Jones, O. T. , ANR Extension Agent, Mississippi State University Extension Service
Guelker, L. D., Missississippi State University
Rivera, J. D. , Missississippi State University

ABSTRACT

 

ABSTRACT.  A two-year study was conducted to examine the use of growth promoting implants (GPI) in beef cattle grazing annual ryegrass.  In both years steers were stratified by body weight,  (n = 36, average body weight = 494 in year 1; and n = 48, average body weight = 512 in year 2) and then were randomly assigned within strata to one of three treatments at receiving: no implant (CON), one estradiol 17b implant at receiving (EST) and one zeranol implant at receiving and reimplanted at d 56 (ZER).  According to label directions, EST has a payout window of 200 d.  Following treatment assignment, cattle were allowed to graze annual ryegrass pastures for 120 d in year 1, and 133 d in year 2.  Data were analyzed as a randomized complete block with year used as a random effect.  Preplanned contrasts were used to determine the difference between use of GPI and CON, and between EST and ZER.  No differences (P > 0.05) were noted at d 0, or 28 in body weight (BW); however GPI tended to have an effect on BW at day 56 ( P = 0.09), had greater BW at day 84 and the overall grazing period (P < 0.05).  No differences were noted between EST and ZER in body weight at any time during the study.  Average daily gain (ADG) was not affected by GPI at d 28; however, GPI increased ADG at day 56, 84, 112 and for the overall study (P < 0.05).  No differences were noted between EST and ZER regarding ADG at any time during the study.  Results suggest application of growth promoting beef implants result in increased performance in beef cattle grazing annual ryegrass pastures, with no difference between ZER and EST implants.

Introduction

Over the years, growth promoting implants have been an effective tool for cattlemen as one of the best economic returns per dollar invested in any management practice (Griffin et al. 2008). In a time of cattle market volatility and commodity price uncertainty, beef producers must maximize productivity with technologies which enhance the performance of grazing cattle. It is well documented that implanting beef calves during the stocker phase has been shown to increase ADG by 10 to 15% (Grigsby et al., 1988; Rush et al., 1989; Kuhl, 1997., McMurphy et al., 2013).  Average daily gain improvements of 17.8% credited to GPI have been evident despite winter grazing ADG below .45kg/d (Paisley et al., 1999).  Despite the obvious benefits to producers, the adaptation of growth promoting implants in grazing systems has been poor (USDA-NAHMS, 2008).  Therefore, in an effort to demonstrate effectiveness of growth promoting implants on production of grazing cattle we conducted a two year study examining the use of two implants with label indication for grazing beef cattle, (zeranol and estradiol 17b; Ralgro and Compudose).

 

Materials and Methods. 

All protocols were approved by the Mississippi State University Institutional Animal Care and Use Committee. 

Year 1.  Thirty-six steers with the most uniform BW were selected from a group of 41.  Steers were primarily Bos Taurus (Hereford x Angus) with approximately 25-33% Bos Indicus and were purchased in local sale barns approximately within a 60-mile radius of Mississippi Agricultural and Forestry Exp. Station White Sand Unit.  The White Sand Unit is located approximately 10 miles west of Poplarville, MS.  Once assembled, cattle were processed which included vaccination against respiratory disease and clostridial pathogens and treated for internal parasites.  Additionally, each animal was weighed and given a uniquely numbered ear tag and treated with tilmicosin phosphate as a metaphalaxis.  Intact males (n =3) were surgically castrated.  Once processing was completed cattle were sorted on paper, then moved through the working area again to receive treatment.  Treatments were no implant (CON); one estradiol 17B implant at receiving (EST); and one zeranol implant at receiving and reimplanted at d 56 (ZER). Following treatment assignment cattle were moved to 24 acres of annual ryegrass where they had ad libitum access to water and a complete beef mineral.  Cattle were monitored for symptoms of respiratory disease and treated with ceftiofur hydrochloride (1^st treatment); if no improvement was noted after 48 d, the animal was treated with florfenicol (2^nd treatment). On days 28, 56, 84, 112, and 120 cattle were weighed.  Cattle in the ZEA were reimplanted on d 56, and all animals were administered an anthelmintic at this time as well.  Animals were continuously grazed with a stocking rate of 1000 lb of body weight / acre. Forage availability was estimated using a forage stick, and forage samples were clipped at each weigh period.  Forage samples were composited at the end of the study and submitted to a commercial laboratory for nutrient (DM, CP and ADF) analysis.  Total digestible nutrients were calculated using the formula 88.845 – (0.812 X ADF). At d 120, due to the lack of grass, it was determined that the study terminate. 

 

Year 2.  Forty-eight of the most uniform cattle from a group of 53 were used.  Similar to the previous year, cattle were purchased from local sale barns within a 60-mile radius of the White Sand Beef Unit.  Once assembled, cattle were processed similar to the previous year, with the exception there were more intact males to castrate (n = 12).  Like the previous year, once processing was completed cattle were sorted on paper, then moved through the working area again to receive treatment.  Treatments were no implant (CON); one estradiol 17B implant at receiving (EST); and one zeranol implant at receiving and reimplanted at d 56 (ZER). Following treatment assignment cattle were moved to 36 acres of annual ryegrass where they had ad libitum access to water and a complete beef mineral.  Cattle were monitored for symptoms of respiratory disease and treated with ceftiofur hydrochloride (1^st treatment); if no improvement was noted after 48 d, the animal was treated with florfenicol (2^nd treatment).  On days 28, 56, 84, and 112 cattle were weighed.  Cattle in the ZEA were reimplanted on d 56, and all animals were administered an anthelmintic at this time as well.  At d 112, researchers felt there was sufficient grass to keep cattle until d 140, however due to dry conditions, the study was terminated earlier than anticipated (d 133). Forage and pasture management (stocking rate and forage measurements) were conducted in a similar manner to Year 1. 

 

 

Data management.  Data were analyzed using SAS PROC MIXED; animal was the experimental unit; treatment was a fixed effect and year was a random effect.  Preplanned contrasts were used to determine differences between use of ZEA and EST compared to controls (GPI vs CON), and differences between ZEA and EST.

 

Results

Data are presented in Table 1. 

Table 1.  Performance of cattle administered different implant strategies while grazing annual ryegrass

	Treatments1				Contrast2
Item	None	Est	Zer	SE	None vs Est+Zer	Est vs Zer
Day 0 Body wt	505.4	501.7	501.0	11.0	0.66	0.93
Day 28 Body wt	557.1	554.9	550.8	13.8	0.72	0.77
Day 56 Body wt	636.4	654.2	658.0	15.5	0.09	0.37
Day 84 Body wt	696.5	732.5	726.7	16.7	0.04	0.48
Day 112 Body wt	773.0	807.4	801.6	18.5	0.13	0.28
Final Body wt3	793.5	831.7	826.6	18.2	0.05	0.16
Daily gain 0-28 d	1.85	1.89	1.79	0.28	0.98	0.69
Daily gain 0-56	2.34	2.74	2.80	0.17	0.04	0.18
Daily gain 0-84	2.27	2.77	2.69	0.13	0.01	0.34
Daily gain 0-112	2.39	2.70	2.65	0.12	0.02	0.92
Daily gain 0 to end3	2.29	2.57	2.54	0.16	0.01	0.74

 

In general, nutrient analysis of composite ryegrass pasture samples for both studies were on average 17.92% CP and 67.54% TDN. There were no differences in BW at day 0 and at 28 (P > 0.05); however, cattle administered GPI tended to have greater BW than CON (P = 0.09) at day 56, nonetheless at this time no differences existed between ZEA and EST (P = 0.37).  At day 84, GPI had greater BW than CON (P = 0.04), and there were no differences      (P = 0.48) between implant types.  No differences were noted at day 112 (P = 0.13 for GPI vs. CON and P = 0.28 for ZEA vs EST).  For the overall grazing period, GPI had greater BW compared to CON (P = 0.02) and no differences were noted between ZEA and EST (P = 0.16). 

 

No differences were noted in ADG during the first 28 d (P > 0.05).  The use of GPI resulted in greater ADG from day 0 to 56 (P = 0.04), day 0 to 84 (P = 0.01), day 0 to 112 (P =0.02), and day 0 until the end of the study (P = 0.01).  No differences (P > 0.05) were found between ZEA and EST in ADG during the study. 

Figure 1. Influence of implant type and time period on average daily gain. 

 

 

Discussion

Growth promoting implants in this study increased BW significantly over the grazing period as compared to CON. This is similar to results realized by Paisley et al., (1999) as well as Jones et al., (2016). Also, over the 133d grazing period, ADG was significantly increased by GPI. However, during the first 28d GPI had no significant effect on BW or ADG. The cattle used in the present study were purchased from a local sale facility, and in all likelihood had been recently weaned.  Jones et al. (2016) determined that the stress of weaning may not allow the animals to realize the full potential of GPI.  Based on these findings, stocker enterprises and those cow-calf producers retaining ownership of calves beyond 56 d could benefit from the increased ADG of calves grazing quality forages implanted with GPI’s. No differences for BW or ADG were demonstrated between ZEA and EST in the current study; similarly, Simms et al (1984) noted that use of zeranol and estradiol 17b increased body weight and ADG over controls but did not differ between implant types. Either technology, when used in stocker calf grazing management, will increase production when nutritional requirements are met.

 

 

 

 

Bibliography

 

Brad Jones, H., Daniel Rivera, J., Vann, R. C., & Ward, S. H. (2016). Effects of growth promoting implant strategies on performance of pre- and postweaned beef calves. Professional Animal Scientist, 32(1), 74–81. https://doi.org/10.15232/pas.2015-01411

Duckett, S. K., & Andrae, J. G. (2001). Implant strategies in an integrated beef production system. Journal of Animal Science, 79(E-Suppl), E110. https://doi.org/10.2527/jas2001.79e-supple110x

Grigsby, M., Lofgreen, G. P., Garcia, D. R., Shafer, M., & Branine, M. (1988). Effects of different implants on performance of steers during summer grazing and in the feedlot. Clayton Livestock Res. Center Prog. Rep, 56.

McMurphy, C. P., Linneen, S. K., Mourer, G. L., Holland, B. P., Horn, G. W., & Lalman, D. L. (2013). Effects of stocker-phase grazing system and implantation on performance and carcass characteristics of fall-born steers. Professional Animal Scientist, 29(1), 27–32. https://doi.org/10.15232/S1080-7446(15)30191-1

Brad Jones, H., Daniel Rivera, J., Vann, R. C., & Ward, S. H. (2016). Effects of growth promoting implant strategies on performance of pre- and postweaned beef calves. Professional Animal Scientist, 32(1), 74–81. https://doi.org/10.15232/pas.2015-01411

Duckett, S. K., & Andrae, J. G. (2001). Implant strategies in an integrated beef production system. Journal of Animal Science, 79(E-Suppl), E110. https://doi.org/10.2527/jas2001.79e-supple110x

Grigsby, M., Lofgreen, G. P., Garcia, D. R., Shafer, M., & Branine, M. (1988). Effects of different implants on performance of steers during summer grazing and in the feedlot. Clayton Livestock Res. Center Prog. Rep, 56.

McMurphy, C. P., Linneen, S. K., Mourer, G. L., Holland, B. P., Horn, G. W., & Lalman, D. L. (2013). Effects of stocker-phase grazing system and implantation on performance and carcass characteristics of fall-born steers. Professional Animal Scientist, 29(1), 27–32. https://doi.org/10.15232/S1080-7446(15)30191-1

Paisley, S. I., Horn, G. W., Ackerman, C. J., Gardner, B. A., & Secrist, D. S. (1999). Effects of implants on daily gains of steers wintered on dormant native tallgrass prairie, subsequent performance, and carcass characteristics. Journal of Animal Science, 77(2), 291. https://doi.org/10.2527/1999.772291x

Rush I, Weichenthal B, Van Pelt B. Implants for grazing yearling steers and their effect on feedlot performance. MP-University of Nebraska, Agricultural Experiment Station (USA). 1989.

USDA. 2008. Beef 2007-08, Part I: Reference of Beef Cow-calf Management Practices in the United States, 2007-08
USDA-APHIS-VS, CEAH. Fort Collins, CO #N512-1008

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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