Document Type : Original Article
Authors
1
Department of Animal, Poultry and Fish Production, Faculty of Agriculture, Damietta University, Egypt
2
Animal Production Research Institute, Ministry of Agriculture, Dokki, Egypt
3
Department of Animal Production, Faculty of Agriculture, Zagazig University, Zagazig, 44519, Egypt
4
Department of Animal Production, Faculty of Agriculture, Suez Canal University, Ismailia 41522, Egypt
Abstract
The aim of this study was to estimate the effect of age at first calving (AFC) on first lactation traits (FLMY, FLP, FDO, FDP, and FCI), lifetime milk yield (LTMY), number of lactations complete (NLC), and profitability in Friesian cows under Egyptian conditions. Additionally, the study aimed to assess genetic parameters and breeding values to aid in genetic selection and improve dairy herd performance. Data were collected over 23 years from 1767 first lactation cows. A General Linear Model (GLM) in SAS was used to assess significant fixed effects, and restricted maximum likelihood (REML) procedures were applied to estimate genetic parameters and breeding values.
AFC significantly influenced productivity and reproductive traits. Cows with early AFC (≤25 -35 months) had higher LTMY (19881.25 ± 1248.6 kg) and NLC (4.58 ± 0.15) compared to cows with late AFC (≥46 months) (LTMY: 15343.5 ± 1430.55 kg, NLC: 2.87 ± 0.15). Profitability was highest in early AFC cows (39518.24 ± 2268.06 EGP), decreasing with delayed AFC. Heritability estimates ranged from 0.14 to 0.26 indicating potential for genetic improvement.
Breeding values were estimated for sires, cows, and dams with high accuracy. These values can guide genetic selection to enhance desired traits in Friesian cows, contributing to improved lifetime milk production and the number of lactations complete.
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