Effect of grazing different forage systems prior to and during mating on the liveweight, condition score, conception and reproductive rate of maternal-composite ewe lambs

Abstract

Context Economic modelling identified that mating of ewe lambs for lambing at 1 year of age has the potential to increase the profitability of sheep-production systems in south-western Victoria. In order to optimise reproductive rates, ewe lambs should weigh at least 35–40 kg, have a condition score (CS) of 3.0 at mating, and be gaining weight (100–150 g/day) during mating. However, typical perennial ryegrass (Lolium perenne L.) pastures in south-west Victoria do not support the attainment of these targets without additional supplementation. Aim Our research aimed to determine how grazing summer-active pastures or brassica (Brassica napus L.) forages affects the liveweight, CS, conception and reproductive rate of ewe lambs when offered before and during mating compared with a system using perennial ryegrass plus supplement. Methods A field experiment was conducted at Hamilton, Victoria, Australia, in 2014 and 2016 testing seven forage treatments replicated four times in a complete block design. The treatments were: canola (B. napus, two treatments of different cultivars), forage brassica, lucerne (Medicago sativa L.), chicory (Cichorium intybus L.), plantain (Plantago lanceolata L.) and perennial ryegrass. Key results Ewe lambs grazing canola or forage brassica had higher (P < 0.05) liveweight gains during the pre-mating and mating periods than those grazing the perennial ryegrass treatment (148 vs 75 g/day in 2014, s.e.m. 17; 139 vs 54 g/day in 2016, s.e.m. 17). In 2014, spring-sown dual-purpose canola, lucerne and chicory resulted in higher (P < 0.05) reproductive rates (144–151%) than the perennial ryegrass treatment (103%); forage brassica and plantain gave intermediate results (128% and 129%). Conclusion Brassica forages (including spring-sown canola), lucerne and chicory can support the attainment of key liveweight and CS targets for successful mating of ewe lambs in autumn. Implications Spring-sown canola is therefore a viable alternative forage for use by livestock producers in southern Australia and presents an opportunity to incorporate an alternative income stream in mixed-farming systems.

Dual-purpose cropping: the opportunity for a step change in production in the temperate region of Australia

“…A more recent application of dual-purpose crops is for spring sowing of crops for grazing in late summer/autumn and harvesting in late spring/early summer in the year after sowing, which has been demonstrated to provide valuable out-ofseason grazing without impacting yield (Paridaen and Kirkegaard 2015). Research in south-west Victoria reported in this special issue (Raeside et al 2021a(Raeside et al , 2021c demonstrates that in environments where it is suitable, for example milder summer temperatures and more consistent summer rainfall, spring sowing of canola can improve diet quality in late summer/autumn, and reduce supplementary feeding costs.…”

“…Canola was a common dualpurpose crop used across sites. Research at Hamilton demonstrated that reproductive rates of ewe lambs that grazed canola were equivalent to or better than other feed options provided (Raeside et al 2021c). At Canberra and Wagga Wagga, ewes grazed canola during late-pregnancy and lambing.…”