Livestock Research for Rural Development 20 (11) 2008 Guide for preparation of papers LRRD News

Citation of this paper

Productive response of tropical lambs reared in two contrasting management systems after weaning and using woody forage species

E González-García*,**, J Arece**, H Archimède*, P P Gomarín** and O Cáceres** 

 *INRA UR143 Unité de Recherches Zootechniques, Centre INRA-Antilles-Guyane, Domain Duclos, 97170 Petit Bourg, Guadeloupe (French West Indies)

eliel.gonzalez@antilles.inra.fr   or   elggar@hotmail.com

  harry.archimede@antilles.inra.fr

** Estación Experimental de Pastos y Forrajes “Indio Hatuey”, Central España Republicana, C.P. 44280, Matanzas, Cuba

javier.arece@indio.atenas.inf.cu

Abstract 

A silvopastoral grazing system (SP) was compared with confinement (CF) to determine the growth and general performance of weaned Pelibuey lambs under experimental conditions. Animals were from the Experiment Station “Indio Hatuey” flock of Matanzas, Cuba. The trial began with weaning in March and April at 4 months after lambing, with the lambs weighing around 13 kg, and lasted for 125 days. After being drenched with Levamisol, 25 lambs were grown on the SP with 18 to 21 lambs/ha, and 25 lambs were grown in CF. A rustic shed was used for CF with 1.5 to 1.8 m2 per animal. The CF lambs were fed cut and carried chopped forage (60% Pennisetum purpureum, 40% Morus alba), and dehydrated citrus pulp at 0.8 to 1.0 kg/lamb per day was offered as supplement in both treatments. The nutritive value of the woody forage species established in both systems was determined with the French expression system. Data were analyzed by Proc Mixed procedure of SAS.

 

For the whole experimental period differences (P< 0.001) were obtained for average daily gain and incidence of gastrointestinal parasitism, mainly from Haemonchus contortus (2117 vs. 144 EPG of faeces) for SP and CF feeding systems, respectively. Lambs from CF (88.5 vs. 48.2 g/d) and males (77.8 vs. 58.9 g/d) exceeded SP and females in daily weight gains. Morbidity rate was explicitly higher in SP, and consequently, the survival level was better under CF experimental conditions (8% mortality in SP vs. 0% in CF). Advantages of the CF feeding system were mainly related to the reduced helminthiasis, which influences feed intake and efficiency, morbidity, growth rate, and survival rate as well.

 

Under the particular conditions of this experiment, these results suggest that CF of lambs, adopting integrative approach with rational use of natural and local resources, can be a good alternative for improving the growth and welfare of growing lambs in the tropics.

Key words: confinement, growth, lambs, parasitism, silvopastoral system, tropic


Introduction 

Sheep (and small ruminant) production is an important practice of many rural families in developing tropical countries where low input production systems are very often (Rajab et al 1992). Currently, the combined effects of high infestation in grasslands, strong negative impact of gastrointestinal parasitism (GIP) and anthelmintic resistance result in reduced animal productivity and farm profitability. This situation makes it necessary to find new alternative with little dependence on external inputs, in order to enhance flock productivity, farm profitability, and family economy, as well as to overcome anthelmintic resistance constraints.

 

The sheep production system in Cuba is based on grazing natural forages consisting of heterogeneous mixture of the locally so-called Bothriochloa-Dichantium complex and ‘sacacebo’ (Paspalum notatum) grasses, and, in some more intensive sheep exploitations (mostly for breeding), the establishment of improved grasses with higher nutritive value and DM yield per unit of area: e.g. guineagrass (Panicum maximum), bermudagrass (Cynodon dactylon), Jamaican stargrass (Cynodon nlemfuensis), Brachiarias (Brachiaria brizanta, Brachiaria decumbens, Brachiaria  mutica, Brachiaria rusiciniens) or Andropogon (Andropogon gayanus). However, in all cases, these grasses depend highly on the rainy season for forage production; therefore diet supplementation is required during the rest of the year.

 

Due to the scarcity of imported concentrates, the agroforestry/ agrosilvopastoral approach has been developed during the last two decades with the inclusion in the grasslands of multipurpose shrubs and trees (less affected by seasonal variation because they have deeper root systems) like leucaena (Leucaena leucocephala), ‘piñon florido’ or ‘mataratón’ (Gliricidia sepium), ‘algarrobo de olor’ (Albizia lebbeck), ‘casco de buey’ (Bauhinia purpurea), ‘piñón de pito’ (Erythrina poeppigiana / Erythrina verteroana), ‘nacedero’ (Trichantera gigantea) or ‘morera’ (Morus alba), along with the rational use of agro industrial by-products and non-conventional feeds. These systems have become interesting options for overcoming the shortage of forage during the drought and to increase the availability of high nutritive value feedstuffs at farm level. We hypothesized that a combination of this opportunity with different production systems (grazing, confining) could result in good options for small-medium scale sheep keepers.

 

Generally, local dry season has been found to be the worse period for sheep survival, mainly because of unbalanced feeding and the increase of infective larvae (L3) concentration in the pastures (Arece et al 2007) and, consequently, mortality rates by helminthosis. At present, this situation is determining more than 50 % of the success and profitability of the sector.

 

The main objective of this work was to evaluate the confined system for growing lambs, in the context of agrosilvopastoral sheep exploitation, as an alternative to the traditional grazing system, in a preliminary (experimental conditions) comparison with the silvopastoral system.

 

This confinement alternative include the development of a balanced feeding system in the same farm with an integrative approach, and the building of a rustic (low cost) shed, thus rationally exploiting local resources. A secondary objective was to assess the nutritive value of the woody forage species included into the systems.

 

Materials and methods

Experimental site, animals, management and design  

The experiment was conducted with Pelibuey lambs (n = 50) from the Experiment Station “Indio Hatuey” flock of Matanzas, Cuba (23°08’N, 82°23’E; 60 m above sea level). Means of monthly temperature and rainfall during this period were obtained from the Meteorological Centre of the unit and are presented in the Figure 1. 



Figure 1.  Average monthly temperature () and average monthly precipitation (black bars) of the experimental site


Temperature in the island has little seasonal variation, while the rainfall pattern divides the year into two distinct seasons: a rainy season that usually starts in May and ends in October, and a dry season that lasts the rest of the year. Hence, quantity and quality of the forages available for grazing vary according to the season and the distribution of the rainfall.

 

Ewes lambed in October and November and grazed at 12 to 14 per ha in a rotational silvopastoral system (SP) without irrigation or fertilization and composed of three grasses distributed by plots (Panicum maximum, PM; Brachiaria brizanta, BB; and Andropogon gayanus, AG) and three fodder trees (Leucaena leucocephala, LL; Albizia lebbeck, AL; and Bauhinia purpurea, BP) randomly distributed and associated in the 4.5 ha of pasture. Ewes were supplemented during the drought with dehydrated citrus pulp (DC) and sugarcane molasses containing 2% urea (MU).

 

The average body weight (BW) of lambs at birth was 3.11 kg (3.22 kg females vs. 3.00 kg males). Lambs were allowed restricted suckling by allowing them access to the mothers only during the mid-day (11.00 to 14.00 h) and at night. Average daily gain for this pre-experimental period was 80.4 g/d.

 

The trial began with weaning in March and April at 4 months after lambing, with lambs weighing an average of 12.31 kg (12.52 kg females vs. 12.11 kg males) and lasted  for 125 days. After being orally treated for internal parasites with Levamisol (doses recommended by the manufacturer: 7.5 mg kg-1 BW), 50 lambs were selected and distributed into two averagely uniform groups in a completely randomised design; 25 lambs were maintained as one group in pasture and were grown on the rotational SP described above with a stocking rate of 18 to 21 lambs/ha; the other group of 25 lambs were grown in CF in an elevated (floor at a height of 1.8 m from the ground) low cost rustic shed (walls, floor and roof built with local wood and palm tree) with 1.5 to 1.8 m2 per animal (see Plate 1).



Plate 1.
Rustic shed built with local wood and palm


The general dimensions and technical characteristics of the shed is in accordance with the archetype of the model proposed by Centro Agronómico de Investigación y Enseñanza (CATIE), Costa Rica, for small ruminant systems in small and medium scale farms with an agroforestal approach (Benavides et al 1995, Oviedo et al 1995). For data interpretation and analysis, animals in each of the two rearing systems (SP and CF) were subdivided into male (12 per treatment) and female (13 per treatment) subgroups. The two rearing systems were considered as main experimental treatments in order to compare the general performance of lambs after weaning under a low input production system approach.

 

In both systems, a balanced feeding was guaranteed and fresh water was given ad libitum. The CF lambs were fed cut and carried chopped forage (60% Pennisetum purpureum, PP; 40% Morus alba, MA) and DC at 0.8 to 1.0 kg/lamb/d, while SP lambs were managed in the rotational grazing system allowing browsing of forage (manually pruning of the foliage from the shrubs/ trees every day) and being stall supplemented with DC at the same rate as in CF.

 

The measured variables per treatment were: live body weight (BW) change and kinetic, ADG of lambs, faecal egg count (FEC) as an indicator of GIP infestation, morbidity and mortality rates. The chemical composition of the forages and feed used in both systems and the nutritive values (NV) of the woody forages species were also determined.  

In vivo nutritive value determination with the French unit system 

The NV of the woody forages species (LL, MA, AL and BP), without irrigation or fertilization, were determined for both the rainy and dry seasons of the year, prior to introduction of the animals by using the total faeces collection and ad libitum forage supply method adapted to tropical conditions (Garcia-Trujillo and Cáceres 1984, Xandé et al 1985, 1989). For each forage specie a NV determination with 21 d period (14 d for adaptation and 7 d for data collection) was carried out using six castrated Pelibuey wethers (average BW = 25 ± 1.8 kg) randomly allocated in individual metabolism crates. The forages (leaves and edible stem fractions) were manually pruned every morning. Forages were individually offered in two ad libitum meals a day (8.30 and 16.00 h) by providing a daily amount exceeding the previous day’s intake by at least 15-20%.

 

During the collection week, offered and refused forages were recorded daily to determine voluntary DM intake (VDMI). Nitrogen values were expressed in the protein digestible in the intestine (PDI) system from the French units, where the sources of protein digestible in the small intestine are estimated by (1) rumen undegraded dietary protein (PDIA), (2) microbial protein synthesized from rumen fermented organic matter (PDIME) and (3) microbial protein synthesized from degradable (PDIMN) (Xandé et al 1989).

 

The in vivo DM digestibility (DMD), the main criterion for the determination of nutritive values with the French system (Aumont et al 1995), the OM (OMD) and CP (CPD) digestibilities, also the composition on digestible CP (DCP), PDIME, PDIMN, and the metabolizable energy (ME) were determined and expressed in the French unit system. 

 Analytical procedures 

Samples of forages (offered and refused) were collected daily by duplicate and composited for each animal. The DM contents of forages (grasses, trees/shrubs), other feeds (DC, MU) and refusals (NV trials) were determined by oven drying at 105 ºC for 24 h. Total daily faeces were collected and weighed and a 10% representative sample per wether was retained. The faecal samples were composited for each animal and stored at –20 ºC until analysis.

 

Dry samples were ground to pass through a 1-mm screen stainless steel screen (Cyclotec 1093 Sample mill, Tecator) for analyses of DM and OM according to AOAC (1997). The CP content was calculated after N determination by Kjeldahl method by using a Kjeltec Auto 1030 Analyzer (Tecator, Hogänäs, Sweden). The methods of Van Soest et al (1991) were used to determine NDF and ADF on an ash-free basis using the Ankom200 Fibre Analyser incubator (Ankom Technology, Fairport, New York, USA) and adding amylase and sodium sulphite solutions. As using French NV system implies the use crude fibre (CF), this parameter was measured using the Weende method (Henneberg and Stohmann 1859). All analyses were performed by duplicate, and average values were used for calculations. 

Morbidity and mortality rates 

For the whole period of the experiment (125 d) all incident of diseases and death were individually recorded, with an identification of the symptoms and classification of pathologies for the calculations of morbidity rate of the flock in each rearing system. Morbidity and particular diseases were expressed as total average of incidence per month by the average monthly percentage of lambs affected from the total population (n = 25) in each treatment.

 

Mortality rates were calculated from weaning to the end of the experiment as the percentage rate of lambs that died during the given period on the basis of the total number of lambs at the beginning of the experiment. 

Faeces collection, faecal eggs counts (FEC) 

Gastrointestinal parasite egg count (faecal egg count, FEC) was determined in one point at the end of the experiment, according to the modified methodology reported by Arece et al (2007). The animals (n = 10 per treatment) were chosen randomly and samples were collected directly from the rectum of the lambs, kept in polyethylene bags to avoid contamination and transported to the laboratory in refrigerated vials. All samples were individually analyzed using a modified McMaster technique and FEC was expressed as the number of eggs/g faeces (EPG).

 

The faecal samples within the same flock were pooled and cultured for ten days at room temperature each month following the Roberts and O’Sullivan (1952) procedure to determine the most parasitic genera.  

Calculation and statistical analysis  

Individual lambs BW and ADG were recorded and calculated in 30 d intervals. BW change, ADG, morbidity, FEC and mortality rate were analyzed using the mixed procedures of SAS (PROCMIXED) (SAS 8.1; SAS Inst. Inc., Cary, NC; 1999) with a statistical model including rearing system, sex, and their interaction as fixed effects. Significance was declared at 5% of probability and comparisons between means were tested by the LSmeans procedure.

 

Results and discussion 

Chemical composition of forages and feeds used and in vivo nutritive value of woody fodder species  

The average chemical composition of the feed samples used during the 125 d of evaluation is given in Table 1.


Table 1.  Average chemical composition of the forages and feeds used in the experiment

 

Item

Forage specie/ supplement

PM1

PP2

BB3

AG4

LL5

MA6

AL7

BP8

DC9

MU0

DM content, %

25.6

22.0

22.3

21.0

31.0

24.2

51.2

33.4

88.0

81.2

Composition, %

 

 

 

 

 

 

 

 

 

 

OM

90.1

89.3

92.1

91.8

90.2

90.2

91.8

89.6

92.5

92.8

CP

5.9

7.6

5.5

7.7

19.0

21.1

22.1

12.1

7.7

3.7

NDF

52.1

53.0

78.0

43.5

22.7

32.9

61.3

46.2

24.0

-

ADF

37.7

33.7

46.8

21.5

16.7

21.1

46.4

31.5

17.5

-

1PM, Panicum maximum cv. Likoni

2PP, Pennisetum purpureum

 3BB, Brachiaria brizantha

 4AG, Andropogon gayanus

 5LL, Leucaena leucocephala

 6MA, Morus alba

 7AL, Albizia lebbeck

 8BP, Bauhinia purpurea

 9DC, Dehydrated citrus pulp

 0MU, Sugarcane molasse - 2% urea


Overall, the quality of grasses (PM, BB and AG) established in SP responded to the approach of low input system (zero irrigation and fertilization) with CP, NDF and ADF levels ranging 55–77, 435–780, and 215–468 g kg-1 DM, respectively. Composition of fodder trees (LL, AL and BP) from SP system was characterised by a high level of CP (180-190 g kg-1 DM) and irregular percentages of the cell wall components depending on the specie.

 

In general, the forage composition of woody species falls within the range of values reported in previous evaluations of agrosilvopastoral systems under Cuban conditions (Cáceres et al 1996, González and Caceres 2002 and González et al 2006) while grasses were, in average, less CP and more NDF and ADF concentrated than values found by Xandé et al (1985) and Aumont et al (1995) for Caribbean conditions.

 

The association of grasses and fodder trees in SP increased the possibilities for heat tolerance and feeding balance of animals, and the fodder tree foliages could also improve the utilization of the low quality roughages (Singh et al 1989, Topps 1992).

 

The forage banks of PP and MA in CF system were organic fertilized with the manure from lambs collected in the rustic shed. This integrated approach allowed for a good quality of the grass (PP) and protein (MA) banks.

 

The chemical composition and the NV for woody fodder species in both year seasons is shown in Table 2. 

 


Table 2. Nutritive value of the forages from the woody fodder species used for lamb feeding, as affected by the year season

 

Forage species

LL1

MA2

AL3

BP4

R5

D6

R

D

R

D

R

D

DM content (%)

30.8

30.1

26.2

28.1

25.1

29.3

28.3

33.2

Composition (%)

OM

91.2

91.1

92.1

91.8

92.9

93.3

89.0

89.7

CP

17.8

24.9

22.7

23.1

25.0

23.5

11.1

12.1

CF

19.0

16.8

15.3

14.2

32.1

32.7

29.4

28.1

NDF

35.0

31.8

34.3

32.5

52.3

53.1

54.3

52.2

ADF

25.9

23.5

22.0

20.8

39.8

40.4

36.9

35.5

ME7 (MJ kg-1DM)

8.6

9.2

10.2

10.1

8.9

9.0

7.9

8.1

Total tract digestibility (g kg-1DM)

 

 

DM

569

613

699

713

597

599

517

511

OM

589

625

792

751

617

620

559

557

CP

606

686

711

750

764

794

553

551

CF

662

569

681

672

574

523

462

450

Digestible CP (g kg-1DM)

108

171

161

174

191

187

  64

  67

PDIME8 (g kg-1DM)

  92

129

117

120

127

122

 57

 63

PDIMN9 (g kg-1DM)

105

147

134

136

149

139

 65

 71

VDMI10 (g kg-1BW.75)

  54.2

  57.5

  83.5

  81.9

  58.7

  47.0

 62.8

 72.8

1LL, Leucaena leucocephala,  2MA, Morus alba,  3AL, Albizia lebbeck, 4BP, Bauhinia purpurea,  5R, rainy season,  6D, dry season,  7ME, metabolizable energy,  8PDIME, microbial protein synthesized from rumen fermented organic matter,  9PDIMN, microbial protein synthesized from degradable, 10VDMI, voluntary DM intake


The DM content ranged between 25 and 33 %, which allow us to infer that this parameter would not limit DM intake in ruminant diets. In general, either the constituents from the cell content or from the cell wall content, as well as the digestibility of DM and OM seem to be unaffected by the year season; CP was considered high and averaged 191.5 ± 31 and 209 ± 30 g kg-1 DM for R and D season, respectively, the highest being for MA and AL forages (227-250 g kg-1 DM) and the lowest for BP (111-121 g kg-1 DM); the forages from LL showed to be more affected by the season with an increase from 178 to 249 g kg-1 DM. The NDF and ADF averaged 440 ± 54 and 311 ± 43, and 424 ± 59 and 300 ± 47 g kg-1 DM for R and D season, respectively; the more fibrous forages were AL and BP, while the metabolizable energy (ME) was not affected by the variability in fibre contents and ranged between 8.5 and 10 MJ kg-1 DM with few difference for season.

 

The total tract digestibility was ranging around 600 g kg-1DM, highlighting the excellent OMD and CPD in mulberry (MA); the lowest digestibility was obtained in BP and it was related with its relative low CP and digestible CP content and higher percentage of cell wall components. However, these parameters did not affect the VDMI of BP, which is falls within the average value of the evaluated forages (65 g/kg BW.75), demonstrating the good palatability of this plant; the worse voluntary intake was obtained in the AL forage which was even lower in D season (59 vs. 47 g/kg BW.75), probably because of the content in condensed tannins and other secondary compounds, while the best VDMI was found for mulberry (> 80 g/kg BW.75).

 

For both seasons there was an unbalance between PDIE and PDIN contents with higher values for PDIN which indicates the presence of important rates of non protein nitrogenous compounds (NPN) and, therefore, the necessity to balance these two fractions in the diet (Garcia-Trujillo and Cáceres 1984, Xandé et al 1985) with other local energy sources.

 

For tropical forages, digestibility is depressed and forage intake drops when CP content is lower than 80 g kg-1DM (Minson 1990), partly because nitrogen is insufficient to meet the needs of rumen bacteria. The CP concentration of the four species evaluated as well as the levels of DCP, PDIME and PDIMN suggest that these plants could effectively provide the N supplement for ruminants fed low N grasses or crop residues. Similar results were reported by Larbi et al (2005) evaluating the nutritive value of browse species in the West African humid tropics.

 

Live body weight (BW) change and average daily gain (ADG) performance

 

Post-weaning growth of lambs was significantly affected by the rearing system (P < 0.001) and sex (P < 0.05), also no significant sex × system interaction was found, and demonstrating that there was no influence of the system conditions in the superiority of males. Final BW from lambs reared in CF was significantly higher (P < 0.05) than those grown in SP (26.2 vs. 20.1 kg) because of a higher ADG (88.5 vs. 48.2 g/d for CF and SP lambs, respectively) (Table 3; Figure 2).


Table 3.  Effects of rearing system on growth rate of Pelibuey lambs

 

Silvopastoral

Confinement

 

Animal (no.)

25

25

 

BW (average, kg)

 

 

 

  Initial

12.7

12.7

0.96

  Final

20.1b

26.2a

2.08

  Change

7.4b

13.5a

0.18

BW (males, kg)

 

 

 

  Initial

12.5

12.5

0.71

  Final

21.3b

26.6a

1.62

  Change

8.8b

14.4a

0.10

BW (females, kg)

 

 

 

  Initial

12.9

12.9

1.15

  Final

18.8b

24.4a

2.77

  Change

5.9b

11.5a

0.10

ADG (g/d)

 

 

 

  Average

48.2b

88.5a

11.49

  Females

 38.6b

 74.8a

  9.76

  Males

 57.8b

 92.4a

13.56

a,b Item means within row with unlike letters differ significantly (P < 0.05). Values are least squares means




Figure 2.  Evolution of live body weight (BW) of lambs reared under silvopastoral or
confinement conditions.
Each point, after weaning, represents the mean of 25 observations
(Silvopastoral system (SP, ○), SE = 1.1; Confinement system (CF, □), SE = 1.86)


As expected, male lambs exceeded (P < 0.05) females in ADG (77.8 vs. 58.9 g/d), although this difference was decreasing with maturity (Figure 3), the final BW was also significantly (P < 0.05) affected (24.0 vs. 21.6 kg) (Table 3). Thus, mature BW for males was 1.11 times the one estimated for females, which is in accordance with the classic reported ratio of 1.3 times (Hammond 1932).


 

Figure 3. Evolution of average daily gain (ADG) of lambs reared under silvopastoral or confinement conditions, as affected by sex. Each point, after weaning, represents the mean of 12 or 13 observations for males (M) and females (F), respectively (SP: Silvopastoral system, CF: Confinement system).

In general, male lambs have been reported to grow at a faster rate than females, although in our case females were heavier at the beginning of the experiment (12.9 kg vs. 12.5 kg males), probably because most of them were single-born. These findings are consistent with the obtained by Rosa et al (2007) evaluating Romney Marsh and Merino Branco sheep in the Azores islands and with those of Rajab et al (1992) in a study conducted at the north-eastern region of Brazil with three tropical hair sheep breeds, in which sex of lambs contributed significantly to the variability of lamb growth and males outweighed females for all the weight traits. Such a trend in the effect of sex on BW might be attributed to different physiological functions in the two sexes, mainly of hormonal mediation, that tend to become more pronounced as animals approach sexual maturity.

 

Although the growth rate in SP system was considered modest (48.2 g/d) and behaved much below the productive potential of the breed (90-120 g/d, depending on environmental factors), the average growth rate obtained in this experiment can be considered as acceptable for Pelibuey breed under low input production systems conditions, without using concentrate supplementation.

 

The superiority of CF was probably related to the higher energy expenditure of SP lambs by walking, and the concomitant higher incidence of helminthosis, contagious ecthyma and lameness affectations (Table 4).


Table 4.  Disease incidences in Pelibuey lambs reared in two contrasting system during four months after weaning

Item

Treatment

SP1

CF2

Animal, No

Morbidity, average month-1; %

Contagious ecthyma, average month-1; %

Lameness, average month-1; %

  Footrot

  Arthritis

Helminthosis

  FEC3 (EPG4 of faeces)

Mortality (%)

25

9.0 (36.0)a

3.2 (12.8)a

 

5.8 (23.2)a

0b

 

2117b

8b

25

2.0 (8.0)b

1.2 (4.8)b

 

0b

0.8 (3.2)a

 

144a

0a

a,bItem means within row with unlike letters differ significantly (P < 0.05). Values are least squares means

1SP, Silvopastoral system

2CF, Confinement system

3FEC, fecal egg count

4EPG, eggs per gram


We can assume that better comfort and more controlled conditions in CF system contributed significantly to avoiding the stress during the transition of lambs from the lactating to the herbivorous phase (Figure 3), normally manifested under grazing conditions and responsible for the depressed immunity and higher rates of morbidity and mortality in the growing lambs.

 

Pedraza et al (1995) in an experiment with weaned Pelibuey lambs in Cuba obtained similar average growth rates to those found in our study for CF system, but using ‘B’ molasses given ad libitum, Digitaria decumbens hay sprinkled with urea-molasses solution and three supplements with high inclusion of sugar cane by-products (Saccharina: sun dried filter cake: brown sugar sweepings). Similarly, ADG for lamb’s hair breeds in tropics ranged between 100-130 g/d when high amount of imported concentrates and irrigated and fertilized pastures were used (Cáceres et al 1996, Mahieu et al 1997, Anindo et al 1998, Pineda et al 1998, Doloksaribu et al 2000, Ortega-Jiménez et al 2005)

 

At present, there is a vast available literature which demonstrate the potential of tree/shrubs fodder use for sustainable sheep production in the tropics and to which our results are consistent (Eswara and Raj 1991, Jegou et al 1994, Jiménez et al 1998, Rios et al 2000, Sánchez 2000, Yao et al 2000).  

Morbidity 

To devise cost-effective disease control programmes, it is important to consider the influences of ecoclimatic factors and management of disease frequency (Kusiluka et al 1998). The incidence of diseases and mortality for lambs reared in both systems is shown in Table 4.

Endoparasitism was found to be common in both management systems, although its prevalence was lower in CF. Other disease incidences were footrot (FR) and contagious ecthyma (CE), and minor signs of arthritis (AT). Incidence of FR and CE were significantly higher (P < 0.05) in lambs grazing on SP than those grown in CF (Table 4). In contrast, the few cases detected with minor trend of AT were found in CF, probably because of the hardness of the floor in the rustic shed.

 

CE is a viral disease of sheep and goat (wild and domestic) being  susceptible every breed and age, although more the young animals. In humid tropics it is common to find in sheep and goats under grazing conditions; scabby lesions of this disease are most commonly found on the lips, skin of the face, udder, within the mouth and above the hooves (Robinson  and Kerr 2001).

 

In our experiment, lambs became infected (mainly on the lips) from the suckling period probably because of contamination with the dirty udder of the mothers. The change to a more ventilated, sun dried and isolated environment, with improved management conditions and hygiene of the animals (CF), allowed for their quick recovery; whereas lambs that continued on grazing (SP) without intervention became even worse in the first period after weaning.

 

FR is a specific contagious disease of the feet of ruminants which has been the focus of extensive investigation in many parts of the world especially in Australia, New Zealand, the United Kingdom, Nepal, Malaysia and India (Wani and Samanta 2006). This pathogen requires warm and moist conditions for multiplication, which was obtainable in our setting.

 

Despite its worldwide distribution, FR has a significant impact in those sheep-farming countries that have temperate climates and moderate to high rainfall, such as Australia and New Zealand (Stewart 1989). In this country, ovine FR remains the most important cause of lameness in sheep flocks, despite the existence of proven methods for the control of the disease (Abbott and Lewis 2005).

 

Under Cuban conditions, FR currently increases with the humidity and temperature during the rainy season being responsible for significant economic losses; the most susceptible animals are those from the young categories because of the tenderness of the hooves; this situation is aggravated under grazing conditions, and without a good management of the time schedule during the day (i.e. avoiding the contact with the dew so early in the morning) (González-García et al, unpublished data). The high prevalence of FR observed in lambs grown in SP demonstrates this situation (Table 4). The more direct effect was a decreased movement capacity of lambs for grazing, and consequently, the difficulties of fitting the nutrient requirements and expressing the productive potential. 

Faecal egg count (FEC) 

Although Latin America as a region has quite a substantial number of sheep and is among the largest consumers of broad-spectrum anthelmintics on a per capita livestock basis, notwithstanding, very little study is known to have been carried out on control of internal parasitism in this region. (Waller et al 1996, Waller 2006).

 

At the same period of this experiment, a deeper analysis of the GIP trends, nematode infestation and genera present was concurrently carried out with the same flock and has been  published by Arece et al (2004, 2007); they found that animals were positive to strongyle infection throughout the year but the highest infestation values were present in the dry season; animals were mainly affected by Haemonchus spp. and to a lesser extent by Trichostrongylus colubriformis and Oesophagostomum columbianum.

 

In the post weaning stage of our experiment, a significant difference (P < 0.001) (Table 4) was found between treatments: 2 117 vs. 144 EPG in SP and CF lambs, respectively. This marked difference could be due to the absence of a direct contact with the L3 contaminated grasses and forages in CF unlike in the SP; this high survival and dynamics of L3 in similar grassland system was also described by Arece et al (2007). Waller (2006) reflected on the possibilities of GIP control through grazing management strategies and biological control. Knowing that for small farmers in the tropics, with production systems that rely basically on local resources and low external input levels, even a good grazing management may sometimes become complicated as it is dependent on land availability, stocking rates, good fencing systems (e. g. the solar powered used in the referred 10 paddock system), and the use of anthelmintics treatment in the early part of the grazing season, which remains an important practice in the preventive strategy (Michel 1985). It is in these circumstances, and for other critical moments, that we consider it a good productive option to combine the confinement of the more susceptible animal categories of the flock with the grazing of the lesser affected (generally adults), being aware that good feeding is essential for animals to remain productive. Our results demonstrated that, in the fight against internal parasitism infection and even with a low input perspective, sheep production in the tropics can be intensified.

 

In addition, confinement allowed for a kind of biological control of nematode parasites with the practice of dung collection, used as organic fertilizer in the forage banks of PP and MA, thus breaking the life cycle of parasites. 

Mortality 

In terms of reproductive wastage, lamb losses represent a serious problem because all investments made for ewes to conceive and maintain pregnancy are wasted (Mukasa-Mugerwa  and Lahlou-Kassi 1995). Losses are particularly high in lambs of around 2.0 kg at birth, most of which die within 24 h of delivery due to starvation/mismothering and exposure (the SME syndrome). Pre weaning lamb mortality averaged around 15% over the period of this study. It was observed that, in contrast to CF lambs, grazing in SP alone showed an 8 % of post weaning mortality; the ‘zero’ mortality obtained in CF system was related to the favourable general comfort conditions of animals and the decrease of infection by GIP, FR and CE when compared to grazing lambs (Table 4).

 

Pre weaning mortality rate of lambs ranging between 9.9 to 18.1 % and 90 % occurring from birth to 7 days postpartum has been reported under intensive grazing management and reproductive rates in Martinique hair breed in Guadeloupe (Ortega-Jiménez et al 2005), while Rosa et al (2007) obtained an average of 18% in Romney Marsh and Merino Branco sheep and Casellas et al (2007) found a preslaughter overall mortality from birth of 9.6% in 1,487 Ripollesa lambs.

 

Conclusions 

 

Acknowledgements 

We wish to thank the technical team of the Experimental Station ‘Indio Hatuey’, Matanzas, Cuba, for the field and laboratory work during the years of this investigation. This study was partly supported by the Research Project FIC No 98/102 in collaboration with the Unité de Recherches Zootechniques (URZ), INRA-Centre Antilles-Guyane, Guadeloupe, France.

 

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Received 7 July 2008; Accepted 18 September 2008; Published 6 November 2008

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