Specialized creep feeding for lambs to optimize performance

[摘要] ENGLISH ABSTRACT: The following study is to determine if a creep feed balanced for limiting essential amino acids (EAA) ata certain non structural carbohydrate (NSC) level will elicit greater responses than lambs reared on acommercial creep feed.Lysine, Threonine, Methionine, Isoleucine, Phenylalanine and Leucine were determined as thelimiting amino acids for nursing lambs. These amino acids were incorporated into the creep feedtreatments CF1 and CF2 representing 157 g CP/kg, 477 g NSC/kg and 179 g CP/kg, 508 g NSC/kg,respectively. A commercial creep feed with no optimisation for EAA is represented as CFC with 139 gCP/kg and 455 g NSC/kg. A negative control (CON) treatment represents lambs receiving no creepfeed but with ad libitum access to suckle their dams while feeding on kikuyu pasture.A growth trial was conducted on Merino x Döhne-Merino cross twin lambs averaging a birth weight of4.42 kg ± 0.11 for 60 days following with a digestibility trial towards the end of the trial. Half of thelamb crop was slaughtered at an average live weight of 23.6 kg ± 0.56. The M. longissimus dorsi wasremoved on both the left and right half of the carcass between the 2nd - 3rd last thoracic vertebrae andthe 4th - 5th lumbar vertebrae. A sample from the rumen wall was taken at the rumino-reticular fold todetermine development characteristics.Results indicate that the feed conversion ratio for the CFC lambs were better than CF1 (P = 0.052)but not more than CF2 (P = 0.307). The FCR was 0.88, 1.19 and 1.01 (kilogram feed required to gain1 kg in bodyweight) for CFC, CF1 and CF2, respectively. Dressing percentage was higher for CF2than for both CFC (P = 0.012) and CF1 (P = 0.077). Along with BUN data it was concluded that thehigh CP level of CF2 resulted in the higher fat deposition. The optimised creep feeds had highernitrogen and energy balances than the commercial CFC, this implicates that the optimised creepfeeds were more efficiently utilised. Optimised creep feed treatments had longer papillae than CON (P< 0.0001). Papillae of creep feed 2 was longer than CFC (P = 0.0537). Papillae width decreased asthe NSC level increased thus it is surmised that higher NSC levels resulted in longer but thinnerpapillae. Rumen muscularization was equally developed between all the treatments and was ascribedto the lambs' access to course roughage. Meat quality in terms of physical and chemicalcharacteristics was found to be in range with that expected for lambs at higher slaughter weights (40kg). In conclusion, the balancing of the limiting EAA increases the benefits of creep feeding whilesimultaneously being more efficiently utilised. Intensive sheep production systems may benefit fromthe feeding of such creep feeds provided it fits economically into their farming system.

[发布机构] Stellenbosch University