Experimental Procedures
One hundred (50 ewes and 50 wethers) Targhee X Hampshire lambs (initial weight 61 ± 0.5 lb) were used in a randomized complete block design experiment. The experiment was blocked by both initial body weight (heavy and light) and lamb sex. Five diets were investigated: 1) 2/3 alfalfa:1/3 soyhulls; 2) 2/3 alfalfa:1/3 corn; 3) 1/3 alfalfa:2/3 soyhulls; 4) 1/3 alfalfa:2/3 corn; and 5) 1/3 alfalfa:1/3 soyhulls:1/3 corn. Alfalfa was 17% protein, alfalfa meal, and all ingredients were combined and pelleted. The trial began in April, 2000 and ended in June, 2000. Lambs were allotted to 20 pens with 5 lambs per pen and 4 pens per diet. Each diet was represented by a pen of heavy weight ewes, a pen of light weight ewes, a pen of heavy weight wethers and a pen of light weight wethers. Diet compositions are shown in Table 1.
Initial and final weights of the lambs were determined using the average of weights taken on two consecutive days, and 14-day intermediate weights were taken prior to feeding at 0800 hours. Average daily gain, DMI, feed efficiency (gain/feed), and days required to reach slaughter weight were determined for all lambs. Lambs were removed from the trial on a pen basis, as each pen reached the predetermined terminal weight (100 lb for ewes and 110 lb for wethers). The pens (5 X 16 ft) were constructed using expanded metal floors, with metal gates on three sides and a wooden fence-line feed bunk (5-feet long) on the fourth side. Each pen had an automatic water cup so that water was available at all times. Feed was provided ad libitum. Feed costs for lambs on each diet were calculated based on ingredient costs of $76.80/ton for corn, $114.00/ton for alfalfa meal, and $60.00/ton for soyhulls.
Statistical Analyses
Statistical analysis was performed using the GLM procedure of SAS (1988) for a randomized complete block experiment (blocked by sex and initial body weight). Pen served as the experimental unit. Treatment means were compared with the PDIFF statement of SAS (1988) when protected by a significant (P < 0.05) F-value.
