Lamb growth rates and carcass characteristics of White Dorper and crossbred lambs grazing traditional and novel pastures during spring in southern Australia

Context Finishing lambs on pasture and specialist forages is a commonly used production system in southern Australia; however, there is little information properly comparing multiple pasture options for lamb production. Aim We aimed to compare growth rates of lambs when grazing traditional pastures, novel legumes, or a herb–legume mixture. Methods Six pasture and forage treatments were sown in three replicate 0.4-ha plots and with access to irrigation. Treatments were French serradella (Ornithopus sativus Brot.), bladder clover (Trifolium spumosum L.), forage brassica (Brassica napus L.), lucerne (Medicago sativa L.), lucerne + phalaris (Phalaris aquatica L.), and arrowleaf clover (Trifolium vesiculosum Savi) + chicory (Cichorium intybus L.). The last two treatments were sown in a 1:1 alternate sowing-row (tyne) arrangement. All plots were grazed concurrently from 15 October to 2 December 2014, each plot with a mixed-sex group of 13 weaned lambs: five White Dorper, three White Suffolk × White Dorper and five White Suffolk × Merino lambs. During the grazing period, lambs were weighed each week following an overnight curfew. Starting liveweight (mean ± s.d.) was 32.4 ± 5.5 kg. At the completion of the grazing period, lambs were slaughtered and carcass traits recorded. Key results Lambs grazing arrowleaf clover + chicory had the highest average daily growth rates (ADG) (245 g/lamb.day) and those grazing lucerne + phalaris the lowest (119 g/lamb.day). There was a lag in ADG for the forage brassica treatment over the first 14 days of grazing, and lamb growth plateaued for the bladder clover treatment toward the end of the trial. Overall, ADG for the forage brassica and bladder clover treatments was similar to that for lucerne. Lambs grazing French serradella had similar ADG to 18 November compared with those grazing other treatments, except arrowleaf clover + chicory; however, lambs grazing French serradella were withdrawn from the experiment on 26 November after losing weight. The genotype × treatment interaction was significant for final liveweights, with White Suffolk × White Dorper lambs having higher predicted final liveweight on the arrowleaf clover + chicory pasture (45.2 kg) than White Dorper (43.8 kg) and White Suffolk × Merino (44.0 kg) lambs, and higher liveweight on lucerne than White Suffolk × Merino lambs (42.6 vs 41.4 kg). White Dorper lambs had a higher overall sale value owing to their higher dressing percentage. The proportion of lambs reaching the finished weight target was higher for arrowleaf clover + chicory (0.96) than for any other treatment. Conclusions and implications Using a forage option that maintains high levels of production and quality later in spring can increase the proportion of lambs reaching target weights and the final sale weight of lambs.

Offering subterranean clover can reduce methane emissions compared with perennial ryegrass pastures during late spring and summer in sheep

Sheep production systems in south-west Victoria are based predominantly on perennial ryegrass pastures, resulting in highly seasonal growth and declining feed quantity and nutritive value in late spring and summer. These changes result in reduced animal performance and increased CH4 emissions per kg DM intake. A potential alternative to the feedbase used in south-west Victoria that provides high quality and quantity of feed in late spring and early summer are legume-based pastures, such as clovers and lucerne. This experiment examined the impact of legume-based pastures on the growth rates and CH4 emissions of Maternal Composite ewes during late spring and early summer. In 2014, 240 Maternal Composite ewes grazed either perennial ryegrass (Lolium perenne L.), lucerne (Medicago sativa L.), subterranean clover (Trifolium subterraneum L.) or arrowleaf clover (Trifolium vesiculosum Savi.) pastures for 6 weeks during late spring and early summer (November and December). Sheep grazing subterranean clover were heavier at the end of the experiment than sheep grazing perennial ryegrass. Methane measurements using portable accumulation chambers indicated lower daily CH4 emissions (g/day) from sheep grazing subterranean clover (23.5 g/day) than from sheep grazing lucerne (27.3 g/day) and perennial ryegrass (32.3 g/day) pastures. Methane emissions and liveweight changes appeared to be associated with the nutritive characteristics of the forage offered. Legume-based pastures provide sheep producers in south-west Victoria an option to increase growth rates and decrease CH4 emissions during a period when perennial ryegrass pastures are declining in nutritive value.

Sheepmeat flavor and the effect of different feeding systems: a review

Lamb has a unique flavor, distinct from other popular red meats. Although flavor underpins lamb's popularity, it can also be an impediment to consumer acceptance. Lack of familiarity with sheepmeat flavor itself can be a barrier for some consumers, and undesirable feed-induced flavors may also compromise acceptability. Against the backdrop of climate uncertainty and unpredictable rainfall patterns, sheep producers are turning to alternatives to traditional grazing pasture systems. Historically, pasture has been the predominant feed system for lamb production in Australia and around the world. It is for this reason that there has been a focus on "pastoral" flavor in sheep meat. Pasture-associated flavors may be accepted as "normal" by consumers accustomed to meat from pasture-fed sheep; however, these flavors may be unfamiliar to consumers of meat produced from grain-fed and other feed systems. Over the past few decades, studies examining the impacts of different feeds on lamb meat quality have yielded variable consumer responses ranging from "no effect" to "unacceptable", illustrating the diverse and sometimes inconsistent impacts of different forages on sheepmeat flavor. Despite considerable research, there is no consensus on which volatiles are essential for desirable lamb aroma and how they differ compared to other red meats, for example, beef. In contrast, comparatively little work has focused specifically on the nonvolatile taste components of lamb flavor. Diet also affects the amount of intramuscular fat and its fatty acid composition in the meat, which has a direct effect on meat juiciness and texture as well as flavor, and its release during eating. The effect of diet is far from simple and much still needs to be learned. An integrated approach that encompasses all input variables is required to better understand the impact of the feed and related systems on sheepmeat flavor. This review brings together recent research findings and proposes some novel approaches to gain insights into the relationship between animal diet, genetics, and sheepmeat quality.

Lamb growth performance and carcass weight from rotationally grazed perennial pasture systems compared with annual pasture systems with supplements

Annual pastures used to finish lambs can decline in herbage nutritive value (NV) from January to April in the temperate zone. If lambs are to be finished to market specifications for carcass weight during this period, the use of summer-active perennial pastures or supplementation of annual pastures, is required. The present study investigated liveweight (LW) gain and carcass characteristics of lambs finished on perennial pastures compared with annual pastures and supplementation. Fifty-four second-cross lambs were allocated to one of the following four treatments in an asymmetric split-plot design: perennial pasture (PP), annual pasture with hay and grain (AP), AP with flaxseed (AP+FS) and AP with flaxmeal (AP+FM). Lambs were fed for 7 weeks and weighed weekly. Blood glucose and total antioxidant status were determined before, during and at the end of the experiment. Carcass weight and GR fat were measured at 24 h post-slaughter. Lambs grazing PP had significantly higher daily LW gain (P < 0.001), slaughter weight (P < 0.001), carcass weight (P < 0.01) and GR fat (total tissue depth at 12 rib, 110 mm from midline) (P < 0.001) than did lambs grazing AP, AP+FS or AP+FM. Lambs receiving AP+FS and AP+FM grew significantly faster (P < 0.001) than lambs receiving AP. It is likely that lambs grazing the perennial pasture were actively selecting the green portion of lucerne that had higher herbage NV than that indicated by the conventional feed analysis. Results show that lambs grazing a lucerne-dominant perennial pasture performed better than did lambs grazing annual pasture with supplements during the finishing period. Further work is required to determine the efficacy of other perennial species to enable economic finishing of lambs during summer and early autumn.

Bioeconomic modelling to identify the relative importance of a range of critical control points for prime lamb production systems in south-west Victoria

Whole-farm decision making is complex as many factors influence the profitability of pasture-based lamb production systems and other influences such as skills and attitudes also affect the behaviours of individual farmers. In this paper we used bioeconomic modelling to identify the relative importance of manipulating components of lamb production systems in south-west Victoria and quantified their likely impacts on whole-farm profitability. Four lamb production systems that varied in relation to the genotype of the ewes and the time of sale of the lambs were examined in the analysis. Two ‘systems’ were based on first-cross Border Leicester × Merino ewes that were mated to a terminal sire and the lambs were either sold as finished slaughter lambs at 45 kg liveweight or as stores at weaning at 30 kg liveweight. The other two ‘systems’ were based on a self-replacing composite breed (Romney × Coopworth base) and the lambs were sold as finished slaughter lambs or stores. Based on the assumptions used the analysis highlighted that the potential economic gain per unit change was high for several factors examined and the relative importance of these critical control points differed between production systems. Matching lamb turn-off (finished or store) to existing ewe genotype improved profitability by more than $100/ha or 50% and optimising pasture utilisation was also important regardless of production system. A 20% increase in pasture utilisation up to the optimum increased whole-farm profit by more than $100/ha. The impacts of improving pasture growth just after the break of season and through early winter on whole-farm profit were even greater. An extra 20 kg of pasture growth per day at this time of the year is potentially worth about $200/ha due to increases in whole-farm stocking rate. Extra pasture growth in early summer also has significant value for later lambing flocks. When farmers have optimised these factors the second-order control points were cost of replacement ewes for the first-cross system, age at first mating and reproduction efficiency in adult ewes. The management and production factors that will provide the greatest return on effort for individual farmers will depend on the potential economic gain per unit change in the target factor, their current management and production levels and the ease with which the management change or increase in production potential can be achieved in the farming system.