Effects of the FecB gene on birth weight, postnatal growth rate and puberty in Booroola x Merinos d'Arles ewe lambs

The effects of the presence of the FecB gene on birth weight, body growth rate and puberty was analyzed in 44 Fec(B)Fec(+) and 48 Fec(+) Fec(+) Booroola x Merinos d'Arles ( MA) ewe lambs and 46 MA ewe lambs. The FecB gene was considered as being present when the ovulation rate, determined by five laparoscopies, was, at least one time, >= 3. The type of birth ( single vs twins) but not the presence of the FecB gene, affected birth weight and body growth. In spite of a transitory difference in the percentage of cycling ewes between FecBFec+ and Fec+ Fec+, the age and body weight at the first ovulation ( defined by the presence of a functional corpus luteum, as plasma progesterone > 1 ng center dot mL(-1), detected at weekly sampling intervals) was similar in the three genotypes ( FecBFec+, Fec(+) Fec(+) and MA: 332.5, 334.8, 330.8 days and 34.1, 34.1, 34.9 kg, respectively). Thus, the presence of one copy of the FecB gene did not modify puberty. This is an important difference between the Booroola and other prolific breeds such as Romanov, Finn or D'Man, which are characterized by a clearly precocious puberty.