Two experiments were conducted to determine the effects of grazing stockpiled perennial forage in field paddocks relative to feeding similar quality round bale hay in drylot pens on rumen degradation characteristics of forage; beef cow performance, cow reproductive efficiency, estimated dry matter intake and forage utilization, forage yield and quality, soil nutrients and system costs. Winter feeding systems were (i) stockpiled perennial forage (TDN = 58.9%; CP = 8.5%) grazing (SPF) and (ii) drylot feeding (DL) of round bale hay (TDN = 57.9%; CP = 8.4%).
Experiment I was an in situ study, where five Hereford heifers (398 ± 14 kg) fitted with rumen cannulae were fed a grass hay (DM = 93.2%; TDN = 50.8%; CP = 9.8%; NDF = 66.2%) diet. In situ degradability of both stockpiled forage (SPF) and round bale hay (BH) samples collected at start (October) and end (December) of the field study were determined. The soluble fraction (S) of DM was greater (P = 0.01) in SPF October forage compared to SPF December, BH October and BH December forages. The potentially degradable fraction (D) of CP was lowest (P = 0.04) in BH December forage than in SPF October, SPF December and BH October forages suggesting that hay quality declined more rapidly than stockpiled forage and method of preservation may have affected overall hay quality. Furthermore, D fraction of both ADF and NDF was higher in SPF samples suggesting stockpiled forage may be more digestible than hay. However, the D fraction of NDF in both SPF and BH forages declined with later sampling date possibly due to effect of weathering and leaf loss.
In Experiment II, 6, 4-ha paddocks consisting of meadow bromegrass (Bromus riparius
Rehm) and alfalfa (Medicago sativa), were randomly assigned to 1 of 2 replicated (n = 3) winter feeding systems. In this study 58 dry pregnant (120 ± 16 d) Angus cows (675 kg ± 51 kg), stratified by body weight (BW; corrected for conceptus gain), were allocated to either the SPF or DL systems. Cows in winter feeding systems were provided additional energy supplement (rolled barley) (TDN = 86.4%; CP = 12.4%) depending on environmental conditions to maintain body condition, with no weight gain above that of conceptus growth. Dry matter intake (DMI) and forage utilization were estimated using the herbage weight disappearance method. The effects of winter feeding systems on soil nutrients were determined the following spring after winter grazing. Forage yield in DL (4683 ± 495 kg ha-1) and SPF (4032 ± 495 kg ha-1) systems was not different (P = 0.18) between treatments. However, forage utilization was lower (P < 0.01) in SPF (83.5%) than the DL (94.4%) system, signifying lower accessibility to stockpiled forage due to snow depth, lower temperatures, freezing rain and wind. Cows in the SPF system had higher forage DMI (P = 0.04) and supplementation intake (P < 0.01) compared to cows in drylot pens likely a combined effect of effective ambient temperatures below the lower critical temperature (LCT) during the grazing period and the higher potentially digestible fraction of neutral detergent fiber in stockpiled forage than hay. Cow BW change, average daily gain, rib fat change and rump fat change were not different (P > 0.05) between winter feeding systems. Reproductive performance of beef cows was not affected (P > 0.05) by either winter feeding methods as cows in both systems maintained body condition score (BCS) at 2.5 to 3.0 throughout the study. Average total production cost was 19% lower in SPF system compared to DL system. In conclusion, the rumen degradation characteristics of stockpiled perennial forages focused in this study support the utilization these forages in a winter feeding system to meet the nutrient requirements of dry beef cows in early to mid-gestation. It may be cost effective to manage beef cows in field grazing of stockpiled perennial forages in western Canada, without any negative impact on beef cow performance or reproductive efficiency.
| Identifer | oai:union.ndltd.org:USASK/oai:ecommons.usask.ca:10388/ETD-2014-04-1500 |
| Date | 2014 April 1900 |
| Contributors | Lardner, Herbert A. |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text, thesis |
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