|Abstract:||Minerals play numerous roles in the ruminant animal’s body and are included as components of bone, tissues, body fluids, enzymes, and hormones. Grazing cattle primarily receive trace minerals through forages; however, these sources often do not meet the trace mineral requirements of cattle due to variation in soil composition. In these instances, producers commonly supplement trace minerals through free-choice mineral and salt blocks or protein/energy supplements fortified with trace minerals to ensure optimal cattle performance and health. The interactions that trace minerals can have on animal production are complex and multiple factors can impact an animal’s response to mineral supplementation. The objective of this dissertation was to evaluate alternative trace mineral supplementation strategies and the effects these minerals may have on heifer development, reproductive success, fetal growth, and long term productivity of beef cattle.
Recently data have suggested that organic or chelated trace minerals may improve growth, reproduction, and health traits in ruminants. To evaluate the effect of supplementing two different chelated trace mineral sources on reproductive performance of beef cows, 204 spring-calving, Angus and Simmental × Angus cows [body weight (BW) = 649 ± 129 kg] were utilized. Cows received 1 of 2 glycine ligand chelated trace minerals, both formulated to replace 50% of the Cu, Mn, and Zn inorganic trace mineral (MAAC; MAAC, Novus International; TRAX; B-Traxim 2C, Pancosma). Liver mineral concentrations were not different (P ≥ 0.11) regardless of treatment. Liver metallothionein (MT)/actin expression was not different (P ≥ 0.24) at trial initiation or at breeding. Interestingly, TRAX cattle did have greater (P = 0.03) MT/actin expression comparted to MAAC cattle at the time of final pregnancy confirmation. There was no effect (P = 0.91) of supplementation on artificial insemination (AI) conception rate (MAAC=72.2% and TRAX=71.2%). Interestingly, overall pregnancy rate was greater (P = 0.03) for TRAX (98.4%) compared to their MAAC (90.1%) counterparts. Supplementing beef cows with B-Traxim 2C prior to breeding improved overall pregnancy rates but did not alter BW or trace mineral status.
Injectable trace minerals offer another unique way to supplement trace minerals. Three experiments were conducted at separate locations to determine the effects of a trace mineral injection (TMI), Multimin 90, on heifer performance and reproduction. In Exp. 1, (spring-born, Angus, n = 93, BW = 428 ± 45.2 kg), Exp. 2 (spring-born, Angus × Simmental, n = 120, BW = 426 ± 54.0 kg), and Exp. 3 (fall-born, commercial Angus, n = 199, BW = 345 ± 39.7 kg) heifers were assigned to 1 of 2 treatments: a control, saline injection, or TMI at a dose of 1 mL/68 kg BW. Injections were given 33 d prior to breeding at the initiation of a 14-d controlled internal drug release (CIDR)-prostaglandin protocol. In Exp.1 pregnancy rates to timed AI and overall pregnancy rates were similar (P ≥ 0.74) regardless of treatment. During Exp. 2, there was a tendency (P = 0.07) for TMI heifers to have an increased AI pregnancy rate (62% vs. 45%) compared with control heifers despite no difference (P = 0.51) in overall pregnancy rate. In Exp. 3, there were no differences (P ≥ 0.50) in AI and overall pregnancy rates.
An additional experiment was conducted to determine the effects of repeated TMI on heifer development and reproductive performance. Commercial Angus heifers (n = 290; 199 ± 34.3 kg; 221 ± 22 d of age) were administered an injectable trace mineral (MM; Multimin90) or saline (CON) given subcutaneously, post-weaning at 221, 319, 401, and 521 ± 22 d of age. Plasma Mn and Zn concentrations did not differ (P ≥ 0.54). However, MM heifers had greater (P ≤ 0.01) plasma and liver concentrations of Cu and Se compared to CON. Interestingly, MM decreased (P = 0.02) liver Zn concentrations compared to CON, and there was no difference (P = 0.60) in liver Mn. Antral follicle count and ovarian size did not differ (P ≥ 0.51) due to treatment. Throughout development, number of heifers cycling was lesser (P < 0.01) for MM than CON heifers. However, there was no difference (P ≥ 0.19) in reproductive tract scores (RTS), AI pregnancy rates, or overall pregnancy rates. Commercial Angus heifers (n = 190; 315 ± 49.3 kg) from the previous experiment, that were confirmed pregnant, were utilized to determine the effects of trace mineral injections during gestation on heifer and subsequent calf performance. Treatments were maintained and subsequent injections were given 205, 114, and 44±26 d prepartum. Data were reported from 174 calves (n = 87 calves/treatment). Multimin heifers tended (P = 0.08) to have greater initial liver Se and tended to have decreased (P = 0.08) initial liver Zn compared to CON. At calving, MM cows had increased (P ≤ 0 .01) liver Cu and Se. There was no difference (P ≥ 0.47) in Julian calving date, calving percent or unassisted births. Calf birth BW was lesser (P = 0.02) for MM than CON calves and MM calves had greater (P = 0.03) liver Cu concentrations at birth compared to CON. Despite MM cows having increased (P < 0.01) milk production, calf weaning BW and average daily gain (ADG) were not different (P ≥ 0.87). Additionally, calf morbidity and mortality were not different (P ≥ 0.43) between treatments. Calf mineral status was not different (P ≥ 0.57) at the time of weaning regardless of treatment; however, MM cows had decreased (P = 0.03) liver Zn. Multimin cows had decreased (P = 0.05) AI pregnancy rates, yet, there was no difference (P = 0.34) in overall pregnancy rate.
Twenty-four commercial Angus steers (BW = 204 ± 19 kg; 12 MM steers and 12 CON) from the previous experiment, were utilized to determine the effects of maternal supplementation with an injectable trace mineral on the inflammatory response of calves subjected to a lipopolysaccharide (LPS) challenge at the initiation of a 42 d receiving period. Initial plasma Zn tended (P = 0.06) to be greater for MM steers. However, there was no difference (P ≥ 0.31) in trace mineral status or serum cortisol at any other time. Total area under the curve (TAUC) for body temperature was lesser (P > 0.01) for MM steers. Basal LPS binding protein (LBP) concentrations and TAUC for LBP tended (P ≤ 0.10) to be greater for MM steers. Peak concentration of interleukin-1β (IL-1β) tended (P = 0.09) to be reached earlier for CON steers. However, there was no difference (P ≥ 0.15) in glucose, insulin, and interleukin-6 (IL-6), concentrations regardless of treatment. Additionally, calf performance and feed efficiency were not different (P ≥ 0.17) between treatments except ADG from d 28 – 42, which was greater (P = 0.03) for CON steers.
In summary, additional injectable trace mineral supplementation in developing beef heifers resulted in varied reproductive responses even when provided adequate trace mineral. Supplementing an injectable trace mineral during heifer development and gestation did result in increased cow milk production. However, there was no effect on overall cow pregnancy rates or pre-weaning calf health or performance. Additionally, maternal supplementation resulted in altered body temperature and LBP production in subsequent calves when exposed to an inflammatory challenge. Due to the difficulty of assessing trace mineral status of an entire herd, supplementing trace minerals through an injection may be a viable way to ensure a consistent, adequate trace mineral supply to heifers for optimal development, reproductive success, and subsequent offspring performance. While mineral status and reproductive responses across these experiments were variable, it is important to note that injectable trace minerals do not appear to incur any negative impacts on beef heifer reproductive success or subsequent calf performance.