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Caracterização produtiva e reprodutiva das raças Merina Branca e Merina Preta em Portugal
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Orientador(es)
Resumo(s)
In this study, growth and reproductive records from two Portuguese breeds of sheep - Merino
Branco (MB) and Merino Preto (MP) were analyzed by linear model methodologies to assess the
importance of systematic environmental factors on these traits. Data were gathered from flocks
registered in the Herd Books owned by the Portuguese Merino Breeders Association from 1995 to
2008.
Growth traits evaluated were adjusted weights at 30 (PA30), 60 (PA60) and 90 (PA90) days of
age and average daily weight gains from birth to 30 (GMD30), 60 (GMD60) and 90 (GMD90) days of
age. A total of 36029 weighing records were used for MB and 16098 records for MP. To evaluate
prolificacy, 29008 and 12827 records were analyzed for MB and MP, respectively.
Separated statistical analyses were performed for each breed. Growth data were analyzed as
a trait of the lamb and models included the fixed effects of sex, type of birth, age of dam, season of
birth and the interactions sex * type of birth, year of birth * breeder, age of dam * type of birth and type
of birth * season of birth and ewe and residual as random effects. Prolificacy was evaluated as a
repeated trait of the ewe and the model contained the fixed effects of season of birth of the ewe,
lambing season, age of ewe at lambing and the interactions year of lambing * breeder and age of ewe
at lambing * lambing season and the residual as random effect.
Adjusted weights for MB single born lambs were 11,12±0,03 Kg for PA30, 17,74±0,06 Kg for
PA60 and 24,20±0,09 Kg PA90. Corresponding weights for MP were 11,17±0,04 Kg for PA30,
17,40±0,08 Kg for PA60 and 23,42±0,13 Kg PA90, respectively. MB twin lambs weighted 1,85 Kg,
2,71 Kg and 3,16 Kg less than singles (p <0,001), for PA30, PA60 and PA90, respectively. On
average, single born MP lambs were 14% heavier than twins and, as observed for MP lambs,
differences increased with age. Males were significantly heavier than females (p < 0,001). Observed
differences were 0,4 Kg for PA30, 0,7 Kg for PA60 and 1,0 Kg for PA90 in the MB breed and 0,5 Kg
for PA30, 0,9 Kg for PA60 and 1,3 Kg for PA90 for MP. For both breeds, ewes of intermediate ages (4
and 5 years old) had in general heavier lambs than younger or older ewes (p < 0,001). Lambs born in
the Fall were lighter as compared to those born in Winter (p < 0,001) (11% for MB and 13% for MP).
Average daily gains for MB singles were 220±0,001 gr/day for GMD30, GMD60 and GMD90,
respectively. Corresponding values for MP were 230±0,001 gr/day, 220±0,001 gr/day and 210±0,001
gr/day. In both breeds, differences between singles and twins (p < 0,001) ranged from 20 to 30 gr/day
for all growth intervals. Males grew faster than the females (p < 0,001), with differences of 8 gr/day for
GMD30 and 10 gr/day for GMD60 and GMD90 in the MB. For MP larger differences were observed
between sexes (10 gr/day for GMD30 and GMD60 and 20 gr/day for GMD90). As for fixed age
weights, a quadratic effect of age of dam was also observed for all weight gains in the two breeds.
Consistently higher weight gains were obtained in lambs born in Winter than in the Fall (range 20 to 50
gr/day).
Prolificacy was low for both breeds (average 1,10 lambs/ewe lambing). For MB, most of the
variation was due to the interactions year of lambing * breeder and age (P<0,001) of ewe at lambing *
lambing season (P<0,001) reflecting probably large management differences. In the MP breed,besides these effects, age of ewe at lambing was significant (p< 0,001). Four year old and older ewes
showed higher prolificacies (range 1,14 to 1,16) than younger ewes (range 1,06 to 1,10).
The results of this study show that the same environmental factors affect growth performance in both
breeds. Growth rate is slower than typical meat sheep breeds, but having in perspective that animals
are raised in extensive grazing conditions, the growth potential shown by both breeds is reasonable.
In terms of reproduction, prolificacy is rather low, showing however an increase with increasing age.
The combined results of growth and reproductive performance reveal that these genotypes show great
longevity and adaptability to local production systems.------------------------------Procedeu-se à análise, pelo método dos quadrados mínimos, de alguns efeitos ambientais
sistemáticos sobre caracteres produtivos e reprodutivos de ovinos das raças Portuguesas Merina
Branca e Merina Preta. Os dados foram recolhidos nos efectivos dos criadores inscritos na
ANCORME, entre 1995-2008.
Os pesos ajustados aos 30, 60 e 90 dias para os borregos da raça MB e nascidos de partos
simples foram 11,12±0,03 Kg; 17,74±0,06 Kg; 24,20±0,09 Kg, respectivamente e 11,17±0,04 Kg;
17,40±0,08; 23,42±0,13 Kg para borregos MP. Para as duas raças em estudo, os machos
superiorizaram-se significativamente (P <0,001) às fêmeas e borregos nascidos no Inverno foram
sempre mais pesados (P <0,001) comparativamente aos nascidos na época do Outono.
Observou-se que borregos MB e MP, oriundos de partos simples fizeram ganhos médios
diários de 220 gr/dia. O valor da prolificidade foi baixo para as duas raças, relativamente a outras
raças de ovinos (valor médio de 1,10 borr. /parto) aumentando com a idade da ovelha.
Este estudo revela que estas raças possuem uma taxa de crescimento mais lento
relativamente a outras raças vocacionadas para a produção de carne, assim como a baixa
prolificidade registada.
O potencial produtivo e reprodutivo dos genótipos MB e MP avaliado neste trabalho é
revelador de grande longevidade e adaptabilidade às condições de exploração.
Descrição
Mestrado em Engenharia Agronómica - Agro-Pecuária - Instituto Superior de Agronomia
Palavras-chave
sheep adjusted weights average daily gain prolificacy ovinos Merino Branco Merino Preto pesos ajustados ganhos médios diários prolificidade Portugal