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ABSTRACT: Effective tick management on grazing animals is facilitated by accurate noninvasive detection methods. Fecal analysis provides information about animal health and nutrition. Diet affects fecal composition, stress may do likewise. The constituents in feces which may be affected by tick burdens and in turn affect near infrared spectra have not been reported. Our objective was to examine the interaction between plane of nutrition and tick burden on fecal composition in cattle. Angus cross steers (n = 28, 194 ± 3.0 kg) were assigned to one of four treatments (n = 7 per group) in a 2 x 2 factorial design: moderate (14.0 ± 1.0% CP, 60 ± 1.5% TDN) vs. low (9.0 ± 1.0% CP, 58 ± 1.5% TDN) plane of nutrition, and control (no tick) vs. tick treatment (infestation of 300 pair of adult Lone Star ticks [Amblyomma americanum] per treated animal). Fecal samples were collected at approximately 0700 h on d -7, 0, 7,10,14,17, and 21 relative to tick infestation. Fecal constituents measured were: DM, OM, pH, Lactobacillus spp., Escherchia coli, acetate, propionate, butyrate, isobutyrate, valerate, isovalerate, immunoglobulin A (IgA), and cortisol. Experimental d affected (P < 0.05). all constituents measured. Plane of nutrition affected (P < 0.05) DM, OM, VFAs, and IgA. Tick treatment numerically (P = 0.13) reduced cortisol. A multivariate stepwise selection model containing cortisol andE. Coli values on d 10 and d 14 accounted for 33% of the variation in daily adult female tick feeding counts across both planes of nutrition (P < 0.07). Within the moderate plane of nutrition, a model containing only cortisol on d 10 and d 14 described 59 % of the variation in the number of feeding ticks (P < 0.02). Similarly, a model including cortisol, propionate, isovalerate, and DM at d 10 and d 14 d described 95% of the variation in total feeding ticks in the low plane of nutrition. Of the constituents measured, fecal cortisol offers the best possibility of non-invasively assessing stress by way of a single assay but the presence of ticks would still need to be confirmed visually. Although several constituents measured in this study should exist in sufficient quantity to directly affect near infrared spectra, none stood out as a clear descriptor of prior observed differences in fecal spectra between tick-treated versus non tick-treated animals. There were, however, groups of fecal constituents related to daily adult female tick feeding numbers (as a visual estimation of tick stress).
Journal of Animal Science 05/2013; · 2.10 Impact Factor
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ABSTRACT: Ticks are external parasites, which pose a significant economic burden to domestic animal agriculture. The effects of ticks on grazing animals may be exacerbated during periods of low nutrition, such as those encountered during drought. It is not completely understood how plane of nutrition and tick burden interact to affect metabolism in cattle. The objective of the current research was to examine the plane of nutrition by tick-burden interaction in cattle and determine the effects of this interaction on physiological indicators of growth and metabolism. Eight-month-old Angus cross steers (n = 28, 194 ± 3.0 kg) were stratified by pretrial BW and DMI into 1 of 4 groups (n = 7/group) in a 2 × 2 factorial arrangement. Categories were: moderate (14.0 ± 1.0% CP, 60 ± 1.5% TDN) vs. low (9.0 ± 1.0% CP, 58 ± 1.5% TDN) plane of nutrition and control (no tick) vs. tick treatment (300 pair of adult Amblyomma americanum per treated animal). Steers were individually fed their respective experimental diets ad libitum and feed intake was monitored for 35 d before and 21 d after the start of tick infestation (d 0). Blood samples were harvested via coccygeal venipuncture on d -7, 0, 7, 8, 9, 10, 11, 13, 17, and 21. Plasma cortisol and IGF-I were determined by RIA. Metabolic indicators were determined by colorimetric assay. Steers weighed 195 ± 6 kg on d -35, but on d -7 and d 21, the moderate steers weighed more than the low steers (244.1 ± 8.7 vs. 227.7 ± 8.4 kg, P < 0.07; and 283.4 ± 8.0 vs. 244.0 ± 7.9 kg, P < 0.001, respectively). Cortisol was affected by plane of nutrition and treatment (P < 0.08). Insulin-like growth factor-I was greater (P < 0.01) in moderate than in low and control animals (P < 0.02), compared with tick-treated animals. Tick treatment had no effect (P > 0.05) on any of the metabolites measured in this study. Plane of nutrition affected (P < 0.02) albumin, blood urea nitrogen, and glucose in that values from the moderate group animals were greater than those from the low group. Although cortisol was related to both tick treatment and nutritional status in the current study, with respect to the combination of parasitism and suboptimal nutrition, IGF-I was the most highly indicative constituent measured. Tick burden affected various characteristics of growth and metabolism in these growing cattle and the effects were exacerbated by a low plane of nutrition.
Journal of Animal Science 06/2012; 90(10):3442-50. · 2.10 Impact Factor
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ABSTRACT: A meta-analysis was conducted to examine phenotypic relationships between feed efficiency, scrotal circumference and semen-quality traits in yearling bulls. Data evaluated were obtained from 5 postweaning trials involving Angus (N = 92), Bonsmara (N = 62), and Santa Gertrudis (N = 50) bulls fed diets that ranged from 1.70 to 2.85 Mcal ME/kg DM. Following an adaptation period of 24 to 28 d, feed intake was measured daily and BW measured at 7 or 14-d intervals during the 70-77 d trials. Ultrasound carcass traits (12(th) rib backfat thickness, BF; longissimus muscle area, LMA) and scrotal circumference (SC) were measured at the start and end of each trial. Semen samples were collected by electroejaculation within 51 d of the end of the trials when age of bulls averaged from 365 to 444 d, and were evaluated for progressive sperm motility and morphology. Residual feed intake (RFI) was calculated as the difference between actual dry matter intake (DMI) and expected DMI from linear regression of DMI on ADG and mid-test BW(0.75); with trial, trial by ADG, and trial by mid-test BW(0.75) as random effects. Across all studies, bulls with low RFI phenotypes (<0.5 SD below the mean RFI of 0) consumed 20% less DMI and had 10% less BF, but had similar ADG, SC and semen-quality traits compared to high-RFI bulls (> 0.5 SD above the mean RFI of 0). Gain to feed ratio (G:F) was strongly correlated with ADG (0.60) and weakly correlated with initial BW (-0.17) and DMI (-0.26). Residual feed intake was not correlated with ADG, initial age or BW, but was correlated with DMI (0.71), G:F (-0.70) and BF (0.20). Initial SC (-0.20), gain in SC (-0.28), and percent normal sperm (-0.17) were correlated with G:F, but only sperm morphology was found to be weakly associated with RFI (0.13). These data suggest that RFI is not phenotypically associated with SC or sperm motility, but weakly associated with sperm morphology.
Journal of Animal Science 06/2012; · 2.10 Impact Factor
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ABSTRACT: Meals are clusters of feedbunk visit (BV) events that are differentiated from the next meal by a nonfeeding interval that is longer compared with the nonfeeding intervals within a meal. The longest nonfeeding interval considered to be part of a meal is defined as the meal criterion. The objective of this study was to determine which combination of 2 probability density functions [(PDF): Gaussian normal (G), Weibull (W), Log-Normal, Gamma, and Gumbel] used in a bimodal distribution model had the best fit of nonfeeding interval data collected in beef heifers. Feeding behavior traits (572,627 total BV events) were measured in 119 heifers fed a high-grain diet (3.08 Mcal ME/kg DM), using a GrowSafe system for 66 d. The frequency and duration of BV events averaged 75 ± 15 events/d and 73.0 ± 22.3 min/d, respectively. The bimodal PDF combinations were fitted to the log(10)-transformed interval lengths between BV events for each animal, using R mixdist package (2.13). The Akaike Information Criterion (AIC) was used to assess goodness of fit of the 25 bimodal PDF combinations. The PDF model with the least AIC value was selected as the best fit for each individual. A χ(2) analysis of the selected best PDF distribution across individuals revealed that 78.2% of the heifers best fit were G-W or W-W PDF models. The likelihood probability estimates were calculated from the average AIC deviation of each model from the standard G-G model. The G-W likelihood probability estimate was greater (P = 0.001) than the W-W combination (0.997 vs. 0.727). Our analysis indicated the G-W model had a statistically better fit and is most likely the best approach to define meal criterion in beef heifers fed high-grain diets.
Journal of Animal Science 03/2012; 90(8):2750-3. · 2.10 Impact Factor
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ABSTRACT: The objective of this study was to evaluate the use of an electronic radio-frequency-identification-based system (GrowSafe System Ltd., Airdrie, Alberta, Canada) to measure feeding behavior traits in beef cattle fed a high-grain diet. Feeding behavior data were recorded by the GrowSafe system and time-lapse video using 10 heifers over a 6-d period. Observed bunk visit (BV) and meal event data (frequency and duration) were compared with electronic feeding behavior data generated by the GrowSafe system at 5 parameter settings (MPS; 30, 60, 100, 150, and 300 s), which are used to define the maximum duration between consecutive electronic identification recordings to initiate a subsequent BV event. A random coefficient model was used to compare video and electronic data using orthogonal contrasts. Video data were regressed on the electronic feeding behavior data to obtain an estimate of precision (r(2)) and other statistical estimates, including mean square error of prediction and concordance correlation coefficient, to access the adequacy of the electronic system predictions. The variation in MPS values affected BV data, but not meal event data. Electronic meal frequency and duration data were not different (P > 0.50) from observed values, and were not affected by electronic MPS values. The optimal MPS value for prediction of BV and meal event frequency and duration traits was 100 s. Our evaluation indicated the GrowSafe system 4000E was able to predict BV and meal event data when the 100-s MPS was used to analyze the feeding behavior data.
Journal of Animal Science 04/2011; 89(9):2904-10. · 2.10 Impact Factor
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ABSTRACT: We examined the response of selected animal performance, endocrine, immune, and metabolic factors from 13 steers (254+/-6.1 kg) with and without a lone star (Amblyomma americanum) tick burden during progressive days of the tick feeding cycle. Steers were randomly assigned to either non-treated controls or treated with 300 adult pair of A. americanum per animal. Animals were weighed and blood sampled on days -7, 0, 10, 14, 21, 28, and 35 relative to tick treatment. Tick treatment did not affect (P<0.1) animal performance. Experimental day did (P<0.05) affect body weight gain and dry matter intake. Tick treatment did not affect (P<0.1) metabolic indicators. Experimental day affected (P<0.05) IGF1 and lactate, tended to affect cortisol (P<0.07), but did not affect (P<0.1) glucose concentrations. Tick treatment did not significantly (P<0.1) affect growth hormone receptor (GHR) mRNA in liver, but liver tissue from treated animals had numerically lower GHR mRNA than did tissue from control animals. Day had a significant (P<0.05) effect on liver GHR mRNA. There was a significant treatment by day interaction (P<0.05) for liver IGF1 gene expression, as IGF1 mRNA was reduced in tick-treated cattle versus control cattle on day 35. Overall, liver IGF1 gene expression was lower (P<0.05) in tick than in control animals while there was no effect (P>0.1) due to day. Within the tick-treated group, correlations were found between quantitative female tick feeding characteristics and host metabolic indicators. Feeding by adult female lone star ticks did cause acute stress in growing beef steers on a moderate plane of nutrition as indicated by some physiologic indicators. In particular there may be longer term effects on the somatotrophic axis in the liver which could affect subsequent (i.e. feedlot) performance. It is not known how these observed effects would be manifest under a lower plane of nutrition, as is common and may become more so within the current native range of A. americanum. Other acute effects due to tick feeding may have been masked by the effects of handling and invasive sampling. Non-invasive experimental procedures are called for in order to study the effects of a stressor such as arthropod infestation on grazing animals. Future research efforts will be aimed at non-invasively elucidating the effects of tick stress on grazing animals under various nutritional environments.
Veterinary Parasitology 10/2010; 173(1-2):99-106. · 2.58 Impact Factor
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ABSTRACT: The objective of this study was to characterize residual feed intake (RFI) and to estimate phenotypic and genetic correlations with performance and ultrasound carcass traits in growing heifers. Four postweaning feed efficiency trials were conducted using 468 Brangus heifers. The complete Brangus pedigree file from Camp Cooley Ranch (Franklin, TX), which included 31,215 animals, was used to generate genetic parameter estimates. The heifer progeny from 223 dams were sired by 36 bulls, whereas the complete pedigree file contained 1,710 sires and 8,191 dams. Heifers were individually fed a roughage-based diet (ME = 1.98 Mcal/kg of DM) using Calan gate feeders for 70 d. Heifer BW was recorded weekly and ultrasound measures of 12th- to 13th-rib fat thickness (BF) and LM area (LMA) obtained at d 0 and 70. Residual feed intake (RFIp) was computed as actual minus predicted DMI, with predicted DMI determined by linear regression of DMI on mid-test BW(0.75) (MBW) and ADG with trial, trial x MBW, and trial x ADG as random effects. Overall means for ADG, DMI, and RFI were 1.01 (SD = 0.15), 9.51 (SD = 1.02), and 0.00 (SD = 0.71) kg/d, respectively. Stepwise regression analysis revealed that inclusion of gain in BF and final LMA into the base model increased the R(2) (0.578 vs. 0.534) and accounted for 9% of the variation in DMI not explained by MBW and ADG (RFIp). Residual feed intake and carcass-adjusted RFI (RFIc) were strongly correlated phenotypically and genetically with DMI and FCR, but not with ADG or MBW. Gain in BF was phenotypically correlated (P < 0.05) with RFIp (0.22), but not with FCR or RFIc; however, final BF was genetically correlated (P < 0.05) with RFIp (0.36) and RFIc (0.39). Gain in LMA was weakly phenotypically correlated with FCR, but not with RFIp or RFIc; however, gain in LMA was strongly genetically correlated with RFIp (0.55) and RFIc (0.77). The Spearman rank correlation between RFIp and RFIc was high (0.96). These results suggest that adjusting RFI for ultrasound carcass composition traits will facilitate selection phenotypically independent of growth, body size, and carcass composition; however, genetic relationships may still exist between RFI and carcass composition.
Journal of Animal Science 08/2009; 87(12):3887-96. · 2.10 Impact Factor
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ABSTRACT: Residual feed intake (RFI) is a measure of feed efficiency defined as the difference between actual feed intake and expected feed intake required for maintenance and production. The objective of this study was to determine the relationship between RFI, feeding behavior, and other performance traits in growing heifers. Individual DMI was measured in Brangus heifers (n = 115) fed a roughage-based diet (ME = 2.0 Mcal/kg) for 70 d using Calan-gate feeders. Residual feed intake was computed as the residuals from linear regression of DMI on mid-test BW(0.75) and ADG. Heifers with the greatest (least efficient, n = 18) and least (most efficient, n = 18) RFI were identified for quantification of feeding behavior traits. Continuous video recordings were obtained for all heifers during d 28 through d 56 of the 70-d feeding trial. Video data of 2 replications of four 24-h periods, 2 wk apart, were analyzed for the focal heifers. A head-down feeding event was defined as a heifer positioned in the feeder with her head lowered. A meal included all head-down feeding events that were separated by less than 300 s. The mean RFI for the high- and low-RFI heifers were 1.00 and -1.03 +/- 0.03 kg/d, respectively. High-RFI heifers consumed 21.9% more (P < 0.0001) DM but had similar BW and ADG compared with low-RFI heifers. The high-RFI heifers spent less time in head-down feeding events per day (P < 0.0001; 124 vs. 152 +/- 4.3 min/d), consumed DM at a faster rate (99.6 vs. 62.8 +/- 3.3 g/min), and ate more often per day (119.1 vs. 90.5 +/- 3.9 head-down feeding events/d) compared with the low-RFI heifers; however, meal duration and frequency were not related to RFI. We conclude that feeding behavior related to head-down feeding events may be more useful as an indicator of RFI than the number of meal events.
Journal of Animal Science 04/2009; 87(8):2685-9. · 2.10 Impact Factor
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S M Behrends,
R K Miller,
F M Rouquette,
R D Randel,
B G Warrington,
T D A Forbes,
T H Welsh,
H Lippke,
J M Behrends, G E Carstens,
J W Holloway
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ABSTRACT: Relationships of temperament evaluated at different production stages with growth, carcass characteristics and beef tenderness were determined in Bonsmara crossbred steers managed under commercial managent. Temperament was evaluated at weaning and at initiation of the finishing phase. Steers from a Roswell, NM ranch (n=156) and a Cline, TX ranch (n=21) were stratified at fall weaning by weight and source and randomly allotted to winter ryegrass at Uvalde or Overton, TX followed by feeding in a commercial feedlot near Batesville, TX. Cattle were observed for temperament (escape velocity, EV, m/s; pen and chute temperament score, PTS and CTS) at weaning and upon entry to the feedlot. Cattle were harvested at approximately 7 mm 12th rib fat. Carcass data was taken approximately 36 hrs post-mortem and 2.5cm thick steaks were removed from the 13th rib for Warner-Bratzler shear force (WBS) determination. The only measures of temperament significantly related to performance were EV and PTS. Weaning EV appeared to be more related to feedlot ADG (r=-0.26, P<0.003), ribeye area (r=-0.37, P<0.0008), yield grade (r=0.29, P<0.01) and WBS, r=0.27, P<0.005) than did the later measures of temperament. However, in-feedlot EV was associated with feedlot weights (r=-0.28, P<0.0004). Results of this research suggest temperament, particularly at weaning, is related to feedlot performance, carcass merit, and beef tenderness at a low to moderate level and evaluation of this trait may be a helpful management tool.
Meat Science 03/2009; 81(3):433-8. · 2.28 Impact Factor
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ABSTRACT: The objectives of this study were to characterize feed efficiency traits and to examine phenotypic correlations between performance and feeding behavior traits, and ultrasound measurements of carcass composition in growing bulls. Individual DMI and feeding behavior traits were measured in Angus bulls (n=341; initial BW=371.1+/-50.8 kg) fed a corn silage-based diet (ME=2.77 Mcal/kg of DM) for 84 d in trials 1 and 2 and for 70 d in trials 3 and 4 by using a GrowSafe feeding system. Meal duration (min/d) and meal frequency (events/d) were calculated for each bull from feeding behavior recorded by the GrowSafe system. Ultrasound measures of carcass 12th-rib fat thickness (BF) and LM area (LMA) were obtained at the start and end of each trial. Residual feed intake (RFIp) was computed from the linear regression of DMI on ADG and midtest BW(0.75) (metabolic BW, MBW), with trial, trial by ADG, and trial by midtest BW(0.75) as random effects (base model). Overall ADG, DMI, and RFIp were 1.44 (SD=0.29), 9.46 (SD=1.31), and 0.00 (SD=0.78) kg/d, respectively. Stepwise regression analysis revealed that inclusion of BW gain in BF and LMA in the base model increased R(2) (0.76 vs. 0.78) and accounted for 9% of the variation in DMI not explained by MBW and ADG (RFIp). Residual feed intake and carcass-adjusted residual feed intake (RFIc) were moderately correlated with DMI (0.60 and 0.55, respectively) and feed conversion ratio (FCR; 0.49 and 0.45, respectively), and strongly correlated with partial efficiency of growth (PEG; -0.84 and -0.78, respectively), but not with ADG or MBW. Gain in BF was weakly correlated with RFIp (0.30), FCR (-0.15), and PEG (-0.11), but not with RFIc. Gain in LMA was weakly correlated with RFIp (0.17) and FCR (-0.19), but not with PEG or RFIc. The Spearman rank correlation between RFIp and RFIc was high (0.91). Meal duration (0.41), head-down duration (0.38), and meal frequency (0.26) were correlated with RFIp and accounted for 35% of the variation in DMI not explained by MBW, ADG, and ultrasound traits (RFIc). These results suggest that adjusting residual feed intake for carcass composition will facilitate selection to reduce feed intake in cattle without affecting rate or composition of gain.
Journal of Animal Science 12/2008; 87(4):1528-39. · 2.10 Impact Factor
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ABSTRACT: As grain prices have increased dramatically in the past year, understanding the fundamental genetic, cellular, and biochemical mechanisms responsible for feed efficiency (FE; g of gain/g of feed) or residual feed intake (RFI; an alternative feed efficiency trait that quantifies interanimal variation in DMI that is unexplained by differences in BW and growth rate) in livestock and poultry is extremely important with respect to maintaining viable meat production practices in the United States. Although breed and diet have long been known to affect mitochondrial function, few studies have investigated differences in mitochondrial function and biochemistry due to interanimal phenotypic differences in FE or RFI (i.e., variation among animals of the same breed and fed the same diet). This paper reviews existing literature on relationships of mitochondrial function and biochemistry with FE and RFI in poultry and livestock. The overall goal of all of this paper is to assist the development of tools (e.g., genetic markers or biomarkers) to aid commercial breeding companies in genetic selection that, in turn, will help maintain viable livestock and poultry industries in the United States and around the world.
Journal of Animal Science 12/2008; 87(14 Suppl):E48-63. · 2.10 Impact Factor
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ABSTRACT: Angus bulls and heifers from lines divergently selected for serum IGF-I concentration were used to evaluate the effects of IGF-I selection line on growth performance and feed efficiency in 2 studies. In study 1, bulls (low line, n = 9; high line, n = 8; initial BW = 367.1 +/- 22.9 kg) and heifers (low line, n = 9; high line, n = 13; initial BW = 286.4 +/- 28.6 kg) were adapted to a roughage-based diet (ME = 1.95 Mcal/kg of DM) for 24 d and fed individually for 77 d by using Calan gate feeders. In study 2, bulls (low line, n = 15; high line, n = 12; initial BW = 297.5 +/- 34.4 kg) and heifers (low line, n = 9; high line, n = 20; initial BW = 256.0 +/- 25.1 kg) were adapted to a grain-based diet (ME = 2.85 Mcal/kg of DM) for 32 d and fed individually for 70 d by using Calan gate feeders. Blood samples were collected at weaning and at the start and end of each study, and serum IGF-I concentration was determined. Residual feed intake (RFI) was calculated, within study, as the residual from the linear regression of DMI on midtest BW(0.75), ADG, sex, sex by midtest BW(0.75) and sex by ADG. In study 1, calves from the low IGF-I selection line had similar initial and final BW and ADG, compared with calves from the high IGF-I selection line. In addition, DMI and feed conversion ratio were similar between IGF-I selection lines; however, calves from the low IGF-I selection line tended (P < 0.10) to have lesser RFI than calves from the high IGF-I selection line (-0.26 vs. 0.24 +/- 0.31 kg/d). In study 2, IGF-I selection line had no influence on performance or feed efficiency traits. However, there was a tendency (P = 0.15) for an IGF-I selection line x sex interaction for RFI. Bulls from the low IGF-I selection line had numerically lesser RFI than those from the high IGF-I selection line, whereas in heifers, the IGF-I selection line had no effect on RFI. In studies 1 and 2, weaning and initial IGF-I concentrations were not correlated with either feed conversion ratio or RFI. However, regression analysis revealed a sex x IGF-I concentration interaction for initial IGF-I concentration in study 1 and weaning IGF-I concentration in study 2 such that the regression coefficient was positive for bulls and negative for heifers. These data suggest that genetic selection for postweaning serum IGF-I concentration had a minimal effect on RFI in beef cattle.
Journal of Animal Science 08/2008; 86(11):2862-71. · 2.10 Impact Factor
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ABSTRACT: The objectives of this study were to describe a system to assess KPH fat by using real-time ultrasound (RTU) and to develop equations to predict total physical separable internal fat (IFAT) based on ultrasound measurements. Data for this study were obtained from 24 Angus steers fed either hay- or corn-based diets during the backgrounding phase. Steers were serially slaughtered in 3 groups: at weaning (baseline), then at 4 and 8 mo after weaning. A fourth group was composed of 4 steers from the hay-fed group that were slaughtered at approximately 10 mo after weaning. The RTU measurements were collected every 2 mo, with a preslaughter scan approximately 7 d before the slaughter time. The RTU measurements consisted of 12th- to 13th-rib backfat thickness, 12th to 13th ribeye area, percentage of intramuscular fat, and kidney fat depth, which was measured in a cross-sectional image collected between the first lumbar vertebra and the 13th rib. For kidney fat, the ultrasound probe was placed on the flank region approximately 15 cm from the midline of the animal. Images were stored in the ultrasound console, and measurements were taken between the ventral part of the iliocostalis muscle and the end of the KPH fat at the chute side. The relationship between carcass and ultrasound measurements in the depths of kidney fat (cKFd and uKFd, respectively) had an r(2) of 0.93, with a root mean square error (RMSE) of 1.14 cm. An allometric regression between carcass KPH weight (cKPHwt) and cKFd was identified, and the untransformed regression had an r(2) of 0.96. The linear regression between total IFAT and cKPHwt had an r(2) of 0.97, with an RMSE of 2.67 kg. Therefore, a system was developed to predict IFAT from uKFd measurements by combining these equations. Additionally, a single linear regression between IFAT and uKFd measurements was developed (r(2) = 0.89, RMSE = 5.32 kg). Even though the system of equations had a lower RMSE of prediction and greater r(2) compared with the single linear regression (4.80 vs. 5.10 kg and 0.91 vs. 0.89, respectively), there was no difference between these methods in predicting IFAT (P = 0.4936) by using a pairwise mean square error of prediction analysis. Our results indicated that uKFd measurements can accurately and precisely predict the cKFd of steers consuming either high concentrate or forage rations. The results also showed that cKFd is highly correlated with cKPHwt, which can be used to estimate total IFAT. More research is needed to further evaluate this technique with different feeding strategies, breeds, and sexes.
Journal of Animal Science 04/2008; 86(3):763-7. · 2.10 Impact Factor
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ABSTRACT: A comparative slaughter trial was conducted with 36 F1 Nellore x Red Angus calves (12 steers, 12 bulls, and 12 heifers), averaging 274 kg of BW, to assess the net requirements of protein and energy for growth and maintenance. Three cattle from each group (i.e., steers, bulls, and heifers) were slaughtered at the beginning of the trial to determine the initial body composition. The remaining calves were randomly assigned to 1 of 3 treatments: maintenance (diet containing 70% of DM as corn silage fed at 1.2% of BW daily) or concentrate at 0.75 or 1.5% of BW daily with corn silage available for ad libitum consumption. The diets were isonitrogenous (2% N, DM basis). The experimental design provided ranges in ME intake, BW, and ADG for the development of regression equations to predict the maintenance requirements for NE and net protein (MRNE and MRNP, respectively) and the growth requirement for NE and net protein (GRNE and GRNP, respectively). After 84 d of growth, the cattle were slaughtered. The cleaned gastrointestinal tracts, organs, carcasses, heads, hides, tails, feet, blood, and tissues were weighed to measure empty BW (EBW). These parts were ground separately and subsampled for chemical analyses. For each animal within a period, DMI was measured daily and samples of feces were collected to determine diet digestibility. There were no differences in MRNE (P = 0.06) among groups. The combined data indicated a MRNE of 71.2 kcal x kg(-0.75) of EBW x d(-1), with a partial efficiency of use of ME to NE(m) of 0.71. The partial efficiency of use of ME to NE for growth was 0.54 for bulls, 0.47 for steers, and 0.54 for heifers. The GRNE for steers and heifers were similar (P = 0.15) but were 18.7% greater (P = 0.03) for steers and heifers than for bulls. The MRNP did not differ among groups and averaged 2.53 g of CP x kg(-0.75) of EBW x d(-1). Likewise, GRNP was not different among groups. The percentage of retained energy deposited as protein (RE(p)) increased as the content of retained energy in the gain (RE(c), Mcal/kg of empty body gain) decreased. The RE(p) equation of the pooled data was 46.5 x e(-0.2463 x RE(c)). We conclude that the energy requirement of crossbred Bos indicus x Bos taurus for maintenance might be less than that of purebred Bos taurus and that RE(p) is nonlinearly, negatively correlated with RE(c). The GRNE was less for bulls than for steers and heifers. However, we found no differences in MRNE, MRNP, and GRNP for bulls, steers, and heifers of Nellore x Red Angus crossbreds.
Journal of Animal Science 09/2007; 85(8):1971-81. · 2.10 Impact Factor
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ABSTRACT: Meat production by goats has become an important livestock enterprise in several parts of the world. Nonetheless, energy and protein requirements of meat goats have not been defined thoroughly. The objective of this study was to determine the energy and protein requirements for maintenance and growth of 34 (3/4) Boer x (1/4) Saanen crossbred, intact male kids (20.5 +/- 0.24 kg of initial BW). The baseline group was 7 randomly selected kids, averaging 21.2 +/- 0.36 kg of BW. An intermediate group consisted of 6 randomly selected kids, fed for ad libitum intake, that were slaughtered when they reached an average BW of 28.2 +/- 0.39 kg. The remaining kids (n = 21) were allocated randomly on d 0 to 3 levels of DMI (treatments were ad libitum or restricted to 70 or 40% of the ad libitum intake) within 7 slaughter groups. A slaughter group contained 1 kid from each treatment, and kids were slaughtered when the ad libitum treatment kid reached 35 kg of BW. Individual body components (head plus feet, hide, internal organs plus blood, and carcass) were weighed, ground, mixed, and subsampled for chemical analyses. Initial body composition was determined using equations developed from the composition of the baseline kids. The calculated daily maintenance requirement for NE was 77.3 +/- 1.05 kcal/kg(0.75) of empty BW (EBW) or 67.4 +/- 1.04 kcal/kg(0.75) of shrunk BW. The daily ME requirement for maintenance (118.1 kcal/kg(0.75) of EBW or 103.0 kcal/kg(0.75) of shrunk BW) was calculated by iteration, assuming that the heat produced was equal to the ME intake at maintenance. The partial efficiency of use of ME for NE below maintenance was 0.65. A value of 2.44 +/- 0.4 g of net protein/kg(0.75) of EBW for daily maintenance was determined. Net energy requirements for growth ranged from 2.55 to 3.0 Mcal/kg of EBW gain at 20 and 35 kg of BW, and net protein requirements for growth ranged from 178.8 to 185.2 g/kg of EBW gain. These results suggest that NE and net protein requirements for growing meat goats exceed the requirements previously published for dairy goats. Moreover, results from this study suggest that the N requirement for maintenance for growing goats is greater than the established recommendations.
Journal of Animal Science 05/2007; 85(4):1014-23. · 2.10 Impact Factor
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ABSTRACT: Anti-tick treatments are often applied concurrent to routine livestock management practices with little regard to actual infestation levels. Prescription treatments against ticks on grazing cattle would be facilitated by non-invasive detection methods. One such method is fecal near infrared spectroscopy (NIRS). Four studies utilizing cattle (Bos spp.) and one with horses (Equus caballus) fed varying diets and infested with either Amblyomma americanum, A. maculatum, A. cajennense or Dermacentor albipictus were conducted to determine the ability of fecal NIRS to identify samples from animals with (High stress) and without (Low stress) a tick burden. Discriminant analysis of each individual trial resulted in R(2)>0.80. Similar analyses utilizing all combinations of four studies, predicting group membership in the remaining study, yielded R(2)>0.80, but correct determinations for Low and High tick stress samples of only 53.4 and 60.1%, respectively. All five trials were combined and a random 10 or 25% of the samples were removed from the calibration. As in the previous calibrations, a high degree of discrimination was achieved (R(2)>0.89). The validation samples were correctly identified at 91.7% for Low stress and 96.3% for High stress, respectively. Difficulties in detecting differences in fecal samples due to confounding effects of trial were overcome by combining calibration sets. Overall, differences in fecal NIR spectra apparently due to tick stress were accurately detected across diet, host species, and tick species.
Veterinary Parasitology 03/2007; 144(1-2):146-52. · 2.58 Impact Factor
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ABSTRACT: Effects of 2-nitro-1-propanol, 2-nitroethanol, nitroethane, and 2-nitro-methyl-propionate (0, 10, and 20 mM) on growth of Campylobacter jejuni were tested during culture in Bolton broth adjusted to pH 5.6, 7.0, or 8.2. The nitrocompounds were similarly tested against C. coli but at pH 8.2 only. Viable cell counts measured during incubation revealed main effects (P < 0.05) of all nitrocompounds on the survivability of C. jejuni. An effect of pH (P < 0.05) on the survivability of C. Jejuni during incubation with nitrocompounds was observed, with greater inhibition observed at pH 8.2 than at pH 5.6 or 7.0 for nitroethane, 2-nitro-l-propanol, and 2-nitroethanol, but not for 2-nitro-methyl-propionate, which showed greatest inhibition at pH 5.6. Except for 2-nitro-methyl-propionate, which was ineffective, all nitrocompounds elicited similar effects on C. coli. The effect of nitroethane and 2-nitro-l-propanol (10 mM) on naturally occurring Campylobacter was investigated during incubation of porcine fecal suspensions, where Campylobacter concentrations decreased more rapidly (P < 0.05) in suspensions with added 2-nitro-l-propanol than in unsupplemented or nitroethane-supplemented suspensions, thus reiterating the superior inhibitory effect of 2-nitro-l-propanol.
Journal of Food Science 03/2007; 72(2):M50-5. · 1.66 Impact Factor
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ABSTRACT: Effects of 2-nitro-1-propanol, 2-nitroethanol, nitroethane, and 2-nitro-methyl-propionate (0, 10, and 20 mM) on growth of Campylobacter jejuni were tested during culture in Bolton broth adjusted to pH 5.6, 7.0, or 8.2. The nitrocompounds were similarly tested against C. coli but at pH 8.2 only. Viable cell counts measured during incubation revealed main effects (P < 0.05) of all nitrocompounds on the survivability of C. jejuni. An effect of pH (P < 0.05) on the survivability of C. Jejuni during incubation with nitrocompounds was observed, with greater inhibition observed at pH 8.2 than at pH 5.6 or 7.0 for nitroethane, 2-nitro-l-propanol, and 2-nitroethanol, but not for 2-nitro-methyl-propionate, which showed greatest inhibition at pH 5.6. Except for 2-nitro-methyl-propionate, which was ineffective, all nitrocompounds elicited similar effects on C. coli. The effect of nitroethane and 2-nitro-l-propanol (10 mM) on naturally occurring Campylobacter was investigated during incubation of porcine fecal suspensions, where Campylobacter concentrations decreased more rapidly (P < 0.05) in suspensions with added 2-nitro-l-propanol than in unsupplemented or nitroethane-supplemented suspensions, thus reiterating the superior inhibitory effect of 2-nitro-l-propanol.
Journal of Food Science 02/2007; 72(2):M50 - M55. · 1.66 Impact Factor
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ABSTRACT: Strategies are sought to reduce economic and environmental costs associated with ruminant methane emissions. The effect of oral nitroethane or 2-nitropropanol administration on ruminal methane-producing activity and volatile fatty acid production was evaluated in mature ewes. Daily administration of 24 and 72 mg nitroethane/kg body weight reduced (P<0.05) methane-producing activity by as much as 45% and 69% respectively, when compared to control animals given no nitroethane. A daily dose of 120 mg 2-nitropropanol/kg body weight was needed to reduce (P<0.05) methane-producing activity by 37% from that of untreated control animals. Reductions in methane-producing activity may have been diminished by the last day (day 5) of treatment, presumably due to ruminal adaptation. Oral administration of nitroethane or 2-nitropropanol had little or no effect on accumulations or molar proportions of volatile fatty acids in ruminal contents collected from the sheep. These results demonstrate that nitroethane was superior to 2-nitropropanol as a methane inhibitor and that both nitrocompounds reduced ruminal methanogenesis in vivo without redirecting the flow of reductant generated during fermentation to propionate and butyrate.
Bioresource Technology 12/2006; 97(18):2421-6. · 4.98 Impact Factor
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ABSTRACT: The major objective of this experiment was to determine whether the bovine placenta could be stimulated to secrete progesterone, since the bovine placenta secretes little progesterone when the corpus luteum is functional. Secondly, we wanted to determine whether reported abortifacients or progesterone or estrogen receptor antagonists affected bovine placental prostaglandin secretion. The ovine placenta secretes half of the circulating progesterone at day 90 of pregnancy and PGE2 appears to regulate ovine placental progesterone secretion. Calcium has been reported to regulate placental progesterone secretion in cattle. Diced 186-245-day placental slice explants from six Brahman and six Angus cows were incubated in vitro at 39.5 degrees C under 95% air: 5% CO2 at pH 7.2 in 5 ml of M-199 for 1 h in the absence of treatments and for 4 and 8 h in the presence of treatments. Treatments were: vehicle; R24571; compound 48/80; IP3; PGE2; CaCl2; cyclosporin A; lipopolysaccharide (endotoxin) from Salmonella abortus equi., enteriditis, and typhimurium; monensin; ionomycin; arachidonic acid; mimosine; palmitic acid; progesterone, androstenedione; estradiol-17beta; A23187; RU-486; or MER-25. Jugular and uterine venous plasma and culture media were analyzed for progesterone, PGE2 and PGF2alpha by radioimmunoassay (RIA). Plasma hormone data were analyzed by a One-Way Analysis of Variance (ANOVA). Hormone data in culture media were analyzed for breed and treatment effects by a Factorial Design (2 breeds, 2-range of days, 21 treatments) for ANOVA (2 x 2 x 21). Since hormone data secreted by placental tissue in vitro did not differ (P > or = 0.05) by breed or range of days of pregnancy, data were pooled and analyzed by a One-Way ANOVA. Concentrations of PGE2 in uterine venous blood were two-fold greater (P < or = 0.05) in Angus than Brahman cows. PGE2 and PGF2alpha in vehicle controls increased from 4 to 8h (P < or = 0.05), but not progesterone (P > or = 0.05) Progesterone in culture media treated with RU-486 increased (P < or = 0.05) at 4 and 8 h compared to vehicle controls and was not affected by other treatments (P > or = 0.05). Concentrations of PGE2 in media at 4 and 8 h were lower (P < or = 0.05) when compared to controls except treatment with PGE2 at 4 and 8h and RU-486 at 8h (P > or = 0.05). PGF2alpha was increased (P < or = 0.05) by RU-486 at 8h and no other treatment affected PGF2alpha at 4 or 8 h (P < or = 0.05). In conclusion, modulators of cellular calcium signalling pathways given alone do not affect bovine placental progesterone secretion at the days studied and progesterone receptor-mediated events appear to suppress placental progesterone, PGF2alpha, and PGE2 secretion in cattle. In addition, PGE2 does not appear to regulate bovine placental progesterone secretion when the corpus luteum is functional and bacterial endotoxin does not appear to affect bovine placental secretion of PGF2alpha or PGE2.
Prostaglandins & other lipid mediators 05/2004; 73(3-4):265-78. · 2.70 Impact Factor
