Acta Veterinaria Scandinavica 2008, 50:41 http://www.actavetscand.com/content/50/1/41 Table 2: Normal sperm head morphometry of Thai native crossbred (T; T1 – T5) and purebred (F; F1 – Standardbred; F2 – Warmblood; F3 and F4 – Thoroughbred) stallions (mean ± SE) Stallion Length (μm) Width (μm) Elongation (%) Perimeter (μm) Area (μm2) Ellipticity 5.94 ± 0.08 5 5.70/6.20 2.89 ± 0.01 6.5 2.80/3.10 0.35 ± 0.001 14.88 ± 0.02 13.90 ± 0.04 2.06 ± 0.004 0.79 ± 0.001 1.63 ± 0.002 0.97 ± 0.001 8.8 4 8.5 6.8 3.4 4.7 3.5 0.33/0.36 14.50/15.20 13.10/14.70 1.97/2.14 0.77/0.81 1.58/1.68 0.95/0.99 Significant differences (P < 0.05) within T or F are indicated by different letters (a, b, c, d). Significant differences (P < 0.05) between T and F are indicated by * in superscript The values showing this property were, respectively, length (5.94 μm, 5.77 μm, 5.67 μm); width (2.89 μm, 2.89 μm, 2.85 μm); perimeter (14.88 μm, 14.59 μm, 15.00 μm) and area (13.90 μm2, 12.66 μm2, 13.42 μm2). Nevertheless, some parameters in our study were lower than those for certain unclassified breeds of stallions in a different research trial [41], which reported values as fol- lows: length 6.01 μm, width 2.97 μm, perimeter 15.64 μm and area 13.48 μm2. Within-animal group percentage CVs for all head mor- phometric parameters were low for sperm in both the T group (from 2.6 for shape factor 1 to 7.5 for elongation) and in the F group (from 2.9 for shape factor 1 to 8.1 for elongation). This reflected a homogeneous sperm popula- tion within individuals. These results were consistent with those studies which examined unclassified breeds of stal- lion (from 5.8 for length and perimeter to 8.8 for area) [41], ram (from 4.36 for length to 7.33 for shape factor 1) Table 3: Within-animal and between-animal CV of normal sperm head morphometry in Thai native crossbred (T) and purebred (F) stallions Length Width Elongation Perimeter Ellipticity T1 T2 T3 T4 T5 F1 F2 F3 F4 % CV (T) Percentile 25/75 Mean F % CV (F) Percentile 25/75 Stallion T F Within-animal CV Between-animal CV Within-animal CV Between-animal CV 4.0 28.9 4.8 5.3 5.4 17.6 5.8 11.9 7.5 11.2 8.1 17.6 2.9 19.2 3.6 1.6 15.88 ± 0.09a,b 16.23 ± 0.09b 16.67 ± 0.08c 15.90 ± 0.09a,b 15.77 ± 0.07a 14.83 ± 0.07a 13.97 ± 0.05b 14.41 ± 0.09c 13.20 ± 0.05d 2.09 ± 0.01a 1.90 ± 0.01b 1.98 ± 0.01c 1.99 ± 0.01c 2.02 ± 0.01c 2.01 ± 0.005* 6.5 1.94/2.10 1.99 ± 0.07a 2.06 ± 0.01b 2.11 ± 0.01c 2.09 ± 0.01c Area 5.9 19.8 7.2 4.0 6.24 ± 0.03a 2.99 ± 0.02a 6.07 ± 0.02b 3.19 ± 0.02b 6.33 ± 0.02c 3.19 ± 0.01b 6.18 ± 0.02ab 3.11 ± 0.02c 6.18 ± 0.02a 3.08 ± 0.01c 4.5 6.00/6.40 6.2 2.90/3.20 5.94 ± 0.02a 2.99 ± 0.01a 5.98 ± 0.01a 2.92 ± 0.01b 6.15 ± 0.03b 2.92 ± 0.01b 5.85 ± 0.01c 2.80 ± 0.01c 0.35 ± 0.002a 0.31 ± 0.003b 0.33 ± 0.002c 0.33 ± 0.003c 0.33 ± 0.002c 0.34 ± 0.001* 8.5 0.31/0.35 0.33 ± 0.002a 0.34 ± 0.002b 0.36 ± 0.002c 0.35 ± 0.001c 15.98 ± 0.04a 15.73 ± 0.04b 16.10 ± 0.04a 15.76 ± 0.04b 15.71 ± 0.03b 15.14 ± 0.03a 14.89 ± 0.03b 15.24 ± 0.05a 14.55 ± 0.03c Mean T 6.22 ± 0.01* 3.09 ± 0.0* 15.88 ± 0.02* 3.3 15.60/16.20 16.09 ± 0.03* 6.6 15.40/16.80 Sf1 0.78 ± 0.002a 0.82 ± 0.002b 0.81 ± 0.001c 0.80 ± 0.002c 0.80 ± 0.002c 0.80 ± 0.001* 3.3 0.79/0.82 0.81 ± 0.001a 0.79 ± 0.002b 0.78 ± 0.002c 0.79 ± 0.001c Sf2 1.63 ± 0.006a 1.57 ± 0.007b 1.60 ± 0.005c 1.60 ± 0.008b,c 1.61 ± 0.005a,c 1.61 ± 0.003* 4.6 1.56/1.66 1.62 ± 0.004a 1.62 ± 0.004a 1.64 ± 0.006b 1.64 ± 0.004b Sf3 0.92 ± 0.004a 0.94 ± 0.003b 0.95 ± 0.002b 0.95 ± 0.004b 0.95 ± 0.002b 0.94 ± 0.002* 4.2 0.92/0.97 0.94 ± 0.002a 0.98 ± 0.001b 0.98 ± 0.003bc 0.98 ± 0.002c 5.6 13.9 6.3 16.0 Sf1 2.6 25.8 2.9 26.1 Sf2 4.3 13.2 4.5 14.2 Sf3 3.8 32.0 3.2 7.2 Page 7 of 9 (page number not for citation purposes)