Forage crops offer low-cost and efficient lamb finishing
Take Home Message: Grazing brassicas reduces feeding costs and improves carcass weight whilst the use of chicory/plantain/clover mixes can reduce the need for worming.
Grazing forage crops can add value and weight to lambs at low cost and improve efficiency of production by releasing grazing for ewes when lambs are marketed earlier. These were the findings of UK trials with chicory/plantain mixes, the results of which were presented to delegates at this year’s British Society of Animal Science’s annual conference, by SAC’s John Vipond.
“The second trial year was wet, so the results failed to show the exceptional gains typical of New Zealand trials, but the forage crops do show promise as bio-active mixtures that reduce the need for worming and also improve trace element/mineral status of lambs,” he explained, adding that further evaluation was justifiable.
Traditionally UK lamb finishers have used forage brassicas to extend the season of supply of lamb beyond the grazing season. Retailers, however, can now import low-cost chilled lamb from New Zealand from December to June so UK supply extension is financially now more risky.
So two trials were carried out to evaluate the ability of currently used forage brassicas to finish lambs in November and December (2007) and to compare the most promising ones with mixtures containing chicory, plantain and clover (CP) for finishing lambs in August and September (2008). The latter mixture has shown to be bio-active with anthelmintic effects.
Five 0.33ha plots of different forage brassicas – kale, rape, stubble turnips, hybrid kale/rape (HB) and a rape/turnip mixture – were established on an upland old grassland site in Peebleshire. Lamb performance was evaluated from early November to mid December 2007 using 75 store lambs, weighing between 32kg and 36kg. Lambs were weighed empty on arrival, given an anthelmintic, allocated to the plots balanced for initial live weight and breed, weighed again after 30 days and slaughtered on day 39.
The abattoir recorded carcass weight, fatness and conformation, which were used with body weight data and an estimated carcass weight at the start of the trail to estimate daily bodyweight gain, killing out percentage and carcass gain.
In the 2008 trial, a hybrid kale/rape crop and mixtures containing chicory, plantain and clover were grazed by parasitised lambs from mid August to mid September with. Lamb liveweight gain was recorded for all lambs and faecal egg count (FEC) was recorded for three lambs per plot.
“And despite there being significant differences in daily gain on the crop in the 2007 trial, estimates of daily carcass gain were not significantly different between treatments as there were differences in killing out percentage,” said Dr Vipond. “All crops grew well and the stubble turnips, being sown earlier than normal, had exceptional yields but lambs had difficulty utilising the crop when roots broke free of soil.
The hybrid kale/rape crop was chosen to compare with chicory/plantain mixes in the 2008 trial. The two plots containing the hybrid crop out yielded the three chicory/plantain mixes and they showed significantly higher lamb liveweight gain. And observations were that lambs preferred to eat the hybrid kale/rape crop, rather than the chicory/plantain mix.”
After 44 days on the crop, 90 % of HB and HB/CP lambs were in finished condition versus only 80% of the lambs on the other chicory/plantain mixes. Lamb daily gains on chicory/plantain mixes were lower than expected from previous work where gains of more than 250g/day were achieved.
“The summer of 2008 was wet and estimates of dry matter content of the brassicas was 87g/kg compared to 67g/kg for chicory/plantain mix suggesting water content of the forages may have constrained intake and performance,” added Dr Vipond.
“And while the overall effect of forage approached statistical significance, lambs on the chicory/plantain mixes showed reduced faecal egg count (FEC) compared to lambs on brassicas and the mineral content of the forages was around twice as high.”
Presented to the British Society of Animal Science Annual Meeting, March 30 to April 1, 2009, Southport, UK.
Full details: Vipond J, Matheson S, Veldhuis A, Houdijk JGM: “Use of forage brassicas and bio-active chicory/plantain/clover mixtures for lamb finishing.”
Summary (pdf) Presentation_045vipond (pdf)
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