Factors Affecting Growth Performance of Sahiwal Heifers in an Organized Herd

The present study was conducted to evaluate body weight and growth performance of Sahiwal female calves and to assess the effects of period, season, and birth weight. Data were collected over a ten-year period from 1996 to 2005. Body weights were recorded at birth and at 3, 6, 9, 12, 18, and 24 months of age. Growth rates were analyzed across six intervals: birth–3, 3–6, 6–9, 9–12, 12–18, and 18–24 months. The study period was divided into three phases (1996–1998, 1999–2001, and 2002–2005). Seasons of birth were categorized as summer (March–June), rainy (July–October), and winter (November–February), while birth weight was grouped into four classes (<17 kg, 17–19 kg, 20–22 kg, and >22 kg). A least squares model was applied using the R package emmeans (version 2.0.2) in the R programming environment (version 4.5.1). The overall mean body weights at birth, 3 months, and 6 months were 20.29 ± 0.14 kg, 40.52 ± 0.49 kg, and 76.48 ± 1.01 kg, respectively, while corresponding weights at 9, 12, and 18 months were 101.45 ± 1.42 kg, 134.29 ± 1.71 kg, and 197.42 ± 1.78 kg, indicating a steady growth pattern. Seasonal effects were largely non-significant during early growth, though some significant influence was observed at later stages, particularly on growth rates. Period of birth significantly affected body weights and growth rates at several stages, reflecting improvements in management, nutrition, and breeding practices over time. Birth weight had a significant effect on early growth (up to 3 months), but its influence diminished at later ages. Growth rates were highest during the mid-growth phases and gradually declined as calves approached maturity. Overall, the findings suggest that growth performance in Sahiwal calves is primarily influenced by management and environmental factors, while the effect of birth weight is limited to early life stages.

⓿ Period of birth significantly influenced body weight and growth rate, indicating continuous improvement in management, nutrition, and breeding practices over time.

⓿ Seasonal effects were generally non-significant during early growth but showed some influence at later stages, particularly on growth rates.

⓿ Birth weight affected growth only during the early stage (up to 3 months), with no significant impact on later growth performance.

⓿ Overall growth in Sahiwal calves was steady and primarily driven by management and environmental factors rather than initial birth weight.