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The effects of extended photoperiod and warmth on hair growth in ponies and horses at different times of year.

ABSTRACT: Photoperiod is considered the most dominant environmental cue allowing animals to anticipate and adapt to seasonal changes. In seasonally breeding mammals, changes in daylength alter pineal melatonin secretion and pituitary prolactin secretion. During the seasonal transition to shorter winter daylengths, increased production of melatonin and declining prolactin are associated with triggering winter coat growth in many animals. Similarly, studies have shown that artificial extension of photoperiod suppresses melatonin secretion and lifts prolactin inhibition to activate moulting. Four longitudinal cohort studies were conducted to determine if extended photoperiod and warmth, provided by mobile light masks and rugs (horse blankets), could reverse the onset of winter coat growth, maintain the summer coat and accelerate winter coat shedding in horses and in ponies. Studies began at dates corresponding to the autumnal equinox, one month post-summer solstice, one month pre-winter solstice and one month post-winter solstice, respectively. To extend photoperiod to approximately 15h of light, commercially available head-worn light masks provided low intensity blue light to one eye until 11pm daily. Coat condition and shedding rate were scored and hair samples collected, measured and weighed bi-weekly. Data from control and treatment groups were analysed by repeated measures ANOVA. Results revealed that extended photoperiod 1) did not reverse winter coat growth when initiated at the autumnal equinox, 2) effectively maintained the summer coat in stabled horses when initiated one month post-summer solstice, 3) accelerated shedding in outdoor living horses when initiated one month pre-winter solstice and 4) did not accelerate shedding in indoor or outdoor living ponies when initiated one month post-winter solstice. To successfully manage equine coat growth while also preserving optimal thermoregulation in both competition and breeding stock correct timing of light application is crucial and requires careful monitoring of environmental temperature. Further studies are needed where variations in breed and management are considered.

SUBMITTER: O'Brien C

PROVIDER: S-EPMC6959597 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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The effects of extended photoperiod and warmth on hair growth in ponies and horses at different times of year.

O'Brien Christiane C Darcy-Dunne Megan Ruth MR Murphy Barbara Anne BA

PloS one 20200114 1

Photoperiod is considered the most dominant environmental cue allowing animals to anticipate and adapt to seasonal changes. In seasonally breeding mammals, changes in daylength alter pineal melatonin secretion and pituitary prolactin secretion. During the seasonal transition to shorter winter daylengths, increased production of melatonin and declining prolactin are associated with triggering winter coat growth in many animals. Similarly, studies have shown that artificial extension of photoperio ...[more]

PMID: 31935219

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Project description:Reasons for performing study. The prevalence of obesity in companion animals, including horses and ponies has risen drastically in recent years and risk factors have been little investigated. Horses are unique amongst companion animals in that many are outdoor-living and forage independently on pasture; they also have a dual utility and companionship role. The body condition of wild and free-living equines is known to vary seasonally, yet previous estimates of the prevalence of obesity and associated risk factors in domestic animals do not consider this. Most previous studies were conducted during the summer months when pasture quality is greater and obesity prevalence is likely to be highest. In addition, many previous estimates do not use validated body condition scoring methods and rely on owner reporting. Objectives. To examine the prevalence and risk factors predictive of equine obesity at both the end of winter and the end of summer, in a domestic population of leisure horses with daily access to pasture. Using validated body condition scoring methods and a single, trained observer. Methods. Body condition and belly girth measurements were taken at the end of winter and during the summer in a population of leisure horses (n = 96) with outdoor pasture access for ?6 h per day. Risk factor information was obtained by two owner questionnaires and analysed statistically using a mixed effects logistic regression model. The dependent variable was obese (BCS ? 7/9) or non-obese (BCS < 7/9). Risk factors associated with seasonal change in belly girth were also explored using a mixed effects linear regression model. Results. Obesity prevalence rose significantly from 27.08% at the end of winter to 35.41% during summer (p < 0.001). Breed was the risk factor most strongly associated with obesity (p < 0.001). Supplementary feed was not a strong predictor and there was no association with low intensity structured exercise. As winter BCS increased, the percentage seasonal change in belly girth decreased. Conclusions. Obesity prevalence differed between winter and summer in domestic equines. Supplementary feed and low intensity structured exercise in equines living outdoors for ?6 h per day had limited or no effect on obesity levels. Seasonal variation in body condition was lower in obese equines. Potential relevance. It is important to consider season when studying equine obesity and obesity-associated disorders. Risk factor analysis suggests preventative measures may need to be breed specific. The metabolic implications of a lessened seasonal change in body condition in obese animals, warrants investigation.

Project description:Fatty acids, as key components of cellular membranes and complex lipids, may play a central role in endocrine signalling and the function of adipose tissue and liver. Thus, the lipid fatty acid composition may play a role in health status in the equine. This study aimed to investigate the fatty acid composition of different tissues and liver lipid classes by comparing Warmblood horses and Shetland ponies under defined conditions. We hypothesized that ponies show different lipid patterns than horses in adipose tissue, liver and plasma. Six Warmblood horses and six Shetland ponies were housed and fed under identical conditions. Tissue and blood sampling were performed following a standardized protocol. A one-step lipid extraction, methylation and trans-esterification method with subsequent gas chromatography was used to analyse the total lipid content and fatty acid profile of retroperitoneal, mesocolon and subcutaneous adipose tissue, liver and plasma. Fatty acids were grouped according to their degree of saturation and their conjugated double bond into the respective lipid classes. In the adipose tissues, saturated fatty acids (SFAs) and n-9 monounsaturated fatty acids (n-9 MUFAs) were most present in ponies and horses. N-6 polyunsaturated fatty acids (n-6 PUFAs), followed by SFAs, were most frequently found in liver tissue and plasma in all animals. Horses, in comparison to ponies, had significantly higher n-6 PUFA levels in all tissues and plasma. In liver tissue, horses had significantly lower hepatic iso-branched-chain fatty acids (iso-BCFAs) than ponies. The hepatic fatty acid composition of selected lipid classes was different between horses and ponies. In the polar PL fraction, horses had low n-9 MUFA and n-3 PUFA contents but higher n-6 PUFA contents than ponies. Furthermore, iso-BCFAs are absent in several hepatic lipid fractions of horses but not ponies. The differences in fatty acid lipid classes between horses and ponies provide key information on the species- and location-specific regulation of FA metabolism, thus affecting health status such as inflammatory responses.

Dataset Information

The effects of extended photoperiod and warmth on hair growth in ponies and horses at different times of year.

Publications

The effects of extended photoperiod and warmth on hair growth in ponies and horses at different times of year.

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