The authors would like to thank Mingxuan Li for his editing of the grammar and polishing of the early version of this manuscript. This work was supported by the Zhejiang Province Natural Science Foundation of China (LD22H090003); the Natural Science Foundation of China (32170991 and 32071097), STI2030-Major Projects 2021ZD0204100 (2021ZD0204101) and 2022ZD0205000 (2022ZD0205003); and the MOE Frontier Science Center for Brain Science &#38; Brain-Machine Integration, Zhejiang University.

All the experimental procedures were approved by the Animal Use and Care Committee of Zhejiang University and followed the National Institutes of Health (NIH) guidelines.
1. Housing and husbandry44
<ol>
	<li>Set the colony room with a 12 h:12 h day/night cycle, the temperature at 26-28 &#176;C, and the relative humidity at 45%-55%.</li>
	<li>Pair male and female marmosets at 2-6 years old, and hold them in cages (850 mm x 800 mm x 800 mm) with suffici...

Enhancing Survival and Development of Marmosets Using a Hand-Rearing Approach

The common marmoset is a very useful NHP model for biomedical and neuroscience research. However, marmoset resources are too limited to meet the rapidly growing needs. In this work, we have developed a hand-rearing method that not only increases the survival rate of marmoset infants but also provides an opportunity to study their postnatal development. This hand-rearing method is practical and easy to learn and is, therefore, easily applicable to other labs working with common marmosets.
Some ...

The common marmoset (Callithrix jacchus) is a small and arboreal New World monkey originating from South and Central America. The use of marmosets in biomedical research has grown rapidly over the past decades due to several key advantages of marmosets compared with other non-human primates (NHPs), including their smaller body size, easier handling and breeding in captivity, shorter gestation time, earlier sexual maturation, and lower zoonotic risks1,2,3,4,5,6. The common marmoset has a similar brain structure and brain function to humans and displays a rich repertoire of vocalizations and highly social behavior with rich emotions. It is a compelling NHP model for different types of neuroscience studies, such as studies on sensory processing7,8,9,10,11,12,13,14, vocal communication15,16,17,18,19, models of spinal cord injury20,21,22,23, Parkinson&#39;s disease24,25,26,27,28, and age-related diseases29. Compared with other NHPs, the common marmoset has a relatively high reproduction rate, which is potentially useful for transgenic modification30,31,32. This primate is also widely used in pharmacology, angiography, and pathogen and immune studies33,34,35,36,37,38,39. However, the supply of marmosets remains very limited, especially in China, and cannot meet the rapidly growing needs of scientific research.
In marmoset colonies, the adult animals are fed once or twice per day, and a few institutions alter the diet for juvenile marmosets40. Generally, infant marmosets usually grasp firmly onto the body of the father or elder siblings for daily care and are handed to the mother several times per day for milk. Some female marmosets give birth to triplets, and in this case, one or two infants cannot survive due to a lack of milk; moreover, some parents do not take care of their infants because they lack nursing experience or for other unknown reasons. This is a big loss for many laboratories. A few studies have reported methods of nutrition management for adult marmosets in captive settings40,41,42 utilizing foods and formulas with different macronutrient compositions, vitamins, and minerals, as well as different feeding protocols for enrichment (mashed, gelled, purified, or canned)2,41. One previous study reported a collaborative rearing method for marmoset triplets43, in which caregivers take one infant per day, hand-feed it throughout the day, and exchange it for another of the triplets on the next day. Although this method allows the infants to have parental care, it requires an experienced caregiver to grab the infant from the body of the parents every day and is labor-intensive. So far, no study has reported a detailed, step-by-step hand-rearing method for newborn marmosets.
The goal of the current study is to provide a hand-rearing method for those interested in marmoset development but with limited resources. In contrast to the previous collaborative rearing method43, the current method is an alternative that causes less disturbance to the infant&#39;s family and is easy to learn. Based on the basic rules of breastfeeding and 5 years of practice, this paper describes a hand-rearing method for raising infant marmosets that includes the preparation of the food, a timetable for feeding, the configuration of the temperature and humidity of the animal incubator, as well as the adaptation of the infant animals to the colony environment.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>animal incubator</td>
			<td>RCOM, Korea</td>
			<td></td>
			<td>MX - BL600N, 855 mm (W) x 470 mm (L) x 440 mm (H)</td>
		</tr>
		<tr>
			<td>baby milk powder</td>
			<td>Meadjohnson, America</td>
			<td></td>
			<td>suitable for 0-12 months of age, executive standard - GB25596</td>
		</tr>
		<tr>
			<td>baby rice paste</td>
			<td>HEINZ, China</td>
			<td></td>
			<td>suitable for 0-6 months of age, executive standard - GB10769</td>
		</tr>
		<tr>
			<td>baby wipes</td>
			<td>babycare, China</td>
			<td></td>
			<td>soft</td>
		</tr>
		<tr>
			<td>beaker</td>
			<td>ShuNiu, China</td>
			<td></td>
			<td>100 mL</td>
		</tr>
		<tr>
			<td>blankets</td>
			<td>Grace, China</td>
			<td></td>
			<td>10 cm &#215; 10 cm, soft</td>
		</tr>
		<tr>
			<td>climbing frame</td>
			<td>WowWee, China</td>
			<td></td>
			<td>firm and no small circular structures</td>
		</tr>
		<tr>
			<td>disposable diaper pads</td>
			<td>Hi Health Pet, China</td>
			<td></td>
			<td>either M or L size</td>
		</tr>
		<tr>
			<td>disposable sterile syringe</td>
			<td>Cofoe, China</td>
			<td></td>
			<td>1 mL, 2.5 mL, 3 mL, 5 mL, 10 mL</td>
		</tr>
		<tr>
			<td>electronic scale</td>
			<td>YouSheng, China</td>
			<td></td>
			<td>measuring range from 0 to 6,000 g with precision of 0.2 g</td>
		</tr>
		<tr>
			<td>intravenous injector</td>
			<td>HD, China</td>
			<td></td>
			<td>0.55 mm x 20 mm needle</td>
		</tr>
		<tr>
			<td>kettle</td>
			<td>FGA, China</td>
			<td></td>
			<td>warm-keeping kettle 1,500 mL</td>
		</tr>
		<tr>
			<td>lactulose</td>
			<td>BELCOL, China</td>
			<td></td>
			<td>to solve constipation</td>
		</tr>
		<tr>
			<td>plastic weighing dish</td>
			<td>SKSLAB, China</td>
			<td></td>
			<td>80 mm x 80 mm x 22 mm, used as a bowl</td>
		</tr>
		<tr>
			<td>plush toy</td>
			<td>Lebiyou, China</td>
			<td></td>
			<td>soft</td>
		</tr>
		<tr>
			<td>probiotic powder</td>
			<td>G-Pet, China</td>
			<td></td>
			<td>to regulate gastrointestinal environment</td>
		</tr>
		<tr>
			<td>sterile centrifuge tube</td>
			<td>NEST, China</td>
			<td></td>
			<td>50 mL</td>
		</tr>
		<tr>
			<td>swab</td>
			<td>OYEAH, China</td>
			<td></td>
			<td>80 - 100 mm</td>
		</tr>
		<tr>
			<td>toy roller</td>
			<td>WowWee, China</td>
			<td></td>
			<td>firm and no small circular structures</td>
		</tr>
	</tbody>
</table>

hand-rearing method for infant marmosets

The common marmoset (Callithrix jacchus) is a small and highly social New World monkey with high reproduction rates, which has been proven to be a compelling non-human primate model for biomedical and neuroscience research. Some females give birth to triplets; however, the parents cannot raise all of them. To save these infants, we have developed a hand-rearing method for raising newborn marmosets. In this protocol, we describe the formula of the food, the time for feeding, the configuration of the temperature and humidity, as well as the adaptation of the hand-reared infants to the colony environment. This hand-rearing method significantly increases the survival rate of marmoset infants (without hand-rearing: 45%; with hand-rearing: 86%) and provides the opportunity to study the development of marmoset infants with similar genetic backgrounds raised in different postnatal environments. As the method is practical and easy to use, we anticipate that it could also be applied to other labs working with common marmosets.

Author Spotlight: Marmoset Research - Scope and Challenges 

Hand-Rearing Method for Infant Marmosets

The marmoset is a highly vocal and highly social New World monkey with high reproductive rate. We are interested in the sound processing in the brain of marmosets, the vocal development and vocal communications of infant marmosets, as well as the establishment of marmoset models of human mental diseases. The current big challenge is the shortage of marmoset supply, which cannot meet the needs of scientific research and thus, impede the progress of marmoset studies.Another challenge is the lack of experiments in maintaining a marmoset colony. This hand-rearing method significantly increases the survival rate of marmoset infants, and provides the opportunity to study the development of marmoset infants with a similar genetic backgrounds, but raised in different postnatal environments.

Body weight is a key index of animal body development and is used as an indicator of the health status of the marmosets in this protocol. In this work, the body weights of the hand-reared animals increased gradually with age (Figure 2A, n = 16), similar to the weights of newborn infants in a previous study46. To minimize the disturbance to the breeding families in the colony, we did not weigh the infant marmosets in the colony every day. We obtained the weights of the...

Watch this Scientific Journal Video about Marmoset Research - Scope and Challenges at JoVE.com

Here, we describe a hand-rearing method for raising infant marmosets in an animal incubator. This method greatly increases the survival rate of marmoset infants, which provides the opportunity to study the development of marmoset infants with similar genetic backgrounds raised in different postnatal environments.