Search

This study evaluated beef heifers selected for high or low digestible fiber intake (DFI) and investigated its relationship with methane production, residual feed intake (RFI), and total tract digestibility. Sixteen recently weaned black Angus beef heifers (n = 8/treatment) were selected from a group 64 heifers (224 ± 17.2 kg) fed a high forage-based diet [70% barley silage:30% pelleted concentrate (DM basis)]. The 64 heifers were fed in 6 outdoor pens equipped with GrowSafe bunks to monitor feed intake for 60 d (14 d adaptation + 46 d for data collection). Individual fecal samples and BW, and feed samples were taken once weekly. Fecal samples were pooled by animal. Feed and fecal samples were analyzed for dry matter (DM), neutral detergent fibre (NDF), and undigested neutral detergent fiber (uNDF) content. The internal marker uNDF was used to estimate total tract diet DM and NDF digestibility. The 8 heifers with the greatest and the 8 with the least digestible NDF intake (g/kg BW0.75) were selected and used for methane measurements using the GreenFeed system (42 d) and in a total-tract digestibility trial with total fecal and urine collection using the same high forage based diet. Results from the GrowSafe selection trial indicated no differences between the average BW of low and high DFI heifers (264 vs. 274 kg, P = 0.20). Heifers selected for high DFI had greater (P < 0.01) DM and NDF intake (kg/d or % of BW), and digestibility (49.6 vs. 42.1% NDF digestibility). The heifer groups differed in RFI (P < 0.01), with high DFI categorized as inefficient (+0.84 RFI) and low DFI as efficient (-0.34 RFI). No differences in ADG were observed between low and high DFI heifers during this short 46 d study period (0.614 vs 0.773, P = 0.16). High DFI heifers had lower methane production than low DFI heifers (15.9 vs. 19.0 g/kg of DMI, P = 0.02). The results of the total-tract digestibility trial showed that the high DFI heifers had a greater DMI compared with the low DFI heifers (10.9 vs. 10.2 kg/d; P = 0.04). The DMI intake was not different between groups when expressed as a % of BW (2.06 vs 2.04, P = 0.65). There was also no difference observed for DM digestibility (73.0 vs 73.1%) between the two groups. It is important to note that in the digestibility study, the DMI was less than in the GrowSafe selection trial (2.5 vs 3.2% BW) and this may have influenced results. Heifers with high DFI were heavier than low DFI heifers (533 vs. 505, P = 0.02) during the digestibility trial. Results suggest that selecting heifers for high DFI may increase growth rate and reduce methane production. [ABSTRACT FROM AUTHOR]

During transient periods of feed restriction (FR), ruminal ammonia-N (NH3-N) concentrations and fluid volume may parallel the reduction in feed and water intake. However, changes in ruminal digesta characteristics and NH3-N during FR have not been characterized. Thus, the objective was to determine how FR duration impacts ruminal digesta weight and the liquid and solid fractions, and ruminal NH3-N concentration. Lambs (n = 9 wethers and 12 rams, stratified by BW and castration status) were fed ad libitum (AL, n = 7) or subjected to 5-d (FR5, n = 7) or 10-d of FR (FR10, n = 7) at 30% of AL intake. Lambs were killed 4 h post-feeding to excise the gastrointestinal tract and ruminal digesta was weighed. Sub-samples of digesta were collected for separation into solid and liquid fractions using a winepress, used for DM determination, and another was strained and preserved with sulfuric acid to analyze ruminal NH3-N concentration. Data were analyzed with PROC GLIMMIX (SAS 9.4) with the fixed effect of treatment and random effects of lamb specified to the R-sided matrix. Linear regression (PROC REG) was used to evaluate the relationship between ruminal NH3-N concentration and quantity relative to ruminal fluid weight and PROC CORR was used to generate Pearson correlation coefficients. The ruminal digesta weight did not differ (P = 0.97) among treatments but AL ruminal digesta was drier (P < 0.01) than FR5 and FR10 digesta (40.2% decrease in DM% relative to AL). As such, FR5 and FR10 had 0.7 ± 0.16 kg less (P = 0.01) ruminal solids than AL while they tended to have more (P = 0.09) ruminal fluid. Ruminal NH3-N concentration was greater (P < 0.01) for FR5 and FR10 compared with AL (2.4 and 2.0 vs. 0.4 ± 0.52 mg/dL, respectively). The quantity of ruminal NH3-N (mg) followed the same pattern with FR5 and FR10 having, on average, 51.5 ± 18.39 mg NH3-N more (P < 0.01) in their ruminal fluid than AL. The quantity of ruminal NH3-N was strongly correlated (ρ = 0.87, P < 0.01) to the total ruminal fluid such that 75% of the variance was explained by the relationship. The strength of the correlation (ρ = 0.81, R² = 0.66, P < 0.01) between ruminal NH3-N concentration and total ruminal fluid was slightly lesser, but the two parameters were still strongly associated. From these data, we surmise that FR is associated with a reduction in ruminal DM content and may increase ruminal liquid that corresponds to increased ruminal NH3-N, independent of the duration of exposure. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate effects of increasing hybrid rye as a replacement for barley grain on feed intake, ruminal fermentation, and site of nutrient digestion in finishing cattle. Eight ruminally and duodenally cannulated Hereford-cross heifers (starting body weight = 514 ± 25.3 kg) were used in a replicated 4×4 Latin square design with 21-d periods including 15 d of dietary adaptation and 6 d of sample collection. Dietary treatments included a control diet with 10.0% hay, 85.2% barley grain, and 4.8% of a vitamin and mineral supplement on a dry matter (DM) basis. Hybrid rye grain replaced 33, 67, or 100% of the barley grain. Both cereal grains were dry rolled to 80% processing index. Feed, refusals, ruminal fluid, duodenal digesta, and fecal samples were collected. Data were analyzed using the MIXED procedure of SAS 9.4 (SAS Inst. Inc., Cary, NC). Increasing hybrid rye inclusion tended (P = 0.052) to linearly decrease DM intake. Additionally, increasing hybrid rye grain linearly decreased mean and minimum ruminal pH (P < 0.01) and increased the duration (P < 0.01) and area (P = 0.01) that pH was less than 5.5. There was no effect of hybrid rye inclusion on total short chain fatty acid, lactic acid concentrations, or osmolality. Likewise, the molar proportion of acetate and butyrate were not affected by hybrid rye inclusion. Propionate tended to linearly increase with increasing hybrid rye inclusion (P = 0.08). Increasing hybrid rye linearly increased NH3-N concentration (P = 0.03). Ruminal organic matter (OM) digestibility tended to linearly increase (P = 0.08) and ash-free neutral detergent fiber (aNDFom) digestibility linearly increased (P < 0.01) when increasing hybrid rye. There was no effect on ruminal starch digestibility (71.1 ± 5.12%). Intestinal digestibility of CP linearly decreased (P = 0.050), but there were no effects for other nutrients. Increasing hybrid rye linearly increased apparent total-tract DM, OM, and aNDFom digestibility (P < 0.05) but did not affect starch digestibility (97.4 ± 0.42%). Increasing the inclusion rate of hybrid rye grain at the expense of barley grain in finishing diets may decrease DMI and increase risk for ruminal acidosis; however, hybrid rye inclusion did not influence the site or extent of starch digestion and increased total tract digestibility of DM, OM, and aNDFom. [ABSTRACT FROM AUTHOR]

Cattle consuming increased concentrations of sulfur (S) are at an increased risk for depletion of copper (Cu) and or S-induced polioencephalomalacia and there are limited mitigation strategies to alleviate risk for cattle consuming high sulfate water. This study evaluated the effects of feeding growing beef heifers bismuth subsalicylate (BSS; 0.0 vs. 0.4% DM basis) when provided water with a low (LS; 346 ± 13) or high (HS; 4,778 ± 263 mg/L) sulfate concentration on dry matter intake (DMI), water intake, ruminal hydrogen sulfide (H2S) concentration, and trace mineral status. Twenty-four beef heifers (221 ± 41 kg) were stratified based on initial liver copper concentrations collected 13 d before the start of the study, into a completely randomized block design using a high forage diet fed for 98 d. Feed and water intake (weekly), ruminal H2S concentration (d 42 and 91), and liver (pre-study and d 91) and serum trace mineral concentrations (d 1, 28, 56, and 91) were evaluated. Initial liver trace-mineral concentration was used as a covariate in the statistical model. Water intake tended to be reduced with the inclusion of BSS (P = 0.10) but was not affected by water sulfate (P = 0.40). Water sulfate and BSS did not affect DMI (P ≥ 0.89), but total S intake increased (P < 0.01) from LS to HS (17.6 to 51.0 g/d) resulting in diets that contained 0.28 and 0.78% S (DM basis). Heifers consuming HS had 1.58 μg/mL more (P < 0.01) ruminal H2S than LS. The inclusion of BSS reduced (P = 0.04) ruminal H2S concentration by 46%. Regardless of water sulfate concentration, heifers fed BSS had lesser liver Cu (average of 4.08 mg/kg) than heifers not provided BSS, and when not provided BSS, HS had lesser Cu than LS (42.2 vs. 58.3; sulfate × BSS, P = 0.02). Serum concentration of Cu did not differ over time for heifers not provided BSS; whereas heifers provided BSS had less serum Cu on d 91 than d 28 and 55 (BSS × time, P < 0.01). The liver concentration of selenium (Se) was reduced (P < 0.01) with BSS inclusion. The Se concentration in serum was not affected by sulfate, BSS, or time (P ≥ 0.16). Bismuth subsalicylate reduces ruminal H2S concentration, but depletes liver Cu and Se. Moreover, sulfate concentration in water does not appear to affect DMI or water intake but reduces liver Cu concentration. [ABSTRACT FROM AUTHOR]

This study aimed to determine the effects of feeding ground whole flaxseed and two types of mechanically extracted flaxseed meals on dry matter intake (DMI), milk production and composition, ruminal fermentation characteristics, and total-tract nutrient digestibility in dairy cows. Twelve multiparous Holstein cows [122 ± 20 days in milk (DIM) at the start of the study] were used in a replicated 4 × 4 Latin square design with 4 dietary treatments. One square had 4 ruminally cannulated cows that were used to determine dietary effects on ruminal fermentation characteristics and total tract nutrient digestibility. The 4 dietary treatments tested were a barley silage-based diet with canola meal (CM; 21.1% of diet DM) as the main protein source (designated CON), and diets containing ground whole flaxseed (designated GWF; 4.92% of diet DM), defatted flaxseed meal (designated DFM; 19.7% of diet DM), or organic flaxseed meal (designated OFM; 20.2% of diet DM) as partial replacements for CM. The crude fat contents of CM, GWF, DFM, and OFM were 3.20, 37.7, 9.9, and 12.9% (DM basis), respectively, and experimental diets were balanced for crude fat content (4.51%; DM basis). Experimental periods consisted of 18 d of dietary adaptation and 10 d of data and sample collection. Orthogonal contrasts were used to test for the following treatment differences: CON vs. GWF; CON vs. [DFM + OFM]; and GWF vs. [DFM + OFM]. Dry matter intake was lower (P < 0.01) for cows fed CON compared with those fed GWF and [DFM + OFM]. Milk yield tended to be greater (P = 0.06) for cows fed CON compared with those fed GWF (P = 0.06) and [DFM + OFM] (P = 0.06). Milk fat content and yield were unaffected by diet; however, milk protein content was reduced for cows fed CON compared with those fed GWF (P = 0.001) and [DFM + OFM] (P < 0.001). Milk urea-N (MUN) concentration was greater (P = 0.001) in cows fed CON compared with those GWF and [DFM + OFM]. Also, MUN concentration was decreased for cows fed GWF compared with those fed [DFM + OFM]. Ruminal NH3-N concentration was less (P = 0.04) in cows fed CON than those fed GWF and [DFM + OFM], but ruminal pH and short-chain fatty acid concentrations were unaffected by diet. Fecal N excretion (g/d) was greater (P < 0.01) for cows fed CON compared with those fed GWF and [DFM + OFM] and, therefore, total-tract CP digestibility was reduced (P < 0.001) in cows fed CON compared with those fed GWF and [DFM + OFM]. In conclusion, partial replacement of CM with GWF or [DFM + OFM] increased DMI; however, it tended to reduce milk yield. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of providing inorganic, chelated, and inorganic plus injectable trace mineral supplementation strategies with or without the inclusion of bismuth subsalicylate (BSS) on dry matter intake (DMI), water intake, ruminal hydrogen sulfide (H2S) concentration, and trace mineral status of growing beef heifers provided high sulfate (5,055 ± 228 mg/L) water. This study consisted of an 84-d feeding period with a 2×2 + 1 factorial treatment arrangement conducted using 2 blocks. Beef heifers (n = 15/block; 367 ± 33 kg BW) in each block were stratified according to their initial liver copper concentration. Mineral treatments included inorganic [added CuSO4 (7.76 mg/kg), ZnSO4 (22.92 mg/kg), MnSO4 (15.28 mg/kg)], chelated (100% of the Cu-methionine (7.68 mg/kg), Zn-methionine (22.89 mg/kg), and Mn-methionine (15.27 mg/kg), and injectable trace mineral (15 mg/mL Cu, 10 mg/mL Mn, 60 mg/mL Zn) provided in combination with the inorganic mineral treatment. The BSS treatments were 0.0 (CON) or 0.2% (BSS) on a DM basis. Feed and water intake (weekly), ruminal H2S concentration (d 42 and 84), and liver (pre-study, d 42 and 84) and serum trace mineral concentrations (d 1, 28, 56, and 84) were evaluated. Initial liver trace mineral concentration was used as a covariate. Dry matter intake tended to be greater (mineral × BSS, P = 0.05) for heifers provided chelated minerals and fed CON, compared with BSS, and tended to be less for heifers fed inorganic and CON than BSS. Heifers fed chelated minerals drank 6.1 L/d more (P < 0.05) water than those provided inorganic minerals. Injectable tracemineral provision did not affect DMI or water intake. Ruminal H2S was not affected by mineral type or BSS (P = 0.33). The inclusion of BSS reduced (P < 0.01) liver Cu concentration from 60.5 to 31.3 ppm. Heifers provided the injectable minerals had greater (P < 0.01) liver Cu concentration than the inorganic without BSS treatment. Serum copper was not affected by BSS or mineral treatment (P = 0.44). The liver concentration of Se was reduced (P < 0.01) by the inclusion of BSS. The serum Se concentration was not affected by mineral type, BSS, time, or any two- or three-way interactions (P = 0.24). Bismuth subsalicylate did not affect ruminal H2S, and negatively affected liver Cu concentration. The use of organic trace mineral supplementation strategies did not affect the trace mineral status of beef heifers drinking high sulfate water, but use of an injectable trace mineral supplement increased liver Cu. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the effect of 5 and 10 d low feed intake (LF) on the ruminant gastrointestinal tract (GIT). Twelve rams and nine wethers were used in a randomized complete block design where they were blocked by castration status and BW. After 5 d of ad libitum feeding, lambs were either exposed to 0 (CON; 100% DMI; n = 7), 5 (LF5; 30% DMI; n = 7), or 10 d (LF10; 30% DMI; n = 7) of LF. At the end of the study, lambs were euthanized, the GIT was removed to determine the digesta and tissue weights by region and the weights of the liver, spleen, and kidneys were recorded. There were no castration × treatment interactions (P = 0.32). Initial (P = 0.97) and final (P = 0.19) BW did not differ by treatment. The weight of the reticulo-ruminal tissue tended to be less (P = 0.06) for LF10 than CON, with LF5 being intermediate but not different. Ruminal digesta weight was not affected (P = 0.98). Omasal tissue weight did not differ among treatments (P = 0.24), but digesta weight tended (P = 0.07) to be greater for CON compared with LF10 and LF5. Abomasal tissue weight was reduced for LF10 (P = 0.04), with LF5 being intermediate but not different. Abomasal digesta weight was less for LF5 and LF10 than CON (P = 0.04). The weight of the duodenum tended (P = 0.08) to be greater for CON than LF10 and LF5, but digesta weight was not affected (P = 0.16). For the jejunum, tissue and digesta weight tended (P = 0.07) to be greater for CON than LF10, with LF5 being intermediate. The weight of the ileum tended to be the greatest for CON, intermediate for LF5, and the least for LF10 (P = 0.10), but digesta weight was not affected (P = 0.81). Cecal tissue weight was not affected by treatment (P = 0.89); whereas digesta weight was the greatest (P = 0.03) for LF10, the least for CON, and intermediate but not different for LF5. In contrast, colonic tissue weight was less for LF10 relative to LF5 and CON (P = 0.01) and digesta weight tended (P = 0.05) to be greater for CON than LF5 and LF10. Liver weight was reduced (P < 0.01) for both LF5 and LF10 relative to CON, but kidney and spleen weights were not affected (P = 0.33). This study indicates that exposing ruminants to LF rapidly reduces the weights for regions of the GIT and liver. These changes likely implicate a reduced absorptive capacity of the GIT and a lesser metabolic capacity of the liver. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate effects of increasing hybrid rye as a replacement for barley grain on feed intake, growth performance, and carcass characteristics for growing and finishing cattle. Commercial steers (n = 360) with an initial body weight (BW) of 348 ± 6.6 kg were stratified by BW and randomly assigned to 1 of 24 pens (15 steers/pen) for growing (n = 8; 65 d) phase and re-randomized for the finishing (n = 6; 118 d) phase. The control diet (BCON) for the growing phase included 60.2% barley grain, 28.0% barley silage, 7.0% corn silage, 3.4% oat hulls, with the remainder as mineral, vitamins, and urea. Hybrid rye was then included by replacing 50 or 100% of the barley grain (DM basis). Treatments for the finishing phase included a control containing 10% hay, 85.2% barley grain, with the remainder coming from mineral and vitamins (FCON). Hybrid rye grain was included by replacing 33 (33R), 67 (67R), and 100% (100R) of the barley grain (DM basis). Data were analyzed using the MIXED procedure for each phase independently with carcass data analyzed using the GLIMMIX procedure of SAS (SAS version 9.4; SAS Institute, Inc. Cary, NC). There was no effect of hybrid rye inclusion on DMI or G:F during the growing phase, but ADG increased quadratically (P = 0.04) with 50% rye having the greatest value. During finishing, DMI decreased linearly as hybrid rye inclusion increased (P = 0.03). Average daily gain was quadratically affected (P = 0.03) with an initial increase from FCON to 33% rye followed by a decrease with increasing rye grain inclusion, but G:F was not affected (0.148 kg BW/kg DMI). There was no effect of hybrid rye inclusion on hot carcass weight, dressing percentage, back-fat thickness, ribeye area, marbling score, and yield score. Increasing the inclusion of hybrid rye quadratically (P < 0.01) increased the proportion of severe liver abscesses with an average of 34.6% severely abscessed livers when hybrid rye grain was included compared with 11.1% for FCON. Partial replacement of barley grain with hybrid rye may improve ADG without affecting DMI or G:F during the growing phase. However, replacing barley grain in finishing diets with hybrid rye decreases DMI, increases risk for severe liver abscesses, but does not affect feed conversion suggesting hybrid rye could replace up to 33% of the barley grain. [ABSTRACT FROM AUTHOR]

Undigestible neutral detergent fiber (uNDF) is a non-nutritive component of the diet representing the portion of neutral detergent fiber (NDF) that is not digested. The uNDF amount affects ruminal fill, passage rate, diet digestibility, and cattle performance. Therefore, a meta-analysis was conducted to evaluate the potential use of dietary uNDF to predict finishing feedlot cattle performance and carcass characteristics. A specific search string was used to obtain 22 eligible experiments forming a database in which models were developed. The search string used was as follows "(feedlot OR beef) AND (forage OR roughage OR iNDF OR uNDF) AND (dressing percentage OR dressing %) AND (liver abscess) AND (feed efficiency OR GF OR FG) AND (DMI) AND (ADG) AND (rumen pH OR ruminal pH OR reticulo-ruminal pH)". Due to the lack of measurement and reporting of uNDF in the literature, the dietary uNDF of each treatment included in the meta-analysis was estimated using data from the Cumberland Valley Analytical Services database. A comparison of uNDF and NDF as predictor variables of performance was also assessed. Models were developed using a mixed model approach, where experiment was modelled as a random effect. Models with dry matter intake (DMI), implant or tylosin as driving variables alongside uNDF concentration or uNDF intake lowered the root mean square prediction error (RMSPE) and improved the concordance correlation coefficient (CCC). The comparison of uNDF and NDF as predictors of outcomes demonstrated more accurate predictions with uNDF as the driving variable. Developed models from this meta-analysis can reasonably predict average daily gain, DMI, dressing percentage, final body weight, dressing percentage, feed efficiency, and hot carcass weight in healthy Bos taurus feedlot cattle. Results suggest there is still more to be discovered about uNDF and its impact in diets for finishing cattle and that uNDF may be a more informative metric than NDF alone. Further research to improve the characterization of forage in the diets of beef cattle is recommended. [ABSTRACT FROM AUTHOR]

The objectives of this study were to examine the impacts of active live yeast (Saccharomyces cerevisiae) as a dietary feed additive on dry matter intake, feed sorting, gut permeability, ruminal pH and volatile fatty acids (VFA) concentration, as well as fecal pH and VFA concentration in cattle fed a highgrain finishing diet and subjected to a ruminal acidotic challenge. Fifteen Hereford X Charolais heifers were blocked by BW into three blocks. Heifers were randomly assigned within block to one of two dietary treatments; CON (no additive), or YST (3 g· animal-1· day-1 of active live S. cerevisiae) added to a steam-flaked corn diet (83% steam-flaked corn, 8% wheat straw, 5% soybean meal protein mix, 4% vitamin and minerals on a DM basis). The experimental timeline was as follows: 30 d adaptation (ADPT), 5 d baseline (BASE), 5 d ruminal acidosis challenge (CHAL), and three subsequent 5 d recovery phases (REC1, REC2, and REC3). On day 2 of each phase and days 2 and 4 of CHAL, 179 mM Cr-EDTA and 360 mM Co-EDTA were infused into the omasum and rumen, respectively, as gut permeability markers. Within each phase, in-dwelling pH probes were used to capture reticulo-ruminal pH every 5min for 96 consecutive hours, rumen fluid and fecal grab samples were collected once for every 3 h in a 24 h period, and blood was collected at 2, 4, 12, and 24 h after each Co and Cr infusion. Dry matter intake and feed sorting were measured daily for each animal. Statistical analysis was conducted using PROC GLIMMIX in SAS as a randomized complete block design with block, treatment, and phase as fixed effects and animal as a random effect. Ruminal acidosis was successfully induced using this method, as suggested by the statistically significant reduction in minimum pH and increase in pH range in the CHAL phase compared with other phases of the experiment (P ≤ 0.02). Recovery from the ruminal acidosis challenge was detected within the REC1 phase when comparing minimum pH (CHAL 5.25 vs. REC1 5.54; P = 0.001). Additionally, the sorting behavior of some particle sizes was significantly impacted by phase (P ≤ 0.01). Overall, the addition of yeast to the diet did not impact feed intake, sorting behavior, spot ruminal and fecal pH, volatile fatty acid concentrations in ruminal fluid or feces, or the uptake of Cr-EDTA and Co-EDTA. These results suggest that adding live S. cerevisiae yeast at this dose in a high-grain finishing diet does not impact feed intake, gut permeability, or the production of VFA when ruminal acidosis is induced. [ABSTRACT FROM AUTHOR]

Efficiency of mature beef cows consuming high-forage diets is not comparable with standard definitions of beef cattle efficiency such as feed conversion or residual feed intake in the feedlot setting. This study aimed to conduct a genome-wide association study (GWAS) to identify regions of the bovine genome associated with efficiency in mature beef cows. Ninetyeight black Angus cows were managed under extensive feeding programs over a two-year period. Using rump fat at calving, calving date, and calf weaning weight as a percentage of the body weight of the dam, a weighted percentile scoring system was used to rank efficiency. Eighty-three of the cows were retained for the GWAS. The 20 most and 20 least efficient cows (HD dataset, n=40) were genotyped with the Illumina BovineHD BeadChip (777,000 SNPs) while the remaining cows were genotyped with the Neogen GGP Bovine 100K chip (LD dataset, n = 43). The LD dataset was imputed to the HD SNP array density using Beagle5.4 (FULL dataset, n = 83). Three separate GWAS were conducted using GAPIT (version3). The first GWAS was performed on the HD dataset using a quantitative phenotype determined by the ranking system. The second GWAS was performed with the HD dataset using a qualitative phenotype (efficient vs non-efficient cows). For the final GWAS, the FULL dataset with ranked phenotypes was used. Five models were evaluated for each GWAS, including the general linear model (GLM), mixed linear model (MLM), multiple loci mixed model (MLMM), fixed and random model circulating probability unification (FarmCPU), and Bayesian-information and linkage-disequilibrium iteratively nested keyway (BLINK). The model that best represented each dataset as determined by quantilequantile plots was used for downstream analysis. Although results of the GWAS were not significant (Bonferroni threshold), associations were identified on BTA10, 16, 17, 25, 27 and 29. Positional candidate genes in the associated regions include: FOXN3, UPB1, SNX29, DDX54, LOC112444612, RITA1, and TACC1. Further functional analyses are required to confirm these findings; however, this work provides a foundation for identifying genes and gene mutations influencing this newly described phenotype. [ABSTRACT FROM AUTHOR]