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Biomedical subjects

C W Hunt

Publications and source records attributed to C W Hunt.

28 records · Page 2Linked to original sources
PubMed1995

Effect of barley variety and dietary barley content on digestive function in beef steers fed grass hay-based diets.

Five ruminally and duodenally cannulated steers were used in a 5 x 5 Latin square design with a 2 x 2 + 1 arrangement of treatments to study the effects of barley variety and dietary barley content on digestive function in steers fed grass hay-based diets. Barley varities evaluated were Russell and Steptoe, which had bulk densities of 67.7 and 64.5 kg/hL, respectively. Supplemental treatments were as follows: corn, low Russell (Ru-lo), low Steptoe (St-lo), high Russell (Ru-hi), and high Steptoe (St-hi). Corn, Ru-lo, and St-lo were provided at 30% (DM basis) of grass hay-based diets, whereas Ru-hi and St-hi were provided at 35.5% of diet DM (equal starch content as the corn treatment). No treatment differences (P > .10) were observed for DMI, ruminal particulate passage rate, and NDF total tract digestibility. Ruminal DM and starch digestibility were greater (P < .01) for barley-containing diets than for the corn diet. Similarly, total tract DM (P < .10) and starch (P < .01) digestibility was greater for barley than for corn diets. Microbial protein and non-NH3 N flow to the small intestine were greater (P < .01) for the barley diets than for the corn diet. Starch intake (P < .01) and DM digestibility (P < .10) were greater for high- than for low-barley diets; however, differences due to barley variety were not observed (P > .10). In situ disappearance of grass hay NDF at 8 and 96 h of incubation was greater (P < .05) for barley than for corn diets. Rate of in situ disappearance of grain DM was greater (P < .01) for barley than for corn and for Russell than for Steptoe barley. Responses suggest that ruminal and total tract digestibility and protein flow to the small intestine can be increased with barley compared with corn as an energy supplement to grass hay-based diets.

Animals↗
PubMed1993

Effects of hybrid and ensiling with and without a microbial inoculant on the nutritional characteristics of whole-plant corn.

Two corn hybrids (Pioneer 3377 and 3389) with similar total plant and grain yield characteristics were evaluated to determine potential differences in nutritive value of the whole plant and stover. Hybrids were grown in plots at four different locations in Idaho in 1988 and 1989 for laboratory evaluation. Samples from the plots were stored fresh or ensiled with or without a microbial inoculant for 60 d in laboratory silos. Whole-plant samples of 3377 had a lower (P < .01) percentage of NDF (42.7 vs 48.1), ADF (26.3 vs 30), hemicellulose (16.2 vs 18.2), cellulose (21.4 vs 24), and lignin (3.4 vs 3.8). Similar differences, but of larger magnitude, were observed in stover samples. Ruminal in situ (24 h) and two-stage IVDMD of whole-plant and stover samples were greater (P < .01) for 3377 than for 3389. Lower fiber content and greater degradability for 3377 was not due to greater grain content; 3377 actually had numerically lower grain as a percentage of whole plant than 3389 (41 vs 44). Ensiling reduced (P < .05) NDF, hemicellulose, and cellulose content compared with fresh samples; however, no effect (P > .10) due to inoculant was noted. Hybrid x storage interactions were not observed (P > .10). Inoculation and hybrid did not affect (P > .10) organic acid concentration of the silages. In 1989 silages from 3377 and 3389 were harvested to evaluate diets containing 65% (DM basis) corn silage in steer digestion and growth trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Comparison of corn and barley with and without ruminal buffer in supplements fed in wheat straw-based diets to beef steers.

Ruminal fiber digestion is often decreased by supplementation of readily fermentable carbohydrates. Five ruminally cannulated beef steers were used in a 5 x 5 Latin square design to evaluate the effects of grain type (corn vs barley) and ruminal buffer (Na sesquicarbonate; 0 vs 1.2% of dietary DM) on ruminal digestion and fermentation in wheat straw-based diets. Grain supplements were 30% of the dietary DM. The 2 x 2 + 1 factorial arrangement of treatments included a control supplement that consisted primarily of soybean meal. Diets were fed once daily and were formulated to be 10% CP (DM basis). In situ DM (ISDMD) and NDF (ISNDFD) disappearance of wheat straw was measured at 0, 8, 16, 24, 32, 40, and 96 h incubation. To examine the effects of time after supplementation, 8-h incubations were performed at 0 to 8, 4 to 12, 8 to 16, 12 to 20, and 16 to 24 h after supplementation. Corn diets resulted in lower (P < .05) ISDMD for the 12- to 20- and 16- to 24-h periods than did barley diets. Averaged across 8-h intervals, the control treatment had greater ISDMD (P < .01) and ISNDFD (P < .05) than the grain treatments. Treatment differences were not observed for ISDMD and ISNDFD after 8 h of incubation. Ruminal fluid pH for barley diets was greater at 0, 16, and 20 h and less at 4 h after feeding than for corn diets (treatment x hour; P < .01). Propionate concentration was greater (P < .05) for corn than for barley diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗
PubMed1992

Dose-response effects of recombinant bovine somatotropin implants on feedlot performance in steers.

One hundred twenty crossbred beef steers averaging 377 kg were used in a 2 x 4 factorial experiment to determine the dose-response effects of recombinant bovine somatotropin (rbST) implants on growth performance and carcass characteristics. The implant dosages were 0 (sham), 40, 80, or 160 mg/wk administered s.c. in the tailhead region on a weekly basis throughout the experiment. The steers were fed a high-concentrate diet, which contained either a degradable (DP; soybean meal) or an escape (EP; corn gluten and blood meal) protein source. No dietary protein effect or dietary protein x rbST level interactions were detected. Recombinant bST decreased both DMI (P less than .10) and feed/gain (P less than .05) in a linear dose-dependent manner. Dosage of rbST did not significantly affect (P greater than .10) ADG or final weight of the steers. Recombinant bST decreased backfat depth (P less than .10), marbling score (P less than .05), and quality grade (P less than .10) and increased yield grade (P less than .10) in a linear dose-dependent manner. Soft tissue composition of the 9-10-11th rib section was altered (P less than .01) by rbST administration in a linear dose-dependent manner. The percentage of protein in the rib section was increased by 9.4% and fat was decreased by 11.8% at the 160 mg/wk rbST level compared with the sham-implanted steers. Recombinant bST did not affect (P greater than .10) dressing percentage, hot carcass weight, kidney, pelvic, and heart fat, or longissimus muscle area.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1991

Effects of grass maturity and legume substitution on large particle size reduction and small particle flow from the rumen of cattle.

Five ruminally and abomasally cannulated heifers (average weight 365 kg) were fed 6 kg/d of early (EOG) or late (LOG) maturity orchardgrass (OG) hay with or without replacement of EOG or LOG by 1.5 kg/d red clover hay (RC) in a 5 x 5 Latin square design. A fifth treatment, of LOG supplemented with 100 g/d casein (LOG + C), was used to evaluate the effect of supplemental protein. In situ fiber digestion, in vivo nutrient digestion and rate of passage from the rumen of large (retained on a 1.68-mm screen; labeled with La) and small (passed a 1.68-mm screen; labeled with Sm) EOG and LOG particles were determined in heifers fed these diets. Early maturity OG hay had 20% and 62%, respectively, greater (P less than .05) rates, and 61% and 73%, respectively, greater (P less than .05) extents of in situ NDF and ADF disappearance than LOG. Red clover substitution for OG increased (P less than .05) in situ extent of NDF disappearance by 6%. Early maturity OG large and small particles had 40% and 36%, respectively, greater (P less than .05) rates of passage than LOG. Large and small particle ruminal pool sizes were increased (P less than .05) by 115% and 33%, respectively, with LOG. Red clover substitution for OG increased (P less than .10) large and small particle output (kg/d) from the rumen by 15% and large particle rate of passage by 20%. Grass maturity may be affecting intake through rate of large particle size reduction and passage and small particle passage, although legume supplementation of OG may influence intake by increasing rate of large particle size reduction and passage.

Animal Feed↗
PubMed1990

Effects of rapeseed silage variety and dietary level on digestion and growth performance of beef steers.

A digestion and ruminal fermentation trial involving five ruminally cannulated steers assigned to a 5 x 5 Latin square with a 2 x 2 + 1 arrangement of dietary treatments was conducted to evaluate the effects of variety of rapeseed silage (RS) containing either a high (HG) or a low (LG) glucosinolate concentration when fed at 100 or 50% of diet DM. A bromegrass hay-corn-soybean meal mixture, which was expected to be isocaloric and isonitrogenous with the RS, was used as the control (C) treatment and replaced RS in the 50% diets. In situ disappearance of substrate from both RS varieties was measured in ruminal environments created by each diet. No dietary treatment x RS substrate interactions were observed for any in situ variable. Total tract digestibility and extent of in situ disappearance of both DM and NDF were greater (P less than .01) for HG than for LG. In situ DM and NDF disappearance at 8, 16 and 24 h was greater (P less than .01) for RS than for the C diet. Similarly, total tract DM digestibility was greater (P less than .01) for RS (61.0%) vs C (56.0%) diets. Diets with 50% RS had greater (P less than .01) NDF digestibility (50.4%) than 100% RS (43.6%) diets. Variety of RS had no effect on particulate passage rate. In a 77-d growth trial with 60 beef steers, ADG was greater (P less than .01) for HG vs LG (.46 vs .36 kg), 50 vs 100% (.52 vs .31) and C vs RS (.64 vs .41) diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Effect of dietary level of barley-based supplements and ruminal buffer on digestion and growth by beef cattle.

Six ruminally cannulated beef steers were used in a 6 x 6 Latin square experiment with a 3 x 2 factorial arrangement of treatments to evaluate the effects of barley supplementation (BS; 10, 30 or 50% of diet DM) and ruminal buffer (RB; Na sesquicarbonate at 0 or 4% of BS DM) addition to bromegrass hay-based diets on digestion. When early- (boot) and late- (full maturity) havested bromegrass and wheat straw substrates were incubated in situ, no interactions (P greater than .10) involving substrate with dietary BS or RB were observed, indicating that forages differing in fermentability responded similarly to different ruminal environments. Averaged across substrates, RB had no effect with 10% BS and a positive effect with 30% BS, but a negative effect with 50% BS diets (BS x RB, quadratic; P less than .05) for in situ DM and NDF disappearance for 18 and 24 h of incubation and for rate of disappearance of potentially degraded DM and NDF. Intakes of DM and digested DM were greater (P less than .01) for RB diets; however, RB had no effect (P greater than .10) on total tract DM and NDF digestibility. Intake and digestibility of DM increased linearly (P less than .01), whereas NDF digestibility decreased linearly (P less than .01) as BS percentage was increased in the diet. Sixty beef steers (avg initial wt 302 kg) were fed the same dietary treatments in a growth experiment. A numerical improvement in DM intake (P = .20) and ADG (P = .06) was observed when RB was provided with the 50% BS diet. Results of these experiments indicate that RB may moderate negative effects occurring on ruminal fiber digestion when grains are used to supplement forage-based diets; however, improvements in ruminal digestion were not translated effectively to improved animal productivity.

Ammonia↗
PubMed1989

The delivery of cottonseed meal at three different time intervals to steers fed low-quality grass hay: effects on digestion and performance.

A ruminal fermentation trial and a steer growth trial were conducted to evaluate the effects of time interval of cottonseed meal (CSM) supplementation of predominantly meadow fescue grass hay (GH; CP = 6.6%) on nutrient digestion and growth performance of beef steers. The fermentation trial used four ruminally cannulated steers assigned to a 4 x 4 latin square design with dietary treatments of GH fed alone (C) or GH supplemented with 3 g CP/kg BW.75 daily as supplied by CSM every 12, 24 or 48 h. Nylon bags containing GH were inserted into the rumen on d 1 and 2 of each collection period and incubated for 12, 24, 48 and 96 h to measure NDF and ADF degradation. Subsequently, steers were fed Yb-labeled GH and fecal samples were collected to determine particulate passage rate (PR). Dry matter and NDF intake, mean NDF and ADF in situ disappearance and ruminal VFA concentrations were greater (P less than .05) when CSM was fed; however, the delivery of CSM at various times did not affect (P greater than .10) these variables. Supplemented diets tended (P = .08) to have faster PR compared with the C diet. In the growth trial, CSM supplemented steers consumed more digestible DM (P less than .05) and had greater (P less than .05) daily gain compared with C steers. Effects due to time of CSM supplementation were not observed for the variables measured in the present study.

Animal Feed↗
PubMed1989

Migrant labor and sexually transmitted disease: AIDS in Africa.

Acquired immune deficiency syndrome (AIDS) is worldwide, but the clinical and epidemiological pattern of the disease in Africa is different from that in developed areas. "Type 1 AIDS" occurs in industrialized North America and Europe; it has a distinctive sex ratio (16:1) and risk pattern of IV drug use and sexual practices. "Type 2 AIDS" occurs in Third World countries, particularly in eastern, southern, and central Africa. It is characterized by an entirely different sex ratio (1:1) and by distinctively different risk patterns. Both epidemics are caused by the HIV-1 virus. The key concept for understanding the origins of the differences between Type 1 and Type 2 AIDS is the migratory labor system in eastern, central, and southern Africa. This system causes long absences, increased family breakdown, and increased numbers of sexual partners. Historically the organization of this labor market has created a population which suffers from epidemics of sexually transmitted diseases. These historical patterns are presented as evidence for the contemporary transmission of AIDS. When contemporary AIDS and HIV-1 seropositivity prevalence data are examined, a systematic temporal and geographic pattern emerges for the AIDS epidemic in Africa. Despite a paucity of good data, the prevalence data from eastern, central, and southern Africa support the thesis of migrant labor's role in the transmission of AIDS.

Acquired Immunodeficiency Syndrome↗