96 Cover Crop Grazing and Backgrounding on Carcass Quality

Abstract Integration of sheep into cropping systems via cover crop grazing leases has potential to benefit sheep producers with a source of inexpensive, high quality forage. We examined this potential by comparing lamb growth and carcass traits of four rearing systems: grain-finished control (GR), cover crop brassica-finished (CCB), cover crop mixture-finished (CCM), and background on brassica and finished on grain (BK-GR). Dorset x Polypay lambs (n = 60; 3 pens or pastures, 5 lambs each) were blocked by body weight and randomly assigned to treatment. All diets were provided to maximize voluntary dry matter intake. Lambs were harvested after 6 wks of feeding for GR and 8 wks for CCB, CCM and BK-GR (BK-GR = 4 wks brassica then 4 wks grain). Grain-fed lambs (GR and BK-GR, 442 g/d) grew faster than pasture-fed lambs (CCB and CCM, 152 g/d) prior to harvest (Table 1, P < 0.01) and attained greater body mass (HCW), muscling (LEA, EMD), fatness (BF, BWF) and yield grade (all P < 0.05). Growth of pasture-fed lambs declined 38% over time (247 wk 1–4 vs. 152 g/d wk5-8; P < 0.05). Pasture-fed lambs were leaner than grain-fed lambs (BF, yield grade; P < 0.01), yet attained a yield grade 2 average. Background lambs (BK-GR) exhibited a 107% increase in growth when fed grain (232 g/d pasture vs. 481 g/d grain, P < 0.01) and were fatter (BF, P < 0.05) yet had reduced eye muscle depth (P < 0.01) at harvest than GR lambs. Lambs did not differ in growth or any carcass measurement according to pasture type (CCB vs. CCM). We conclude that 8 wks of cover crop finishing produced acceptable carcass weight and finish. Backgrounding on cover crops followed by 4 wks of grain finishing results in marked compensatory gain with lambs achieving the same carcass size and similar qualities to lambs fed only grain.