Behavioural response of dairy cows with and without calf-contact to hair of own and alien calves presented in the milking parlour

Highlights

• We tested responses of dairy cows to olfactory stimuli in the milking parlour.

• Stimuli were cloth bags with hair of the own or an alien calf or no hair.

• Primi- and pluriparous cows either reared their own calf or not while being milked.

• Response rates were generally low, but they significantly differed between stimuli.

• All cows and the calf-rearing heifers were more responsive to calf-linked stimuli.

Abstract

In systems where dairy cows are milked and additionally suckle their calves during the first months of lactation, problems with alveolar milk ejection during machine-milking occur. As olfaction is a key sense for kin recognition and acceptance at the udder, olfactory stimulation might alleviate this challenge. In this pilot study, we investigated whether cows behaviourally respond to calf hair presented in the parlour, and whether this is affected by suckling the own calf or not. Discrimination between hair of the own calf in a thin cloth bag (‘own’), hair of an alien calf (‘alien’) and a control cloth bag without calf hair (‘no’) was tested among 17 multiparous and 6 primiparous cows with free calf-contact (‘contact’) and 13 multiparous and 4 primiparous cows separated within 12 h after parturition from their calves (‘control’). Both groups were milked twice daily in a tandem milking parlour, where they were individually tested in six consecutive milkings (trials) starting between the 12th and 20th day of lactation. Two of three olfactory stimuli were simultaneously presented. Sniffing or licking of the stimuli during the first minutes of milking (response duration in % of total observation time) and number of trials with any response (frequency of responses) were recorded. Calf hair (‘own’ or ’alien’) elicited responses in 60% of the animals at least once, but altogether there were only overt responses in 23% of trials. Significant differences in responsiveness towards the different stimuli were found in terms of frequency of responses for all cows (n = 28 without missing data, p = 0.003). Response duration differed significantly for all responsive multiparous cows (n = 12, p = 0.049) and in tendency for all responsive heifers (n = 8, p = 0.061) and for responsive ‘contact’ cows and heifers (n = 11, p = 0.034). In all these cases, responses were highest for ‘own’, intermediate for ‘alien’ and lowest for ‘no’. In the post hoc tests, no significant differences between ‘own’ and ‘alien’ could be detected. Despite low response rates to the presented olfactory stimuli in general, we conclude that the responsive multiparous cows and ‘contact’ heifers were able to perceive the presented calf odour and preferred to sniff/lick those stimuli compared to a stimulus with ‘no’ odour.

Introduction

Dairy calf rearing systems, in which the calves are allowed to suckle their mothers and the cows are additionally milked, have both advantages and disadvantages (Johnsen et al., 2015). One of the challenges to overcome is a decreased milk yield during machine milking due to disturbed alveolar milk ejection, which, in turn, is caused by suppressed oxytocin release (Bar-Peled et al., 1995, De Passillé et al., 2008, Sandoval-Castro et al., 1999). The underlying mechanisms are not completely understood, but a lack of calf-associated stimuli during milking may play a role. The odour of the cow’s own young might be an especially strong stimulus. At least in ewes, olfaction is particularly important for the acceptance of the lamb at the udder (Alexander and Stevens, 1981, Alexander et al., 1983). Most scientific research on olfactory young recognition in farm ungulates has been done in ewes, but some studies have been conducted on goats and cattle as well. Olfactory selectivity is established through the prepartum rise of oestrogen, vaginocervical stimulation caused by fetus expulsion and the licking of the neonate, which, in turn, is elicited by an olfactory attraction towards amniotic fluid, and triggers further hormonal and neurophysiological processes in the mother (reviewed by Lévy and Keller, 2009 and Poindron et al., 2007). The influence of olfaction during the establishment of maternal selectivity was demonstrated by comparing intact goats or sheep with animals prenatally rendered anosmic. The latter were not attracted to amniotic fluid (Lévy et al., 1983) and did not form an exclusive bond with their own offspring, but also suckled alien young (ewes: Ferreira et al., 2000, Lévy et al., 1995, Poindron and Le Neindre, 1980; goats: Hernandez et al., 2002, Romeyer et al., 1994). Among anosmic goats, the oxytocin release was the same when suckling their own or an alien young, while intact goats showed a higher oxytocin release when suckling their own kid (Hernandez et al., 2002). Likewise, in beef cattle, anosmic mothers showed lower suckling-mediated inhibition of LH secretion than intact animals while suckling their own calf. This may lead to an earlier oestrus after calving among anosmic animals (Griffith and Williams, 1996).

If calf odour shall be used as a potential stimulus in the milking parlour, the first question that arises is how to present it in a way that is best perceived by the cow. In sheep, scent rather than pheromones is responsible for the development of a selective recognition of the lamb (reviewed by Kendrick et al., 1997). Odours of faeces or urine play a minor role in maternal recognition in ewes (Alexander and Stevens, 1981; [Alexander and Stevens, 1983]1982/83). The theory that lambs are “labelled” by their mother’s milk or saliva could not be substantiated (Alexander and Stevens, 1982/83; Lévy et al., 1991). Textile materials, with which animals were rubbed or which were worn by an animal or human, have been successfully used in fostering (beef cattle: Dunn et al., 1987; ewes: Martin et al., 1987) and discrimination tests (ewes: Alexander and Stevens, 1982/83; humans: Porter and Cernoch, 1983, Porter and Moore, 1981, Lundström et al., 2009; European storm petrel sea birds: Bonadonna and Sanz-Aguilar, 2012). Therefore, Barth et al. (2010) rubbed calves with cotton cloths, which were used to reproduce an olfactory stimulation in dairy cows in the milking parlour. However, neither behavioural responses were detected nor an increase in milk ejection achieved. It remained unclear whether the cows did not perceive the stimulus or merely did not react to it. Therefore, in this study we attempted to intensify the calf-odour of samples presented to cows in the milking parlour. A source of odour, which worked well in choice tests with ewes, was wool of different body regions (Alexander, 1978; Alexander and Stevens, 1982/83). For acceptance at the udder, the odour from the anogenital region of the lambs was most important (Alexander et al., 1983). Therefore, calf hair from the anogenital region and hind limbs was used as the source of odour in this study to elicit a behavioural response in cows during milking. As proffering each cow the hair of her own calf is too labour intensive for normal farm practices, the response to alien calf hair is of significant interest. This pilot study addressed the questions whether (i) cows behaviourally respond to small amounts of calf hair presented in the parlour (compared to a control without calf hair), (ii) responses are different to hair of the own calf or an alien calf, and whether (iii) cows with and without calf contact behave differently to the olfactory stimuli. The possible influence of olfactory stimulation on milk let-down was tested in another experiment, not presented here.