Biomedical subjects

G W Horn

Publications and source records attributed to G W Horn.

At least 19 recordsLinked to original sources

PubMed2005

Incidence of puberty in beef heifers fed high- or low-starch diets for different periods before breeding.

Spring-born Hereford x Angus heifers (n = 206) were used to determine effects of energy supplementation programs and amount of starch in the diet on incidence of puberty. In Exp. 1, heifers (205 +/- 5 kg; n = 68) grazing dormant native pasture were fed 0.9 kg/d (as-fed basis) of a 42% CP supplement from November until February 14. Heifers were stratified by weaning weight and allotted randomly to treatment before breeding (May to July). Treatments were 1) 0.9 kg (as-fed basis) of a 42% CP supplement/d and pasture (control); 2) a high-starch (HS) diet (73% corn; 53% starch) fed in a drylot for 60 d (HS-60); 3) a HS diet fed in drylot for 30 d (HS-30); or 4) a low-starch (LS) diet (49% corn; 37% starch) self-fed on pasture for 30 d (LS-30). The HS-60 and HS-30 heifers were limited-fed to gain 0.9 kg/d, and the LS-30 heifers had ad libitum access to the diet. High-starch-60 and LS-30 heifers were heavier (P < 0.05) than control and HS-30 heifers at the beginning of the breeding season. Thirty-one, 25, and 26% more HS-60 heifers were pubertal (P < 0.05) on May 1 compared with LS-30, HS-30, and control heifers, respectively. At puberty, HS-60 heifers were 24 and 22 d younger (P < 0.05) than LS-30 and control heifers, and 31 kg lighter (P < 0.01) than LS-30 heifers. In Exp. 2, heifers grazed dormant pasture and were fed 0.9 kg (as-fed basis) of a 42% CP supplement/d from weaning in October to late February; then heifers were assigned randomly to treatments for 60 d before the breeding season. In two years, control heifers (n = 46) grazed pasture and received 0.9 kg of SBM supplement/d; LS (n = 46) heifers were self-fed a distiller's grain and soybean hull-based diet in drylot; and HS heifers (n = 46) were limited-fed a corn-based diet in drylot. During treatment, HS and LS heifers had greater weight gains than control heifers. Pubertal BW (313 +/- 6 kg) was not influenced by treatment, but HS and LS heifers were younger (P < 0.03) than control heifers at puberty. During a 60-d breeding period, the incidence of puberty was greater (P < 0.05) for HS and LS heifers than for control heifers and was greater (P < 0.05) in HS than in LS heifers in Year 1. Feeding a LS or a HS diet for 30 d before breeding may be inadequate to stimulate puberty in beef heifers, but feeding a diet with a greater amount of starch for 60 d before breeding may increase the incidence of puberty during breeding of heifers that have inadequate yearling weight.

Animal Feed↗

PubMed2005

Effects of grazing program and subsequent finishing on gene expression in different adipose tissue depots in beef steers.

This experiment was conducted to examine the effects of grazing program and subsequent finishing on gene expression in adipose tissue from steers. Twenty Angus x Angus-Hereford steer calves (initial BW = 231 +/- 25 kg) were allotted randomly to one of two winter grazing treatments: 1) grazing winter wheat pasture to achieve a high rate of BW gain (HGW); or 2) grazing dormant tallgrass native range (NR). Steers in the NR treatment were provided 0.91 kg.steer(-1).d(-1) of a 41% CP (as-fed basis) cottonseed meal supplement. Following the grazing period, steers were assigned randomly to feedlot pens. Steers were fed to a common endpoint of 1.27 cm of backfat between the 12th and 13th rib. Four steers from each treatment were slaughtered at the end of the grazing period, and the remaining steers from each treatment (n = 6) were slaughtered at the predetermined compositional endpoint. Intramuscular and s.c. fat samples were collected from LM sections of each steer at the 12th-/13th-rib interface on the left side. Pools of RNA were prepared for HGW and NR s.c. adipose tissue from steers slaughtered immediately after grazing. Suppression subtractive hybridization was performed followed by dot-blot hybridization screening to confirm differential expression of subtracted transcripts. Transcripts confirmed to be differentially expressed were subjected to dideoxy chain-termination sequencing. Quantitative reverse transcription PCR was performed on three differentially expressed clones: osteonectin, ferritin heavy chain, and decorin. Osteonectin, ferritin heavy chain, and decorin gene expression was greater (P < 0.05) in s.c. than in i.m. adipose tissue of finished steers. A depot x background interaction for osteonectin (P < 0.01) and ferritin heavy chain (P = 0.03) gene expression was observed for steers slaughtered after grazing, indicating that nutritional management can affect gene expression in adipose tissue depots differently. No differences resulting from prefinishing nutritional background (HGW or NR) were noted in osteonectin, ferritin heavy chain, or decorin gene expression in i.m. adipose tissue collected from finished steers, which might have resulted from feeding steers to the same compositional endpoint. Our data suggest that nutritional background alters gene expression in adipose depots, and that depots are influenced differently.

Adipose Tissue↗

PubMed2004

Effect of live weight gain of steers during winter grazing: II. Visceral organ mass, cellularity, and oxygen consumption.

Two experiments were conducted to examine the effect of BW gain during winter grazing on mass, cellularity, and oxygen consumption of splanchnic tissues before and after the feedlot finishing phase. In each experiment, 48 fall-weaned Angus x Angus-Hereford steer calves were assigned randomly to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range supplemented with 0.91 kg/d of a 41% CP supplement (NR). At the end of winter grazing, four steers were selected randomly from each treatment for initial slaughter to measure organ mass, cellularity, and oxygen consumption. All remaining steers were placed into a feedlot and fed to the same backfat end point (1.27 cm). Six steers were selected randomly from each treatment for final organ mass, cellularity, and oxygen consumption. Initial empty BW (EBW) was greatest (P < 0.001) for HGW, intermediate for LGW, and least for NR steers in both Exp. 1 and 2 (355 > 263 > 207 +/- 6.5 kg and 337 > 274 > 205 +/- 8.7 kg, respectively). For both experiments, the initial total gastrointestinal tract (GIT; g/kg of EBW) proportional weight was greater (P < 0.05) in NR steers than in LGW, and LGW steers had greater (P < 0.05) initial GIT proportional weight than HGW steers. Proportional weight of total splanchnic tissues (TST; g/kg of EBW) did not differ (P < 0.19) among treatments. Initial duodenal RNA concentration and RNA:protein were greater (P < 0.02) in LGW than in HGW steers, and NR steers were intermediate. Initial in vitro liver O2 consumption was greater (P < 0.09) in HGW and LGW than in NR steers (34.5 > 16.9 mL/min), whereas initial small intestinal oxygen consumption was greater (P < 0.01) in LGW than in HGW and NR steers (12.1 > 5.2 mL/min). Ruminal papillae oxygen consumption did not differ (P < 0.55) among treatments. The rate of decrease of GIT (g x g EBW(-1) x d(-1)) during finishing was greater in NR than in HGW and LGW steers in both Exp. 1 and 2, but mesenteric fat (g x g EBW(-1) x d(-1)) increased for NR steers, resulting in a similar (P < 0.75) increase in TST across the finishing period for all treatments. Similar rates of increase in TST across the finishing phase corresponded with similar rates of live and carcass weight gain among treatments. Our data support the hypothesis that increased visceral organ mass increases maintenance energy requirements of growing cattle.

Animal Feed↗

PubMed2004

Effect of live weight gain of steers during winter grazing: I. Feedlot performance, carcass characteristics, and body composition of beef steers.

Two experiments were conducted to examine the effect of previous BW gain during winter grazing on subsequent growth, carcass characteristics, and change in body composition during the feedlot finishing phase. In each experiment, 48 fall-weaned Angus x Angus-Hereford steer calves were assigned randomly to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range (NR) supplemented with 0.91 kg/d of cottonseed meal. Winter grazing ADG (kg/d) for HGW, LGW, and NR steers were, respectively, 1.31, 0.54, 0.16 (Exp. 1) and 1.10, 0.68, 0.15 (Exp. 2). At the end of winter grazing, four steers were selected randomly from each treatment to measure initial carcass characteristics and chemical composition of carcass, offal, and empty body. All remaining steers were fed a high-concentrate diet to a common backfat end point. Six steers were selected randomly from each treatment for final chemical composition, and carcass characteristics were measured on all steers. Initial fat mass and proportion in carcass, offal, and empty body were greatest (P < 0.001) for HGW, intermediate for LGW, and least for NR steers in both experiments. Live BW ADG and gain efficiency during the finishing phase did not differ (P = 0.24) among treatments, but DMI (% of mean BW) for NR and LGW was greater (P < 0.003) than for HGW steers. Final empty-body composition did not differ (P = 0.25) among treatments in Exp. 1. In Exp. 2, final carcass and empty-body fat proportion (g/kg) was greater (P < 0.03) for LGW and NR than for HGW steers. Accretion of carcass fat-free organic matter was greater (P < 0.004) for LGW than for HGW and NR steers in Exp. 1, but did not differ (P = 0.22) among treatments in Exp. 2. Fat accretion in carcass, offal, and empty body did not differ (P = 0.19) among treatments in Exp. 1, but was greater (P < 0.05) for LGW and NR than for HGW steers in Exp. 2. Heat production by NR steers during finishing was greater (P < 0.02) than by HGW steers in Exp. 1 and 2. Differences in ADG during winter grazing and initial body fat content did not affect rate of live BW gain or gain efficiency during finishing. Feeding steers to a common backfat thickness end point mitigated initial differences in carcass and empty-body fat content. However, maintenance energy requirements during finishing were increased for nutritionally restricted steers that were wintered on dormant native range.

Adipose Tissue↗

PubMed2004

Effect of live weight gain of steers during winter grazing: III. Blood metabolites and hormones during feedlot finishing.

Two experiments were conducted using 48 Angus x Angus-Hereford steers in each experiment to determine the effect of previous winter grazing BW gain on jugular concentrations of metabolites and hormones during feedlot finishing. In each experiment, steers were randomly assigned to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range (NR) with 0.91 kg/d of a 41% CP (DM basis) supplement. Steers grazed for 120 or 144 d in Exp. 1 and 2, respectively. Plasma and serum were collected from all steers before placement into a feedlot, and six or seven times during finishing in Exp. 1 and 2, respectively. In Exp. 1, before steers entered the feedlot, concentrations of insulin, triiodothyronine (T3), and thyroxine (T4) were greater (P < 0.05) in HGW than in LGW or NR steers, and concentrations of IGF-I and plasma urea-N were greater (P < 0.05) in steers that grazed wheat pasture than in NR steers. In Exp. 2, concentrations of glucose, T3, T4, and IGF-I were greater (P < 0.05) in steers that grazed wheat pasture than NR steers. In Exp. 1 (P < 0.19) and 2 (P < 0.86), glucose concentration did not differ among treatments during finishing. In Exp. 1, insulin concentration across days on feed was greater for HGW than LGW steers, which were greater than for NR steers (treatment x day interaction, P < 0.03). In Exp. 2, insulin concentration increased (P < 0.001) as days on feed increased. Concentrations of IGF-I were greater in steers that had grazed wheat pasture, whereas the increase in IGF-I with increasing days on feed was greater for NR steers (treatment x day interaction, P < 0.003). Concentrations of T3 and T4 during finishing were greater (P < 0.001) in HGW and LGW than in NR steers in Exp. 1. In Exp. 2, T4 concentration also differed (P < 0.009) among treatments (HGW > LGW > NR). In Exp. 2, final concentration of glucose was greater (P < 0.01) in NR than in HGW and LGW steers, and serum insulin concentration was greater (P < 0.04) in NR than LGW steers. Final concentrations of T3 (P < 0.01) and T4 (P < 0.004) were greater in NR than in HGW steers. Our data show that previous BW gain can affect blood metabolites and hormones in steers entering the feedlot. However, lower concentrations of T3, T4, and IGF-I in steers when they entered the feedlot did not inhibit the growth response of previously restricted steers.

Adipose Tissue↗

PubMed2003

Effect of the live weight gain of steers during winter grazing on digestibility, acid-base balance, blood flow, and oxygen consumption by splanchnic tissues during adaptation and subsequent feeding of a high-grain diet.

Ten multicatherized steers were used in a completely random design to determine the effect of previous BW gain on blood flow, acid-base balance, and oxygen consumption across portal-drained viscera and liver of growing beef steers fed a high-grain diet. Treatments were high (1.31 +/- 0.09 kg/d) or low (0.68 +/- 0.07 kg/d) daily BW gain during an 82-d winter wheat pasture grazing period and a subsequent 37-d transition period. Blood flow, blood gas measurements, and oxygen consumption were determined on d 0, 14, 28, 42, and 64 of a high-grain finishing period. Compensatory growth was evident in low-gain steers; ADG (1.50 vs. 1.11 kg/d, P < 0.05) and gain efficiency (0.221 vs. 0.109 kg/kg, P < 0.01) were greater from d 14 through 28 than for high-gain steers. Arterial base tended (P < 0.12) to be greater in low-gain than in high-gain steers, whereas calculated HCO3- (mmol/L; P < 0.20) did not differ between treatments. Arterial O2 concentration was not different (P < 0.97) between treatments but increased (P < 0.001) with increasing days on feed. Portal blood flow increased with days on feed (P < 0.001) but did not differ (P < 0.34) between treatments. Hepatic blood flow scaled to metabolic BW was 19.7% greater (P < 0.02) in low-gain than in high-gain steers. Across the feeding period, O2 consumption and CO2 flux by PDV, liver, and total splanchnic tissue (TST) did not differ (P < 0.33) between treatments. However, TST O2 consumption (mmol/[h x kg BW(0.75)]) tended (P < 0.12) to be greater in low- than in high-gain steers. Compensating steers' arterial blood acid-base measurements did not change with days on feed, indicating that they were not more susceptible to metabolic acidosis than high-gain steers. However, steers that had lower BW gain before high-grain feeding exhibited increased hepatic blood flow and TST O2 consumption (metabolic BW basis) during the finishing period compared with high-gain steers. Greater hepatic blood flow and energy expenditure by TST of previously restricted steers might have facilitated compensatory growth.

Acid-Base Equilibrium↗

PubMed2002

Effects of supplementation on intake, digestion, and performance of beef cattle consuming fertilized, stockpiled bermudagrass forage.

Experiments were conducted to determine the effects of increasing supplement protein concentration on performance and forage intake of beef cows and forage utilization of steers consuming stockpiled bermudagrass forage. Bermudagrass pastures were fertilized with 56 kg of N/ha in late August. Grazing was initiated during early November and continued through the end of January each year. Treatments for the cow performance trials were: no supplement or daily equivalents of 0.2, 0.4, and 0.6 g of supplemental protein per kilogram of BW. Supplements were formulated to be isocaloric, fed at the equivalent of 0.91 kg/d, and prorated for 4 d/wk feeding. Varying the concentration of soybean hulls and soybean meal in the supplements created incremental increases in protein. During yr 1, supplemented cows lost less weight and condition compared to unsupplemented animals (P < 0.05). During yr 2, supplemented cows gained more weight (P = 0.06) and lost less condition (P < 0.05) compared to unsupplemented cows. Increasing supplement protein concentration had no affect on cumulative cow weight change or cumulative body condition score change. Forage intake tended to increase (P = 0.13, yr 1 and P = 0.07, yr 2) in supplemented cows. Supplement protein concentration did not alter forage intake. In a digestion trial, four crossbred steers were used in a Latin square design to determine the effects of supplement protein concentration on intake and digestibility of hay harvested from stockpiled bermudagrass pasture. Treatments were no supplement; or 0.23, 0.46, and 0.69 g of supplemental protein per kilogram of BW. Forage intake increased (P < 0.05) 16% and OM intake increased (P < 0.01) 30% in supplemented compared to unsupplemented steers. Diet OM digestibility increased (P = 0.08) 14.5% and total digestible OM intake increased (P < 0.05) 49% in supplemented compared to unsupplemented steers. Supplement protein concentration did not alter forage intake, total digestible OM intake, or apparent digestibility of OM or NDF. During the initial 30 d after first killing frost, beef cows did not respond to supplementation. However, later in the winter, supplementation improved utilization of stockpiled bermudagrass forage.

Animal Feed↗

PubMed2001

Performance of light vs heavy steers grazing Plains Old World bluestem at three stocking rates.

Live weight gains of light and heavy calves grazing Plains Old World bluestem at three stocking rates were evaluated during the summers of 1997 and 1998. Initial weights of mixed-breed light-weight steers (LHT) were 141 SD = 17 kg (n = 214) in 1997 and 160 SD = 23 kg (n = 193) in 1998. Initial weights of mixed-breed heavy steers (HWT) were 265 SD = 17 kg (n = 115) in 1997 and 248 SD = 13 kg (n = 126) in 1998. Initial stocking rates for both sizes of steers were as follows: light, 392 kg of live weight/ha; moderate, 504 kg of live weight/ha (increased to 616 kg live weight/ha in 1998); and heavy, 840 kg of live weight/ ha. Averaged gain and gain/hectare are reported as stocking rate by steer type within year. Heavy steers had greater ADG than LHT steers during both years. Forage intake, expressed as a percentage of BW, was greater (P = 0.05) for LHT (3.1%) than for HWT (2.8%) calves. Grazing time (min/d; 1998 only) was greater (P = 0.05) for LHT (665) than for HWT (624) steers. Forage CP and in vivo digestible organic matter (DOM) were slightly greater (P < 0.05) in pastures grazed by HWT vs LHT cattle. Gain/hectare was greater (P < 0.05) for LHT than for HWT calves at all three stocking rates during both years. A linear decline in ADG was observed (P < 0.07) as stocking rates increased for HWT steers in 1997 and LHT steers in 1998. However, ADG did not decline with increasing stocking rate for LHT calves during 1997 or HWT calves during 1998. Forage intake was not different among stocking rates in either 1997 or 1998. Grazing time was greatest (P < 0.05) for steers in the moderate and heavy stocking rates. Forage in vivo DOM decreased (P < 0.05) as stocking rate increased. Both LHT and HWT steers had lower (P < 0.05) ADG at all three stocking rates during 1998 compared with 1997. Despite lower ADG, LHT steers had greater gain/hectare than HWT steers during both 1997 and 1998.

Animal Husbandry↗

PubMed2000

Effects of supplemental zinc and manganese on ruminal fermentation, forage intake, and digestion by cattle fed prairie hay and urea.

One in vitro and one in vivo metabolism experiment were conducted to examine the effects of supplemental Zn on ruminal parameters, digestion, and DMI by heifers fed low-quality prairie hay supplemented with urea. In Exp. 1, prairie hay was incubated in vitro for 24 h with five different concentrations of supplemental Zn (0, 5, 10, 15, and 20 ppm) and two concentrations of supplemental Mn (0 and 100 ppm), both provided as chloride salts. Added Mn increased (P < 0.02) IVDMD, but added Zn linearly decreased (P < 0.03) IVDMD. Added Zn tended to increase the amount of residual urea linearly (P < 0.06) at 120 min and quadratically (P < 0.02) at 180 min of incubation, although added Mn counteracted these effects of added Zn. Six 363-kg heifers in two simultaneous 3 x 3 Latin squares were fed prairie hay and dosed once daily via ruminal cannulas with urea (45 or 90 g/d) and with Zn chloride to provide the equivalent of an additional 30 (the dietary requirement), 250, or 470 ppm of dietary Zn. After a 7-d adaptation period, ruminal contents were sampled 2, 4, 6, 12, 18, 21, and 24 h after the supplement was dosed. Supplemental Zn did not alter prairie hay DMI (mean = 4.9 kg/d) or digestibility, although 470 ppm added Zn tended to decrease (P < 0.06) intake of digestible DM, primarily due to a trend for reduced digestibility with 470 ppm supplemental Zn. Zinc x time interactions were detected for both pH (P = 0.06) and NH3 (P = 0.06). At 2 h after dosing, ruminal pH and ruminal ammonia were linearly decreased (P < 0.05; P < 0.01) by added Zn. At 5 h after feeding, ruminal pH was linearly increased (P < 0.05) by added Zn, suggesting that added Zn delayed ammonia release from urea. The molar proportion of propionate in ruminal fluid was linearly and quadratically increased (P < 0.02; P < 0.01) whereas the acetate:propionate ratio was linearly and quadratically decreased (P = 0.02; P < 0.05) by added Zn. Through retarding ammonia release from urea and increasing the proportion of propionate in ruminal VFA, Zn supplementation at a concentration of 250 ppm may decrease the likelihood of urea toxicity and increase energetic efficiency of ruminal fermentation.

Animal Feed↗

PubMed1999

Effects of implants on daily gains of steers wintered on dormant native tallgrass prairie, subsequent performance, and carcass characteristics.

Fall-weaned crossbred steer calves (n = 300; 184 +/- 2.9 kg) received either no implant (Control) or were implanted with Synovex-C (SC = 10 mg estradiol benzoate + 100 mg progesterone), Synovex-S (SS = 20 mg estradiol benzoate + 200 mg progesterone), or Revalor-G (RG = 8 mg estradiol-17beta + 40 mg trenbolone acetate) to determine the effects of implants on weight gain during winter grazing on dormant tallgrass prairie, subsequent grazing and finishing performance, and carcass characteristics. Steers grazed two dormant tallgrass prairie pastures from October 16, 1996, until March 29, 1997 (164 d), and received 1.36 kg/d of a 25% CP supplement that supplied 100 mg of monensin/steer. Following winter grazing, all steers were implanted with Ralgro (36 mg zeranol) and grazed a common tallgrass prairie pasture until July 17 (110 d). After summer grazing, all steers were implanted with Revalor-S (24 mg estradiol-17beta + 120 mg trenbolone acetate), and winter implant treatment groups were equally allotted to four feedlot pens. Steers were harvested November 17, 1997, after a 123-d finishing period. Daily gains during the winter grazing phase averaged .28, .32, .32, or .35 kg/d, respectively, for Control, SC, SS, or RG steers and were greater (P < .01) for implanted steers than for Controls. Summer daily gains were similar (1.05 +/- .016 kg/d; P > or = .61) for all treatment groups. Feedlot daily gains were also similar (1.67 +/- .034 kg/d; P > or = .21), with implanted steers weighing 14 kg more than Control steers (P = .05) at harvest, despite similar management during summer grazing and feedlot phases. Control steers tended (P = .06) to have lower yield grades. There were no differences (P = .99) in marbling between implanted and nonimplanted steers. Steers implanted during the wintering phase had increased skeletal and overall (P < .01) carcass maturities compared with nonimplanted steers, which resulted in more "B" and "C" maturity carcasses. Because carcass maturity score affects quality grade, the increased maturities of implanted steers resulted in a $9.04 decrease in carcass value/100 kg (P < .01) compared with Controls. The results of this study indicate that growth-promoting implants are efficacious for cattle wintered on dormant native range despite low daily gains. This increased weight is maintained through the summer grazing and feedlot phases; however, the benefit of the increased weight may be offset by decreased carcass quality grade and value due to increased carcass maturity.

Anabolic Agents↗

PubMed1995

Influence of high-starch vs high-fiber energy supplements on performance of stocker cattle grazing wheat pasture and subsequent feedlot performance.

A 3-yr study was conducted to determine effects of high-starch (HS) or high-fiber (HF) energy supplements on performance of fall-weaned steer calves (n = 192, Exp. 1 and 2; n = 84, Exp. 3) grazing winter wheat pasture (Triticum aestivum variety 2157) and subsequent feedlot performance. The steers received 1) no supplement (CL) other than free-choice access to a commercial mineral mixture or 2) were hand-fed 6 d/wk either a corn-based HS supplement, or 3) a soybean hull/wheat middling-based HF supplement. In Exp. 1 (1989-1990), a fourth treatment provided ad libitum access to the HF supplement (SFHF). Supplements contained 88 mg of monensin/kg and the combination of ionophore, minerals and salt (8%) was used to limit intake of the SFHF supplement. Target level of daily consumption of all supplements was .75% of mean BW. Stocking density was increased by 33% (i.e., from 1.24 to 1.65 steers/ha) in Exp. 1 and 3, and by 22 to 44% in Exp. 2 when supplements were fed. Subsequent to grazing wheat pasture in Exp. 2 and 3, feedlot performance and carcass quality (Exp. 2 only) of the cattle were measured. Over the 3-yr period (pooled analysis), mean daily supplement consumption was .65% BW. Daily gains were increased (P < .001) .15 kg by supplementation and were .92, 1.06, and 1.08 kg for CL, HS, and HF, respectively. Daily gains were not influenced (P > .45) by type of energy supplement. Mean supplement conversions (kilograms asfed.kilogram of increased gain-1.hectare-1) were 5.4 for HS and 5.0 for HF and did not differ (P > .95). Subsequent feedlot daily gain was decreased .09 kg (P < .05) by supplementation in Exp. 2 but not in Exp. 3 (P > .80). This supplementation program for growing cattle on wheat pasture allowed stocking density to be increased by approximately one-third and increased daily gains by .15 kg.

Animal Feed↗

PubMed1995

Effect of protein supplementation on forage intake and nitrogen balance of lambs fed freshly harvested wheat forage.

Wether lambs (mean BW = 32 kg) fed wheat forage freshly harvested daily (Exp. 1, n = 28; Exp. 2, n = 25) were used to evaluate the effects of supplemental energy and protein on forage intake, diet digestibility, and N retention. Experiment 1 was conducted in the winter of 1988 and the four treatments were 1) CONTROL, no supplement; 2) ENERGY, low-protein corn-based supplement; 3) CSM, 22% CP supplement with cottonseed meal; and 4) CGM, 22% CP supplement with corn gluten meal. Experiment 2 was conducted in the spring of 1989, and the five treatments were 1) CONTROL; 2) ENERGY; 3) CSM, 23% CP with cottonseed meal; 4) FTM, 25% CP supplement with feather meal and corn gluten meal; and 5) BM, 25% CP supplement with blood meal and corn gluten meal. All supplements were isoenergetic and composed 22 and 24% of total DMI in Exp. 1 and 2, respectively. In Exp. 1, forage intake was not affected but total and digestible DMI were increased (P < .01) by energy and protein supplementation. Protein supplements did not (P > .10) increase total and digestible DMI compared to ENERGY supplementation but tended (P < .10) to increase N retention (g/d). In Exp. 2, digestible DMI and N retention did not differ among the five treatments. Results suggest that lambs consuming wheat forage in the vegetative stage (Exp. 1) will have greater digestible DMI if supplemental energy or protein is provided. When more mature wheat forage was fed (Exp. 2), energy seemed to limit animal performance.

Animal Feed↗

PubMed1991

Nutritive value of ammoniated wheat straw fed to cattle.

The effects of ammoniation of wheat straw on site and extent of digestion of nutrients by cattle and the nutritive value of the N added to the straw were studied using eight Hereford steers during three consecutive 21-d periods and analyzed in an incomplete block design with steers and periods as orthogonal blocking factors. The steers, approximately 30 mo old and weighing 360 +/- 24 kg, were cannulated in the rumen, duodenum and ileum. Diets consisted of untreated (US) or ammoniated (AS) wheat straw supplemented with a mineral-vitamin mixture. Steers fed US received four supplements in which the percentages of supplemental N from soybean meal (SBM) and urea were 0:100; 33:67; 67:33 or 100:0. Percentage of N and in vitro DM digestibility values were increased in US by the ammoniation process from .42 to 1.82 and 34.8 to 54.3, respectively. Total tract digestibility of OM consumed was similar among treatments, although total tract digestibility of dietary N was decreased by ammoniation. Ammoniation doubled (P less than .05) the synthesis of microbial N per unit of dietary OM truly fermented in the rumen. When SBM and urea were fed in combination they depressed (P less than .10) microbial N flow and synthesis of microbial N per unit of OM truly fermented more than each depressed flow and synthesis individually. The nutritive value of the increased N of AS was equivalent to between 67 and 100% of SBM N based on amounts (g/d) of non-ammonia N apparently digested in the small intestine.

Ammonia↗

PubMed1991

Energy and protein supplementation of ammoniated wheat straw diets for growing steers.

Eighty-eight yearling beef steers (308 +/- 1.4 kg) were used in two separate trials to determine the protein-sparing value of the N added to wheat straw during the ammoniation process and to determine the effects of supplementing ammoniated straw diets with energy and ruminal escape protein. In Exp. 1, steers were fed untreated straw (US) with either 0, 150, or 500 g of soybean meal (SBM) for 88 d. The addition of SBM to US diets increased (P less than .01) straw intake and average daily gains (ADG), indicating that N was limiting. When ammoniated straw (AS) was substituted for US, the N in the AS was used as efficiently as 500 g of SBM for growth. In Exp. 2, steers had ad libitum access to AS with three levels of supplemental corn (0, 1.23, or 2.45 kg DM.animal-1.d-1) either with or without .41 kg DM of corn gluten meal (CGM) added. Straw intake decreased (P less than .01) as the amount of corn in the diet was increased, but ADG increased (P less than .01) with the addition of corn. Straw consumption was not altered by the addition of CGM, but ADG was increased (P less than .01) by an average .35 kg by CGM. Rumen and blood N components indicated that the N from AS was contributing to the ruminal N pool and that CGM was compensating for microbial protein deficiencies postruminally.

Ammonia↗

PubMed1991

Effects of lactational status on forage intake, digestibility, and particulate passage rate of beef cows supplemented with soybean meal, wheat middlings, and corn and soybean meal.

Sixteen mature, lactating (453 kg) and 16 nonlactating (487 kg) Hereford and Angus x Hereford cows were used to determine effects of different dietary supplements and lactational status on forage intake, digestibility, and particulate passage rate. Supplement treatments and amounts fed (kg/d) were as follows: control, 0; and equal daily amounts of CP from soybean meal (SBM), 1.36; wheat middlings (WM), 3.41; or a blend of corn and soybean meal (corn-SBM; 22% corn and 76% SBM), 3.41. Cows were fed supplements at 0800 and had ad libitum access to prairie hay (4.9% CP) in stalls from 0800 to 1100 and from 1300 to 1600 for three 17-d periods. Lactational status and supplement type did not interact (P greater than .50) for hay DMI, DM digestibility, or particulate passage rate. Cows fed SBM ate more hay DM (P less than .01) and had greater hay DM digestibility (P less than .01) than did cows in other treatment groups. Average hay DMI (kg/100 kg of BW) was 1.95, 2.16, 1.94, and 1.89, and hay DM digestibility was 52, 61, 55, and 53% for control, SBM, WM, and corn-SBM supplements, respectively. Total diet DM digestibility was increased by supplementation (P less than .01), but no differences (P greater than .18) were observed among supplements. Lactating cows ate more (P = .13) hay DM (2.11 vs 1.87 kg/100 kg of BW) and had greater (P less than .05) fecal output (4.6 vs 4.3 kg/d) than did nonlactating cows. Dry matter digestibility and particulate passage rate were not affected (P greater than .35) by lactational status.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1989

Effects of supplemental silage on forage intake and utilization by steers grazing wheat pasture or bermudagrass.

Seven trials were conducted to determine the effects of increasing amounts of silage (corn, wheat or sorghum) on forage intake, gastrointestinal tract fill, fecal output and ruminal flow and degradation of forage by cattle grazing wheat pasture or bermudagrass. In each of 3 yr, 24 steers grazed a common wheat or bermudagrass pasture and were randomly allocated to four treatments (0, .35, .70 or 1.05 kg silage DM.100 kg body weight-1.d-1). Intake and ruminal flow of forage were measured by feeding a single pulse dose of Yb-labeled forage followed by collection of fecal samples for 4 to 5 d and fitting Yb concentrations to a one-compartment, age-dependent model. Ruminal digestion kinetics of wheat forage were estimated in situ using eight ruminally cannulated steers fed 0 or .55 kg sorghum silage DM.100 kg body weight-1.d-1. Supplemental silage decreased wheat forage (P less than .10) and bermudagrass (P less than .01) intake linearly. However, total forage intake of bermudagrass plus silage increased linearly (P less than .05). Each kilogram of added silage DM decreased DM intake of wheat forage by .66 +/- .25 and of bermudagrass by .63 +/- .17 kg. Flow and turnover of wheat forage or bermudagrass were not altered (P greater than .15) by supplemental silage. Silage consumption increased extent of ruminal degradation of wheat forage DM (P less than .05; 63.1 vs 52.5%), indicating a positive associative effect of silage on wheat forage utilization.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1989

Mutagenicity of dimethyl heteroaromatic triazenes in the Ames test: the role of hydrophobicity and electronic effects.

The mutagenicities of five heterocyclic 3,3-dimethyltriazenes have been evaluated in the Ames test. The octanol-water partition coefficients (P) for these triazenes have been measured, and their electron distributions and molecular orbital energies were calculated using the MNDO semiempirical molecular orbital method. Molecular structures of three triazenes have been determined using X-ray crystallography. The mutagenicities of these five triazenes, which range from nearly inactive to very highly mutagenic, are well predicted by quantitative structure-activity relationships that had been derived previously for the mutagenicity of aryltriazenes. The form of these equations indicates that more hydrophobic and more electron-rich triazenes are more active in the Ames test. This supports the hypothesis that the ease of initial triazene activation by cytochrome P-450 governs the mutagenicity of these compounds.

Biotransformation↗

PubMed1987

The prophylactic effect of corn supplementation on experimental nitrate intoxication in cattle.

Sodium nitrate was administered through rumen cannulae to produce NO-3 intoxication in four cows (382 to 445 kg body wt) fed prairie grass hay and a protein-mineral supplement. The cows were fed 0, 1.6 or 3.2 kg of dry rolled corn daily for 10 d prior to sodium nitrate administration. Sodium nitrate administration was followed by a marked increase in intraruminal NO-2 and NH3 and blood NO-2 and methemoglobin. Six of eight cows fed 0 and 1.6 kg of corn were given methylene blue to treat severe methemoglobinemia, while none of the cows fed 3.2 kg corn required such therapy. Feeding of 3.2 kg of corn protected against nitrate poisoning by reducing intraruminal nitrite and blood methemoglobin (P less than .05).

Animal Feed↗