Effect of feed intake during pregnancy on productive performance and grazing behaviour of primiparous sows kept in an outdoor system under tropical conditions

Twenty-four primiparous sows were allocated randomly in four blocks distributed through a year to evaluate the effect of feeding level on productive performance and grazing behaviour of primiparous pregnant sows kept outdoors under tropical conditions. Three diets designed to supply 19 (L), 26 (M) and 33 (H) MJ of DE/day were used. The sows had opportunity to graze freely in a paddock of star grass (SG). Total weight gain (kg) from mating to weaning increased linearly as feeding level increased (L: 30.5, M: 36.3, H: 48.7; P < 0.05). However, sows in treatment L had a negative balance in back fat depth (mm) (L: - 1.3, M: 0.5 H: 3.6; P < 0.05) during the same period. Time spent grazing (min/day) (L: 130.4, M: 96. 1, H: 67.8; P < 0.05) grazing activity (%) (L: 17.4, M: 13.2, H: 9.2; P < 0.05) and distances walked (meters) (L: 305.8, M: 185.8, H: 169.8; P < 0.05) reduced significantly with dietary energy intake. Rectal temperature (T) increased significantly (P < 0.05) as energy intake increased (L: 38.9, M: 39.1, H: 39. 1; P < 0.05). The average ambient temperature recorded during daytime in block IV was higher (34.0 degrees C) than average ambient temperature recorded in block I (29.6 degrees C), II (29.5 degrees C) and III (28.8 degrees C). There was a significant (P < 0.05) treatment X block (season) interaction for distance walked. Also, a significant (P < 0.05) block X days of pregnancy (D) interaction for grazing time, distances walked and rectal temperature. In our experimental conditions, 26 MJ DE/day was sufficient to ensure live weight gain and back fat gain during pregnancy in primiparous sows. Increases in feed intake during pregnancy reduced grazing behaviour during daytime and increased the rectal temperature. The interactions observed suggested that extremely high ambient temperature had more effect on grazing behaviour and body temperature than energy intake in pregnant sows kept outdoors under tropical conditions. (c) 2002 Elsevier Science B.V. All rights reserved.