An Approach of Estimating Individual Growth Curves for Young Thoroughbred Horses Based on Their Birthdays

Abstract

We propose an approach of estimating individual growth curves based on the birthday information of Japanese Thoroughbred horses, with considerations of the seasonal compensatory growth that is a typical characteristic of seasonal breeding animals. The compensatory growth patterns appear during only the winter and spring seasons in the life of growing horses, and the meeting point between winter and spring depends on the birthday of each horse. We previously developed new growth curve equations for Japanese Thoroughbreds adjusting for compensatory growth. Based on the equations, a parameter denoting the birthday information was added for the modeling of the individual growth curves for each horse by shifting the meeting points in the compensatory growth periods. A total of 5,594 and 5,680 body weight and age measurements of Thoroughbred colts and fillies, respectively, and 3,770 withers height and age measurements of both sexes were used in the analyses. The results of predicted error difference and Akaike Information Criterion showed that the individual growth curves using birthday information better fit to the body weight and withers height data than not using them. The individual growth curve for each horse would be a useful tool for the feeding managements of young Japanese Thoroughbreds in compensatory growth periods.

Effects of different winter climates in Japan on body composition of young Thoroughbreds in training

“…In conclusion, the higher rate of increase in FFM of Miyazaki colts suggests that training young Thoroughbreds in winter under mildly cold climate is more likely to mature earlier than severely cold climate [ 27 , 34 , 49 ], particularly in colts. The increased FFM in the Miyazaki colts suggests that the training may have been effective [ 12 ].…”

“…But after 2000s, indoor training facilities have been developed in Hokkaido, making it possible to train horses for fast work even in winter, regardless of weather conditions. In contrast, it has been reported that Thoroughbreds in Hokkaido at the “pre-training stage” have their growth suppressed during winters due to cold sensitization and other factors [ 27 , 34 , 49 ]. Training Thoroughbreds adequately during ‟the pre-training stage” is considered important for them to show their racing performance from the early 2 years of age [ 38 , 44 ].…”

A genome-wide association study for body weight in Japanese Thoroughbred racehorses clarifies candidate regions on chromosomes 3, 9, 15, and 18

“…Thoroughbred racehorses have been bred for improved racing ability, such as speed and stamina, which has led to variations in morphological traits such as body weight. This characteristic is used for confirming growth in humans and animals, and in Thoroughbred racehorses, it is measured at several occasions including postnatal, training, and racing periods to confirm growth and training degrees [ 13 , 14 , 15 , 16 ].…”