Abstract: The ability to jump over an obstacle depends upon the generation of work across the joints of the propelling limb(s). The total work generated by one hind limb of a horse and the contribution to the total work by four joints of the hind limb were determined for a jump. It was hypothesized that the hip and ankle joints would have extensor moments performing positive work, while the knee would have a flexor moment and perform negative work during the jump. Ground reaction forces and sagittal plane kinematics were simultaneously recorded during each jumping trial. Joint moment, power and work were determined for the metatarsophalangeal (MP), tarsal (ankle), tibiofemoral (knee) and coxofemoral (hip) joints. The hip, knee and ankle all flexed and then extended and the MP extended and then flexed during ground contact. Consistent with our hypothesis, large extensor moments were observed at the hip and ankle joints and large flexor moments at the knee and MP joints throughout ground contact of the hind limb. Peak moments tended to occur earlier in stance in the proximal joints but peak power generation of the hind limb joints occurred at similar times except for the MP joint, with the hip and ankle peaking first followed by the MP joint. During the first portion of ground contact (approximately 40%), the net result of the joint powers was the absorption of power. During the remainder of the contact period, the hind limb generated power. This pattern of power absorption followed by power generation paralleled the power profiles of the hip, ankle and MP joints. The total work performed by one hind limb was 0.71 J kg(-1). Surprisingly, the knee produced 85% of the work (0.60 J kg(-1)) done by the hind limb, and the positive work performed by the knee occurred during the first 40% of the take-off. There is little net work generated by the other three joints over the entire take-off. Velocity of the tuber coxae (a landmark on the pelvis of the animal) was negative (downward) during the first 40% of stance, which perhaps reflects the negative work performed to decrease the potential energy during the first 40% of contact. During the final 60% of contact, the hip, ankle and MP joints generate positive work, which is reflected in the increase of the animal's potential energy.

Abstract: Much evidence now suggests that the postnatal killing of young in primates and carnivores, and induced abortions in some rodents, are evolved traits exerting strong selective pressures on adult male and female behaviour. Among ungulates it is perplexing that either no species have developed convergent tactics or that these behaviours are not reported, especially as ungulates have social systems similar to those of members of the above groups. Only in captive horses (Equus caballus) has infant killing been reported. It has been estimated that 40,000 wild horses live in remote areas of the Great Basin Desert of North America (US Department of Interior (Bureau of Land Management), unpublished report), where they occur in harems (females and young) defended by males. Here I present evidence that, rather than killing infants directly, invading males induce abortions in females unprotected by their resident stallions and these females are then inseminated by the new males.

Abstract: In order to determine if horses will increase their intake in response to caloric dilution, four pony geldings were fed ad lib a mixed grain diet either undiluted (3.4 Mcal/kg of digestible energy) or diluted (wt/wt) with 25% sawdust (2.6 Mcal/kg) or with 50% sawdust (1.7 Mcal/kg). The mean daily caloric intake was 17,457 kcal (3.4 Mcal diet), 17,546 kcal (2.6 Mcal diet) and 12,844 kcal (1.7 Mcal). The mean time spent eating was 246 (3.4 Mcal), 351 (2.6 Mcal), and 408 (1.7 Mcal) minutes/day. Meal size increased and meal frequency decreased with increasing dilution. The median long survivorships of intermeal intervals were 6.4 min (3.4 Mcal), 3.95 min (2.6 Mcal) and 4.91 min (1.7 Mcal). Ponies responded to caloric dilution by increasing the volume of intake to maintain caloric intake when the diet had 25% diluent. When the diet was diluted by 50%, intake was increased, but not at a rate adequate to maintain caloric intake. However, the ponies were able to maintain body weight.

Abstract: Lateralization of emotions has received great attention in the last decades, both in humans and animals, but little interest has been given to side bias in perceptual processing. Here, we investigated the influence of the emotional valence of stimuli on visual and olfactory explorations by horses, a large mammalian species with two large monocular visual fields and almost complete decussation of optic fibres. We confronted 38 Arab mares to three objects with either a positive, negative or neutral emotional valence (novel object). The results revealed a gradient of exploration of the 3 objects according to their emotional value and a clear asymmetry in visual exploration. When exploring the novel object, mares used preferentially their right eyes, while they showed a slight tendency to use their left eyes for the negative object. No asymmetry was evidenced for the object with the positive valence. A trend for an asymmetry in olfactory investigation was also observed. Our data confirm the role of the left hemisphere in assessing novelty in horses like in many vertebrate species and the possible role of the right hemisphere in processing negative emotional responses. Our findings also suggest the importance of both hemispheres in the processing positive emotions. This study is, to our knowledge, the first to demonstrate clearly that the emotional valence of a stimulus induces a specific visual lateralization pattern.

Abstract: A study carried out on 49 horses showed that it is possible to measure the attention time by operant conditioning. After teaching horses an instrumental task using a signal, we were then able to test their attention time by asking them to prolong it increasingly while setting success and failure criteria. Two tests were performed 3 weeks apart. The 2nd test was feasible without relearning, a proof of memory, and was repeatable, a proof of consistency in the attention time. A significant difference was observed between the 3 age groups. Young horses often performed very well during the 1st test but their attention dropped in the 2nd test while older horses were more stable with respect to attention and even increased it slightly. The study shows that there are individual differences but it was not possible to prove a significant influence of breed, gender and paternal influence. Consequently, learning appears to be one of the most interesting approaches for evaluating the attention of horses and for observing their behaviour.