382
Effect of energy source, level, and sex on growth and performance of lambs
The objective of the study was to compare ad libitum or restricted intake of whole shelled corn (WSC) versus alfalfa pellets, and the sex of lamb, on lamb growth and performance. Ewe (n=48) and wether (n=48) lambs were blocked by sex and stratified by initial weight to pen. The three diets were ad libitum WSC (AC), 85% of ad libitum intake WSC diet (LC), or an ad libitum alfalfa pellet diet (AA). There were 4 lambs per pen, and 8 replicate pens per dietary treatment. Ewe and wether lambs were removed from the study when pens reached an average weight of 59.0 and 63.5 kg, respectively. Statistical analysis was conducted using PROC MIXED statement in SAS with diet and sex as fixed effects, diet and sex nested within pen as the random effect, and initial weight interactions and final weight were used as covariates if P < 0.20. For daily DMI, gain efficiency, and feed cost of gain data, pen averages were used for the analysis and the random effect was removed. Initial and final weight covariates were the deviations from the average ewe or wether weights. The LSMEANS and DIFF statements were used to distinguish significant (P < 0.05) differences between treatments and record the standard error. Average daily gain (ADG) of lambs fed the AC diet was greater (P < 0.001) than lambs fed the LC and AA diets, which resulted in fewer (P < 0.01) days on feed for AC fed lambs. Lambs consuming the AA diet had greater (P < 0.001) DMI than lambs fed the AC or LC diets. Wether lambs had greater (P < 0.01) DMI compared to ewe lambs. Gain efficiency was greatest (P < 0.001) for lambs fed AC, followed by lambs fed the LC diet, and finally the AA diet. Whole shell corn cost $0.15/kg, alfalfa pellets cost $0.60/kg, and supplements cost $0.51/kg on an as-fed basis. The resulting feed cost of gain was greatest (P < 0.001) for AA fed lambs, followed by LC fed lambs, and lastly AC fed lambs. There was a trend (P = 0.06) for ewe lambs to have a lower feed cost of gain than wethers. The AC diet resulted in the most efficient gain, fewest days on feed, and the lowest feed cost of gain.
Key Words: energy source, growth, lambs