「Horse with each foot spread」refers to the cloven hooves of a CAMEL, an animal that is used much as is a horse in some sandy areas of the world. A large animal used as a beast of burden,「horse with feet that spread」is a CAMEL. An anatomical area that is regularly mounted by masturbating stallions, one that「spreads with head in crotch, orifice within」a CAMEL TOE.
「Ten adult camels were developed habit of sand masturbation and under xylazine and ketamine anaesthesia purse string suture at preputial orifice was applied leaving enough space for urination. It was found an effective and complication free prophylactic way to control sand masturbation in adult male racing camels during racing season. This technique was tried on over 50 adult male racing camels during last 3 years and it prevented sand masturbation.」
[ https://www.researchgate.net/publication/292668103_Surgical_technique_to_control_sand_masturbation_in_male_racing_camels 2020-03-09 ]
The「white skin with a black mane」bit refers to the delicate zone with surrounding pubic hairs, also referred to today colloquially as THE CAMEL TOE, although「regularly masturbating into a spread foot orifice」back in the time of dynastic China would have had a more literal meaning, that of using the no-longer-integrated foot of a service provider for autoerotic pleasures:
「Qing Dynasty sex manuals listed 48 different ways of playing with women's [no-longer-integrated] bound feet」(after removing the binding cloths, of course)
[ https://en.wikipedia.org/wiki/Foot_binding 2012-12-17 ]
The literal「orifice in spread feet of a horse」(or camel, for that matter) relative to the size of a human penis would likely provide little stimulation,「no sensation, feeling nothing with crotch」and how that relates to the human female camel toe after giving birth (see 同) may also shed some light on why the use of no-longer-integrated feet, with user-controlled pressure settings, became so popular in dynastic China.
Without a doubt, the Irish also have knowledge of their own to pass along in these trying times:「Masturbation will not spread coronavirus, especially if you wash your hands (and any sex toys) with soap and water for at least 20 seconds before and after.」Nonetheless and regrettably, unlike in dynastic China, it must be undertaken alone to truly be a preventative countermeasure but still achieve the desired result with some degree of safety.
[ https://www.sexualwellbeing.ie/sexual-health/sex-and-coronavirus/ 2020-03-31 ]
The Dutch, too have the same solution—it seems masturbation has become mainstream in the media the world over due to the coronavirus (it has always been 'the main stream' in reality, albeit covertly for most folks):
「'Don't have sex with your partner if they have been isolated because of (suspected) coronavirus infection,' the RVIM says. 'Sex with yourself or with others at a distance is possible (think of telling erotic stories, masturbating together).'」
[ https://www.theguardian.com/world/2020/may/15/dutch-official-advice-to-single-people-find-a-sex-buddy-for-lockdown-coronavirus 2020-05-16 ]
Needless to point out perhaps, but Chinese shamans from antiquity hit upon the same solution as a pandemic preventative countermeasure, honed for ultimate client satisfaction by utilizing naked females with no-longer-integrated feet as masturbatory sex buddies available for short-term rental with erotic visualization of live prepubescent female genitalia engaging in autoerotic stimulation herself, as a solution to the same problem facing us now, but in pre-Internet days.

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: camel; white horse with a black mane (archaic)
Japanese EDRDG: white horse
Unihan extended: a white horse with black mane; a camel