Better Pork - April 2007

Research

Gauging the effect of Paylean® on growth performance and carcass quality

Experimentation suggests that a typical return of $2-$3 per pig sold can be expected with the inclusion of five ppm of ractopamine hydrochloride to the diets of finishing pigs. However, these benefits will be erased if losses during transit are not controlled.

by A. D. BEAULIEU, J.F. PATIENCE and P. LETERME

Canada recently joined 22 other countries in registering ractopamine hydrochloride for use under the brand name Paylean™  (Elanco Animal Health, Guelph.

Initially, at least, the product is being recommended for use at five milligrams per kilo or five parts per million (ppm) for the last 28 days prior to marketing. Paylean breaks down quickly in the body, so there is no withdrawal time required.

Previous research has established that ractopamine hydrochloride (RAC) increases protein synthesis at the expense of fat synthesis within muscle tissue. Thus, RAC results in improved rate and efficiency of gain as well an improvements in carcass composition.

Much of the earlier research on this product was undertaken at higher levels of inclusion in the feed, so information on the response of pigs to ractopamine at the five milligram level is less abundant. Furthermore the Canadian grading system differs from that in other countries, so the conclusions drawn from those studies may not apply in Canada. Also, there have been very few studies that evaluated the impact of Paylean on the eating quality of pork.

Since the acceptance of pork by the consumer is critical, it is important to understand if Paylean has an impact on eating quality, and if so, what is the magnitude of such effects. Therefore, we concluded that any evaluation of Paylean for the Canadian pig industry must consider the impact on growth performance, carcass traits, eating quality and economics. 

The experiment consisted of two dietary treatments: a control finishing diet or a similar diet supplemented with 0.025 per cent Paylean equivalent to five milligrams of RAC per kilogram (see Table 1).

The control diet was typical of that used by the commercial pig industry for pigs fed from 85 kilograms to market. Based on previous research on Paylean, the treatment diet was formulated to contain one per cent total lysine compared to 0.75 per cent in the control (see Table 2) to support the expected increase in lean gain.

The minimum ratio of other essential amino acids to lysine was the same in both diets. The level of vitamin and trace mineral premix was increased by 12 per cent and both calcium and total phosphorus were increased by 0.05 percentage points to ensure that nutrient supply would not impair the pig’s ability to respond to RAC. 

Pigs were marketed when they reached a minimum live weight of 116 kilograms or after the pigs were on test for six weeks, whichever occurred first. Pigs not reaching the minimum marketing weight at the end of the six-week period were considered to be “tail-enders.” On day 28 of the experiment, the two pigs within each pen whose bodyweight was closest to that pen’s mean at the time were selected for more intensive carcass and meat evaluation.

The experiment was conducted at PSC Elstow Research Farm, a 600-sow single-site commercial farrow-to-finish research facility in Saskatchewan. Unlike many past experiments, all pigs available in the two farrowing groups assigned to this experiment were used; there was no pre-selection to achieve a uniform group of pigs.

This was critical, as we wanted to evaluate the impact of Paylean under commercial conditions, so all pigs were placed on test. The only exception was animals excluded to keep the number of pigs balanced in all pens. The feeding of the experimental diets commenced when the average initial weight of the pigs was 86 kilograms.

A total of 531 animals – 259 gilts and 272 barrows – started the experiment. During the experimental period, one control barrow died of splenic torsion and one control gilt became lame and was euthanized. One Paylean barrow was removed from the experiment due to endocarditis and arthritis and two Paylean gilts were removed from the experiment due to severe tail-biting.    

All control pigs were successfully shipped to market, though three Paylean gilts died during transport to market and two Paylean barrows were condemned at the plant. Thus, 99.6 per cent of the control pigs reached slaughter successfully, while 97 per cent of the Paylean pigs did so. In this size of experiment, it is difficult to conclude that these losses were due to the Paylean or were a random effect.

The Paylean pigs were on test an average of 26.5 days, which was very close to the 28-day average anticipated at the start of the experiment. Control pigs were on test for 30.1 days, which was four days longer than the treatment pigs. (P < 0.01). P, is the probability that an observed difference between the intervention and control groups is due to chance alone. Not surprisingly, there were many fewer tail-end pigs on Paylean than on the control treatment. No Paylean barrows and only two Paylean gilts were tail-enders, but there were two control barrows and 18 control gilts that were tail-enders (see Table 2). Based on our results, it would be possible to turn a room around almost one week sooner as a result of using Paylean, an important finding if floor space is limited.

Average daily gain was 13 per cent higher in the Paylean pigs as compared to the controls (P < 0.001) and both genders responded in a similar manner. Interestingly, there was no effect of treatment on feed intake (P > 0.10), so feed conversion also increased by 13 per cent (P < 0.01) in the Paylean pigs. Because the Paylean pigs grew more efficiently, they used 11.5 kilos less feed per pig than the control pigs. 

It is well known that the response to Paylean tends to decline as pigs remain on the product. In the current study, the response to five ppm of ractopamine was consistent during the first four weeks of the feeding period. Indeed, whether the pigs were growing more rapidly (>1.3 kg/d) or more slowly (< 1.3 kg/d), there was a 13 per cent or seven per cent, respectively, increase in average daily gain during the first week on the product.
 
Similarly, during the second week on the product, the response to RAC was observed in both the faster growing and the slower growing pigs. However, for pigs not yet marketed following four weeks on test, the response to RAC was smaller during weeks five and six than observed in weeks one through four. However, it should be noted that by the end of week four, 73 per cent of the Paylean-fed pigs had already gone to market, as compared to only 52 per cent of the control pigs.

The final decision on the use of RAC will depend on relative economics. Based on the results of this experiment, the use of RAC during the finishing period will have significant economic effects, although the impact will be heavily dependent on individual farm circumstances. For example, as shown in Figure 1, the use of RAC would essentially permit the closeout of a room or barn one week earlier. Assuming pigs are available to re-fill that room one week earlier, the increase in net income per pig place in a barn would be substantial. On a very conservative basis, it would increase return per pig place by almost $5 per year in a $1.40 per kilogram market.

Alternatively, if the room cannot be re-filled one week earlier, the number of tail-end pigs could be reduced substantially. Depending on the market price and grading grid employed on a particular farm, reducing the portion of tail-end pigs from 7.5 per cent to 0.75 per cent would increase gross income by about $2.17 per pig sold.

RAC decreased backfat thickness by one millimetre and increased loin thickness by 2.5 millimetres. The impact of these changes in carcass index was surprising, providing much less economic benefit than one might expect.

For example, within gilts, where backfat was unchanged and loin increased by 2.4 millimetres, carcass index actually declined by 0.3.  In barrows, backfat was reduced by 1.8 millimetres and loin thickness increased by 2.6 millimetres; carcass index increased by 1.6. Based on the results of this experiment, the modest increase in carcass index would increase gross income per pig by only $0.80 in a $1.40 per kilogram market. 

However, in some circumstances, producers may be operating under a grading system that does not penalize heavier carcasses, so the increase in growth rate can be converted directly into heavier pigs sold, rather than pigs of the same weight sold sooner.

In this scenario, assuming pigs receive the product for an average of 26 days and increase their rate of gain by 13 per cent, as seen in this experiment, the mean carcass weight will increase by 2.9 kilograms. Adjusting for additional feed required to support the additional gain, the return over marginal feed cost would be $3.94 per pig sold.

John F. Patience, PhD, is president and chief executive of the Prairie Swine Centre, Saskatoon. P. Leterme, PhD, is a research scientist and A. D. Beaulieu, PhD. is a research assistant there.