Epsilon Open Archive

Abstract

The Reyna Creole cattle in Nicaragua is a local breed originating from the Bos taurus cattle brought to Latin America during the Spanish colonization in the fifteenth century. Reyna Creole cattle are today found in five herds. The primary use of the breed is to produce milk. The breed comprises about 650 purebred female animals. The main objective of the thesis was to characterize the population structure and productivity in terms of milk production and some reproduction traits, and to discuss options for conservation and improvement of the breed.

The inbreeding level was 13% on average, primarily due to use of individual bulls for long periods. An effective population size of 28 to 46 animals was estimated, showing that the Reyna Creole cattle breed is endangered, close to critical status.

Average birth weight was 27.8 kg, age at first calving 37.4 months and calving interval 14.0 months. Large differences between herds were observed for all traits. Heritabilities were 0.34, zero and 0.20 for the respective trait. Average lactation yield for 534 Reyna cows with 1,750 lactations was 1,319 kg with large variations between herds and time periods. Test-day records on milk yield and fat and protein contents were collected monthly during one year for three Reyna herds and two herds with crossbred cows. Commercial dairy breed crosses had the highest production, and Reyna the lowest, but large differences were noted in management between the herds. The heritability for lactation yield in Reyna cattle was 0.18.

Large variation between and within the Reyna herds suggest good opportunities to increase productivity of the Reyna breed by improving management and breeding strategies. It is proposed to keep all females in the herds, develop mating plans and to apply a recording scheme for keeping pedigrees and records on reproduction and milk production traits. Only young bulls, selected from the best cows for milk production and calving interval, are proposed to be used for 1-2 years each to manage inbreeding and keep generation intervals short.