Vergleich verschiedener Aufzuchtintensitäten der Junghengstaufzucht und deren Einfluss auf Gesundheit und dauerhafte Leistungsfähigkeit (English shop)

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This basic study on the rearing of young stallions compared different rearing intensities of young stallions under practical conditions in order to determine their effects on the horse and its health as well as on lasting performance capacity. The impetus for this basic study was the fact that, over the past 20 years, high-intensity rearing systems have developed which are geared towards rapid physical development of young stallions with the aim of stallion licensing (Körung). In the course of this, individual farms have also specialised in stallion rearing.

In order to determine how a high rearing intensity affects the individual animal, metric, palpatory and descriptive data were collected from a total of 459 stallions on eleven Westphalian and Lower Saxon stallion-rearing farms. Furthermore, the distal radial epiphyseal plate of 110 stallions was radiographed in order to examine how different rearing intensities affect the timing of epiphyseal plate closure (EpFS). In the next step, 1,199 stallions from the eleven stallion-rearing farms which had been registered for pre-selection in the years 1996 to 2006/2007 were traced with regard to competitive sport and breeding aspects, in order to be able to make a statement on how different rearing intensities affect the lasting usability characteristics of the stallions. To obtain information on how the system of young stallion licensing is assessed by the members of the Westfälisches Pferdestammbuch e.V., an exploratory survey was conducted among them.

In addition, various methods (DXA, QUS, fpVCT, three-point bending test) for determining bone quality were compared with one another. The objective was to be able to use, in the medium term, a reliable parameter for determining bone quality that appears sufficiently sensitive to demonstrate, for example, possible effects of rearing intensity on bone.

In the course of the data collection, the eleven cooperating farms were characterised by means of a questionnaire on farm structures. On the basis of the age-corrected average live weight of the stallions, the stallion-rearing farms were classified into rearing systems of low, moderate and high intensity.

Metric, descriptive and palpatory data were collected from the stallions. It was found that the stallions from the intensive rearing systems had considerably higher daily weight gains than the stallions from the moderate and low-intensity rearing systems. Whereas linear growth patterns corresponding to rearing intensity could be observed for height, heart girth and body length, no differing developments of the measurements of the cannon bone and the fetlock joint attributable to rearing intensity were found.

The average time of EpFS, at 26.1 months, corresponded to the values known from the literature. The epiphyseal plates of the intensively reared stallions closed at 24.9 months and those of the stallions reared at low intensity at 27.1 months. In addition, the moderately and intensively reared stallions showed a considerably higher frequency of an irregular course of EpFS than the stallions reared at low intensity.

The frequency of alterations of the limbs in the intensively reared stallions was considerably higher than the frequency in the stallions reared at low and moderate intensity. Alterations in the area of the soft tissues or of the bony structures may be regarded as indicators of metabolic overload, for example due to highly concentrated feeding.

Of the stallions traced in order to examine lasting usability, one third were licensed; in relative terms, most of these came from a rearing system of moderate intensity. The duration of use defined by participation in competitive sport was highest in the intensively reared stallions, while the moderately reared stallions showed the highest average prize money earnings.

From the point of view of sustainable breeding selection, the low-intensity rearing system appears particularly successful. This system produced the most offspring per licensed stallion, as well as the most offspring with competition successes up to advanced level. The offspring of the stallions from the low-intensity rearing systems also had the highest lifetime earnings.

The breeders surveyed in the course of the survey on the assessment of stallion-rearing structures in Westphalia stated that in stallion rearing in recent years a strong specialisation has taken place, resulting in intensive preparation of young stallions for licensing. It was further stated that the genetic effects which are to be examined in the course of licensing are masked by environmental effects. For these reasons, the right horses were not always licensed and late-maturing lines had no chance. They criticise that the examination of actual breeding suitability is not in the foreground, but rather marketing. Alongside the positive assessment of the good organisation of the Westphalian licensing, more than half could envisage an alternative licensing system. This should be more strongly oriented towards the age-appropriate development of the stallions and take greater account of performance selection.

In the framework of the comparison of methods for bone density measurement, three methods established in human medicine (DXA, QUS, fpVCT) for determining bone quality were tested ex vivo on 19 equine metacarpi, which were subsequently broken in order to examine bone breaking strength. Bone breaking strength, which is regarded as an absolute parameter of bone quality, was measured by means of three-point bending. The only method for which a linear relationship to breaking strength could be established was the DXA measurement, which measures the mineral content of the bone. For the QUS and the fpVCT measurements no linear relationship to bone breaking strength could be established, but there was one between the two parameters themselves. From this it can be deduced that the methods mentioned measure similar quality parameters of bone, but not bone quality in the form of bone breaking strength.