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19. Metabolic adaptation in ponies in a cold climate
Abstracts/Livestock Production Science 40 (1994) 77~86
unlikely that this was due to the presence of horses. The two species shared habitat when grazing, but tended to stay separated when resting. Both species had special areas for grazing and others for resting. Resting places at night were not the same as during the day. Daily patterns of movement were discovered. Horses spent over 60% of the day grazing, 15-20% standing, 10% lying and 3-5% grooming. Precise patterns of resting were not found although rest seemed to be most likely in mornings and evenings. Behaviour of horses was not observed during nights. The sheep had two main resting and two main grazing periods, associated with sunrise and sunset. Out of 9 plant communities found in the area, sheep grazed mostly grassland and Kobresia heaths and horses grassland and bogs. Grasses were the biggest components of both sheep and horse diets. Horses ate more Cyperacea species and Equisetumpalustre, but sheep ate more forbs and Equisetum arvense. The sheep appeared to graze very selectively, preferring younger and shorter plants, but horses grazed taller vegetation as well as shorter. 17. Horse grazing in northern Iceland - behaviour and habitat selection. J. Magntlsson and A.G.
Thorhallsd6ttir. Hvanneyri Agricultural College, IS311 Borgarnes, Iceland. Grazing behaviour of horses was studied in northern Iceland on an area of 520 ha with several varied plant communities, including wet and drained bogs, dry heather, grasslands and ravines. A vegetation map of the area was made at the beginning of the study. Within the study area, 72 horses from local farms roamed freely from late July to the end of September. Their grazing behaviour was followed for two days, four times during the grazing period. During that time, the location and behaviour of each horse was recorded every two hours. On average, the horses spent 62% of their time grazing, 29% resting and 9% walking. Grazing time during daylight hours increased as the summer proceeded, from 54% in the beginning of August to 80% at the end of September. As the days got shorter in the autumn, the last grazing bout of the day started earlier and lasted longer. Different habitats were selected for different activities. The dry heather was only used for resting, while most of the grazing took place on the grassland and the drained bog, with the greatest grazing pressure on the border between these. More grazing took place in the wetlands earlier than later in the season. The
83
horse groups on the study area became fewer and bigger as the autumn approached. 18. Growth performance of Icelandic mares and their foals grazing a lowland mire. (5. Gudmundsson.
Agricultural Research Institute, Keldnaholt, IS-112 Reykjav~, Iceland. It is common knowledge that in Iceland lambs and calves do not thrive on lowland mires during summer grazing. However, it is assumed that horses do. To verify this a summer grazing experiment (from late June or early July to late September), lasting for 4 years, was conducted on a drained lowland mire in southern Iceland, with mares suckling foals, on low (L), moderate (M) and intense (I) stocking rates (average 0.46, 0.92 and 1.37 mares/ha, respectively). The vegatation was domminated by Carex nigra and Agrostis capillaris. In previous years it had been used for grazing experiments with cattle and sheep, giving unsatisfactory performance. The average in vitro digestibility and protein content of the herbage was 59.4 and 10.9% at the beginning and 41.9 and 7.7% at the end of the summer grazing, respectively. The average standing herbage left at the end of each summer grazing was 1.02, 0.84 and 0.43 tons/ha for the L, M and I stocking rates, respectively. The average liveweight of the mares was 360 and 382 kg and the foals 80 and 136 kg at the beginning and the end of grazing, respectively. In most years the liveweight gain of the mares was independent of stocking rates, whereas for the foals it decreased with increasing stocking rate, giving average daily gains of 263,504 and 105 g/mare/ day (P<0.001) and 834, 753 and 682 g/foal/day (P<0.001) at L, M and I grazing, respectively. The mares gained most during the early grazing period, but lost weight during September, whereas the foals grew fastest in the middle of the grazing season. It is coneluded that mares and their foals thrive well on drained lowland mires where the liveweight gain of young ruminants is unsatisfactory.
Sub-theme: management and health
19. Metabolic adaptation in ponies in a cold climate. H. Sigurdsson. Institute for Experimental Pathology, University of Iceland, Keldur, IS-112 Reykjavfk, Iceland. The Icelandic horse has for centuries survived under
84
Abstracts/Livestock Production Science 40 (1994) 77~g6
harsh conditions such as severe climate and poor and unreliable food supply. As a consequence they may have developed an efficient metabolism to survive. We observe that the Icelandic horses fatten very easily and quickly in the spring. The same is true in the autumn when the horses are preparing for the winter. Although they sometimes have to survive on withered grass through the whole winter, which does not meet their requirements for maintenance, they remain in good shape. Horses that are not allowed to fatten in the autumn when the grass is still green will have to be stabled early. From other countries we have the same observation that ponies fatten more readily than other breeds of horses. The hypothesis has been put forward that this difference in metabolic capability may be related to a basic tissue insensitivity to insulin in the pony when compared to the larger breeds. This causes a degree of insulin resistance in muscles resulting in a greather proportion of ingested carbohydrate being diverted to the liver where triglyceride synthesis is promoted and taken up by the adipose tissue, ensuring that excess of oxidisable substrate is stored as triglyceride. In other studies it has been proposed that this tissue insensitivity exacerbates the effect of stress induced cortisol release in the pathogenesis of both hyperlipaemia and lamnitis. These two diseases are registered in Icelandic horses. Most cases of lamnitis are registered in the spring when stabled horses are turned out to lustrous pasture. This supports the view that ingestion of new grass in the spring following a diet of hay and other roughages may be a causal factor in lamnitis together with a degree of insulin insensitivity. Hyperlipaemia is a metabolic condition which is mainly found in fat ponies and occurs in late pregnancy and early lactation. Hyperlipaemia has also been registered in Icelandic mares in late pregnancy. A tremendous increase in the mobilization of depot lipid leads to accumulation in liver and plasma. It is concluded that more basic research should be directed to the insulin metabolism in ponies and the effects of stress, e.g. due to disease, starvation and pregnancy, on this metabolism. 20. Time spent in shelter in relation to weather by two free-ranging thoroughbred yearlings during winter. P. Michanek and M. Ventorp. Department of Farm Buildings, Swedish University of, Agricultural Sciences, P.O. Box 945, S-220 09 Lund, Sweden. Two free-ranging thoroughbred filles, 8-10 months old, were used to study the utilization of a straw-bedded
shelter in winter in southern Sweden. During the experiment, temperature varied between + 10 and - 10°C and wind-speed ranged from 0 to 30 m/s. No natural wind or rain protection was available. The interior of the shelter was video-taped for 27, 24-hour periods. Temperature, wind and precipitation was recorded twice daily at 0700 and 1700 hours. The exact time spent inside the shelter was determined from the video recordings. The horses spent an average of 7 h and 25 min per 24-h period inside the shelter. They laid down in total for 4 h and 40 min. There were significant differences between day (0600-1800 h) and night (1800-1600 h) observations. During daytime the horses spent an average of 2 h and 56 min inside the shelter, with 1 h and 21 min in the lying position. The correlation between total time and time spent lying was 0.61. Rain significantly increased the time spent standing in the shelter and increasing wind was also associated with more time spent standing in the shelter during daytime. During the night, an average of 4 h and 30 min was spent in the shelter with 3 h and 20 min in the lying position. There was a correlation of 0.91 between time spent in the shelter and time spent lying. No significant correlation was found with weather. It is concluded that the need for a comfortable lying place was the main motive for the horses to use their shelter. Rain and hard winds increased the use of the shelter, but the need for weather protection was probably secondary to behavioral needs. 21. Disease problems in Icelandic horses. H. Sigurdsson. Institute for Experimental Pathology, University of Iceland, Keldur, IS-112 Reykjav~, Iceland. Disease problems in Icelandic horses are few compared to many other horse breeds, especially the fastgrowing breeds. Horses in Iceland have been isolated from other horses for over 1000 years. This creates the unique situation that most of the viral and bacterial contagious diseases have not been recorded in Iceland yet and therefore protective measures have been taken to try to preserve this situation. In Iceland, for instance, we do not have diseases such as influenza, herpesviruses (EHV), viral arteritis (EVA) and strangles. Contagious diseases are of rather little importance in Icelandic horses, although some bacterial and fungal diseases are registered sporadically, e.g. listeriosis, salmonellosis, tetanus and dermatophytosis caused by Tr/chophyton mentagrophytes. Most of the disease problems Icelandic veterinarians are dealing with are
unlikely that this was due to the presence of horses. The two species shared habitat when grazing, but tended to stay separated when resting. Both species had special areas for grazing and others for resting. Resting places at night were not the same as during the day. Daily patterns of movement were discovered. Horses spent over 60% of the day grazing, 15-20% standing, 10% lying and 3-5% grooming. Precise patterns of resting were not found although rest seemed to be most likely in mornings and evenings. Behaviour of horses was not observed during nights. The sheep had two main resting and two main grazing periods, associated with sunrise and sunset. Out of 9 plant communities found in the area, sheep grazed mostly grassland and Kobresia heaths and horses grassland and bogs. Grasses were the biggest components of both sheep and horse diets. Horses ate more Cyperacea species and Equisetumpalustre, but sheep ate more forbs and Equisetum arvense. The sheep appeared to graze very selectively, preferring younger and shorter plants, but horses grazed taller vegetation as well as shorter. 17. Horse grazing in northern Iceland - behaviour and habitat selection. J. Magntlsson and A.G.
Thorhallsd6ttir. Hvanneyri Agricultural College, IS311 Borgarnes, Iceland. Grazing behaviour of horses was studied in northern Iceland on an area of 520 ha with several varied plant communities, including wet and drained bogs, dry heather, grasslands and ravines. A vegetation map of the area was made at the beginning of the study. Within the study area, 72 horses from local farms roamed freely from late July to the end of September. Their grazing behaviour was followed for two days, four times during the grazing period. During that time, the location and behaviour of each horse was recorded every two hours. On average, the horses spent 62% of their time grazing, 29% resting and 9% walking. Grazing time during daylight hours increased as the summer proceeded, from 54% in the beginning of August to 80% at the end of September. As the days got shorter in the autumn, the last grazing bout of the day started earlier and lasted longer. Different habitats were selected for different activities. The dry heather was only used for resting, while most of the grazing took place on the grassland and the drained bog, with the greatest grazing pressure on the border between these. More grazing took place in the wetlands earlier than later in the season. The
83
horse groups on the study area became fewer and bigger as the autumn approached. 18. Growth performance of Icelandic mares and their foals grazing a lowland mire. (5. Gudmundsson.
Agricultural Research Institute, Keldnaholt, IS-112 Reykjav~, Iceland. It is common knowledge that in Iceland lambs and calves do not thrive on lowland mires during summer grazing. However, it is assumed that horses do. To verify this a summer grazing experiment (from late June or early July to late September), lasting for 4 years, was conducted on a drained lowland mire in southern Iceland, with mares suckling foals, on low (L), moderate (M) and intense (I) stocking rates (average 0.46, 0.92 and 1.37 mares/ha, respectively). The vegatation was domminated by Carex nigra and Agrostis capillaris. In previous years it had been used for grazing experiments with cattle and sheep, giving unsatisfactory performance. The average in vitro digestibility and protein content of the herbage was 59.4 and 10.9% at the beginning and 41.9 and 7.7% at the end of the summer grazing, respectively. The average standing herbage left at the end of each summer grazing was 1.02, 0.84 and 0.43 tons/ha for the L, M and I stocking rates, respectively. The average liveweight of the mares was 360 and 382 kg and the foals 80 and 136 kg at the beginning and the end of grazing, respectively. In most years the liveweight gain of the mares was independent of stocking rates, whereas for the foals it decreased with increasing stocking rate, giving average daily gains of 263,504 and 105 g/mare/ day (P<0.001) and 834, 753 and 682 g/foal/day (P<0.001) at L, M and I grazing, respectively. The mares gained most during the early grazing period, but lost weight during September, whereas the foals grew fastest in the middle of the grazing season. It is coneluded that mares and their foals thrive well on drained lowland mires where the liveweight gain of young ruminants is unsatisfactory.
Sub-theme: management and health
19. Metabolic adaptation in ponies in a cold climate. H. Sigurdsson. Institute for Experimental Pathology, University of Iceland, Keldur, IS-112 Reykjavfk, Iceland. The Icelandic horse has for centuries survived under
84
Abstracts/Livestock Production Science 40 (1994) 77~g6
harsh conditions such as severe climate and poor and unreliable food supply. As a consequence they may have developed an efficient metabolism to survive. We observe that the Icelandic horses fatten very easily and quickly in the spring. The same is true in the autumn when the horses are preparing for the winter. Although they sometimes have to survive on withered grass through the whole winter, which does not meet their requirements for maintenance, they remain in good shape. Horses that are not allowed to fatten in the autumn when the grass is still green will have to be stabled early. From other countries we have the same observation that ponies fatten more readily than other breeds of horses. The hypothesis has been put forward that this difference in metabolic capability may be related to a basic tissue insensitivity to insulin in the pony when compared to the larger breeds. This causes a degree of insulin resistance in muscles resulting in a greather proportion of ingested carbohydrate being diverted to the liver where triglyceride synthesis is promoted and taken up by the adipose tissue, ensuring that excess of oxidisable substrate is stored as triglyceride. In other studies it has been proposed that this tissue insensitivity exacerbates the effect of stress induced cortisol release in the pathogenesis of both hyperlipaemia and lamnitis. These two diseases are registered in Icelandic horses. Most cases of lamnitis are registered in the spring when stabled horses are turned out to lustrous pasture. This supports the view that ingestion of new grass in the spring following a diet of hay and other roughages may be a causal factor in lamnitis together with a degree of insulin insensitivity. Hyperlipaemia is a metabolic condition which is mainly found in fat ponies and occurs in late pregnancy and early lactation. Hyperlipaemia has also been registered in Icelandic mares in late pregnancy. A tremendous increase in the mobilization of depot lipid leads to accumulation in liver and plasma. It is concluded that more basic research should be directed to the insulin metabolism in ponies and the effects of stress, e.g. due to disease, starvation and pregnancy, on this metabolism. 20. Time spent in shelter in relation to weather by two free-ranging thoroughbred yearlings during winter. P. Michanek and M. Ventorp. Department of Farm Buildings, Swedish University of, Agricultural Sciences, P.O. Box 945, S-220 09 Lund, Sweden. Two free-ranging thoroughbred filles, 8-10 months old, were used to study the utilization of a straw-bedded
shelter in winter in southern Sweden. During the experiment, temperature varied between + 10 and - 10°C and wind-speed ranged from 0 to 30 m/s. No natural wind or rain protection was available. The interior of the shelter was video-taped for 27, 24-hour periods. Temperature, wind and precipitation was recorded twice daily at 0700 and 1700 hours. The exact time spent inside the shelter was determined from the video recordings. The horses spent an average of 7 h and 25 min per 24-h period inside the shelter. They laid down in total for 4 h and 40 min. There were significant differences between day (0600-1800 h) and night (1800-1600 h) observations. During daytime the horses spent an average of 2 h and 56 min inside the shelter, with 1 h and 21 min in the lying position. The correlation between total time and time spent lying was 0.61. Rain significantly increased the time spent standing in the shelter and increasing wind was also associated with more time spent standing in the shelter during daytime. During the night, an average of 4 h and 30 min was spent in the shelter with 3 h and 20 min in the lying position. There was a correlation of 0.91 between time spent in the shelter and time spent lying. No significant correlation was found with weather. It is concluded that the need for a comfortable lying place was the main motive for the horses to use their shelter. Rain and hard winds increased the use of the shelter, but the need for weather protection was probably secondary to behavioral needs. 21. Disease problems in Icelandic horses. H. Sigurdsson. Institute for Experimental Pathology, University of Iceland, Keldur, IS-112 Reykjav~, Iceland. Disease problems in Icelandic horses are few compared to many other horse breeds, especially the fastgrowing breeds. Horses in Iceland have been isolated from other horses for over 1000 years. This creates the unique situation that most of the viral and bacterial contagious diseases have not been recorded in Iceland yet and therefore protective measures have been taken to try to preserve this situation. In Iceland, for instance, we do not have diseases such as influenza, herpesviruses (EHV), viral arteritis (EVA) and strangles. Contagious diseases are of rather little importance in Icelandic horses, although some bacterial and fungal diseases are registered sporadically, e.g. listeriosis, salmonellosis, tetanus and dermatophytosis caused by Tr/chophyton mentagrophytes. Most of the disease problems Icelandic veterinarians are dealing with are