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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Livestock Nutrient Management Research » Research » Publications at this Location » Publication #413627
Research Project: Strategies to Manage Feed Nutrients, Reduce Gas Emissions, and Promote Soil Health for Beef and Dairy Cattle Production Systems of the Southern Great Plains

Location: Livestock Nutrient Management Research

Title: A diverse diet increases animal growth performance and carcass yield of grazing lambs

Author
item Beck, Matthew
item GARRETT, KONAGH - Lincoln University - New Zealand
item MARSHALL, CAMERON - Lincoln University - New Zealand
item GREGORINI, PABLO - Lincoln University - New Zealand

Submitted to: Translational Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/28/2024
Publication Date: 7/10/2024
Citation: Beck, M.R., Garrett, K., Marshall, C.J., Gregorini, P. 2024. A diverse diet increases animal growth performance and carcass yield of grazing lambs. Translational Animal Science. 2024. Article txae103. https://doi.org/10.1093/tas/txae103.
DOI: https://doi.org/10.1093/tas/txae103

Interpretive Summary: Recent research has demonstrated that offering dietary diversity to growing lambs may improve wellbeing and growth performance relative to monotonous diets that are traditionally fed. However, most of these experiments were conducted with animals fed harvested forages. Accordingly, scientists from ARS (Bushland, TX) and Lincoln University (Lincoln, New Zealand) aimed to determine how offering swards composed of 5 forage species that are spatially separated influenced growth performance and carcass weight compared with lambs offered a monotonous sward. Two experiments were conducted over two years to determine the growth promoting benefits of offering a diverse diet composed of spatially separated sown strips of perennial ryegrass, plantain, chicory, broad-leaf dock, and alfalfa compared with monotonous diets of Italian ryegrass (experiment 1) or perennial ryegrass with white-clover (experiment 2). In experiment 1 the monotonous treatment group were stocked at a rate of 1,076-ft2 per lamb per week, while the diverse fed lambs were stocked at either 860, 1,022, 1,076, or 1184 ft2 per lamb per week. In experiment 2, the lambs were stocked at 1,318 ft2 per lamb per week, while the diverse lambs were stocked at 799 ft2 per lamb per week, on average. Lambs offered diverse swards in the 860 ft2 per lamb per week in experiment 1 and the lambs offered diverse swards in experiment 2 were allocated much less area, dry matter, crude protein, and metabolizable energy than the lambs offered monotonous swards, yet still had 34% or greater average daily gain and 13% or greater hot carcass weight. These results suggest that lambs will grow at appreciably faster rates when offered diverse swards, resulting in greater saleable carcass weight compared with lambs offered monotonous swards of Italian ryegrass or perennial ryegrass with white-clover.

Technical Abstract: The current experiments were conducted across two lamb finishing seasons [2019 (experiment one; Exp1) and 2020 (experiment two; Exp2)]. In both experiments lambs were provided a monotonous (MON) diet [annual ryegrass (Lolium multiflorum L.) during 2019 and perennial ryegrass (Lolium perenne L.) and white-clover (Trifolium repens L.) during 2020] or a diverse (DIV) diet composed of spatially separated strips sown to chicory (Chicorium intybus L.), plantain (Plantago lanceolata L.), perennial ryegrass, lucerne (Medicago sativa L.), and dock (Rumex obtusifolius). During Exp1, the DIV lambs had a stocking rate (SR) of either 80, 95, 100, or 110 m2/ram/week, whereas the MON lambs had a 100 m2/ram/week SR. In Exp2, the SR provided the rams was allocated in an to provide MON lambs with twice the forage allowance (kg DM/lamb/d) as DIV lambs. In Exp1, all rams provided DIV had a greater (P < 0.01) average daily gain (ADG; +130%) than MON rams, independent of the SR. Accordingly, DIV had greater (P < 0.05) hot carcass weight (HCW; +26%) and aged carcass weight (CW; +27%) compared with MON, across all SR. While the 80 m2/ram/week SR tended to have a greater (P = 0.10) dressing percentage and had similar (P = 0.29) drip loss percentage, the other lambs in all other DIV SR had greater (P < 0.05; +12%) dressing percentages and lower (P < 0.05) drip loss percentage than MON lambs. In Exp2, DIV lambs had a 37% greater (P < 0.01) ADG, a 15% greater (P < 0.01) HCW, and a 6% greater (P < 0.01) dressing percentage compared with MON lambs. This improved animal performance occurred despite being offered 57% less (P = 0.01) dry matter (DM), 56% less (P < 0.01) digestible DM, and 57% less (P = 0.02) metabolizable energy per lamb per d. Ultimately, these experiments demonstrate that providing growing rams a diverse diet improves animal performance, and carcass characteristics compared with a monotonous diet of annual ryegrass or a mixed sward containing perennial ryegrass with white clover.