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Abstract:
Four trials were conducted utilizing two nonselected (randombred) and two selected (commercial broiler) stocks to investigate sex divergence in feed and water intake, and feed efficiency immediately posthatch. Although differences between sexes in body weight were not significant until 4 days of age, male:female ratios indicated that divergence in body weight started immediately posthatch and increased in a more or less linear fashion with age. At 14 days of age males were 7% larger than females (ratio 1.07) in both selected and nonselected stocks. The male:female ratios for feed intake followed the same general pattern as body weight ratios, starting at low levels immediately posthatch and increasing to the same approximate levels (ratio 1.07). Conversely, the male:female water intake ratios indicated that males consumed more water (4 to 9%) than females immediately following hatch and maintained constant rather than increasing ratios through 12 days. Feed efficiency and water:feed ratios were higher for males than females with the magnitude of the difference greater immediately posthatch. Data from these experiments indicated that both feed intake and feed efficiency are involved in the early body weight divergence between males and females.