Accumulated or stockpiled forage is permitted to grow and develop during the growing season without utilization to provide feed during a subsequent season anticipated to have limited growth; specifically, it refers to late summer growth stockpiled for fall and winter utilization. This process is also referred to in the literature as autumn-saved forage.
The concentration of CP in tall fescue tissue was less than in orchardgrass or Kentucky bluegrass, regardless of sampling time during the winter following an August start of forage accumulation (Item A, Table 11-6). For all the grass species studied, green tissue was greater in CP concentration than brown (dead) tissue. This trend was observed in stockpiled forage in Maryland, Kentucky, Virginia, and North Carolina. Values observed for the green tissue generally would be adequate to support moderate performance of most nonlactating ruminants during the wintering period (National Research Council, 1996).
Increased N application also increased CP concentrations in the forage (Item B, Table 11-6). Delaying N application from June to September increased CP concentrations sampled in December. An early July date to initiate accumulation resulted in rather low CP concentrations (74 g/kg) in December, and N applications of 200 kg/ha increased CP concentrations by only 22 to 96 g/kg. Delaying harvest until February generally reduced CP concentrations, but only slightly.
When tall fescue was clipped instead of stockpiled during late summer, CP concentrations averaged 154 g/kg, compared with lower concentrations when forage was stockpiled from June, July, or September and sampled in August, September, and November, respectively (Item C, Table 11-6). Generally, delaying the time to begin forage accumulation from June to September increased the CP concentration of the subsequent stockpile when sampled in mid-winter (Item C, Table 11-6). A noted exception was reported by Rayburn et al. (1980): CP concentrations changed little when forage was accumulated from June, July, or August and sampled in December (101 to 108 g/kg). A September accumulation sampled in December gave greater CP concentrations 1 yr (132 g/kg), but concentrations were similar to the longer accumulation periods in a second year (106 g/kg). Low CP concentrations from shorter accumulation periods were attributed to weathering associated with early frost damage and higher than normal fall precipitation.
Delaying sampling in the fall, regardless of the time when the stockpile was initiated, also reduced the CP concentrations measured. In North Carolina, the lowest CP concentration generally occurred by mid December to January, with concentrations increasing somewhat by early February and March. This increase was attributed to new growth of tall fescue, which can sometimes occur by February in that region.
|Click Link to Expand|
Delaying the sampling of accumulated tall fescue and orchardgrass from October to December reduced TDD and increased NDF in both species (Item A, Table 11-7). In general, TDD values were slightly greater and NDF slightly less for tall fescue than for orchardgrass.
Examining the green and the brown tissues showed that green tissue had greater TDD than brown tissue regardless of forage species, dates of accumulation, and sampling dates. Second, both tall fescue and orchardgrass changed similarly in DMD and NDF, with the green tissue from tall fescue slightly greater in TDD and with less NDF when forages were accumulated in Maryland. These relationships were less consistent when the two species were stockpiled and compared in Virginia.
The application of 67-84 kg N/ha at time of accumulation generally increased DMD compared with no N fertilizer, but greater rates showed little additional effect in either December or February (Item B, Table 11-7). Applying N, P, and K as a complete fertilizer in August did not alter DMD of the forage in January.
Tall fescue that was clipped during autumn had greater DMD than forage that was accumulated from June or July and sampled in August and September (Item C, Table 11-7). Forage accumulated from September and sampled in November had DMD that was similar to that in the clipped treatment. In general, delaying the date when accumulation was initiated increased DMD and decreased NDF of the forage when sampled in November, December, or January.
Within an accumulation treatment, whether initiated in June, July, August, or September, DMD generally increased from October to November, but showed a large decrease by the December sampling. Both NDF and ADF showed concurrent increases by the December sampling. Increases in DMD and decreases in NDF and ADF can occur in March with the onset of new growth.
Green tissue of tall fescue, orchardgrass, and Kentucky bluegrass had appreciably greater soluble carbohydrate concentrations than dead tissue from the same plants (Item A, Table 11-7). Generally, tall fescue retained its soluble carbohydrate status into the fall and winter better than either orchardgrass or Kentucky bluegrass.
Nitrogen fertilization of tall fescue at modest application rates generally increased soluble carbohydrates in December and January. Stockpiles that began accumulation no earlier than September generally had greater soluble carbohydrate concentrations in the fall and winter than those accumulated over a longer period of time.
|Click Link to Expand|
The proportion of the accumulated stockpile that remains as green tissue during the fall and winter season has an important impact on animal daily response. It is well established that grazing animals select for green leaf tissue and against brown or dead tissue (Hodgson, 1981). As the winter season progresses, stockpiled tall fescue generally declines in the proportion of green tissue and increases in the proportion of brown or dead tissue (Taylor and Templeton, 1976; Archer and Decker, 1977b). Further, the proportion of dead tissue can vary widely from year to year depending on the length of the accumulation period and weather conditions during accumulation. Burns and Chamblee (2000a) showed that when tall fescue was stockpiled monthly in the Piedmont of North Carolina from June to September, the proportion of dead tissue in the November stockpiled forage ranged from 54 to 70% in one year and from 61 to 77% in another year. However, all accumulated forage in December of both years, regardless of accumulation date, had similar proportions of green tissue (26%). This type of variation was reported also by Beaty et al. (1978) in the mountains of Georgia.
Selecting an August closing date and examining the stockpiled herbage revealed that as the fall and winter progressed, the DMD and CP concentrations declined while NDF increased (Burns and Chamblee, 2000b). Associated with these changes was a decline in green tissue and an increase in dead tissue. Upon examination of the stockpiled forage it was noted that the green tissue was greater in DMD (708 g/kg) and lesser in NDF (489 g/kg), whereas the dead tissue had reduced DMD (401 g/kg) and increased NDF (700 g/kg) (Burns and Chamblee, 2002). Further, neither the green nor the dead tissue changed much in composition during the entire fall and winter season. Consequently, the decline in the nutritive value of the stockpile was attributed mainly to the shift in the proportions of green and dead tissues. The relationship between DMD and the proportion of dead tissue showed a decline in DMD ranging from 26 to 55 g/kg, depending on the year, for each increase of 10% units in dead tissue (Burns and Chamblee, 2000b). Moreover, Archer and Decker (1977b) proposed that dead tissue resulting from normal senescence that occurs during accumulation may influence nutritive value differently than dead tissue from cold damage. This was verified by Burns and Chamblee (2000b), who showed tissue that died during accumulation had low DMD in October and changed little during the fall and winter sampling period. They also showed that stockpiled forage that had little dead tissue in October (little senescence) had greater DMD, and, as the dead proportion increased during the winter from cold damage, the DMD remained high. These same trends also were noted for Jesup and MaxQ tall fescues when stockpiling began 15 August and it was sampled from mid November through mid December (Burns et al., 2006b).
The proportion of the tall fescue stockpile that can be retained as green tissue appears to be influenced by the length of the accumulation period and by the severity of the weather during both accumulation and utilization phases. Shorter, late-summer accumulation periods and utilization by mid December improved the nutritive value of stockpiled tall fescue and made the forage a more suitable feed for either growing or producing animals. Longer summer accumulation periods resulted in greater dry matter yields, but the stockpile was least in nutritive value; delaying utilization until December resulted in forage that was suitable only for maintenance. Within a systems context, both management strategies may be appropriate, and the projected feed demand for each animal class can be used to develop a mix of pasture managements appropriate for a particular production system.
|<--Previous||Back to Top||Next-->|