Effects of the FecXR allele of BMP15 gene on the birth weight, growth rate and carcass quality of Rasa Aragonesa light lambs

Small Ruminant Research 108 (2012) 45–53

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Effects of the FecXR allele of BMP15 gene on the birth weight, growth rate and carcass quality of Rasa Aragonesa light lambs A. Roche a,1 , G. Ripoll a , M. Joy a , J. Folch a , B. Panea a , J.H. Calvo a,b , J.L. Alabart a,∗ a b

Unidad de Tecnología en Producción Animal, CITA, Av. Monta˜ nana 930, 50059 Zaragoza, Spain ARAID, 50004 Zaragoza, Spain

a r t i c l e

i n f o

Article history: Received 27 February 2012 Received in revised form 18 June 2012 Accepted 19 June 2012 Available online 11 July 2012

Keywords: Sheep Bone morphogenetic protein 15 Ternasco de Aragón Average daily gain Meat quality Sensory analysis

a b s t r a c t A new allele of the BMP15 gene (FecXR ) that increases prolificacy has been recently described in the Rasa Aragonesa sheep breed. The present study was conducted to evaluate the effects of lamb and maternal genotypes on birth weight, growth and meat quality traits. Two experiments were carried out. In experiment 1, the progeny of heterozygous (R+) and wild-type (++) dams mated to wild-type hemizygous (+) rams from four flocks were tested to estimate the effects of the FecXR allele on birth weight and average daily gains (ADGs) until weaning and slaughter (at approximately 50 and 100 days of age, respectively). Three maternal/lamb genotype groups were studied: wild-type progeny from ++ ewes (females: ++/++, n = 62; males: ++/+, n = 60), wild-type progeny from R+ ewes (females: R+/++, n = 31; males: n = 28 R+/+) and progeny carrying the FecXR mutation born to R+ ewes (females: R+/R+, n = 35; males: R+/R, n = 28). No significant differences were observed in the birth weights or ADGs between the FecXR genotype groups in either female or male lambs. In experiment 2, 37 male lambs (13 ++/+, 12 R+/+ and 12 R+/R) were used to evaluate the effect of the FecXR genotype groups on carcass characteristics and meat quality traits. All lambs were classified within the normal ranges for the “Ternasco de Aragón” commercial category, and no significant differences were observed between the genotype groups. We conclude that birth weight, growth traits, light lamb carcass characteristics and meat quality traits were not affected by the maternal and lamb FecXR genotype combinations that were studied. © 2012 Elsevier B.V. All rights reserved.

1. Introduction Genetic studies on sheep prolificacy have indicated that litter size and ovulation rates can be determined by the action of single genes with a major effect, known as the fecundity (Fec) genes: BMPR 1B, BMP15 and GDF9 (Davis, 2005). The impact of the presence of the BMPR 1B (Bone Morphogenetic Protein Receptor type 1B) gene (Booroola; FecB) on sheep production is well-documented (reviewed by Fogarty, 2009). However, different naturally

∗ Corresponding author. Tel.: +34 976716450; fax: +34 976716335. E-mail address: [email protected] (J.L. Alabart). 1 Present address: Oviaragón-Grupo Pastores S.C.L., 50014 Zaragoza, Spain. 0921-4488/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.smallrumres.2012.06.011

occurring mutations in the sheep GDF9 (Growth Differentiation Factor 9) and BMP15 (Bone Morphogenetic Protein 15) genes (FecG and FecX, respectively) have only been associated with high prolificacy or sterility depending on their heterozygotic or homozygotic presence, respectively (Galway, Belclare, Inverdale, Hanna, Lacaune, Rasa Aragonesa, Moghani, Ghezel and Barbarine breeds; Hanrahan et al., 2004; Galloway et al., 2000; Davis, 2005; Bodin et al., 2007; Martínez-Royo et al., 2008; Barzegari et al., 2009; Vacca et al., 2010). No studies of the effect of FecX alleles on growth performances have been conducted. The results concerning birth weight related to the Booroola genotype (FecB), a single mutation in the gene of the type I-B receptor for BMP15, as well as for other BMPs and AMH, have been studied in Booroola crosses. In Garole (Homozygous for FecB) × Malpura crossbred sheep, a lower birth weight of

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A. Roche et al. / Small Ruminant Research 108 (2012) 45–53

the FecB carrier progeny was found (Kumar et al., 2008). In the same way, in Booroola-Assaf crosses homozygous FecB ewe lambs also showed a lower birth weight than either heterozygous or non-carrier ewe lambs (Gootwine et al., 2006). However, no significant effect of the ewe lamb’s genotype on birth weight has been found in the Merino d’Arles breed (Abella et al., 2005). From these references, it can be concluded that the effect of the Booroola mutation on the birth weight may depend on the breed in which the allele is introgressed. A selection programme to increase prolificacy has been carried out in the Spanish breed Rasa Aragonesa since 1994, as the number of lambs born per ewe plays a key role in the efficiency and viability of the farms (Pardos et al., 2008). This selection led to the detection of a new naturally occurring polymorphism in the BMP15 gene (FecXR allele), which consists of a deletion of 17 bp in the coding region of BMP15, located on the X chromosome, causing increased prolificacy in heterozygous (R+) and sterility in homozygous (RR) ewes (Martínez-Royo et al., 2008). In the following years, the use of naturally occurring polymorphisms can be an important tool to increase the reproductive efficiency. In the case of Rasa Aragonesa sheep (approximately 500,000 animals recorded), the FecXR allele increases prolificacy in heterozygous ewes, and consequently the reproductive efficiency is also improved. This mutation produces an increase of 0.63 extra ovulations and 0.35 extra lambs per lambing ewe. The percentages of single, double, triple, quadruple and quintuple births in FecXR ewes are 67.7, 31.0, 1.3, 0.77 and 0.091%, respectively while in wild-type Rasa Aragonesa ewes are 42.5, 46.9, 9.7, 0.054 and 0.0042%, respectively (Lahoz et al., 2011). Because this mutation is linked to the X chromosome, the mutation can be easily spread through the farms by artificial insemination. To prevent the appearance of sterile RR ewes, farmers are advised against keeping FecXR sires on their farms. Rather, most hemizygous FecXR sires are grouped in artificial insemination centres, and most R+ ewes are produced by artificial insemination and remain identified. The progeny of these heterozygous ewes as replacement animals is genotyped for BMP15 and identified. Due to its advantages, farmers have an increasing interest in this polymorphism, and the demand of seminal doses from Rasa Aragonesa carrier sires is continuously increasing (Lahoz et al., 2011). Consequently, it is necessary to check the effect of this allele on production parameters other than prolificacy to ensure the absence of undesirable characteristics associated with that allele. In the European Union, consumers are aware of meat quality traits. Therefore, possible consequences of the current selection programmes on those traits might be of critical economic importance in the near future. The aim of the present study was to evaluate the effect of FecXR on growth performance parameters, as well as on carcass and meat quality traits.

2. Materials and methods 2.1. Experiment 1 The animals used in this study belong to four different flocks. Three of them are commercial, and the fourth belongs to the Centro de

Investigación y Tecnología Agroalimentaria (CITA) de Aragón research centre (Zaragoza, Spain). In the present study, three groups based on the following combinations of maternal and lamb genotypes were considered: wild-type progeny from wild-type ewes, wild-type progeny from ewes carrying the FecXR allele and, finally, mutant progeny (carrying FecXR ) from ewes carrying the FecXR allele. The nomenclature to describe these groups is the following: the maternal genotype is followed by the lamb’s genotype, separated by a slash (/); in ewes, the mutant (FecXR ) and wild-type (FecX+ ) alleles are represented as R and +, respectively (++: homozygous wildtype; R+: heterozygous). As BMP15 is located on the X chromosome, the males have only one allele, and they are said to be hemizygous (+: wildtype; R: mutant). One hundred and twenty two lambs (28 R+/+ and 28 R+/R males, and 31 R+/++ and 35 R+/R+ females) and 122 control lambs (60 ++/+ males and 62 ++/++ females) were studied. These lambs’ wild-type (+) fathers were chosen at random from the different available families. The BMP15 genotype (lambs and dams) was determined as described by MartínezRoyo et al. (2009). All animals were subjected to the same management, nutrition and environmental conditions in all farms. During the last third of pregnancy and the subsequent two months after parturition, the ewes received a total mixed ration ad libitum (40% straw, 60% concentrate; 128 g CP/kg, 510 g NDF/kg on a dry matter basis). After parturition, all animals remained indoors, the lambs suckled dams until weaning, and from the second week post-partum, the lambs had free access to concentrate. After weaning, the lambs were fed with concentrate (185 g CP/kg, 190 g NDF/kg, on a dry matter basis) and straw ad libitum until slaughter. During the whole trial, fresh water was supplied to the animals. Only single, double and triple births were considered in this study. The numbers of lambs born as singles, twins and triplets in the three experimental groups were: non-carrier lambs born to carrier ewes, 13, 35 and 11, respectively; carrier lambs born to carrier ewes, 10, 42 and 11, respectively; non-carrier lambs born to non-carrier ewes, 20, 75 and 27, respectively. The lambs were weighed immediately after birth and thereafter at weaning (age: approximately 50 days) and slaughter (age: approximately 100 days) with an electronic balance (0.1 kg precision). Pre-weaning, post-weaning and overall average daily gains (ADG1, ADG 2 and ADG(1+2)) were calculated for each lamb as the difference between final and initial weights divided by the total number of days.

2.2. Experiment 2 2.2.1. Carcass traits Thirty-seven male lambs (13 ++/+, 12 R+/+ and 12 R+/R) were used to evaluate the effect of genotype on carcass characteristics, meat quality and sensory analysis. The three groups of selected lambs were well-balanced according to birth type (single or twin births). The lambs were always kept indoors and had concentrate and straw available ad libitum since weaning. The lambs were weighed on weekly intervals at 8 h a.m. with an electronic balance (0.1 kg precision). The lambs were brought to slaughter at weekly intervals when they reached 22–24 kg of live-weight (LW). The lambs were slaughtered at the experimental abattoir of the Research Centre according to the specifications of the “Ternasco de Aragón” protected geographical indication (Official Journal of the European Union, 2008). Slaughter procedures were conducted according to the guidelines of the Council Directive 86/609/EEC (European Communities, 1986) on the protection of animals used for experimental and other scientific purposes. The slaughter lamb weight (SW), hot carcass weight (HCW) and cold carcass weight (CCW; 24 h after slaughter at 4 ◦ C) were recorded. Dressing percentage was calculated as CCW × 100/LWS. Subjective classification of conformation and fatness degree were conducted following the Community Scale for Classification of Carcasses of Ovine Animals (Official Journal of the European Union, 1994) for light carcasses (<13 kg). The conformation was scored with grade values from 15 for E+ (excellent) to 1 for P− (poor) of the EUROP system (E excellent, U very good, R good, O fair and P poor), and the classification for fatness degree was scored from 1 (low), 2 (slight), 3 (average), 4 (high), expanded to three points (1−, 1, 1+; 2−, 2, 2+; 3−, 3, 3+, 4−, 4, 4+). Hence, the fatness degree was scored from 1 to 12. Subjective fat colour and meat colour were determined according to Colomer-Rocher et al. (1988): The fat colour was scored from 1 (very white) to 9 (intensive yellow) for white, cream or yellow classification, and the M. rectus abdominis colour was scored from

A. Roche et al. / Small Ruminant Research 108 (2012) 45–53 1 (very pale pink) to 9 (very dark) for pale pink, pink and other colour classifications. The following objective carcass measurements were also recorded: carcass internal length (L) and hindquarter perimeter (D), according to Colomer-Rocher et al. (1988). These measurements were used to calculate the carcass compactness index (CCW/L). 2.2.2. Instrumental measurements: the pH of the M. longissimus thoracis and the colour of the M. rectus abdominis, subcutaneous fat and M. longissimus thoracis Instrumental colour measures were determined on subcutaneous fat colour at the tail root (Díaz et al., 2002) and on the M. rectus abdominis. The subcutaneous fat colour was measured at three selected locations, avoiding blood spots, discolorations and less covered areas. The M. rectus abdominis was assessed at two locations on the internal face of each selected piece to obtain a mean value representative of the surface colour after having removed the covering fascia (Eikelenboom et al., 1992). A white tile behind the muscle was used to standardise the measurements. The tail was removed, the carcass was carefully split longitudinally and the two halves were weighed. The renal fat from the left half of the carcass was removed and weighed. The left side was cut into six standardised commercial joints: thoracic limb, breast, pelvic limb, neck, anterior-rib, and loin-rib according to Colomer-Rocher et al. (1988). The joints were classified in the 1st category (anterior-rib, pelvic limb, loin-rib), 2nd category (thoracic limb), and 3rd category (breast and neck). The thoracic limb was weighed and dissected into muscle, bone, fat (subcutaneous, intermuscular) and waste (major blood vessels, ligaments, tendons, and thick connective tissue sheets associated with some muscle) according to Colomer-Rocher et al. (1988). The M. longissimus thoracis from the left side was removed and sampled as follows: samples from the 6th to the 10th thoracic vertebrae were taken for chemical analysis, vacuum-packed and frozen (−20 ◦ C) until analysis. The muscle ultimate pH was measured at the 4th vertebral region with a pH-metre equipped with a Crison 507 penetrating electrode (Crison Instruments S.A., Barcelona, Spain). The M. longissimus thoracis samples for colour measurements were cut with a minimum thickness of 2 cm and placed in a polystyrene tray, wrapped with an oxygen permeable film and kept in the dark at 4 ◦ C. The M. longissimus thoracis colour was measured immediately after cutting and after 24 h of air exposure on the cranial side of the 11th thoracic vertebra. The instrumental colour was measured using a Minolta CM-2006 d spectrophotometer (Konica Minolta Holdings, Inc., Osaka, Japan) in the CIELAB space (CIE, 1986) with a measured area diameter of 8 mm, specular component included and 0% UV, standard illuminant D65, which simulates daylight (colour temperature 6504 K), the observer angles of 10 and zero and the white calibration. The lightness (L*), redness (a*) and yellowness (b*) were recorded, and hue angle (H*) and chroma (C*) −1 indices were calculated as 57.29 tan (b*/a*), expressed in degrees, and C∗ =

2

47

2, heated to 200 ◦ C) to an internal temperature of 70 ◦ C, monitored using an internal thermocouple (Jenway 2000, Bibby Scientific Ltd., Essex, England). Every loin was trimmed of any external connective tissue, cut into 2 cm × 2 cm samples, wrapped in individually marked aluminium foil and stored in a warm cabinet at 50 ◦ C until they were tasted. The samples were served at random to a trained (ISO 8586-1, 1993) eight-member taste panel in individual booths under red lighting to mask differences in the meat colour. A comparative multi-sample test with three samples each was used to detect differences in taste attributes between the treatments. The sensory variables analysed were the lamb’s odour intensity, fat odour intensity, tenderness, fibrousness, juiciness, greasiness, the lamb’s flavour intensity, metallic flavour intensity, grease flavour intensity and overall rating. For each variable, an unstructured 10-point scale was used on which 1 was the lowest score and 10 the highest score for the attribute in question, as described in the above-mentioned document (ISO 8586-1, 1993). 2.3. Statistical analyses The effect of the genotype group (dam/lamb) on the weight at birth and the ADG were analysed by ANOVA using PROC GLM of the SAS statistical package (SAS, 2004). All terms included in the model were considered as fixed effects: the birth type (single, double or triple), the lamb’s sex, the lamb’s genotype group (dam/lamb: Carrier/Carrier, Carrier/Noncarrier, Non-carrier/Non-carrier) and the farm (Farms 1–4). All possible interactions between birth type, the lamb’s sex and the lamb’s genotype group were examined. Correlations between birth weight and ADG were assessed by the Pearson’s correlation coefficient using PROC CORR of SAS. Objective and subjective carcass measurements, proportions of joints, commercial meat categories, instrumental colour variables of caudal subcutaneous fat, M. rectus abdominis and M. longissimus thoracis, sensory characteristics and the fatty acid composition were analysed by one-way ANOVA (PROC GLM of SAS) considering the genotype group as a fixed effect. Instrumental colour variables of M. longissimus thoracis were analysed using a mixed ANOVA model for repeated measures based on Kenward–Roger’s adjusted degrees of freedom solution (PROC MIXED of SAS; Littell et al., 1998; Ripoll et al., 2012). The genotype was included as a between-subject fixed effect, time (0 h and 24 h) as a within-subject effect and the animal as the subject (experimental unit). The lowest Akaike Information Criterion (AIC) was used to choose the matrix of the error structure. When ANOVA indicated a significant genotype group effect, two orthogonal contrasts were used to test for differences between progeny genotypes and between maternal genotypes, respectively. The significance level was considered for values of P ≤ 0.05.

3. Results and discussion

2

(a∗) + (b∗) .

3.1. Experiment 1 2.2.3. Chemical composition of the meat Meat samples were minced to determine the percentage of crude protein (Dumas procedure; AOAC, 1999) and intramuscular fat (AOAC, 1999). The M. longissimus thoracis portion was minced for FA analysis. Fatty acid methyl esters were obtained using a 20% solution of boron trifluoride in methanol (Rule, 1997). Analysis of fatty acid methyl esters was performed by gas chromatography using a flame ionisation detector (FID) and an HP-6890 gas chromatograph equipped with an H-88 column that was 100 m × 0.25 mm id with 0.20-␮m film thickness (Agilent Technologies, Waldbronn, Germany). Fatty acid content was expressed as a percentage of the total amount of the FAs identified. After individual FA determination, the sum of the saturated fatty acids (SFA), monounsaturated FA (MUFA), and polyunsaturated FA (PUFA) was calculated. Moreover, the PUFA/SFA and PUFA n−6/n−3 ratios were calculated. 2.2.4. Sensory analysis After 24 h of refrigeration at 4 ◦ C, the longissimus lumborum muscle was removed from the left half of each carcass for the sensory analysis. All samples were vacuum-packed and frozen (−20 ◦ C) until analysis. On the day of the panel test, the samples were thawed inside their bags under cold running water until they reached an internal temperature of 17–19 ◦ C. After the bags were opened, the loins were wrapped in aluminium foil and cooked on a heated double-plate grill (Sammic P8D-

Significance levels for the main effects and interactions on the birth weight and growth phases are shown in Table 1. As expected, the farm, birth type and sex had a significant influence on the performance traits. Birth weight and ADG1 depended on the farm, birth type and sex, while ADG2 depended on the farm and sex. The birth weight of lambs born as singles, twins and triplets were 4.2 ± 0.1, 3.4 ± 0.1 and 3.1 ±0.1 kg, respectively (least squares means ± SE). Although ADG2 did not depend on the birth type or the genotype, a significant interaction between both factors was found. In this way, higher ADG2 values were observed in carrier progeny in comparison with non-carrier progeny born to non-carrier ewes only within triplets (294.2 ± 18.6 vs. 244.9 ± 9.7 g/d, respectively; P < 0.05). Non-carrier triplets born to carrier ewes showed an intermediate ADG2 that was not significantly different from the above-mentioned groups (252.0 ± 16.0 g/d). At present, we have no explanation for

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A. Roche et al. / Small Ruminant Research 108 (2012) 45–53

Table 1 Factors affecting birth weight and the pre- and post-weaning growth rates of Rasa Aragonesa light lambs of different FecXR genotype groups. Source

Birth weight ADG1 ADG2 ADG(1+2)

Farm Birth type (BT) Lamb’s sex (S) Lamb’s genotype group (G) BT × S BT × G S×G BT × S × G

**

**

**

*

**

**

NS

NS

**

**

**

**

NS NS NS NS NS

NS NS NS NS NS

NS NS

NS NS NS NS NS

*

NS NS

ADG1, ADG2, ADG(1+2): pre-weaning, post-weaning and overall average daily gain, respectively; NS: not significant. * P < 0.05. ** P < 0.01.

this result. In meat breeds, milk allowance may be limiting in triplets. This fact could have been exacerbated by putative small differences existing between the lamb’s genotypes in post-weaning growth. The overall growth ADG(1+2) depended only on the farm and sex. Concerning the gender effect on growth rates, the greater ADGs in male than in female lambs was expected (Askar et al., 2006; Álvarez-Rodríguez et al., 2010), and the gender effect was linked to a higher feed conversion ratio in female compared to male lambs, which has been attributed to greater fat deposition (Rodríguez et al., 2008). Growth rates ADG1, ADG2 and ADG(1+2) were positively correlated with birth weight (r = 0.38, 0.32 and 0.45; each P < 0.0001). Therefore, heavier lambs at birth tended to show a greater daily gain. The correlation between ADG1 and ADG2 was also significant, although it was lower than those mentioned above (r = 0.18; P < 0.01). These results confirm the importance of achieving an adequate birth weight to reach fast growth rates in both the pre-weaning and the fattening periods. The birth weight results were similar between the dam/lamb genotype groups considered (Table 2). These values were in agreement with previous reports in the wild-type Rasa Aragonesa ewes (Beriain et al., 2000; Álvarez-Rodríguez et al., 2010). Our study confirms the preliminary results reported by Lahoz et al. (2011), which showed that the maternal genotype did not have a significant effect on the birth weight among lambs from the same type of birth. Consequently, we suggest that the presence of the FecXR allele in the mother has no negative effects on the foetal growth of carrier and non-carrier progenies.

The growth rates did not differ between the genotype groups (Table 2), and these values were in agreement with previous reports in wild-type Rasa Aragonesa lambs (Beriain et al., 2000; Álvarez-Rodríguez et al., 2010). The nutrition of the lamb during its first weeks of life depends on the dam’s milk, and thus its growth is related to mother’s milk quantity and quality. The similar pre-weaning ADG (ADG1) observed in the wild-type progeny of R+ and ++ dams would indicate similar milk yield (quantity and quality) in both genotypes. In addition, the similar ADG1 observed in the wild-type and FecXR -carrier progenies of the R+ dams suggests that the presence of FecXR in the progeny does not affect pre-weaning growth. Although the post-weaning ADG (ADG2) was slightly lower in R+/+ male lambs than in either ++/+ or R+/R male lambs, significance was not achieved. Most studies of Booroola Merino (B◦ M) cross lambs and lambs from crossbred ewes introgressed with FecB reported lower birth weights and growth rates. However, it is difficult to separate the effects of low background genetic merit for growth of the B◦ M and the lower birth weight and growth rate of lambs from larger litters from the genetic effect of carrying FecB (Fogarty, 2009). In conclusion, the results reported here suggest that FecXR does not affect either the weight at birth or the growth rates in the pre-weaning and fattening periods. 3.2. Experiment 2 As far as we know, the effects of FecX mutations in BMP15 on carcass classification and sensory characteristics have not been reported. 3.2.1. Carcass traits With the exception of the carcass internal length, the genotype group had no effect (P > 0.05) on objective and subjective carcass characteristics (Table 3). All carcasses were included within C class (10.1–13 kg) of the European carcass classification system for light lambs (Ternasco commercial category). The presence of the mutation did not affect the conformation score or fatness degree. The classification obtained was according to the Ternasco commercial category, with a usual classification ranging from O− to O+ (in the Scale EUROP) and 2+ (Slight+). Dressing percentage was slightly low in relation to other studies (Carrasco et al., 2009a). The hot carcass weight was in agreement with previous works in the same type of lambs in the Rasa Aragonesa (Beriain et al., 2000; Álvarez-Rodríguez et al., 2010) and

Table 2 Least squares means ± SE for birth weight and pre- and post-weaning growth rates of Rasa Aragonesa light lambs by sex and genotype group. Lamb’s sex

Genotype group (dam/lamb)

n

Birth weight (kg)

ADG1 (g/d)

ADG2 (g/d)

ADG(1+2) (g/d)

Male

++/+ R+/+ R+/R

60 28 28

3.7 ± 0.1 3.7 ± 0.1 3.9 ± 0.2

204.4 ± 0.6 216.4 ± 1.0 208.5 ± 1.2

281.7 ± 0.7 271.9 ± 1.1 310.1 ± 1.3

240.9 ± 0.4 244.6 ± 0.7 249.7 ± 0.9

Female

++/++ R+/++ R+/R+

62 31 35

3.4 ± 0.1 3.4 ± 0.1 3.3 ± 0.1

199.2 ± 0.8 180.5 ± 1.0 189.6 ± 0.8

230.6 ± 0.9 227.9 ± 1.1 229.7 ± 1.0

212.1 ± 0.6 204.4 ± 0.7 211.6 ± 0.6

n: number of lambs; ADG1, ADG2, ADG(1+2): pre-weaning, post-weaning, and overall average daily gains, respectively. The within sex differences between genotype groups were not statistically significant.

A. Roche et al. / Small Ruminant Research 108 (2012) 45–53

49

Table 3 Least squares means of weight, carcass characteristics and the subjective and objective measures of Rasa Aragonesa light male lambs of different FecXR genotype groups. Genotype (dam/lamb) Number of animals Weights and carcass characteristics Slaughter lamb weight (SW) (kg) Hot carcass weight (HCW) (kg) Cold carcass weight (CCW) (kg) Dressing percentage (%) Renal fat weight (kg) Subjective carcass evaluation Conformation scorea (1–15) Fatness Scoreb (1–12) Fat Colourc (1–9) M. rectus abdominis colourd (1–9) Objective carcass evaluation Carcass internal length (cm) Hindquarter perimeter (cm) Carcass compactness (CCW/L) (g/cm)

++/+

R+/+

R+/R

13

12

12

23.3 10.9 10.6 45.4 1.5

22.5 10.6 10.3 45.6 1.7

22.8 10.9 10.4 45.7 1.6

5.8 (O+ ) 5.8 (2+ ) 2.2 (W) 2.0

5.5 (O) 5.7 (2+ ) 2.2 (W) 1.8 54.1 53.1 195.3

52.9 52.7 194.2

5.4 (O) 6.1 (2+ ) 2.1 (W) 1.8 53.9 52.6 193.3

SE

Significance

0.25 0.20 0.20 0.62 0.12

NS NS NS NS NS

0.29 0.29 0.25 0.12

NS NS NS NS

0.34 0.41 0.35

*,e

NS NS

SE: standard error; NS: not significant a Scale from 1 (P− : poor) to 15 (E+ : Excellent) of the EUROP classification (E excellent, U very good, R good, O fair and P poor). b Scale from 1 (1− : very low) to 12 (4+ : very high). c Scale from 1 to 9 (1− : very white, 9: intensive yellow) of white (W), cream (Cr), yellow (Y). d Scale from 1 to 9 (1− : very clear pink to 9: very dark) of clear (C), pink (P), red (R). e Orthogonal contrasts: between lamb genotypes (R vs. +): P < 0.06; between maternal genotypes (R+ vs. ++): P < 0.13. * P < 0.05.

Churra Tensina (Joy et al., 2008a) breeds. Fat colour was not affected by genotype (P > 0.05), and a subjective classification of white and was equal to that observed in concentrate-fed light lambs (Joy et al., 2008a; Ripoll et al., 2012). No studies of the effect of the FecXR allele of the BMP15 gene on carcass classification are found in the literature. Studies on Booroola crosses showed that carrier lambs had higher carcass weights and fatter carcasses than wild-type lambs (Kleemann et al., 1985, 1988; Visscher et al., 2000). Nevertheless, the effect of the FecB genotype on the carcass and meat quality was considered to be small (Visscher et al., 2000). Current results for the zoometric conformation measurements (Table 3) were similar to previous studies in light lambs (Carrasco et al., 2009a). The dam/lamb BMP15 genotype only significantly affected the half-carcass internal length. As a significant difference was not observed between maternal genotypes and the difference between lamb genotypes only approached statistical significance

(P < 0.06), this effect was likely due to the fact that halfcarcass internal length was longer in the wild-type lambs born to wild-type dams than in the wild-type lambs born to FecXR carrier dams. These results are likely related to the slaughter weight. Lambs from the ++/+ genotype were slaughtered at 23.3 kg while the rest were slaughtered at 22.5 and 22.8 kg for R+/+ and R+/R, respectively (Table 3). With heavier lambs, you get a bigger carcass and consequently, a longer half-carcass internal length. Regardless of the differences in internal length (P < 0.05), no differences were found in carcass compactness, meaning that there was no effect on commercial value, according to Carrasco et al. (2009a). The proportions of joints obtained from the left half-carcasses are presented in Table 4. The BMP15 genotype only affected the second category, which corresponds to the thoracic limb, whose proportion was somewhat higher in the lambs born to wild-type dams than in the lambs born to FecXR carrier dams (P < 0.04). Carcasses from all genotype groups presented a similar proportion of

Table 4 Least squares means for the proportion of joints obtained from the left half-carcasses of Rasa Aragonesa light lambs of the different FecXR genotype groups. Genotype (dam/lamb)

++/+

R+/+

R+/R

SE

Effect

Half carcass weight (g) Thoracic limb (%) Loin-rib (%) Pelvic limb (%) Anterior-rib (%) Neck (%) Breast (%) Commercial meat category 1st category (%) 2nd category (%) 3rd category (%)

5233.8 20.8 19.1 35.3 6.9 7.2 10.6

5140.8 20.2 19.8 34.9 7.1 7.7 10.3

5249.5 20.4 19.3 34.9 7.3 7.9 10.3

108.29 0.19 0.34 0.34 0.27 0.28 0.23

NS

61.4 20.8 17.8

61.8 20.2 18.0

61.5 20.4 18.1

0.31 0.19 0.35

NS

1st category: loin-rib, pelvic limb, anterior-rib; 2nd category: thoracic limb; 3rd category: neck and breast. SE: standard error; NS: not significant. a Orthogonal contrasts: between lamb genotypes (R vs. +): P < 0.48; between maternal genotypes (R+ vs. ++): P < 0.04. * P < 0.05.

*,a

NS NS NS NS NS

*,a

NS

50

A. Roche et al. / Small Ruminant Research 108 (2012) 45–53

Table 5 The pH values (a) and instrumental colour of (b) M. rectus abdominis, (c) subcutaneous caudal fat, (d) M. longissimus thoracis (Least squares means ± SE) in male lambs of the different FecXR genotype groups. (a) Genotype group (dam/lamb)

++/+

R+/+

R+/R

SE

Effect

pH

5.64

5.59

5.57

0.02

NS

(b) Genotype group (dam/lamb)

++/+

R+/+

R+/R

SE

Effect

L* a* b* Hue angle Chroma

46.2 11.9 10.1 40.1 15.8

45.9 11.9 10.1 40.6 15.9

46.9 12.00 10.6 41.0 16.2

0.94 0.50 0.56 2.30 0.42

NS NS NS NS NS

Genotype group (dam/lamb)

++/+

R+/+

R+/R

SE

Effect

L* a* b* Hue angle Chroma

65.9 4.3 13.0 71.5 13.7

66.8 4.1 12.8 72.3 13.4

66.8 4.1 12.7 72.3 13.4

0.61 0.34 0.48 1.33 0.49

NS NS NS NS NS

(c)

(d) Genotype (dam/lamb)

++/+

Time

0h

L* a* b* Hue angle Chroma

39.0 9.6 3.4 19.8 10.3

R+/+ 24 h ± ± ± ± ±

1.7 0.5 1.0 2.3 0.6

43.1 12.8 8.2 32.8 15.2

R+/R

0h ± ± ± ± ±

1.7 0.5 1.0 2.3 0.6

37.3 7.9 3.3 20.3 8.6

24 h ± ± ± ± ±

1.7 0.6 1.0 2.4 0.7

43.7 11.7 7.3 32.6 13.9

P-value

0h ± ± ± ± ±

1.7 0.6 1.0 2.4 0.7

34.3 8.6 6.6 18.7 8.6

24 h ± ± ± ± ±

1.7 0.5 1.0 2.3 0.6

43.2 12.7 7.8 31.6 15.0

± ± ± ± ±

1.7 0.5 1.0 2.3 0.6

G

T

G×T

NS NS NS NS NS

0.0001 0.0001 0.0003 0.0001 0.0001

NS NS NS NS NS

SE: standard error; NS: not significant.

first and third carcass categories and were classified within the normal ranges for the “Ternasco de Aragón” commercial category, the first category representing more than 60% of commercial meat in all genotype groups.

3.2.2. Instrumental measurements: pH of the M. longissimus thoracis and colour of the M. rectus abdominis, subcutaneous fat and the M. longissimus thoracis The mean pH values and instrumental colour of M. rectus abdominis, subcutaneous fat and M. longissimus thoracis are shown in Table 5. There were no significant differences among the genotype groups (P > 0.05). The values ranged from 5.57 to 5.64 (P > 0.05), which is in agreement with ˜ several studies carried out in light lambs (Sanudo et al., 1997; Díaz et al., 2002; Carrasco et al., 2009b; Ripoll et al., 2005, 2012). This pH range is the usual pH of light lamb’s meat, ruling out dark-cutting or stress problems due to differences in handling or behaviour between treatments (Carrasco et al., 2009b). The genotype did not have any effect on the colour indexes (P > 0.05). The results observed in M. rectus abdominis are in agreement with those observed in other studies conducted in male Rasa Aragonesa lambs (Ripoll et al., 2008, 2012). The M. rectus abdominis of these lambs would be classified as red (Ripoll et al., 2012) according to the Colomer–Rocher scale (Colomer-Rocher et al., 1988).

Concerning the subcutaneous fat colour, there were no significant differences between the genotype groups (P > 0.05; Table 5). White fat colour is the most common colour in concentrate-fed light lambs, whereas when forage is included into the diet, greater values of lightness and hue angle are found (Carrasco et al., 2009b; Ripoll et al., 2012). The colour of the M. longissimus thoracis was only affected by time of exposure to air (P < 0.001; Table 5). All colour indices increased over time, rising from 0 to 24 h after cutting, due to the oxidation of deoxymyoglobin. 3.2.3. The chemical composition of meat The FecXR allele of BMP15 had no effect on moisture, protein content or intramuscular fat content (P > 0.05; Table 6). The average intramuscular fat content observed in the present study, specifically, 2.55%, was similar to that

Table 6 Chemical composition of M. longissimus thoracis in male lambs of the different FecXR genotype groups. Genotype group (dam/lamb)

++/+

R+/+

R+/R

SE

Effect

Moisture (%) Fat (%) Crude protein (%)

74.96 2.46 21.13

74.59 2.66 21.32

74.96 2.52 21.13

0.18 0.17 0.12

NS NS NS

SE: standard error; NS: not significant.

A. Roche et al. / Small Ruminant Research 108 (2012) 45–53

51

Table 7 Fatty acid profile (g/100 g fat) of the M. longissimus thoracis of the different FecXR genotype groups. Genotype group (dam/lamb)

++/+

R+/+

R+/R

SE

Effect

Capric (C10:0) Lauric (C12:0) Myristoleic (C14:0) Palmitic (C16:0) Palmitoleic (C16:1) Heptadecanoic (C17:0) Heptadecenoic (C17:1) Stearic (C18:0) Oleic (C18:1n−9) Vaccenic (C18:1n−7) Linoleic (C18:2n−6) Linolenic (C18:3n−3) CLA, cis9, trans11 (C18:2n−7) Arachidic (C20:0) (C20:1n−9) Arachidonic (C20:4n−6) Eicosapentaenoic (C20:5n−3) Docosatetraenoic (C22:4n−6) Docosapentaenoic (C22:5n−3) DPA Docosahexaenoic (C22:6n−3) DHA SFA MUFA PUFA PUFA/SFA n−6/n−3

0.2 0.25 2.77 23.01 2.4 1.25 0.85 13.33 41.34 2.19 7.27 0.44 0.43 0.08 0.09 2.63 0.26 0.24 0.63 0.3 42.90 46.84 12.23 0.29 6.36

0.18 0.21 2.77 22.99 2.38 1.52 1.01 13.84 40.98 2.15 7.15 0.44 0.39 0.08 0.09 2.47 0.25 0.22 0.56 0.27 43.49 46.53 11.85 0.27 6.56

0.19 0.21 2.66 23.07 2.48 1.4 0.97 13.59 40.73 2.39 7.3 0.36 0.52 0.08 0.09 2.7 0.19 0.27 0.51 0.23 43.28 46.59 12.18 0.28 8.10

0.01 0.02 0.19 0.37 0.06 0.08 0.06 0.29 0.68 0.1 0.39 0.03 0.06 0.003 0.003 0.18 0.03 0.02 0.04 0.03 0.55 0.71 0.67 0.01 0.27

NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS *,a

SFA: saturated fatty acids; MUFA: monounsaturated fatty acids; PUFA: polyunsaturated fatty acids; NS: not significant. a Orthogonal contrasts: between lamb genotypes (R vs. +): P < 0.03; between maternal genotypes (R+ vs. ++): P < 0.05. * P < 0.05.

observed by Dervishi et al. (2010) in light lambs of the same breed reared under the same feeding system. The intramuscular fat composition is shown in Table 7. The most abundant fatty acids observed in the present study were oleic, palmitic and stearic acids, as expected. These fatty acids accounted for approximately two thirds of the total fatty acid amount, which was in agreement with the results reported by several authors (Velasco et al., 2004; Arana et al., 2006; Panea et al., 2011). Studies in the literature of the effect of the FecB gene on fat content and its composition are scarce (Suess et al., 2000; Mezoszentgyorgyi et al., 2001). No effect of the FecXR genotype groups on fatty acid composition was observed (P > 0.05). The contents of different FAs were in agreement with previous studies in Rasa Aragonesa light lambs ˜ (Sanudo et al., 2000) and Churra Tensina light lambs (Joy et al., 2008b; Panea et al., 2011; Joy et al., 2012). Concerning the proportions of the FA groups (Table 7), genotype only had an effect on the PUFA n−6/n−3 ratio, which was higher in R lambs (P < 0.03). In addition, it was higher in lambs born to R+ ewes (P < 0.05). Similarly, Suess et al. (2000) found that the ratio between linoleic (18:2, n−6) and linolenic (18:3, n−3) acid was higher in the progeny of FecB carriers. In spite of the three genotype groups received the same concentrate, ADG2 was slightly higher in R+/R lambs (310.1 vs. 271.9 and 281.7 g/d in R+/+ and ++/+; Table 2). This higher ADG2 may explain, at least in part, the observed differences between genotype groups. We have no clear explanation for this result, and further research is required. 3.2.4. Sensory evaluation The FecXR allele did not affect any sensorial characteristics of the meat (Table 8). Our results for sensory attributes

are in agreement with previous works in wild-type light lambs (Martínez-Cerezo et al., 2005; Panea et al., 2011). It is known that meat quality traits have a low heritability (Barkhouse et al., 1996; Wulf et al., 1996). In an experiment with Texel pure lambs, Lambe et al. (2011) reported that the presence or absence of Texel-muscling QTL (TMQTL) did not affect any of the sensory variables studied, although it influenced the shear force values. Notwithstanding, Lambe et al. (2010) reported that the effect of QTL phenotype on shear force disappeared when ageing time was increased. Most authors (Goodson et al., 2001; Warner et al., 2010) reported that meat from animals expressing the callipyge genotype presented higher shear force values than meat from control animals, due to a higher calpastatin activity in the muscles of callipyge lambs, an inhibitor of the calpain-mediated degradation of myofibrilar proteins. Nevertheless, some authors reported an interaction between muscle type and phenotype, causing the calTable 8 Sensory characteristics of Rasa Aragonesa light male lambs of the different FecXR genotype groups. Genotype group (dam/lamb)

R+/R

R+/+

++/+

SE

Effect

Lamb odour intensity (1–10) Fat odour intensity (1–10) Tenderness (1–10) Fibrousness (1–10) Juiciness (1–10) Greasiness (1–10) Lamb flavour intensity (1–10) Metallic flavour intensity (1–10) Grease flavour intensity (1–10) Overall rating (1–10)

4.6 2.8 6.3 4.5 5.9 3.4 5.2 3.4 4.3 5.6

4.6 2.9 5.8 4.7 5.4 3.8 5.1 3.5 4.1 5.2

4.3 2.9 6.3 4.2 6.3 3.5 5.0 3.8 4.1 5.3

1.49 1.21 1.51 1.78 1.68 1.71 1.37 1.68 1.91 1.40

NS NS NS NS NS NS NS NS NS NS

SE: standard error; NS: not significant.

52

A. Roche et al. / Small Ruminant Research 108 (2012) 45–53

lipyge phenotype to affect the shear force in the longissimus dorsi but not in the fore-limb muscles (Duckett et al., 1998). This interaction was also found for sensory variables (Goodson et al., 2001), demonstrating that callipyge expression decreases the tenderness of the longissimus dorsi but not that of the biceps femoris muscle. Altogether, these results suggest that the effect of genotype on meat sensory characteristics is different for the different alleles studied to date. In the present study, the FecXR allele did not affect meat sensory quality. 4. Conclusions In the present work, we have demonstrated that farmers can use this polymorphism without any effect on birth weight, growth rate, or meat quality in male and female lambs. The characteristics of the carcasses of FecXR male lambs are within the specifications of the protected geographical indication, ‘Ternasco de Aragón’. Acknowledgments The authors are thankful to the cooperative UPRA˜ de Grupo Pastores (Servicio de mejora genética en rebanos raza Rasa Aragonesa) and to the staff of CITA de Aragón for their assistance in sample collection and analysis. This study was supported by the Ministerio de Ciencia e Innovación (project TRACE PET-2008-0076). References AOAC, 1999. Official Methods of Analysis, 16th ed. Association Official Analytical Chemists International, Gaithersburg, MD, USA. Abella, D.F., Cognie, Y., Thimonier, J., Seck, M., Blanc, M.R., 2005. Effects of the FecB gene on birth weight, postnatal growth rate and puberty in Booroola × Merinos d’Arles ewe lambs. Anim. Res. 54, 283–288. Álvarez-Rodríguez, J., Sanz, A., Ripoll-Bosch, R., Joy, M., 2010. Do alfalfa grazing and lactation length affect the digestive tract fill of light lambs? Small Rumin. Res. 94, 109–116. Arana, A., Mendizábal, J.A., Alzón, M., Eguinoa, P., Beriain, M.J., Purroy, A., 2006. Effect of feeding lambs oleic acid calcium soaps on growth adipose tissue development and composition. Small Rumin. Res. 63, 75–83. Askar, A.R., Guada, J.A., Gonzalez, J.M., de Vega, A., Castrillo, C., 2006. Diet selection by growing lambs offered whole barley and a protein supplement, free choice: effects on performance and digestion. Livest. Sci. 101, 81–93. Barkhouse, K.L., Van Vleck, L.D., Cundiff, L.V., Koohmaraie, M., Lunstra, D.D., Crouse, J.D., 1996. Prediction of breeding values for tenderness of market animals from measurements on bulls. J. Anim. Sci. 74, 2612–2621. Barzegari, A., Atashpaz, S., Ghabili, K., Nemati, Z., Rustaei, M., Azarbaijani, R., 2009. Polymorphisms in GDF9 and BMP15 associated with fertility and ovulation rate in Moghani and Ghezel sheep in Iran. Reprod. Domest. Anim. 45, 666–669. Beriain, M.J., Horcada, A., Purroy, A., Lizaso, G., Chasco, J., Mendizabal, J.A., 2000. Characteristics of Lacha and Rasa Aragonesa lambs slaughtered at three live weights. J. Anim. Sci. 78, 3070–3077. Bodin, L., Di Pasquale, E., Fabre, S., Bontoux, M., Monget, P., Persani, L., Mulsant, P., 2007. A novel mutation in the bone morphogenetic protein 15 gene causing defective protein secretion is associated with both increased ovulation rate and sterility in Lacaune sheep. Endocrinology 148, 393–400. Carrasco, S., Ripoll, G., Sanz, A., Álvarez-Rodríguez, J., Panea, B., Revilla, R., Joy, M., 2009a. Effect of feeding system on growth and carcass characteristics of Churra Tensina light lambs. Livest. Sci. 121, 56–63. Carrasco, S., Panea, B., Ripoll, G., Sanz, A., Joy, M., 2009b. Influence of feeding systems on cortisol levels, fat colour and instrumental meat quality in light lambs. Meat Sci. 45 (2), 209–215. Colomer-Rocher, F., Delfa, R., Sierra, I., 1988. Método normalizado para el estudio de los caracteres cuantitativos y cualitativos de las canales

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