Table 12.
Gestational stages of horses based on physical features of the fetuses
| Horse | Volume of the uterus in L | Width/diameter of the uterus in cm | External features | Crown‐rump‐length in cm | Femur length | Length of metatarsus in mm | Eye length mm (Ultrasonography) | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Reference | Rüsse and Grunert (1993) | Roberts (1986) | Njaa (2012) | Evans and Sack (1973) | Evans and Sack (1973) | Platt (1978) | Njaa (2012) | Habermehl (1975) | Habermehl (1975) | Guffy et al. (1970) | Murase et al. (2014) | Turner et al. (2006) |
| First third of gestation (day 1–day 112) | ||||||||||||
| Day 112 | 15–3.5 (d90) | 12.5–15 (d90) | Mammary nipples and hooves visible (d90) | Tactile hairs on lips; teats well formed. | ~ 20 | n.a. | 10–14 (d90) | 23 (15 weeks) | 17 (15 weeks) | n.a. | ~ 16 | 14 for horse (for pony) |
| Second third of gestation (day 113–day 226) | ||||||||||||
| Day 120 | n.a. | n.a. | External genitalia formed, scrotum empty, ergots and orbital areas prominent | Fine hair on muzzle, chin and around eyes; orbital area prominent; ergot prominent | ~ 25 | n.a. | 15–20 | 41 (20 weeks) | 32 (20 weeks) | n.a. | ~ 17 | 16 (15) |
| Day 210 | 10–15 (d180) | n.a. | Hair on lips, nose eyebrow, eyelids, edge of ear, tip of tail, back and mane | Eyelashes emerged, mane and tail hair present, mane hair ~ 2.5 mm long | ~ 65 | 70 | 55–70 | 89 (29 weeks) | 80 (29 weeks) | n.a. | ~ 28 | 29 (25) |
| Last third of gestation (day 227–day 340) | ||||||||||||
| Day 240 | n.a. | n.a. | Hair on mane and tail, back and distal portion of extremities | Hair appears on poll, pinnae, throat chin and muzzle; mane hair 5 mm long; hair covers distal half of tail | ~ 80 | 83 | 60–80 | n.a. | n.a. | n.a. | ~ 28 | 30 (28) |
| Day 270 | n.a. | n.a. | Short fine hair over entire body | Body covered with fine hair; mane hair 1.5 cm long; short switch on tail. | ~ 100 | 99 | 80–90 | 140 (37 weeks) | 154 (37 weeks) | n.a. | ~ 31 | 30 (30) |
| 330 | 60–90 | n.a. | Complete hair coat, testes descended | n.a. | n.a. | 118 | n.a. | 212 (44 weeks) | 236 (44 weeks) | n.a. | ~ 34 | 37 (d320) (35) |
| Information on source reliability | No source provided | Multiple resources which can mostly not be retrieved | Data from Bergin et al., (1967; 93 specimens); Roberts, (1971) | Data from Bergin et al., (1967; 93 specimens) Ewart, 1897, review of Zietzschmann and Krolling (1955) |
Bergin et al., (1967; 93 specimens) Ewart, 1897, review of Zietzschmann and Krolling, 1955) Numbers extrapolated from graph |
179 aborted thoroughbred foals | n.a. | Data from Habermehl (1975) on 22 horse fetuses | Data from Habermehl (1975) on 22 horse fetuses | 101 American fetuses |
10 thoroughbred mares Numbers extrapolated from graph |
23 ponies (36 pregnancies) Back calc from parturition assuming 340 days and data from Kahn and Leidl (1987 – n = 77) and Turner et al. (2006 – n = 66) on light horses Concluded houses and ponies had diff equations |