Influence of advancing season on dietary composition, intake, site of digestion, and microbial efficiency in beef steers grazing a native range in western North Dakota1

Abstract

Four ruminally and duodenally cannulated beef steers (388 +/- 12 kg) were used to evaluate effects of advancing season on forage quality, intake, site of digestion, and microbial efficiency while grazing mixed-grass prairie in western North Dakota. Five 11-d sample collections were conducted from late June to mid-November. Chromic oxide (8 g) was dosed twice daily at 0700 and 1900 h via gelatin capsule from d 2 to 11 of each collection period, and duodenal and fecal collections were performed on d 7 to 11. Masticate samples were collected for each sampling period. Dietary N declined linearly (P = 0.01), from 1.95% in June to 1.15% in November, whereas NDF increased linearly (P = 0.01), 72.4% in June to 85.1% in November. Total OM intake (g/kg of BW) decreased linearly (P <or= 0.01) from June to November, from 26.2 to 11.4 +/- 2.7 g/kg of BW, respectively, and ruminal fill increased linearly (P <or= 0.01) from June to November, from 45.4 to 65.9 +/- 3.3 kg, respectively. True ruminal OM and N digestion declined linearly (P <or= 0.01) with advancing season. Total tract OM, N, and NDF digestion declined linearly (P <or= 0.01). Microbial efficiency (g of microbial N/kg of OM truly fermented) increased linearly (P = 0.02) from late June to late November. Undegradable intake protein (UIP) intake (g/d) declined (P <or= 0.06) linearly and cubically from 374.4 in June to 215.9 g in November. Degradable intake protein (DIP) intake was 735.5 g/d in June and declined linearly (P <or= 0.01) to 99.5 g/d with advancing season. Likewise, microbial CP supply at the duodenum (g/d) declined linearly (P <or= 0.01) as season advanced. As expected, DIP (% of CP) decreased (P <or= 0.01; 66.1 to 31.9 +/- 5.8% for June to November, respectively), whereas percentage of UIP increased (P <or= 0.01; 33.9 to 68.1 +/- 5.8% for June to November, respectively) with advancing season. The portions of DIP and UIP (% of CP) were not different in late August and mid-September. These data imply that mixed-grass range forage consumed by cattle after late September is deficient in N, particularly DIP, and that forage intake may decrease and may be too low to support adequate cow performance. Supplementation could be implemented to overcome these deficiencies; however, additional research is needed to determine supplemental type and frequency needed to optimize nutritional and economic efficiency.

Chemical Composition, In vitro Gas Production, Ruminal Fermentation and Degradation Patterns of Diets by Grazing Steers in Native Range of North Mexico

“…The NDF content was 8% higher in 2005 than in 2004, while CP content was 20% higher in 2004. These differences in chemical composition of diets may be induced by registered rainfall in the two years of study (Cline et al, 2009). The CP, IVDMD and ME values were greater in summer and fall as compared to winter and spring (p<0.01); while NDF content was higher in spring and winter as compared to summer and fall (p<0.01).…”

Influence of advancing season on dietary composition, intake, site of digestion, and microbial efficiency in beef steers grazing season-long or twice-over rotation native range pastures in western North Dakota1

“…Research was conducted approximately 35 km north and 5 km west of Dickinson, ND (N latitude 47°11′43′′, W longitude 102°50′22′′; Cline et al, 2009). This area is characterized by a continental climate with warm summers and cold winters.…”

“…As forage matures, digestibility and N content decrease, whereas fiber and lignin content increase (Savage and Heller, 1947;Cook, 1972;Johnson et al, 1998). Nitrogen, especially degradable intake protein (DIP), can be deficient in native range forages consumed by cattle later in the grazing season (Cline et al, 2009). Supplementation is often practiced to optimize livestock performance and offset forage quality and quantity deficiencies.…”

Chemical composition, intake, ruminal fermentation, plasma metabolites and hormones in range steers

“…However, would not be satisfied. These differences between years and seasons may be the result of registered rainfall during the collection periods (Cline et al 2009). Cha´vez and Gonza´lez (2009) mention that nutritive quality of the diet of grazing cattle in northern Mexico is higher in summer and fall versus winter and spring and attribute these differences to the phenology of rangelands.…”