Forty years have passed since the giant panda population hit an all-time low, and the global community of panda experts has been tirelessly working towards a singular goal: to cultivate a self-sustaining population that can thrive in the wild, ensuring a secure future for this wild species. However, two significant obstacles have hindered research into allowing these animals to maintain their numbers independently: a lack of collaborative efforts among various institutions and a disregard for the breeding advice of genetic scientists. Particularly in China, the native home of the panda, breeders have often prioritized the quantity of cubs over their quality, with the funding of competing departments being directly tied to the number of cubs they produce.
The Hidden Costs of Human Intervention
A long-standing concern has been the health and behavioral issues that arise in captive pandas due to improper breeding methods. These issues not only complicate the breeding process but also make it more challenging for pandas to adapt to the wild. Our recent publication in Scientific Reports adds to the growing body of evidence that human interference in breeding can be detrimental to the animals.
In China, where the giant panda conservation efforts are most concentrated, it is customary for breeding centers to frequently supplement or even replace mother's milk with artificial formula. This practice, influenced by China's livestock culture, is believed to maximize survival rates and growth speed. However, breeding practices vary in other countries, often depending on their panda loan agreements with the Chinese government. In many cases, the presence of a Chinese caretaker is required, ensuring that the breeding habits of China are followed.
The Colostrum Conundrum: Comparing Panda Milk to Formula
The importance of milk for giant pandas cannot be overstated, especially considering the extreme immaturity of newborn panda cubs. Among the bear family, and excluding marsupials, pandas are born with the least developed, with newborns weighing only 100 to 150 grams, a mere one-thousandth of their mother's weight. They are blind, deaf, and unable to regulate their body temperature, relying entirely on their mother's care for survival and development.
Mothers of many species produce a special type of milk, known as colostrum, in the first few days after giving birth. This milk is rich in unique nutrients that are crucial for the immune system of newborns. It also contains proteins, lipids, and other essential molecules required for infant development.
For species like calves and foals, which are more developed at birth, colostrum is produced for only a few hours. Our recent paper, the third in a series on panda milk, hypothesized that due to the underdeveloped state of newborn pandas, the production of colostrum would last longer. Indeed, our analysis of six giant panda milk samples revealed that the secretion of colostrum can last from 30 to 40 days.
We also found that the composition of panda milk changes dramatically over time. Some components that are abundant at the beginning gradually disappear, while others that start at low concentrations sharply increase. The most significant changes are seen in molecules that contribute to the development of the eyes, brain, and nervous system.
Other fluctuating components are indispensable for the cubs, aiding in biosynthesis, cell membrane construction, antimicrobial defense, and the establishment of a microbiome in the digestive system. This microbiome may be particularly important during the first few years as pandas transition from milk to a bamboo-based diet, possibly relying on a specialized gut microbiota to digest the large quantities of bamboo.
Our analysis of the formula milk commonly used to supplement panda cubs in breeding centers revealed a severe imbalance in the proportions of key components, with some being too low and others too high. Unlike the dynamic colostrum of panda mothers, the formula's ratios and concentrations remain static, not adapting to the growth stages of the cubs.
For instance, we found that artificial formula milk contains an excess of lactose, which is abundant in cow's milk and other milks but absent in panda colostrum after the first few days. Lactose can cause severe gastrointestinal issues in panda cubs, disrupting the delicate microbial balance in their gut, which in turn can hinder their digestion throughout life.
Moreover, we discovered significant deficiencies in other key components of artificial formula milk, which could affect the development of the cubs' brains, eyes, and other organs. Given that the ultimate goal of captive breeding is to reintroduce pandas to the wild, artificial formula milk poses considerable risks.
The Impact of Artificial Formula Milk
The issues surrounding artificial formula milk are just the tip of the iceberg. In the wild, panda mothers invest significant time and skill in teaching their cubs to adapt to their environment and master survival skills, a process that still holds many mysteries. Human interference in breeding can disrupt the care provided by panda mothers, potentially causing numerous harms to the cubs, and our research has only scratched the surface.
Other factors may also be counterproductive, such as the constant live disturbances to panda families, being kept in confined and monotonous enclosures, and the lack of privacy and control over their nurturing environment for panda mothers. Breeding centers often forcibly separate cubs from their mothers at 3 to 5 months old to increase the chances of the mother panda breeding annually. This is a stark contrast to the wild, where a mother panda stays with her cubs for at least two to two and a half years, and female pandas breed every four to five years.
If we want captive-bred panda cubs to grow into healthy adults in terms of physical, cognitive, and behavioral development, breeders need to step back and let panda mothers take care of their cubs. Our research repeatedly emphasizes that evolution has endowed them with sufficient wisdom, and no one is better suited to the job than a panda mother.
