Extended-release Eprinomectin Research Articles

Evaluation of postweaning performance and reproductive measurements in fall-born replacement beef heifers treated with different anthelmintic regimens

The United States cattle industry suffers substantial monetary losses due to gastrointestinal parasites. There are limited data on extended-release and pour-on anthelmintic treatment on growth and reproductive performance in replacement beef cattle. This study aimed to investigate anthelmintic therapy on postweaning growth performance and reproductive success in fall-born, crossbred replacement heifers. Eighty-three, newly weaned, Angus crossbred, fall-born heifer calves were stratified by BW at d −14, fecal egg count, and day of age and allocated randomly to 1 of 3 anthelmintic treatments: (1) control, no anthelmintic (n = 28; CON); (2) combination pour-on moxidectin and oxfendazole (n = 28; MO); or (3) extended-release eprinomectin (n = 27; ERE). Heifers grazed within treatment groups on separate pastures for a 274-d period. Respective anthelmintics were administered on d 0 and 154. Body weights, BCS, and calf BW were analyzed using the MIXED procedure of SAS. Heifer cyclicity, estrous detection (using an Estrotect patch), AI conception, natural service conception, overall pregnancy rates, and live calving rates were analyzed using the GENMOD procedure of SAS. Significance was declared at P ≤ 0.05. Final heifer BW, ADG and BCS were greater ( P < 0.01) in ERE groups compared with MO and CON heifers. Heifer cyclicity and estrous detection rates were greater ( P < 0.01) in MO and ERE compared with CON. Overall pregnancy rates were greater in ERE compared with CON ( P < 0.01). The inclusion of an anthelmintic increased growth and improved reproductive performance in fall-born heifers over a 274-d grazing study.

PSI-2 Effects of extended release eprinomectin on heifer performance while grazed on endophyte-infected tall fescue or housed in drylot

Abstract Objectives were to evaluate the effects of LongRange, an extended-release eprinomectin, on beef heifer performance while grazed on endophyte-infected tall fescue or housed in drylot. Fall-born, Angus × Simmental heifers (n = 153) were utilized in a split-plot design. Heifers were stratified by BW and assigned to 6 groups. Groups were randomly assigned to 1 of 2 environmental treatments: grazed endophyte-infected tall fescue (Pasture) or housed in drylot and fed alfalfa hay. Within environmental treatment groups, heifers were randomly assigned to LongRange (LR) or control (Saline). Prior to experiment initiation, heifers were treated with oral fenbendazole (SafeGuard) to minimize parasite load. Data were analyzed using the MIXED procedure of SAS. At d 0, 56, and 112, heifer BW, ADG, BCS, hair coat score (HCS), and fecal egg counts (FEC) were collected. Treatments did not affect (P ≥ 0.17) BW on d 0 and 56. On d 112, drylot heifers tended (P = 0.08) to be heavier than pasture heifers and LR increased (P = 0.01) BW. There was an interaction (P = 0.02) for ADG; LR increased ADG to a greater magnitude in pasture than drylot heifers. On d 0, 56, and 112, there was no interaction or LongRange effect (P ≥ 0.11) on BCS; however, pasture heifers had greater (P = 0.05) d 112 BCS than drylot heifers. On d 56, there was an interaction (P = 0.01) on HCS; LR decreased HCS in pasture heifers, but did not affect HCS in drylot heifers. Although treatment did not effect (P ≤ 0.33) FEC at d 0, there was an interaction (P = 0.01) observed on d 56. LongRange decreased FEC in pasture heifers but not in drylot. In conclusion, LongRange increased heifer growth performance with a greater difference for heifers grazing tall fescue, compared with heifers in drylot.

PSIV-26 Effects of extended-release eprinomectin on heifer growth and reproductive performance while grazed on endophyte-infected tall fescue or housed in drylot

Abstract The objective was to assess the effects of an extended-release eprinomectin (LongRange) on beef heifer reproductive performance when grazed on endophyte-infected tall fescue or housed on drylot. In a split-plot design, fall-born, Angus × Simmental heifers (n = 153) were stratified by BW and divided into 6 groups. Groups were randomly assigned environmental treatments: grazed endophyte-infected tall fescue (pasture) or maintained in drylot and fed alfalfa hay. Within a group, heifers were randomly assigned to LongRange (LR) or saline (control). Heifers were dewormed with oral fenbendazole (SafeGuard) to minimize parasite load before trial initiation. On d 140 and final pregnancy check, body weight (BW) and body condition score (BCS) were collected; BW was also collected at time of artificial insemination (AI). Hair coat score (HCS), fecal egg count (FEC), packed cell volume (PCV), and respiration rates (RR) were collected on d 140. Data were analyzed using the MIXED procedure of SAS. Environment × treatment effects for BW were detected (P ≤ 0.01) at d 140 and at overall pregnancy confirmation; LR increased BW to a greater magnitude in pasture than in drylot heifers. At breeding, LR increased (P = 0.01) heifer BW compared to control. On d 140, LR increased (P = 0.01) heifer BCS compared to control. On d 140, pasture heifers tended (P = 0.08) to have greater RR than drylot heifers. Heifer AI pregnancy rates were not affected (P ≥ 0.21) by treatments. Environment × treatment effects for overall pregnancy were detected (P = 0.03); LR increased overall pregnancy rate in pasture compared to drylot heifers and LR tended to increase overall pregnancy rate compared with control in pasture heifers. In conclusion, LongRange increased BW to a greater extent in pasture than in drylot and tended to increase heifer final pregnancy rate compared to control on pasture.

79 Evaluation of extended release eprinomectin efficacy on multiparous beef cow performance

Abstract Internal parasitism inevitability prompts economic loss in beef cattle production by decreasing growth performance and reproductive traits. Previous studies have conflicting results on the macrocyclic lactones (ML) efficacy against internal parasitism. The objective of this study was to evaluate the efficacy of milbeymycin and avermectin sub groups of ML on cow performance. Multiparous fall calving, crossbred beef cows (n = 106) were allocated randomly to 1 of 3 anthelmintic treatments: 1) Negative control (CON), in which cows did not receive an anthelmintic, 2) Injectable moxidectin (MOX) and 3) Injectable extended release eprinomectin (ERE). Body weights (BW), body condition scores (BCS), and fecal egg counts (FEC) were taken throughout the duration of the calving season to weaning on d0, d80, d162, and d217, with weaning occurring on d217. Performance data were analyzed using the MIXED procedures of SAS, and pregnancy data were analyzed using the GENMOD procedures of SAS. Significance was fixed at P &amp;lt; 0.05 and tendencies were established from 0.05 ≤ P ≤ 0.10. There was no effect of anthelmintic treatment on cow BW (P ≥ 0.57) or cow BCS (P ≥ 0.22) during the 217 d study; however, CON cows tended to have lower BCS (P = 0.08) throughout the duration of the study. Cows treated with ERE had fewer FEC compared to MOX and CON groups (P ≤ 0.001), and tended to improve pregnancy rates (c2 = 0.0546). Calf weaning weight was similar among treatments averaging 216, 225, and 223 kg regarding CON, MOX, and ERE cow treatments, respectively.

80 Evaluation of extended release eprinomectin efficacy on multiparous beef cow performance

Abstract Internal parasitism inevitability prompts economic loss in beef cattle production by decreasing growth performance and reproductive traits. Previous studies have conflicting results on the macrocyclic lactones (ML) efficacy against internal parasitism. The objective of this study was to evaluate the efficacy of milbeymycin and avermectin sub groups of ML on cow performance. Multiparous fall calving, crossbred beef cows (n = 106) were allocated randomly to 1 of 3 anthelmintic treatments: 1) Negative control (CON), in which cows did not receive an anthelmintic, 2) Injectable moxidectin (MOX) and 3) Injectable extended release eprinomectin (ERE). Body weights (BW), body condition scores (BCS), and fecal egg counts (FEC) were taken throughout the duration of the calving season to weaning on d0, d80, d162, and d217, with weaning occurring on d217. Performance data were analyzed using the MIXED procedures of SAS, and pregnancy data were analyzed using the GENMOD procedures of SAS. Significance was fixed at P &amp;lt; 0.05 and tendencies were established from 0.05 ≤ P ≤ 0.10. There was no effect of anthelmintic treatment on cow BW (P ≥ 0.57) or cow BCS (P ≥ 0.22) during the 217 d study; however, CON cows tended to have lower BCS (P = 0.08) throughout the duration of the study. Cows treated with ERE had fewer FEC compared to MOX and CON groups (P ≤ 0.001) and tended to improve pregnancy rates (c2 = 0.0546). Calf weaning weight was similar among treatments averaging 216, 225, and 223 kg regarding CON, MOX, and ERE cow treatments, respectively.

Reduced gastrointestinal worm burden following long term parasite control improves body condition and fertility in beef cows

The objective of this study was to compare effects of gastrointestinal parasite control over a long vs short term (PC-LT vs. PC-ST) on fecal parasite load, body condition and pregnancy in beef cows. On Day 0, fecal samples were collected from Angus cross cows (n = 1462) and they were assigned a body condition score (BCS: 1, emaciated; 9, Obese) and randomly divided into two groups (within location) to receive extended-release eprinomectin [PC-LT; n = 749; 50 mg/50 kg body weight (BW)] or pour-on ivermectin (PC-ST; n = 713; 25 mg/50 kg BW). All cows were synchronized with CO-Synch + CIDR [100 μg GnRH + progesterone vaginal insert (CIDR) application on Day 20, CIDR removal +25 mg PGF2a on Day 27, and artificial insemination +100 μg GnRH on Day 30 (66 h after CIDR removal)] protocol, artificially inseminated (AI; Day 30) and on Day 44, exposed to breeding bulls (1:40 bull to cow ratio) for the remainder of the 85 day breeding season. On Day 90, a second fecal sample was collected from all cows and the cows were examined to determine pregnancy/AI (P/AI). All cows were assigned a BCS on Day 180 and re-examined to determine pregnancy/breeding season (P/BS). Worm egg count per gram of feces (FEG) was determined by McMaster method. There were no differences (P > 0.1) between PC-LT and PC-ST groups on Day 0 for FEG (46.9 ± 13.1 vs 42.6 ± 15.2, respectively; mean ± SEM) or BCS (5.95 ± 0.12 vs 6.00 ± 0.20). The mean FEG (PC-LT, 12.3 ± 4.7 vs. PC-ST, 131.3 ± 10.9) on Day 90 and BCS (PC-LT, 6.04 ± 0.07 vs. PC-ST, 5.79 ± 0.13) on Day 180 differed (P < 0.05) between the two groups. Mean P/AI [PC-LT, 62.9 %; (471/749) vs PC-ST, 57.4 %; (409/713)] and P/BS [PC-LT, 92.9 % (696/749) vs PC-ST, 90.0 (642/713)] also differed (P < 0.05). Lower FEG at Day 90 resulted in moderate to good body condition at Day 180 and cows with moderate to good body condition at Day 180 had higher P/BS. In conclusion, lower worm burden with long-term parasite control reduced FEG and improved BCS, P/AI and P/BS.

Evaluation of parasite resistance in a beef cattle operation with use of extended-release eprinomectin for 3 years

ABSTRACT Objective Our objective was to determine whether parasite resistance to extended-release eprinomectin was present in an operation after 3 yr of eprinomectin use. Materials and Methods Fall-born Angus × Simmental heifers (224 ± 22 d of age; 171 ± 17.8 kg initial BW) were stratified by d −2 fecal egg count (FEC) and BW and assigned to 1 of 9 groups (7 heifers per group). Groups were then assigned to 1 of 3 treatments: extended-release eprinomectin (ERE; n = 3), extended-release eprinomectin and oxfendazole (ERE+O; n = 3), or saline control (CON; n = 3). Throughout the experiment, FEC and packed cell volume were evaluated 6 times, and a fecal egg reduction test was conducted on d 28. Results and Discussion There was a treatment × time interaction (P Implications and Applications Based on the fecal egg reduction test (>90%), parasite resistance was not present in an operation after 3 yr of use of extended-release eprinomectin.

Efficacy and production benefits following use of eprinomectin extended-release injection in pastured dairy heifers

A study was conducted in grazing dairy heifers to assess anthelmintic efficacy and production responses in dairy heifers treated with a single injection of eprinomectin in an extended-release formulation over a 123 day-period. The study was conducted on a pasture-based dairy in the Southeastern United States (North Carolina) over the summer months. Sixty crossbred dairy heifers were weighed and randomly allocated into 2 groups. One group (n = 30) was given 5% eprinomectin subcutaneously in the cervical region while the other group (n = 30) was given an equivalent volume of saline. Calves were weighed every 30 days throughout the trial for calculation of average daily gain and differences in overall weight gain. In addition, fecal samples were collected at days 0, 30, 60, 90 and 123 for worm egg count and coproculture. Both groups of cattle had similar worm egg concentrations at the start of the study. However, the control group had increasing concentrations of fecal worm eggs throughout the summer months while the heifers that received eprinomectin had minimal fecal worm eggs. The primary parasite species identified in this study were Haemonchus placei, Cooperia species and Ostertagia. The heifers that received eprinomectin gained 105 + 2.8 kg during the 123-day study period, representing an average daily gain of 0.85 kg/day compared to 78.3 + 4.1 kg (0.64 kg/day) for the control group. This represented a 33 % increase in average daily gain associated with deworming. The results of this study indicate that a single dose of extended-release eprinomectin was sufficient to control parasites through a 123-day summer grazing season and that administration of the anthelmintic had a significant impact on weight gain.

371 Evaluation of parasite resistance in cattle treated with extended-release eprinomectin (LongRange)

Abstract The objective was to determine parasite resistance in cattle treated with extended-release eprinomectin (LongRange) from a herd with 3 years of prior eprinomectin use. Fall-born Angus x Simmental heifers (224 ± 22 d of age) were randomly assigned 1 of 3 treatments: LongRange (LR; n = 21), LongRange and Synanthic (COMBO; n = 21), or saline-treated control (CON; n = 21). At trial initiation, all heifers were administered treatments according to label instructions. All heifers grazed endophyte-infected tall fescue in groups (n = 3 per treatment) and supplemented daily modified wet distillers grain (0.91 kg as fed per heifer) and soybean hulls (0.91 kg as fed per heifer). Prior to trial initiation and monthly thereafter, BW, packed cell volume (PCV), and fecal egg counts (FEC) were determined. There was a treatment × date interaction (P = 0.001) for fecal eggs counts. There were no differences (P ≥ 0.53) in the FEC in May or June. In July and August, the LR and COMBO heifers had decreased (P &lt; 0.01) FEC compared with CON. By September there were no differences (P = 0.84) in FEC. At d 28, there was no difference (P ≥ 0.44) in FEC reduction between LR (91% FEC reduction) and COMBO (98% FEC reduction). There was no treatment or treatment × date interaction (P ≥ 0.34) for PCV. There was a treatment × date interaction (P = 0.01) for BW. There were no differences (P ≥ 0.16) in BW during May, June, and July. In August the LR and COMBO heifers tended (P = 0.09) to have greater BW than CON. In September and October, the LR and COMBO heifers had a greater (P ≤ 0.01) BW than CON heifers. Parasite resistance to extended-release eprinomectin was not observed based on FEC reduction tests and similar BW of LR and COMBO heifers.

56 The efficacy of extended-release eprinomectin for the reduction of horn flies, face flies, and fecal egg counts of parasitic nematodes in replacement beef heifers

Abstract The purpose of this study was to evaluate the efficacy of extended-release eprinomectin against horn flies, face flies, and fecal egg counts of parasitic nematodes in crossbreed replacement beef heifers. Fifty-four heifers were randomly placed into three treatment groups (n = 18 heifers/treatment). Group 1 was administered the labeled dosage of extended-release eprinomectin at the onset of fly season (day 0). Group 2 acted as the negative control. Group 3 received the anthelmintic injection once a quarter of the heifers in the group reached the threshold treatment level for horn flies (n = 200 flies/animal; day 41). All cattle were separately pastured for the duration of the study. Throughout the study, nematode infections were measured via fecal egg counts while horn and face flies were visually monitored. Evaluation of pregnancy status was recorded at the conclusion of the study (day 144). Due to the high number of face flies, heifers were treated with insecticide dusts twice during the study (day 54 and 69). Group 1 averaged a fecal egg count of (2.3), group 2 (7.4), and group 3 (9.1) (day 111). Low egg counts for all treatment groups reflected minimal parasite burden which likely had little effect on treatment groups. Extended release eprinomectin had little influence on face flies given that all groups were above threshold at days 40, 48, and 54. At study conclusion, horn fly population was lower (P &lt; 0.05) for group 1 (405.6) compared to group 2 (680.6) and group 3 (680.6). Conception rates were greater (P &lt; 0.05) in group 1 (89%) compared to the control heifers (56%) and group 3 exhibited an intermediate rate (72%). Results indicate that although treatment with extended-release eprinomectin did not decrease the face fly burdens, it did have an effect on fecal egg counts, horn fly burdens, and subsequent pregnancy status at the conclusion of the study

122 The efficacy of extended-release eprinomectin for the reduction of horn flies, face flies, and fecal egg counts of parasitic nematodes in replacement beef heifers

Abstract The purpose of this study was to evaluate the efficacy of extended-release eprinomectin against horn flies, face flies, and fecal egg counts of parasitic nematodes in crossbreed replacement beef heifers. Fifty-four heifers were randomly placed into three treatment groups (n = 18 heifers/treatment). Group 1 was administered the labeled dosage of extended-release eprinomectin at the onset of fly season (day 0). Group 2 acted as the negative control. Group 3 received the anthelmintic injection once a quarter of the heifers in the group reached the threshold treatment level for horn flies (n = 200 flies/animal; day 41). All cattle were separately pastured for the duration of the study. Throughout the study, nematode infections were measured via fecal egg counts while horn and face flies were visually monitored. Evaluation of pregnancy status was recorded at the conclusion of the study (day 144). Due to the high number of face flies, heifers were treated with insecticide dusts twice during the study (day 54 and 69). Group 1 averaged a fecal egg count of (2.3), group 2 (7.4), and group 3 (9.1) (day 111). Low egg counts for all treatment groups reflected minimal parasite burden which likely had little effect on treatment groups. Extended release eprinomectin had little influence on face flies given that all groups were above threshold at days 40, 48, and 54. At study conclusion, horn fly population was lower (P &lt; 0.05) for group 1 (405.6) compared to group 2 (680.6) and group 3 (680.6). Conception rates were greater (P &lt; 0.05) in group 1 (89%) compared to the control heifers (56%) and group 3 exhibited an intermediate rate (72%). Results indicate that although treatment with extended-release eprinomectin did not decrease the face fly burdens, it did have an effect on fecal egg counts, horn fly burdens, and subsequent pregnancy status at the conclusion of the study

Effects of extended-release eprinomectin on fescue toxicosis, performance, and reproduction on fall-calving beef cows.

The objective of this experiment was to evaluate effects of extended-release eprinomectin on fescue toxicosis and impacts on performance and reproduction in fall-calving beef cows. Fall-calving Angus × Simmental multiparous cows [n = 335; age = 5.8 ± 2.1 yr; 586.5 ± 6.0 kg body weight (BW); 5.48 ± 0.05 body condition score (BCS)] were stratified by BW, age, and BCS and randomly assigned to one of three treatments. Treatments included a spring injection of extended-release eprinomectin (SERE) on day 0, a fall injection of extended-release eprinomectin injection (FERE) on day 84, and a saline control (CON). All treatments were administered at a rate of 1 mL/50 kg BW. Prior to the experiment, all cows were treated with oral fenbendazole to minimize parasite load. Cows grazed endophyte-infected tall fescue. Hair coat score (HCS), BW, and BCS were recorded on all cattle. Fecal egg count (FEC), respiration rate (RR), horn fly and tick count, hematocrit (% packed cell volume, PCV), and serum prolactin were analyzed on a subset of cows (35/treatment). On day 194, cows were artificially inseminated (AI) and 11 d following AI were exposed to bulls for 51 d. Milk production was estimated on day 210 on a subset of 85 cow–calf pairs (28–29/treatment). There was a tendency for a treatment × time interaction (P = 0.07) for FEC likely driven by an increase in FEC of the CON cattle at day 126 compared to SERE and FERE. There was a tendency for a treatment × time interaction (P = 0.06) for cow BW, largely driven by time differences; however, there was no effect of treatment (P = 0.84) on BW. There was no difference (P ≥ 0.13) in cow PCV, fly and tick count, BCS, HCS, RR, and serum prolactin throughout the experiment. Additionally, there was no difference (P ≥ 0.46) in Julian calving date, calf birth BW, or milk production between treatments. Interestingly, heifer calves born to FERE dams tended to have greater (P = 0.06) weaning BW compared to heifer calves born to CON dams. In addition, there was no difference (P ≥ 0.17) in heat patch scores, AI conception rates, or overall pregnancy rates between treatments. Extended-release eprinomectin did not impact cow growth performance, reproductive performance or fescue toxicity symptoms when grazing endophyte-infected tall fescue; however, calf weaning BW tended to be improved.

Effects of spring administration of extended-release eprinomectin on fescue toxicosis, performance, and reproduction of fall-born beef heifers.

The objective of this experiment was to assess the effects of eprinomectin, an extended-release injectable parasiticide, on fescue toxicosis and its impacts on beef heifer performance and reproduction. Fall-born Angus × Simmental heifers (age = 246.3 ± 22.4 d; 264.8 ± 21.1 kg body weight [BW]) were randomly assigned to one of two treatments: extended-release eprinomectin injection (ERE; n = 100) or control (CON; saline; n = 99). Treatments were administered at a rate of 1 mL/50 kg BW. Prior to experiment, heifers were dosed with oral fenbendazole to minimize parasite load. All heifers grazed endophyte-infected tall fescue as a single group and were offered a 50:50 supplement mix of corn gluten feed and soybean hulls (2.7 kg as fed per heifer per day). Body condition scores (BCS), BW, hair coat score (HCS), blood, and fecal samples were collected throughout the experiment. A subset of 40 heifers were randomly selected (20 per treatment) to assess respiration rate (RR). On d 138, heifers began a 14-d controlled internal drug release + prostaglandin synchronization protocol. Following artificial insemination (AI), heifers were exposed to five bulls for 71 d. On d 214 and 291, AI and overall pregnancy rates, respectively, were determined. There was a treatment × time interaction (P < 0.01) for BW, BCS, and average daily gain (ADG). The ERE heifers had greater (P < 0.04) BW and BCS compared to CON heifers from d 55 and 112, respectively. In addition, ERE heifers had greater (P ≤ 0.04) ADG from d 0 to 56, 56 to 112, 112 to 171, and 171 to 214; however CON heifers had greater (P < 0.01) ADG from d 214 to 291. There was no treatment × time interaction or treatment difference (P ≥ 0.27) for HCS, RR, and serum prolactin concentrations. However, serum prolactin decreased (P < 0.01) in all heifers over time. There was a treatment × time interaction (P<0.01) for fecal egg counts (FEC). The FEC did not differ (P ≥ 0.32) on d −1 or 55; however, ERE heifers had decreased (P < 0.01) FEC compared with CON heifers on d 111 (1.52 vs. 13.56 eggs per gram). The ERE heifers tended (P = 0.10) to have greater AI pregnancy rates (69% vs. 58%) and had greater (P = 0.01) overall pregnancy rates (84% vs. 68%) than CON heifers. Spring administration of extended-release eprinomectin improved BW, ADG, BCS, and AI and overall pregnancy rates in fall-born beef heifers. However, the underlying mechanism is still unclear, as there were minimal to no differences in HCS, RR, serum prolactin, and FEC.

Effects of extended-release eprinomectin on productivity measures in cow–calf systems and subsequent feedlot performance and carcass characteristics of calves

The objective of this study was to estimate the impact of a single injection of extended-release eprinomectin on economically relevant production variables in beef cows and calves as well as subsequent feedlot health, performance, and carcass traits of calves compared with a traditional, short duration anthelmintic. Animals from 13 cooperator herds across seven states were stratified within herd and assigned to one of two treatments; injectable doramectin (DOR; Dectomax; n = 828) or injectable eprinomection (EPR; Longrange; n = 832). Fecal samples were randomly collected from a subset of cows at both treatment and the end of grazing to evaluate fecal egg count (FEC). Continuous and categorical data were analyzed using the MIXED and GLIMMIX procedures of SAS, respectively. Cow treatment body weight (BW) and final BW were not different (P ≥ 0.40) between treatments. There were no differences (P ≥ 0.12) between treatments in cow ADG, change in BW, or body condition scores during the grazing season. While FEC at treatment did not differ (P = 0.18), cows treated with EPR had lower final FEC at the end of the grazing season (P = 0.02) and a greater reduction of FEC over the grazing season (P = 0.01). Calf treatment BW, weaning BW, and ADG did not differ between treatments (P ≥ 0.34). Incidence of pinkeye tended to be less (P = 0.06) for cows treated with EPR but was not different for calves (P = 0.43). Conception to AI, overall pregnancy rates, and calving interval were not different between treatments (P ≥ 0.45). A subset of calves from each herd was sent to Tri-County Steer Carcass Futurity (TCSCF) feedlot for the finishing phase. Calf BW did not differ at initiation of feeding (P = 0.20). While EPR calves tended to be heavier at reimplantation (P = 0.07), final BW and overall ADG were not different between treatments (P ≥ 0.13). Health records indicated lower morbidity for EPR calves (P = 0.05). Carcass performance including HCW, dressing percent, backfat, KPH, REA, YG, were not different between treatment groups (P ≥ 0.12). However, EPR calves had a greater marbling score, greater average quality grade (P < 0.01), and higher proportion of calves that graded average choice or greater (P = 0.03). Results of this study indicate no difference in cow or preweaning calf performance, however, carcass quality in the feedlot phase was improved. Thus, economic analysis indicates opportunities for return on investment if animals treated with EPR have improved health status and/or carcass quality during the feeding phase.

Case Study: Effects of extended-release eprinomectin on cow-calf performance and reproductive success in a fall-calving beef herd

ABSTRACT Gastrointestinal parasites cost the US beef industry $3 billion annually. Therefore, the objective of this study was to assess performance parameters and reproductive success of fall-calving beef herds treated with extended-release eprinomectin compared with a conventional anthelmintic product. In Exp. 1, 119 fall-calving cows were treated with short-duration injectable ivermectin (n = 53; CONV) or injectable extended-release eprinomectin (n = 66; EPR). Cow and calf performance, pregnancy rates, calving interval, and calving distribution were analyzed. Average daily gain and change in BW were greater in EPR cows (P ≤ 0.01) than CONV. Pregnancy rates tended to be greater for EPR than CONV cows (P = 0.15). Calves from EPR dams were younger at weaning but had greater weaning weights than calves from CONV dams (P

Concurrent treatment with a macrocyclic lactone and benzimidazole provides season long performance advantages in grazing cattle harboring macrocyclic lactone resistant nematodes

In 2013, a 118-day study was initiated to investigate the efficacy of concurrent treatment at pasture turnout with an injectable macrocyclic lactone with activity up to 28 days and an oral benzimidazole, referred to as “conventional” anthelmintics, when compared to treatment with conventional macrocyclic lactone alone or an injectable macrocyclic lactone with extended activity of 100 days or longer. A group of 210 steers were obtained from a ranch in California and transported to Idaho, USA. A total of 176 steers with the highest fecal egg counts were blocked by pre-treatment body weights and pasture location. A total of 44 pasture paddocks were assigned with 4 steers per paddock with 12 paddocks per therapeutic treatment group and 8 paddocks per controls. The four treatments were injectable doramectin (Dectomax®, Zoetis Inc., 0.2 mg kg−1BW, SC), injectable doramectin concurrently with oral albendazole (Valbazen®, Zoetis Inc., 10 mg kg−1BW, PO), extended release injectable eprinomectin (LongRange™, Merial Limited, 1 mg kg−1BW, SC) or saline. Cattle were individually weighed and sampled for fecal egg count on Days 0, 31/32, 61, 88, and 117/118 with an additional fecal sample on Day 14. At conclusion, one steer per paddock was euthanized for nematode recovery. The results from the first 32 days found evidence of macrocyclic lactone resistance against injectable doramectin and extended release eprinomectin. During this period the concurrent therapy provided nearly 100% efficacy based on fecal egg count reduction and a 19.98% improvement in total weight gain compared to controls (P = 0.039). At the conclusion of the 118-day study and past the approved efficacy for the conventional anthelmintics, the concurrent therapy with conventional anthelmintics provided a 22.98% improvement in total weight gain compared to controls (P = 0.004). The 118-day improvement in weight gain for the extended release eprinomectin group (29.06% compared to control) was not statistically different from the concurrent therapy with conventional anthelmintics. The results indicate that concurrent treatment with a conventional macrocyclic lactone and benzimidazole may provide production benefits early in the grazing period that continue throughout the entire period for cattle harboring macrocyclic lactone resistant nematodes. By using two different anthelmintic classes together, macrocyclic lactone resistant parasites were effectively controlled early in the period. Furthermore, the use of an effective conventional anthelmintic treatment regimen without an extended period of drug release may help to promote refugia and decrease the further selection for anthelmintic resistant parasites.

381 Effects of spring administration of extended-release eprinomectin (LongRange) on fescue toxicosis, performance, and reproduction of fall-born beef heifers

381 Effects of spring administration of extended-release eprinomectin (LongRange) on fescue toxicosis, performance, and reproduction of fall-born beef heifers

Season-long effectiveness of stocker-calf treatment at turnout with eprinomectin extended-release injection or a combination of injectable doramectin and oral albendazole

On May 22, 2013, 128 stocker calves enrolled in an internal parasite control study were treated according to structured allocations and placed directly onto treatment-specific, randomly allocated, similar pastures (4 animals/2 acres (0.8 hectare) pasture). Treatment groups were saline injection (8 pastures); 0.09 mg/lb (0.2 mg/kg) BW doramectin injection concomitantly with 4.54 mg/lb (10 mg/kg) BW albendazole oral suspension (12 pastures); and 0.45 mg/lb (1 mg/kg) BW eprinomectin extended-release injection (12 pastures). Over the 119-day grazing period, average daily gains ñ SE were 1.21ñ0.07, 1.46ñ0.04, and 1.52ñ0.04 lb (0.55ñ0.03, 0.66ñ0.02, and 0.69ñ0.02 kg)/day for the saline, combination, and extended-release groups, respectively; calves in the combination and extended-release groups outgained the control group (P&lt;0.05). In comparison to the saline-treated group, there were statistically significant (P&lt;0.05) reductions of strongyle fecal egg counts at 14, 30, and 58 days post-treatment (combination group) and at 14 and 30 days post-treatment (extended-release group). No significant differences in adult Haemonchus placei, Ostertagia ostertagi, Cooperia punctata, and Oesophagostomum radiatum populations between treatment groups were seen at necropsy. The combination treatment group had fewer O. ostertagi early fourth-stage larvae than did controls (P&lt;0.05). Based on results of this study, a single treatment of heavily infected and challenged stocker calves in the spring in Arkansas with either extended-release eprinomectin or doramectin+albendazole was not sufficient for adequate parasitic nematode control.

Weight gains in sucking beef calves treated with macrocylic lactone anthelmintics in either an extended-release injectable formulation or a pour-on formulation

The objective of this trial was to test the hypothesis that treating suckling beef calves grazing summer pastures with an extended-release injectable parasiticide containing eprinomectin (ERE) would result in additional weight gain when compared to ivermectin in a pour-on (POI) formulation. Extended-release eprinomectin contains the anthelmintic with a poly-lactide-co-glycolic-acid polymer allowing slow release of eprinomectin following injection with a label claim for protection against reinfection with Cooperia oncophora and Cooperia punctata for 100 d and Ostertagia ostertagi for 120 d. Pour-on ivermectin claims 21 d control for C. punctata with 14 for O. ostertagi and C. oncophora.

Comparison of ivermectin and extended-release eprinomectin deworming treatment on stocker and subsequent feedlot performance and carcass characteristics of fall-born Angus heifers

The effect of deworming beef heifers with either ivermectin or extended-release eprinomectin on performance and carcass characteristics of stocker and feedlot cattle was assessed. Sixty Angus heifers (610 +/- 50 lb initial body weight; 277 +/- 23 kg) were blocked by body condition score and body weight, and allotted to 1 of 2 injectable deworming treatments after grazing summer pasture for 35 days: (1) ivermectin (IVM) or (2) extended-release eprinomectin (ERE). After 63 days grazing, heifers were placed in a feedlot and fed a finishing ration for 150 days. Heifers were stratified by BW within grazing treatment and allotted to receive ivermectin (dewormed; DWRM) or no treatment during processing (NO) at feedlot entry. Although fecal egg counts did not differ at treatment initiation, egg counts were greater in the IVM group (5.138 eggs per gram) than in the ERE group (0.073 EPG) at the end of the grazing period (P less than 0.01). Heifers in the ERE group had greater average daily gain and greater body weight change (P=0.01) during the grazing period. There were no differences in feedlot performance or carcass characteristics (P greater than or equal to 0.09) between treatment groups. Based on this study, there may be no benefit to deworming at feedlot arrival when cattle are effectively managed to minimize internal parasite infection during the grazing period. However, even at extremely low levels of infection during grazing, parasites can significantly impact performance.