Monitoring Milk Yield and Composition Traits in Holstein Friesian Crosses: Influence of Blood Level, Location, Lactation Stage, and Parity

This study evaluated the effects of genotype (G), parity (P), lactation stage (LS), and location (L) on milk yield and composition of Holstein Friesian (HF) crossbred dairy cows in the Shashemene–Dilla milkshed. A total of 117 lactating cows (39 per location: Shashemene, Hawassa, and Dilla) were included, comprising three genotype groups (50%, 75%, and 87.5% HF; 13 cows per genotype per location). Milk yield traits assessed were peak yield (PY), total yield (TY), lactation length (LL), peak day (PD), and average daily milk yield (ADMY). Milk composition traits; fat, protein, lactose, milk density (MD), salt, pH, freezing point (Fpt.), and total solids (TS) were determined using a Milkoscan FT2. Data were analyzed using a linear mixed-effects model in R (version 4.3.3). GraphPad Prism (10.4.0) was used to visualize milk production, while Origin software illustrated changes in ADMY across lactation stages by genotype. Results showed that 87.5% HF crosses outperformed 75% and 50% HF cows in ADMY, TY, PY, LL, and PD. In contrast, 50% HF cows exhibited higher MD, TS, protein, Fpt., and salt content, whereas 75% HF cows had the highest fat percentage. Location significantly affected MD, Fpt., and salt (P < 0.05), with significant genotype × location interactions observed for MD, TS, protein, and solids-not-fat. Lactation stage significantly influenced fat, MD, TS, protein, and salt (P < 0.001), while parity affected all yield traits except PD. ADMY was negatively correlated with fat (r = -0.22) and TS (r = -0.22). Protein showed strong positive correlations with density (r = 0.86) and lactose (r = 0.63), while solids-not-fat was strongly associated with density (r = 0.76). Overall, higher HF inheritance improved milk yield, although production was strongly influenced by location. Strategic selection based on performance records and improved management practices is recommended to enhance productivity under smallholder systems.