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Reproductive performance of gilts having developed in heat stressed dams
First parity Large White x Landrace gilts (Choice Genetics USA) were artificially inseminated and housed under either cyclical thermoneutral (GTN; 18-22ºC) or heat stress (GHS; 28-34ºC) conditions throughout gestation at the University of Missouri (MU) Brody Environmental Chambers. Gilts farrowed in March 2013 and lactated for ~21d under TN conditions, after which piglets were weaned to a mechanically ventilated wean-finish barn at the MU South Farm and raised under commercial conditions with GHS and GTN gilts housed together in pens of 22-25 gilts per pen. On October 7, 123 gilts aged 193-198d were transported to Virginia Tech’s Tidewater Agricultural Research and Extension Center (TAREC). Estrus was recorded and synchronized to facilitate 68 litters born in four farrowing groups. Data were analyzed using ANOVA including treatment, season (March and April vs July and September) and their interaction where appropriate. Gilts were managed together at TAREC, and though anticipated seasonal effects were seen, neither treatment nor treatment x season interaction affected breeding weight, gestation weight gain, nor gestation length. GHS gilts tended to eat more during lactation (5.42±0.115 vs 5.12±0.114 kg/d; P=.07) with no effect on lactation weight loss. Numbers born, born alive or stillborn did not differ significantly by treatment, though numerically all favored GTN gilts (12.06±0.72 vs 12.94±0.72; 11.32±0.67 vs 11.76±0.67; 0.53±0.15 vs 0.47±0.15 for GHS vs GTN, respectively). GHS gilts tended to have lower piglet survival than GTN gilts (88.9±.02% vs 93.9±.02%; P=.08). A numerical non-significant difference of almost one piglet was observed favoring GTN gilts for total piglets weaned per litter (9.91±0.53 vs 10.85±0.53). Further research is needed to quantify reproductive status of gilts developing in utero under heat stress conditions.
Keywords: gestational heat stress, reproduction, gilt