Parameters influencing body condition score of mares and foals

Abstract

Introduction: The New Zealand racing industry is a major contributor to the New Zealand economy. The large breeding industry in New Zealand encounters a significant commercial pressure to produce well grown colt foals for sale, as heavy and tall yearlings are expected to deliver better race performances at an earlier age. Nutrient supply to the fetus is the major regulator of fetal growth, and is dependent of several factors, including placental function and maternal nutrition. Nutritional status of the mare is believed to play a major role in fetal and foal development. Fatness of the horse can be determined by scoring the body condition. It is proposed that high body condition scored mares would produce foals with a higher body condition score than mares with a lower body condition score. Furthermore, parity and gestation length of the mare are also believed to be important factors in determining foal size and body condition at birth. The aim of this study was to determine the associations between mare body condition score, parity, gestation length and foal body condition score, wither height and growth rate. Materials and methods: Data were collected from two Thoroughbred stud farms. Mares and foals were body condition scored before, close after (within 3 days) and weekly up to 6 weeks after foaling. Foals wither height was measured close after birth and at 4 weeks of age. Official breeding data on mare age, mare parity, gestation length and last year of empty season were obtained from NZ Thoroughbred Racing. Pasture height was measured weekly using a rising plate meter and available energy calculated to assess if pastures met mares energy requirements. Results:Mean body condition of mares and foals close after birth was 4.70 ± 1.16 and 5.18 ± 0.81 respectively. Data from the 2009 season tended to show a linear relation between mare BCS (at foaling) and foal BCS (at birth) but this was not significant. The 2010 data were best described with a cubic relationship. However, there was no significance difference between foal BCS from thin mares and foal BCS from moderate mares (p=0.147), nor between foals from moderate and fat mares (p=0.079). There was no correlation found between mare BCS and foal withers height close after birth (p= 0.745). However, we found a significant correlation between mare parity and foal BCS (close after birth) (quadratic, R2=0.092. p=0.037) as well for parity and foals wither height at birth (cubic correlation, R2=0.150, p=0.023). There was a significant difference between foal BCS from primiparous mares and foal BCS from multiparous mares (p=0.001). Furthermore, these data demonstrate that there is a negative correlation between last year empty season and foal BCS at birth (R2 = 0.144, p = 0.001). No correlation was found between gestation length and foal BCS. Mare age did not affect mare and foal parameters. Interestingly, these data show that foals with low BCS (scored close after birth) gain body condition faster than fat foals do (negative linear correlation, R2= -0.301 en p=0.000), they will be at same level of body condition as foals which were fat at birth at 4 weeks of age. Conclusion: Foal BCS is related to mare BCS, however, mare BCS had no influence on foals withers height. Moderate mares tend to give birth to foals with higher BCS than foals from thin and fat mares.Parity and last year of empty season are important factors influencing foal BCS at birth. Primiparous mares give birth to foals with lower BCS than foals from multiparous mares. Furthermore, mares which have an empty season before a year in which they produce a foal will give birth to foals with lower BCS. Mare age is not an important factor determining BCS of the newborn foal. Important factors which affect foal BCS are hence mainly mare BCS, parity of mare and last year of empty season.