Submitted to: Biology of Reproduction Abstracts
Publication Type: Abstract only
Publication Acceptance Date: 3/14/2003
Publication Date: 6/1/2003
Citation: CHRISTENSON, R.K., LEYMASTER, K.A. EFFECTS OF SELECTION FOR OVULATION RATE OR UTERINE CAPACITY ON NUMBER AND WEIGHT OF PIGS AT BIRTH AND WEANING. BIOLOGY OF REPRODUCTION ABSTRACTS. 2003. v. 68(Suppl. 1). p. 244. Abstract No. 321. Interpretive Summary:
Technical Abstract: Ovulation rate (OR) was determined at laparoscopy and uterine capacity (UC) was determined by number of fully formed pigs at farrowing in unilaterally hysterectomized-ovariectomized gilts. Eleven generations of selection for ovulation rate or uterine capacity increased (P < 0.01) OR (3.2 ova) or UC (1.1 pigs per uterine horn). Our objective was to explore the effects of enhanced OR or UC on farrowing and weaning traits in control (CO), OR, or UC-line White crossbred gilts for four years following selection. Fifty-three gilts of each line were assigned to experiment in each of two seasons (March and September) of 1999, 2000, 2001, and 2002. Gilts were mated within line and 40 gilts per line were allowed to farrow. Normal husbandry procedures were used at farrowing, and pigs were weaned at 18 days of age and retained for the next generation. At farrowing, CO line (n = 324 gilts) means for total number of pigs born, live born pigs, stillborn pigs, and mummified fetuses were 10.3 +/ 0.2 pigs, 9.7 +/ 0.2 pigs, 0.63 +/ 0.07 pigs and 0.31 +/ 0.04 mummified fetuses, respectively. OR (n = 298 gilts) or UC (n = 279 gilts) line means deviated from the CO line means by 0.5* and 0.8* pigs, 0.2 and 0.5* pigs, 0.26* and 0.24* pigs and 0.22* and -0.12* mummified fetuses, respectively (* P < 0.05). CO line means for pig birth weight, litter birth weight, number of pigs weaned, and litter weaning weight were 1.30 +/ 0.01 kg, 13.1 +/ 0.2 kg, 8.4 +/ 0.2 pigs, and 38.9 +/ 0.7 kg, respectively. OR or UC line means deviated from the CO line means by -0.08** and -0.02 kg, -0.1 and 0.9** kg, -0.1 and 0.2 pigs, and -0.5 and 1.7 kg, respectively (** P < 0.01). In summary, total number of pigs, number of live pigs and number of stillborn pigs were increased by single-trait selection. These and previous results indicate that ovulation rate and uterine capacity are genetically independent. Therefore, simultaneous selection emphasis on both ovulation rate and uterine capacity are necessary to produce greater increases in litter size.