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Effect of Restriction of Energy during Lactation on Body Condition, Energy Metabolism, Endocrine Changes and Reproductive Performance in Primiparous Sows¹

North Carolina State University Raleigh 27695-7621

Abstract

Seventeen Landrace – Large White primiparous sows that farrowed in August 1982 were fed ad libitum (AL, n=8) or their intakes were restricted (R, n=9) during lactation. Litter sizes were equalized after farrowing and pigs were not allowed creep feed. Pigs were weaned 23.8 ± .4 d postpartum. On d 6, 12 and 20 postpartum, all sows were fasted for 16 h and blood samples were collected prior to feeding for analysis of plasma glucose (GLU), urea nitrogen (UN), free fatty acids (FFA), prolactin (PRL) and serum insulin (INS). On d –2, 2 and 4 from weaning, sows were fasted for 16 h and then blood samples were collected hourly from 0 to 6 h postprandial for analysis of GLU, UN, FFA, PRL and INS. Serum for analysis of luteinizing hormone (LH), progesterone and estradiol was collected every 6 h from 1 d before until 12 d after weaning. Samples for LH were also collected at 15-min intervals for 3 h at –18, –6, 6, 18, 78, 102, 126, 150, 240 and 480 h from weaning. After weaning all sows were fed 1.8 kg·d^–1, and were checked for estrus twice daily. Daily intakes of metabolizable energy (ME) during lactation were greater in AL (12,194 ± 465 kcal) than in R sows (8,144 ± 90 kcal). Compared with AL sows, R sows lost more weight and backfat during lactation and had higher postprandial UN levels 2 d before and 4 d after weaning, Reproductive performance and reproductive hormones were not affected by restriction of energy, but frequency of episodic release of LH prior to weaning was greater in sows that exhibited estrus after weaning (n=12) than in anestrous sows (n=5). After weaning, LH and estradiol concentrations were similar between estrous and anestrous sows until onset of the preovulatory increase in estradiol in the sows that exhibited estrus. Energy intake, body condition and productivity were similar between anestrous sows and sows that exhibited estrus. On d 12 and 20 of lactation, preprandial levels of GLU were greater and FFA were lower in anestrous than estrous sows. We conclude that restriction of feed intake during lactation affected body condition and metabolism of primiparous sows, but reproductive performance and productivity were not affected. Aberrations in partitioning of energy during lactation may predispose primiparous sows to postweaning anestrus, but the mechanisms by which this occurs have yet to be defined.

¹ Paper No. 10326 of the Journal Series of the North Carolina Agr. Res. Serv., Raleigh. The use of trade names in this publication does not imply endorsement by the North Carolina Agr. Res. Serv. of the product named, nor criticism of similar ones not mentioned.

² Dept. of Anim. Sci., North Carolina State Univ., Box 7621, Raleigh, NC 27695-7621.

³ Richard B. Russell Agr. Res. Center, Agr. Res. Serv., USDA, Athens, GA 30613.