2003 Southern Section ASAS meeting

Prepubertal administration of porcine Epidermal Growth Factor increases litter size

John J. McGlone, Deidre L. Anderson and Vaughan H. Lee. Pork Industry Institute, Texas Tech University and Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, 79409.

Two studies were conducted to evaluate the effects of porcine Epidermal Growth Factor (pEGF) on litter size in pigs. Recombinant pEGF was generated by RT-PCR and subcloned into a bacterial vector. The recombinant pEGF molecule had 5 histadine residues that aided in protein isolation and its identity was confirmed by Western blot analysis. In the first pilot study, four prepubertal gilts were selected from each of three litters. Littermates received either 1 mg/day pEGF (equivalent to 0.03 mg mEGF biological activity) or control vehicle each day from 14 to 28 days of life. The pEGF or control solution were administered by mini-osmotic pump. Half the gilts were sacrificed at about 70 d of age for examination of ovarian development by histology. The remaining half were mated to a single sire and taken to term. The second study involved 26 or 28 gilts per treatment (82 gilts farrowing in total). Three doses of pEGF were used (0, 1 or 2 mg/d) and the pEGF was given by a single daily i.m. injection. Half the gilts received a single injection of 5 mL of P.G.600 (Intervet) at 70 days of age and half received a control injection. P.G.600 had no effects on reproductive measures and was dropped from the analyses. Linear contrasts were used to compare control with pEGF treatments (1 or 2 mg/d did not differ). In the first pilot study, gilts had morphological evidence of enhanced follicular development and had 3.33 more pigs born alive when treated with pEGF compared with gilts in the control treatment. In the second study, both doses of pEGF increased (P = 0.05) total numbers of pigs born per litter. Control pigs had 10.1, while each pEGF treatment produced 12.2 pigs born per litter (SE = 0.83). Gilts treated with pEGF also tended (P = 0.08) to wean 1.5 more pigs per litter than control litters. Days to onset of puberty, piglet preweaning survival and body weights at 21 days were not different among treatments (P > 0.15). In conclusion, pEGF can increase litter size in gilts when administered to the prepubertal gilt.