EFFECTS OF UTILIZING CROP RESIDUES IN WINTER FEEDING SYSTEMS ON BEEF COW PERFORMANCE, REPRODUCTIVE EFFICIENCY AND ECONOMICS
Over 2 years (Year 1, 2009-2010; Year 2, 2010-2011), two separate experiments were conducted to evaluate the effects of winter feeding system (n=3) on beef cow performance, reproductive performance, economics and forage degradability. The three systems (treatments) were grazing pea crop residue (PEA) cv. ‘Performance 40-10’ (Year 1, TDN = 50.2%, CP = 7.3%; Year 2, TDN = 56.9%, CP = 8.9%) in field paddocks, grazing oat crop residue (OAT) cv. ‘Baler’ (Year 1, TDN = 59.1%, CP = 2.9%; Year 2, TDN = 66.9%, CP = 5.3%) in field paddocks, and feeding mixed grass-legume hay in drylot pens (DL) (Year 1, TDN = 61.4%; CP = 8.8%; Year 2, TDN = 52.3%, CP = 12.3%). In the first experiment, 90 dry, pregnant Black Angus cows (Year 1, 629 kg ± 74 kg; Year 2, 665 ± 69 kg) stratified by body weight (BW) and days pregnant were randomly allocated to 1 of the 3 systems. Cows were allocated feed in the field or pen on a 3 d basis and supplemented oat grain daily at 0.4-0.6% BW depending on environmental conditions. Dry matter intake (DMI) was estimated for each system using the herbage weight disappearance method. Cow BW, body condition score (BCS), and rib and rump fat were measured at start and end of trial and cow BW was corrected for conceptus gain based on calving data. When data from the first 20 d were pooled over 2 years, initial cow BW was greater (P < 0.01) for the DL and OAT cows compared to the PEA cows and final cow BW was different (P < 0.01) between all 3 winter feeding systems. The change in BW was also greater (P < 0.01) for DL cows compared to cows on the OAT and PEA treatments. Analysis of the first 20 d of Year 1 study period and the total Year 2 study period, showed a significant (P < 0.01) year by treatment interaction for final BW and BW change. The differences (P < 0.01) in initial BW, final BW and BW change between the first 20 d of Year 1 study period and the total Year 2 study period (20 d) suggest feed quality, animal preference and weather conditions may cause difficulties when grazing residues in winter grazing systems. Analysis of the entire trial period in Year 1 (62 d) indicates differences (P < 0.01) for final BW and BW change between cows on all three systems. The change in rib and rump fat was also different (P < 0.01) between cows in all 3 systems. In Year 2 (20 d), initial BW, final BW and BW change were different (P < 0.01) between DL and PEA cows, and between (P < 0.01) OAT and PEA cows. No difference (P > 0.05) was found for cow rib and rump fat in Year 2 and no difference (P > 0.05) was found for BCS in either Year 1 or Year 2 for cows managed in all 3 systems. Differences (P < 0.05) were observed for calving rate and calf birth weight between the DL and OAT system cows, but not between (P > 0.05) cows managed in the DL and PEA or OAT and PEA systems. Costs per cow per day were $1.22, $1.01 and $2.77 for PEA, OAT and DL systems in Year 1, respectively. In Year 2, cow costs per day were $1.59, $1.44 and $1.84 for PEA, OAT and DL systems, respectively. In experiment 2, three ruminally cannulated, dry Holstein cows were fed a silage based total mixed ration (TMR) of 22 kg barley silage, 7 kg chopped alfalfa hay and 1 kg energy supplement (DAC-485). In-situ degradability was studied to determine the extent of degradation of pea, oat and grass-legume hay collected at start (SOT) and end of test (EOT) in experiment one. Rate of degradation (Kd) of DM was greater (P < 0.01) for PEA EOT compared to HAY, OAT SOT and OAT EOT. Dry matter rate of degradation for PEA SOT was greater (P < 0.05) compared to OAT SOT and OAT EOT. The effectively degradable fraction of CP was greater (P = 0.03) for HAY compared to PEA EOT. The ruminally undegradable fraction of CP was greater (P = 0.03) for PEA EOT compared to HAY. Acid detergent fiber rate of degradation (Kd) was greater (P = 0.01) for PEA EOT compared to HAY, OAT SOT and OAT EOT. Acid detergent fiber rate of degradation for PEA SOT was greater (P < 0.05) compared to OAT SOT and OAT EOT. No differences (P > 0.05) were observed between either OAT SOT and OAT EOT or PEA SOT and PEA EOT for S, D, U, ED or RU suggesting that weathering did not have an effect on the degradability of the forages. The results of these experiments show that it is possible to maintain cow BW through the winter months in Western Canada by grazing oat crop residues, which have the potential to reduce winter feeding costs.
DegreeMaster of Science (M.Sc.)
DepartmentAnimal and Poultry Science
SupervisorLardner, H. A.
CommitteeMcKinnon, John J.; Hendrick, Steve
Copyright DateJune 2013