Abstract
The project aimed to collate the state of knowledge regarding lamb growth rates and identify constraints on individual lamb performance in feedlots. The key constraints on lamb growth rates were identified from a literature review and a series of experiments investigated growth rates and body composition of lambs under different nutritional and stage of lamb maturity treatments.
An experiment to assess the benefits of creep feeding and backgrounding was conducted; however, conclusive results were constrained by the low growth rates observed in a finishing period in the feedlot. Subsequent experiments sought to focus on the constraints in the feedlot.
The second experiment investigated the impact of feeding level and stage of maturity on growth rate, body composition and diet digestibility in a cohort of lambs. A third experiment investigated the effects of feeding lambs a pelleted diet with the fibre component incorporated compared to a pelleted diet with roughage fed separately on lamb growth and body composition. A separate cohort that grazed lucerne was included to compare the compositional changes between confinement fed and pasture fed lambs. Finally, modelling of lamb growth and body composition was conducted using body compositional data generated from CT scans in the second experiment. This compared the prediction accuracy of two published models with alternative methods for the estimation of heat production energy losses with the aim of supporting the development of a calculator that better reflects the realities of lamb growth by accounting for nutritional history and stage of maturity.
The results generated from this study indicate that providing lambs with a feedlot ration prior to feedlot entry may be a technique to increase feed intake and growth rates in the feedlot but more research is required to confirm this finding. Lambs fed high concentrate diets and in confinement, deposit a greater amount of empty body fat and decreased lean tissue in comparison to animals grazing pasture. The commonly reported phenomenon of compensatory growth was not observed in the current research, highlighting the importance of accurately predicting heat production energy costs to better predict growth responses. CT scanning of lambs demonstrated the technology’s advantages as a non-destructive method for repeated measures of body compositional changes in growing lambs.
An experiment to assess the benefits of creep feeding and backgrounding was conducted; however, conclusive results were constrained by the low growth rates observed in a finishing period in the feedlot. Subsequent experiments sought to focus on the constraints in the feedlot.
The second experiment investigated the impact of feeding level and stage of maturity on growth rate, body composition and diet digestibility in a cohort of lambs. A third experiment investigated the effects of feeding lambs a pelleted diet with the fibre component incorporated compared to a pelleted diet with roughage fed separately on lamb growth and body composition. A separate cohort that grazed lucerne was included to compare the compositional changes between confinement fed and pasture fed lambs. Finally, modelling of lamb growth and body composition was conducted using body compositional data generated from CT scans in the second experiment. This compared the prediction accuracy of two published models with alternative methods for the estimation of heat production energy losses with the aim of supporting the development of a calculator that better reflects the realities of lamb growth by accounting for nutritional history and stage of maturity.
The results generated from this study indicate that providing lambs with a feedlot ration prior to feedlot entry may be a technique to increase feed intake and growth rates in the feedlot but more research is required to confirm this finding. Lambs fed high concentrate diets and in confinement, deposit a greater amount of empty body fat and decreased lean tissue in comparison to animals grazing pasture. The commonly reported phenomenon of compensatory growth was not observed in the current research, highlighting the importance of accurately predicting heat production energy costs to better predict growth responses. CT scanning of lambs demonstrated the technology’s advantages as a non-destructive method for repeated measures of body compositional changes in growing lambs.
| Original language | English |
|---|---|
| Place of Publication | North Sydney, NSW |
| Publisher | Meat and Livestock Australia |
| Commissioning body | Meat and Livestock Australia |
| Number of pages | 107 |
| Publication status | Published - 22 Jan 2024 |