This publication discusses a research project designed to explore the genetics of resistance to gastrointestinal parasites in sheep and goats. Written by Zaira M. Estrada Reyes, Yoko Tsukahara, Arthur L. Goetsch, Terry A. Gipson, Tilahun Sahlu, Richard Puchala, and Raluca G. Mateescu, and published by the UF/IFAS Department of Animal Sciences, January 2022.

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.

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 < 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.

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 < 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 < 0.001). The genetic correlation between FEC and IgA was positive (r=0.39, P < 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 < 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.

Background: Gastrointestinal nematode infection (GNI) is the most important disease affecting the small ruminant industry in U.S. The environmental conditions in the southern United States are ideal for the survival of the most pathogenic gastrointestinal nematode, Haemonchus contortus . Host genetic variation for resistance to H. contortus allows selective breeding for increased resistance of animals. This selection process increases the prevalence of particular alleles in sheep and goats and creates unique genetic patterns in the genome of these species. The aim of this study was to identify loci with divergent allelic frequencies in a candidate gene panel of 100 genes using two different approaches (frequentist and Bayesian) to estimate F st outliers in three different breeds of sheep and goats exposed to H. contortus . Results: Our results for sheep populations showed SNPs under selection in C3AR1 , CSF3 , SOCS2 , NOS2 , STAT5B , TGFB2 and IL2RA genes using frequentist and Bayesian approaches. For goats, SNPs in CD1D , ITGA9 , IL12A , IL13RA1, CD86 and TGFB2 genes were under selection. Common signatures of selection in both species were observed in NOS2 , TGFB2 and TLR4 genes. Directional selection was present in all SNPs evaluated in the present study. Conclusions: A total of 13 SNPs within 10 genes of our candidate gene panel related to H. contortus exposure were identified under selection in sheep populations. For goats, 11 SNPs within 7 genes were identified under selection. Results from this study support the hypothesis that resistance to H. contortus is likely to be controlled by many loci. Shared signatures of selection related to mechanisms of immune protection against H. contortus infection in sheep and goats could be useful targets in breeding programs aimed to produce resistant animals with low FEC.

Haemonchus contortus infections are an important source of animal production loss to livestock industry. Genetics of helminth resistance involves a complex set of factors related to the host immune response. The increasing use of genetic markers such as single nucleotide polymorphisms (SNPs) in genome wide association studies (GWAS) offers the potential to identify loci or regions associated with nematode resistance in small ruminants. The aims of this study were: (1) to use a targeted sequencing approach to identify SNPs in 100 genes related to immune response during Haemonchus contortus exposure in growing males of St. Croix, Katandin and Dorper sheep, and in Kiko, Boer and Spanish goats, and (2) to perform an association analysis for fecal egg count (FEC), packed cell volume (PCV), immunoglobulin levels (IgA, IgG and IgM) and average daily gain (ADG) in the populations under study. After quality control (call rate < 95%, MAF < 0.05), 1356 SNPs (sheep) and 1,029 SNP5 (goats) were used for the association analysis. A mixed model was used to analyze the phenotypic information. To control for population structure, the genomic relationship matrix (G) calculated from marker information was included in the model. Fixed effects included year and breed. Bonferroni correction was used to control for multiple testing. For sheep, SNPs located on OAR1 (42487870, 42489606) and OAR2 (192231080, 26321541) were significantly associated with IgM, ADG, and FEC. For goats, SNPs on CHR3 (42898132) and CHR22 (23066762) were associated with ADG and IgM. In both species, no significant associations were found for IgA, IgG and PCV. The results from this study revealed genes involved in the immune response to H. contortus exposure and provide additional SNP marker information that has potential to aid selection of resistance to gastrointestinal parasites in sheep and goats from different breeds. Significant SNP5 within IL12RB2, NFIL3 and STAT4 genes could be potential markers for IgM, FEC and ADG in sheep populations. For goats, potential markers for IgM and ADG were identified within IL5RA and IL12RB2 genes. These results could be directly implemented in the populations used in this study, however, they should be validated before using these markers in other sheep and goat populations.

s from the 2013 Oklahoma Research Day Held at the University of Central Oklahoma 05. Mathematics and Science

The relationship between packed cell volume (PCV) and fecal egg count (FEC) in different breeds of meat goats and hair sheep infected with gastrointestinal nematodes, including Haemonchus contortus, was characterized. Growing males from eight commercial and two research farms (one Kiko, Spanish, Dorper, and St. Croix; three Boer; four Katahdin) in the southcentral United States were evaluated in a central performance test with ad libitum intake of a 50% concentrate pelleted diet. There were 84 Boer, 55 Kiko, and 57 Spanish goats and 52 Dorper, 129 Katahdin, and 49 St. Croix sheep. During adaptation, animals were dewormed then dosed with 10,000 infective H. contortus larvae. PCV and FEC were determined before deworming (i.e., natural infection potentially with multiple internal parasites) and 21, 28, 35, 42, and 49 days after artificial infection. Effects of species, breed, and year were analyzed with mixed effects models including day of sampling post dosing as a repeated measure and FEC and FEC x breed as covariates. Moreover, differences in correlation coefficients between PCV and logarithmic FEC (lnFEC) among species, breed, year, and day of sampling were evaluated. Breed affected (P <= 0.001) PCV in goats (24.8, 27.2, and 26.0% for Boer, Kiko, and Spanish, respectively; SEM = 0.42) and sheep (29.8, 26.7, and 31.0% for Dorper, Katahdin, and St. Croix, respectively; SEM = 0.28). There were effects of FEC x breed (P <= 0.029) on PCV for Boer, Kiko, Dorper, Katahdin, and St. Croix (-0.31, -0.33, -0.46, -0.46, and -0.49% per 1000 eggs, respectively) but not for Spanish goats (P = 0.451). With all data, PCV and lnFEC with natural infection were highly correlated (P < 0.001) for Boer and Kiko goats and Dorper and Katahdin sheep (r = -0.59, -0.67, -0.77, and -0.84, respectively) but not for Spanish goats or St. Croix sheep (P >= 0.323). Correlation coefficients for artificial infection with H. contortus were significant (P <= 0.002) except for Spanish goats, although values were lower (-0.40, -0.21, -0.23, -0.47, and -0.28 for Boer, Kiko, Dorper, Katahdin, and St. Croix, respectively) compared with natural infection. In conclusion, PCV was not related to FEC in Spanish goats infected either naturally or artificially, and the nature of the relationship varied among breeds of goats and sheep. Based on the magnitude of the FEC x breed coefficient, sheep incurred a relatively greater reduction in PCV as FEC increased, and correlation coefficients indicate stronger relationships with natural than artificial infection.

Packed cell volume (PCV) and fecal egg count (FEC) have been used as indirect and direct indicators of haemonchosis, respectively. The relationship between PCV and FEC was evaluated with growing hair sheep and meat goats in 3 central sire performance tests. There were 52 Dorper (3.9 ± 0.13 mo old; initial BW 28.2 ± 0.74 kg), 96 Katahdin (3.8 ± 0.05 mo; 31.0 ± 1.12 kg), 49 St. Croix (4.3 ± 0.06 mo; 19.0 ± 0.77 kg), 48 Boer (3.9 ± 0.08 mo; 19.4 ± 0.78 kg), 55 Kiko (3.6 ± 0.06 mo; 19.1 ± 0.46 kg), and 57 Spanish (4.0 ± 0.09 mo; 18.0 ± 0.44 kg) males used. A 50% concentrate pelleted diet was consumed ad libitum in confinement. Animals were dewormed then dosed with 10,000 infective Haemonchus contortus larvae, with PCV and FEC determined 21, 28, 35, 42, and 49 d later. The PCV and FEC were correlated (P=0.509). A mixed effects model for each species included fixed effects of breed, year, breed×year, day as a repeated measure, and log transformed FEC (lnFEC) and lnFEC×breed as covariates. Breed affected (P=0.004) PCV in goats (24.9, 27.1, and 25.9% for Boer, Kiko, and Spanish, respectively; SEM=0.42) but not in sheep (P=0.40; 30.2, 26.6, and 31.2% for Dorper, Katahdin, and St. Croix, respectively; SEM=0.29). There were effects of lnFEC×breed (P≤0.01) for Dorper, Katahdin, St. Croix, Boer, and Kiko (-0.0011, -0.0005, -0.0006, -0.0005, and -0.0009% per egg) but not Spanish (-0.0002% per egg; P=0.87). In conclusion, PCV does not appear highly reflective of FEC in Spanish goats infected with H. contortus, and the nature of the relationship varied among other breeds of sheep and goats. Based on the magnitude of the lnFEC×breed coefficient, Dorper sheep and Kiko goats incurred relatively greater reduction in PCV as FEC increased, and correlations indicate strongest relationships for Katahdin sheep and Boer goats.

The aim of this study was to identify single nucleotide polymorphisms (SNPs) associated to internal parasite resistance in sheep and goats exposed to H. contortus, using a targeted sequencing approach. Three different breeds of sheep (St. Croix, Katahdin and Dorper) and goats (Spanish, Boer and Kiko) were used in this study. Dewormed male animals were infected with 10,000 L3 H. contortus larvae. Average daily gain (ADG), fecal egg count (FEC) and package cell volume (PCV) were measured in all animals. The level of IgA, IgM and IgG was measured from serum samples at 21 days post-infection. Targeted sequencing panel included 100 candidate genes for immune response against H. contortus. SNPs were discarded if call rate < 95% and minor allele frequency ≤0.01. A mixed model was used to analyze the response variables and included the identity by state matrix. Year and breed were included as fixed effects. Bonferroni correction was used to control for multiple testing. Thirty two SNPs on chromosomes 1, 2, 5, 11, 12, 16, 17, 19, 24 and X were significant for different traits. For ADG and IgM, significant SNPs were located within IL12RB2 and IL4R genes. For IgA and PCV, one common peak was significant to both traits in exon 2 of CD86 gene. For IgG and IgM, significant regions were observed on IL5RA. Significant regions for FEC and PCV were identified in the NFIL3 gene. These results suggest that chromosomal regions related to cytokine receptors and membrane proteins expressed by antigen presenting cells, play an important role in the expression of resistant phenotypes. In conclusion, potential immune like loci could be used as DNA markers for resistance in sheep and goats exposed to H. contortus.

Effects of the level of a brackish water source (BRW; 5,600 mg/L total dissolved salts; TDS) and higher levels of TDS through the addition of NaCl on feed intake, digestion, and heat energy in growing Boer goat wethers (GRO-G) and mature Boer (MAT-G) and Katahdin sheep wethers (MAT-S) were determined. Five GRO-G (22 ± 2.5 kg; 0.76 ± 0.121 yr of age), MAT-G (52 ± 5.0 kg), and MAT-S (66 ± 4.2 kg) were assigned to three simultaneous 5 × 5 Latin squares with 3-wk periods. Treatments within squares were ad libitum intake of fresh water (0-BRW), 50% fresh water and 50% BRW (50-BRW), 100% BRW (100-BRW), 100-BRW plus 3,450 mg/L NaCl (Low-SLW), and 100-BRW plus 6,900 mg/L NaCl (Mod-SLW). Total water intake was not influenced by TDS level with GRO-G or MAT-S but increased linearly with increasing TDS (P=0.004) for MAT-G (952, 1,087, 1,284, 1,192, and 1,372 g/d for 0-BRW, 50-BRW, 100-BRW, Low-SLW, and Mod-SLW, respectively; SEM=147.7). Intake of OM was not influenced by water treatment with GRO-G but changed quadratically as TDS increased (P=0.049) with MAT-G (744, 749, 785, 732, and 703; SEM=76.3) and linearly (P=0.065) with MAT-S (870, 867, 835, 788, and 694 g/d for 0-BRW, 50-BRW, 100-BRW, Low-SLW, and Mod-SLW, respectively; SEM=80.0). Total tract OM digestion in MAT-G and MAT-S was not influenced by water TDS level but decreased linearly (P=0.004) and changed quadratically (P=0.054) in GRO-G (59.3, 55.5, 47.8, 47.0, and 49.5% for 0-BRW, 50-BRW, 100-BRW, Low-SLW, and Mod-SLW, respectively; SEM=4.67). Intake of ME decreased linearly with increasing TDS for MAT-G (P=0.014; 458, 458, 441, 449, and 381; SEM=34.2) and MAT-S (P=0.045; 384, 361, 328, 317, and 289; SEM=33.2) and increased linearly and changed quadratically (P≤0.031) for GRO-G (519, 402, 321, 319, and 363 kJ/kg BW0.75 for 0-BRW, 50-BRW, 100-BRW, Low-SLW, and Mod-SLW, respectively; SEM=54.5). Similarly, recovered energy (RE) decreased linearly with increasing TDS for MAT-G (P=0.037; 0.73, 0.66, 0.18, 0.96, and -0.86; SEM=0.534) and MAT-S (P=0.042; -0.58, -1.54, -2.20, -2.02, and -2.67; SEM=0.645) and increased linearly and changed quadratically (P≤0.048) for GRO-G (0.56, -0.63, -1.40, -1.01, and -0.51 MJ/d for 0-BRW, 50-BRW, 100-BRW, Low-SLW, and Mod-SLW, respectively; SEM=0.576). In conclusion, ME intake and RE for growing goats were more adversely affected by increasing BRW level compared with mature small ruminants because of decreased digestibility. Conversely, decreases in ME intake and RE for MAT-S with increasing TDS primarily related to decreasing feed intake, with relatively small effects for MAT-G associated with the Mod-SLW treatment.

Fifty Alpine goats at 125 ± 3.0 days-in-milk were given access in Calan gate feeders to a 40% forage diet for 12 wk continuously (Control), during daytime (Day) or night (Night), or for 2 or 4 h/day after milking in the morning and afternoon (2Hour and 4Hour, respectively), resulting in few significant effects. In a second 12-wk experiment, average daily gain (ADG) by 40 Alpines at 14 ± 0.7 days-in-milk (73, 39, 11, 24, and 21 g) was greater for Control than for the average of other treatments, milk yield was similar among treatments, milk fat was lower (P = .089) for Control (3.41%, 3.88%, 4.21%, 3.70%, and 3.49%), and milk energy was not affected (8.20, 7.36, 9.53, 8.56, and 6.91 MJ/day for Control, 2Hour, 4Hour, Day, and Night, respectively). Metabolizable energy intake (31.25, 22.69, 25.92, 26.69, and 23.46 MJ/day) and heat energy (17.51, 13.34, 14.09, 15.54, and 15.25MJ/day) were greater and milk energy relative to ME intake was lower for Control (26.0%, 31.9%, 37.6%, 31.4%, and 30.0% for Control, 2Hour, 4Hour, Day, and Night, respectively). In conclusion, continuous diet access of dairy goats in early to mid-lactation can affect partitioning of nutrients between milk synthesis and tissue accretion differently than some restricted feeder access treatments.

The effect of Ovar-DRA and Ovar-DRB1 genotypes on faecal egg count (FEC) was determined in sheep and goats infected with Haemonchus contortus. One hundred and forty-three sheep from 3 different breeds (St. Croix, Katahdin and Dorper) and 150 goats from three different breeds (Spanish, Boer and Kiko) were used. Parasitological (FEC), haematological (packed cell volume) and immunological (IgA, IgG and IgM) parameters were measured. Sheep populations showed a higher FEC and humoural response than goat breeds. Genotypes were determined by high-resolution melting assays and by conventional PCR. For Ovar-DRA, sheep and goats carrying the AA genotype showed significant lower FEC than AG and GG genotypes. The additive effect was found to be 115.35 less eggs per gram of faeces for the A allele for goats. For Ovar-DRB1, only in sheep, the GC genotype was associated with low FEC. The additive effect was 316.48 less eggs per gram of faeces for the G allele, and the dominance effect was 538.70 less eggs per gram of faeces. The results indicate that single nucleotide polymorphisms within Ovar-DRA and Ovar-DRB1 could be potential markers to be used in selection programmes for improving resistance to Haemonchus contortus infection.

A study was conducted to evaluate effects of the level of a brackish water source (5596 mg/l total dissolve salts; TDS) and higher levels of TDS through addition of NaCl on feed intake, digestion, and heat energy in growing Boer goat wethers (GRO-G) and mature Boer (MAT-G) and Katandin sheep wethers (MAT-S). Five GRO-G (22.1 +/- 2.50 kg; 0.76 +/- 0.121 yr of age), five MAT-G (52.2 +/- 4.99 kg), and five MAT-S (65.5 +/- 4.17 kg) were assigned to three simultaneous 5 x 5 Latin squares with 3-wk periods. Treatments within squares were ad libitum intake of fresh water (0-BRW), 50% fresh water and 50% brackish water (50-BRW), 100% brackish water (100-BRW), 100-BRW plus 3450 mg/l NaCl (Low-SLW), and 100-BRW plus 6900 mg/l NaCl (Mod-SLW). Total water intake was not influenced by TDS level with GRO-G or MAT-S but increased linearly with increasing TDS (P = 0.004) for MAT-G (952, 1087, 1284, 1192, and 1372 g/day for 0-BRW, 50-BRW, 100-BRW, Low-SLW, and Mod-SLW, respectively; SEM = 147.7). Organic matter (OM) intake was not influenced by water treatment with GRO-G but changed quadratically as TDS increased (P = 0.049) with MAT-G (744, 749, 785, 732, and 703; SEM = 76.3) and linearly (P = 0.065) with MAT-S (870, 867, 835, 788, and 694 g/day for O-BRW, 50-BRW, 100-BRW, Low-SLW, and Mod-SLW, respectively; SEM = 80.0). Total tract OM digestion in MAT-G and MAT-S was not influenced by water TDS level but decreased linearly (P = 0.004) and tended to change quadratically (P = 0.054) in GRO-G (59.3, 55.5, 47.8, 47.0, and 49.5% for 0-BRW, 50-BRW, 100-BRW, Low-SLW, and Mod-SLW, respectively; SEM = 4.67). Intake of metabolizable energy (ME) decreased linearly with increasing TDS for MAT-G (P = 0.014; 458, 458, 441, 449, and 381; SEM = 34.2) and MAT-S (P = 0.045; 384, 361, 328, 317, and 289; SEM = 33.2) and increased linearly and changed quadratically (P <= 0.031) for GRO-G (519, 402, 321, 319, and 363 kJ/kg BW0.75 for 0-BRW, 50-BRW, 100-BRW, Low-SLW, and Mod-SLW, respectively; SEM = 54.5). In conclusion, increasing TDS concentration in drinking water had effects on intake and digestion that differed among animal types, with ME intake of growing goats more adversely affected by increasing brackish water level compared with mature small ruminants because of decreased digestibility. Conversely, decreases in ME intake for MAT-S with increasing TDS primarily related to decreasing feed intake, with relatively small effects for MAT-G associated with the Mod-SLW treatment.

Restricting periods of diet access to lactating dairy goats could influence level or efficiency of production and offer different management options. Therefore, 40 Alpine goats (12 and 28 of parity 1 and ≥2, respectively) with initial BW of 58.0 kg (SEM 1.50) and 14.2 d in milk (SEM 0.72) were offered a 40% forage diet (16.6% CP and 37.5% NDF; 20% alfalfa pellets, 10% cottonseed hulls, 10% coarsely ground grass hay, 12.9% wheat middlings, 12.9% rolled oats, 12.9% rolled corn, 11.0% soybean meal, 3.0% soybean oil, 5.0% molasses, and 2.3% other ingredients) free choice in Calan gate feeders for 12 wk. Feed access was continuous other than during morning and afternoon milking (Control), during the day for 8 h (Day) or night for 16 h (Night), or for 1 or 2 h after morning and afternoon milking (2Hour and 4Hour, respectively). Digestibilities were not influenced by treatment (e.g., OM: 73.1, 76.9, 77.1, 76.3, and 77.3% [SEM 1.81]), DMI was greater (P < 0.05) for Control than for most treatments (2.07, 2.23, 2.70, 2.33, and 2.01 kg/d [SEM 0.157]), and ADG was greater (P = 0.019) for Control than for the mean of restricted feeder access treatments (39, 11, 73, 24, and 21 g [SEM 17.7] for 2Hour, 4Hour, Control, Day, and Night, respectively). Milk yield was similar among treatments (2.60, 3.24, 3.05, 3.07, and 2.58 kg/d [SEM 0.375]), fat concentration tended (P = 0.089) to be lower for Control than for other treatments (3.88, 4.21, 3.41, 3.70, and 3.49% [SEM 0.208]), and milk energy yield was not affected by treatment (7.36, 9.53, 8.20, 8.56, and 6.91 MJ/d [SEM 1.071] for 2Hour, 4Hour, Control, Day, and Night, respectively). Intake of ME (22.69, 25.92, 31.25, 26.69, and 23.46 MJ/d [SEM 2.184]) and heat energy (13.34, 14.09, 17.51, 15.54, and 15.25 MJ/d [SEM 0.921]) were greater (P ≤ 0.011) for Control than for other treatments, resulting in milk energy that was 31.9, 37.6, 26.0, 31.4, and 30.0% of ME intake for 2Hour, 4Hour, Control, Day, and Night, respectively (SEM 3.08). In conclusion, continuous diet access may affect partitioning of nutrients between milk synthesis and tissue accretion differently than some restricted feeder access treatments, particularly 4Hour.

Thirty-three yearling Katandin sheep (KAT, 38.9 kg) and Boer (BOE, 28.6 kg) and Spanish goat wethers (SPA, 22.7 kg) were used to determine conditions appropriate for evaluating resilience to high heat load index (HLI). Grass hay (69% NDF and 9.5% CP) was consumed ad libitum with concentrate supplemented at 0.5% BW. Period 1 was 2 wk and periods 2-5 were each 1 wk. Target HLI for the five periods during the day/night was 70/70, 80/70, 90/76.5, 95/80.75, and 100/85, and measured HLI was 66/66, 80/75, 92/84, 97/86, and 101/89, respectively. Respiration rate increased with advancing period except from period 4-5 when there was a smaller decline for KAT than for BOE or SPA. Rectal temperature also increased as the experiment progressed until period 4 and was similar among animal types in period 5 when values for BOE and SPA were lower than in period 4, in contrast to similar values for KAT. Respiration rate at 13:00 and 17:00 h increased with advancing period up to a plateau at 150-155 breaths/min converse to much lower rates (i.e., 32-83) at 06:00 in periods 2-5. Respiration rate at 06:00 h differed more among days of period 5 than at 13:00 or 17:00h, with values increasing from day 1-3 and thereafter generally declining from 118 to 37 breaths/min on day 7. Rectal temperature for KAT was lower than for goats early in period 5 but similar among animal types on days 6 and 7. In conclusion, a HLI in the range of 95/80.75 and 100/85 seems appropriate, periods longer than 1 wk appear necessary for full adaptation, and measures should occur during both night and day. (C) 2016 Elsevier B.V. All rights reserved.

Thirty-seven Dorper, 35 Katahdin, and 31 St. Croix ewes (57, 58, and 44 kg [SEM 2.2]) from 45 commercial farms in the Midwest (MW), Northwest (NW), Southeast (SE), and central Texas (TX), between 2.2 and 3.4 yr of age, were used to evaluate responses to high heat load index (HLI) conditions. There were 4 sequential 2-wk periods with target HLI during day/nighttime of 70/70, 85/70, 90/77, and 95/81. A 15% CP and 50% concentrate pelleted diet was fed at 120% of the ME requirement for maintenance, and water was offered free choice. Body weight was measured 3 times each week, and blood was sampled at 1300 h on the last day of each period. There was an interaction (P < 0.001) between period and week within period in BW, with slightly greater values in wk 2 vs. 1 of periods 3 and 4 and a greater difference between period 1 and 4 values in wk 2 than 1 (53.1, 54.1, 54.9, and 55.4 kg in wk 1, and 53.0, 54.2, 55.4, and 56.1 kg in wk 2 in periods 1, 2, 3, and 4, respectively [SEM 0.85]). There was an interaction (P = 0.037) in DMI (g/kg BW0.75) among region, period, and week, with values generally similar between weeks in periods 1 and 2 relative to those in periods 3 and 4 (51.0, 52.4, 51.0, and 51.2 in period 3 and wk 1; 49.5, 52.1, 50.8, and 51.6 in period 3 and wk 2; 49.6, 52.1, 50.6, and 49.4 in period 4 and wk 1; and 48.9, 52.0, 49.7, and 46.3 in period 4 and wk 2 for MW, NW, SE, and TX, respectively [SEM 1.09]). Neither blood glucose nor lactate concentration was affected by breed (P > 0.05), but there were breed differences (P < 0.02) in serum concentrations of creatinine (0.91, 0.81, and 0.77 mg/dL [SEM 0.023]), total protein (6.13, 6.42, and 6.81 g/dL [SEM 0.156]), and urea N (17.4, 18.0, and 20.0 mg/dL [SEM 0.54] for Dorper, Katahdin, and St. Croix, respectively). In conclusion, some blood constituent levels suggest breed differences in resilience to high HLI. Differences among periods and weeks in BW presumably relate to increased water consumption with high HLI. The interaction in DMI may reflect differences among regions in rate of adaptation to high HLI and the contribution of decreased feed intake to coping with high HLI.

Boer goats (7/8 and 1/8 Spanish breed) were used to characterize effects of gender and age on the ME requirement for maintenance (MEm). There were eight animals of each gender, doelings, intact males, and wethers castrated at 2mo of age. Kids were weaned at 3.7mo and thereafter consumed a 50% concentrate pelleted diet ad libitum while in group pens at most times. Measurement periods consisted of three segments of 12, 10, and 4 days with consumption ad libitum and near MEm and while fasting, respectively. Maintenance segment measures began at 4.9, 7.8, 11.7, and 14.8 mo of age in periods 1, 2, 3, and 4, respectively. Feed intake data, feces and urine collections, and a calorimetry system were used to determine ME intake and heat energy (HE). The MEm estimate was based on fasting HE and the slope (km) of the regression of recovered energy (RE) against ME intake with intake near MEm and while fasting, and kg was RE with ad libitum intake relative to ME intake above MEm. BW (kg) during the maintenance segment was 20.6, 30.8, 46.5, and 57.1 for doelings, 25.9, 40.1, 67.3, and 76.9 for males, and 23.1, 35.1, 53.9, and 65.0 for wethers in periods 1, 2, 3, and 4, respectively (SE=1.85). km was similar among genders and periods (P>0.05%; 70.2%, 69.5%, and 69.7% for doelings, males, and wethers, respectively; SE=1.25). Fasting HE and MEm were affected by gender×period interactions (P<0.001). Fasting HE (kJ/kg BW0.75) was 277, 272, 281, and 281 for doelings, 288, 327, 334, and 398 for males, and 274, 303, 274, and 305 for wethers (SE=10.1); MEm (kJ/kg BW0.75) was 382, 390, 399, and 420 for doelings, 412, 469, 492, and 569 for males, and 384, 417, 426, and 439 for wethers in periods 1, 2, 3, and 4, respectively (SE=14.2). kg tended (P=0.067) to vary among genders (61.5%, 48.1%, and 52.7% for doelings, males, and wethers, respectively; SE=3.91). In conclusion, MEm was not greatly different between doelings and wethers and increased for both as the study progressed, whereas that for males was greater, with the difference increasing considerably as age rose.

Twenty-eight Alpine goats were used to evaluate the effects of different pasture access regimes on lactation performance, grazing behavior, and energy utilization in a 16-wk experiment with four 4-wk periods beginning at 26 +/- 2.5 days in milk. Treatments were access to grass and (or) legume pasture continually other than during milking in the morning and afternoon (CG); from the time leaf surfaces were dry (measured by leaf wetness sensors) until afternoon milking and thereafter to sunset (ND-D); from the time leaf surfaces were dry until afternoon milking (ND-M); and between morning and afternoon milking (SET). The CG, ND-M, and SET goats were supplemented with approximately 1.5% body weight (BW; dry matter basis) of concentrate immediately following the afternoon milking and ND-D goats were supplemented at sunset. Organic matter digestibility, average daily gain, fecal egg count, and FAMACHA((c)) score were not affected by treatment (P > 0.05). Milk concentrations of protein, fat, and lactose and milk energy yield (5.41, 5.06, 5.34, and 5.55 MJ/day for CG, ND-D, ND-M, and SET, respectively; SEM = 0.340) were similar among treatments (P > 0.05). Treatment affected (P < 0.05) time spent grazing (7.43, 6.93, 5.86, and 6.18 h for CG, ND-D, ND-M, and SET, respectively; SEM = 0.351). Intake of metabolizable energy (ME) was similar among treatments (P > 0.05; 1111, 1010, 1043, and 874 kJ/kg BW0.75; SEM = 89.1), daily heat energy was greatest among treatments for CG (P < 0.05) (745, 684, 631, and 667 kJ/kg BW0.75; SEM = 17.9), and milk energy as a percentage of ME intake was greatest (P < 0.05) for SET (30.2, 28.3, 27.9, and 36.3% for CG, ND-D, ND-M, and SET, respectively; SEM = 1.52). In conclusion, there appeared potential to improve efficiency of milk production by pasture access between morning and afternoon milking compared with continuous grazing and there were no clear benefits from delaying pasture access until leaf surfaces were dry.

An in vivo fecal egg count reduction (FECR) test was conducted on 5 farms in the southcentral United States participating in an animal resistance selection project to assess internal parasite resistance to anthelmintics. Seventy-six Kiko does on farm G1, 54 Spanish does (G2), 37 Katahdin sheep (S1), 61 Dorper ewes (S2), and 80 St. Croix sheep (S3) were randomly allocated within farm to control and 3 classes of anthelmintics. After determining initial fecal egg count, recommended doses of anthelmintics were given and fecal egg count was assessed 7 to 8 d later. Resistance to eprinomectin was detected on all farms, with FECR <63%. There was no levamisole resistance on sheep farms (FECR >95%). There was resistance to albendazole on 4 farms (FECR <95%). An egg hatch test was conducted to evaluate resistance to albendazole using composite fecal samples from untreated animals of G1, S1, S2, and S3 farms as well as control eggs from susceptible larvae. Final concentrations of albendazole were 0.00005, 0.0005, 0.005, 0.05, 0.5, and 2.0 μg/mL. After 48 h of incubation at 25°C, numbers of unhatched eggs and larvae per well were counted. The hatched percentage of susceptible larvae was 96% in the control wells. Drug concentration affected (P < 0.01) the percentage of unhatched eggs for S2 and S3, whereas values were similar (P > 0.10) for G1 and S1. In conclusion, resistance to common anthelmintics varied considerably among farms and products, suggesting a need for such testing rather than general treatment recommendations.