PSIV-8 - Effects of feeder lamb receiving protocols on lamb performance, feed efficiency and carcass characteristics as part of a lamb-value discovery program

Abstract: Minimizing interruptions in feed intake during the highly stressful receiving period is critical for lamb performance and animal welfare for lambs arriving from extensively managed operations. The objectives of the study were to evaluate feeder lamb receiving protocols, specifically the effectiveness of hay processing and respiratory vaccine on feed intake, growth performance, feed efficiency and carcass traits on a 107 d feeding trial. Sixty-three feeder lambs (BW = 47.6 ± 7.9 kg; wethers n = 46; ewes n = 17; Western white-faced n= 34; black-faced n= 4; crossbred n= 25) sourced from 15 WY and CO producers participated in the "Lamb-A-Year" program at the University of Wyoming- Laramie Research and Extension Center. Lambs were randomly sorted into two groups and fed an 8% CP, 61% NDF hay that was either unprocessed or processed (8 cm). Half of the lambs in each hay processing group were then vaccinated or not-vaccinated with a Mannheimia haemolytica Types 1 & 2 and Pasteurella multocida vaccine. Lambs were adapted to electronic feeders (Vytelle, Calgary, AB, CA) for 7 d (7 to 8 lambs/feeder) to record individual daily feed intake for 50 d. During the initial receiving period (d 0 to 14) lambs had ad libitum access to their respective hay treatment. A textured finishing diet was administered from d 15 to 50 (75% corn, 15% soyhulls, 10% lamb grower pellet). From d 51 to 107, lambs were group fed ad libitum the textured finishing diet until slaughter at a commercial abattoir. Hot carcass weight (HCW), 12^th rib back fat (RFT), body wall thickness (BWT), and loin muscle area (LMA) carcass data were collected at the abattoir. Data were analyzed as a mixed model with fixed effects of hay treatment, vaccination status, and their interaction with random effects of ranch source and individual animal. The hay treatment x vaccine status interaction was significant (P ≤ 0.03) for RFI. While the ranking changed for RFI when comparing vaccination status, no statistical difference between treatment groups were observed after a Tukey adjustment. Interestingly, the hay treatment x vaccine status interaction was significant (P ≤ 0.01) for BWT. Again, ranking did change, however no statistical differences were observed after a Tukey adjustment. Under current study conditions, there were no clear effects on dry matter intake (DMI), average daily gain (ADG), HCW, RFT, or LMA (Table 1). The effects of hay processing type and vaccine administration had minimal disruptions on DMI and ADG. Lamb performance may not be influenced by management interventions at the receiving phase. Further research should evaluate producer management prior to weaning and genetic factors that influence overall performance during the backgrounding and feeding phases.