In pregnant mares, peripheral insulin antagonism channels glucose preferentially to the foetus. On the other hand, horses reduce their metabolic activity in winter. Taking these aspects of equine pregnancy and metabolism together, we hypothesized that glucose clearance from blood and the insulin response to glucose do not only change throughout gestation but also with season. To test this hypothesis, the glucose and insulin response to an oral glucose test and relative insulin release were analysed in pregnant mares (n = 12) and in geldings (n = 10) as controls. Animals were tested in June, September, December, and in March (geldings) and on day 320 of gestation (mares). Furthermore, the 6 mares foaling early and 6 foaling later in the year were compared. In mares and geldings, plasma glucose concentration increased after glucose feeding (p < 0.001). The increase was more pronounced in mares (p < 0.05) and increased from June to December in mares (p < 0.001) but not geldings (month x group p < 0.05). This indicates constant glucose clearance in geldings but reduced clearance in pregnant mares. A partial insulin resistance is thus induced by pregnancy independent from season. Insulin release increased after glucose feeding (p < 0.001) similarly in geldings and mares. The insulin response to glucose and relative insuslin release increased from June to December (p < 0.001) indicating seasonal changes in β-cell sensitivity. Glucose and insulin concentration did not differ between early and late foaling mares. In conclusion, in horses, β-cell sensitivity to glucose is affected by season while insulin sensitivity during pregnancy decreases independent from season.

Pedigrees of a reference population of 1 659 North American Norwegian Fjord horses were traced to founders and analysed for coefficientsof inbreeding and genetic variability. Effective population size was 207.8 and there were 641 total founders. Pedigree completenesswas close to 100 percent for 6 generations, with 9.8 average complete generation equivalents. The average inbreeding coefficientwas 3.2 percent for the entire pedigree and 1.6 percent for pedigrees traced back five generations. Average inbreeding coefficients byyear of birth increased until 1983, before decreasing and then stabilizing through 2009. Effective number of founders, ancestors andgenomes were 96, 30.0 and 12.7, respectively. Low effective number of founders and ancestors indicate that genetic diversity has beenlost in the development of the breed in North America. However, registry-enforced breeding strategies have contributed to lowerinbreeding coefficients in the current generation.

The objective of this study was to estimate genetic parameters of foal inspection scores from the International Sporthorse Registry and Oldenburg Registry North America. Traits included type and conformation (TC), athletic ability of movement (AM), overall development (OD), total score (TS), and the binary trait premium status (PS). Fixed effects included sex, year of birth, year of birth by sex interaction, inspection period (1999 to 2005 or 2006 to 2009), breed of dam and breed of sire. Heritabilities and genetic correlations were estimated using an animal model. Approximately 27% of sires produced only one offspring and therefore their records were removed as they do not contribute information to genetic analyses. All trait means increased over time, with the most significant increase occurring from 1999 to 2003. Female foals exhibited significantly higher scores for all traits excluding AM. Mean scores were significantly higher in inspection period 2 than period 1. Offspring of warmblood dams were consistently scored higher than offspring of all other dam breeds. Offspring of Thoroughbred dams generally had higher scores than offspring of miscellaneous or unknown dam breeds. Percentage of foals named premium ranged from 32 to 56% and registry decisions to change the criteria for determining PS in 2008 have not significantly reduced this percentage. Heritabilities were estimated to be 0.45±0.05, 0.47±0.05, 0.49±0.05, 0.55±0.05, and 0.32±0.04 for TC, AM, OD, TS, and PS, respectively. Heritability of PS was 0.51 when transformed from the binary to the underlying normal scale. Genetic correlations among TC, AM, OD, and TS were extremely high and favorable (0.80 to 0.99). Overall, foal inspection scores appear to have the potential to strengthen the breeding program of these sporthorse registries, provided scored traits are favorably correlated with performance traits in adult horses.

Foal scores from the International Sporthorse Registry and Oldenburg Registry North America were used for statistical and genetic analysis. Scored traits include type and conformation (TC), athletic ability of movement (AM), overall development as related to age (OD), and total score (TS) calculated as a weighted average of TC, AM, and OD. Premium status (PS) was analyzed as a binary trait. Preliminary statistical analysis determined significant fixed effects of sex, year of birth, dam breed, and inspection period. Offspring of stallions with only one offspring in the dataset and nonwarmblood sires were deleted. Non-warmblood or non-Thoroughbred dams were also removed. Variance components were estimated using ASReml methodology to obtain genetic parameters. Traits were moderately to highly heritable with heritabilities of 0.45, 0.47, 0.49, and 0.55 for TC, AM, OD, and TS, respectively. PS had a heritability of 0.32 on a binary scale and 0.51 when transformed to the normal scale. Genetic correlations between TC, AM, OD, and TS were all high and favorable, ranging from 0.80 to 0.99. Genetic correlations with PS were inestimable. Foal inspection scores are heritable and should respond to selection. Selection for improvement in one trait should result in improvement in all traits. If genetic parameters can be correlated to data obtained in older horses, incorporating foal scores in selection decisions could improve warmblood breeding programs. Utilizing foal inspection scores should be beneficial to breeding objectives of the International Sporthorse Registry and Oldenburg Registry North America.