Using stepwise regression analysis to partition the variability in growth and some carcass traits in three lines of Japanese quail differing in genetic background

Abstract EN

Data of blood and/or plasma constituents of three weeks old Japanese quail were used to predict the growth and some carcass traits of 6 weeks old quail.

Stepwise regression analysis was performed to partition the variability in growth and carcass traits of three lines of Japanese quail differing in genetic background.

The first and second lines were selected over three generations for high six week-body weight (HBW6) and high 0-6 week growth rate (HGR0-6) respectively, whereas the third randombred control line (RC) was kept in order to facilitate comparison among lines.

The results cleared that the most important predictor for live body weight at six weeks of age (LBW6) in both males of RC and males of HGR was thyroxine (T4).

Both plasma total lipids and total proteins (TL and TP) were the best predictors for LBW6 for females of RC line.

Model 2 which used hemoglobin (Hb) and T4 was the best model for predicting LBW6 for males of HBW6.

Whereas, TL was the most important predictor for LBW6 for females of HBW6 line.

The most important predictors for feed conversion (FC) were TL and T4 for males of RC line, white and red blood cells (WBC and RBC) for females of RC, T4 and packed cell volume (PCV) for males of HGR0-6, triglycerides (TG) and TL for females of HGR0-6, TL and WBC for males of HBW6 and growth hormone (GH) and PCV for females of HBW6 line.

Performance index (PI) was predicted through TL and albumin (Alb) for males of RC, TP and GH for females of RC, T4 and PCV for males of HGR, TG and TP for females of HGR, TL and ratio of triiodothyronine to thyroxine (T3/T4) for males of HBW6 and TG and T3/T4 for females of HBW6.

For predicting dressing% in all studied groups, the most important predictors were T3/T4 and TP for males of RC, TP and GH for females of RC, ratio of T3/T4 and T3 for males of HGR0-6, Alb and TP for females of HGR0-6, PCV and RBC for males of HBW6, Alb and T3/T4 for females of HBW6, respectively.

Carcass% for all studied groups could be predicted using these predictors: PCV and GH for males of RC, GH and TG for females of RC, GH and RBC for males of HGR0-6, WBC and T3 for females of HGR0-6, T3/T4 and Hb for females of HBW6, respectively.

The most important predictors for boneless meat% (BLM) were RBC and TP for males of RC, Hb and Alb for females of RC, TG and T4 for males of HGR0-6, TP and T4 for females of HGR0-6, T3/T4 and Alb for males of HBW6 and TL and Hb for females of HBW6, respectively.

The major predictor in determining protein% for both males and females of the HBW6 line was T3.

The most important predictors for fat% were T3/T4, TL and TP in a descending order for males and females of the RC line and males of HBW6, respectively.

The predicted traits were insignificantly differed than the actual values or percentages (P>0.05).

Therefore, results of the stepwise regression analyses revealed that either certain studied hematological values or plasma constituents at three weeks of age in studied lines of both sexes could be used to predict carcass and growth productive traits in Japanese quail with high precision and low error.