Growth and carcass characteristics of Moroccan INRA180 lambs

M El Fadili

Department of Animal Production, National Institute of Agronomic Research,
B.P. 415, 10060, Rabat, Morocco
elfadili.moussa@yahoo.com

Abstract

Growth and carcass characteristics were evaluated on 82 lambs of both sex of the INRA180 breed from 2007 to 2010. This Moroccan new synthetic breed was created from the Timahdite and D’man parental local breeds which contribute each with 50% of genes. The development and ewe performances and lamb pre-weaning traits of the INRA180 new breed were reported in a previous paper.

During the fattening period of 45 days, the INRA180 lambs had average daily gain (ADG) of 247 g/day and a feed conversion index of 5.00. At the averaged slaughtering age of 170 days, the INRA180 lambs weighed 30.8 and 15.92 kg respectively for slaughter and carcass weight and showed a dressing percentage of 51.6%. Furthermore, the INRA180 lambs deposited 603 g and 3.24 mm, respectively, for mesenteric fat and back fat thickness. In addition, the conformation score was 3.43 and longissimus dorsi muscle area 10.1 cm².

These results indicated that the infusion of 50% of the prolific D’man genes into the INRA180 lambs did not affect post-weaning growth and carcass traits. INRA180 promise a high potential genetic merit in purebred or maternal breed in terminal crossing for increasing sheep flocks productivity and for improving red meat production in the agricultural production system in Morocco.

Keywords: growth, conformation, D’man, fat, sheep, synthetic, Timahdite

Introduction

In Morocco, crossbreeding is one possible way to improve prolificacy and productivity of local breed flocks of sheep.  Furthermore, increasing the number of lambs marketed per ewe and per year is a major way to improve the efficiency of the sheep meat production.

The National Institute and Agricultural Research (INRA) of Morocco developed a new synthetic breed from the non prolific Timahdite and prolific D’man local breeds. This new breed, INRA180, might be suitable for farmers who need to intensify lambs’ production in agricultural land. In previous papers, the ewe reproductive performances and lambs pre-weaning growth for the INRA180 breed under the INRA El Koudia experimental station conditions (El Fadili 2011a) and under private farmer conditions (El Fadili 2011b) were reported.

Information on post-weaning growth and carcass traits of the other local Moroccan breeds (Timahdite, D’man, Boujâad, BeniGuil and Sardi) is well documented in our previous publications (El Fadili and Leroy 2000, El Fadili 2001, El Fadili el al 2001, El Fadili 2004, El Fadili 2006, El Fadili 2009). The present paper aims to measure growth and carcass traits of INRA180 lambs.

Materials and methods

Management and control

Details on management and feeding conditions during pre-weaning growth period are described in a previous paper (El Fadili 2011a). During post-weaning, 82 weaned lambs witch weighted 23.7 kg were chosen randomly from a total of 659 lambs reared and were fattened according to sex during an average period of 45 days. The lambs were given free access to a finishing mixed diet of hay (10%) and concentrate (90%). The concentrate was composed of barley and triticale grains (40%), sunflower meal (14%), minerals and vitamins (1%), and a commercial pelted feed (45%).

The lambs were weighed individually two times at the start and twice again at the end of fattening period. The average of the two weighings was used to calculate fattening daily gain. Daily feed intake was weighed and refusal recorded. Average daily gain, daily dry matter intake, and feed conversion efficiency (kg feed intake per kg live body gain) were computed.

The afternoon prior to slaughter, lambs were transported to the commercial abattoir of Rabat, where they were weighed after an 18 hour fasting period, without access to feed and water. Lambs were slaughtered at an average age of 170 days and a final weight of 34.5 kg.

The warm carcass weight was obtained within one hour after slaughtering. The mesenteric fat was removed and weighed. Then, the carcass were chilled at 4°C for approximately 24 hours, and the following measurements were taken on the entire cold carcasses: carcass length, carcass width, leg length, back fat thickness taken at the 13^th rib in the left side from 4 cm of the spinal column. Cold carcass was visually assessed for conformation score using a scoring method (1 to 5 point scales) applied to this type of light carcass (Colomer-Rocher 1986). The scoring for conformation was from 1 (very poor conformation) to 5 (very good conformation).

A sample of 72 cold carcasses were randomly selected and cut at the 13^th rib to determine area of the muscle longissimus dorsi measured by tracing an outline of the cross-selection of the longissimus dorsi from the left sides of the carcass on a piece of acetate. The following traits were calculated from some of the objective measurements: dressing percentage =100* cold carcass weight/slaughter weight and carcass compactness =100*cold carcass width/carcass length.

Statistical analysis

Statistical analyses were performed using the GLM procedure (Statistical Analysis System Institute 2000). The final general linear models used to analyze fattening and carcass traits included fixed effects of sex of lambs (male, female), lambs rearing type (single, twin and more) and lambs year of birth (2007, 2008, 2009, 2010).  

Results and discussion

The objectives of this study were to evaluate performances of INRA180 lambs and the influence of sex, number at parturition and year of birth on average daily gain (ADG), feed intake and conversion at fattening and carcass traits.

Fattening traits

The results showed that all factors studied affected lamb fattening traits (Table 1). These effects were observed by (El Fadili et al 2001) when compared in the same conditions of management Timahdite, D’man purebreds and crosses lambs. The estimate values ranged from 196 to 256 for ADG, 1.14 to 1.30 for DM intake and from 5.27 to 6.14 for feed conversion.

In a another previous study, ADG were 196 g/d, DM intake 1.12 kg and conversion index 5.25 for Boujaad breed (El Fadili 2004), and 193, 196 and 208 g/d respectively for D’man, Sardi and Timahdite breeds for ADG (El Fadili et al 1998). Our results (Table 1) are also within the range of those obtained by Boujenane et al (2003) who reported average values of fattening traits in lambs of other Moroccan synthetic breed (DS) of 221 g/day and 7.09 respectively for ADG at fattening and feed efficiency.

Male lambs were 11% heavier, grew 28% faster, showed 13% greater DM intake and 18% beter feed conversion than female lambs. Similar values were reported between male and female lambs from Boujaad local breed, when compared to purebred animals (El Fadili 2004). The differences between the two sexes were -6, -2 and +7%, respectively for ADG, DM intake and feed conversion for purebred and crossed lambs (El Fadili et al 2001).

During fattening period, Singles lambs were 10% heavier, grew faster (13%), 5% greater in DM intake and 9% slower feed conversion than multiples birth lambs (Table 1). These differences between single and multiples birth lambs were also observed in previous studies (El Fadili et al 2001; El Fadili 2004).  

Year of birth had an effect (P < 0.01) on finishing final weight, growth daily gain and food conversion index, but no effect P > 0.05) on dry matter intake (Table 1). Similar observations were reported by El Fadili (2004) who also observed an effect of year of birth on all fattening traits of the Boujaad breed and crossbred lambs sired by meat improved breeds.

Slaughter performances and carcasses fat deposit

The LS means of slaughter performances and carcasses fat deposit of the INRA180 lambs and the fixed effects are reported in Table 2. These values were in range to those observed by El Fadili (2000, 2004) for local lambs of Timahdite, D’man and Boujâad breed of sheep. Furthermore,  Boujenane et al (2003) reported values of 34.0 kg, 16.1 kg, 47.1% and 144 g respectively for slaughtering weight, hot carcass weight, dressing and kidney fat for the DS synthetic lambs breed. This author observed also that the DS lambs deposit significantly (P <0.05) more kidney fat when compared to the Sardi (99 g) and D’man (116 g) breeds.

Results of El Fadili (2004), Boujenane et al (1990) and El Fadili et al (2001) showed that D’man lambs deposed more internal fat than purebred lambs of the local breeds (Sardi, Timahdite, Boujâad) or crossbred lambs sired by meat improved sires of Ile de France and Merinos Précoce.  El Fadili et al (2001) also reported that first crosses lambs (D’man x Timahdite) had more internal mesenteric fat than purebred Timahdite local lambs, but they deposited less mesenteric fat when compared to lambs born from D’man  breeds. Indeed, D’man and Timahdite lambs had thinner back fat compared with those sired by meat improved sire breeds that had deposit more subcutaneous fat.

Furthermore, prolific breeds, such as Romanov and Finnsheep and their crosses, also show a tendency to deposit higher proportion of internal fat and lower proportion of back fat than non-prolific breeds (Ricordeau et al 1990; Greeff 1992; Borys and Mandeckta (1996). According to these authors and to Bouix (1994), carcasses of lambs sired by breeds of large mature weights have relatively deposit less internal more back fat compared with lambs sired by breeds with small mature weight.

The sex of lamb had no effect (P > 0.05) on slaughter age and carcass weights but had an effect (P < 0.01) on dressing percentage (Table 2). Males were 10% heavier at slaughter, had superior carcass weight (+5%) but had 5% lower dressing percentage than female lambs. The differences between male and female were observed in previous studies using other local purebreds (El Fadili et al 1998; El Fadili 2000 and 2004).

The superiority in dressing percentage in female lambs may be explained by their tendency to deposit more fat in their carcass than males. This superiority was also observed in previous studies (Boujenane et al 1996, El Fadili 2004, Bouix 1994). Therefore, sex of lamb had effects on mesenteric and back fat deposits (P < 0.05). Females deposited more mesenteric fat (+249 g) and had thicker back fat (1.36 mm) than males. In other studies (El Fadili et al 1998 and El Fadili et al 2001) also observed respectively  that carcasses from female lambs were also fatter than male lambs' carcasses by +180 g and +170 g, and +0.6 and +0.89 mm respectively for mesenteric fat and back fat thickness.

The rearing type had high an effect (P < 0.01) on all carcass traits, except on lambs slaughter age (P > 0.05) but lambs reared singles were younger (- 3 days) at slaughter than lambs reared twins and more (Table 2). Indeed, slaughter and carcass weights and dressing percentage in single lambs exceeded those in twins or triplets,

The effects of the number of lambs per parturition were minor, with differences (P < 0.05) only for internal mesenteric fat +132 g when compared to multiple rearing types (Table 2). Therefore, single birth lambs tended to deposit more internal and back fat than twins and more lambs respectively by +142 g and +0.15 points.  Similar findings were observed by El Fadili et al (1998) when they compared lamb number per parturition effect on carcass weight, dressing percentage and internal and external fat deposit in other Moroccan local breeds, Timahdite and Sardi.

Year had an effect (P <0.05) on slaughter age and weight, carcass weight and dressing percentage. However, year had no (P >0.05) effect on internal and subcutaneous fat deposit (Table 2). El Fadili et al (1998) reported an effect of year of birth on carcass fat deposit.

Carcass development

The results showed that, sex of lambs had no effect (P >0.05) for carcass length, leg wide, conformation, and carcass compacity, but had significant effect for carcass wide and longissimus dorsi area (Table 3). Male carcasses were 5% largest and greatest by 22% cm² than female’s carcasses. An effect of sex was reported by (El Fadili et al 1998), except for carcass length and conformation. Furthermore, El Fadili (2004) observed no effect of sex on leg length, conformation score and longissimus dorssi area for Boujâad lambs.

The rearing type affected (P < 0.05) all carcass measurements, except longisimus dorsi area. Lambs reared as singles had greater values than those reared as twins or triplets. The differences were in favor of singles reared by 2, 4, 4, 12 and 10% respectively for carcass length, carcass wide, leg wide, conformation score, longissimus dorsi area and carcass compacity. An effect of twinning was observed by El Fadili et al (1998), except for carcass length and carcass development.  By contrast, El Fadili (2004) found no effect of rearing type on all traits of purebreds and crossbred lambs confounded.

Year had no effect (P >0.05) effect on all carcass development traits studied on INRA180 lambs (Table 3). While, in previous studies using local purebreds and crossbred lambs, the year of birth had significant effects on all carcass development traits (El Fadili et al 1998; El Fadili 2004).

Conclusions

• The INRA180 purebred lambs had good  fattening performance and carcasses traits.

  
  

• The acceptation of this new synthetic breed by the Moroccan breeders especially when the management and feeding conditions are adequate such in favourable agricultural regions, promise an increase of sheep productivity and efficiency in lamb production.

Acknowledgements

The author wishes to acknowledge the technicians and staff of the sheep station at El Koudia experimental domain of INRA for their contribution in control and animal keeping.

References

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Received 27 June 2012; Accepted 14 October 2012; Published 6 November 2012

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