Effects of Surgical Spaying on Heifer Feedlot Growth Performance and Dietary Energetics

Iranian Journal of Applied Animal Science

دوره 13، شماره 2، شهریور 2023، صفحه 383-387   

نوع مقاله: Short Communications

نویسندگان

A. Plascencia^{* 1}؛ V.M. González-Vizcarra²؛ Y.S. Valdés-García²؛ A. Barreras²؛ A. Estrada-Angulo¹؛ J.D. Urías-Estrada¹؛ R.A. Zinn³

¹Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Sinaloa, Culiacán 80260, Sinaloa, México

²Instituto de Investigaciones en Ciencias Veterinarias, Universidad Autónoma de Baja California, Mexicali, Baja California, México

³Department of Animal Science, University of California, Davis, USA

چکیده

Fifty crossbred heifer calves were used in randomized complete block design experiment (5 heifers/pen and 5 replications per treatment), to compare effects on surgical spaying (SPAY) versus non-spayed intact (INTC) on growth-performance and dietary energetic efficiency during a 175-d growing finishing period. Upon initiation of the study heifers were implanted with a medium potency anabolic implant (200 mg testosterone propionate and 20 mg estradiol benzoate) and were reimplanted at day 75 (100 days previously to finishing experiment) with a high potency anabolic implant (140 mg trenbolone acetate and 14 mg estradiol. During first 35 days, spaying tended (P=0.08) to depress average daily gain (ADG, 9.9%) and dry matter intake (DMI, 7.5%). Differences in ADG were consistent with treatment effects on DMI, as observed DMI for both treatments were in good agreement with expected based on the net energy (NE) value of the diet. The cumulative ADG during the first 70 days and overall, were lower (7.0% and 4.6%, respectively; P≤0.04) for SPAY vs. INTC heifers. Due numerically greater DMI for INTC heifers, gain efficiency and observed vs. expected dietary NE were similar (P>0.27) across treatments. Surgical spaying retard has an appreciable long-term negative effect on daily weight gain of otherwise implanted feedlot heifers.

کلیدواژه‌ها

anabolic؛ cattle؛ feed efficiency؛ ovariectomy؛ re-implanting؛ spayed vs. intact

اصل مقاله

INTRODUCTION

Advantages of heifer spaying include both a reduction in physical activity and reduced risk of injury due to absence of “heat” cycles. These potential benefits might be reflected in enhancements in feedlot growth efficiency (Smith-Thomas, 2013; Ko et al. 2022). However, Rupp and Hamilton (2000), in a 33 trial summary observed that spaying of non-implanted heifers depressed ADG (6.5%) when comparison with intact heifers. However, ADG of implanted spayed heifers tended to be numerically greater (1.5%) than that of intact implanted heifers (Rupp and Hamilton, 2000). Likewise, Dinusson and Haugse (1983) observed the restorative effect of implanting spayed heifers. Ovariectomized heifers exhibited a four-fold greater response in ADG due to application of growth implants than intact heifers (Garber et al. 1990). Therefore, the removal of ovaries can enhance the response of heifers to anabolic implantation. Nevertheless, augmentations due to implanting may not be sufficient to overcome risks and costs associated with spaying (Kelzer, 2009; AVMA, 2011). It is customary with longer term feedlot growing-finishing periods (i.e., >140 d), heifers would be reimplant at least once. To our knowledge, there is no information available evaluating feedlot growth performance response of reimplanted spayed feedlot heifers. For this reason, an experiment was conducted to evaluate the effects of surgical spaying on feedlot growth performance and efficiency of dietary net energy of heifers receiving two anabolic implants during the course of the growing-finishing period.

 

MATERIALS AND METHODS

All procedures involving animal care and management were in accordance with and approved by the University of California, Davis, Animal Use and Care Committee (Protocol #22271). Sixty crossbreed heifers (approximately 25% Brahman breeding with the remainder represented by Hereford, Angus, Shorthorn, and Charolais breeds in various proportions) with an average initial weight of 253.06 ± 22.8 kg were received at the research facility 4 weeks before the start of the trial. Upon arrival, heifers were vaccinated against bovine rhinotracheitis-parainfluenza (Cattle Master Gold FP 5 L5, Zoetis, New York, NY), clostridials (Ultrabac-7, Zoetis, New York, NY), treated against internal and external parasites (Dectomax Injectable, Zoetis, New York, NY), subcutaneously injected with 1500 IU vitamin E (as d-alpha-tocopherol) 500000 IU vitamin A (as retinyl-palmitate) and 50000 IU vitamin D3 (Vital E-A+D3, Stuart Products, Bedford, TX), and 2.4 g oxytetracycline (LA-200, Zoetis, New York, NY), branded, and ear-tagged. All heifers were subject to rectal palpation in order to determine absence of pregnancy and normality of uterus and ovaries. Subsequently, 50 heifers were selected from the original group for inclusion in the experiment. Heifers were blocked by weight (5 blocks) and assigned within blocks to 10 pens (5 heifers/pen, 5 pen replications per treatment). Half of the heifers were spayed (bilateral ovariectomy, via an incision through the left paralumbar fossa, with complete removal of the ovaries using an ovariotome emasculator). All surgeries were performed under local anesthesia (10 mL of lidocaine-HCL, 2%) of and were performed by a certified large-animal-veterinarian. In order to ensure 0% pregnancy rate in intact heifers group, heifers were injected intramuscularly with 25 mg dinoprost (Lutalyse, Zoetis, Kalamazoo, MI). Pens were 50 m² with 33 m² overhead shade, automatic waters, and 4.3 m fence-line feed bunks. Heifers were fed with a steam-flaked corn-based diet formulated to meet requirements for growing-finishing feedlot beef heifers (NRC, 2016), same as it contained 11.8% crude protein and 2.23 Mcal of net energy for maintenance (NE_m)/kg. Ingredient composition of the finishing diet was as follows (dry matter; DM basis): Alfalfa hay, 3.83%; sudan grass hay, 7.67%, steam flaked corn, 75.92, yellow grease, 2.64%, cane molasses, 7.04% limestone, 1.31%, urea, 0.97%, magnesium oxide, 0.18%, and trace mineral salt, 0.44%. Heifers were allowed ad libitum access to the diet. Fresh feed was provided twice daily at 08:00 and 14:00. Feed delivery was adjusted so that daily feed refusals did not exceed 5% prior to the morning feeding. Feed samples were collected from each elaborated batch. Daily feed refusal composited weekly for DM analysis (oven drying at 105 ˚C until no further weight loss; method 930.15, AOAC, 2000). Upon initiation of the experiment, heifers were implanted with 200 mg testosterone propionate/20 mg estradiol benzoate (Synovex H, Zoetis, Kalamazoo, MI), and on day 70, heifers were reimplanted with 200 mg trenbolone acetate/14 mg estradiol benzoate (Revalor-H, Merck Animal Health, Madison, NJ). All heifers were weighed before the morning meal at initiation of the experiment, and on days 35, 70, and 175. For the growth performance and dietary energy calculations, full live weights were multiplied by 0.96 to obtain estimated initial and final shrunk body weight (SBW). Average daily gain (ADG) was determined as the difference in initial SBW and carcass adjusted final SBW divided by 175 (days on test). Gain efficiency (G:F) was determined as the ADG divided by corresponding dry matter intake (DMI). One approach for evaluation of the efficiency of dietary energy utilization in growth-performance trials is the observed-to-expected dietary NE ratio and the observed-to-expected DMI ratio. Based on measures of growth performance (observed DMI, ADG, and average SBW), the observed dietary net energy was calculated for each treatment by means of the quadratic formula according to the procedure from Zinn et al. (2008) as follows:

x= (-b-√ b2–4ac) / 2c

Where:

x: observed dietary NE_m (Mcal/kg).

a: -0.41 EM

b: 0.877 EM + 0.41 DMI + EG.

c: -0.877 DMI.

EM= energy required for maintenance (NE_m, Mcal/d), and EG= energy required for gain (NE_g, Mcal/d), were estimated using following equations: EM= 0.077 × SBW^0.75 and EG= 0.0618 × (SBW×0.91)^0.75 × ADG^0.905, and DMI correspond to the average daily DMI (kg) registered during the experiment (Zinn et al. 2008).

Treatments were randomly assigned to pens within each block in a general complete block design. Response variables were analyzed with a linear model which includes μ as constant, τi and θj as fixed effects of treatment and block, and εijk as associated random error. Response variables Yijk are mutually independent and have a normal distribution with mean μ + τi and variance σ2. Pen was the experimental unit and initial weight the criterion of blocking. The analysis was carried out using the MIXED procedure of SAS software (SAS, 2007). Least squares means were compared using Tukey test. Significant differences among treatments were declared at P ≤ 0.05 and tendencies were declared at 0.05 < P ≤ 0.10.

 

RESULTS AND DISCUSSION

No morbidity or mortality was observed. Treatment effects on growth performance are shown in Table 1. During first 35days, spaying tended (P=0.08) to depress ADG (9.9%) and DMI (7.5%). Differences in ADG were consistent with treatment effects on DMI, as observed DMI for both treatments were in good agreement with expected based on the NE value of the diet (Table 2). The cumulative ADG during the first 70 days and overall, were lower (7.0% and 4.6%, respectively; P≤0.04) for SPAY vs. INTC heifers. Due numerically greater DMI for INTC heifers, gain efficiency and observed vs. expected dietary NE were similar (P>0.27) across treatments. These results are in agreement with the results reported by Hamernik et al. (1985) and Bailey et al. (2008), but not with findings of Garber et al. (1990) and Perino et al. (1995). Inconsistencies between reports have been attributed to differences in initial weight, diet energy density, and anabolic implants (Adams et al. 1990; Garber et al. 1990). However, Plascencia et al. (2008), comparing a group of ovariectomized heifers fed a 1.72 Mcal NE_m/kg diet during the first 70 days followed by a 2.16 Mcal NE_m/kg of diet for the remaining 28 days vs. a group that were fed a 2.16 Mcal NE_m/kg diet throughout the 98 d trial, observed feeding management did not affect gain efficiency and efficiency of dietary energy utilization. Thus, it seems apparent that anabolic implants would be the more important supportive factor influencing growth efficiency of spayed heifers (Garber et al. 1990; Popp et al. 1997). In one study (Garber et al. 1990), ovariectomized heifers exhibited a four-fold greater ADG response to an anabolic implant than intact heifers. Compared to intact heifers Plascencia et al. (2008) observed that spayed heifers (implanted once with medium potency implant) greater gain efficiency and efficiency of dietary energy utilization during a 98-d fattening.

 

Table 1 Effect of surgical spaying on long-term fattening on dietary energy of feedlot heifers receiving two implants during fattening

 

SEM: standard error of the means.

 

Table 2 Effect of surgical spaying on long-term fattening on dietary energy of feedlot heifers receiving two implants during fattening

 

SEM: standard error of the means.

 

Brownson (1994) observed that spayed heifers implanted (single implant) with a low-or- moderate potency anabolic implant had similar ADG to that of intact heifers. In contrast, Bailey et al. (2008), in a 42-d feedlot evaluation, report a tendency for lower ADG in spayed heifers compared to intact heifers (both implanted with a medium potency anabolic implant). Unfortunately, there has been relatively little research comparing implant programs in spayed heifers. Garber et al. (1990), reported that spayed heifers receiving an implant of estradiol/progesterone (Synovex S) gained significantly better (P<0.05) than heifers receiving an implant of estradiol/testosterone (Synovex H) during a finishing period. Additionally, Perino et al. (1995) observed that spayed heifers receiving estradiol or estradiol + trenbolone acetate, but not trenbolone acetate alone, had greater ADG (P<0.05) than non-implanted, spayed heifers. There is no recent information about the effect of spaying on performance of feedlot heifers under current implantation systems in which more than one implant is used during fattening. Our hypothesis was that in long-fed heifers, the magnitude of response to spaying heifers might be compensated when receive two anabolic implants, in which one implant is a high potency implant. However, in the present study the implanting was not sufficient to compensate for overall effects of spaying on ADG. A possible explanation is the suppression of estrus associated hormonal changes due anabolic implant containing trenbolone (Preston, 1999).

 

CONCLUSION

Surgically spaying heifers upon entry to the feedlot retards the rate of gain, notwithstanding application of anabolic implants during a longer-term growing finishing period. Taking in account the difference in final weight and rate of gain in SPAY heifers compared to intact heifers, spayed heifers needed 7.5 more days to achieve a final weight similar to that of intact heifers.

 

ACKNOWLEDGEMENT

The authors thank all the teams who worked on the experiments and provided results during this study.

مراجع

Adams T.E., Dunbar J.R., Berry S.L., Garret W.N., Famula T.R. and Lee Y.B. (1990). Feedlot performance of beef heifers implanted with Sinovex-H: Effect of melengestrol acetate, ovariectomy or active inmunization against GnRH. J. Anim. Sci. 68, 3079-3085.

AOAC. (2000). Official Methods of Analysis. 17^th Ed. Association of Official Analytical Chemists, Arlington, Washington, DC., USA.

AVMA. (2011). Literature Review on the Welfare Implications of Ovariectomy in Cattle. American Veterinary Medical Association. WebMD. https://www.avma.org/resources-tools/literature-reviews/welfare-implications-ovariectomy-cattle.

Bailey C.R., Duff G.C., Sanders S.R., Cuneo S.P., McMurphy C.P., Limesand S.W., Marchello J.A., Schafer D.W., Rhoads M.L. and Hallford D.M. (2008). Effects of ovariectomy and anabolic steroid implantation on the somatotrophic axis in feedlot heifers. South African J. Anim. Sci. 38, 207-216.

Brownson R. (1994). Spaying Heifers. Beef Cattle Handbook-BCH-7390. Iowa Beef Center. Available at: https://www.iowabeefcenter.org/bch/SpayingHeifers.pdf.

Dinusson W.E. and Haugse C.N. (1983). The effect of spaying, aborting and implants on the performance of beef heifers-A review. North Dakota State University Farm. Available at: https://library.ndsu.edu/ir/bitstream/handle/10365/10190/farm_41_02_12.pdf.

Garber M.J., Roeder R.A., Combs J.J., Eldridge L., Miller J.C., Hinman D.D. and Ney J.J. (1990). Efficacy of vaginal spaying and anabolic implants in growth and carcass characteristics in beef heifers. J. Anim. Sci. 68, 1469-1475.

Hamernik D.L., Males J.R., Gaskins C.T. and Reeves J. (1985). Feedlot performance of hysterectomized and ovariectomized heifers. J. Anim. Sci. 60, 358-362.

Kelzer J. (2009). Spaying Heifers: What Is It Worth? The Beef Site. WebMD. https://www.thebeefsite.com/articles/2213/spaying-heifers-what-is-it-worth.

Ko B.H., Park D.G. and Lee W.J. (2022). Postoperative observation of spaying with the silicon ring on the ovaries in heifers: A retrospective study in 28 cases. Vet. Sci. 9, 643-652.

NRC. (2016). Nutrient Requirements of Beef Cattle. 8^th Ed. National Academy Press, Washington, DC., USA.

Perino L.J., Rupp G.P., Hollis L.C., Schanbacher B.D. and Cundiff L.V. (1995). Growth and carcass characteristics of heifers implanted with estradiol benzoate and trenbolone acetate. The compendium on continuing education for the practicing veterinarian, USA. 

Plascencia A., Valenzuela R.M., Barreras A., Cervantes M., González V.M. and Zinn R.A. (2008). Influence of ovariectomized (spaying) and feeding system on performance and carcass characteristics of implanted beef heifers. J. Anim. Vet. Adv. 7, 365-369.

Popp J.D., McAllister T.A., Burgevitz W.J., Kemp R.A., Kastelic J.P. and Cheng K.J. (1997). Effect of trenbolene acetate/estradiol implants and estrus suppression on growth performance and carcass characteristics of beef heifers. Canadian J. Anim. Sci. 77, 325-328.

Preston R.L. (1999). Hormone containing growth promoting implants in farmed livestock. Adv. Drug Delivery Rev. 38, 123-138.

Rupp G.P. and Hamilton E.D. (2000). Management of spayed heifers. American Assoc. Bovine Pract. Conf. Proc. 33, 112-116.

SAS Institute. (2007). SAS^®/STAT Software, Release 9.3. SAS Institute, Inc., Cary, NC. USA.

Smith Thomas H. (2013). Why spaying beef heifers makers sense. Beef Magazine, 7900 International Drive, Suite 650, Minneapolis, MN 55425 USA. Available at: http://beefmagazine.com/cattlegenetics/why-spaying-beef-heifers-makes-sense?page=1.

Zinn R.A., Barreras A., Owens F.N. and Plascencia A. (2008). Performance by feedlot steers and heifers: ADG, mature weight, DMI and dietary energetics. J. Anim. Sci. 86, 1-10.