A re-think is needed over weaning practices in horses, according to researchers, who found that foals are naturally weaned from their mothers at 9 or 10 months in a stress-free way.
The authors of the French study say the need to re-examine traditional weaning methods is crucial for welfare reasons.
Animal behaviour specialist Dr Séverine Henry, from the University of Rennes, and her colleagues noted that most foals were usually artificially weaned at 4 to 7 months of age, before the time of natural weaning.
Artificial weaning is recognized as a major source of stress that can also lead to long-lasting harmful effects, the study team wrote in the open-access journal Animals.
“This common practice seriously impairs the welfare of foals,” they say. However, to date, there is little data on the natural process of weaning and the immediate consequences for both the mare and foal.
The researchers firstly reviewed current scientific knowledge on the subject.
“It is to be noted,” they wrote, “that the natural process of weaning is little documented, individual variations have been poorly investigated and immediate effects of weaning on the mare–foal relationship remain unexplored.”
To partly address these gaps, the researchers performed a study around the weaning period on 16 mare–foal pairs kept with minimal human interference.
“We found that most foals were weaned spontaneously between 9 and 10 months of age, and overall, that natural weaning induced no stress response in either partner and no sign of rejection from the dam.”
Individual variations related mainly to the conception rate of mares, they said.
Contrary to expectations, the older mares did not tend to wean their foals earlier and, overall, no loss of body condition was noted over the lactation period.
“Natural weaning induced no stress response in either partner and was performed without clear signs of rejection by the dams either just before or after.”
The researchers said that even though the precise origin of early artificial weaning is unclear, it is important to go back to the sources of such a practice.
In the second half of the 19th century, several studies highlighted two main results that probably led to the routine practice of early artificial weaning. Firstly, it has been found that maternal milk production decreased sharply by the third month of lactation and secondly, that the nutritional needs of 3–4 month-old foals exceeded the level of nutrients available from maternal milk.
“From that point, early weaning may have been considered the best decision to make to optimize the physical development of domestic foals.
“This practice became rapidly widespread in professional breeding farms followed by non-professional breeders of one or two mares.
Economy and safety a factor
“Nowadays, there are many practical, economical and safety reasons to proceed to the early weaning of foals, such as allowing for an early marketing of foals, switching the foal’s attention from the mother to humans, facilitating the management of the foal’s nutritional intake without the mare interfering, or even optimizing the subsequent reproductive efficiency of the mares by limiting the potential negative impact of a prolonged nursing.”
Some of the reasons are based more on habits and tradition, perhaps even on false beliefs, and clearly not on the prospects for improving the welfare of domestic foals, they said.
“While the impact of artificial weaning on mares has not yet been properly examined, it is now well admitted that artificial weaning is one of the most stressful events in a foal’s life.”
The well-known behavioral responses to early weaning and the associated risks of injury, typically peak within the first two post-weaning days.
“However, other behavioral changes such as altered feeding and sleeping patterns, aggressiveness, suspension of play and redirected suckling towards peers stemming from frustration, may be observed for much longer periods.”
Weanlings show elevated stress hormone levels, changes in heart rate, as well as a decline in growth rates. “Most of these behavioral and physiological manifestations are more intense in the first post-weaning days and vanish within two-three weeks.”
Gut and behavior issues noted
However, artificial weaning can also cause chronic problems, they said. Stress hormones lead to a subsequent decrease in immune response. There is also evidence it can affect the development of the gut microbiota.
“Numerous scientific studies also point out, in foals, as in other domestic or captive young mammals, that early weaning is a major cause of stereotypic behaviors and thus of animal welfare impairment.”
They continued: “Without human interference, the situation is of course dramatically different. It is often reported that weaning takes place gradually over several months through the joint initiative of the dam and the foal, and that foals are usually not weaned before the age of 9-11 months or until shortly before the birth of the next foal.”
However, “natural weaning” only implies a nutritional aspect, as the close dam-offspring bond remains afterwards for a much longer time.
The researchers, discussing their findings, said modern breeding practices generally imposed strong constraints compared to the conditions of development of foals in a more natural environment. One interesting finding of the study was that the natural weaning process induced no frustration or distress behaviors in either party.
“These results thus suggest that the main source of stress in artificial weaning is rather the abrupt rupture of the dam–foal bond than the cessation of suckling.
“This would explain why gradual weaning, allowing foals to see, hear, smell, and touch their dams through a fence, but not suckle, results in fewer behavioral responses than abrupt weaning.
“Similarly, a recent study that investigated the effect of a two-stage weaning method which involves separating the effects of the nutritional part (suckling) and the physical part (social bond), tends to confirm this assumption.”
The researchers suggest that switching to natural weaning, especially in smaller breeding farms, is feasible.
“There are easy changes to make in management practices to do so, such as installing selective feeders to make sure foals have access to sufficient food or providing forage ad libitum to make sure that mares are not losing weight, especially in cases of concurrent lactation and pregnancy.
“Maintaining foals with their dams over a longer period of time also offers the benefit to use maternal influences to facilitate the education of foals, to decrease the occurrence of stereotypic behaviors in breeding mares and to lower aggression within groups, horses being less aggressive when in groups with foals.”
The authors say further studies are needed to better identify what should constitute the best weaning practices with respect to the welfare of foals and mares.
“However, it also seems essential to conduct longitudinal studies to compare artificially weaned foals with foals that have been naturally weaned in order to assess all the potential consequences of artificial weaning.”
The study team comprised Henry, Aziliz Klapper, Julie Joubert, Gabrielle Montier and Martine Hausberger, all with the University of Rennes; and Hrefna Sigurjónsdóttir, with the University of Iceland.
Henry, S.; Sigurjónsdóttir, H.; Klapper, A.; Joubert, J.; Montier, G.; Hausberger, M. Domestic Foal Weaning: Need for Re-Thinking Breeding Practices? Animals 2020, 10, 361.