Effects of wet corn gluten feed on ruminal pH and productivity of lactating dairy cattle fed diets with sufficient physically effective fiber.

Wet corn gluten feed (WCGF), a byproduct of the wet-milling industry, is commonly substituted in lactating dairy rations for both forages and concentrates. Previous research has shown that increasing WCGF in the diet decreased ruminal pH, likely due in part to decreasing particle size as forage inclusion rate decreased. The objective of this study was to maintain at least 10% of ration particles >19 mm in length across diets while increasing WCGF inclusion in the diet. We hypothesized that as WCGF increased in this scenario, dry matter intake (DMI) and milk yield would increase and ruminal pH would be maintained. Seven ruminally cannulated, lactating Holstein cows (4 multiparous and 3 primiparous) were used in an incomplete 4×4 Latin square design. Treatments included 0, 12.4, 24.5, or 35.1% WCGF and used alfalfa hay to maintain particle size. Across treatments, crude protein and neutral detergent fiber concentrations were held relatively constant. Four 21-d periods were used with 17d of adaptation and 4d of sample collection. Indwelling ruminal pH probes were used during sampling periods and recorded pH every 5 min. Particle size of total mixed rations and orts were analyzed using a Penn State Particle Separator (The Pennsylvania State University, University Park). Results were analyzed with mixed models to test the fixed effect of treatment. All diets contained ≥10% of particles >19 mm; however, as WCGF increased, the proportion of particles >19 mm decreased. Interestingly, with increasing WCGF, cows sorted for the particles >19 mm but against particles on the bottom screen and pan. With increasing WCGF, ruminal pH was not affected, but DMI and milk yield increased in a quadratic fashion, with the peak responses for the 24.5% WCGF diet. Milk protein, lactose, and fat concentrations were not affected by treatment; however, milk protein and lactose yields increased with the inclusion of WCGF because of the increased milk yield. Production efficiency was not affected by treatments. Thus, if adequate particle size is maintained when WCGF increases in the diet, DMI and milk yield increase while maintaining production efficiency and ruminal pH.

Effects of varying rates of tallgrass prairie hay and wet corn gluten feed on productivity of lactating dairy cows.

Productivity of lactating dairy cows fed diets with wet corn gluten feed (WCGF, Sweet Bran, Cargill Inc., Blair, NE) as the primary energy substrate and prairie hay as the primary source of physically effective neutral detergent fiber (peNDF) was assessed relative to a control diet. Forty-eight Holstein cows, 100 to 250 d in milk, were randomly assigned to 1 of 6 pens and pens were randomly assigned to treatment sequence in a replicated 3×3 Latin square. Treatments were a control diet with 18% alfalfa, 18% corn silage, 33% WCGF, and 15% forage NDF (CON); a diet with 20% tallgrass prairie hay, 46% WCGF, and 13% forage NDF (TPH20); and a diet with 14% tallgrass prairie hay, 56% WCGF, and 9% forage NDF (TPH14). Midway through period 2, TPH14 was discontinued due to the high prevalence of diarrhea among cows on that treatment. Data from period 2 for TPH14 pens were discarded, and the pens that had been assigned to TPH14 for period 3 were randomly assigned to the other 2 treatments. Pen-level data were analyzed using linear mixed models, including the random effects of period and pen and the fixed effect of treatment. For animal-level data, additional random effects were introduced to account for subsampling. No evidence for treatment effects was apparent on dry matter intake. Least squares mean milk yields were 36.2, 34.6, and 35.2 kg/d for CON, TPH20, and TPH14, respectively, and were not significantly different. Milk fat concentration was higher for CON and TPH20 than for TPH14, with means of 3.48, 3.41, and 2.82%, respectively. Fat yield was significantly greater for CON compared with TPH20 and TPH14. Milk urea nitrogen was greatest for TPH20 and TPH14 and least for CON, consistent with differences in dietary protein content. Efficiencies, expressed as energy-corrected milk divided by dry matter intake, were 1.47, 1.42, and 1.24 for CON, TPH20, and TPH14, respectively, and were not significantly different. These data indicate that TPH14 did not provide adequate peNDF to support normal rumen function in mid lactation dairy cows; instead, TPH20 may be a feasible diet for use on dairies where high-NDF grass hay and WCGF are available.

Effects of feeding increasing levels of wet corn gluten feed on production and ruminal fermentation in lactating dairy cows.

An experiment was conducted to evaluate the effects of increasing dietary inclusion rates of wet corn gluten feed (WCGF; Sweet Bran; Cargill Inc., Blair, NE) on milk production and rumen parameters. Four primiparous and 4 multiparous ruminally cannulated Holstein cows averaging 90±13 d in milk (mean ± SD) were randomly assigned to 1 of 4 sequences in a replicated 4 × 4 Latin square experiment with 28-d periods. Treatments were diets containing 0, 11, 23, and 34% WCGF on a dry matter basis; alfalfa hay, corn silage, corn grain, soybean meal, expeller soybean meal, and mineral supplements were varied to maintain similar nutrient concentrations across diets. Performance and measures of ruminal fermentation were monitored. Linear and quadratic effects of increasing WCGF inclusion rate were assessed using mixed-model analysis. Increasing dietary WCGF linearly increased dry matter intake (26.7, 25.9, 29.3, and 29.7 kg/d for 0, 11, 23, and 34% WCGF, respectively) and milk production (36.8, 37.0, 40.1, and 38.9 kg/d). Concentrations of milk components did not differ among treatments; however, protein and lactose yields increased linearly and fat yield tended to increase linearly when more WCGF was fed. This led to greater production of energy-corrected milk (38.2, 38.8, 41.7, and 40.4 kg/d) and solids-corrected milk (35.2, 35.7, 38.5, and 37.2 kg/d), but efficiency of production linearly decreased. Increased WCGF in the diet tended to linearly decrease ruminal pH (6.18, 6.12, 6.14, and 5.91), possibly because mean particle size was below typical recommendations for all diets, and diets with greater proportions of WCGF had a smaller mean particle size. Ruminal acetate concentration decreased linearly and propionate increased linearly as WCGF inclusion rate increased. Treatments had a quadratic effect on ammonia concentration, with greater concentrations for the 0 and 34% WCGF diets. In situ digestibility of soybean hulls showed a significant diet-by-time interaction, and increasing dietary levels of WCGF linearly decreased in situ neutral detergent fiber disappearance at 24h. Change in body condition score increased linearly with increasing WCGF inclusion rate. Results indicate that adding WCGF to dairy rations can increase energy-corrected milk yield, and this increase appears to be driven, at least in part, by an increase in dry matter intake.

Effects of alfalfa hay inclusion rate on productivity of lactating dairy cattle fed wet corn gluten feed-based diets.

An experiment was conducted to evaluate the effects of varying the alfalfa inclusion rate in diets containing 31% (dry matter basis) wet corn gluten feed (Sweet Bran, Cargill Inc.). Eighty primiparous and multiparous Holstein cows averaging 178 +/- 90 d in milk (mean +/- SD) were randomly assigned to 1 of 4 sequences in a 4 x 4 Latin square design with 28-d periods. Treatments were diets containing 0, 7, 14, or 21% alfalfa on a dry matter basis, with corn silage, corn grain, soybean meal, expeller soybean meal, and mineral supplements varying across diets to maintain uniform nutrient densities. Diets were formulated for similar crude protein, neutral detergent fiber, and nonfiber carbohydrate concentrations. Feed intake, milk production, body weight, and body condition score were monitored, and linear and quadratic effects of increasing the alfalfa inclusion rate were assessed using mixed model analysis. As the alfalfa inclusion rate increased, dry matter intake tended to increase linearly (26.7, 27.3, 27.4, and 27.5 kg/d for 0, 7, 14, and 21% alfalfa, respectively), and solids-corrected milk (29.9, 30.2, 30.8, and 30.5 kg/d) and energy-corrected milk production (32.9, 33.3, 33.8, and 33.6 kg/d) tended to increase linearly. Body weight gain decreased linearly (22.9, 18.0, 11.2, and 9.5 kg/28 d) with increasing alfalfa inclusion rate. Although increasing the inclusion rate of alfalfa increased the proportion of large particles in the diets, treatments had no effect on milk fat yield or concentration. Feeding more alfalfa (up to 21% of dry matter) tended to increase milk yield while decreasing body weight gain, suggesting that metabolizable energy utilization shifted from body weight gain to milk production in these treatments. However, adding alfalfa to the diet had only minor effects on productivity.

Combinations of starch and digestible fiber in supplements for steers consuming a low-quality bromegrass hay diet.

Five steers (690 kg) with ruminal and duodenal cannulas were fed 100% bromegrass hay or 60% bromegrass hay:40% concentrate at 90% of their ad libitum DMI. The concentrate consisted of ground corn (GC) and(or) soybean hulls (SBH): 1) 100% SBH; 2) 66% SBH/33% GC; 3) 33% SBH/66% GC; or 4) 100% GC. Increasing level of corn inclusion decreased (linear, P < .01) DM and OM digestion (corrected for microbial DM and OM flow) in the rumen. Neutral detergent fiber digestion decreased in the rumen (quadratic, P = .05) and total tract (linear, P = .06) with increasing level of corn. Ruminal NDF digestion (quadratic, P = .05) and duodenal microbial N flow (quadratic, P < .01) were greatest for 66% SBH/33% GC, whereas total N flow to the duodenum was similar (P > .10) among treatments. Microbial efficiency increased (quadratic, P = .10) as the level of corn inclusion increased. Molar percentage of ruminal acetate decreased (linear, P < .01) with increasing level of corn, whereas molar percentage of butyrate increased (linear, P < .10). Carboxymethylcellulase activity was greatest (quadratic, P = .08) for 66% SBH/33% GC and paralleled NDF digestion in the rumen. Increasing level of corn decreased (linear, P < .07) in situ DM digestibility of SBH after 4, 8, and 12 h of incubation.

Site and extent of nutrient digestion by steers fed a low-quality bromegrass hay diet with incremental levels of soybean hull substitution.

Five ruminally and duodenally cannulated steers were fed bromegrass hay (H; 5.6% CP; 70.9% cell wall) substituted with 0, 15, 30, 45, or 60% soybean hulls (SH; 10.5% CP; 87.9% cell wall) at 90% of ad libitum DMI. Diets were made isonitrogenous (11% CP) by addition of isolated soybean protein (91.5% CP). Total ruminal VFA concentration, molar proportion of acetate, and molar acetate:propionate ratio increased (linear; P less than .02) with increasing level of SH substitution, but propionate (mol/100 mol) and ruminal fluid passage rate decreased (linear; P less than .01). Ruminal pH and ammonia concentration decreased more rapidly, and to a greater extent and duration, as level of SH increased; neither was decreased to levels considered detrimental to fiber digestion. Ruminal and total tract DM, OM, and cell wall digestibilities increased (linear; P less than .01), whereas total tract N digestibility decreased (linear; P = .03), as level of SH increased Total N flow to the duodenum increased (linear, P = .03) with increasing level of SH, and microbial N flow tended (cubic, P = .09) to increase. Microbial efficiencies were unchanged (P = .10) with SH level. True ruminal digestibilities of N did not differ (P greater than .10) among diets. Rate of in situ DM disappearance of H and SH was not influenced (P greater than .10) by SH substitution, although rate tended to be fastest with 30 and 45% SH (quadratic, P = .14). We infer from these data that SH can replace 60% of the DMI of a low-quality forage diet without decreasing OM or cell wall digestion.

Performance, forage utilization, and ergovaline consumption by beef cows grazing endophyte fungus-infected tall fescue, endophyte fungus-free tall fescue, or orchardgrass pastures.

Two 120-d trials (May to September, 1988 and 1989) determined the effects of grazing tall fescue (two varieties) or orchardgrass on forage intake and performance by beef cows. Each summer, 48 cow-calf pairs grazed endophyte-infected Kentucky-31 tall fescue (KY-31), endophyte-free Mozark tall fescue (MOZARK), or Hallmark orchardgrass (OG) pastures (16 pairs/treatment). Forage OM intakes and digestibilities were determined during June and August each year. Cow and calf BW and milk production were determined every 28 d. During June of both years, OM intakes did not differ (P greater than .10) among treatments. During August of 1988, intakes were 18% lower (P less than .05) by KY-31 cows (1.6% of BW) than by MOZARK or OG cows (average 1.95% of BW); however, no differences (P greater than .10) were measured in August of 1989. Estimates of ergovaline consumption during June from KY-31 were between 4.2 (1988) and 6.0 mg/d (1989), whereas August estimates were between 1.1 (1988) and 2.8 mg/d (1989). Ergovaline in MOZARK estrusa was below detection limits, except in August of 1989. Cows that grazed KY-31 lost three times (P less than .01) more BW than cows that grazed MOZARK or OG (42 vs 9 and 13 kg, respectively). Milk production by KY-31 cows was 25% lower (P less than .01) than that by cows that grazed MOZARK or OG (6.0 vs average of 8.0 kg/d). Similarly, slower (P less than .01) calf gains were noted for KY-31 than for MOZARK or OG (.72 vs .89 and .88 kg/d, respectively). Cows grazing KY-31 experienced accelerated BW loss and reduced milk production and weaned lighter calves than did cows grazing MOZARK or OG. Decreased performance was not explained by consistently reduced forage intakes; hence, altered nutrient utilization was suspected.

Use of DNA probes to monitor nutritional effects on ruminal prokaryotes and Fibrobacter succinogenes S85.

We used DNA probes to study dietary effects on the prokaryotic population in the rumen. Procedures used to isolate and quantify prokaryotic 16S ribosomal RNA (rRNA) from the rumen using universal and species-specific DNA probes were evaluated. In this experiment, three ruminally fistulated steers were fed orchard-grass hay, and ruminal digesta were collected at 0, 3, and 9 h after offering hay (0800). Samples of ruminal digesta were taken from the interior portion of the digesta mat and from the fluid below the mat in the dorsal rumen. Freezing (-65 degrees C) and blending samples both increased (P less than .07) the yield of 16S rRNA from ruminal digesta. Extraction of prokaryotic rRNA was greater (P less than .04) when phenol buffered with sodium acetate was used than when it was buffered with hydroxymethyl-amino-methane. Prokaryotic 16S rRNA concentration of the fluid phase was similar (P greater than .10) at 0, 3, and 9 h after offering hay. Prokaryotic 16S rRNA concentration of the mat phase increased up to the 9 h after feeding. The proportion of Fibrobacter succinogenes remained constant in both digesta phases at all times measured. From these data we concluded that DNA probes can be used to monitor bacterial population shifts in the rumen.

Digestibility of vegetative and mature tall fescue greenchop with or without alfalfa greenchop substitution.

Nine ruminally and duodenally cannulated steers (average BW 355 kg) were used to evaluate effects of prebloom alfalfa greenchop substitution at 20% of DMI on utilization of late-May (high quality; HQ; Period 1) and mid-August (low quality; LQ; Period 2) tall fescue greenchop. Alfalfa inclusion did not influence (P greater than .10) diet ad libitum DMI during Period 1 but it decreased (P less than .10) DMI during Period 2. Ruminal and total tract DM, cell wall, and GE digestibility of HQ were unaffected (P greater than .10) by alfalfa inclusion; however, digestibility of these constituents in LQ was increased (P less than .03) by alfalfa substitution. Alfalfa substitution did not influence (P greater than .10) dietary cell wall monosaccharide disappearance. Ruminal CP digestibility was greater (P less than .10) when steers received alfalfa, but microbial efficiency (grams of bacterial N/kilogram of OM truly digested in the rumen) was not enhanced (P greater than .10) by alfalfa inclusion in either HQ or LQ diets. There was a trend (P = .15) for greater microbial efficiency with alfalfa substitution to LQ. Ruminal particulate passage rate did not differ (P greater than .10) between treatments for either stage of maturity. Fluid passage rate was faster (P less than .10) in steers that received only LQ (7.1%/h) than in those fed LQ substituted with 20% alfalfa (5.0 %/h). Our data suggest that alfalfa inclusion in a low-quality fescue diet enhanced cell wall and GE digestibility.