Abstract
Heat stress (HS) is one of the costliest issues in the U.S. pork industry. Aims of the present study were to determine the consequences of repeated exposure to HS on growth performance, and the effects of a high fiber diet, the genetic potential for high lean tissue accretion, and the genetic potential for residual feed intake (RFI) on resilience to HS. Barrows (n = 97) from three genetic lines (commercial, high RFI, low RFI) where subjected three times to a 4-day HS treatment (HS1, HS2, and HS3) which was preceded by a 9-day neutral (TN) adaptation period (TN1) and alternated by 7-day periods of neutral temperatures (TN2, TN3, and TN4). Body weight gain (BWG), feed intake (FI), feed conversion efficiency (FCE), RFI, and the drop in BWG and FI between TN and HS were estimated for each period, and slaughter traits were measured at the end of TN4. Commercial pigs had lower FI when fed a high fiber diet compared to a regular diet (2.70 ± 0.08 vs. 2.96 ± 0.08 kg/d; P < 0.05), while no differences were found for BWG, RFI or FCE. HS reduced FI, BWG, and FCE, increased RFI, and resulted in leaner pigs that generate smaller carcasses at slaughter. In TN, commercial pigs grew faster than the low and high RFI pigs (1.22 ± 0.06 vs. 0.720 ± 0.05 and 0.657 ± 0.07; P < 0.001) but growth rates were not significantly different between the lines during HS. Growth rates for the low RFI and high RFI pigs were similar both during TN and during HS. Pigs of interest for genetic improvement are those that are able to maintain growth rates during HS. Our results show that response in growth to HS was repeatable over subsequent 4-d HS cycles, which suggests the potential for including this response in the breeding index. The best performing animals during HS are likely those that are not highly superior for growth in TN.
Highlights
Despite aggressive heat stress (HS) abatement strategies, the U.S swine industry loses at least $900 million/year to HS (Pollmann, 2010)
Results for loin aye area (LEA) and back fat thickness (BFT) at TN1 and TN4, and for loin depth (LoinD), hot carcass weight (HCW), and Lean% at slaughter are given in Table 4, for each line
None of these traits were significantly different between pigs fed high vs. low fiber diets
Summary
Despite aggressive heat stress (HS) abatement strategies, the U.S swine industry loses at least $900 million/year to HS (Pollmann, 2010). Sources of reduced revenue include slower growth rates, inconsistent market weights, altered carcass traits, infertility, increased health care costs and mortality. Pigs’ Response to Heat Stress compromises the industry’s capacity to efficiently produce animal protein for human consumption (Baumgard and Rhoads, 2013). The effect of HS will likely become more of an issue if the frequency of severe hot weather increases as predicted (USDA, 2015). A depression in both feed intake and growth rate in HS is a common observation in all heat-stressed livestock (BrownBrandl et al, 2004). Whereas animals that grow faster have higher FCE, RFI is phenotypically independent of body weight gain but highly correlated with feed intake (Crews, 2005). Depending on the extent to which HS affects growth and feed intake, it may affect both measurements of feed efficiency differently. Heat stress mediated changes in energy metabolism may result in changes in carcass quality (Pearce et al, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
