A comparison of annual forages and stockpiled pasture on the growth and health parameters of grazing fall-born lambs

Abstract

The objective of this experiment was to investigate the effect of annual forages on the growth and parasite resilience of growing, fall-born lambs. We hypothesized that lambs grazing annual forages would increase their body weight (BW) at a greater rate and be more resilient to parasitic infection when compared with lambs grazing on stockpiled pasture. A total of 54, 60-day-old Dorset and Suffolk × Dorset crossbred lambs (24 ± 4.9 kg) were stratified by sex, weight, and randomly assigned to one of three grazing treatments with all lambs weaned at an average of 60 days of age and placed on either: 1.) Avena sativa (oat), 2.) Brassica rapa subsp. Rapa (turnip), or 3.) Schedonorus arundinaceus (Schreb.) (permanent tall fescue-based) pastures. In terms of lamb growth, lambs grazing turnips demonstrated greater BW on days 42 and 56 when compared with lambs grazing oat and stockpiled pastures. In addition, lambs grazing turnips had a greater average daily gain (ADG) on days 28 and 42 when compared with lambs grazing oat and stockpiled pastures. Furthermore, on day 42, lambs grazing stockpiled pastures had a greater ADG when compared with lambs grazing oat pastures. For indices of parasitism, there were no differences shown between treatments for lamb FAMACHA© eye score, packed cell volume, and total plasma protein concentration. However, lambs grazing oat pastures had less eggs per gram of feces on days 28, 42, and 56 when compared with lambs grazing turnips and stockpiled pastures. Annual forages can play a critical role in the growth and resilience to parasitic infection of grazing lambs, as lambs grazing on turnips demonstrated the greatest BW and ADG whereas lambs grazing on oat pastures shed fewer fecal eggs per gram of feces.