of energy as sugar from cactus and N from atriplex. Moreover, cactus intake may have contributed to a continued dilution and excretion of salt in atriplex foliage.
5. Conclusions Under West Asia and North Africa conditions a wide variety of shrub species offers an economical alternative to costly energy and protein supplements. This should encourage widespread introduction of shrub and tree species for eco-regeneration and as nutrient-rich fodder in waste lands. The pattern of growth and nutrient utilisation observed in this study indicates that supplementation of poor quality roughages with spineless cactus and atriplex had a positive impact on sheep gain, and more interestingly that these browse species may reduce the use of costly concentrate feeds, thus alleviate feeding cost. Association of soybean meal with cactus instead of barley resulted in highest growth rate (ca. 120 g per day), and diet cost should be considerably decreased as compared to barley–soybean meal combination (ca. 110 g per day). The farmer could be satisfied by a daily gain of 80 g when common concentrate feeds (i.e. barley and soybean meal) are totally removed from the diet of lambs and replaced by cactus and atriplex, provided that these range species provide similar amounts of energy and N as by barley grains and soybean meal.
Acknowledgements This work was conducted with the financial support of ‘Secrétariat d’Etat à la Recherche Scientifique et à la Technologie (SERST-Tunisie)’ and the Pasture and Livestock Agency (Office de l’Elevage et des Pˆaturages-Tunisie). References Agricultural Food and Research Council (AFRC), 1993. Energy and protein requirements of ruminants. An Advisory Manual
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