Effects of injectable trace minerals on reproductive performance of beef heifers in adequate trace mineral status

The Professional Animal Scientist 34:649–652 https://doi.org/10.15232/pas.2018-01752 © 2018 American Registry of Professional Animal Scientists. All rights reserved.

Effects of injectable trace minerals on reproductive performance of beef heifers in adequate trace mineral status S. A. Springman,* J. G. Maddux,† M. E. Drewnoski,‡ and R. N. Funston,*1 PAS *West Central Research and Extension Center, University of Nebraska, North Platte 69101; †Maddux Ranches, Wauneta, NE 69045; and ‡University of Nebraska, Lincoln 68583

ABSTRACT Red Angus–based, May-born heifers (n = 799) at 2 locations (Maddux Ranches, Wauneta, NE) were used to evaluate an injectable trace mineral on reproductive performance. Following October weaning, heifers were backgrounded in a feedlot until reaching a BW of 295 kg and then moved to native range at location 1 (n = 125) or location 2 (n = 286) in early March. Additional heifers (n = 388) grazed corn residue with cows, weaned in April, and were backgrounded until reaching 295 kg and then transported to locations 1 and 2 by early June. Free-choice mineral was available at both locations. Initial liver mineral status before treatment (n = 22; 307 kg) was adequate and not different (P > 0.26) among winter locations (copper = 146 μg/g, manganese = 9.22 μg/g, selenium = 1.54 μg/g, and zinc = 115 μg/g). Heifers were synchronized with a 14-d controlled internal drug-release (CIDR) timed-AI protocol and injected with a trace mineral (5 mL, Multimin 90; MM, n = 399) or not (CON, n = 400) at CIDR insertion. Bulls were with heifers on range 60 d following AI. The proportion of heifers pregnant within the first 21 d was not different (P = 0.32; 69 vs. 62 ± 3%; CON vs. MM) nor were those pregnant within 33 d (P = 0.57; 86 vs. 77 ± 2%; CON vs. MM) or overall pregnancy rates (P = 0.38; 95 vs. 93 ± 1%; CON vs. MM). Injectable trace mineral 33 d before AI did not influence reproductive performance in heifers with adequate trace mineral status. Key words: beef heifer, injectable trace mineral, reproduction

INTRODUCTION Trace minerals serve an important role in many biochemical processes such as carbohydrate, protein, and nucleic acid metabolism. As such, any change in micronu-

Received April 19, 2018. Accepted August 13, 2018. The authors declare no conflict of interest. 1 Corresponding author: rfunston2@​unl​.edu

trient levels may alter the production of reproductive and other hormones. Supplementing Cu, Mn, and Zn has been shown to reduce days to conception, reduce services per conception, and influence hormone synthesis in the ovary (DiCostanzo et al., 1986). The primary source of trace minerals for grazing cattle is forage, with water and ingested soil representing secondary sources (Arthington et al., 2014). However, these natural sources may not meet the trace mineral requirements of cattle, thereby emphasizing the need for trace mineral supplementation. Various forms of supplementation are available, including free-choice mineral, trace mineral–fortified salt blocks, drenching, oral boluses, and mineral injections (Arthington et al., 2014). Traditionally, grazing beef cattle are offered trace mineral supplementation free choice; however, intake can vary (Arthington and Swenson, 2004). Furthermore, dietary trace mineral absorption may be reduced due to negative interactions with other trace minerals during digestion. However, an injectable trace mineral (ITM) bypasses the gastrointestinal tract and dietary antagonists, making it an advantageous method by which to increase trace mineral status (Genther and Hansen, 2014). In addition, animals receive known amounts of mineral, reducing the effect of voluntary intake variability (Arthington et al., 2014). An ITM has been shown to be beneficial in some studies and not in others. Conception to fixed-time AI was greater in ITM cows when compared with saline-treated cows (Mundell et al., 2012). Conversely, a more recent study noted no differences in reproductive performance of feedlot-developed heifers given an ITM 30 d before the breeding season when adequate concentrations of trace mineral were provided in the diet (Willmore et al., 2015). Limited research has been conducted concerning the effects of an ITM administered at insertion of a controlled internal drug-release insert (CIDR) on reproductive performance of range-developed beef heifers. Heifers developed extensively represent those managed under dormant or scarce forage conditions, low precipitation, undulating terrain, or restricted gain in a pen. Therefore, the objective of the current study was to determine whether an ITM at CIDR insertion 33 d before AI affected reproductive performance of range-developed beef heifers.

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MATERIALS AND METHODS Experimental Design The University of Nebraska–Lincoln Institutional Animal Care and Use Committee approved all procedures and facilities used in this experiment. Red Angus–based, May-born heifers (n = 799) at 2 locations were used to determine whether an ITM (Multimin 90; Multimin USA, Fort Collins, CO) affected reproductive performance. Heifers were managed at the Maddux ranch, near Wauneta, Nebraska. Following October weaning, heifers (193 kg) were backgrounded in a feedlot (Table 1; 120 d, 0.78 kg/d) until reaching a BW of 295 kg. Following attainment of target BW, heifers grazed native range at location 1 (L1, n = 125) or location 2 (L2, n = 286) beginning in early March. Grazing locations (L1 and L2) were 17.7 km apart in southwest Nebraska. Additional heifers (n = 388) grazed corn residue with cows over winter, were weaned in April, and were backgrounded in a feedlot until reaching the target BW of 295 kg. They were then transported to L1 and L2 in early June. Heifers were synchronized mid-July with a 14-d CIDRprostaglandin F2α protocol (Figure 1). On d 0, heifers received a CIDR (Eazi-breed CIDR, Zoetis, Parsippany, NJ) and either were injected with a trace mineral (MM, 5 mL; n = 399) or received no injection (CON, n = 400). The injectable trace mineral dosage administered to heifers was slightly less than that recommended (1 mL/45.4 kg) and contained 15 mg/mL Cu, 10 mg/mL Mn, 5 mg/ mL Se, and 60 mg/mL Zn. Removal of CIDR occurred on d 14, and prostaglandin F2α was administered to heifers on d 30. Gonadotropin-releasing hormone was administered concurrently with fixed-time AI on d 33. Heifers randomly received AI by 6 technicians to 1 of 9 bulls. Sires were evenly distributed across breeding locations (L1 and L2) and treatment. Five days after AI, bulls were placed with heifers on range for 60 d following AI (1:17 bull-to-heifer ratio). Stocking rate during the breeding season was approximately 2.2 ha per heifer. Pregnancy diagnosis was determined via transrectal ultrasonography 61 and 91 d after AI; bulls were still with heifers at the initial ultrasound.

Table 1. Composition and nutrient analysis of diet limit fed1 to heifers in the feedlot (DM basis) Item

Value

Ingredient, % of diet   Distillers grains  Silage  Straw   Grower supplement2 Nutrient analysis   CP, %   TDN, %  NEg, Mcal/kg

47.48 35.00 11.71 5.81   19.39 78.78 1.0

Limit fed (2% BW) during backgrounding period from October to March for the first subset and April to early June for the corn residue–managed heifers. 2 Diet balanced to meet trace mineral NRC requirements: 1,372 mg/kg of zinc, 338 mg/kg of copper, 683 mg/kg of manganese, 7 mg/kg of cobalt, and 7 mg/kg of selenium. 1

Heifers were offered free-choice mineral (850 mg/kg Cu, 16 mg/kg Se, and 3,400 mg/kg Zn, Elanco, Greenfield, IN) at both locations. Initial mineral status was determined in a subset of heifers via liver biopsy before treatment (307 kg, n = 22, 13 CON, 9 MM; 15 corn residue, 7 backgrounded). Liver samples were collected in late June using the Engle and Spears (2000) method. Samples were placed in a plastic culture tube, transported on ice to the University of Nebraska–Lincoln nutrition laboratory, and frozen at −20°C. Liver samples were dried in a forced-air oven at 60°C and sent to the Diagnostic Center for Population and Animal Health (Lansing, MI) for trace mineral concentration analysis. Liver mineral concentrations were determined as described by Pogge et al. (2012) using inductively coupled plasma mass spectroscopy.

Statistical Analysis Pregnancy data were analyzed using the GLIMMIX procedure of SAS (SAS Institute Inc., Cary, NC), and trace

Figure 1. Management timeline for heifers. L1 and L2 = location 1 and location 2, respectively.

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Table 2. Initial liver mineral concentrations1 of CON and MM beef heifers2 Initial mineral, μg/g Cu Mn4 Se Zn

Adequate status3

CON (n = 13)

MM (n = 9)

SEM

P-value

125–600 >8 1.25–2.50 25–200

163 9.09 1.56 114

129 9.35 1.52 116

22 0.13 0.38 11

0.26 0.80 0.61 0.89

Concentrations are presented on a DM basis. CON = heifers received no trace mineral injection; MM = heifers were injected with 5 mL of trace mineral (Multimin 90, Multimin USA, Fort Collins, CO). 3 “Adequate” described by Kincaid (2000). 4 Adequate range status is not well established (Hansen et al., 2006). 1 2

mineral concentrations of liver were evaluated with the MIXED procedure. Least squares means and SE of the proportion of pregnant heifers by treatment were obtained using the ILINK function as pregnancy rates represent binomial distribution. Individual heifer was considered the experimental unit. Treatment and location were considered fixed effects. No interactions between treatment and location were observed. A P-value ≤0.05 was considered significant.

RESULTS AND DISCUSSION Initial liver DM concentrations of copper (146 μg/g), manganese (9.22 μg/g), selenium (1.54 μg/g), and zinc (115 μg/g) were adequate (Kincaid, 2000) and not different (P > 0.26) among heifers managed at the 2 locations (Table 2). Pregnancy rates are presented in Table 3. The proportion of heifers pregnant within the first 21 d of the breeding season was not different (P = 0.32; 69 vs. 62 ± 3%; CON, MM) nor was proportion pregnant within the first 33 d (P = 0.57; 86 vs. 77 ± 2%; CON, MM). Heifer BW at the first pregnancy diagnosis was 338 kg. Bulls remained with heifers at the initial ultrasound; therefore, a second pregnancy diagnosis was performed 30 d later. Overall pregnancy rates did not differ between treatments (P = 0.38; 95 vs. 93 ± 1%; CON, MM). Increasing amounts of essential minerals (such as Cu, Mn, Se, and Zn) are beneficial up until the requirement is met. Beyond this, additional amounts of mineral likely has little additional value and if supplemented above the maximum tolerable level, can even be toxic (NRC, 2000). In the present study, the initial concentrations of Cu, Mn, Se, and Zn in the liver of the heifers would suggest that they had adequate status of these minerals and were not deficient. Thus, it is not unexpected that the ITM did not improve reproductive performance. Previous research has indicated Cu and Se in the liver remain elevated through d 30 after injection (Pogge et al., 2012). Willmore et al. (2015) also found no effect of ITM on reproductive performance when Angus heifers were administered an ITM 30

d before the breeding season and were being fed a diet in drylot that was adequate in Cu, Mn, Se, and Zn. In addition, Stokes et al. (2018) also found no difference in primiparous AI pregnancy rate. In other work, Stokes et al. (2017) noted increased AI pregnancy rates in Simmental × Angus heifers administered an ITM 30 d before breeding. One of the first studies to report a benefit of ITM on reproduction was a study conducted in Brazil with timed embryo transfer where an increase in heifer conception rate was noted (Sales et al., 2011). In this study they did not measure concentrations of the supplemented trace minerals (Cu, Mn, Se, or Zn) in the liver or blood. Heifers were grazing grass pastures (Brachiaria brizantha) and received free-choice access to mineral salts containing these trace minerals. However, the stated expected daily intake of the mineral salt would have supplied 64, 17, 60, and 86% of the heifers’ Cu, Mn, Zn, and Se requirements in the winter, respectively. Although the forage would have made up some of the difference in trace mineral intake, low quality forage tends to be relatively low in trace mineral content, and thus, a deficiency in one of these minerals cannot

Table 3. Effect of an injectable trace mineral administered 33 d before breeding on pregnancy rate in beef heifers with adequate trace mineral status1 Pregnancy rate,2 % First 21 d First 33 d Overall

CON MM (n = 400) (n = 399) SEM P-value 63 86 95

69 77 93

3 2 1

0.32 0.57 0.38

CON = heifers received no trace mineral injection; MM = heifers were injected with 5 mL of trace mineral (Multimin 90, Multimin USA, Fort Collins, CO). 2 Pregancy rates were determined via transrectal ultrasonography. 1

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be ruled out. Samples of Brachiaria brizantha taken during the growing season in a different study in Brazil showed that it contained only 6.3 mg/kg Cu (Rueda et al., 2003), and Cu concentrations would be expected to decline as the forage matures. Mundell et al. (2012) administered an ITM (Multimin) 105 d before projected calving date and 30 d before fixedtime AI to cows that were grazing native pastures in Kansas with access to free-choice trace minerals. The authors suggested that based on the SD of serum concentrations of Cu, Se, and Zn at the initiation of the study, a notable portion of the cows may have been marginal to slightly deficient in these minerals, potentially explaining the conception rates to AI being greater for ITM cows (60%) than for CON cows (51%). However, in dairy cows, Vanegas et al. (2004) reported no beneficial effects of a single dose of an ITM (Multimin) before breeding on first-service conception rates. However, decreased first-service conception rates were observed in dairy cows receiving 2 doses of ITM: one before calving and one before breeding. There have been, however, positive results reported from ITM including increased mineral status (Pogge et al., 2012), increased feed efficiency (Clark et al., 2006), reduced treatments for illness (Berry et al., 2000), and reduced morbidity treatment costs (Richeson and Kegley, 2011) in stressed feeder calves.

2006. Effects of respiratory disease risk and a bolus injection of trace minerals at receiving on growing and finishing performance by beef steers. Prof. Anim. Sci. 22:1–7.

IMPLICATIONS

Richeson, J. T., and E. B. Kegley. 2011. Effect of supplemental trace minerals from injection on health and performance of highly stressed, newly received beef heifers. Prof. Anim. Sci. 27:461–466.

Our findings indicate an ITM administered at CIDR insertion did not influence reproductive performance in heifers with adequate trace mineral status. Our study in combination with the available peer-reviewed literature suggests that there may be no benefit to using an ITM before breeding if cattle have adequate status, but when using an ITM to correct a deficiency before breeding, an improved conception rate may be observed.

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Rueda, B. L., R. W. Blake, C. F. Nicholson, D. G. Fox, L. O. Tedeschi, A. N. Pell, E. C. M. Fernandes, J. F. Valentim, and J. C. Carneiro. 2003. Production and economic potentials of cattle in pasturebased systems of the western Amazon region of Brazil. J. Anim. Sci. 81:2923–2937. Sales, J. N. S., R. V. V. Pereira, R. C. Bicalho, and P. S. Baruselli. 2011. Effect of injectable copper, selenium, zinc and manganese on the pregnancy rate of crossbred heifers (Bos indicus × Bos taurus) synchronized for timed embryo transfer. Livest. Sci. 142:59–62. Stokes, R. S., A. R. Ralph, A. J. Mickna, W. P. Chapple, A. R. Schroeder, F. A. Ireland, and D. W. Shike. 2017. Effect of an injectable trace mineral at the initiation of a 14 day CIDR protocol on heifer performance and reproduction. Transl. Anim. Sci. 1:458–466. Stokes, R. S., M. J. Volk, F. A. Ireland, P. J. Gunn, and D. W. Shike. 2018. Effect of repeated trace mineral injections on beef heifer development and reproductive performance. J. Anim. Sci. (Accepted). Vanegas, J. A., J. Reynolds, and E. R. Atwill. 2004. Effects of an injectable trace mineral supplement on first-service conception rate of dairy cows. J. Dairy Sci. 87:3665–3671. Willmore, C. J., J. B. Hall, S. Harrison, and M. E. Drewnoski. 2015. Effect of a trace mineral injection on pregnancy rate of Angus beef heifers when synchronized using the 14-day controlled internal drugreleasing insert–prostaglandin F2α protocol at a commercial feedlot. Prof. Anim. Sci. 31:588–592.