Nutritive value and the maximum inclusion level of pennycress meal for broiler chickens
Two experiments were conducted to evaluate the nutritive value and maximum safe level (MSL) of pennycress meal (PM) for broiler chicks. In experiment 1, a total of 480 chicks was fed either mash or crumbled diets containing zero, 5, 10, or 15% PM for 18 d (8 diets; 6 replications per diet). In experiment 2, a total of 660 chicks was fed mash diets containing zero, 3, 6, 9, 12, or 15% of either PM or canola meal (CM; a comparative reference) for 14 d (11 diets; 6 replications per diet). Analytical results show that PM is a good source of protein (˜31% CP) and it is very comparable to CM (˜36% CP). However, it contains higher erucic acid (˜1.68 vs. < 0.021%), glucosinolates (sinigrin) (˜63.5 vs. <0.163 μmol /g), and crude fiber (18.60 vs. 9.27%) compared to CM. In experiment 1, increasing PM from zero to 15% resulted in linear reductions (P < 0.05) in FI, BWG, and FCR at 10 days. Above 10%, performance responses were affected for FI and BWG at 18 d, respectively. An estimated MSL of 10% PM based on orthogonal contrast was optimal for satisfactory FI and BWG. The MSL as estimated by broken-line linear (BLL) and broken-line quadratic (BLQ) models was 9.12 ± 0.50 and 7.0 ± 1.27%, respectively. In experiment 2, growth performance at 14 d was reduced above 9% due to PM inclusion. CM inclusion did not affect growth performance at 14 d, suggesting 15% to be safe. The MSL for maximum growth performance varied depending on the statistical analysis as follows: 12% by orthogonal contrast and LSD, 15% by the Scheffé test, 10.84 ± 0.57 by BLL, and 8.61 ± 1.29 by BLQ. In conclusion, PM can be included in broiler starter diets as a protein source but its inclusion should be limited to no more than 8.5%. Different statistical procedures give different MSL and this should be considered when interpreting the data.