Large Group Auto Sort: Potential and Problems

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Summary

Large Group Auto Sort (LGAS) systems are being used successfully on a number of operations. In general they are achieving their potential in terms of sorting pigs for market. They are infrequently used to sort pigs towards different diets, even though considerable potential exists for improved efficiency. Loss of productivity remains a significant problem on some operations, although better designed food courts and better training generally address the problem. LGAS requires the collaboration and dedication of the manufacturer/distributor, the farm manager, and staff to ensure its success.

Introduction

Large Group Auto Sort (LGAS)is a relatively new system that applies electronic technology to the management of grow-finish pigs. The ability of the modern industry to assemble several hundred animals of a similar weight into one pen has made the application of electronic scales and sorting gates cost effective. But the method has received mixed reviews. A number of operations have removed the scales or are using them at less than their planned efficiency, yet others are enthusiastic about the benefits to their operation. We have been monitoring progress in the technology over the past few years, been involved in a producer satisfaction survey, and are conducting a series of trials at our PSC Elstow Research Farm. LGAS has a number of potential advantages, but a number of problems have also been identified.

Potential

1. Reduced labour at sorting. Rather than herding pigs to and through a set of scales, LGAS weighs and sorts pigs as they enter the food court.
2. Hitting the grid. Pigs can be sorted for market the day before shipping, reducing the error involved in pulling pigs based on week-old weights.
3. Split phase feeding. Large and small pigs within the same pen can be fed separate diets that better match their nutrient requirements. Although recognized as a potential for the system, it is rarely practiced. Most systems have not installed additional feed lines that would be needed to accomplish this option.
4. Paylean management. As pigs approach market weight they can be sorted to the heavy feed court to receive Paylean for the maximum allowable period. All pigs in the group can receive Paylean rather than the final two market groups. Again, this potential has rarely been achieved.
5. Easier handling, reduced losses during transport. Easier handling and loading has been anecdotally reported, and transport surveys have confirmed an advantage of LGAS.

Problems

1. Poor performance. The most successful operations report losses of less than 3% in average daily gain, but some report in excess of 10%. Food court design probably accounts for much of this discrepancy. It is critical that the food court provide easily accessible feeding spaces.
2. Training of pigs. LGAS only works if pigs move easily through the scale enroute to the food court. Most producers favour a gradual training method in which the food court is accessible through several openings for the first few weeks. These openings are gradually closed until the pigs must enter through the scale only. Fewer than 5% of pigs should fail to learn the system.
3. Managing the pigs. Although pigs in LGAS are generally as healthy as pigs in conventional pens, they do require health checks and occasional treatment. Health checking requires walking through all areas of the pen. Relief pens, for suspect animals at the beginning of the grow-out period, for those requiring treatment, and for those that fail to learn the system should be provided and used.
4. Managing the program. Although the software is generally easy to manage, there is a learning curve. Managers must ensure that their staff understands the need to monitor pig performance and ensure the program sorts properly.
5. Manufacturer/distributor support. A number of operations have indicated that they could have used more support from the manufacturers or distributors in planning their system, installation, and initial operation.

Although results from LGAS are improving, and the majority of operations that have used them would install them again, some operations continue to report substantial problems even though they have done everything according to recommendations. The causes of these problems are sometimes difficult to identify, and some producers consider the program a failure.

Further Research at Prairie Swine Centre

In 2005, two fully-slatted large group grower-finisher rooms with capacity for 280 pigs each were modified to include auto sorters. A series of studies have been proposed to identify aspects of pen layout, design and pig behaviour that are limiting productivity or impacting on pig behaviour. The first series of studies will be completed in early 2007 and look at the question of handling ease and indicators of stress at transport and comparing pigs housed in large groups (approx 280 pigs/pen versus small groups (18 pigs per pen).
During the grow-out period animals will be housed and managed as per typical industry norms in each housing system. Measures included on days of transport. Physiological sampling for breathing rate, body temperature, skin blotching and cortical (hormone levels). These measure were taken in the barn, on the truck and at the packing plant
After being off leaded from the truck. Comparison of these indicators of stress will help to determine any physiological differences on animals that may lead to differences in ease of handling at market. Additional observations of speed of pig movement at leading and the amount of required use of pushing or use of prod were also made.
Implications

Manufacturers, distributors and managers must be aware that LGAS requires their attention during the design, installation, and initial operating phases. Only when staff feel comfortable with the day to day management of the system will LGAS be capable of achieving its potential. The potential to differentially feed animals of different weights within a pen is yet to be achieved, and requires greater attention to feed delivery systems.

Grower/Finisher Room: Achieving 95% Core Weights

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The variability of pigs that go to slaughter resulted in a loss in 2002 of $3.63 per pig. Dressed weight at market needs to be adjusted, as it is farm specific, and continue to be adjusted as various market factors fluctuate. Sort losses are a huge contributor to pig variability. This variability results in a variety of weights of pigs going to market, less targets being hit, and a reduction in net returns to the farm. To reduce sort losses, producers can define the barn’s optimum market weight, based on financial returns, determine the barn’s capacity for shipping some pigs sooner, to reduce heavies, or some pigs later, to reduce lights, weigh pigs, and address variability. Smaller pigs growing faster, decreasing disease, and ensuring adequate access to feeders and drinkers can control uniformity of pigs. Variability can be managed by pre-sorting the pigs into predicted groups of performance, removing lighter weight pigs at weaning to increase throughput, and not mixing gilt offspring with sow’s offspring due to compromised immunity of the gilts offspring.

Auto-sorting Technology Receives International Focus

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Saskatoon – How many pigs does it take to make a pen? This question is the focus of a workshop held at the Prairie Swine Center Focus on The Future Conference, March 27 & 28 in Saskatoon.

“This workshop is designed to bring together experienced operators to discuss and demonstrate through their operation some of the key factors that determine the success, including pig training, personnel training, equipment selection, and barn design” notes Dr. Harold Gonyou, Research Scientist with Prairie Swine Centre.

Lee Whittington, Manager of Information Services at Prairie Swine Centre points out the considerable experience of the speakers on the program, “We will have two farms discussing their systems, with Cliff Her of Humboldt, Saskatchewan, and Don Huftalin of Malta, Illinois. Mr. Her is the grow-finish production manager with Big Sky Farms, and has constructed 45,000 large groups housing spaces with auto-sort technology. Mr. Huftalin and his family operate a 2000 sow farrow to finish farm, using 18 auto-sorters spread over two states, with internet links allowing management of the barns and auto-sorting equipment from the home farm”

“This technology offers opportunities as well as some significant challenges to farm operators” notes Dr. Gonyou, “By having this discussion we are in a position to assist farms in making wise choices for incorporating new technology based on experience as well as recent research, it also gives the industry an excellent opportunity to help develop plans for future research in this area.”

Registration for the conference can be made by phone 306-373-9922, fax 306-955-2510, or email ken.Engele@usask.ca

Prairie Swine Centre Inc., located in Saskatoon, is a non-profit research corporation affiliated with the University of Saskatchewan, and is recognized globally for its contributions to practical, applied science in pork production in the disciplines of Nutrition, Engineering and Animal Behaviour.

Effect of Ractopamine in Finishing Swine Diets – Economics

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SUMMARY
Pigs were fed a control diet, or that diet supplemented with 5 ppm ractopamine for an average of 27 days. Ractopamine improved growth and feed conversion, decreased backfat and improved loin thickness. The economic benefit accruing from the use of ractopamine will depend on market prices, grading grids and the current farm’s carcass quality. Based on our experiment we estimate a “typical” return in the range of $2 to $3 per pig sold.

INTRODUCTION
Paylean® is a feed additive that was recently registered in Canada. The active ingredient of Paylean® is ractopamine, a beta-adrenergic agonist known to stimulate muscle growth and inhibit lipid growth. The final decision to use Paylean® will depend on the relative economics. Similar to other feed additives, there is a cost to using this product. Apart from the cost of the product there are costs associated with the additional nutrients and management required to exploit the performance expected with Paylean®.

MATERIALS AND METHODS
Approximately 530 animals were assigned to receive either a control or a diet supplemented with Paylean® to supply 5 mg/kg ractopamine (RAC). This was to provide an average of 28 days on Paylean® prior to slaughter.
All animals were fed a diet comparable to the barn’s normal gilt finisher, The experiment consisted of two treatments: control or 0.25% Paylean®, equivalent to 5 ppm ractopamine (RAC). Except for total lysine which was increased to 1.00 % and the 5 ppm ractopamine; the Paylean®-fed pigs were fed a diet formulated to the same specification as the controls.

All pigs were shipped to Mitchell’s Gourmet Foods in Saskatoon. Shipping occurred once per week. Pigs were shipped at 116 kg. Market weights were recorded on the morning prior to marketing. The room was completely emptied on week 14 of the growout period (week 6 of the experiment) as per normal barn procedure. Pigs not attaining 116 kg after 14 wk of growout are classified as tail-enders.

Carcass weight, backfat and loin thickness, estimated lean yield, carcass index and carcass loin premiums were recorded at the packing plant according to Mitchell’s standard grid.

Because the economic impact of using ractopamine is dependent on individual farm circumstances, the calculations used different scenarios. We assumed a market price of $1.40 kg and a net market value of $149.00. Other assumptions are described under the appropriate table.

RESULTS and DISCUSSION
Table 1 shows the performance and carcass parameters, which influence the economics of pork production. Additionally, the feed costs, associated with the use of ractopamine are described.

Based on our data, the use of RAC would permit the close-out of a room or barn approximately one week earlier. Assuming that pigs are available to refill that room one week earlier, the net return per pig place would increase by almost $5.00 per year (Table 2). Alternatively, the number of tail-end pigs could be reduced. Reducing the proportion of tail-end pigs from 7.5 % to 0.75 % would increase gross income by about $2.17 per pig sold in a $1.40 /kg market and assuming the tail-end pigs weigh an average of 81 kg, have an average index of 101.9 and receive a loin bonus of $1.86,

If producers are operating under a grading system that does not penalize heavier carcasses, the increase in growth rate could be converted directly into heavier pigs sold (rather than pigs of the same weight sold earlier). Using the growth data obtained from our experiment, and accounting for the additional feed required the return over feed cost would be an additional $3.94 per pig sold (Table 3).

RAC decreased back fat thickness by 1 mm and increased loin thickness by 2.5 mm. In gilts, where backfat was unchanged and loin thickness increased by 2.4 mm, carcass index actually declined by 0.3. In barrows, backfat was reduced by 1.8 mm and loin thickness increased by 2.6 mm, carcass index actually increased by 1.6. Based on the results of our experiment, this increase in carcass index would increase grow income per pig by only $0.80 in a $1.40/kg market.

The increase in loin thickness observed as a consequence of using RAC would increase loin premiums on most farms. However, in our experiment, the control pigs already had a loin thickness of 68.3 mm, and loin premiums dropped from $3.50 to 0.50 when loins exceeded 70 mm.. However, if average loin thickness is 62.8 mm (Mitchell’s Gourmet Foods, personal communication) and assuming a standard deviation of 6.8 mm (PSC Elstow Research Farm, unpublished) RAC would decrease loin premiums from $2.56 to $2.46 (Table 4). A change in loin premiums would dramatically alter this scenario.

CONCLUSION
The actual benefit accruing from the use of RAC will depend on individual farm circumstances. However, based on our data, the “typical” farm will see a return of $2 to $3 per pig sold. Transit losses must be controlled.

ACKNOWLEDGEMENTS
Strategic funding provided by Sask Pork, Alberta Pork, Manitoba Pork Council and Saskatchewan Agriculture and Food Development Fund. Specific funding for this project from Elanco Animal Health is gratefully acknowledged.

Grower/Finisher Room: Large Group Pens: Making them Work

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As pig production continued to increase in the past, the need for regrouping pigs to maximize space efficiency became necessary. Studies show that the larger the group of pigs, the less fighting that occurs. This will lead to better carcass quality. An initial reduction in growth rate in large pens should not be worried about because it will balance out at the end. A shift in the dunging area should not be confused with poor ventilation. Health checking in large pens involves getting in amongst the pigs and walking in a set pattern to observe. Weighing and sorting can be a challenge, which is why some producers elect to weigh and sort in small groups at a time and/or in a designated area. Auto sort systems have the potential to be efficient but reports have been variable. There should be adequate feeder space for the stage of production required and the pig’s first trip through the feeder should be pleasant and stress-free. With good management practices auto sort feeders can be very good for successful sorting and weighing of large groups of pigs.

Conference Tackles Emerging Disease Challenge

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Saskatoon – Post-weaning multi-systemic wasting syndrome (PMWS) is the focus of day one of the Focus on the Future conference held in Saskatoon March 27 & 28. Practical methods of identifying, and dealing with the disease and its impact on herd performance are the subject of the first day of the conference.

Lee Whittington, Manager of Information Services at the Centre notes, “We have assembled leading speakers on the disease and Circo virus, the main causative agent, to address the defenses available to pork producers in protecting their herds, identifying the problem in the barn since many pork producers will have not seen it yet, and some of the solutions available to deal with the problem including new vaccination programs.” Dr. Frank Marshall, a swine practitioner from Camrose, Alberta will lead off the program documenting what the disease is and where to look for it in the barn.

Dr. John Harding, Associate Professor at the Western College of veterinary medicine in Saskatoon and one of the speakers on the program comments on the disease “PCV2 certainly has some unique characteristics and outcomes that have not been fully understood from a scientific point of view. This only reemphasizes the importance of control and prevention strategies that focus on control of concurrent diseases in the herd and the use of PCV2 vaccines if available.”

Dr. Francois Joisel, our keynote international speaker and a researcher with Merial in France will be addressing the area of vaccine development and how this recent advancement in vaccine technology can be added to the pork producer’s defense strategy.

Dr. Harding reminds pork producers across Canada “Until further research and experience can help us to determine with some certainty what are the factors which cause this disease to devastate production in one herd and hardly impact performance in another herd we need to use all the tools available to us to limit any disease entry into the barn and minimize the impact of concurrent diseases that may already exist in the barn.”

Registration for the conference can be made by phone 306-373-9922, fax 306-955-2510, or email ken.Engele@usask.ca

Prairie Swine Centre Inc., located in Saskatoon, is a non-profit research corporation affiliated with the University of Saskatchewan, and is recognized globally for its contributions to practical, applied science in pork production in the disciplines of Nutrition, Engineering and Animal Behaviour.

Effect of Ractopamine in Finishing Swine Diets – Meat Quality

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INTRODUCTION
Paylean® is a feed additive that was recently registered in Canada. The active ingredient of Paylean® is ractopamine, a beta-adrenergic agonist known to stimulate muscle growth and inhibit lipid growth. There is limited information available on the impact of RAC on the eating quality of pork and the results available are equivocal. Moreover, few studies used taste panel evaluation. Those studies that did evaluate meat quality suggested that RAC had no effect on visual colour, firmness, marbling or sensory juiciness and flavour properties. However, the effect of RAC was inconsistent for some quality traits, specifically, meat tenderness or Warner-Bratzler shear force. The acceptance of pork by the consumer is critical to the industry’s success, therefore it is important to determine if RAC has an impact on eating quality. The data reported here was from a larger trial (see part 1). The specific objective of part 2 was to evaluate the impact of feeding 5 ppm RAC on meat quality and the sensory characteristics of pork.

MATERIALS AND METHODS
The experiment was designed so that the average starting weight within a treatment would be 87 kg. This was to provide an average of 28 days on Paylean prior to slaughter.
All animals were fed a diet comparable to the barn’s normal gilt finisher, The experiment consisted of two treatments: control or 0.25% Paylean®, equivalent to 5 ppm ractopamine (RAC).

In each of two weeks, a total of 8 animals from each gender and treatment (32 animals per week) selected for shipping, were randomly selected for detailed meat quality analysis. Loin eye area and backfat measurements were determined following chilling. Loins were harvested one day post-slaughter, and cut into one inch chops for measurement of drip loss, subjective colour scores, chemical composition, sensory evaluation and shear force. Sensory analysis was conducted using 11 trained panellists. They were provided individual cubes of meat cooked to an internal temperature of 70 C.

RESULTS and DISCUSSION
Similar to the results shown by those feeding ractopamine at 10 ppm or 20 ppm, including ractopamine in the diet at 5 ppm did not markedly affect meat quality parameters (Table 1). pH, drip loss, and visual colour scores were unaffected (P > 0.05). Changes in some of the colour scores were statistically significant, however, the absolute differences are of uncertain significance from a consumer perspective.

Our observation that RAC had no effect on marbling is consistent with some published reports, but not others. The lack of an effect in our study may be due to our low inclusion rate. The decrease in back fat, and improvement in loin-eye area are consistent with the known nmechanism of action of ractopamine.

The increase in shear force, and decreases in observed tenderness supports previous reports that RAC may produce less tender pork. The effect of RAC on shear force was more pronounced in gilts, than barrows. Overall acceptability however, was not affected by the inclusion of RAC in the diet at 5 ppm (Table 2).

ACKNOWLEDGEMENTS
Strategic funding provided by Sask Pork, Alberta Pork, Manitoba Pork Council and Saskatchewan Agriculture and Food Development Fund. Specific funding for this project from Elanco Animal Health is gratefully acknowledged.

Effects on behaviour and performance following regrouping in pigs

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Regrouping of unfamiliar pigs is a common management practice, which usually occurs at several stages of the pig’s life. Every time pigs are regrouped, a new social structure must be formed (Meese and Ewbank, 1973). This results in aggression in which pigs will fight intensely for approximately 2 h. Less intense fighting will continue to occur over the next couple of days, until a relatively stable structure or organization is formed.
The aggression that results is a serious animal welfare concern. This concern has prompted many studies to investigate methods of reducing the regrouping aggression.
Some examples that have not been very successful include masking odours, using sedatives (Luescher et al., 1990), providing hide areas (McGlone and Curtis, 1985; Luescher et al., 1990) and environmental enrichment (Schaefer et al., 1990; Arey and Franklin, 1995). Behavioural differences among pigs can be reliably determined using the human approach test. This study investigated the theory of ‘pre-forming’ a stable hierarchy based on behavioural composition. While in the nursery with littermates, 222 pigs were individually tested in two human approach tests and classified as either being slow, medium, or fast to approach a novel person. Pigs were then regrouped at eight weeks of age. Groups of 12 pigs, consisting of either all slow (uniform slow), all fast (uniform fast), or slow, medium, and fast (diverse) were formed. Intact litters were used as a control treatment. Subsequent aggression, average daily gain, and approach times were assessed. Regrouped pigs took longer to approach than pigs in intact litters (28.6 versus 9.25 ± 3.03 s; P = 0.02) during the final human approach test. There was less fighting per pig in the intact litters (0.45) compared with regrouped pigs (greater than 3.61 ± 0.45 s; P < 0.01). Pigs in the intact litters tended to grow faster than pigs in the uniform fast treatment (863 versus 805 ± 21.6 g/day; P = 0.09). The slow pigs in the intact litters, diverse and uniform-slow treatments all became faster to approach over time (P < 0.05), and did not differ in average daily gain. Whereas, fast pigs in the intact litters became slower to approach than fast pigs in the diverse treatment (49.4 ± 8.61 versus 3.4 ± 7.04 s; P = 0.02) and tended to take longer than the uniform-fast pigs (49.4 ± 8.61 versus 26.7 ± 7.04 s; P = 0.09). There were no differences in average daily gain among fast pigs in any of the treatments (P > 0.1). The human approach test is useful for distinguishing among individuals. Regrouping affects the ability to habituate over time. Furthermore, the type of regrouping strategy influences the ease of habituation. Pigs that are initially classified as slow, medium, or fast may habituate differently to the test. The pigs also have different growth patterns depending on whether they have experienced regrouping. Behavioural uniformity tended to result in more aggression and less weight gain, when compared to intact litters.

New Research to Optimize Use of Canola for Swine

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Saskatoon – Dr. Pascal Leterme, Research Scientist in Nutrition at Prairie Swine Centre, is new to western Canada but not the swine research community. Although he only joined the Centre’s research team in August 2005, he has already garnered significant support for a new research effort in optimizing the use of canola for swine.

Dr. David Hickling, Vice President of Canola Council of Canada, which is funding the project in cooperation with the Saskatchewan Canola Development Commission, underlines the importance of this novel research approach, “Increasing the energy value of canola is important to ensuring pork producers make the best use of this ingredient in western Canada. This research will help us define the areas of greatest opportunity to improve the product through plant breeding, processing or the use of dietary enzymes.”

“This research will provide us with significant insight into how the energy from canola is utilized by the pig”, notes Dr. Leterme. “Firstly we will be looking at the difference between how young growing pigs utilize energy differently from adult sows. We believe that there is not one energy value but two for canola depending on the maturity of the animal’s digestive system”. Dr. Leterme notes this approach, using a sophisticated Net Energy system, could have a significant impact on the efficiency and cost of practical farm diets.
“Secondly, we want to look at the whole seed, rather than just processed canola meal as an energy and protein source for swine. This approach will contribute to our understanding of the nutritional impact of crushing canola and whether there is an opportunity to increase energy content for the pig.” This project also provides the opportunity to use whole canola seed as an ingredient.

Mr. Roy Button, Executive Director, Saskatchewan Canola Development Council, reinforces why they are funding this type of research. “Saskatchewan produces 40% of Canada’s Canola and is located in the heart of western Canada’s pig industry with a third of the nation’s pork producers within easy access.
“Canola seed is 58% meal and 42% oil, knowing the Net Energy of this product improves the value of the meal and thus the value of the seed to our growers.”

Prairie Swine Centre Inc., located in Saskatoon, is a non-profit research corporation affiliated with the University of Saskatchewan, and is recognized globally for its contributions to practical, applied science in pork production in the disciplines of Nutrition, Engineering and Animal Behaviour.

Effect of Ractopamine in Finishing Swine Diets – Performance and Carcass Composition

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SUMMARY
Ractopamine at 5 ppm/kg feed improved growth and feed efficiency by 13% when fed for an average of 26 to 27 days. Ractopamine decreased backfat and improved loin thickness. Transit losses were higher in the ractopamine fed group.

INTRODUCTION
Paylean® is a feed additive that was recently registered in Canada. The active ingredient of Paylean® is ractopamine, a beta-adrenergic agonist known to stimulate muscle growth and inhibit lipid growth. It has been registered in numerous countries around the world and is actively used by the pork industry in those countries to improve the profitability of pork production. Because the marketing and grading systems in Canada differ from those in other countries, there was a need to evaluate this product locally.
The overall objective of this experiment was to evaluate the effectiveness of Paylean, fed to deliver 5 ppm ractopamine on performance, carcass characteristics, carcass quality and the economics of pork production in finishing pigs.

MATERIALS AND METHODS
The experiment was designed so that the average starting weight within a treatment would be 87 kg. This was to provide an average of 28 days on Paylean prior to slaughter. All available pigs in two rooms (1 room started each week) at PSC Elstow were randomly allocated within gender to one of 8 pens. Only pigs with obvious health problems were excluded from the experiment so the variation observed was typical of normal practise.
At the end of the room turn, all remaining pigs were weighed and any feed remaining in the feeder was weighed. Any pigs failing to achieve the minimum market weight at the end of the room-turn were marketed and carcass information obtained from the packing plant. The number of “light” or “tail-ender” pigs was recorded by gender and treatment.
All animals were fed a diet comparable to the barn’s normal gilt finisher, The experiment consisted of two treatments: control or 0.25% Paylean®, equivalent to 5 ppm ractopamine (RAC). Except for total lysine which was increased to 1.00 % and the 5 ppm ractopamine; the Paylean-fed pigs were fed a diet formulated to the same specification as the controls.

RESULTS and DISCUSSION
A total of 271 barrows, and 259 gilts started the experiment (Table 1). During the experiment 5 pigs were removed from the experiment, all for reasons unrelated to the trial. Three RAC gilts died during transport to market, and two RAC barrows were condemned at the plant. In this size of experiment, we can’t conclude that these deaths were a result of treatment or were a random effect. However, it has been suggested by others that RAC pigs may be more susceptible to stress during shipping.
Average daily gain was 13% higher in the RAC pigs, relative to the controls (P < 0.001); genders responded similarly. There was no effect of treatment on feed intake, thus feed conversion also increased by 13% in the RAC pigs (P < 0.001). Because they grew more efficiently, the RAC pigs used about 11.5 kg less feed than the control pigs to reach market weight. Thus, this experiment confirms that even at 5 ppm, RAC has positive effects on growth rate in both barrows and gilts. The RAC pigs were on test an average of 26.5 days; the control pigs, 30.1 days (Table 1), thus tail-enders were reduced in the RAC group. Table 3 shows weekly pig performance, within treatment, according to the week in which the pig was marketed. It can be seen that during the first week of the experiment, except for those pigs shipped during week 5, the RAC pigs consistently outperformed the control treatment. However, these slower growing pigs appeared to respond to RAC during their second week on test. For the pigs marketed during the 5th and 6th weeks of the experiment, the response to RAC had diminished. As shown in Figure 1, because of the faster growth by the RAC pigs during the initial weeks of the experiment, more control than treatment pigs were shipped during the final two weeks. This decline in the response to RAC with longer exposure to the product is well documented. The faster growing pigs (> 1.3 kg/d) demonstrated a 13 % increase and the slower growing pigs (< 1.3 kg/d) had a 7 % improvement in growth rate during the first two weeks of the experiment. The faster growth of the RAC pigs reduced the number of tail-end pigs from 7.5 % to 0.8%, a noteworthy response because of the heavy penalties associated with marketing lightweight pigs. Table 4 describes the carcass response to RAC. Dressing percent was unaffected by treatment (P > 0.20). RAC reduced backfat thickness by an average of 1 mm (P < 0.02); however, this decrease was 1.8 mm in barrows and only about 0.3 mm in gilts (trt by gender, P = 0.06). Loin thickness was increased by 2.5 mm, lean yield was improved (P < 0.001) and carcass index tended to improve in the RAC treated pigs (P = 0.06). This results are consistent with the mode of action of RAC CONCLUSIONS Including RAC in the diet at 5 ppm, results in faster growth rate, increased carcass lean and faster barn throughput. The response to RAC diminishes if pigs receive it for more than 28 days. ACKNOWLEDGEMENTS Strategic funding provided by Sask Pork, Alberta Pork, Manitoba Pork Council and Saskatchewan Agriculture and Food Development Fund. Specific funding for this project from Elanco Animal Health is gratefully acknowledged.