Forage Production and Quality in 2003: Impacts on Livestock Performance

Kevin Sedivec, Extension Rangeland Specialist, Animal and Range Sciences Department, North Dakota State University

Introduction

Forage Quality in 2003

Summary

Introduction

Herbage production, and subsequent forage production, is directly correlated to growing season precipitation. In North Dakota cool-season grasses such as western wheatgrass, green needlegrass, smooth bromegrass and Kentucky bluegrass (Junegrass) produce 80 to 85 percent of their total growth from May through mid-July (Figure 1). The remaining 15% to 20% of the total biomass growth occurs from early September through early October in the form of regrowth, depending on temperature and moisture. If precipitation is at or above normal in May and June, cool-season grass growth will be at or above normal during the first growth cycle. If precipitation is below normal in August and September, cool-season grass regrowth potential will be limited.

Warm-season grasses such as blue grama, little bluestem and prairie sandreed produce most of their growth in June, July and August (Figure 2). If precipitation is at or above normal in June and July, warm-season grasses will achieve at or above normal production. However, if precipitation is low, especially in June and July, overall herbage production and subsequent forage production will be reduced.

Precipitation at the Central Grasslands Research Extension Center near Streeter, North Dakota, was above normal in May and June, 2003, however, well below normal in July, August and September (Table 1). Based on plant growth physiology and 2003 precipitation patterns, primary growth of cool-season grasses was probably at or above normal in 2003, however, regrowth was very limited. Warm-season grass growth started out very well in May and June but was stressed in July and August, resulting in less overall growth than normal years.

Overall, forage production should be average or slightly below average on much of North Dakota’s and northern South Dakota’s rangelands in 2003. Although cool-season grass production was abundant during its primary growth period there was little fall regrowth and warm-season grass production was reduced. Many ranchers in the Dakotas experienced excellent grass growth in much of 2003.

However, these same ranchers quickly discovered a shortage of grass in September and October due to below normal warm-season growth and a lack of cool-season regrowth. Bob Patton (personal communication) reported an average peak total above ground production of 2,786 lb/ac on the grazing intensity trial in 2003 (when assuming 86% silty, 14% overflow)(Table 2). The 2003 peak production was similar to the current 5-year average (2,635 lb/ac), indicating the abundant cool-season growth in May through July compensated for the loss of cool-season regrowth and warm-season grass production.

Forage Quality in 2003

North Dakota’s range and pasture lands provide high quality feed in May through July, however, they can become deficient in nutrients by August depending on moisture conditions (Figure 3). Meeting the nutritional needs of a lactating cow during the second half of the grazing season is highly dependent on late summer cool-season grass regrowth. This regrowth is extremely important in years that receive excellent May and June moisture and subsequently achieve a fully-matured grass stand in July and August, as seen in 2003.

Grasses contain the lowest quantity of nutrients (crude protein, phosphorus, energy) when allowed to mature and set seed (Figure 3). When grasses are allowed to reach this physiological stage, nutritional quality will not meet the needs of a lactating cow and high quality regrowth (Figure 3) is essential in sustaining livestock performance throughout the grazing season. In 2003, most cool-season grasses reached full maturation with limited regrowth, creating a worst case scenario of low quality feed in August, September and October.

Figure 3. Crude protein content of primary growth and regrowth of selected cool-season grasses at the Central Grasslands Research Extension Center near Streeter, ND.

Livestock nutritional management was critical in 2003 in maintaining high calf gains and cow condition. Creep feeding would have been an option in August through October to maintain calf performance on poor quality feed. The cow would have still lost condition, however, good calf performance would be maintained. A second and probably better option would have been to wean calves earlier than normal. Early weaning would have allowed individual calf feeding to maximize performance while reducing the nutritional demands and quantity of forage needed for the grazing cow.

Summary

The grazing season of 2003 was an odd year for North Dakota livestock producers. The growing season provided the best and worst of moisture regimes. Abundant moisture early in the growing season provided excellent forage production, however, the very dry mid and late summer created diminished growth and an extremely low quality feed during the second half of the grazing season. If you experience years like 2003 in the future, prepare for an abundant mature stand of forage that is low in crude protein, phosphorus, and possible energy. Plan for an aggressive creep feeding program or early weaning strategy that minimizes the loss in cow condition and calf performance. Remember, we are always blessed to receive good spring and summer moisture. Adequate spring and early summer moisture guarantees abundant forage, but you may need to plan for low quality conditions.