Interrelationships among water quality, climate and diet on feedlot performance of steer calves.

Four experiments involving 16 pens of 8 to 10 crossbred steer calves each were conducted at Yuma, Arizona. Initial and final weights were approximately 170 and 275 kg, respectively. The experimental design was a 2 x 2 x 4 factorial replicated over 2 yr with main effects for season (summer, winter), diet (H = ground alfalfa hay, H + G = 50% ground alfalfa, 47.5% dry-rolled wheat and 2.5% molasses) and water source (N = normal, S = saline) during two consecutive 56-d periods in each experiment (N-N, N-S, S-N, S-S). Normal water contained approximately 1,300 ppm, and saline water contained approximately 6,000 ppm, total dissolved salts. Steers on the H + G diet gained 32% faster (P less than .01) and consumed 4% less (P less than .01) feed than those on the H diet. Gain and feed intake during winter were greater than during summer (20% and 7%, respectively, P less than .01). Gain and feed intake were reduced approximately 9% (P less than .01) on S water combinations compared with N-N water. Depression in gain and feed intake due to heat stress (summer season) or S water ingestion was greater on the H diet (diet x water source and diet x season interactions, P less than .02). Although season x water source interactions were not significant, saline water ingestion tended to be more detrimental during periods of heat stress (summer). Apparent adaptation to saline water occurred on the H + G diet, but not on the H diet.(ABSTRACT TRUNCATED AT 250 WORDS)