A donkey or an ox -- the question is still open -- may be at the heart of a controversy surrounding one of China's most treasured national art works.

　　The dilemma is whether repairs made over the centuries to a Northern Song Dynasty masterpiece simply added images that were not there. If so, should those repairs be undone or did they become part of the work?

　　Qingming Shanghe Tu was painted by 12th century imperial court painter Zhang Zeduan during the Northern Song Dynasty (906-1127).

　　Variously translated as Going Upriver for the Qingming Festival or Peace Reigns on the River, the 528.7-centimetre-long silk handscroll in ink and colours depicts a panorama of daily life, business and social interaction in Bianliang, the capital of the Northern Song Dynasty and today's Kaifeng in Henan Province.

　　The United States, France, Britain and Japan each has at least one copy of this Chinese masterpiece, which experts believe are just duplications.

　　Only the Palace Museum in Beijing possesses the original, said Yu Hui, a museum official.

　　But the restoration of a tiny part of the handscroll in 1973 has triggered a heated debate among academics and the public.

　　At the centre of the controversy is a donkey. Or is it an ox?

　　A former Palace Museum copier, Wang Kairu, said the restorations changed the original work.

　　In 1973, a panel of experts at the Palace Museum determined a small part of the painting had been inappropriately mended during the Ming Dynasty (1368-1644).

　　According to Yu, the experts believed the Ming artists had "mistakenly" thought a pole crutch on the painting was the "horn of an ox," whose body was missing. So they pasted on a little piece of silk and painted an "ox" on it.

　　So the Palace Museum experts in 1973 removed that little piece of silk.

　　Over the past few months, however, the now absent piece of silk has fuelled a hot debate.

　　Yu and other experts claim the Ming addition makes the painting difficult to understand and goes against the spirit of the original work.

　　"The decision to remove the tiny silk piece from the painting was made after careful consideration and deliberation, with the whole process being photographed," Xu Zhongling, 67, then deputy director of the museum's calligraphy and painting division, told China Daily yesterday.

　　But Wang Kairu, who has studied Zhang's painting for years and made four copies of the original work in 1997, insisted the small piece of silk on Zhang's original work perfectly fits the scenario of the handscroll, and was likely made with good reason.

　　And that is only the beginning of the debate.

　　To many people's surprise, however, Wang believes that the Ming Dynasty restorers did not paint an ox on their silk patch but a donkey in heat.

　　"A person with knowledge of livestock will see it was a ruttish she-donkey," he said.

　　Putting the animal in the context of the painting, the donkey could be interpreted as moving towards a jackass nearby, scaring an old man who tries to rein it in while warning a child to avoid, Wang said.

　　"The Palace Museum experts seemed to not know the behaviour of animals very well, I know animals well since I grew up and live in the countryside," he said.

　　Ox or donkey, once it had been fixed on the ancient painting by ancient artists, it should not be simply taken away, said both Wang and Feng Jicai, a well known Chinese writer and painter.

　　Removing the patch made that part of the masterpiece more difficult to understand, Wang said.

　　He said the art work should be restored to what it was before 1973, otherwise, people throughout the world will never have a chance to see the "undeleted" painting.

　　But Palace Museum official Yu said removing the tiny part restored the original look of the great work.

　　He said the museum will sponsor an international seminar on the painting next October, when the museum will give a clear explanation of its restoration efforts.