Effects of tropical climate and water cooling methods on growing pigs' responses

We report a study on crossbred growing pig ((Duroc x Pietrain) x Large White) that measured the effect of tropical conditions on respiration rate (RR), skin temperature (ST), rectal temperature (RT) and productivity and determined the efficacy of two simple cooling methods. The experiment was a randomized complete block design using 120 growing pigs. The factors were cooling system and pen design. The effects of two cooling systems (water bath (WB) and sprinkling (S)) were evaluated and compared with a control (CON). Cooling systems were tested in pens with (Y) or without an additional outdoor yard (NY). The pens were similar to those used in small-scale pig keeping in South-East Asia. The inside pen size was 2.5 x 3 m, the yard was 2.5 x 2 m. The same experimental design was used in two blocks: one block was in the wet season with average ambient temperature (T) of 27.5 degrees C and average relative humidity (RH) of 74.7% and the other was in the dry season with average T of 28.7 degrees C and average PH of 62.8%. In each block a batch of 60 pigs was reared in 12 pens (five pigs per pen). Pigs had free access to feed and water. Results showed that cooling and pen type significantly affected most parameters. The bath and S reduced RR by 4.2 and 5.2 min(-1), respectively (P < 0.01), and ST by 0.3 and 0.4 degrees C, respectively, (P < 0.05). Rectal temperature was not influenced by any treatment. The bath significantly reduced number of defecations and urinations in the resting area in pens NY (P < 0.001). A yard reduced the number of excretions in the resting area (P < 0.01). There were significant interaction effects of cooling and pen type on lying, lateral lying, and huddling (P < 0.01; P < 0.001; P < 0.01, respectively). Daily weight gain was 6 g d(-1) more with WB and 50 g d(-1) more with S (P < 0.05). The biggest daily weight gain was achieved when S was combined with a pen NY (P < 0.01). We conclude that the physiologic and behavioral responses and hence productivity of group-housed growing pigs raised under tropical climate conditions benefited from the simple cooling systems tested and were affected by the presence of a yard. A fall in the high respiration rate indicated that cooling with the bath or sprinkling alleviated the pigs' heat stress. (c) 2006 Elsevier B.V. All rights reserved.