Detection of anthelmintic resistance in nematodes infecting dairy heifers in Puerto Rico

The efficacy of the anthelmintic albendazole (ALB), doramectin (DOR) and ivermectin (IVM) were evaluated in Holstein and Holstein crossbreed dairy heifers using the fecal egg count reduction test (FECRT). Dairy heifers (n=420; ~6 months of age; BW = 149 ± 39.6 kg) were evaluated in 21 dairy farms. All heifers were required to be on pasture and not have been exposed to anthelmintic treatment for a minimum of 3 months. At each dairy farm, a priori, groups of at least 18 heifers were randomly divided to be treated with IVM, or DOR, or ALB following manufacturer's instructions. Fecal samples were collected directly from the rectum 7 days before anthelmintic treatment (d-7), at the time of the treatment (d0), and 14 days after treatment (d14). Only heifers that had an average FEC ³ 100 eggs per gram of feces (average of FEC from day d-7 and d0) were considered in the FECRT. The FECRT was determined by the modified McMaster technique. Of the three-anthelmintic used, ALB (n=142) proved to be the most effective (P < 0.0005) with an efficacy of 67.47% ± 8.43. The efficacy of DOR and IVM did not differ (P = 0.8713). While DOR (n = 130) exhibited a efficacy of 25.50% ± 18.00, IVM (n = 148) exhibited a efficacy of -8.13% ± 19.89 due to an increase in FEC after treatment. Dairy farmers should implement integrated methods of nematode control to preserve the effectiveness of currently available anthelmintics.

Efficacy of Clinically Used Anthelmintics Against Toxocariasis of Buffalo Calves in Bangladesh

Toxocariasis is a paramount parasitic disease having over 50% prevalence among newborn buffalo calves in Bangladesh. The objective of this study was to compare the efficacy of clinically used anthelmintics and their subsequent effects on the hematological parameters and body weight in buffalo calves in commercial buffalo farms in coastal region. Thirty-two buffalo calves below 3 months of age with clinical Toxocara infection had been selected and treated with albendazole (ABZ), levamisole (LVM) and ivermectin (IVM). The EPG counts, hematological parameters and initial body weight of buffalo calves were recorded on the day of anthelmintic treatment (day 0). Fecal samples were collected on day 14 and 28 including hematological parameters and body weight were recorded on day 28 post-treatment. The efficacy (%) of anthelmintics were estimated by fecal egg count reduction test (FECRT). The parameters like Hb, PCV, ESR, TEC, TLC were analyzed from the blood samples. The FECRT revealed 96.83% efficacy for IVM followed by 94.23% and 85.84% for LVM and ABZ, respectively. Anthelmintic treated calves showed significant (p<0.01) increase in Hb, PCV, TEC and body weight, and decrease in ESR and TLC as a result of worm expulsion from buffalo calves after 28 days of post-treatment. Among the tested anthelmintics, IVM was found to be more effective against toxocariasis in buffalo calves. This is a novel new information on anthelmintics efficacy in buffalo calves in Bangladesh. Further studies are imperative to explore the factors responsible for high prevalence of this deadly nematode in buffalo calves.

Comparison between methods for measuring fecal egg count and estimating genetic parameters for gastrointestinal parasite resistance traits in sheep

Fecal egg count (FEC) is an indicative measurement for parasite infection in sheep. Different FEC methods may show inconsistent results. Not accounting for inconsistencies can be problematic when integrating measurements from different FEC methods for genetic evaluation. The objectives of this study were to evaluate the difference in means and variances between two fecal egg counting methods used in sheep, the Modified McMaster (LMMR) and the Triple Chamber McMaster (LTCM); to estimate variance components for the two FEC methods, treating them as two different traits; and to integrate FEC data from the two different methods and estimate genetic parameters for FEC and other gastrointestinal parasite resistance traits. Fecal samples were collected from a commercial Rideau-Arcott sheep farm in Ontario. Fecal egg counting was performed using both Modified McMaster and the Triple Chamber McMaster methods. Other parasite resistance trait records were collected from the same farm including eye score (FAMACHA ©), body condition score (BCS), and body weight (WT). The two FEC methods were highly genetically (0.94) and phenotypically (0.88) correlated. However, the mean and variance between the two FEC methods were significantly different (P &lt; 0.0001). Therefore, re-scaling is required prior to integrating data from the different methods. For the multiple trait analysis, data from the two fecal egg counting methods were integrated (LFEC) by using records for the LMMR when available and replacing missing records with re-standardized LTCM records converted to the same mean and variance of LMMR. Heritability estimates were 0.12 ± 0.04, 0.07 ± 0.05 , 0.17 ± 0.06, and 0.24 ± 0.07 for LFEC egg count, FAMACHA ©, BCS, and WT, respectively. The estimated genetic correlations between fecal egg count and the other parasite resistance traits were low and not significant (P&gt;0.05) for FAMACHA © (r= 0.24 ± 0.32) and WT (r= 0.22 ± 0.19), and essentially zero for BCS (r= -0.03 ± 0.25), suggesting little to no benefit of using such traits as indicators for LFEC.

The efficacy of a single oral dose of albendazole against soil-transmitted helminthiasis in Ogun State, Nigeria

Soil Transmitted Helminths (STHs) are Neglected Tropical Diseases of global public health importance. This study evaluated the efficacy of albendazole (ALB) amongst primary school children aged 6 – 16 years in STH-endemic communities in Ogun State, Nigeria. Demographic characteristics were obtained and stool samples were collected and analysed by Kato-Katz at baseline and 15 and 21 days post-treatment. All study participants were treated with a single ALB 400 mg tablet. A total of 282 participants were screened at baseline, of which 151 were found to be excreting STH (51.4%) of which A. lumbricoides was the most prevalent STH (n = 137, 48.6%), followed by hookworm (n = 60 children, 21.3%) and T. trichiura (n = 3; 1.1%). The prevalence across the four schools varied from 31.3% to 73.9% for A. lumbricoides, from 6.8% to 56.3% for hookworm, and from 0.0% and 2.2% for T. trichiura infections. Of the 151 children excreting any STH infection at baseline, 131 (86.8%) provided a stool sample 15 and 21 days after treatment. The mean fecal egg counts across these complete cases at baseline was 5,096 (± 13,735) eggs per gram (EPG) for A. lumbricoides, 2,202 (±7,849) for hookworms and 288 (±375) for T. trichiura. Fifteen days after drug administration the therapeutic efficacy, measured as the reduction in mean fecal egg count (FEC) following drug administration (ERR), was 99.7% (95CI: 99.4-99.9) for A. lumbricoides and 69.2% (95CI: 28.7-92.8) for hookworms. The hookworm ERR at day 14 was reduced due to the continued high egg output of one highly infected individual. One week later, 21 days following drug administration, ERR for hookworm also reached satisfactory levels (99.4% (95CI: 98.7-99.8)). This study highlights that ALB still shows satisfactory efficacy to Ascaris and hookworm infections in Ogun State, Nigeria.

PSXIV-19 Heritability for growth and resistance to gastrointestinal parasitism in meat goats and hair sheep

Genetic selection for resistance to internal parasitism is of great research interest. Heritabilities were determined for average daily gain (ADG), logarithmic transformed fecal egg count (FEC), packed cell volume (PCV), and serum immunoglobin (Ig) levels of growing male meat goats and hair sheep from different farms in the southcentral USA during three consecutive central performance tests (CPT). Tests entailed 7–10 wk of data collection after artificial infection with Haemonchus contortus. In year 1, animals evaluated were selected randomly and in years 2 and 3 progeny of CPT sires classified as highly or moderately resistant, which included 46, 50, and 51 Boer, Kiko, and Spanish and 59, 61, 34, and 46 Dorper, Katahdin-farm A, Katahdin-farm B, and St. Croix, respectively. Females were classified accordingly on-farm based on FEC and FAMACHA. Pedigree records consisted of 32 and 57 known sires, 95 and 152 known dams including 4 and 10 full-sibs and 97 and 149 half-sibs for goats and sheep, respectively. Variance components and heritabilities were estimated by AIREML using WOMBAT with a multivariate animal model. Heritability estimates were 0.48 ± 0.214 and 0.85 ± 0.157 of ADG, 0.31 ± 0.237 and 0.20 ± 0.172 of FEC, 0.60 ± 0.206 and 0.24 ± 0.185 of PCV, 0.26 ± 0.172 and 0.51 ± 0.167 of IgA, 0.335 and 0.543 of IgM, and 0.14 ± 0.192 and 0.31 ± 0.190 of IgG for goats and sheep, respectively. Reasons for relatively high heritabilities for all traits include the low residual variance estimates due primarily to a standardized environment in the performance test. In conclusion, moderate to high heritabilities were found for growth performance and response to parasite infection for growing meat goat and hair sheep males under a standardized environment that suggests considerable for genetic improvement through selection.

PSXIV-22 Selection for low fecal egg count estimated breeding value correlates with greater circulating antibody in sheep

Sheep selected for resistance to gastro-intestinal parasites have been shown to have greater survivability to weaning. Data from Katahdin sheep indicates that selection based on post-weaning fecal egg count estimated breeding values (PWFEC EBV) may further improve generalized immunity. However, no data exists to confirm this increased circulating antibody occurs in breeds genetically unrelated to Katahdins. In the fall of 2020 post-weaning blood and fecal samples were collected from Shropshire sheep (n = 42) and Polypay sheep (n = 91). The blood samples were analyzed for total immunoglobulin-G (IgG) using ELISA. Shropshire sheep were sorted into low (PWFEC EBV &lt; 0) and high (PWFEC EBV &gt; 0) groups based on fecal egg count (FEC), which were analyzed via a modified McMaster’s method. Polypay sheep were sorted into three groups by PWEC EBV; A (&lt; -50) B (&gt;-50 &lt; +50) and C (&gt;+50). In Shropshire group, individuals with low FEC had greater average IgG concentration (87.9 µg/mL) than those with high FEC (62.4 µg/mL) (P &gt; 0.05). In the Polypay group, sheep in PWFEC EBV group A had numerically higher IgG concentration (86.2 µg/mL) than sheep in group B (71.2 µg/mL) and group C (53.1 µg/mL) (P &gt; 0.05). While data in either breed were not significant, the trend observed across breeds indicate that sheep with a lower PWFEC EBV have numerically greater circulating antibody.

PSXIV-18 Genetic improvement for resistance to gastrointestinal parasitism in growing meat goats and hair sheep through a centralized performance test in the southcentral USA

Progress from selecting meat goats and hair sheep from different farms in the southcentral United States for resistance to internal parasitism during three consecutive central performance tests was evaluated. Tests entailed 7–10 wk of data collection after artificial infection of growing males with Haemonchus contortus larvae. There were 44, 50, and 50 Boer, Kiko, and Spanish goats and 54, 55, 34, and 47 Dorper, Katahdin-farm-A, Katahdin-farm-B, and St. Croix sheep, respectively. In year 1, males were randomly selected and in years 2 and 3 were progeny of sires and females classified as highly and moderately resistant. Criteria for males was average daily gain and residual feed intake during the performance test and means of fecal egg count (FEC) and packed cell volume after artificial infection and for females was FEC and FAMACHA on-farm. There were interactions in FEC of breed×year (P &lt; 0.001) for both species (1,046; 1,134; and 2,630 for Boer; 3,781; 1,239; and 1,216 for Kiko; 1,303; 1,357; and 1,464 for Spanish; 3,288; 1,956; and 1,315 for Dorper; 1,528; 1,759; and 2,241 for Katahdin-A, 2,414; 3,874; and 1,793 for Katahdin-B; and 1,371; 1,160; and 1,175 eggs/g for St. Croix in years 1, 2, and 3, respectively) and year×resistance group (RG; P = 0.005) for goats (1,359; 610, and 552 for high; 1,951; 1,268; and 1,440 for moderate; 2,821; 1,852; and 3,118 eggs/g for low RG in years 1, 2, and 3, respectively) but not for sheep (P = 0.639). In conclusion, resistance appeared greatest for Spanish and St. Croix within species and was increased by selection of Kiko and Dorper. For highly resistant goats, lower FEC in year 2 and 3 vs. 1, compared with no year differences for moderate and low RG, indicates selection progress, and the lack of similar differences for sheep may reflect their relatively greater resistance.

PSI-19 Influence of cattle breed and forage type on organic dairy heifer performance

Many breeds of dairy cattle exist, but questions remain about their relative performance within exclusively forage-based systems in the United States. This paucity of data is especially apparent in relation to heifer development, which is the second largest expense on most dairy farms. We evaluated the performance of prepubertal heifers from four different genetic backgrounds (“breeds”) within a rotational grazing system in the Intermountain West. For each of two 105-day grazing seasons, 24 dairy heifers from each of four different breeds [Holstein (HO), Jersey (JE), Holstein/Jersey crossbred (HJ), and Swedish Red/Holstein/Montbeliarde crossbred (SHM)] were randomly assigned to one of two pasture treatments that consisted of either grass only (MONO) or grass interseeded with the legume birdsfoot trefoil (BFT; MIX). Main effects of treatment and breed (and potential interactions) on heifer average daily gain (ADG), change in percent mature body weight (CPMBW), fecal egg count (FEC), rumen volatile fatty acids (VFA), and body condition scores (BCS) were evaluated. There was a significant effect of pasture treatment on ADG, with MIX heifers averaging 0.48 kg of gain/day, whereas MONO heifers averaged 0.29 kg/day (P &lt; 0.0001). Change in BCS was significantly affected by treatment (P = 0.0012) and breed (P &lt; 0.0001). Significant effects of treatment (P &lt; 0.0001), breed (P = 0.0005), and treatment*breed (P = 0.0005) on CPMBW were also found. Treatment and breed had no effect on FEC or total rumen VFA content (P &gt; 0.05). Overall, we found that Jerseys were able to gain a higher percentage of their mature body weight and lose less body condition while on pasture than heifers of other breeds. We also found that grazing BFT can have significant positive effects on ADG, BCS, and CPMBW. Further research is needed to more thoroughly evaluate the influence of heifer genetics (breed) on metrics of growth, health, reproductive performance, and production in pasture settings.

PSXII-30 Genetic and phenotypic correlations for growth and resistance to gastrointestinal parasitism in meat goats and hair sheep

Genetic and phenotypic correlations for growth and response to parasite infection traits were estimated for growing male meat goats and hair sheep from different farms in the southcentral United States during three consecutive central performance tests (CPT). Data were collected for 7–10 wk after artificial infection with Haemonchus contortus, which included average daily gain (ADG), fecal egg count (FEC), packed cell volume (PCV), and immunoglobin (Ig) levels. Animals evaluated were selected randomly in year 1 and in years 2 and 3 progeny of CPT sires classified as highly or moderately resistant and included 46, 50, and 51 Boer, Kiko, and Spanish goats and 59, 61, 34, and 46 Dorper, Katahdin-farm A, Katahdin-farm B, and St. Croix sheep, respectively. Females were classified accordingly on-farm based on FEC and FAMACHA. Pedigree records included 4 and 10 full-sibs and 97 and 149 half-sibs for goats and sheep, respectively. Variance components and correlations were estimated by AIREML using WOMBAT with a multivariate animal model. The additive genetic correlation between FEC and PCV was negative for goats (r=-041, P &lt; 0.001) but positive for sheep (r=0.21, P = 0.004), whereas the phenotypic correlation between FEC and PCV was nonsignificant for goats but negative for sheep (r=-0.252, P &lt; 0.001). The genetic correlation between FEC and IgA was positive (r=0.39, P &lt; 0.001) for goats but nonsignificant (P = 0.439) for sheep, whereas those of FEC with IgM and IgG were both negative (r=-0.369 and -0.732 with IgM and r=-0.284 and -0.702 for goats and sheep, respectively; P &lt; 0.001). Genetic and phenotypic correlations between ADG and FEC were nonsignificant for both species. In conclusion, different relationships of FEC and PCV between species require careful attention during selection and the lack of relationship between ADG and FEC suggests that selection of growing male meat goats and hair sheep for resistance to internal parasitism will not adversely affect growth performance.

363 Relationship Between Parasite Load and Performance in Goat Kids at Weaning and Early Post Weaning

Goats are small ruminants that have enormous potential to boost the economy and be a major source of income especially to marginal farmers and landless laborers. A very common and economically important condition, which affects domestic livestock species worldwide, is Gastrointestinal (GI) parasitism. Haemonchus contortus is the gastrointestinal parasite most common in small ruminants. To better understand the impact of GI parasitism, a study was conducted to research the relationship between parasite load and performance in goat kids at weaning and 60 d post-weaning. Fecal samples were collected at weaning and 60 d post-weaning and egg counts were performed using the modified McMasters technique. Data collected included weights, Fecal Egg Count at weaning, and at 60 d post-weaning. The average fecal egg count at weaning was 830 eggs per gram and 1103 eggs per gram 60 d post-weaning for H. contortus. Egg count at weaning was significantly related to weight at both weaning and 60 d post-weaning (P &lt; .0001 and P = .0003 respectively), but not to ADG (P &gt; .05). Fecal egg count at 60 d post-weaning was not significantly related to either weight or ADG (P &gt; .05). Egg counts at weaning and 60 days post-weaning were not related (P = .0708). The results indicate that early parasite infection can influence animal weights. The lack of a significant correlation between egg counts at weaning and 60 d post weaning indicates a need to evaluate parasite load at later ages in kids when selecting for resistance.