Mobile light therapy

A new way to advance the breeding season in mares is being developed following research into the use of light-emitting diodes (LEDs) to inhibit melatonin secretion.

 

Thoroughbred breeders aim to have foals born as soon as possible after the official birthday of January 1^st (in the northern hemisphere.) This gives them a head start in size and maturity when competing against other horses in the same age group, both at sales and subsequently at the race track.

However, breeding early in the year is at odds with the horse's natural breeding season, which occurs some months later.

Artificial light is commonly used to advance the breeding season in mares. When an early foal is desired, breeders will put the mare "under lights" - keeping the barn lights on in the winter, to mimic the lengthening days that initiate the natural breeding season.

The hormone responsible for controlling this seasonal variation in response to change in day length is melatonin. It is secreted by the pineal gland in response to darkness.

Researchers at the University College Dublin's School of Agriculture and Food Science, have been examining the effect of different levels of blue light on melatonin production.

Four healthy 5-year-old TB mares took part in the study, which was conducted around the vernal (spring) equinox, so the mares were accustomed to equal 12 hour periods of light and darkness. For the duration of the study the mares were housed in a light-tight barn with artificial lighting timed to mimic the conditions outside .

The researchers used LEDs (emitting blue light of wavelength 468nm) set in a head mask to investigate the effect of blue light on melatonin secretion in the horse. (Blue light (465–485 nm) has been found to be the most efficient for inhibiting melatonin secretion in humans.)

Blood samples were collected through indwelling catheters at the end of hour-long periods of exposure to dark or to varying intensities of light. The light was directed at either both eyes or just one eye.

All samples, except the first, collected after exposure to “daylight”, occurred during the dark phase of the 24 h cycle.

The results showed that blue light inhibited the production of melatonin. The inhibitory effect occurred regardless of whether the light was administered to one or both eyes.

Melatonin levels were significantly lower after exposure to 10 lux, 50 lux, 100 lux as well as barn light, than they were after an hour of darkness. Melatonin levels after exposure to 3 lux were not significantly different from those recorded in darkness.

Lead researcher Dr Barbara Murphy, concludes that “melatonin inhibition can be achieved by exposing a single eye to low wavelength blue light.” She adds that “this is a novel finding with important implications for management of artificial lighting regimens in horses.”

“The light mask represents a safe cost-effective method of administering timed low-level light to a single eye so that mares can be maintained outdoors in their natural environment, avoiding the costs of indoor maintenance, while effectively advancing the onset of the breeding season to meet industry timelines.”

Read more at equinescienceupdate.com

Study suggests fatter is naughtier

 

Being overweight is not just a problem in human health; recent research suggests that fat horses and ponies are more likely to misbehave than their more slender companions.

A study, Misbehaviour in Pony Club Horses: Incidence and risk factors, published in the Equine Veterinary Journal (EVJ) is the first of its kind to quantify the incidence of misbehaviour in a population of horses.

Conducted by Petra Buckley, Senior Lecturer in Equine Science at Charles Sturt University, New South Wales,the study involved 84 Pony Club horses from seven different Clubs in rural Australia. Over a period of a year owners kept daily records of horse management including nutrition, healthcare and exercise and recorded any misbehaviour.

Misbehaviour was classified as “dangerous” (such as bucking, rearing, biting or kicking) or “unwelcome” (including “pulling like a steam train”, playing up, resenting foot trimming, and being difficult to catch.)

The horses were checked by a vet every month to investigate any relationship between pain, such as lameness and back pain and misbehaviour.

Of the horses studied, 59% misbehaved at least once during the study year, either during handling or when ridden. Whilst the occurrence of misbehaviour during riding was low, at 3% of horses in each month, in more than half of these cases the misbehaviour was dangerous, and posed a serious injury risk to horse and rider.

Risk of misbehaviour was higher in horses that were fat or obese and in those that were ridden infrequently. Horses exercised more than three times each week were less likely to misbehave. The odds of misbehaviour during riding were more than twice as high when horses were fed daily supplements, such as roughage, concentrates and/or grain. Access to “good grass” was also associated with increased risk of misbehaviour, independent of any supplementary feed provided. Horses and ponies that were excessively fat were roughly three times more likely to misbehave.

This suggests a link between nutrition, exercise, body condition scores and misbehaviour, where higher body condition scores reflect dietary intake exceeding requirements, a problem that can be exacerbated by infrequent exercise.

The study includes recommendations to help prevent misbehaviour such as exercising at least three times a week and maintaining an optimal physique by more closely matching pasture and supplementary feeding to horses’ exercise levels and resulting energy requirements.

“Our results highlight the importance of considering horse body condition, nutrition and exercise in any investigation of horse misbehaviour” concludes Petra Buckley.

Read more at equinescienceupdate.com

Saddle slip may indicate lameness

Saddle slip may not be the result of an ill fitting saddle or asymmetrical back muscles. A recent study has shown that it is often a sign of hindlimb lameness.

The study, conducted at the Centre for Equine Studies at the Animal Health Trust in Newmarket , identified a significant link between hind limb lameness and saddle slip, showing consistent saddle slip in some horses with hind limb lameness, even when the lameness was fairly subtle and difficult to detect.

Saddle slip, in which the saddle slips consistently to one side, is a well-recognised problem in sports horses. It can occur for a variety of reasons, including asymmetry in the shape of the horse’s back, riders sitting crookedly and ill-fitting saddles.

Sue Dyson, Head of Clinical Orthopaedics at the Centre for Equine Studies, had also observed that saddle slip may occur because of hind limb lameness. The intention of the study, therefore, was to find out more about the interrelationships between the horse, saddle and rider and to document the frequency of occurrence of saddle slip in horses with hind limb lameness compared with other horses.

The research was undertaken by Line Greve, Intern at the Centre for Equine Studies, and Sue Dyson, and was presented at the British Equine Veterinary Association Congress in September 2012. It is thought to be the first study of its kind, and was supported by the Saddle Research Trust (SRT).

The study assessed 128 horses of varying size, age and type. The degree of lameness of each horse was graded; back shape and symmetry were measured and saddles assessed for symmetry and fit. Each horse was ridden by at least two riders and rider straightness plus weight were recorded. The grade of saddle slip, whether it occurred with more than one rider, and whether saddle slip was influenced by the direction of movement or the diagonal on which the rider was sitting were also noted.

The saddle consistently slipped to one side in 54% of horses with hind limb lameness, compared with 4% of horses with fore limb lameness, 0% with back pain and/or sacroiliac joint region pain and 0% of non-lame horses. The saddle usually slipped towards the side of the lame (or more lame) hindleg.

Diagnostic analgesia was subsequently used to abolish the hind limb lameness and this eliminated the saddle slip in 97% of cases.

Sue Dyson said: “Our findings emphasise the need to educate owners, veterinarians, physiotherapists, trainers, riders and saddle fitters that saddle slip is frequently an indicator of lameness, not necessarily a manifestation of an ill-fitting saddle or asymmetric shape of the horse’s back. Detection of saddle slip provides an opportunity for the owner, riders and trainers to detect low-grade and subclinical lameness, with important welfare consequences.”

Minimising the stress of weaning

What is the least stressful way to wean foals? A small scale pilot study compared three different procedures.

The research was carried out at the Graf Lehndorff Institute for Equine Science, Neustadt (Dosse), Germany, under the direction of Professor Christine Aurich. A full report of the study has been published in the journal Stress.

Different weaning procedures were used for each of three groups of mares and foals. Each group comprised 6 (or 5) mares and foals.

Methods of weaning used were:

• Group A (6 foals): all foals in the group were weaned at the same time

• Group B (5 foals): all foals were weaned at the same time, but were left with two mares with which they were familiar, but not related.

• Group C (6 foals): these foals were weaned by removing two mares from the group on each of three consecutive days

During the weaning process, the researchers monitored the foals' behaviour and movement. They also measured the concentration of cortisol in the foals' saliva, recorded their heart rate and variability, and their weight.

The results confirmed that weaning was associated with stress. All groups showed an increase in salivary cortisol on the day of weaning. In Group C the cortisol concentration remained elvated for two days.

Abrupt weaning with no further contact with adult animals seemed to be the most stressful. Foals in Group A lost weight for two days. They seemed more unsettled - spending more time moving about on the day of weaning. They also showed the most pronounced increase in heart rate.

Foals that were weaned in the presence of two familiar but unrelated mares, (Group B) seemed least affected by the weaning procedure. Of the three groups, they showed the least locomotion and vocalisation after weaning.

The researchers conclude: “Based on cortisol release and behavior, weaning is associated with stress but this was least pronounced in foals weaned in the presence of two familiar but unrelated adult female horses.”

Fixed time protocol for frozen AI

A fixed time insemination protocol described by researchers from Brazil could encourage a greater use of frozen semen in equine reproduction.

One of the reasons frozen semen is not more widely used for breeding mares is the need for insemination to occur close to the time of ovulation. This necessitates repeated ultrasound examinations when the mare is in season, making the technique time consuming and labour intensive.

For artificial insemination with frozen semen to become more widespread, a simplified routine is needed that is less labour intensive, but does not sacrifice fertility.

Bruno Ribeiro Avanzi and colleagues at the Department of Animal Reproduction and Veterinary Radiology, Universidade Estadual Paulista at Botucatu, used a fixed time insemination protocol to achieve conception rates comparable with those using a more traditional approach.

Semen from two stallions was used in the study. One stallion (A), a Westphalen, was of good fertility, the other, (B) a Mangalarga Marchador, was of poor fertility.

The semen was collected, processed and frozen using a standard method.

Twenty nine mares were enrolled in the study. The oestrus cycle was monitored by rectal palpation and ultrasound scanning. Once a pre-ovulatory follicle of at least 35mm diameter was present, each mare received an injection of the gonadotrophin releasing hormone deslorelin acetate.

Growth of the follicle was monitored every six hours, starting eighteen hours after the deslorelin. Half of the mares were inseminated when ovulation had been detected, the others were inseminated 40 hours after the administration of deslorelin regardless of whether ovulation had occurred or not.

All mares were inseminated into the tip of the uterine horn adjacent to the follicle.

For frozen semen from the fertile stallion, the researchers reported pregnancy rates of 46.7% (7/15) when bred 6 hours after ovulation, and 66.6% (10/15) for inseminations performed 40h after ovulation induction.

The less fertile stallion achieved pregnancy rates of 35.7% (5/14) when bred 6 hours after ovulation and 21.4% (3/14) for inseminations performed 40h after induction of ovulation.

The researchers conclude that insemination at a fixed time after ovulation induction is efficient. “The present data supports the feasibility of equine frozen semen as a technology to be widely used and spread since it reduces mare management and costs.”

Read more at equinescienceupdate.com