Prediction of first lactation 305-day milk yield (305 DMY) of Sahiwal cattle from body measurements
Prediction using one independent variable
The linear regression equations of first lactation 305-day milk yield for different body measurement traits taking single independent variables have been presented in Table 1. The R² values for predicting 305 DMY from birth weight and body measurements
i.e., body length (BL), heart girth (HG) and height at withers (HW) at 3, 12, 18, 24 months and AFC were non-significant, indicating these measurements are not useful for prediction of 305 DMY at this stage. The R² value for predicting 305 DMY was better from HG alone at different ages compared to other individual measurement.
The present study revealed that heart girth (HG) had a significant and positive association with milk yield in dairy cows, which is in agreement with previous research highlighting the importance of HG in predicting production performance. However other body measurements did not show significant prediction of first lactation 305 DMY, which was supported by previous findings of
Mishra et al., (2017). The current findings align with
Alsheikh (2013), who reported that morphometric traits in Shami goats, including HG, could aid in predicting daily milk yield (DMY). Similar findings were noted by
Dahiya and Rathi (2002) in indigenous cattle,
Ahmad et al., (2013) in Nili-Ravi buffaloes and by
Ahlem et al., (2022) in goats.
Body measurements such as stature and heart girth (HG) are well-established indicators of body weight
(Heinrichs et al., 1992; Mantysaari, 1996), which is closely linked to metabolic capacity, feed efficiency and energy balance (
Søndergaard et al., 2002). Larger-framed animals with greater HG possess enhanced thoracic capacity, supporting better-developed heart and lungs, improved circulation and respiratory efficiency, all of which contribute to higher milk production (
Bais, 2023). HG also serves as an indicator for biological capacities related to lactation (
Durón-Benítez and Huang, 2016) and reflects changes in body condition during lactation, underscoring its value as a selection criterion for dairy productivity improvement
(Dijkstra et al., 2005).
Prediction using two independent variables
The linear regression equations of first lactation 305-day milk yield for different body measurement traits taking two independent variables have been presented in Table 2. At 6 and 9 months and also at AFS, the R² values for predicting 305 DMY from combinations of HG with BL and HW showed higher prediction efficiency. For ages 3, 12, 18, 24 months and AFC the R² values for various body measurement combinations were non-significant, suggesting these measurements are not useful for predicting 305 DMY at these ages.
The regression analysis using two independent variables showed that HG in combination with BL and HW provided better prediction at 6 and 9 months of first lactation 305 DMY. In line with the present findings
Alsheikh (2013) reported that HG combined with withers height and hip height improved accuracy, reaching an R² of 80% in joint models of does and kids. Similar findings were reported by
Ahmad et al., (2013) and
Dhillod et al., (2017) in buffalo, while in goats were noted by
Kouri et al., (2019) and
Makamu et al., (2023). Heart girth reflects thoracic capacity, impacting intake, digestion, respiratory efficiency, enhancing metabolism, oxygenation and overall productivity (
de Melo et al., 2018). Moreover, the present findings showed a negative relationship of 305 DMY with HW and BL. In line with the present findings
Mota et al., (2014) reported that negative canonical correlations of BL and HW with lactation length (LL) suggest that smaller buffalo may have longer lactation periods due to lower maintenance energy requirements.
de Melo et al. (2020) also reported body morphometric traits like BW had higher cross-loadings for milk and reproductive traits. Conversely,
Sieber et al., 1988; Ahlem et al., (2022) found that wither height had a positive correlation (P<0.05) with yield traits during the first parity which supported the present findings.
Prediction using three independent variables
The multiple linear regression equations of first lactation 305-day milk yield for different body measurement traits taking three independent variables have been presented in Table 3. The results revealed that HG alone and particularly in combination with BL and HW, provides the most consistent predictive value for 305 DMY at earlier ages.
In agreement to the present findings
Dhillod et al., (2017) stated that HG and BL were reliable predictors of milk yield and recommended using these parameters as selection criteria in breeding programs to improve milk productivity. Similar findings were noted by
Lin et al., (1987), who reported that selecting animals for higher milk production resulted in proportional increases in BL, HG and HW, indicating their strong association with productive potential.
Singh and Prasad (1983) also demonstrated significant correlations between these measurements and milk yield in both cows and buffaloes, reinforcing their predictive value across breeds and species.
Bhakat et al., (2010) further observed strong correlations between HG and abdominal girth, suggesting that these traits are interconnected indicators of overall body capacity. Supporting this,
Kumar et al., (1995) reported that multiple linear regression using BL, HG and HW explained 12.8% of the variation in 305 DMY, highlighting their utility in early selection programs for dairy cattle. However,
Mishra et al., (2017) observed non-significant effect of body measure-ments on first lactation milk yield in Jersey and Holstein Friesian crossbred cattle.
The present findings revealed that HG along with BL and HW, provides the most consistent predictive value for 305 DMY at earlier ages, making it a practical trait for field-level evaluation. This association is likely because HG serves as a reliable indicator of body size, which directly correlates with rumen capacity and the efficiency of energy intake and utilization in dairy cows
(Sloniewski et al., 2005). A larger HG generally signifies greater thoracic and abdominal volume, enabling higher feed intake and enhanced digestive efficiency
(Kennedy et al., 1999). This in turn leads to improved nutrient absorption and utilization, supporting increased metabolic activity and energy turnover (
Oldham, 1996). Such physiological advantages facilitate greater energy availability for milk synthesis, thereby explaining the higher yields observed in cows with larger heart girth.
In the present study, BL, when combined with HG and HW, showed improved prediction of 305 DMY compared to using BL alone. This was supported by previous findings of
Zujović et al. (2011),
Ahmad et al., (2013), Dhillod et al., (2017) and
Makamu et al., (2023). Lin et al., (1987) reported that selection for higher milk production increased BL, HG and HW simultaneously which is in agreement with the present findings. According to
Soeharsono et al., (2020), BL shows only a weak correlation (r = 0.15) with daily milk production, explaining just 2.31% of the variability (R²). This suggests that while BL contributes to milk yield prediction, it is not a strong independent predictor.
Hamid et al., (2003) reported that BL, PG and HG together explained 12.9% of the variation in first lactation milk yield and when BL was excluded, the remaining traits explained 12.3%, indicating that BL added only marginal predictive value. However,
Petrovska and Jonkus (2014) emphasized that BL influences small intestine size, which is vital for digestion and nutrient absorption. Longer BL is associated with greater absorptive capacity, which may enhance nutrient utilization and support higher daily milk production. These findings underline that while BL can be a valuable component when used alongside other body measure-ments like HG and HW, its influence on milk yield is more pronounced in combination rather than isolation.