EFFECT OF TRANSPORT CAGE HEIGHT ON BROILER LIVE SHRINK AND DEFECATION PATTERNS

Transcription

1 2001 Poultry Science Association, Inc. EFFECT OF TRANSPORT CAGE HEIGHT ON BROILER LIVE SHRINK AND DEFECATION PATTERNS N. L. TAYLOR, D. L. FLETCHER 1, J. K. NORTHCUTT, and M. P. LACY Department of Poultry Science, University of Georgia, Athens, GA Phone: (706) FAX: (706) Primary Audience: Poultry Processors, Researchers SUMMARY A series of eight trials was conducted to determine the effect of transport cage height on broiler defecation patterns during holding. Prior to treatment, broilers were held in pens with free access to feed and water. In each trial, birds were randomly placed into nine experimental cages, allowing a bird density of 447 cm 2 /bird. Cages were constructed of wire with perforated wooden tops set at internal heights of 15.2 cm (short), 22.9 cm (normal), or 68.6 cm (tall). The normal height was determined as an average for commercial broiler transport cages. Cages with broilers inside were weighed, placed over preweighed manure catch pans, and held for 8 h at 26 C; the cages and the pans were reweighed to determine live shrink and excreta weight. In the first two trials, birds held in the short cages had a significantly greater live shrink than the broilers in the normal or tall cages. However, observations that the cage designs might have adversely affected ventilation led to a redesigning of the tops using wire fabric to improve ventilation. In the following six trials, cage height had no significant effect on live shrink (4.2%) or excreta (1.8%). These results indicate that transport cage height, relative to bird posture during transport, had no significant effects on live shrink or defecation patterns of broilers. Key words: Broiler live shrink, live bird holding, transport cage 2001 J. Appl. Poult. Res. 10: DESCRIPTION OF PROBLEM Feed and water are routinely withdrawn from market-aged broilers prior to slaughter to allow sufficient time for voiding of the digestive tract to minimize the potential for carcass fecal contamination during evisceration. To be effective, the feed withdrawal period should be long enough for adequate intestinal emptying but short enough to limit live weight loss, or broiler live shrink, due to feed deprivation [1, 2, 3]. Commercial feed withdrawal schedules vary widely, with most companies scheduling broilers for slaughter after 8 to 12 h of feed withdrawal; however, these times are frequently shifted to accommodate plant operations. In practice, feed withdrawal begins in the grow-out house where broilers have access to water but not feed for 2 to 5 h before catching and caging. The remaining feed withdrawal time (3 to 10 h) is spent in cages during transit or at the plant. Because of the zero tolerance fecal requirement in the USDA s Pathogen Reduction, HACCP ruling, which prohibits carcasses with visible fecal con- 1 To whom correspondence should be addressed.

2 336 JAPR: Research Report tamination from entering immersion chillers, poultry companies are re-examining feed withdrawal programs on intestinal evacuation and reduction of carcass contamination [4, 5]. Previous research has shown that environmental conditions as well as length of feed withdrawal can affect live shrink. Hale [6] described a seasonal effect on live shrink. It was noted that high environmental temperatures combined with long holding times caused excessive live shrink [6]. Shackleford et al. [7], Kettlewell [8], and Hoxey et al. [9] also reported increased weight losses due to high environmental temperatures. These environmental extremes, along with other factors such as broiler health, feeding programs, excitement during the withdrawal period, light or dark conditions during feed withdrawal, and length of time broilers are held in cages before processing have been reported to affect the rate of digestive tract clearance [5, 10, 11, 12, 13]. Because of these factors, the rate of live shrink for market-aged broilers held without feed for 8 to 24 h has been reported to vary between 0.18 and 0.6% of the bird s body weight per h of feed withdrawal [1, 5, 13, 14]. Summers and Leeson [15] reported that broilers held in cages during feed withdrawal retained intestinal contents longer than broilers left on litter with access to water. Farr [16] indicated that the physiological stress on broilers caused by catching and caging resulted in an immediate halt in absorption of intestinal contents by the broilers for several hours. Savage [17] suggested that feed clears a broiler s crop and proventriculus within the first 4 to 5 h of feed withdrawal, provided water is available. These findings conflict with those of May and Deaton [10] who compared intestinal contents of broilers after feed withdrawal when birds were held in cages, held on litter without water, or held on litter with water available ad libitum. It was reported that broilers held in cages had more material in the crop after 2 and 4 h and more material in the proventriculus and gizzard after 6 h than broilers held on litter, irrespective of water withdrawal [10]. Savage [17] indicated that birds often evacuate while drinking water due to their posture (standing with neck stretched upward). It has also been noted by field personnel that excreta often accumulates near the waterers [18]. Evacuation could be limited during transportation because of the inability of birds to stand in the transport coops. The objective of the present study was to determine the effect of transport cage height on broiler live shrink and defecation patterns during holding. If the bird s postures during holding negatively affected defecation then live shrink and the microbiological status of the birds entering the processing plant could also be affected. MATERIALS AND METHODS One hundred twenty, 5-wk-old male broilers were obtained from each of two separate commercial sources and were transported to the University of Georgia Research Facility. They were held in litter-floored pens in an environmentally controlled house using standard broiler management procedures and with free access to feed and water until they reached 6 wk of age. Each broiler flock was used for four trials. During the study, birds were completely randomized among treatments and replicate trials. A minimum of 3 d between each experimental trial was used to allow birds to partially recover from the stresses associated with handling. CAGES Nine experimental transport cages were constructed using an open wire fabric (square mesh approximately 2.5 cm 2.5 cm). Each cage was 61 cm wide by 66 cm deep, allowing for a ninebird placement density of 447 cm 2 /bird. Cages were constructed with false bottoms of the same wire fabric and were fitted approximately 5 cm over excreta catch pans. Three replicate cages were used with the tops set to allow for internal heights of 15.2 cm (short), 22.9 cm (normal), and 68.6 cm (tall) for each treatment. The normal height was estimated as an average height for commercial broiler transport cages. The short height was determined by observation to not allow the bird to assume an upright or standing posture but would allow limited movement. The tall cages were set such that there was no limitation to the birds standing or vertical postures. In Trials 1 and 2, the cage tops were constructed using perforated wood, and in Trials 3 through 8, the tops were constructed using the same wire fabric as used for the cages to allow for better ventilation.

3 TAYLOR ET AL.: TRANSPORT CAGE HEIGHT 337 EXPERIMENTAL TRIALS For the trials, nine birds were randomly placed into each of the nine cages. The cages with the birds were weighed and placed over preweighed excreta collection pans. Caged broilers were held in the same temperature controlled, enclosed rooms in which they were reared at 26 C for 8 h. At the end of the holding period, the loaded cages and the excreta collection pans were weighed. After weighing, the tops of the cages were opened, allowing birds unlimited ability to stand and move about freely in the open cages, the cages were replaced over the manure collection pans for an additional 10 min, and the excreta pans were reweighed. This procedure was followed to determine if the posture during holding caused decreased evacuation, colon loading, and would result in compensatory defecation. Each excreta catch pan was examined, and cecal plugs were enumerated. STATISTICAL ANALYSIS The weight data were used to determine average bird weight, live shrink, collectable excreta, collectable excreta weight as a percentage of live shrink, and number of cecal plugs per cage [19]. The experimental design consisted of eight trials, three treatments (cage heights), three replicate cages per treatment and trial, and nine birds per cage (total cage observations = 72) [20]. Data were analyzed using analysis of variance option of the general linear model (GLM) procedure, and means were separated using Dun- can s multiple-range option of the SAS/STAT software [21]. RESULTS AND DISCUSSION Table 1 shows the results for bird weight, live shrink, excreta, and excreta as a percentage of total live shrink for Trials 1 through 8. As expected, bird weights increased significantly for the four trials within each flock as the birds aged. There were no significant flock or trial effects for percentage live shrink, percentage excreta, or excreta as a percentage of total live shrink. The results for treatments are shown in Table 2. For Trials 1 and 2, the randomization of birds appeared successful, as there were no significant differences in bird weight by treatment group and no treatment by replicate interactions. A significant difference in live shrink was observed in Trials 1 and 2 (Table 2). Birds in the short cages exhibited significantly more live shrink (5.3%) compared to the birds in the normal height cages (4.3%) and the tall height cages (4.5%). Although this significant difference in live shrink was observed, no significant differences in the collectable excreta, excreta as a percentage of live shrink, or presence of cecal plugs in the excreta were observed for Trials 1 and 2. It was noted that during these initial trials, the birds in the short cages, constrained by a perforated wooden board top, were panting more than those in the other treatments. It was concluded that the increased weight loss of this TABLE 1. Mean (± standard error of the mean) for average bird weight (cage weight/number of birds per cage), percentage live shrink, percentage excreta, and excreta as a percentage of total shrink per cage for Trials 1 to 8 BIRD WEIGHT LIVE SHRINK A EXCRETA B EXCRETA % FLOCK TRIAL (kg) (%) (%) OF SHRINK C g ± ± ± ± d ± ± ± ± b ± ± ± ± a ± ± ± ± h ± ± ± ± f ± ± ± ± e ± ± ± ± c ± ± ± ± 0.6 a h Means within a column followed by different superscript letters differ significantly (P < 0.05). A Live shrink (%) = ((initial live bird cage weight 8 h live bird cage weight)/initial live bird cage weight) 100. B Excreta (%) = (collected cage excreta weight/initial live bird cage weight) 100. C Excreta % of shrink = (cage excreta weight (g)/cage shrink weight (g)) 100.

4 338 JAPR: Research Report TABLE 2. The effect of transport cage height (short, normal, tall) on the mean (± standard error of the mean) average bird weight (cage weight/number of birds per cage), live shrink, excreta, excreta percent of total shrink, and presence of cecal plugs in Trials 1 2, and Trials 3 8 BIRD WEIGHT LIVE SHRINK A EXCRETA B EXCRETA % CECAL TRIALS TREATMENT (kg) (%) (%) OF SHRINK C PLUGS D 1 2 Short 2.21 ± a ± ± ± ± 0.3 Normal 2.16 ± b ± ± ± ± 1.5 Tall 2.22 ± b ± ± ± ± 1.0 P Short 2.39 ± ± ± ± ± 0.5 Normal 2.38 ± ± ± ± ± 0.6 Tall 2.41 ± ± ± ± ± 0.4 P a,b Means within a column followed by different superscript letters differ significantly (P < 0.05). A Live shrink (%) = ((initial live bird cage weight 8 h live bird cage weight)/initial live bird cage weight) 100. B Excreta (%) = (collected cage excreta weight/initial live bird cage weight) 100. C Excreta % of shrink = (cage excreta weight (g)/cage shrink weight (g)) 100. D Cecal plugs = number of cecal plugs per cage. treatment might have been due to evaporative cooling due to inadequate ventilation. Holding temperature has previously been shown to affect live shrink [6, 7, 8, 9]. For this reason, the cage tops were redesigned for Trials 3 through 8, with the same wire mesh used for the cages, to allow better ventilation. After the tops were redesigned, no significant cage height effects on any of the parameters tested were observed in Trials 3 through 8 (Table 1). Birds averaged a body weight of 2.39 kg, a live shrink of 4.2%, and 3 cecal plugs per cage. The live shrink values we observed are consistent with published live shrink values for this period [22]. These data indicate that the posture capability of birds during transport and holding does not affect 8-h defecation or live shrink profiles. Because birds of different ages and weights are often transported in the same containers, the interactions between bird weight and cage height should not influence live shrink or defecation. CONCLUSIONS AND APPLICATIONS 1. Broiler transport cage height had no effect on defecation patterns, live shrink, or cecal shedding. 2. Cage ventilation, as a function of transport cage design (height, solid floors, dimensions, etc.), may have more of an effect on broiler live shrink than cage height on bird behavior. REFERENCES AND NOTES 1. Veerkamp, C.H., Fasting and yield of broilers. Poult. Sci. 65: Lyon, C.E., C.M. Papa, and R.L. Wilson, Effect of feed withdrawal on yields, muscle ph, and texture of broiler breast meat. Poult. Sci. 70: Northcutt, J.K., S.I. Savage, and L.R. Vest, Relationship between feed withdrawal and viscera conditions of broilers. Poult. Sci. 76: USDA Food Safety and Inspection Service, Pathogen Reduction: Hazard Analysis and Critical Control Point (HACCP) Systems; Final Rule. Fed. Reg. 61: Buhr, R.J., J.K. Northcutt, C.E. Lyon, and G.N. Rowland, Influence of time off feed on broiler viscera weight, diameter, and shear. Poult. Sci. 77: Hale, K.K., Effect of diet and harvesting on plant yield of broilers. Proc. Carolina Nutr. Conf. 7. Shackleford, A.D., W.F. Whitehead, J.A. Dickens, J.E. Thomson, and R.L. Wilson, Evaporative cooling of broilers during preslaughter holding. Poult. Sci. 63: Kettlewell, P.J., Physiological aspects of broiler transportation. World s Poult. Sci. J. 46: Hoxey, R.P., P.J. Kettlewell, A.M. Meehan, C.J. Baker, and X. Yang, An investigation of the aerodynamic and ventilation characteristics of poultry transport vehicles: Part I. Full-scale measurements. J. Agric. Eng. Res. 65: May, J.D., and J.W. Deaton, Digestive tract clearance of broilers cooped or deprived of water. Poult. Sci. 68: Rasmussen, A.L., and M.G. Mast, Effect of feed withdrawal on composition and quality of broiler meat. Poult. Sci. 68:

5 TAYLOR ET AL.: TRANSPORT CAGE HEIGHT May, J.D., B.D. Lott, and J.W. Deaton, The effect of light and environmental temperature on broiler digestive tract contents after feed withdrawal. Poult. Sci. 69: Wabeck, C.J., Feed and water withdrawal time relationship to processing yields and potential fecal contamination of broilers. Poult. Sci. 51: Fletcher, D.L., and A.P. Rahn, The effect of environmentally modified and conventional housing types on broiler shrinkage. Poult. Sci. 61: Summers, J.D., and S. Leeson, Comparison of feed withdrawal time and passage of gut contents in broiler chickens held in crates or litter pens. Can. J. Anim. Sci. 59: Farr, A.J., Feed withdrawal: Effects on processing and microbiological quality. Proc. Poult. Processors Workshop, Atlanta, GA. 17. Savage, S.I., Effects of feed withdrawal on contamination. Pages 1, 3, 5 in: Pfizer Animal Health Avian News. Pfizer Animal Health Group, Exton, PA. 18. Savage, S.I., 2936 Summer Rd., Moultrie, GA Personal communication. 19. Live shrink (%) was calculated as [(initial cage weight 8 h cage weight)/initial cage weight] 100. Collectable excreta (%) were calculated as [excreta weight/initial bird weight] 100. Collectable excreta, as a percentage of live shrink, were calculated as [excreta weight/live shrink weight] Because the first two trials were conducted with wooden tops, the data were analyzed with Trials 1 and 2 separately from Trials 3 to 8. Because there were no trial or flock by treatment interactions, the effect of trial was tested using the experimental error term of the trial by treatment by replicate interaction. 21. SAS Institute, SAS/STAT User s Guide for Personal Computers, Release SAS Institute Inc., Cary, NC. 22. Warriss, P.D., L.J. Wilkins, and T.G. Knowles, The influence of ante-mortem handling on poultry meat quality. Pages in: Poultry Meat Science. R.I. Richardson and G.C. Mead, ed. CABI, New York, NY. ACKNOWLEDGMENT This research was supported in part by stat and Hatch funds allocated to the Georgia Agricultural Experiment Station. The authors express appreciation to Reg Smith, Meihua Qiao, David McNeal, and Erica Fletcher for their technical assistance.