Determination of the impact of housing system on the determination of apparent total tract digestibility of energy and dry matter

Abstract Text: Swine digestibility trials are primarily carried out in metabolism crates, which provide the most accurate data on total input and output.  However, this limits research to having access to crates and the facilities to maintain them, in addition to studying a relatively small group of pigs.  If researchers were able to run digestibility studies on a larger scale, the data would be more applicable to producers, and more reflective of a commercial setting.  The objective of this experiment was to determine if apparent total tract digestibility (ATTD) outcomes would be similar among 3 different fecal collection housing systems: group pen (GP; n=8 with 20 pigs per pen), individual pen (IP; n=8) or metabolism crate (MC; n=8). One hundred seventy six gilts (PIC 337 X C22/29) with an average initial weight of 48.5 ± 0.3 kg were assigned to penning treatment according to body weight and received a standard grower diet for 7 days with titanium dioxide added at 0.4%.  Fresh fecal samples were collected morning and late afternoon on each of days 5, 6, and 7, immediately frozen and later homogenized within pen and assayed for dry matter, gross energy and titanium dioxide content. Data were analyzed according to the randomized complete block design using PROC MIXED (SAS 9.3) with pen as the experimental unit. Housing system did not impact body weight (P=0.58) or average daily feed intake (P=0.15).  ATTD of DM increased as pen size decreased (MC=83.53 %, IP=80.40 %, GP=79.13 %; P<0.01).  Similarly, ATTD of GE matched this trend, increasing as pen size decreased (MC=84.08 %, IP=81.29 %, GP=79.96 %; P<0.01).  However, DE was different between MC and IP/GP (3.71 vs 3.56/3.53 Mcal/kg as fed; P<0.01). ADG was greater in GP compared to IP or MC (1.06 vs 0.88 vs 0.90 kg/d; P<0.01), but there was no significant difference between IP and MC (P>0.10). These data indicate that collecting feces in pens – either group or individual - will result in lower estimates of the ATTD of energy and dry matter and of DE than in MC.  This means that it may be advantageous for applied research to be done in both metabolism crates and group penning in order to have the most accurate assessment of ATTD of a diet prior to applying it to a commercial setting.

Keywords: swine, digestibility, methodology, housing