Journal of Cell and Animal Biology Vol. 1 (4), pp. 066-070, November, 2007 Available online at http://www.academicjournals.org/JCAB ISSN 1996-0867 © 2007 Academic Journals Full Length Research Paper Within-herd phenotypic and genetic trend lines for milk yield in Holstein-Friesian dairy cows Khalid Javed*, Masroor Ellahi Babar and Muhammad Abdullah Department Livestock Production, University of Veterinary and Animal Sciences, Lahore, Pakistan. Accepted 29 th October, 2007 A total of 937 pedigree, breeding and performance records of 567 Friesian cows at the Livestock Experiment Station Bhunikey Dist. Kasur (Pakistan) spanning the years 1982-2001 were analyzed using Best Linear Unbiased Predictions procedure. Individual animal models were fitted to total milk yield from all lactations to estimate breeding values by Restricted Maximum Likelihood methodology. Milk yield and lactation length averaged 3391.66 ± 137.97 kg and 278.40 ± 90.17 days, respectively. The estimated breeding values for milk yield ranged from –354 to 503 kg. The corresponding values for the standing herd ranged from –209 to 294 kg. The genetic trend for milk yield was slightly positive indicating that the sires used during the last 20 years were of better breeding values. Phenotypic reduction in milk yield over time was observed, a probable reflection of the inability of the cows to adapt to the local environment and other environmental inadequacies. Key words: Friesian, pedigree, genetic, phenotypic, trend lines, Estimated Breeding Value (EBV), animal model INTRODUCTION Out of Pakistan’s 26 million heads of cattle (Anonymous, 2007), about 72% are of non-descript type. These animals are late-maturing and poor milkers. To improve their lactation performance, a crossbreeding programme with exotic temperate dairy breeds was initiated in the early seventies by importing frozen semen of Jersey and Friesian cattle. To cope with the demand of exotic cattle semen, a herd of 86 pregnant Friesian cows was also imported for the production of genetically superior bulls to ensure the regular and adequate supply of semen for crossbreeding in canal-irrigated areas of the Punjab and other parts of the country. About 4 - 5 generations of these imported cows have been produced in the sub- tropical environment of central Punjab. The genetic eval- uation of the performance of these animals has not yet been carried out. Ranking breeding animals according to their genetic merit for desirable traits adds value and efficiency in a breeding programme. Therefore, an accurate identification and genetic evaluation of breeding animals is of vital significance for genetic improvement. Estimated breeding values (EBVs) are estimates of the true *Corresponding author. E-mail: drjavedkhalid@yahoo.com. breeding value of an animal and Best Linear Unbiased Predictions (BLUP) procedure using the Individual Animal Model (IAM) is one of the global favourite methodologies for the prediction of breeding values of farm animals (Hill and Meyer, 1988). A graphic historical perspective of a within-herd breed- ing program using phenotypic and genetic trend lines can convey a quick assessment of a breeder’s selection success in previous generations. Trend lines may be used to compare alternative methods of selection or management for breeders involved with large herds. Trend lines may reinforce selection and management goals established by a breeder. However, such trend lines may also signal the need for changes in selection and/or management schemes. Trend lines resulting in a direction and (or) at a rate contrary to the anticipated result could mean that projected responses to selection were made with inappropriate assumptions or that expectations were too optimistic. Trend lines may also demonstrate how much (or little) selection was actually applied (Wilson and Willham, 1986). The aim of this investigation was to present the phenotypic and genetic trend lines of total milk yield and also to estimate the breeding values of the cows for comparative ranking within a purebred herd of Holstein- Friesian cattle in the Punjab Province of Pakistan. The