In this article, Professor Sylvie Chastant-Maillard and Dr Hanna Mila discuss the importance of colostrum for building a foundation of immunity in neonatal puppies. The quality of colostrum produced by the bitch is largely dependent on her own immunity and health. This article outlines the components of colostrum and how neonatal immunity develops. It also explores how to improve colostrum production and quality, and what to do in the absence of colostrum.
How to Boost the Immunity of Your Puppies: Colostrum and Milk
Pregnancy is not only the time for the intra-uterine growth and maturation of puppies, but also the time for the preparation of essential mammary secretions. During the second part of pregnancy, mammary epithelial cells multiply and at the very end of gestation, trap circulating immunoglobulins.
What is Colostrum?
After parturition (and sometimes even two weeks before), mammary cells begin to secrete lipids, lactose and proteins, especially immunoglobulins (also referred to as antibodies). This first mammary secretion is called colostrum and is of a very specific composition (double the proteins and half the lactose in cow’s milk). During the first two days of life, it is of crucial importance for the survival of puppies, providing energy supplies and immunological support.
Why is Colostrum so Important for Puppies?
Colostrum is a Key Factor for Puppies’ Immunity
Colostrum is characterized by a high concentration of Ig - immunoglobulins (or antibodies) -that are crucial for providing immune support to the neonatal puppy. At the time of whelping, total Ig concentration in colostrum is 20-30 ng/mL whereas at one month of lactation, this level has dropped to 5-10 ng/mL. Several types of Ig, with different biological functions, are secreted in colostrum. The two main classes are IgG, responsible for systemic immunity, and IgA, responsible for the local protection of mucosa (especially in the digestive and the respiratory tracts). The proportions of the various classes of Ig vary with the time period elapsed after parturition: in colostrum, IgG and IgA represent respectively 60% and 38% of the total Ig, whereas in milk (one month after lactation), these proportions change to 5% and 90%. Compared to maternal serum, canine colostrum contains two times more IgG, but 13 times more IgA.
Due to the histological structure of the canine placenta (endotheliochorial junction in dogs is four cell layers between foetal and maternal blood, compared to only one cell layer in humans), the concentration of Ig at birth in puppies’ bloodstream is close to zero (around 0.3 g/l vs around 10 g/l for an adult).
Only 5-10% of the circulating Ig in puppies at two days’ of life crosses the placenta during pregnancy via foetal circulation. The other 90-95% is provided by colostrum and is absorbed immediately after birth by the neonatal gut. This phenomenon is called "passive immune transfer". Its quality is evaluated through the blood IgG concentration in puppies during the first days of life.
Colostrum contains not only Ig, but also trypsin inhibitors, protecting colostral Ig from proteolysis in the puppies’ gut. This can contribute to the relative inefficiency of oral administration of serum as a colostral replacer to reach a significant passive immune transfer. It also contains immune cells, which are destroyed after freezing/thawing.
Colostrum is Rich in Energy
Neonates have minimal body fat reserves and limited metabolic capacities to generate glucose from precursors stored in the body. At the same time, they are exposed to high heat losses due to wet skin and a high body surface/weight ratio. During the first day of life, puppies are supposed to ingest 9-14 mL colostrum/100g body weight. An adequate supply of nutrients in relation to actual requirements has to be followed through an every-day weight follow-up: apart from a weight loss between birth and day two of life (10% max), puppies are expected to increase their weight by 2-4g/kg adult weight each day (+5-10%/day). Puppies that lose weight during the first two days of life are of higher risk of death and higher risk of insufficient passive immune transfer.
Colostrum for the Maturation of Puppies
Colostrum also contains hormones (growth hormone, leptin, insulin, cortisol) and growth factors (epidermal growth factor, insulin-like growth factors), crucial for the intestinal and pancreatic maturation of the newborn. It thus contributes to the adaptation of the puppies to extra-uterine life.
Colostrum and Health
Colostrum ingestion has an impact on morbidity, mortality and intestinal health of puppies until at least two months of age.
We recently demonstrated that puppies with blood Ig concentration lower than 2.3 g/l at two days of life (i.e. with insufficient passive immune transfer) were at higher risk of mortality within the first three weeks of life than those with better passive immune transfer. Focusing on parvovirus infection, we observed that only puppies with high levels of absorbed colostrum-derived antibodies against CPV-2 had the minimal protective antibody level till 28 days of age: 63% of the puppies with high immune transfer at two days of age were still protected at day 28, against only 28% for intermediate transfer and 0% with low transfer. The very early ingestion of colostrum is thus crucial to ensure the bloodstream absorbs the highest quantity of immunoglobulins.
However, the interest of colostrum ingestion by the puppies is not restricted to the first hours after birth. Colostrum-derived IgA ingested after the gut closure retains a local protective role for the intestinal mucosa by coating it and by trapping pathogens present in the lumen. Since digestive pathogens are frequent causes of death in puppies, suckling of late colostrum, and then milk, remains indicated long after the closure of the intestinal barrier.
Management of Colostrum
When Should Colostrum be Administered?
Passive immune transfer (absorption of Ig from the intestinal lumen through the bloodstream) requires the permeability of the intestinal mucosa to macromolecules. This property, present at birth, is progressively lost during the first hours of life. It is retained in the canine species only during the first 16-24 hours after birth. Whereas 40% of the ingested Ig is absorbed at birth, the absorption rate falls at 20% four hours after birth, 10% at 12 hours and is null at 24 hours.
From a practical point of view, puppies have to be fed colostrum as early as possible and at least during the first 12 hours of life to optimize passive immune transfer. Attention has thus to be given to first suckling. If necessary, the bitch can be milked manually (after oxytocin injection - 0.1 UI/kg IM - eventually) and colostrum administered via a feeding tube under veterinary supervision.
How to Improve Colostrum Production
Before whelping, modifications of the diet during the last two weeks of pregnancy, matching energy, proteins and vitamins (in particular Vitamins A and E) requirements are of special interest to ensure sufficient milk production with sufficient energy concentration. During and after whelping, limiting stress for the bitch encourages the adequate onset of colostrum production.
How to Improve Colostrum Quality
Obviously, improving the immunological quality (IgG concentration) of colostrum would increase the puppies’ chances of reaching the minimal protective IgG threshold. This is why conventional vaccination (especially against parvovirus) at a short delay before heats and revaccination in late pregnancy against canine herpes virus 1 are advised. Nevertheless, there is no link between colostrum Ig concentration and puppies’ serum Ig concentration. This strongly suggests that the main limiting factors of passive immune transfer are in fact the quantity and/or the age at first ingestion.
Any drug treatment to a lactating bitch has to evaluate any risk of trans-mammary passage of the molecules to avoid any risk for puppies. Molecules considered as safe for foetuses during pregnancy are usually considered to be secure for suckling puppies. Colostrum can also carry pathogenic bacteria, directly in case of mastitis, or indirectly in case of poor teat hygiene. Worming the bitch at around 40 days of pregnancy is advised to limit the transmission of parasites through suckling.
What to Do in the Absence of Colostrum
In the absence of available colostrum, an alternative is needed to provide both energy and immunoglobulins. Energy supply must be ensured through a milk replacement, with a neonatal caloric requirement of 134 kcal/kg/day during the first week.
In terms of passive immunity transfer, no milk replacement can be a real source of canine immunoglobulin. Obviously, adoption by another bitch having whelped 2-3 days before is a good (probably the best, but not easy) solution. Constitution of a colostrum bank should be encouraged: colostrum can be collected by manual milking in the best hygienic conditions before whelping and until the 2-3 first days after whelping. For thawing, do not use a microwave and remember that samples must be kept at temperatures lower than 53°C. Immune cells will be killed by freezing/thawing, but immunoglobulins will remain active.
The oral administration of adult canine serum allows a very limited increase of IgG blood concentration. Even if the levels obtained after subcutaneous injection of the serum (4 mL/100g body weight) remain 10 times below those obtained thanks to free colostrum suckling, this way of administration seems at the least to allow puppies to exceed the critical IgG threshold (2.3 g/L).
The relevance of heterospecific colostrum (e.g. bovine, for ease of access) for puppies’ systemic protection remains to be proven. It seems to have a positive effect on gut physiology when given after weaning.
The survival of puppies is thus highly dependent on the care given to the bitch very early during the pregnancy (and even before oestrus; worming, vaccination, nutrition) and then to the care given to puppies in the immediate hours after birth.