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ABSTRACT: Feed cost for beef cattle is the largest expense incurred by cattle producers. The development of genetic markers to enhance selection of more efficient animals that require less feed while still achieving acceptable levels of production has the potential to substantially reduce production costs. A genome-wide marker association approach based on the Illumina BovineSNP50 BeadChip™ was used to identify genomic regions affecting average daily feed intake (ADFI), average daily gain (ADG) and residual feed intake traits in a population of 1159 crossbred steers. This approach identified a region on BTA14 from 22.02 to 23.92 Mb containing several single-nucleotide polymorphisms (SNPs) that have significant association with at least one of the traits. Two genes in this region, lysophospholipase 1 (LYPLA1) and transmembrane protein 68 (TMEM68), appeared to be logical positional and functional candidate genes. LYPLA1 deacylates ghrelin, a hormone involved in the regulation of appetite in the rat stomach, while TMEM68 is expressed in bovine rumen, abomasum, intestine and adipose tissue in cattle, and likely affects lipid biosynthetic processes. SNPs lying in or near these two genes were identified by sequencing a subset of animals with extreme phenotypes. A total of 55 SNPs were genotyped and tested for association with the same population of steers. After correction for multiple testing, five markers within 22.79-22.84 Mb, located downstream of TMEM68, and between TMEM68 and the neighbouring gene XKR4, were significant for both ADFI and ADG. Genetic markers predictive of feed intake and weight gain phenotypes in this population of cattle may be useful for the identification and selection of animals that consume less feed, although further evaluation of these markers for effects on other production traits and validation in additional populations will be required.
Animal Genetics 04/2012; 43(2):216-9. · 2.40 Impact Factor
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ABSTRACT: With the high cost of feed for animal production, genetic selection for animals that metabolize feed more efficiently could result in substantial cost savings for cattle producers. The purpose of this study was to identify DNA markers predictive for differences among cattle for traits associated with feed efficiency. Crossbred steers were fed a high-corn diet for 140 days and average daily feed intake (ADFI), average daily gain (ADG), and residual feed intake (RFI) phenotypes were obtained. A region on chromosome 14 was previously associated with RFI in this population of animals. To develop markers with the highest utility for predicting an animal's genetic potential for RFI, we genotyped additional markers within this chromosomal region. These polymorphisms were genotyped on the same animals (n = 1066) and tested for association with ADFI, ADG and RFI. Six markers within this region were associated with RFI (P ≤ 0.05). After conservative correction for multiple testing, one marker at 25.09 Mb remained significant (P = 0.02) and is responsible for 3.6% of the RFI phenotypic variation in this population of animals. Several of these markers were also significant for ADG, although none were significant after correction. Marker alleles with positive effects on ADG corresponded to lower RFI, suggesting an effect increasing growth without increasing feed intake. All markers were also assessed for their effects on meat quality and carcass traits. All of the markers associated with RFI were associated with adjusted fat thickness (AFT, P ≤ 0.009) and three were also associated with hot carcass weight (HCW, P ≤ 0.003). Marker alleles associated with lower RFI were also associated with reduced AFT, and if they were associated for HCW, the effect was an increase in weight. These markers may be useful as prediction tools for animals that utilize feed more efficiently; however, validation with additional populations of cattle is required.
Animal Genetics 02/2012; 43(5):599-603. · 2.40 Impact Factor
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Animal Genetics 02/2012; 43(1):112. · 2.40 Impact Factor
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ABSTRACT: Growth, feed intake, and temperament indicator data, collected over 5 yr on a total of 1,141 to 1,183 mixed-breed steers, were used to estimate genetic and phenotypic parameters. All steers had a portion of Hereford, Angus, or both as well as varying percentages of Simmental, Charolais, Limousin, Gelbvieh, Red Angus, and MARC III composite. Because the steers were slaughtered on various dates each year and the animals thus varied in days on feed, BW and feed data were adjusted to a 140-d feeding period basis. Adjustment of measures of feed efficiency [G:F or residual feed intake (RFI), intake adjusted for metabolic body size, and BW gain] for body fatness recorded at slaughter had little effect on the results of analyses. Average daily gain was less heritable (0.26) than was midtest BW (MBW; 0.35). Measures of feed intake had greater estimates of heritability, with 140-d DMI at 0.40 and RFI at 0.52; the heritability estimate for G:F was 0.27. Flight speed (FS), as an indicator of temperament, had an estimated heritability of 0.34 and a repeatability of 0.63. As expected, a strong genetic (0.86) correlation was estimated between ADG and MBW; genetic correlations were less strong between DMI and ADG or MBW (0.56 and 0.71). Residual feed intake and DMI had a genetic correlation of 0.66. Indexes for phenotypic RFI and genotypically restricted RFI (no correlation with BW gain) were compared with simple economic indexes incorporating feed intake and growth to elucidate expected selection responses under different criteria. In general, few breed differences were detected across the various measurements. Heterosis contributed to greater DMI, RFI, and MBW, but it did not significantly affect ADG, G:F, or FS. Balancing output (growth) with input costs (feed) is needed in practicing selection, and FS would not be recommended as an indicator trait for selection to change feed efficiency. An index including BW gain and RFI produced the best economic outcome.
Journal of Animal Science 05/2011; 89(11):3452-9. · 2.10 Impact Factor
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W M Snelling,
M F Allan,
J W Keele,
L A Kuehn,
R M Thallman,
G L Bennett, C L Ferrell,
T G Jenkins,
H C Freetly,
M K Nielsen,
K M Rolfe
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ABSTRACT: The effects of individual SNP and the variation explained by sets of SNP associated with DMI, metabolic midtest BW, BW gain, and feed efficiency, expressed as phenotypic and genetic residual feed intake, were estimated from BW and the individual feed intake of 1,159 steers on dry lot offered a 3.0 Mcal/kg ration for at least 119 d before slaughter. Parents of these F(1) × F(1) (F(1)(2)) steers were AI-sired F(1) progeny of Angus, Charolais, Gelbvieh, Hereford, Limousin, Red Angus, and Simmental bulls mated to US Meat Animal Research Center Angus, Hereford, and MARC III composite females. Steers were genotyped with the BovineSNP50 BeadChip assay (Illumina Inc., San Diego, CA). Effects of 44,163 SNP having minor allele frequencies >0.05 in the F(1)(2) generation were estimated with a mixed model that included genotype, breed composition, heterosis, age of dam, and slaughter date contemporary groups as fixed effects, and a random additive genetic effect with recorded pedigree relationships among animals. Variance in this population attributable to sets of SNP was estimated with models that partitioned the additive genetic effect into a polygenic component attributable to pedigree relationships and a genotypic component attributable to genotypic relationships. The sets of SNP evaluated were the full set of 44,163 SNP and subsets containing 6 to 40,000 SNP selected according to association with phenotype. Ninety SNP were strongly associated (P < 0.0001) with at least 1 efficiency or component trait; these 90 accounted for 28 to 46% of the total additive genetic variance of each trait. Trait-specific sets containing 96 SNP having the strongest associations with each trait explained 50 to 87% of additive variance for that trait. Expected accuracy of steer breeding values predicted with pedigree and genotypic relationships exceeded the accuracy of their sires predicted without genotypic information, although gains in accuracy were not sufficient to encourage that performance testing be replaced by genotyping and genomic evaluations.
Journal of Animal Science 02/2011; 89(6):1731-41. · 2.10 Impact Factor
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Animal Genetics 12/2010; 41(6):669. · 2.40 Impact Factor
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ABSTRACT: Records of individual feed intake (FI) and BW gain (GN) were obtained from the Germ Plasm Evaluation (GPE) program at US Meat Animal Research Center (USMARC). Animals were randomly assigned to pens. Only pens with 6 to 9 steers (n = 289) were used for this study (data set 1). Variance components and genetic parameters were estimated using data set 1. Estimated genetic values (EGV) for FI were calculated by 5 methods using single and 2-trait analyses: 1) individual FI and individual GN, 2) individual FI alone, 3) 2-trait with individual GN but with FI missing, 4) individual GN and pen total FI, and 5) pen total FI alone. Analyses were repeated but with some of the same records assigned artificially to 36 pens of 5 and 4 paternal half sibs per pen (data sets 2 and 3). Models included year as a fixed factor and birth and weaning weights, age on test, and days fed as covariates. Estimates of heritability were 0.42 +/- 0.16 and 0.34 +/- 0.17 for FI and GN. The estimate of the genetic correlation was 0.57 +/- 0.23. Empirical responses to selection were calculated as the average EGV for the top and bottom 10% based on rank for each method but with EGV from method 1 substituted for the EGV on which ranking was based. With data set 1, rank correlations between EGV from method 1 and EGV from methods 2, 3, 4, and 5 were 0.99, 0.53, 0.32, and 0.15, respectively. Empirical responses relative to method 1 agreed with the rank correlations. Accuracy of EGV for method 4 (0.44) was greater than for method 3 (0.35) and for method 5 (0.29). Accuracies for methods 4 and 5 were greater than indicated by empirical responses and correlations with EGV from method 1. Comparisons of the 5 methods were similar for data sets 2 and 3. With data set 2, rank correlations between EGV from method 1 and EGV from methods 3, 4, and 5 were 0.47, 0.64, and 0.62. Average accuracies of 56, 75, and 75% relative to method 1 (0.67) generally agreed with the empirical responses to selection. As expected, accuracy using pen total FI and GN to obtain EGV for FI was greater than using GN alone. With data set 1, empirical response to selection with method 4 was one-third of that for method 1, although average accuracy was 65% of that for method 1. With assignment of 5 paternal half sibs to artificial pens, using pen total FI and individual GN was about 81% as effective for selection as using individual FI and GN to obtain EGV for FI and was substantially more effective than use of GN alone.
Journal of Animal Science 02/2010; 88(6):1967-72. · 2.10 Impact Factor
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ABSTRACT: The objective of the study was to measure net AA flux rates across the portal-drained viscera (PDV) and liver in the presence and absence of abomasal glucose infusion. Decreasing the fraction of AA metabolized by the mucosal cells may increase the fraction of AA being released into the blood. A potential mechanism to reduce AA catabolism by mucosal cells is to provide an alternative source of energy. We hypothesized that increasing glucose flow to the small intestine would increase net appearance of AA across the PDV. Eighteen mature ewes with sampling catheters were placed on study. The experimental design was a split-plot with a complete randomized design on the whole-plot and a Latin-square subplot with 5 periods and incremental levels of protein infusion. One-half of the ewes received abomasal glucose infusions (3.84 g/h), and all ewes received each of 5 protein abomasal infusion levels over 5 periods (0, 2.6, 5.2, 7.8, and 10.5 g/h). Net PDV release of isoleucine, leucine, methionine, phenylalanine, aspartate, glutamate, glutamine, proline, serine, and tyrosine increased linearly with increased protein infusion, and net PDV release of histidine, lysine, threonine, valine, alanine, and glycine did not differ with protein infusion. Net hepatic glucose release decreased with glucose infusion. With the exception of histidine, phenylalanine, and valine, net hepatic AA uptake increased linearly with increased delivery of AA to the liver. Glucose infusion increased the hepatic lysine and valine uptake and decreased phenylalanine uptake. Based on the observations in the current study, we reject our hypothesis that glucose can spare AA metabolism by PDV tissue. Our findings suggest that hepatic gluconeogenesis can be increased in the presence of increased AA delivery to the liver and that hepatic gluconeogenesis can be decreased with increased absorption of dietary glucose. Our findings support the concept that for most AA, hepatic transport of AA can be described by mass action kinetics; however, the rates of hepatic uptake of specific AA are upregulated directly or indirectly by elevated glucose.
Journal of Animal Science 12/2009; 88(3):1093-107. · 2.10 Impact Factor
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ABSTRACT: Multiparous Alpine does (42) were used to determine how stage of lactation and dietary forage level affect body composition. The feeding and body composition portion of the study had a 2 x 3 factorial arrangement of treatments. Eighteen does were fed a 40% forage diet (40F) and 18 received a diet with 60% forage (60F) for approximately 2, 4, or 6 mo of lactation (59 +/- 1.3, 116 +/- 1.0, and 184 +/- 1.4 d, respectively), followed by determination of body composition (6 does per diet at each time of slaughter). Does were assigned sequentially to treatments as kidding occurred. The 60F diet had 20% more dehydrated alfalfa pellets than the 40F diet, with higher levels of corn and soybean meal and inclusion of supplemental fat in the 40F diet. Initial body composition measures were made with 6 other does a few days after kidding (0 mo; 4 +/- 0.6 d). Before parturition, does were fed a 50% concentrate diet free choice. Intake of dry matter was greater for 60F than for 40F, average daily gain tended to be affected by an interaction between diet and month (0, 24, 121, -61, 46, and 73 g), and 4% fat-corrected milk was less in mo 5 to 6 than earlier. Internal fat mass was greatest among times at 6 mo and greater for 40F than for 60F. Mass of the gastrointestinal tract was less for 40F than for 60F and decreased with increasing time in lactation. Concentrations of fat in the carcass (13.8, 13.1, 16.5, 11.2, 11.5, and 14.4%), noncarcass tissues (18.6, 24.2, 33.3, 14.3, 16.5, and 24.5%), and empty body (16.5, 18.7, 25.2, 12.9, 14.1, and 19.5% for 40F at 2 mo, 40F at 4 mo, 40F at 6 mo, 60F at 2 mo, 60F at 4 mo, and 60F at 6 mo, respectively) were affected by stage of lactation and diet. Based on daily change in tissue mass and energy, energy concentration in tissue mobilized or accreted was 16, 20, and 32 MJ/kg in 1 to 2, 3 to 4, and 5 to 6 mo of lactation, respectively. In conclusion, based on tissue mass, more energy was expended by the gastrointestinal tract with 60F than with 40F. Considerable internal fat appeared to be mobilized in early lactation, particularly with the diet moderate to high in forage, with more rapid and a greater magnitude of repletion by does consuming the diet lower in forage. The concentration of energy in tissue mobilized or accreted varied with stage of lactation, being considerably greater at 5 to 6 mo of lactation than earlier.
Journal of Dairy Science 08/2009; 92(7):3374-85. · 2.56 Impact Factor
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J E Wells,
S D Shackelford,
E D Berry,
N Kalchayanand,
M N Guerini,
V H Varel,
T M Arthur,
J M Bosilevac,
H C Freetly,
T L Wheeler, C L Ferrell,
M Koohmaraie
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ABSTRACT: The objective of this study was to determine if wet distillers grains with solubles (WDGS) from corn in diets affected Escherichia coli O157:H7 in growing and finishing cattle; steers (n = 603) were randomly assigned to diets with or without WDGS. Hide and fecal samples were collected monthly (October through June) from each animal for enumeration and enrichment of E. coli O157:H7. In the growing phase (0 or 13.9% WDGS diets), fecal prevalence for E. coli O157:H7 in steers fed a diet with WDGS was twice that of the prevalence in control steers (P < 0.001). In the finishing phase (0 or 40% WDGS diets), the average prevalence in feces (P < 0.001) and on hides (P < 0.001) was higher for cattle fed WDGS. The average percentage of fecal E. coli O157:H7 enumerable samples during the finishing phase for cattle fed WDGS was 2.7% compared with 0.1% for control steers (P < 0.001). The average percentage of E. coli O157:H7 enumerable hide samples was not different between diets, but the cattle fed WDGS had higher levels (P < 0.05) of the pathogen. Animals fed WDGS had higher levels of E. coli (P < 0.001), higher pH values (P < 0.001), and lower concentrations of L-lactate (P < 0.001) in feces than those values of the control steers. These results indicate that feeding 40% WDGS could increase the level and prevalence of E. coli O157:H7 in and on feedlot cattle when E. coli O157:H7 is seasonally low.
Journal of food protection 08/2009; 72(8):1624-33. · 1.94 Impact Factor
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J.E. Wells,
S.D. Shackelford,
E.D. Berry,
N. Kalchayanand,
M.N. Guerini,
V.H. Varel,
T.M. Arthur,
J.M. Bosilevac,
H.C. Freetly,
T.L. Wheeler, C.L. Ferrell,
M. Koohmaraie
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ABSTRACT: The objective of this study was to determine if wet distillers grains with solubles (WDGS) from corn in diets affected Escherichia coli O157:H7 in growing and finishing cattle; steers (n = 603) were randomly assigned to diets with or without WDGS. Hide and fecal samples were collected monthly (October through June) from each animal for enumeration and enrichment of E. coli O157:H7. In the growing phase (0 or 13.9% WDGS diets), fecal prevalence for E. coli O157:H7 in steers fed a diet with WDGS was twice that of the prevalence in control steers (P < 0.001). In the finishing phase (0 or 40% WDGS diets), the average prevalence in feces (P < 0.001) and on hides (P < 0.001) was higher for cattle fed WDGS. The average percentage of fecal E. coli O157:H7 enumerable samples during the finishing phase for cattle fed WDGS was 2.7% compared with 0.1% for control steers (P < 0.001). The average percentage of E. coli O157:H7 enumerable hide samples was not different between diets, but the cattle fed WDGS had higher levels (P < 0.05) of the pathogen. Animals fed WDGS had higher levels of E. coli (P < 0.001), higher pH values (P < 0.001), and lower concentrations of L-lactate (P < 0.001) in feces than those values of the control steers. These results indicate that feeding 40% WDGS could increase the level and prevalence of E. coli O157:H7 in and on feedlot cattle when E. coli O157:H7 is seasonally low.
Journal of food protection 07/2009; 72(8):1624-1633. · 1.94 Impact Factor
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ABSTRACT: Sixty growing 3/4 Boer x 1/4 Spanish (BS) and Spanish (SP) wethers were used to determine influences of diet and breed on growth and body composition. A pelleted 50% concentrate diet (CD) and a diet based on grass hay (HD) were fed for ad libitum intake. Six wethers of each breed were slaughtered at 0 wk (total of 12). Six wethers of each diet-breed combination were slaughtered at 14 and 28 wk (24 per time) after consumption of the CD or HD. Initial BW of fed wethers were 21.6 and 18.8 kg for BS and SP, respectively (SEM = 0.7). Average daily gain during the entire experiment was influenced by an interaction (P < 0.05) between breed and diet (199, 142, 44, and 50 g/d for BS:CD, SP:CD, BS:HD, and SP:HD, respectively). Carcass mass was greater (P < 0.05) for CD vs. HD (56.2, 56.2, 53.2, and 54.0% of empty BW for BS:CD, SP:CD, BS:HD, and SP:HD, respectively). Mass of the liver (2.11, 1.92, 2.00, and 1.98% of empty BW; SEM = 0.05) and gastrointestinal tract (5.50, 4.83, 8.43, and 8.36% of empty BW for BS:CD, SP:CD, BS:HD, and SP:HD, respectively; SEM = 0.16) tended (P < 0.07) to be influenced by an interaction between breed and diet. Mass of internal fat (12.2, 12.1, 3.4, and 3.4% empty BW for BS:CD, SP:CD, BS:HD, and SP:HD, respectively; SEM = 0.3) differed (P < 0.05) between diets. Energy in the carcass (320, 236, 87, and 79 MJ), noncarcass tissues (318, 237, 77, and 72 MJ), and empty body (638, 472, 164, and 150 MJ) ranked (P < 0.05) BS:CD > SP:CD > BS:HD and SP:HD. Empty body concentration of protein was 18.3, 17.5, 18.3, and 19.7% (SEM = 0.3) and of fat was 24.0, 23.4, 10.8, and 10.3% for BS:CD, SP:CD, BS:HD, and SP:HD, respectively (SEM = 0.6). Energy concentration in accreted tissue was 17.0, 18.7, 16.3, and 6.4 MJ/kg for CD:wk 1 to 14, CD:wk 15 to 28, HD:wk 1 to 14, and HD:wk 15 to 28, respectively (SEM = 1.4). In conclusion, relatively high growth potential of growing Boer crossbred goats with a moderate to high nutritional plane does not entail a penalty in realized growth when the nutritional plane is low. Body composition of growing Boer and Spanish goats is fairly similar regardless of growth rate. For growing meat goats other than with a prolonged limited nutritional plane, an average energy concentration in accreted tissue is 17.3 MJ/kg.
Journal of Animal Science 05/2009; 87(9):2913-23. · 2.10 Impact Factor
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ABSTRACT: Corn ethanol production removes starch and concentrates the remaining nutrients, including CP and minerals. When wet distillers grains with solubles (WDGS) are fed to cattle in place of corn, CP and minerals often exceed dietary needs. This may increase N emission, P run-off, and odor production. These variables are evaluated in this study. Crossbred steers (n = 160; 434 +/- 8 kg) were assigned in a completely randomized block design to 9 x 9 m pens with concrete floor (10 animals/pen; 4 pens/treatment). Steers were fed a finishing diet that contained 0, 20, 40, or 60% WDGS on a DM basis, and provided 13.3, 15.5, 20.6, or 24.9% CP, respectively. Two kilograms of manure slurry (14 to 23% DM) were collected from each pen monthly (Aug. 20, Sep. 24, and Oct. 22). Samples were analyzed immediately for odorants, DM, pH, NH(3), total alcohol, l-lactate, and concentrations of generic Escherichia coli. After incubation of the samples at 22 degrees C for 2, 4, 7, 10, 15, 21, and 28 d, samples were analyzed for methane production in addition to the above characteristics. Before incubation, NH(3), H(2)S, indole, phenol, isovalerate, isobutyrate, and acetate increased (P < 0.01) with increasing amounts of WDGS in the diet. Other odorants, including skatole, caproate, valerate, butyrate, and propionate, were greater (P < 0.01) in manure slurries from cattle fed 20 or 40% WDGS, compared to 0% WDGS. The l-lactate was greater (P < 0.01) in slurries from cattle fed 0% WDGS (447 mu mol/g of DM) compared with the other treatment slurries (14 to 15 mu mol/g of DM). After incubation, l-lactate contributed to lowered slurry pH (6.3, 7.1, 7.6, and 8.2, respectively, for 0, 20, 40, and 60% WDGS), which inhibited microbial fermentation, E. coli persistence, and methane production. Because of the favorable, more neutral pH in the 40 and 60% WDGS slurries, many of the odorant compounds were rapidly converted to methane during a 28-d static incubation. Escherichia coli O157:H7 inoculated into subsamples of the manure slurries exhibited behavior similar to that of naturally present generic E. coli, surviving in greater numbers longer (P < 0.05) in 20 and 40% WDGS slurries than in 0% WDGS. These data indicate feeding WDGS can increase odorants in manure slurries and extend the persistence of E. coli.
Journal of Animal Science 08/2008; 86(12):3617-27. · 2.10 Impact Factor
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ABSTRACT: We hypothesized that providing dried distillers grains with solubles (DDGS) would improve the N retention and use of nutrients by wethers fed a moderate-quality bromegrass hay. Additionally, we hypothesized that treatment effects on nutrient fluxes would be similar after 3, 6, or 9 wk on treatment. Chronic indwelling catheters were surgically implanted in a mesenteric artery, mesenteric vein, hepatic vein, and portal vein of 9 Suffolk x Dorset wethers (initial BW +/- SD = 57.4 +/- 6.1 kg). Wethers had ad libitum access to moderate-quality bromegrass hay (8.44% CP, DM basis) and received 100 g/d of either a corn-based (Corn, n = 4) or a DDGS-based (n = 5) supplement. There was no difference in DMI (P = 0.85) or DM digestibility (P = 0.46) between the 2 groups. There was a numerically greater N intake (21.5 vs. 18.4 g/d; P = 0.14) and N retention (4.4 vs. 2.5 g/d; P = 0.15) when wethers were supplemented with DDGS instead of Corn. Wethers fed DDGS had a greater (P = 0.008) release of alpha-amino N from the portal-drained viscera (PDV, 37.9 mmol/h) than those fed Corn (14.1 mmol/h). Similarly, there was a shift (P = 0.004) from a net splanchnic uptake to a net release of alpha-amino N in wethers fed DDGS (9.1 mmol/h) compared with those fed Corn (-9.6 mmol/h). However, there was no difference in ammonia release from the PDV (P = 0.49) or hepatic release of urea-N (P = 0.19) between the 2 treatments. There were very limited interactions between nutrient fluxes and the length of time after the initiation of treatments. However, there was a tendency (interaction, P = 0.07) for the PDV release of alpha-amino N to be greater at 6 and 9 wk after the initiation of the treatments than after 3 wk on treatment for wethers fed DDGS, although there was no difference over time for wethers fed the Corn supplement. Additionally, there were changes in numerous nutrient fluxes between 3 and 6 wk after the initiation of treatments regardless of treatment. These data indicate that DDGS is a viable supplement to enhance the nutriture of ruminants consuming moderate-quality forages. Additionally, these data indicate that the effects are discernible after 3 wk on treatment, with modest alterations in nutrient flux after additional time on treatment.
Journal of Animal Science 04/2008; 86(3):691-701. · 2.10 Impact Factor
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ABSTRACT: To quantify the relationship between DM consumption, the ability to sustain BW per unit of DMI (BW stasis), and days to reach BW equilibrium among diverse cattle breeds, weekly individual cow BW and DMI data were recorded for mature, nonpregnant, and nonlactating cows sampled from Angus, Braunvieh, Charolais, Hereford, Gelbvieh, Limousin, Pinzgauer, Red Poll, and Simmental breeds. Within each breed, cows were assigned to receive 1 of 4 daily DM allowances (56, 76, 93, or 111 g.BW(-0.75, kg)) of a ground alfalfa hay-corn grain-based diet. Cows were housed in pens (space for 4 animals/pen) in open-front barns and fed individually using head gates. During the first 60 d of the experiment, BW were recorded every 28 d, after which BW were recorded on a weekly basis until the cows were determined to have attained BW equilibrium. Individual cows were determined to be at BW equilibrium when the rate of weekly BW change did not differ from 0 over an 8-wk period. The number of days to reach BW equilibrium was not affected (P > 0.79) by breed but was affected by the daily DM allowance (P < 0.003). The number of days required to attain BW equilibrium was greater as the rate of feeding (g of DM fed.BW(-0.75)) increased and ranged from 103 to 136 d. Within breed linear and the pooled quadratic regressions were significant for BW. Observed breed differences varied with feeding rate. Weight stasis estimates for mature Red Poll cows (68.3 +/- 3.8) differed (P < 0.05) from estimates for all the breeds, with the exception of Limousin (72.0 +/- 3.8), Braunvieh (74.0 +/- 4.8), and Pinzgauer (75.5 +/- 3.8) cows at the lowest feeding rate. At the 111 g.BW(-0.75) daily DM allowance, the estimates for Limousin (82.2 +/- 3.8) were greater (P < 0.05) than for the other breeds, with the exception of the Pinzgauer (81.0 +/- 4.3) and Braunvieh (75.7 +/- 3.9), which were similar to the remaining breeds in the study (P > 0.05). The change in rank of breed estimates for BW stasis suggests a breed x nutrition interaction for BW stasis.
Journal of Animal Science 07/2007; 85(7):1787-92. · 2.10 Impact Factor
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ABSTRACT: We hypothesized that oscillation of the dietary CP concentration, which may improve N retention of finishing beef steers, would reduce production of manure odor compounds and total N inputs while yielding comparable performance. Charolais-sired steers (n = 144; 303 +/- 5 kg of initial BW) were used in a completely randomized block design (6 pens/treatment). The steers were fed to 567 kg of BW on the following finishing diets, which were based on dry-rolled corn: 1) low (9.1% CP), 2) medium (11.8% CP), 3) high (14.9% CP), or 4) low and high oscillated on a 48-h interval for each feed (oscillating). Steers fed low tended (P = 0.08) to have less DMI (7.80 kg/d) than steers fed medium (8.60 kg/d) or oscillating (8.67 kg/d), but not less than steers fed high (8.12 kg/d). Daily N intake was greatest (P < 0.01) for steers fed high (189 g), intermediate for medium (160 g) and oscillating (164 g), and least for low (113 g). The ADG was lower (P < 0.01) for steers fed low (1.03 kg) than for those fed medium (1.45 kg), high (1.45 kg), or oscillating (1.43 kg). Similarly, steers fed low had a lower adjusted fat thickness (P < 0.01) and yield grade (P = 0.05) and tended (P = 0.10) to have less marbling than steers fed the other 3 diets. In slurries with feces, urine, soil, and water, incubated for 35 d, nonsoluble CP was similar among slurries from steers fed medium, high, or oscillating, but was less (P < 0.01) in slurries from steers fed low. However, throughout the incubation period, slurries from steers fed high or oscillating had greater (P < 0.01) concentrations of total aromatics and ammonia than those from steers fed low or medium. Also, the slurries from steers fed oscillating had greater (P < 0.01) concentrations of branched-chain VFA than manure slurries from steers fed any of the other diets. These data indicate that although there is no apparent alteration in the performance of finishing steers fed diets with oscillation of the dietary protein, there may be undesirable increases in the production of compounds associated with malodor.
Journal of Animal Science 06/2007; 85(6):1487-95. · 2.10 Impact Factor
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ABSTRACT: We hypothesized that oscillation of the dietary CP concentrations would improve efficiency of N use and reduce N loss to the environment. Charolais-cross steers (n = 8; 315 +/- 21 kg of BW) were used in a replicated 4 x 4 Latin square design. The steers were allowed ad libitum access to the following diets: 1) 9.1% CP (low), 2) 11.8% CP (medium), 3) 13.9% CP (high), or 4) low and high oscillated on a 48-h interval on each diet (oscillating). Dry matter intake did not differ among treatments (P = 0.46), but N intake differed (P < 0.01) from 94 (low) to 131 (medium), 142 (high), and 133 g/d (oscillating), as designed. Dry matter digestibility increased (P < 0.01) from 71.8% (low) to 75.8% (medium), 77.7% (high), and 77.5% (oscillating). Nitrogen digestibility increased (P < 0.01) from 62.2% (low) to 67.2% (medium) to 70.1% (high) and 70.9% (oscillating). Nitrogen retention was greater (P < 0.01) in steers fed oscillating (55.0 g/d) than in the steers fed low (34.8 g/ d) or high (40.2 g/d), but N retention of steers fed medium (49.8 g/d) differed (P = 0.02) only from that of steers fed low. Urinary urea N did not differ between steers fed medium (19.5 g/d) or oscillating (21.3 g/d) but was lowest (P < 0.01) for those fed low (8.2 g/d) and greatest for those fed high (39.2 g/d). Daily heat production (kcal/BW(0.75)) tended (P = 0.09) to be less for the steers fed low (177) than those fed medium (189), high (188), or oscillating (182). Cumulative in vitro ammonia volatilization from the manure of steers fed oscillating was lower (P < 0.01) for the initial 5 d of incubation than from manure of those fed medium, but there was no difference after 11 d of incubation. Additionally, there was a decrease (P < 0.01) in in vitro ammonia volatilization as protein concentration in the diet decreased from high to medium to low. These data indicate that oscillation of the dietary protein improved N retention of finishing steers compared with those in high and low N diets and that these changes were great enough to correspondingly alter ammonia volatilization from manure.
Journal of Animal Science 06/2007; 85(6):1496-503. · 2.10 Impact Factor
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ABSTRACT: We hypothesized that oscillating dietary CP would improve N retention by increasing the uptake of endogenous urea N by portal drained viscera (PDV), compared with static dietary CP regimens. Chronic indwelling catheters were surgically implanted in the abdominal aorta, a mesenteric vein, a hepatic vein, and the portal vein of 18 growing Dorset x Suffolk wethers (44.6 +/- 3.6 kg of BW). Wethers had ad libitum access to the following diets in a completely randomized block design: 1) Low (9.9% CP), 2) Medium (12.5% CP), or 3) Low and High (14.2% CP) diets oscillated on a 48-h interval (Osc). Dry matter intake was greater (P = 0.04) for the Osc diet (1,313 g/d) than the Low diet (987 g/d) and was intermediate for the Medium diet (1,112 g/d). Nitrogen intake was not different between the wethers fed the Osc (25.4 g/d) and Medium diets (22.2 g/d), but was lower (P < 0.01) in wethers fed the Low diet (16.0 g/d). Wethers fed the Osc diet (6.7 g/d) retained more (P < 0.04) N than did those fed the Medium diet (4.0 g/d). Hepatic arterial blood flow was not different (P = 0.81) between wethers fed the Osc (31 L/h) or Medium diet (39 L/h) but was greater (P = 0.05) in wethers fed the Low diet (66 L/h). Net release of alpha-amino N by the PDV did not differ (P = 0.90) between the Low (37.8 mmol/h) and Medium diets (41.5 mmol/h) or between the Osc (53.0 mmol/h) and Medium diets (P = 0.29). Net PDV release of ammonia N was less (P = 0.05) for the Low diet than for the Medium diet, and this was accompanied by a similar decrease (P = 0.04) in hepatic ammonia N uptake. Urea N concentrations tended to be (P = 0.06) less in arterial, portal, and hepatic blood in wethers fed the Low diet compared with those fed the Medium diet. Wethers fed the Osc diet tended (P = 0.06) to have a greater PDV uptake of urea N than did those fed the Medium diet, but there was no difference between the Osc and Medium diets (P = 0.72) in hepatic urea N release. Net PDV uptake of glutamine tended to be greater (P < 0.07) in wethers fed the Low diet (6.7 mmol/h) than those fed the Medium diet (2.7 mmol/h). These data indicate that oscillating dietary protein may improve N retention by increasing endogenous urea N uptake by the gastrointestinal tract.
Journal of Animal Science 05/2007; 85(4):997-1005. · 2.10 Impact Factor
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ABSTRACT: Three beef cattle diets were assessed for their potential to produce odorous compounds from cattle feces excreted during the growing and finishing periods. Eight pens containing 51 steers of varying proportions of Brahman and MARC III genotypes were fed either a chopped bromegrass hay diet or a corn silage diet for a 119-d growing period. After the growing period, all steers were switched to the same high-corn finishing diet (high corn) and fed to a target weight of 560 kg (finishing period). Fecal slurries were prepared from a composite of fresh fecal pats collected in each pen during both periods and incubated anaerobically. In additional flasks, starch, protein, or cellulose was added to the composite fecal subsamples to determine the preferred substrates for fermentation and odorous compound production. The content and composition of the fermentation products varied both initially and during the incubation, depending on the diet fed to the steers. The corn silage and high corn feces had the greater initial content of VFA (381.0 and 524.4 micromol/g of DM, respectively) compared with the bromegrass feces (139.3 micromol/g of DM) and accumulated more VFA than the bromegrass feces during the incubation. l-Lactic acid and VFA accumulation in the high corn and corn silage feces was at the expense of starch, based on starch loss and the production of straight-chain VFA. In the bromegrass feces, accumulation of branched-chain VFA and aromatic compounds and the low starch availability indicated that the protein in the feces was the primary source for odorous compound production. Substrate additions confirmed these conclusions. We conclude that starch availability was the primary factor determining accumulation and composition of malodorous fermentation products, and when starch was unavailable, fecal microorganisms utilized protein.
Journal of Animal Science 10/2006; 84(9):2533-45. · 2.10 Impact Factor
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ABSTRACT: This study assessed the influence of cattle genotype and diet on the carriage and shedding of zoonotic bacterial pathogens and levels of generic Escherichia coli in feces and ruminal contents of beef cattle during the growing and finishing periods. Fifty-one steers of varying proportions of Brahman and MARC III [0 (15), 1/4 (20), 1/2 (7), and 3/4 Brahman (9)] genotypes were divided among 8 pens, such that each breed type was represented in each pen. Four pens each were assigned to 1 of 2 diets [100% chopped bromegrass hay or a diet composed primarily of corn silage (87%)] that were individually fed for a 119-d growing period, at which time the steers were switched to the same high-concentrate, corn-based finishing diet and fed to a target weight of 560 kg. Feces or ruminal fluid were collected and analyzed at alternating intervals of 14 d or less. Generic E. coli concentrations in feces or ruminal fluid did not differ (P > 0.10) by genotype or by growing diet in the growing or finishing periods. However, the concentrations in both feces and ruminal fluid increased in all cattle when switched to the same high-corn diet in the finishing period. There was no effect (P > 0.25) of diet or genotype during either period on E. coli O157 shedding in feces. Forty-one percent of the steers were positive for Campylobacter spp. at least once during the study, and repeated isolations of Campylobacter spp. from the same steer were common. These repeated isolations from the same animals may be responsible for the apparent diet (P = 0.05) and genotype effects (P = 0.02) on Campylobacter in feces in the finishing period. Cells bearing stx genes were detected frequently in both feces (22.5%) and ruminal fluid (19.6%). The number of stx-positive fecal samples was greater (P < 0.05) for 1/2 Brahman steers (42.9%) than for 1/4 Brahman (25.0%) or 3/4 Brahman steers (22.2%), but were not different compared with MARC III steers (38.3%). The greater feed consumption of 1/2 Brahman and MARC III steers may have resulted in greater starch passage into the colon, accompanied by an increase in fecal bacterial populations, which may have further improved the ability to detect stx genes in these cattle. There was no correlation between either ADG or daily DMI and the number of positive samples of E. coli O157, Campylobacter spp., or stx genes, which agrees with our current understanding that these microorganisms occur commonly in, and with no measurable detriment to, healthy cattle.
Journal of Animal Science 09/2006; 84(9):2523-32. · 2.10 Impact Factor
