Research Briefs

18 June 2008

As part of a programme to quantify the Thoroughbred production process in New Zealand researchers at Massey University have recently conducted a number of surveys examining feeding, management of thoroughbred racehorses and general stud farm management. In a related project in collaboration with Dr Arpad Bakor from Hungary a mathematical model of foal growth has been developed. These data provide opportunity for the industry to benchmark current practices and measure the impact of new feeding and management strategies on growth and production.

How Thoroughbred racehorses are fed in New Zealand

Data were collected from Thoroughbred racehorse trainers in the Auckland, Waikato and Central districts. The trainers were asked a series of question on the feeding and management of their horses. Faecal samples were taken from a sample of horses to indirectly evaluate any hindgut acidosis associated with a high grain diet.

In contrast to the belief that many New Zealand racehorses are pasture trained, the majority of racehorses surveyed (95%) spent most of their time in stables or yards for more than 12 hrs per day . Fifity three percent of racehorses were fed a combination of grains and commercial pre-mixes, whilst 32 % were fed just commercial pre-mixes and 14 % were fed grain as the only source of concentrate. Horses fed only grains were fed more grain than the other two groups (6.1kg / day vs. 5.1kg / day) and tended to have a faecal pH indicative of some hindgut acidosis (pH 6.2). Irrespectively of the concentrate fed, the feeding of at least 2.25 kg of hay twice per day reduced the number of horses with faecal pH indicative of hindgut acidosis. Therefore it would appear that irrespective of management system it is important to feed at least 2.25 kg of hay/day ad libitum, to buffer hindgut acidosis associated with diets high in soluble carbohydrate.

To view the article published in New Zealand Veterinary Journal

General stud farm management

Data were collected from 22 stud farms located in the South Auckland/Waikato region (n=15) and lower North Island (n=7) of New Zealand, using a face-to-face survey. The stud master provided information on the size, scope and management of the farms during the 2004/2005 breeding season. Analysis was based on the location of the farm and size of the breeding operation (number of resident mares).

The effective farm size ranged from 20 to 526 ha and averaged 167 and 88 ha in the South Auckland/Waikato and lower North Island areas, respectively. The typical farm had 3 stallions and 50 wet mares and 21 dry mares at the time of the survey.

Seventy-one percent of farms aimed to breed dry mares early in the breeding season, and used a combination of lights, hormone therapy, and rising plane of nutrition to achieve this. Foaling took place in foaling paddocks with most farms (77%) using a night foaling attendant and 22% of farms using a foaling alarm.

At birth, 77 % of stud masters routinely administered antibiotics; 64% administered tetanus antitoxin; 41% administered an enema to foals and only 9% did not routinely administer prophylactic treatments. On average, weaning occurred at 5 months of age and on 73% of farms foals were confined to a box for 1–2 weeks. Weaned foals were drenched with anthelmintics every 7 weeks and were fed on average 2.9kg of concentrate feed while at pasture until yearling preparation began,; on average 13 weeks before the sales. Eight farms weighed the weanlings, at least monthly, to monitor growth.

The management of Thoroughbred horses was relatively consistent throughout the regions surveyed. Utilisation of breeding stallions tended to be more efficient on the larger stud farms in the South Auckland/Waikato region.

To view the article published in New Zealand Veterinary Journal

Modelling foal growth

In order to measure the impact management changes have on foal growth it is important to have a growth model to which growth rates and body weights can be compared. The ability to grow foals successfully with a pasture-based production system is a unique opportunity for Thoroughbred breeders in New Zealand. Therefore, it is important the breeders have access to a growth model that has been developed using data from foals grown under a typical New Zealand production system.

In this study, twice monthly weight records, collected from a thoroughbred stud farm over a 6 year period, were used to model foal growth up to when the foals were weaned. Within this dataset colts and fillies grew at similar rates; the largest impact on foal weaning weight was the age at weaning and the foal's birth weight. The most accurate model of foal growth to weaning was a Brody’s equation LW = [b0– (b0–BW) x e(–b1 x age)], and an equation including BW: LW = [((b0 x BW x age) + BWb1)b2], that was developed in this study (b0 is an intercept, b1 and b2 are regression coefficients, and e is the base of natural logarithms). These models describe rapid growth up to the first month and less rapid rate of growth with increasing live weight up to weaning. The typical average daily weight gain of New Zealand Thoroughbred colts and fillies were:

Colt: ADG (kg/day) = 1.819–0.00443 x Live weight
Filly: ADG (kg/day) = 1.896–0.0050 x Live weight


Figure 1. Scatterplot of the liveweight data (n=3,200) of 218 Thoroughbred foals from birth to weaning.

To view the article published in New Zealand Veterinary Journal


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