GROWTH AND REPRODUCTIVE-PERFORMANCE, DURING EXPOSURE TO AMMONIA, OF GILTS AFFLICTED WITH PNEUMONIA AND ATROPHIC RHINITIS

From 2 to 4.5 months of age, 80 crossbred gilts were reared in a conve ntional grower unit where they were naturally exposed to mycoplasmal a nd bacterial pathogens that cause pneumonia and atrophic rhinitis. At 4.5 months of age, gilts were moved to environmentally regulated rooms (4.3 x 7.3 m) and assigned at random to 1 of 2 treatment groups: low aerial concentration of ammonia (4 to 12 ppm; mean, 7 ppm) or moderate aerial concentration of ammonia (26 to 45 ppm, mean, 35 ppm). Low con centration of ammonia was obtained by flushing of manure pits weekly, whereas moderate concentration of ammonia was maintained by adding anh ydrous ammonia to manure pits that were not flushed. Gilts were weighe d biweekly. Mean daily gain (MDG) was less (P < 0.01) for gilts expose d to moderate concentration of ammonia than for gilts exposed to low c oncentration of ammonia after 2 weeks in their respective environments . By 4 and 6 weeks, however, MDG was similar between the 2 treatment g roups. After 6 weeks in these environments, 20 gilts from each treatme nt group were slaughtered, and prevalence and severity of lung lesions and snout grades were determined. At slaughter, body weight was great er (P < 0.01) in gilts exposed to low, rather than moderate, ammonia c oncentration (94.5 vs 86.8 kg; SEM, 3.3 kg). Percentage of lung tissue containing lesions (18 vs 12) and snout grade (2.8 vs 3.1) were simil ar between gilts exposed to low or moderate concentration of ammonia. The remaining 20 gilts in each treatment group were maintained in thei r respective environments, exposed daily to mature boars and bred at f irst estrus. Age at puberty was similar between gilts exposed to low o r moderate concentration of ammonia (208 vs 205 days; SEM, 1.3 days), even though weight at puberty was less (P < 0.03) for gilts exposed to low concentration of ammonia than for gilts exposed to moderate conce ntration of ammonia (109.7 vs 118.2 kg; SEM, 4.5 kg). At day 30 of ges tation, number of live fetuses (10.6 vs 11.7), fetal length (2.53 vs 2 .57 cm), and fetus-to-corpus luteum ratio (0.85 vs 0.78) were similar between gilts at low and moderate ammonia environments. These data ind icate that exposure of gilts to mean aerial ammonia concentration of 3 5 ppm in environmentally regulated rooms depressed MDG for 2 weeks, bu t failed to alter onset of puberty or litter size at day 30 of gestati on.