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Fattening of Pelibuey hair sheep and crossbreds (Rambouillet-Dorset×Pelibuey) in the Mexican tropics
Small Ruminant Research 27 Ž1998. 263–266
Fattening of Pelibuey hair sheep and crossbreds žRambouillet-Dorset= Pelibuey / in the Mexican tropics J. Pineda a , J.M. Palma b, G.F.W. Haenlein d , M.A. Galina a
a,b,c,)
PICP Posgrado Interinstitucional en Ciencias Pecuarias, UniÕersidad de Colima, AP. 22 Colima, Colima, 28000 Mexico ´ b CUIDA, UniÕersidad de Colima, AP. 22 Colima, Colima 28000, Mexico ´ c Departamento de Ciencias Pecuarias, Facultad de Estudios Superiores Cuautitlan, ´ UNAM, Cuautitlan ´ Izcalli, Edo de Mexico 54700, Mexico ´ ´ d Department of Animal and Food Sciences, UniÕersity of Delaware, Newark, DE 19717-1303, USA Accepted 16 January 1996
Abstract A study was conducted on a farm in tropical Mexico with 19 crossbred ŽPelibuey= Rambouillet-Dorset. and 20 Pelibuey hair sheep lambs, each group subdivided into male and female subgroups. Feeding in total confinement was with a ration of 6% guinea grass and 94% of a mixture of 37.5% poultry litter, 37.5% corn, 14.5% molasses, 7% coconut oilmeal, 2% urea, 1% salt and 0.5% minerals. Crossbreds and males exceeded Pelibuey and females in total feed intake and intake on a metabolic weight basis Ž P - 0.05.. Daily weight gains after 64 days of fattening for crossbreds were 238 g and 182 g compared with Pelibuey, 182 g and 102 g for males and females, respectively Ž P - 0.05.. Similar results were obtained after 34 days of fattening. Feed conversion efficiency similarly was better for crossbreds and better for males. Carcass evaluations gave similar results for all groups, with a small advantage for crossbreds in overall meat percentage. However crossbreds and males achieved desirable slaughter weight significantly earlier than Pelibuey and females. Feed cost per kg of meat production was significantly lower after 34 days compared with 64 days; and was lower for crossbreds and males after 34 and 64 days. It was concluded that F1 crossbreeding of hair sheep with larger wool breeds enables a greater weight gain to be obtained in a shorter time, with better feed conversion efficiency and economics. q 1998 Published by Elsevier Science B.V. Keywords: Hair sheep; Fattening; Crossbreds; Tropics
1. Introduction In Mexico there is a good market for lambs, and demand has been greater than supply, causing large
)
Corresponding author. Tel: Ž331. 411 33; fax: Ž331. 275 81; e-mail: galina @cgic.ucol.mx
imports of lambs from USA and New Zealand ŽCruz, 1991.. In the tropics, climatic conditions and all year grazing are favorable for improving lamb production to meet domestic demands. Local production systems could be improved by breeding adapted local breeds, Pelibuey and Barbados Blackbelly, Žfemales with large wool sheep males. to produce F1 crossbreds for slaughter, with greater body weight gains and
00921-4488r98r$19.00 q 1998 Published by Elsevier Science B.V. All rights reserved. PII S 0 9 2 1 - 4 4 8 8 Ž 9 7 . 0 0 0 2 1 - 7
J. Pineda et al.r Small Ruminant Research 27 (1998) 263–266
264
Table 1 Total and average daily feed intake of crossbred and Pelibuey male and female lambs after 64 days of fattening Breed
Sex
n
Concentrate Žg.
Grass Žg.
Total intake Žg.
Average intake1
Crossbreds
Males Females Males Females
10 9 10 10
1206 1159 755 667
75 75 75 75
1281 " 57a 1234 " 53A 830 " 50b 742 " 62B
136 " 13.1a 142 " 14.8A 95 " 5.1b 85 " 3.7B
Pelibuey
a,b; A,B Ž P - 0.05.. DM kgy1 BW 0.75 .
1
some wool supply for the artisanal industry ŽGalina and Guerrero, 1993.. Pelibuey sheep grazing in the tropics have shown low weight gains from 40–80 g per day ŽTorres et al., 1978., but in other studies Pelibuey crossbreds reached DWG of 100–110 g ŽOlazaran ´ et al., 1991.. Large wool sheep breeds have been adapted to Mexican conditions from the original Spanish importations of Rambouillet, and low seasonality has been achieved ŽGalina et al., 1996.. Fattening of Pelibuey lambs on grazing produced low weight gains, but some confinement management can increase growth. However, use of concentrates is costly, reducing profit; therefore mixed systems have to be studied ŽGalina et al., 1996.. The objectives of this study were to challenge Pelibuey and crossbreds with Rambouillet or Rambouillet= Dorset in full confinement to measure
growth under optimal conditions, carcass evaluation and economic feasibility. 2. Materials and methods The study was conducted near Colima, Mexico. The farm is located at 19813X latitude N and 104848X longitude W, at 550 m above sea level. The climate is classified as dry tropics with rain from June to October, average temperature 258C, with a minimum of 178C and maximum of 308C. There is an average rain precipitation of 850 mm per year, minimum relative humidity 56% and maximum 80% ŽGarcıa, ´ 1973.. Two groups of sheep were studied, Group 1 with
Table 2 Average daily weight gain and feed conversion efficiency for F1 crossbreds and Pelibuey males and females after 34, 64 days of fattening and overall Breed
Sex
Daily weight gain (g) Crossbreds Males Females Pelibuey Males Females
n
34 days
64 days
Overall
10 9 10 10
246"30 221"24 191"23 112"24
231"83 143"56 173"63 98"16
238.5a 182.0A 182.0b 102.0B
Feed conÕersion efficiency (kg feed DM: kg BW) Crossbreds Males 10 5.122:1 5.545:1 Females 9 5.072:1 8.629:1 Pelibuey Males 10 5.350:1 5.650:1 Females 10 6.675:1 9.210:1 a,b; A,B Ž P - 0.05..
5.334:1 6.850:1 5.500:1 7.942:1 Fig. 1. Cumulative weight gains of F1 crossbred and Pelibuey males and females.
J. Pineda et al.r Small Ruminant Research 27 (1998) 263–266
nine females and 10 males from crossbreeding Rambouillet = Dorset males with Pelibuey females; Group 2 with 10 male and 10 female Pelibuey hair sheep. Average initial weight was 17.8 " 2.6 kg of crossbred males and 15.9 " 2.1 of female crossbreds. Pelibuey hair sheep control weights were 17.0 " 1.7 kg for males and 16.1 " 2.2 kg for females. All sheep were fully confined and fed a mixture of 94% concentrate with 16.5% CP and 3.0 Mcal ME and 6% of guinea grass Ž Panicum maximum. for 64 days, after adapting to the diet for 7 days. Concentrate was composed of poultry litter Ž37.5%., corn Ž37.5%., molasses Ž14.5%., coconut oilmeal Ž7%., urea Ž2%., salt Ž1%. and a mineral salt mixture Ž0.5%.. Daily forage intake was weighed, refusal recorded, weekly body weights were determined until 30 kg BW was achieved by males. Feed conversion efficiency was calculated and seven and four lambs, respectively, were slaughtered from crossbreds and Pelibuey for carcass evaluation. Results were evaluated statistically by analyses of variance, covariance and regression. 3. Results Table 1 contains the overall daily feed consumption for crossbred and Pelibuey male and female lambs after 64 days of fattening. Crossbreds had significantly higher feed intakes per day and per metabolic BW Ž P - 0.01.. Average DWG was greater for males over females and greater for crossbreds compared with Table 3 Carcass evaluations of crossbreds and Pelibuey lambs after fattening to reach slaughter weight Crossbreds
Pelibuey
Males Females Males Females Number of lambs 3 4 Slaughter weight Žkg. 30 22 Age Ždays. 152 163 Overall meat percentage Ž%. 45.2 45.6 Head, legs and tail Ž%. 6.7 6.0 Empty digestive tract Ž%. 7.8 6.9 Respiratory tract Ž%. 1.4 1.7 Liver Ž%. 3.1 3.2 Skin Ž%. 16.9 16.1
2 2 30 24 250 310 44.3 44.5 6.4 6.3 7.9 7.0 1.4 1.3 3.1 3.3 16.1 16.7
265
Table 4 Feed cost per kg of meat production for male and female crossbreds and Pelibuey lambs Breed
Sex
n
Feed cost 1
Feed cost 2
Crossbreds
Males Females Males Females
10 9 10 10
0.95 0.94a 0.99 1.24a
0.99 1.27b 1.02 1.48b
Pelibuey
a,b Ž P - 0.05.. per kg BW, after 34 days, US $. 2 per kg BW, after 64 days, US $. 1
Pelibuey after 34 as well as after 64 days of fattening Ž P - 0.05, Table 2.. Fig. 1 shows similar differences for the cumulative weight gains up to 9 weeks of fattening. Feed conversion efficiency was better for male than female crossbreds on an overall 64 days basis and crossbreds had better feed conversion efficiency than Pelibuey lambs after 34 days, 64 days and overall ŽTable 2.. Carcass evaluation was performed in 11 lambs after feeding to desired slaughter weights up to 44 weeks. Slight apparent advantages were noted for crossbreds in meat percentage, head, legs and tails, but significant differences in days reaching final slaughter weight for crossbreds ŽTable 3.. Table 4 shows that cost of meat production in US $ per kg was slightly less for crossbreds and males. The cost for females was significantly less at 34 days compared with 64 days of fattening regardless of breed Ž P - 0.05.. 4. Discussion Previously DWG among males and females of 240 g and 161 g, respectively, with DM feed conversion of 5.2 and 8.0:1 have been obtained in Pelibuey sheep with 70 to 80% corn ŽAguilera et al., 1995.. However, high cost of corn limits the economical use of the diet, so alternative uses of other sources of nitrogen, such as non-protein nitrogen, low degrading protein and non-degradable rumen protein conversion, as described in this work, were developed to produce similar DWG in Pelibuey and larger gains in crossbreds with lower cost. On the other hand, the present results were slightly higher than most obtained in the tropics with similar diets of 16% CP and 2.87 Mcal ME kgy1 DM in
266
J. Pineda et al.r Small Ruminant Research 27 (1998) 263–266
Pelibuey Ž191 g. ŽMartınez, 1991. or those applied to ´ Dorset= Pelibuey Ž225 g. or Pelibuey Ž190 g. by Cambellas Ž1990.. Romano Ž1989. obtained DWG of 205 g with a feed conversion of 7.5:1 in Pelibuey. When DWG was increased, conversion of DM to body weight was also augmented, but produced at a higher cost. Carcass value of total meat was lower at 45.2%– 45.6% than that published by Aguilera et al. Ž1995., who obtained 52.5% and 50.8% for males and females, respectively. However the high content of corn in the diet will increase cost. Similar findings have been reported by Cambellas Ž1990. with 51.1% for F1 crosses and 49.3% for Pelibuey. Cost of production per kg of lamb BW in pervious work has been reported at 1.50 US $, due to the use of concentrates ŽAguilera et al., 1995.. In the present work an overall lower feed cost was obtained at 1.00 US $. 5. Conclusions F1 crossbreeding hair sheep, such as Pelibuey, with large wool breed males, such as RambouilletDorset, enabled a greater weight gain to be obtained in a shorter time, better feed conversion efficiency, slightly better meat yield and better economics of production. Acknowledgements Many thanks are due to DGAPA, UNAM. Grants IN 501595, CONACYT Grant 3108-N and SIMORELOS Grant 9501075 for support of this study. References Aguilera, R., Lopez, J., Marquez, ´ ´ V., 1995. Comportamiento productivo de ovinos pelibuey alimentados con dietas basadas
en grano y mazorca de maız ´ completa. ŽProductive behavior of Pelibuey sheep fed diets based on grain and corn meal.. Rev. Vet. Mex. ´ 26, 251. Cambellas, J., 1990. Crecimiento y composicion ´ corporal de corderos West African y Dorset horn=West African. ŽBody composition and growth of West African and Dorset-horn= West African lambs.. Anais da 12a Reuniao de ALPA, Campinas, Brasil 96. Cruz, C., 1991. Engorda de los borregos pelibuey en condiciones tropicales. ŽFattening of Pelibuey lambs under tropical conditions.. Memorias de la Tercera Reunion de Produccion Animal Tropical. CIEGT. UNAM. Martinez de la Torre, Veracruz, Mexico, pp. 29–37. Galina, M.A., Guerrero, M., 1993. La Ganaderıa ´ Mexicana. Caracterısticas y Perspectivas del sector. ŽMexican livestock in´ dustry, Characteristics and perspectives.. Avances Invest. Agropecuaria, 1 Ž2., 13–40. Galina, M.A., Morales, R., Silva, E., Lopez, B., 1996. Reproduc´ tive performance of hair sheep Pelibuey and Blackbelly under Mexican tropical management systems. Small Ruminant Res. 22 Ž1., 31–38. Garcıa, ´ E., 1973. Modificaciones al sistema de clasificacion ´ climatica de Kopen. Instituto de geografıa. ´ ¨ ´ ŽModification of the climatic classification by Kopen ¨ .. Universidad Nacional Autonoma de Mexico, Mexico, D.F. 33. ´ ´ ´ Martınez, L., 1991. Hacia la integracion ´ ´ de la ovinocultura tropical con la del altiplano Mexicano. ŽIntegration of the tropical sheep industry in the Mexican highland.. IV Reunion ´ Cientıfica, Tecnologica, Forestal y Agropecuaria del estado de ´ ´ Veracruz, pp. 221–230. Olazaran, de produccion ´ J., Lagunes, J., Castillo, H., 1991. Modulo ´ ´ de carne ‘San Pedro’ con ovinos Pelibuey, Dorset=Pelibuey y Suffolk=Pelibuey. ŽModel of ‘San Pedro’ meat production with Pelibuey, Dorset=Pelibuey and Suffolk=Pelibuey sheep.. Memorias del IV Congreso Nacional de Produccion Ovina., Mexico, 81 pp. Romano, J., 1989. Evaluacion ´ de la respuesta productiva de ovinos de pelo y lana ante diferente medio ambiente y densidad energetica de la dieta. ŽEvaluation of the productive ´ response of hair and wool sheep to different evironments and energy density in the diet.. Tesis Maestrıa. ´ Facultad de Estudios Superiores Cuautitlan, ´ UNAM, Mexico. ´ Torres, H., Garza, R., Arroyo, D., De Leon, R., Molina, Y., 1978. Evaluacion del borrego Tabasco o Pelibuey bajo condiciones de pastoreo. ŽEvaluation of Tabasco or Pelibuey lambs under grazing conditions.. Memoria de la XIV Reunion Anual del Instituto Nacional de Investigaciones Pecuarias, Mexico City, 15 pp.
Fattening of Pelibuey hair sheep and crossbreds žRambouillet-Dorset= Pelibuey / in the Mexican tropics J. Pineda a , J.M. Palma b, G.F.W. Haenlein d , M.A. Galina a
a,b,c,)
PICP Posgrado Interinstitucional en Ciencias Pecuarias, UniÕersidad de Colima, AP. 22 Colima, Colima, 28000 Mexico ´ b CUIDA, UniÕersidad de Colima, AP. 22 Colima, Colima 28000, Mexico ´ c Departamento de Ciencias Pecuarias, Facultad de Estudios Superiores Cuautitlan, ´ UNAM, Cuautitlan ´ Izcalli, Edo de Mexico 54700, Mexico ´ ´ d Department of Animal and Food Sciences, UniÕersity of Delaware, Newark, DE 19717-1303, USA Accepted 16 January 1996
Abstract A study was conducted on a farm in tropical Mexico with 19 crossbred ŽPelibuey= Rambouillet-Dorset. and 20 Pelibuey hair sheep lambs, each group subdivided into male and female subgroups. Feeding in total confinement was with a ration of 6% guinea grass and 94% of a mixture of 37.5% poultry litter, 37.5% corn, 14.5% molasses, 7% coconut oilmeal, 2% urea, 1% salt and 0.5% minerals. Crossbreds and males exceeded Pelibuey and females in total feed intake and intake on a metabolic weight basis Ž P - 0.05.. Daily weight gains after 64 days of fattening for crossbreds were 238 g and 182 g compared with Pelibuey, 182 g and 102 g for males and females, respectively Ž P - 0.05.. Similar results were obtained after 34 days of fattening. Feed conversion efficiency similarly was better for crossbreds and better for males. Carcass evaluations gave similar results for all groups, with a small advantage for crossbreds in overall meat percentage. However crossbreds and males achieved desirable slaughter weight significantly earlier than Pelibuey and females. Feed cost per kg of meat production was significantly lower after 34 days compared with 64 days; and was lower for crossbreds and males after 34 and 64 days. It was concluded that F1 crossbreeding of hair sheep with larger wool breeds enables a greater weight gain to be obtained in a shorter time, with better feed conversion efficiency and economics. q 1998 Published by Elsevier Science B.V. Keywords: Hair sheep; Fattening; Crossbreds; Tropics
1. Introduction In Mexico there is a good market for lambs, and demand has been greater than supply, causing large
)
Corresponding author. Tel: Ž331. 411 33; fax: Ž331. 275 81; e-mail: galina @cgic.ucol.mx
imports of lambs from USA and New Zealand ŽCruz, 1991.. In the tropics, climatic conditions and all year grazing are favorable for improving lamb production to meet domestic demands. Local production systems could be improved by breeding adapted local breeds, Pelibuey and Barbados Blackbelly, Žfemales with large wool sheep males. to produce F1 crossbreds for slaughter, with greater body weight gains and
00921-4488r98r$19.00 q 1998 Published by Elsevier Science B.V. All rights reserved. PII S 0 9 2 1 - 4 4 8 8 Ž 9 7 . 0 0 0 2 1 - 7
J. Pineda et al.r Small Ruminant Research 27 (1998) 263–266
264
Table 1 Total and average daily feed intake of crossbred and Pelibuey male and female lambs after 64 days of fattening Breed
Sex
n
Concentrate Žg.
Grass Žg.
Total intake Žg.
Average intake1
Crossbreds
Males Females Males Females
10 9 10 10
1206 1159 755 667
75 75 75 75
1281 " 57a 1234 " 53A 830 " 50b 742 " 62B
136 " 13.1a 142 " 14.8A 95 " 5.1b 85 " 3.7B
Pelibuey
a,b; A,B Ž P - 0.05.. DM kgy1 BW 0.75 .
1
some wool supply for the artisanal industry ŽGalina and Guerrero, 1993.. Pelibuey sheep grazing in the tropics have shown low weight gains from 40–80 g per day ŽTorres et al., 1978., but in other studies Pelibuey crossbreds reached DWG of 100–110 g ŽOlazaran ´ et al., 1991.. Large wool sheep breeds have been adapted to Mexican conditions from the original Spanish importations of Rambouillet, and low seasonality has been achieved ŽGalina et al., 1996.. Fattening of Pelibuey lambs on grazing produced low weight gains, but some confinement management can increase growth. However, use of concentrates is costly, reducing profit; therefore mixed systems have to be studied ŽGalina et al., 1996.. The objectives of this study were to challenge Pelibuey and crossbreds with Rambouillet or Rambouillet= Dorset in full confinement to measure
growth under optimal conditions, carcass evaluation and economic feasibility. 2. Materials and methods The study was conducted near Colima, Mexico. The farm is located at 19813X latitude N and 104848X longitude W, at 550 m above sea level. The climate is classified as dry tropics with rain from June to October, average temperature 258C, with a minimum of 178C and maximum of 308C. There is an average rain precipitation of 850 mm per year, minimum relative humidity 56% and maximum 80% ŽGarcıa, ´ 1973.. Two groups of sheep were studied, Group 1 with
Table 2 Average daily weight gain and feed conversion efficiency for F1 crossbreds and Pelibuey males and females after 34, 64 days of fattening and overall Breed
Sex
Daily weight gain (g) Crossbreds Males Females Pelibuey Males Females
n
34 days
64 days
Overall
10 9 10 10
246"30 221"24 191"23 112"24
231"83 143"56 173"63 98"16
238.5a 182.0A 182.0b 102.0B
Feed conÕersion efficiency (kg feed DM: kg BW) Crossbreds Males 10 5.122:1 5.545:1 Females 9 5.072:1 8.629:1 Pelibuey Males 10 5.350:1 5.650:1 Females 10 6.675:1 9.210:1 a,b; A,B Ž P - 0.05..
5.334:1 6.850:1 5.500:1 7.942:1 Fig. 1. Cumulative weight gains of F1 crossbred and Pelibuey males and females.
J. Pineda et al.r Small Ruminant Research 27 (1998) 263–266
nine females and 10 males from crossbreeding Rambouillet = Dorset males with Pelibuey females; Group 2 with 10 male and 10 female Pelibuey hair sheep. Average initial weight was 17.8 " 2.6 kg of crossbred males and 15.9 " 2.1 of female crossbreds. Pelibuey hair sheep control weights were 17.0 " 1.7 kg for males and 16.1 " 2.2 kg for females. All sheep were fully confined and fed a mixture of 94% concentrate with 16.5% CP and 3.0 Mcal ME and 6% of guinea grass Ž Panicum maximum. for 64 days, after adapting to the diet for 7 days. Concentrate was composed of poultry litter Ž37.5%., corn Ž37.5%., molasses Ž14.5%., coconut oilmeal Ž7%., urea Ž2%., salt Ž1%. and a mineral salt mixture Ž0.5%.. Daily forage intake was weighed, refusal recorded, weekly body weights were determined until 30 kg BW was achieved by males. Feed conversion efficiency was calculated and seven and four lambs, respectively, were slaughtered from crossbreds and Pelibuey for carcass evaluation. Results were evaluated statistically by analyses of variance, covariance and regression. 3. Results Table 1 contains the overall daily feed consumption for crossbred and Pelibuey male and female lambs after 64 days of fattening. Crossbreds had significantly higher feed intakes per day and per metabolic BW Ž P - 0.01.. Average DWG was greater for males over females and greater for crossbreds compared with Table 3 Carcass evaluations of crossbreds and Pelibuey lambs after fattening to reach slaughter weight Crossbreds
Pelibuey
Males Females Males Females Number of lambs 3 4 Slaughter weight Žkg. 30 22 Age Ždays. 152 163 Overall meat percentage Ž%. 45.2 45.6 Head, legs and tail Ž%. 6.7 6.0 Empty digestive tract Ž%. 7.8 6.9 Respiratory tract Ž%. 1.4 1.7 Liver Ž%. 3.1 3.2 Skin Ž%. 16.9 16.1
2 2 30 24 250 310 44.3 44.5 6.4 6.3 7.9 7.0 1.4 1.3 3.1 3.3 16.1 16.7
265
Table 4 Feed cost per kg of meat production for male and female crossbreds and Pelibuey lambs Breed
Sex
n
Feed cost 1
Feed cost 2
Crossbreds
Males Females Males Females
10 9 10 10
0.95 0.94a 0.99 1.24a
0.99 1.27b 1.02 1.48b
Pelibuey
a,b Ž P - 0.05.. per kg BW, after 34 days, US $. 2 per kg BW, after 64 days, US $. 1
Pelibuey after 34 as well as after 64 days of fattening Ž P - 0.05, Table 2.. Fig. 1 shows similar differences for the cumulative weight gains up to 9 weeks of fattening. Feed conversion efficiency was better for male than female crossbreds on an overall 64 days basis and crossbreds had better feed conversion efficiency than Pelibuey lambs after 34 days, 64 days and overall ŽTable 2.. Carcass evaluation was performed in 11 lambs after feeding to desired slaughter weights up to 44 weeks. Slight apparent advantages were noted for crossbreds in meat percentage, head, legs and tails, but significant differences in days reaching final slaughter weight for crossbreds ŽTable 3.. Table 4 shows that cost of meat production in US $ per kg was slightly less for crossbreds and males. The cost for females was significantly less at 34 days compared with 64 days of fattening regardless of breed Ž P - 0.05.. 4. Discussion Previously DWG among males and females of 240 g and 161 g, respectively, with DM feed conversion of 5.2 and 8.0:1 have been obtained in Pelibuey sheep with 70 to 80% corn ŽAguilera et al., 1995.. However, high cost of corn limits the economical use of the diet, so alternative uses of other sources of nitrogen, such as non-protein nitrogen, low degrading protein and non-degradable rumen protein conversion, as described in this work, were developed to produce similar DWG in Pelibuey and larger gains in crossbreds with lower cost. On the other hand, the present results were slightly higher than most obtained in the tropics with similar diets of 16% CP and 2.87 Mcal ME kgy1 DM in
266
J. Pineda et al.r Small Ruminant Research 27 (1998) 263–266
Pelibuey Ž191 g. ŽMartınez, 1991. or those applied to ´ Dorset= Pelibuey Ž225 g. or Pelibuey Ž190 g. by Cambellas Ž1990.. Romano Ž1989. obtained DWG of 205 g with a feed conversion of 7.5:1 in Pelibuey. When DWG was increased, conversion of DM to body weight was also augmented, but produced at a higher cost. Carcass value of total meat was lower at 45.2%– 45.6% than that published by Aguilera et al. Ž1995., who obtained 52.5% and 50.8% for males and females, respectively. However the high content of corn in the diet will increase cost. Similar findings have been reported by Cambellas Ž1990. with 51.1% for F1 crosses and 49.3% for Pelibuey. Cost of production per kg of lamb BW in pervious work has been reported at 1.50 US $, due to the use of concentrates ŽAguilera et al., 1995.. In the present work an overall lower feed cost was obtained at 1.00 US $. 5. Conclusions F1 crossbreeding hair sheep, such as Pelibuey, with large wool breed males, such as RambouilletDorset, enabled a greater weight gain to be obtained in a shorter time, better feed conversion efficiency, slightly better meat yield and better economics of production. Acknowledgements Many thanks are due to DGAPA, UNAM. Grants IN 501595, CONACYT Grant 3108-N and SIMORELOS Grant 9501075 for support of this study. References Aguilera, R., Lopez, J., Marquez, ´ ´ V., 1995. Comportamiento productivo de ovinos pelibuey alimentados con dietas basadas
en grano y mazorca de maız ´ completa. ŽProductive behavior of Pelibuey sheep fed diets based on grain and corn meal.. Rev. Vet. Mex. ´ 26, 251. Cambellas, J., 1990. Crecimiento y composicion ´ corporal de corderos West African y Dorset horn=West African. ŽBody composition and growth of West African and Dorset-horn= West African lambs.. Anais da 12a Reuniao de ALPA, Campinas, Brasil 96. Cruz, C., 1991. Engorda de los borregos pelibuey en condiciones tropicales. ŽFattening of Pelibuey lambs under tropical conditions.. Memorias de la Tercera Reunion de Produccion Animal Tropical. CIEGT. UNAM. Martinez de la Torre, Veracruz, Mexico, pp. 29–37. Galina, M.A., Guerrero, M., 1993. La Ganaderıa ´ Mexicana. Caracterısticas y Perspectivas del sector. ŽMexican livestock in´ dustry, Characteristics and perspectives.. Avances Invest. Agropecuaria, 1 Ž2., 13–40. Galina, M.A., Morales, R., Silva, E., Lopez, B., 1996. Reproduc´ tive performance of hair sheep Pelibuey and Blackbelly under Mexican tropical management systems. Small Ruminant Res. 22 Ž1., 31–38. Garcıa, ´ E., 1973. Modificaciones al sistema de clasificacion ´ climatica de Kopen. Instituto de geografıa. ´ ¨ ´ ŽModification of the climatic classification by Kopen ¨ .. Universidad Nacional Autonoma de Mexico, Mexico, D.F. 33. ´ ´ ´ Martınez, L., 1991. Hacia la integracion ´ ´ de la ovinocultura tropical con la del altiplano Mexicano. ŽIntegration of the tropical sheep industry in the Mexican highland.. IV Reunion ´ Cientıfica, Tecnologica, Forestal y Agropecuaria del estado de ´ ´ Veracruz, pp. 221–230. Olazaran, de produccion ´ J., Lagunes, J., Castillo, H., 1991. Modulo ´ ´ de carne ‘San Pedro’ con ovinos Pelibuey, Dorset=Pelibuey y Suffolk=Pelibuey. ŽModel of ‘San Pedro’ meat production with Pelibuey, Dorset=Pelibuey and Suffolk=Pelibuey sheep.. Memorias del IV Congreso Nacional de Produccion Ovina., Mexico, 81 pp. Romano, J., 1989. Evaluacion ´ de la respuesta productiva de ovinos de pelo y lana ante diferente medio ambiente y densidad energetica de la dieta. ŽEvaluation of the productive ´ response of hair and wool sheep to different evironments and energy density in the diet.. Tesis Maestrıa. ´ Facultad de Estudios Superiores Cuautitlan, ´ UNAM, Mexico. ´ Torres, H., Garza, R., Arroyo, D., De Leon, R., Molina, Y., 1978. Evaluacion del borrego Tabasco o Pelibuey bajo condiciones de pastoreo. ŽEvaluation of Tabasco or Pelibuey lambs under grazing conditions.. Memoria de la XIV Reunion Anual del Instituto Nacional de Investigaciones Pecuarias, Mexico City, 15 pp.