EFFECT OF ZERANOL IMPLANTATION ON DAILY GAIN AND CARCASS QUALITY OF BUFFALO BULLS

Dept. of Animal & Poultry Production,

Fac. of Agriculture, Assiut University.

Effect of zeranol implantation on daily gain and carcass quality

of buffalo bulls

 (With 7 Tables)

By

M.N.M. Abd El-Ati

(Received at 20/4/2009)

نأثير زرع الزيرانول على معدل الزيادة اليومية وجودة الذبيحة

فى طلائق الجاموس

محمد نصرت عبد العاطى

إستخدم فى هذة التجربة ستة طلائق من ذکور الجاموس ومتوسط وزنها 311.3 ± 0.74 کجم. قسمت الطلائق عشوائياً لمجموعتين (3 طلائق / مجموعه) طبقاً لوزن الجسم. استخدمت المجموعة الأولى للمفارنة بينما تم زرع الزيرانول ( 36 ملجرام فى قاعدة الأذن اليسرى من الخارج تحت الجلد) فى المجموعة الثانية ثلاثة مرات عند بداية التجربة ثم عند اليوم 75 واليوم 150 من بداية النجربة. تم وزن الطلائق کل إسبوعين ثم ذبحها بعد 150 يوم من آخر معامله ومتوسط وزنها العام 503.33 ± 9.54 کجم.عند اليوم 300 من التجربة. أظهرت النتائج عدم وجود إختلافات عند اليوم 75 بين متوسط وزن الجسم اللمجموعتين ولکن کانت الإختلافات بينهما عند کلآً من اليوم 150 و 225 حيث زادت مجموعة الزيرانول عن المقارنة 0.38 % و 4.7 % على الترتيب. أيضاً أظهرت النتائج أن  المجموعة المعاملة عند نهاية مدة التسمين أعلى 19.9 % فى العائد اليومي الکلي. زاد العائد اليومى عند اليوم 75 و175و225 للمجموعة المعاملة عن المقارنة بنسبة 5.52 و 16.49 و 17.87 % على الترتيب. کان معدل الزيادة اليومية خلال المدة من اليوم الأول حتى اليوم 75 متماثلاً وخلال المدة من اليوم 75 حتى 150 کانت بالنسبة للمجموعة المعامة    0.852 ± 0.076 مقابل 0.822 ± 0.108 کجم لمجموعة المقارنة ومن اليوم 150 حتي 225 زادت معنوياً 0.669 ± 0.039 مقابل 0.407 ± 0.056 کجم بنسبة 64.37 %. نسبة التصافى بالنسبة للوزن الحى کانت 53.6 ± 1.07 مقابل 53.47 ± 1.64 % أو بالنسبة للوزن الحى بدون محتويات القناة الهضمية 61.31 ± 1.84 مقابل 62.63 ± 1.08 % بالنسبة لمجموعة المقارنة أو المعاملة وکانت الفروق غير معنويه. وکانت النسب المئوية للأجزاء الصالحة والغير صالحة للأکل متقاربة بين المجموعتين وکانت نسبة دهن الجسم الکلى (دهن الکلى والقناة الهضمية) المئوية أعلى معنوياً (5 %) فى مجموعة المقارنة   (3.9 %) عن مجموعة الزيرانول (1.64%). لم تختلف المجموعتين فى نسبة الخصيتين المئوية (0.07 %). وکانت نسبة قطعيات الذبيحة الممتازة (الفخذ وبيت الکلاوى ولفلتو) تمثل 57.49 ± 1.82 % و 57.54 ± 1.95 % فى مجموعة طلائق المقارنة والمعاملة ، على الترتيب. زادت مجموعة الزيرانول فى قطعية الکتف عن مجموعة المقارنة وکانت 19.71 ± 0.15 مقابل 19.02± 0.17%. زادت مجموعة المقارنة (1.97 ± 0.18 %) معنوياً بالنسبة لقطعية الفلتو عن مجموعة الزيرانول (1.50 ± 0.03 %) مثلما کانت عضلتى قطعية الفلتو مع دهن بين العضلات أعلى معنوياً عند إحتمال 1 % فى مجموعة المقارنة (2.10 ± 0.08 %) عن المعاملة (1.50 ± 0.03 %). والنسبة المئوية للعضلة الظهرية الطولية المشفاة من قطعية الضلوع الممتازه أعلى معنوياً عند 5 % بالنسبة لمجموعة الزيرانول عن مجموعة المقارنة و کان غالبية النسب المئوية للحوم المشفاة أعلى فى المجموعة المعاملة بالزيرانول عن مجموعة المقارنة ولکن غير معنويه. زادت نسبة الإنکماش بالتبريد فى قطعية الضلوع الممتازه ونسبة السائل الراشح بعد الضغط وقلت نسبة الفقد بالطبخ ونسبة السائل الراشح بعد التجميد فى مجموعة المقارنة بالمقارنة بالمجموعة المعاملة. کانت نسبة اللحم المشفى من قطعية الضلوع الممتازه أعلى معنوياً (1%) فى مجموعة الزيرانول عن مجموعة المقارنة بينما کانت نسبة العظام ودهن بين العضلات  أعلى فى مجموعة المقارنة. أظهرت النتائج عدم وجود فروق معنوية فى التحليل الکيماوي للعضلة الظهرية الطولية بين المجموعتين.

SUMMARY

Six buffalo bulls with an average body weight 311.3 ± 0.74 kg were used in the experiment. Bulls were divided randomly into two groups (3 bulls each) according to their live body weight. The first group was served as a control whereas bulls of the second one were implanted with zeranol (36 mg) three times at 0, 75 and 150 d at the base of the left ear. Bulls were weighed every two weeks and slaughtered 150 days after the last implantation. The overall slaughter body weight mean was 503.33 ± 9.54 kg at 300 d. Average body weights at 75 d, the control and zeranol groups were not differed but at 150 and 225 d the zeranol group was highly differed and not significantly than control group by 0.38 % and 4.7 %, respectively. The treated group had higher total daily gain at the end of fattening period by 14.9 % than the control group. Daily gain at 75, 150 and 225 d of treated group, increased by 5.52 %, 16.49 % and 17.87 % than the control group, respectively. Averages daily gain at different periods of implantation, from 1 to 75 d they were nearly equal. Treated group had 0.852 ± 0.076 vs. 0.822 ± 0.108 kg at 75 d  to 150 d and 0.669 ± 0.039 vs. 0.407 ± 0.056 kg at 150 to 225 d periods with significant (P<0.05) increase at the last period by 64.37 %. Dressing percentage either based on slaughter body weight (53.6 ± 1.07 vs. 53.47 ± 1.64 %) or based on empty body weight (61.31 ± 1.84 vs. 62.63 ± 1.08 %) was not significantly differed between the control and zeranol groups. The edible and non-edible parts percentages were nearly close to each other between groups. Only the total internal body fat (kidney and digestive tract fat) percentages were differed significantly (P<0.05), where the control group was 3.9 % and zeranol group had the lower percentage 1.64 %. Also, the testes percentages of control and treated groups were the same 0.07 %. Choice meat cuts (round, sirloin and fillet) were 57.49 ± 1.72 and 57.54 ± 1.95 % for control and zeranol treated buffalo bulls, respectively. Shoulder meat cut percentage (ratio of left side) of zeranol group was 19.71 ± 0.15 % higher than control one (19.02 ± 0.17 %). Fillet meat cut of the control group was 1.97 ± 0.18 % significantly higher (P< 0.05) than treated group (1.50 ± 0.03 %).The Psoas major and minor muscles in control group (containing intermuscular fat) had higher significant (P< 0.01) percentage 2.10 ± 0.08 % than the zeranol treated animals (1.50 ± 0.03 %). The Longisimus Dorsi muscle percentage (ratio of the left side and best rib cut) which had been dissected from the best ribs meat cut (9^th – 11^th ribs) was significantly (P< 0.05) higher for zeranol treated group 0.80  ± 0.02 % and 28.42 ± 2.08 %  than the control one (0.59 ± 0.07 & 21.13 ± 1.15 %). Boneless tissues of retail meat cuts percentages zeranol implanted buffalo bulls had almost high percentages as a ratio of each retail meat cut. Chilled best ribs joint percent was higher in control group (1.78 ± 0.11 %) than zeranol one (1.11 ± 0.24 %) and the expressible fluid percent was higher but not significant in control group (26.13 ± 1.85 %) compared with zeranol group (24.89 ± 1.14 %). Cooking loss percentages were also correlated to shrinkage percent where the highly shrinkage meat had lesser dripping and cooking losses percentages for the control group. Differences were not significant between groups. Lean meat of dissected best rib cut zeranol group was highly significant (P<0.01) than the control. Bone percentages and intermuscular fat were higher in untreated group than treated one and these differences were not significant. For the chemical analysis of Longissimus Dorsi muscle (dry matter, protein contents, intramuscular fat and ash percentages), no significant differences between treated and non-treated groups were found.

Key words: Buffalo bulls, zeranol, daily gain, carcass.

INTRODUCTION

            To develop an appropriate technology for fattening buffalo is an urgent task. The increase of productivity in both quantity and quality would make buffalo husbandry profitable, which would be a big push to this brand of economy. Buffalo meat is not preferred because of its perception as low in quality (most buffalo meat comes from the culled animals as a result of age and working ability without fattening before slaughter). Actually buffalo meat quality is not lower than cattle beef in any aspect if we raise buffalo for beef.

Compounds that modify animal metabolism, such as anabolic steroid implants, can increase production efficiency (NRC, 1994). Smith et al. (2007) reported that anabolic implants are integrated into the management practices of the finishing phase of US beef production to enhance animal performance (Samber et al., 1996; Duckett and Andrae, 2001) and carcass muscle yield (Johnson et al., 1996 a, b; Roeber et al., 2000). Return on investment from the use of implants is generally positive, but its effect on carcass quality and palatability has not been consistent across studies.

Silcox et al. (1986) concluded that this could be of potential benefit in the utilization of young bulls for red meat production if modification of adverse behavior and carcass masculinity occurs.

Schneider et al. (2007) reported that despite the proven effectiveness of implants for improving growth performance of growing and finishing cattle (Duckett and Andrae, 2001), concerns that the use of implants may reduce carcass quality grade and beef tenderness continue to be expressed (Smith et al., 2006). Research conducted to examine the effects of implanting on beef quality characteristics has shown that some implant programs can result in advanced skeletal maturity (Reiling and Johnson, 2003), reduced marbling scores (Duckett et al., 1997), and decreased beef tenderness (Platter et al., 2003).

Zeranol (6- "6, 1C-dihydroxyundecyl" - resorcylic acid µ-2lactone), (Hall et al., 1977) which is marketed under the commercial brand-name of Ralgro® (Commercial Solvents Corperation, Terre Haute, Indiana, U.S.A.). It is a metabolite of Gibberella zeae (Greathouse et al., 1983) and derived from the mycotoxin zeralenone, that has proven of anabolic effects in cattle (Sharp and Dyer, 1971). Zeranol has been adapted as a growth stimulant, as well as to reduce stress in beef animals and cattle (Olivares and Halford, 1990).

Lamm et al. (1980) indicated that meat from Ralgro-implanted bulls was more desirable than meat from non implanted bulls. Greathouse et al. (1983) revealed that a majority of researchers also have observed that meat from bulls is less tender than from steers (Seideman et al., 1982), although others (Field et al., 1966; Hedrick et al., 1969) have found that meat from young bulls is comparable in palatability to that of steers.

Some reports have indicated that zearalenone, a mycotoxin produced on grains and cereals by Fusarium spp., can be converted to zeranol in the rumen of cattle (Kennedy et al., 1998). It appears that some cattle that never had hormone implants do contain traces of zeranol from eating moldy feed. Plasma clearance of implanted alpha-zearalanol in cattle was rapid and the drug did not accumulate appreciably in any edible tissue. After 65 days, no residues could be detected (Sharp and Dyer, 1972).

The objectives of the study were to determine the effects of zeranol (Ralgro) on buffalo bulls daily gain performance and carcass traits.

MATERIALS and METHODS

Six intact male buffalo bulls averaging 311.3 ± 0.74 kg were used in the experiment. The bulls were divided randomly into two groups (3 calves of each) according to their live body weight. The bulls of the first group were served as control and bulls of the second one were implanted with zeranol (36 mg) three times at 0, 75 and 150 d at the base of the left ear where, the length of time an implant releases growth promotant approximately 75 days for Ralgro® (Dale Zo Bell     et al., 2000). Animals were fed a concentrate mixture containing 40% maize, 35% wheat bran, 20% decorticated cotton meal, 3% limestone and 2% sodium chloride. Also,rice and wheat straw as roughages and water were offered twice daily. Fasted (14 h) buffalo bulls were weighed every two weeks to calculate body weight and daily gain in different implantation times and periods.

            Animals were slaughtered150 days after the last implantation. The overall slaughter body weight mean was 503.33 ± 9.54 kg at 300 d. Slaughter weight was recorded immediately before slaughter to be used in calculating the dressing percent. Weights of hot carcass (HCW) and internal organs were recorded. Left side of every carcass after halving was weighed quartered at 8^th and 9^th ribs into fore and hind quarters then divided into the following retail meat cuts: neck, shoulder, brisket, fore ribs, flat ribs, thin flank, fillet, best ribs, sirloin and round.

            Each meat joint was weighed then deboned and the weight of boneless tissues was recorded. The best ribs cuts (9, 10 and 11th) were dissected into lean meat, fat and bone and weighed. From shoulder, the Suprasspinatus muscle, Psoas major and minor muscles and Semimembranosus muscle from round cuts were weighed.

            A sample of Longissimus Dorsi muscle was taken from each carcass best ribs cut to physical and chemical analysis (Hankins and Howe, 1946 and Unruh et al., 1986), the expressible fluids, chemical composition (after 24 h chilling, AOAC, 1975), cooking and drippings losses (after freezing).

             Data were statistically analyzed using the analysis of variance procedure of SAS (1996).

RESULTS and DISCUSSION

                Table (1) shows that the average body weights at 75 d of the control group and zeranol group were not differed but at 150 and 225 d the zeranol group was highly differed and not significantly than the control group by 0.38 % and 4.7 %, respectively. As well as the treated group had higher total daily gain at the end of fattening period by 14.9 % than the control group. Daily gain at 75, 150 and 225 d of treated group had the same trend of body weight and increased by 5.52 %, 16.49 % and 17.87 % than the control group, respectively. Average daily gain of groups at different periods of implantation, the first one from 1 to 75 d they were nearly equal. But, for the other two periods, the treated group had 0.852 ± 0.076 vs. 0.822 ± 0.108 kg at 75 d to150 d and 0.669 ± 0.039 vs. 0.407 ± 0.056 kg at 150 to 225 d periods with a significant (P<0.05) increase of the last period by 64.37 %.

            The results of the present study indicate that implanting bulls with zeranol, does not significantly alter body weight gain. Similar results have been seen previously in zeranol (Corah et al., 1979; Ford and Gregory, 1983; Juniewicz et al., 1985). In contrast, others have found zeranol or trenbolone acetate plus zeranol to increase live weight gain in bulls (Fabry et al., 1983; Greathouse et al., 1983; Gregory and Ford, 1983).

            It has been postulated that testicular androgens are responsible for the increased growth rate in bulls (Gortsema et al., 1974). Zeranol alters testosterone secretion in young bulls (Juniewicz et al., 1985; Staigmiller et al., 1985; Silcox et al., 1986), but there is little or no influence of zeranol on testosterone secretion or testicular growth in bulls implanted as yearlings or older (Juniewicz et al., 1985; Staigmiller et al., 1985; Silcox et al., 1986). Perhaps bulls overcome the inhibitory effects of zeranol on testis function as they increase in age. Staigmiller  et al. (1985) hypothesized that age at implanting with Table (1) Buffalo bulls average (mean ± S. E.) body weights (BW), and daily gains (DG/d, Kg) at different periods.

* Significant at 5 %.

Zeranol was more critical than the dose of zeranol used in bulls. Higher doses (72 mg vs 36 mg) did not amplify effects in young bulls and did not affect older bulls (Staigmiller et al., 1985).

Silcox et al. (1986) showed that implanting bulls younger 200 d of age with zeranol decreased peripheral testosterone concentration. Lower concentrations of androgens in the peripheral circulation of young bulls may explain the lower response in body growth to zeranol because androgens have been implicated in causing increased body growth rates in bulls (Gortsema et al., 1974). 

Carcass traits:

            Slaughter body weight (BW) kg, hot carcass, edible and non-edible parts percentages (%) of buffalo bulls are shown in Table (2). Dressing percentage either based on slaughter body weight (53.6 ± 1.07 vs. 53.47 ± 1.64 %) or based on empty body weight (61.31 ± 1.84 vs. 62.63 ± 1.08 %) basis was not significantly differed between the control or zeranol groups. As well as, the edible and non-edible parts percentages were nearly close to each other. Only the total internal body fat (kidney and digestive tract fat) percentages were differed significantly (P<0.05). Where the control group was 3.9 % and zeranol group had the lower percentage 1.64 %. Also, it had been noticed that the testes percentages of the control and treated groups were the same 0.07 %.

 This indicates that zeranol had a minimal effect, as an estrogenic agent, and treated bulls did not affected by implantations. Dale ZoBell  et al. (2000) revealed that sufficient endogenous testosterone may have been present in implanted bulls to stimulate growth and carcass traits to levels of control bulls where, higher doses (72 mg vs. 36 mg) did not amplify effects in young bulls and did not affect older bulls (Staigmiller et al., 1985).

Table 2: Slaughter body weight (BW) kg, hot carcass, edible and non-edible parts percentages (%) of buffalo bulls.

* Significant at 5 %.

Failure of zeranol to alter significantly carcass characteristics is consistent with previous reports on bulls (Ford and Gregory, 1983; Gregory and Ford, 1983) and steers (Sharp and Dyer, 1971; Borger       et al., 1973). The superior rate of gain and leaner carcasses of bulls vs. steers is well established (Field, 1971; Seideman et al., 1982), and is thought to be dependent upon testicular testosterone (Gortsema et al., 1974; Galbraith et al., 1978).  

Also, Egan et al. (1993) deduced that zeranol implants had a minimal effect on carcass quality. Hide-off carcass weights (HCWT) were similar among treatments, although they tended to increase (P < 0.l0) with higher doses of zeranol. Mean HCWT was 114.4 kg with a corresponding dressing percentage of 61.4; dressing percentage did not differ among treatments. Lower KPH% scores were present in treated calves than in controls, but the differences were not significant. Also, reduced percent body fat (P<0.05) and increased (P<0.05) percent body water and protein had been also reported by Sharp and Dyer (1970).

Data in Table (3) shows the carcass left side, choice meat cuts and retail meat cuts percentages. Choice meat cuts (round, sirloin and fillet) were 57.49 ± 1.72 and 57.54 ± 1.95 % for control and zeranol treated buffalo bulls, respectively. Shoulder meat cut

Table 3: Retail meat cuts and choice cuts percentages (%) of carcass left side.

* Significant at 5 %.

** Significant at 1 %.

Percentage (ratio of left side) of zeranol group was 19.71 ± 0.15 %higher significant (P< 0.05) than the control group (19.02 ± 0.17 %). However, fillet meat cut of the control group was 1.97 ± 0.18 % higher significantly (P< 0.05) than treated group (1.50 ± 0.03 %). As well as the Psoas major and minor muscles (containing fat) % had the higher significant (P< 0.01) percentage in control group (2.10 ± 0.08 %) than the zeranol treated animals (1.50 ± 0.03 %). The Longisimus Dorsi muscle percentage (ratio of the left side and best rib cut) which had been dissected from the best ribs meat cut (9^th – 11^th ribs) was significantly (P< 0.05) higher for zeranol treated group (0.80  ± 0.02 % and 28.42 ± 2.08 %, Table, 4) than the control one (0.59 ± 0.07 & 21.13 ± 1.15 %). El-Kholy et al. (1997) found also that fillet joint weight was higher for the control group (2.98± 0.12 kg) than Ralgro treated animals (2.92 ± 0.12 kg).

Boneless tissues of retail meat cuts percentages in Table (4) revealed that also the implanted buffalo bulls with zeranol had the almost high lean tissues of the meat retail cuts percentages as a ratio of each retail meat cut. These results are in agreement with
those reported by Jones et al. (1986), Fumagalli et al. (1989) and Keane and Drenan (1990) that implantation with anabolic agents increases lean percentages.

This is more profitable for consumers who have always requested tender, flavorful meat, but because of economics and concern over fat intake, they also prefer products that are mostly free of fat (Dikeman, 1982).

Chilled best ribs joint shrinkage and physically dissected components percentages (Table, 5) shows that the cold shrinkage percent was higher in control group (1.78 ± 0.11 %) than zeranol one (1.11 ± 0.24 %). In zeranol group (Table, 6), where the expressible

Table 4: Percentages of boneless tissues of left side retail meat cuts.

                * Significant at 5 %.

Table 5: Cold shrinkage and physical components percentages of Best ribs joint dissection.

                ** Significant at 1 %.

Table 6: Expressible fluids, drippings and cooking loss of Longissimus Dorsi muscle.

fluid percent was not significantly higher in control group 26.13 ± 1.85 % compared with zeranol group 24.89 ± 1.14 %. This may be due to the higher muscle pH values which improved the water retention (Preston and Willis, 1974), while this shrinkage opens drip channels and results in increased drip loss (Kristensen and Purslow, 2001; Rowe et al., 2001), therefore, less water would be lost initially, and ultimately, would result in a greater water-holding capacity. Cooking loss percentages were also correlated to shrinkage percent where the highly shrinkage meathadlesserdripping and cooking losses percentages for the control group. Differences were not significant between groups. As well as, Greathouse et al. (1983) found that cooking loss percentages were similar (P>.05) for longissimus steaks from non-implanted and implanted bulls.

Lean meat of zeranol group was highly significant (P<0.01) than the control (62.79 ± 0.56 Vs. 55.95 ± 0.51 %). Vanderwert et al. (1985) found higher lean percentage in the best rib cuts (65.92 %) in the animals implanted with zeranol than non-implanted bulls and steers.

Bone percentages were higher in untreated group (23.09 ± 1.47 %) than treated one (19.57 ± 1.20), as well as, the intermuscular fat was 19.99 ± 1.51 % and 16.04 ± 0.55 % for control and zeranol groups, respectively. These differences were not significant. Some implant programs can result in advanced skeletal maturity (Reiling and Johnson, 2003).

The chemical analysis of Longissimus Dorsi muscle (Table 7) has no significant differences between treated and non-treated groups for dry matter, protein contents, intramuscular fat and ash percentages.

Zeranol implants had a minimal effect on carcass traits in these trials. This is in agreement with the findings of Richards et al. (1986). Anabolic combinations that are used to treat veal calves and have neither positive nor negative effects on carcass quality traits of color, pH, protein, collagen, fat, water-holding capacity, nor cooking loss (van Weerden, 1984).

The limited literature concerning meat quality and palatability of implanted steers and heifers indicate minimal differences compared with controls, but implanting young bulls with estrogens (zeranol), starting early in life, may improve carcass quality and palatability (Unruh, 1986).

Table 7: Chemical analysis of Longissimus Dorsi muscle.

REFERENCES

AOAC. (1975): Official Methods of Analysis (llth Ed.). Association of Official Analytical Chemists, Washington, DC.

Borger, M.L.; Wilson, L.L. Sink, J.D. Ziegler, J.H. and Davis, S.L. (1973): Zeranol and dietary protein level effects on live performance, carcass merit, certain endocrine factors and blood metabolite levels of steers. J. Anim. Sci. 36:706.

Corah, L.R.; Fink, L. Kiracofe, G.H. and McKee, M. (1979): Sexual development and carcass traits of bulls after sequential implanting with zeranol. J. Anim. Sci. 49(Suppl. 1): 287.

Dale ZoBell, C.; Kim Chapman and Kevin Heaton (2000): Beef cattle implants. Utah State University extension. Revised from University of Nebraska Publication No. G97-1324-A. By Dee Griffin and Terry Mader. Electronic publishing.

Dikeman, M.E. (1982): Efficient meat production, consumer demands for nutrition and for palatability. In: Proc. Int. Symp. Meat Sci. and Tech. pp 57-60. Award Printing Corp., Chicago.

Duckett, S.K. and Andrae, J.G. (2001): Implant strategies in an integrated beef production system. J. Anim. Sci. 79(E. Suppl.):  E110–E117. 

Duckett, S.N.; Owens, F.N. and Andrade, J.G. (1997): Effects of implants on performance and carcass traits of feedlot steers and heifers. Pages 63–82 in Proc. Symp. Impact Implants Perform. Carcass Value Beef Cattle. Oklahoma State Univ., Stillwater.

Egan, C.L.; Wilson, L.L.; Drake, T.R.; Henning, W.R.; Mills, E.W.; Meyer, S.D. and D.C. (1993): Effects of different doses of zeranol on growth, hemoglobin, and carcass traits in veal calves. J Anim. Sci. 71: 1081-1087.

El-Kholy, F.A.; Salem, M.A.I.; Abdellatif, H.A. and Sami, A.S. (1997): Daily gain, feed conversion and carcass characteristics of Friesian and buffalo males implanted with zeranol. Egyptian J. Anim. Prod., 34(1): 1-10.

Fabry, J.; Renaville, R.; Halleux, V. and Burny, A. (1983): Plasma testosterone and LH responses to LHRH in double-muscled bulls treated with trenbolone acetate and zeranol. J. Anim. Sci. 571 286.

Field, R.A. (1971): Effect of castration on meat quality and quantity. J. Anim. Sci. 32: 849.

Field, R.A.; Nelms, G.E. and Schoonover, C.O. (1966): Effects of age, marbling and sex on palatability of beef. J. Anim. Sci. 25: 360.

Ford, J.J. and Gregory, K.E. (1983): Effects of Late Castration and Zeranol on Feedlot Performance and Carcass Characteristics of Bovine Males. J Anim. Sci. 57: 286-291.

Fumagalli, A.; Verde, L.S.; Moore, C.P. and Fernandez, H.M. (1989): The effect of zeranol on live weight gain, feed intake and carcass composition of steers during compensatory growth. J. Anim. Sci., 67: 3397-3409.

Galbraith, H. and Watson, H.B. (1978): Performance, blood and carcass characteristics of finishing steers treated with trenbolone acetate and hexoestrol. Vet. Rec. 103: 28.

Gortsema, S.R.; Jacobs, J.A.; Sasser, R.G.; Gregory, T.L. and Bull, R.C. (1974): Effects of endogenous testosterone on production and carcass traits in beef cattle. J. Anim. Sci. 39:680.

Greathouse, J.R.; Hunt, M.C. Dikeman, M.E.; Corah, L.R.; Kastner, C.L. and Kropf, D.H. (1983): Ralgro-Implanted Bulls: Performance, Carcass Characteristics, Longissimus Palatability and Carcass Electrical Stimulation. J Anim. Sci. 57: 355-363.

Gregory, K.E. and Ford, J.J. (1983): Effects of late castration, zeranol and breed group on growth, feed efficiency and carcass characteristics of late maturing bovine males. J. Anim. Sci. 56: 771.

Hall, Ga.B.; Savain, J.; Figueiro, P.R.P. and Muller, L. (1977): Zeranol implantation for suckling ram lambs weight gain and Development of the reproductive tract. Trop Anim Prod 1977 2:2

Hankins, O.G. and Howe, P.E. (1946): Estimation of the composition of beef carcasses and cuts. USDA Tech. Bull. No. 926.

Hedrick, H.B.; Thompson, G.B. and Krause, G.F. (1969): Comparison of feedlot performance and carcass characteristics of half-sib bulls, steers and heifers. J. Anim. Sci. 29:687.

Johnson, B.J.; Anderson, P.T.; Meiske, J.C. and Dayton, W.R.  (1996a): Effect of a combined trenbolone actetate and estradiol implant on feedlot performance, carcass characteristics, and carcass  composition of feedlot steers. J. Anim. Sci. 74: 363–371. 

Johnson, B.J.; Hathaway, M.R.; Anderson, P.T.; Meiske, J.C. and Dayton, W.R. (1996b): Stimulation of circulating insulin-like growth factor I (IGF-I) and insulin-like growth factor binding proteins (IGFBP) due to administration of a combined trenbolone acetate and estradiol implant in feedlot cattle. J. Anim. Sci. 74: 372–379. 

Jones, S.D.M.; Newman, J.A.; Tong, A.K.W.; Martin, A.H. and Robertson, W.M. (1986): The effect of two shipping treatments on the carcass characteristics of bulls implanted with zeranol and unimplanted steers. J. Anim. Sci., 62: 1602-1608.

Juniewicz, P.E.; Welsh, T.H. Jr. and Johnson, B.H. (1985): Effects of zeranol upon bovine testicular function. Theriogenology 23: 565.

Keane, M.G. and Drenan, M.J. (1990): Comparison of growth and carcass composition of heifers in three production systems and steers and effects of implantation anabolic agents.Ir. J. Agric. Res., 29: 1-13.

Kennedy, D.G.; Hewitt, S.A.; McEvoy, J.D., Currie, J.W.; Cannavan, A.; Blanchflower, WJ and Elliot, C.T. (1998): Zeranol is formed  from Fusarium spp. toxins in cattle in vivo. Food Addit.  Contam; 15(4): 393–400.

Kristensen, L. and Purslow, P.P. (2001): The effect of ageing on the water-holding capacity of pork: role of cytoskeletal proteins. Meat Sci. 58: 17–23.

Lamm, W.D.; Kelly, R.F.; McClure, W.H. and Fontenot, J.P. (1980): Effect of zeranol implants on performance of suckling calves and growing finishing bulls and heifers. J. Anim. Sci. 51 (Suppl. I): 377.

NRC. (1994): Metabolic Modifiers. Effects on the nutrient requirements of food-producing animals. National Academy Press. Washington, D.C.

Olivares, V.H. and Halford, D.M. (1990): growth and carcass characteristics and serum growth hormone, plrolactin and insuline profiles in Debouilet lambs treated with Ovine growth hormone and (or) zeranol. J. Anim. Sci., 68: 1971.

Platter, W.J.; Tatum, J.D.; Belk, K.E.; Scanga, J.A. and Smith, G.C. (2003): Effects of repetitive use of hormonal implants on beef carcass quality, tenderness, and consumer ratings of beef palatability.J. Anim. Sci. 81: 984–996.

Preston, T.R. and Willis, M.B. (1974): Intensive beef production. Pergamon press Ltd., Headington Hill Hall, Oxford OX3 0BW, England.

Reiling, B.A. and Johnson, D.D. (2003): Effects of implant regimens (trenbolone acetate-estradiol administered alone or in combination with zeranol) and vitamin D3 on fresh beef color and quality. J. Anim. Sci. 81: 135–142.

Richards, J.E.; Mowat, D.N. and Wilton, J.W. (1986): Ralgro implants for intact male calves. Can. J. Anim. Sci. 66: 441.

Roeber, D.L.; Cannell, R.C.; Belk, K.E.; Miller, R.K.; Tatum, J.D. and Smith, G.C. (2000): Implant strategies during feeding: Impact on carcass grades and consumer acceptability. J. Anim. Sci.  78: 1867–1874. 

Rowe, L.J.; Huff-Lonergan, E. and Lonergan, S.M. (2001): Desmin degradation influences water-holding capacity and tenderness of fresh pork. J. Anim. Sci. 79(Suppl. 1): 443. (Abstr.)

Samber, J.A.; Tatum, J.D.; Wray, M.I.; Nichols, W.T.; Morgan, J.B.  and Smith, G.C. (1996): Implant program effects on performance and carcass quality of steer calves finished for 212 days. J. Anim.  Sci. 74: 1470–1476. 

SAS (1996): SAS User’s Guide, statistics (6.2th Ed.) Cary NC: SAS Institute Inc.

Schneider, B.A.; Tatum, J.D.; Engle, T.E. and Bryant, T.C. (2007): Effects of heifer finishing implants on beef carcass traits and longissimus tenderness. J Anim Sci 2007.85: 2019-2030.

Seideman, S.C.; Cross, H.R.; Oltjen, R.R. and Schanbacher, B.D. (1982): Utilization of the intact male for red meat production: A review. J. Anim, Sci. 55: 826.

Sharp, G.D. and Dyer, I.A. (1970); Metabolic responses to zearalanol implants. . J. Anim. Sci.30: 1040 (Abst.)

Sharp, G.D. and Dyer, I.A. (1971): Effect of zearalanol on the performance and carcass composition of growing-finishing ruminants. J. Anim. Sci. 33: 865.

Sharp, G.D. and Dyer, I.A. (1972): Zearalanol metabolism in steers. J. Anim. Sci., 34, 176-179.

Silcox, R.W.; Kecton, J.T. and Johnson, B.H. (1986): Effects of zeranol and trenbolone acetate on testis function, live weight gain and carcass traits of bulls. J. Anim. Sci. 63: 358-368.

Smith, G.C.; Savell, J.W.; Morgan, J.B. and Lawrence, T.E. (2006). Final report of national beef quality audit-2005: A new benchmark for the US beef industry. Natl. Cattlemen’s Beef Assoc., Centennial, CO.

Smith, K.R.; Duckett, S.K.; Azain, M.J.; Sonon, R.N. Jr. and Pringle, T.D. (2007): The effect of anabolic implants on intramuscular lipid deposition in finished beef cattle. J. Anim. Sci. 85:      430-440.

Staigmiller, R.B.; Brownson, R.M.; Kartchner, R.J. and Williams, J.H. (1985): Sexual development in beef bulls following zeranol implants. J. Anim. Sci. 60: 342.

Unruh, J.A. (1986):Effects of endogenous and exogenous growth-promoting compounds on carcass composition, meat quality and meat nutritional value.J Anim. Sci. 62: 1441-1448.

Unruh, J.A.; Gray, D.G. and Dikeman, M.E. (1986): Implanting young bulls with zeranol from birth to four slaughter ages: I. Live measurements, behavior, masculinity and carcass characteristics. J Anim. Sci. 62: 279-289.

Van Weerden, E.J. (1984): Carcass quality of veal calves given anabolic agents. In: J. E Roche and D. O'Callaghan (Ed,) Manipulation of Growth in Farm Animals. pp 112-121.

Vanderwert, W.; Berger, L.L.; McKeith, F.K.; Baker, A.M.; Gonyou, H.W. and Bechtel, P.J. (1985): Influence of zeranol implants on growth, behavior and carcass traits in Angus and Limousin bulls and steers. J. Anim. Sci., 61: 310-319.