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PubMed1997

Effects of dietary forage source and amount of forage addition on intake, milk yield, and digestion for lactating dairy cows.

Lactating cows were used to determine the effects of increasing forage content from alfalfa (Medicago sativa L.) hay or Tifton 85 bermudagrass (Cynodon sp.) hay or Tifton 85 bermudagrass (Cynodon sp.) hay on dry matter intake (DMI), milk yield, and nutrient digestion. Forage proportions and neutral detergent fiber (NDF) content of diets were (dry basis) 1) 45% corn (Zea mays L.) silage (control), 33.5% NDF; 2) 15% bermudagrass hay and 30% corn silage, 39.5% NDF; 3) 30% bermudagrass hay and 15% corn silage, 46.6% NDF; 4) 15% alfalfa hay and 30% corn silage, 35.5% NDF; or 5) 30% alfalfa hay and 15% corn silage, 33.5% NDF. The DMI was greater with alfalfa diets than with bermudagrass diets, with low hay diets than with high hay diets, and with the control diet than with the hay diets. Digestibility of NDF in bermudagrass diets was greater than that in alfalfa diets, in high hay diets than in low hay diets, and in hay diets than in the control diet. In vitro NDF digestion was most rapid for bermudagrass hay, intermediate for corn silage, and slowest for alfalfa hay. Results suggest that NDF from bermudagrass was digested more completely and rapidly than was NDF from corn silage or alfalfa, which improved the rate of passage despite the high NDF content of diets containing bermudagrass. Milk yield followed trends for DMI. The control diet and diets containing alfalfa elicited the greatest DMI and milk yield, but DMI per 100 kg of body weight for Holsteins was equal for diets containing either bermudagrass or alfalfa. High quality bermudagrass can be used in rations for lactating dairy cows.

Animal Feed↗
PubMed1989

Comparison of two methods for enumeration of anaerobe numbers on forages and evaluation of ethylene oxide treatment for forage sterilization.

Experiments were conducted to (i) compare most-probable-number (MPN) procedures with roll tube procedures for enumeration of forage anaerobic bacteria and (ii) evaluate the efficacy of using ethylene oxide to sterilize wet herbage. Alfalfa, corn, and alfalfa-orchardgrass silages and alfalfa and orchardgrass herbages were analyzed for total anaerobic bacteria (medium pH, 6.8) and acid-tolerant anaerobic bacteria (medium pH, 4.5) by both roll tube and MPN procedures. No difference was found between the roll tube and MPN procedures for total bacteria; however, higher counts were obtained for acid-tolerant bacteria when the MPN procedure was used. Although MPN procedures require less time to obtain an estimate of bacterial numbers, isolation and identification of the microbial population is not possible. Alfalfa herbage was treated with ethylene oxide for 12, 24, or 36 h, incubated for 7 days at 37 degrees C with or without addition of a bacterial inoculant, and analyzed for total bacteria by MPN procedures. Microbial growth after inoculation of ethylene oxide-treated herbage indicated that there was insufficient residual ethylene oxide to inhibit subsequent microbial growth. The results also indicated that 24 h was required to adequately sterilize fresh herbage. Thus, ethylene oxide can be used to sterilize wet herbage for use as a substrate for pure cultures of silage bacteria.

Journal Article↗
PubMed1994

Performance and forage utilization by beef cattle receiving increasing amounts of alfalfa hay as a supplement to low-quality, tallgrass-prairie forage.

Two experiments evaluated effects of amount of supplemental alfalfa hay on intake and utilization of dormant, tallgrass-prairie forage by beef steers and on performance of cows grazing tallgrass prairie during winter. In Exp. 1, four supplemental alfalfa levels (.23, .47, .70, and .94% BW.steer-1.d-1) were evaluated in a 34-d, randomized complete block design experiment using 16 steers (291 kg). Voluntary tallgrass-prairie hay intake decreased linearly (P = .02), whereas total DMI increased linearly (P < .01) with increased alfalfa. Dry matter digestibility was unaffected (P > .10) by treatment, although NDF digestibility decreased (linear, P = .03) and passage rates of indigestible ADF and Cr EDTA increased (linear, P = .02) with increased alfalfa. In Exp. 2, supplemental alfalfa (.48, .72, or .96% BW.cow-1.d-1) was fed to 113 pregnant Hereford x Angus cows (502 kg) from November 27 until calving (average calving date = March 7). Cumulative weight loss from the beginning of the experiment until just after calving was lowest with .96% BW alfalfa (quadratic, P = .09), and cumulative condition loss was decreased linearly (P = .02) with increased alfalfa. Although treatment did not alter (P > .10) pregnancy rates, increasing the amount of alfalfa supported shorter intervals to conception (P = .03). Cows fed .96% BW alfalfa weaned heavier calves (quadratic, P = .04) than other groups. Results indicate that improvements in performance of beef cows in moderate body condition were greater when the amount of supplemental alfalfa was increased from .48 to .72% BW than when it was increased from .72 to .96% BW.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗
PubMed1991

Microscopic investigation of changes in histology and digestibility in the rumen of a forage grass and a forage legume during the first growth stage.

An Italian "Dalita" ryegrass (Lolium italicum) and a European lucerne (Medicago sativa) were harvested at 5 different growth stages to determine the anatomical factors limiting their digestibility and in particular the effects of lignification of the tissues. In vitro digestibility, cell wall contents of the whole plant and stem of lucerne and of the whole plant, stem and leaf blade of ryegrass were determined. The rate and the extent of degradation in the rumen of the different tissues were observed by scanning electron microscopy. This degradation occurred very rapidly with the lucerne stems; the xylem of lucerne was the only undegradable tissue whatever the stage. The collenchyma was degraded in the rumen although with acid phloroglucinol it stained positive for the presence of phenolic compounds. Ryegrass stems were digested more slowly than lucerne stems, and the sclerenchyma and xylem of ryegrass were indigestible whatever the stage. The parenchyma located close to the sclerenchyma became indigestible as the cell walls lignified progressively from the third stage. These results contribute to the understanding of the decrease in digestibility over the first growth stage and the variation in rate of digestion of lucerne and ryegrass in the rumen.

Animal Feed↗
PubMed1996

The fate of absorbed and exogenous ammonia as influenced by forage or forage-concentrate diets in growing sheep.

Changes in splanchnic energy and N metabolism were studied in sheep, prepared with vascular catheters across the portal-drained viscera (PDV) and the liver, and maintained on supramaintenance intakes of either gross or grass + barley pellets. The animals were challenged, on both diets, with 4 d intramesenteric vein infusions of NH4Cl (25 mumol/min) plus NH4HCO3 (at either 0 or 125 mumol/min). On the final day of each treatment the natural abundance NH4Cl was replaced with 15NH4Cl over a 10 h infusion while over the same period [1-13C]leucine was infused via a jugular vein. Measurements were made of blood flow plus mass transfers of NH3, urea, free amino acids and O2 across the PDV and liver. Enrichments of [14N15N]urea and [15N15N]urea plus [15N]glutamine, aspartate and glutamate were also monitored. Whole-body urea flux was determined by infusion of [14C]urea. At the end of the study the animals were infused for 3 h with 15nH4Cl, killed and liver samples assayed for intracellular free amino acid enrichments and concentrations. Blood flows across the splanchnic region were unaffected by either diet or level of ammonium salt infusion. At the lower ammonium salt infusion there was a trend for greater absorption of NH3 across the PDV (P < 0.10) with grass + barley than with the grass diet, while removal of urea was unaltered. At the higher ammonium salt infusions there was a significantly greater appearance of NH3 across the PDV and this exceeded the extra infused. Urea-N removal, however, was also elevated and by more than that required to account for the additional NH3. The PDV contributed 19-28% to whole-body O2 consumption and the liver 23-32%. Hepatic extraction of absorbed NH3 was complete on all treatments and systemic pH remained constant. The fractions of urea-N apparently derived from NH3 were similar on the grass (0.50-0.64) and grass + barley (0.64-0.67) diets. Hepatic production of urea agreed well with urea flux measurements. Between the two levels of ammonium salt infusion and within diets the additional NH3 removed across the PDV was accounted for by the increased urea-N production. The [14N15N]:[15N15N] ratio of the urea produced was 97:3, while the enrichment of hepatic intracellular free aspartate was lower than that of [14N15N]urea. Glutamine enrichments were 0.23-0.37 those of [14N15N]urea, indicating a minor role for those hepatocytes (probably perivenous) which contain glutamine synthetase (EC 6.3.1.2). Leucine kinetics, either for the whole body or splanchnic tissues, were not different between diets or level of ammonium salt infusion, except for oxidation which was less on the grass + barley ration. Amino acid concentrations were lower on the grass + barley diet but net PDV absorptions were similar. The pattern of essential amino acids absorbed into the PDV showed good agreement with the published composition of mixed rumen microbial protein. Fractional disappearances of absorbed free essential amino acids across the liver varied from 0.4 (branched chains) to near unity (histidine, phenylalanine).

Amino Acids↗
PubMed1989

Nutrient digestion in the large intestine as influenced by forage to concentrate ratio and forage physical form.

Digestion in the large intestine was investigated in four growing steers fitted with duodenal and ileal cannulas. Diets assigned within a 4 x 4 Latin square were: 20% long alfalfa hay and 80% grain; 15% pelleted alfalfa, 5% hay, and 80% grain; 80% hay and 20% grain; and 60% pellets, 20% hay, and 20% grain. Intake of DM was not affected by diet. Organic matter digestion in the large intestine averaged 9, 3, 1, and -4% of total tract digestion for the 20% hay, 20% pellet, 80% hay, and 80% pellet diets, respectively, with significant increases due to high grain diets and long hay. Digestion of CP in the large intestine as a percentage of total tract digestion was unaffected by diet but averaged 3, -1, .3, and -6% for the respective diets. Percentage of total tract starch digestion occurring in the large intestine increased with grain feeding and averaged 6, 3, 1, and 1%, respectively. Digestion of ADF and NDF in the large intestine as a percentage of total tract was unaffected by diet; however, the respective means were 16 and 15, 7 and 7, 5 and 15, and 1 and 1%. In a second trail the same animals were fed a more typical dairy cow diet consisting of 50% grain, 25% corn silage, and 25% long alfalfa hay for a single 18-d period. Digestion in the large intestine accounted for 2.1, .2, 3.6, and 6.4% of total tract digestion of organic matter, starch, ADF, and NDF, respectively; however, feed intake was not as great as in the first trail. Although conditions of these studies differed from those commonly experienced by lactating cows, the underlying principals should apply. The large intestine would be expected to make an even greater contribution to total tract digestion in lactating cows consuming proportionally more DM.

Animal Feed↗
PubMed1989

Production of volatile fatty acids in the rumen and cecum-colon of steers as affected by forage:concentrate and forage physical form.

Contribution of cecal and ruminal VFA to metabolizable energy was investigated in steers with cannulas in both the rumen and cecum. Animals were fed ad libitum so that data would be applicable to the lactating dairy cow. Diets assigned within a 4 x 4 Latin square were: 20% long alfalfa hay and 80% concentrate; 15% pelleted alfalfa, 5% hay and 80% concentrate; 80% hay and 20% concentrate; 60% pellets, 20% hay and 20% concentrate. Intake of DM was unaffected by diet. Cecal fluid pH, osmolality, and concentrations of valerate and isovalerate were unaffected by diet. Concentrations of total VFA, acetate, propionate, butyrate, and lactate in the cecum increased with proportion of grain in the diet. The high grain diets depressed cecal ammonia concentration and acetate to propionate ratio. Acetate production in the cecum was higher with the high grain diets whereas that in the rumen was lower. Production of propionate and butyrate in both the cecum and rumen was unaffected by diet. Cecal VFA provided 8.6% of metabolizable energy intake, on average. Contribution of ruminal VFA to total metabolizable energy was affected by diet, accounting for 72, 51, 74, and 52% of metabolizable energy from the 20% hay, 20% pelleted alfalfa, 80% hay, and 80% pelleted alfalfa, respectively. Cecal VFA were an important source of energy for ad libitum-fed steers; this contribution would undoubtedly increase with increasing feed intake.

Animal Feed↗
PubMed2005

Effect of cattle age, forage level, and corn processing on diet digestibility and feedlot performance.

Three experiments were conducted to determine the effects of cattle age and dietary forage level on the utilization of corn fed whole or ground to feedlot cattle. In Exp. 1, 16 steers were used to investigate the effects of cattle age and corn processing on diet digestibility. Two cattle age categories were evaluated (weanling [254 +/- 20 kg BW] and yearling [477 +/- 29 kg BW]; eight steers per group), and corn was fed either ground or whole to each cattle age category. Cattle age and corn processing did not affect (P > 0.10) diet digestibility of DM, OM, starch, CP, NDF or ADF, and no interactions (P > 0.10) between these two factors were detected. In Exp. 2, the effects of forage level and corn processing on feedlot performance and carcass characteristics were evaluated. One hundred eighty steers (310 +/- 40 kg BW) were allotted to 24 pens, and were fed one of the following diets: high-forage (18.2% corn silage) cracked corn (HFCC); high-forage shifting corn (whole corn for the first half of the trial, then cracked corn until harvest; HFSC); high-forage whole corn (HFWC); low-forage (5.2% corn silage) cracked corn (LFCC); low-forage shifting corn (LFSC); and low-forage whole corn (LFWC). For the high-forage diets, steers fed cracked corn had 7% greater DMI than those fed whole corn, whereas for the low-forage diets, grain processing did not affect DMI (interaction; P = 0.02). No interactions (P > 0.10) between forage level and corn processing were found for ADG and G:F. Total trial ADG and G:F, and percentage of carcasses grading USDA Choice, and carcass yield grade were not affected (P > 0.10) by corn processing. Cattle with fewer days on feed grew faster and more efficiently when cracked corn was fed, whereas cattle with longer days on feed had greater ADG and G:F when corn was fed whole (interaction; P < 0.10). In Exp. 3, the effects of forage level and corn processing on diet digestibility were evaluated. The high-forage cracked corn, high-forage whole corn, low-forage cracked corn, and low-forage whole corn diets used in Exp. 2 were fed to 16 steers (350 +/- 27 kg BW) in a digestion trial. No interactions (P > 0.10) between forage level and corn processing were detected for starch digestibility. Forage level and corn processing (grinding) did not affect (P > 0.10) diet DM, OM, starch, CP, and NDF digestibility. Processing corn did not provide additional benefits to feedlot cattle performance under these experimental conditions.

Age Factors↗
PubMed2003

Effects of forage and sunflower oil levels on ruminal biohydrogenation of fatty acids and conjugated linoleic acid formation in beef steers fed finishing diets.

Six Hereford steers (295 kg) cannulated in the proximal duodenum were used to evaluate the effects of forage and sunflower oil level on ruminal biohydrogenation (BH) and conjugated linoleic acid (CLA) outflow. Steers were fed one of six treatment diets in a 3 x 2 factorial arrangement of treatments (grass hay level: 12, 24, or 36% of DM; and sunflower oil level: 2 or 4% of DM) in a 6 x 6 Latin square design. The remainder of the diet was made up of steam rolled corn and protein/mineral supplement. Duodenal samples were collected for 4 d following 10-d diet adaptation periods. Data were analyzed with animal, period, forage level, sunflower oil level, and two-way interaction between forage and sunflower oil level in the model. Dry matter intake showed a quadratic response (P < 0.04), with an increase in DMI as forage level increased from 12 to 24% followed by a decrease in DMI when 36% forage was fed. Flow of fatty acids at the duodenum was higher (P < 0.03) for 4 vs. 2% sunflower oil diets, and similar among forage levels. Apparent ruminal digestibility of NDF increased in a linear manner (P < 0.04) as dietary forage level increased. Ruminal BH of dietary unsaturated 18-C fatty acids, oleic acid, and linoleic acid increased linearly (P < 0.05) as dietary forage level increased. Linoleic acid BH tended (P < 0.07) to be greater for 4 than 2% sunflower oil level. Duodenal flow of pentadecyclic, stearic, linolenic, and arachidic acids increased linearly (P < 0.05) as dietary forage level increased from 12 to 36%. Duodenal flow of linoleic acid decreased in a linear manner (P < 0.03) with increasing dietary forage level. Flow of trans-10 octadecenoate decreased linearly (P < 0.03) as dietary forage level increased, whereas trans-11 vaccenic acid flow to the duodenum increased (P < 0.01) linearly with increased dietary forage. Dietary forage or sunflower oil levels did not alter the outflow of cis-9, trans-11 CLA. Flows of cis-11, trans-13, and cis-9, cis-11 CLA increased linearly (P < 0.05) with increased dietary forage. Flows of cis-11, cis-13, and trans-11, trans-13 CLA decreased linearly (P < 0.05) with increased dietary forage. Increasing dietary forage levels from 12 to 36% in beef cattle finishing diets increased BH of unsaturated 18-C fatty acid and outflow of trans-11 vaccenic acid to duodenum without altering cis-9, trans-11 CLA outflow.

Animal Feed↗
PubMed2000

Effects of starch source and level of forage neutral detergent fiber on performance by dairy cows.

The effectiveness of neutral detergent fiber (NDF) from soyhulls and whole cottonseed for replacing NDF from forage was evaluated in a lactation trial during wk 10 to 25 of lactation. Forty-eight cows were blocked and randomly assigned within a block to one of four diets: 1) 21% forage NDF with corn 2) 16% forage NDF with corn, 3) 16% forage NDF with corn and wheat (1:1) and, 4) 11% forage NDF with cottonseed and corn. Soybean hulls were added at approximately 23.0% of dry matter (DM) for the 16 and 11% forage NDF diets to replace forage and formulate diets with 35% nonfiber carbohydrates. Actual forage NDF concentration were 17.8, 14.0, 13.9, and 9.4%, respectively. Dry matter intake and milk yield were highest for cows fed 11% forage NDF with cottonseed. Milk fat percentage was higher for cows consuming 21% forage NDF and 16% forage NDF with corn than for cows fed the two other diets. Cows fed 16% forage NDF with corn and wheat experienced milk fat-protein inversion, but ruminal acetate:propionate was lower for cows fed 11% forage NDF than cows fed 16% forage NDF. Body weight (BW) and BW change were not different among treatments. Time spent chewing was similar among all diets. For cows in midlactation, forage NDF may be reduced to 9 to 11% when cottonseed is at 11% of DM and dietary nonstructural carbohydrates are at 30% of DM. Forage NDF may be reduced to 14 to 16% without cottonseed when nonstructural carbohydrates are at 30% of DM.

Animal Feed↗
PubMed2005

Sex-specific foraging behaviour in a seabird with reversed sexual dimorphism: the red-footed booby.

Most hypotheses attempting to explain the evolution of reversed sexual dimorphism (RSD) assume that size-related differences in foraging ability are of prime importance, but the studies on sex-specific differences in foraging behaviour remain scarce. We compare the foraging behaviour of males and females in a seabird species with a RSD by using several miniaturised activity and telemetry loggers. In red-footed boobies males are 5% smaller and 15% lighter than females, but have a longer tail than females. Both sexes spend similar time on the nest while incubating or brooding. When foraging at sea, males and females spend similar time foraging in oceanic waters, forage in similar areas, spend similar proportion of their foraging trip in flight, and feed on similar prey-flying fishes and flying squids-of similar size. However, compared to males, females range farther during incubation (85 km vs. 50 km), and furthermore feed mostly at the extremity of their foraging trip, whereas males actively forage throughout the trip. Males are much more active than females, landing and diving more often. During the study period, males lost mass, whereas females showed no significant changes. These results indicate that males and females of the red-footed boobies differ in several aspects in their foraging behaviour. Although some differences found in the study may be the direct result of the larger size of females, that is, the slightly higher speeds and deeper depths attained by females, others indicate clearly different foraging strategies between the sexes. The smaller size and longer tail of males confer them a higher agility, and could allow them to occupy a foraging niche different from that of females. The higher foraging effort of males related to its different foraging strategy is probably at the origin of the rapid mass loss of males during the breeding period. These results suggest that foraging differences are probably the reason for the differential breeding investment observed in boobies, and are likely to be involved in the evolution and maintenance of RSD.

Animals↗
PubMed1995

Is there an endogenous tidal foraging rhythm in marine iguanas?

As strictly herbivorous reptiles, Galápagos marine iguanas graze on algae in the intertidal areas during low tide. Daily foraging rhythms were observed on two islands during 3 years to determine the proximate factors underlying behavioral synchrony with the tides. Marine iguanas walked to their intertidal foraging grounds from far-off resting areas in anticipation of the time of low tide. Foraging activity was restricted to daytime, resulting in a complex bitidal rhythm including conspicuous switches from afternoon foraging to foraging during the subsequent morning when low tide occurred after dusk. The animals anticipated the daily low tide by a maximum of 4 h. The degree of anticipation depended on environmental parameters such as wave action and food supply. "Early foragers" survived in greater numbers than did animals arriving later at foraging sites, a result indicating selection pressure on the timing of anticipation. The timing of foraging trips was better predicted by the daily changes in tabulated low tide than it was by the daily changes in actual exposure of the intertidal foraging flats, suggesting an endogenous nature of the foraging rhythms. Endogenous rhythmicity would also explain why iguanas that had spontaneously fasted for several days nevertheless went foraging at the "right" time of day. A potential lunar component of the foraging rhythmicity of marine iguanas showed up in their assemblage on intertidal rocks during neap tide nights. This may indicate that iguanas possessed information on the semi-monthly rhythms in tide heights. Enclosure experiments showed that bitidal foraging rhythms of iguanas may free run in the absence of direct cues from the intertidal areas and operate independent of the light:dark cycle and social stimuli. Therefore, the existence of a circatidal oscillator in marine iguanas is proposed. The bitidal foraging pattern may result from an interaction of a circadian system with a circatidal system. Food intake or related stimuli may be used as tidal zeitgebers in synchronizing the foraging rhythms of these reptiles under natural conditions.

Animals↗
PubMed1996

Effects of forage level on the comparative feeding value of supplemental fat in growing-finishing diets for feedlot cattle.

Ninety-six crossbred steers (316 kg) were used in a 135-d growth-performance trial to evaluate the comparative feeding value of yellow rease (0 vs 6%) in 10% forage vs 30% forage rowing-finishing diets. There were interactions between forage level and supplemental fat on ADG (P < 10), DM conversion (P < .05), diet NE (P < .10), longissimus muscle area (P < .01), fat thickness (P < 10), and percentage of retail yield (P < .01). Supplemental fat increased (8.5%; P < .10) marbling score, sufficient to move the average carcass grade from high Select to low Choice. With the low-forage diet supplemental fat did not affect (P > .10) ADG, but decreased (P < .01) retail yield (2.3%) and longissimus muscle area (5.6%). With the high-forage diet supplemental fat increased ADG (13.3%; P < .05) and longissimus muscle area (7.1%; P < .01) but did not affect (P > .10) retail yield. Differences in carcass fat were small and not affected by treatment (P > .10). The NEm and NEg values of yellow grease were 3.55 and 2.65 Mcal/kg, respectively, for the low-forage diet and 5.71 and 4.65 Mcal/kg, respectively, for the high-forage diet. Treatment effects on characteristics of ruminal and total tract digestion were evaluated using four Holstein steers (233 kg) with cannulas in the rumen and proximal duodenum. There were no interactions (P > .10) between forage level and supplemental fat on ruminal and total tract digestibility of OM, ADF, starch, lipid, and gross energy. Postruminal lipid digestibility averaged 65.5% and was not affected (P > .10) by forage level. The ME value of yellow grease was the same (6.94 Mcal/kg) for both the low- and high-forage diets. There was an interaction between supplemental fat and forage level on nonammonia N flow to the small intestine (P < .10), percentage of ruminal escape feed N (P < .05), postruminal N digestion (P < .05), and methane production (P < .10). With the low-forage diet, fat supplementation did not affect (P > .10) ruminal degradation for feed N and methane production. With the high-forage diet fat supplementation decreased ruminal degradation of feed N (19.0%; P < .05) and methane production (14.8%; P < .05). We concluded that supplementation of a 30% forage (alfalfa hay) finishing diet with 6% yellow grease will permit growth-performance similar to that of steers fed a 10% forage diet without supplemental fat. The improved performance may be attributed to increased diet energy density and positive associative effects on protein flow to the small intestine and decreased ruminal methane production.

Animal Feed↗