Ractopamine hydrochloride, also known as PAYLEAN 9 and PAYLEAN 45 in the USA, is a dietary supplement for the cattle. This beta adrenergic agonist increases the muscle weight and decrease the fat volume in the cattle. The energy taken from the fat is redirected to the increase of muscle fiber diameter. In this way the muscle protein grows and the number of days to market reduces. Nowadays ractopamine is widely used in the livestock sector.
"Feeding ractopamine hydrochloride (RAC; 200 mgÂ·animalâˆ’1Â·dâˆ’1) to steers influences animal performance and carcass quality in a positive manner." (Golzales et al, 2010)
Though the muscle growth response was observed in many species, the official approval of the US Food and Drug Administration initially allowed ractopamine use only in swine. The legislation of other countries, however, allows mode wide use of ractomapine in the livestock sector.
The objective of this research is to overview the latest articles related to ractomapine use, to summarize the results and findings and to make the conclusion about the affect of ractopamine hydrochloride on carcass traits in slaughter cattle.
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Affect of actopamine hydrochloride on carcass traits in slaughter cattle
"Ractopamine hydrochloride (RAC) and zilpaterol hydrochloride (ZH) are Î²-adrenergic agonists that improve growth performance and affect carcass characteristics."(Scramlin et al, 2010) The use of ractopamine hydrochloride in livestock sector is an issue of economical and ethical discussions. To improve feedlot performance the beef industry continues modifying practices to improve efficiency. The result is the development of dietary additives and the different methods of implementation of them (Scramlin et al, 2010). The use of ractopamine hydrochloride allows decreasing the number of days to market and to obtain the lean meat. Thus, its economic value for livestock sector is very high. However, there are some negative aspects in ractopamine hydrochloride use. The information regarding the influence of ractopamine on humans is insufficient due to the lack of proved and systemized data. However, some indirect data (particular the impact of ractopamine hydrochloride on pigs) allows the supposition that this additive can cause the arrhythmia, sickness, sleep disorders and even addition in human. Recently the Chinese media published a set of publication regarding the cases of human poisoning in some Chinese region with ractopamine in swine meet. Thus, the "existing data on the effects of ractopamine-HCl on growth performance and carcass characteristics for finishing feedlot heifers need to be refined"( Quinn, 2010). This research can contribute to the general information about the consequences of ractopamine use.
Due to habit-forming and the lack of the results after the long feeding FDA recommends to use ractopamine hydrochloride no more than last two-three weeks before slaughtering "at a dietary concentration of 4.5 to 9.0 g of ractopamine hydrochloride per ton of feed" (FDA, NADA 140-863, 2006) The swine weighting at the beginning of ractopamine hydrochloride feeding should be no less than 150 lbs. In average the swine should gain the last 45 to 90 lbs during the period of ractopamine feeding. It is important to understand the percent of the meat weight and carcass weight before and after ractopamine diet to make the conclusion about this supplement affect.
The group of scientists from the Department of Animal Sciences and Industry, and Department of Statistics, Kansas State University studied growth-related responses to ractopamine in steers and heifers (Walker et al, 2006). Nowadays the findings of this group is considered as the most significant contribution in the study of ractopamine effect in carcass traits. The main objective of their research was to understand the different effectiveness of ractopamine between sexes. However, some of their findings can be useful for this research. Thus, according the previous studies the ractopamine affects hot carcass weight in steers and heifers differently:
"Hot carcass weight has been increased by 8 (Winterholler et al., 2007), 6 (Laudert et al., 2004), and 5.5 kg (Gruber et al., 2007) in feedlot steers fed ractopamine. In feedlot heifers, HCW was increased by 4.6 (Laudert et al., 2007) and 2.9 kg (Schroeder et al., 2005a) in response to ractopamine."(Walker et al, 2010).
The research of Grouber's group from the Department of Animal Science, Colorado State University, is also the important contribution in this issue. This was the first group that studied the affect of the ractopamine in feedlot heifers. This group noticed the degradation of the fat tissue, the increase of muscle weight, the decrease of tenderness in meat, the shift in the proportion of muscle fiber with a corresponding increase in muscle fiber diameter (Grouber et al, 2007)
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The other research of scientists group from Illinois provides the supportive data to the previous research. The group of Dr. Scramlin from the Department of Animal Science, University of Illinois, studied the impact of two dietary addictives, ractopamine hydrochloride (RAC) and zilpaterol hydrochloride (ZH), on cattle. They defined the objective of their study as "was to evaluate the comparative effects of RAC and ZH when fed to beef steers during the last 33 d of the finishing period."(Scramlin et al, 2010) The group of 63 steers were divided onto three groups: control group, RAC-group and ZH-group. During the finishing period steers in RAC group were fed with ractopamine hydrochloride. The dosage of addictive was within the FDA recommended norm. Than the steers were slaughtered using conventional, humane procedures. (Scramlin et al, 2010). After that the researches measured the characteristics of different tissues and organs, including HCW (hot carcass weight). Among other results, the group by Scramlin writes: "Steers supplemented with RAC had a mean increase HCW of 5.3 kg compared with control steers. Previous studies have shown a similar response in carcass characteristics of steers supplemented with ZH and RAC with significantly increased HCW and dressing percentages" (Scramlin et al, 2010). The authors also mention some discrepancy in body weight vs. carcass weight increase. Thus, the impact of RAC of carcass weight was proved with the experiment.
The next group of researches, Quinn et al, is from the Department of Animal Sciences and Industry, Kansas State University. The group conducted two experiments to determine the effects of ractopamine-HCl on the different characteristics including the carcass characteristics. For 28 before slaughter the group of heifers was fed steam-flaked corn diets. One subgroup got 200 mg of ractopamine-HCl per heifer daily, other group was control and got no ractopamine. After 28 days of experiment the cattle was slaughtered, the weight of each pen of heifers was determined, and the slaughter data including hot carcass weight was obtained immediately. The terms of experiments were similar to the mentioned above experiments in Illinois and Kansas. The result of the first experiment was unexpected. The obtained information allows conclusion that "in Exp.1, carcass weight was not affected by the addition of Optaflexx to the diet"(Quinn et al, 2010) The results of this experiment contradicts to the result of some previous researcher, for example, the mentioned above experiment of Walker et al. (2006) and the experiment of Gruber et al. (2007). In these experiments "administration of ractopamine 28 d before slaughter to heifers and steers, respectively, resulted in increases in carcass weight."(Quinn, 2010). However, the result of the second experiment cleared the situation. The doze of Optaflexx in the daily diet of heifers was the same, but the period of feeding with Optaflexx was longer. This time the information about the significant improvement of carcass was obtained.
"Hot carcass weights were not different among treatments. However, there was a tendency for pens of heifers fed Optaflexx to have increased HCW compared with control pens" (Quinn, 2010). This conclusion totally corresponds to the conclusion of Walker et al. (2006) and Gruber et al. (2007)
The result of measurements and the data obtained "would suggest that duration of administration of Optaflexx may play a larger role in improving performance rather than dosage of the compound." The results of some earlier studies contradict to these conclusions: however, all this data allows clarifying the situation with the affect of ractopamine on carcass. The researches provide some recommendations regarding the use of the ractopamine-HCL, or Optaflexx, in finishing heifer diets. To reach the modest improvement in growth performance it is needed to feed the heifer with Optaflexx during the last 14 days. However, the longer duration of feeding can cause the better results, and the longer period of feeding with Optaflexx is more important than the dosage. "There was only an 8.4% improvement in carcass efficiency and no improvement in carcass gain when increasing Optaflexx concentration from 200 to 300 mg per heifer in Exp. 2." (Qulinn 2010) This conclusion support the hypothesis that the better growth performance in independent on Optaflexx dosage. On the other hand, the increase in duration of feeding from 28 to 42 days led to "13.4% improvement in carcass gain that resulted in carcasses weighing 1.3% or 4 kg greater than the 200 28 treatment." (Quinn 2010) Thus, the findings of this research show that the use of Optaflexx affects the carcass traits in slaughter cattle, and the duration of feeding has a significant impact on general growth performance, unlike the dosage.
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At last, the research of the group of Gonzales from the Department of Animal Sciences and Industry, Florida State University, adds the supportive information to the general picture. The group of 88 cows was fed for 54 before slaughter with RAC-containing diet. As in the previous cases, the growth performance was significantly increased, the proportion of muscle mass increased and the volume of fat tissue decreased. The group of Gonzales concluded, however, that "larger muscle fiber CSA stimulated by RAC fed at the recommended dose of the manufacturer (200 mgÂ·headâˆ’1Â·dâˆ’1) does not translate into larger ribeye area" (Conzales, 2010).
The affects of feeding RAC to livestock and the affect of RAC on the carcass characteristics are well documented. It is obvious that the RAC-containing diet increases the volume of muscular tissue because the ractopamine hydrochloride takes the energy from the fat and transforms it into the protein synthesis in muscle tissue. The optimal duration of RCA containing diet is 48-54 days. However, the changes in dosage can't have the significant impact on the general growth performance in the cattle. It allows getting the optimal results in growth performance, as was proved above. However, some findings of these researches are rather vogue and demand the further clarification. For example, the limitation of muscle growth, the proportions of different tissues growth in different terms. Also the influence of RAC-containing meat in humans also should be studied additionally.