Using ammonium sulfate, three levels of dietary S (.15, .20, and .25%, DM basis) were evaluated in a finishing trial with 108 yearling crossbred heifers (384 kg). The basal diet contained (DM basis) 4% alfalfa hay, 6% sudangrass hay, 74% steam-flaked corn, 4% yellow grease, 6% cane molasses, and 6% protein-mineral supplement. Increasing dietary S decreased ADG (quadratic effect, P < .10), DMI (linear effect, P < .10), feed efficiency (quadratic effect, P < .10), diet NE (quadratic effect, P < .10), and longissimus muscle area (linear effect, P < .05). Six Holstein steers (218 kg) with cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on characteristics of digestion. Treatment effects on ruminal and total tract digestion of OM and N were small (P > .10). However, ruminal digestion of ADF and starch was slightly lower (quadratic effect, P < .10), and postruminal digestion of ADF and starch was correspondingly greater (quadratic effect, P < .05) with supplemental S. Dietary S level did not influence (P > .10) ruminal synthesis of microbial N. Increasing dietary S did not influence (P > .10) ruminal pH or lactic acid. Increasing S decreased molar proportions of acetate (quadratic effect, P < .10) and increased molar proportions of propionate (linear effect, P < .10). We conclude that S in excess of .20% of dietary DM may have detrimental effects on growth performance and dietary NE. Excessive dietary S may also compromise carcass merit by decreasing longissimus muscle area.

No abstract

Crossbred yearling steers (n = 125; 372 kg) were used in a 109-d finishing trial. Steers were fed an 88% concentrate diet containing 65% corn (DM basis) as 1) dry rolled corn (DRC); 2) tempered rolled corn (TRC), 43 mg surfactant (SarTemp)/kg corn; 3) TRC, 172 mg surfactant/kg corn; 4) TRC, 430 mg surfactant/kg corn; and 5) steam-flaked corn (SFC). Corn moisture was greater (3.5%, P < .01) for TRC than for DRC but less (10%, P < .05) than for SFC. Starch enzymatic reactivity was less for TRC than for either DRC (18%, P < .05) or SFC (42%, P < .01). Tempering increased the integrity of rolled corn and reduced the amount of particles less than 2 mm in diameter by 54% (P < .01). Steam flaking corn increased (P < .01) proportion (78%) of the grain having a particle size distribution of greater than 8 mm, as compared with TRC (25%) and DRC (3%). Compared with DRC, tempering enhanced (P < .10) ADG (9%), feed efficiency (5%), and dietary NE (3%). Daily weight gain was similar (P > .10) for TRC and SFC. Feed efficiency (P < .10) and dietary NE (P < .01) were greater (6%) for SFC than for TRC. There were no differences (P > .10) between DRC and TRC in ruminal and total tract digestion of OM, N, and starch, and in ruminal microbial efficiency. Ruminal digestion of OM decreased (linear effect, P < .05) and ruminal microbial efficiency increased (linear effect, P < .05) with increasing surfactant concentration. Ruminal digestion of OM and starch, and flow of nonammonia N to the small intestine were greater (31, 56, and 14%, respectively, P < .01) for SFC than for TRC. Postruminal and total tract digestion of OM, N, and starch, and dietary DE were greater (P < .01) for SFC than for TRC. We concluded that tempering corn will enhance animal performance. Increasing the concentration of surfactant used in tempering may enhance ruminal microbial efficiency and lean tissue growth.

This paper studies both existence and spectral stability properties of bounded spatially periodic traveling wave solutions to a large class of scalar viscous balance laws in one space dimension with a reaction function of monostable or Fisher-KPP type. Under suitable structural assumptions, it is shown that this class of equations underlies two families of periodic waves. The first family consists of small amplitude waves with finite fundamental period which emerge from a Hopf bifurcation around a critical value of the wave speed. The second family pertains to arbitrarily large period waves which arise from a homoclinic bifurcation and tend to a limiting traveling (homoclinic) pulse when their fundamental period tends to infinity. For both families, it is shown that the Floquet (continuous) spectrum of the linearization around the periodic waves intersects the unstable half plane of complex values with positive real part, a property known as spectral instability. For that purpose, in the case of small-amplitude waves it is proved that the spectrum of the linearized operator around the wave can be approximated by that of a constant coefficient operator around the zero solution and determined by a dispersion relation which intersects the unstable complex half plane. In the case of large period waves, we verify that the family satisfies the assumptions of the seminal result by Gardner (Spectral analysis of long wavelength periodic waves and applications, J. Reine Angew. Math. 491 (1997), 149–181) of convergence of periodic spectra in the infinite-period limit to that of the underlying homoclinic wave, which is unstable. A few examples are discussed.

Two isonitrogenous diets (12.5% CP) containing 20 (20% NPN) or 40% (40% NPN) of the N as nonprotein N were evaluated with 0 or 10 mg laidlomycin propionate (LP)/kg in a 2 x 2 factorial arrangement. Changes in dietary NPN:N ratio were developed by partial substitution of urea N for fish meal N. In Trial 1, four Holstein steers (349 kg) with cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on digestive function. Total tract OM digestion was slightly greater (1.2%, P < .10) for diets containing 20% of N as NPN, due to greater (3.4%, P < .05) postruminal OM digestion. Supplemental LP decreased passage of microbial N to the small intestine (7.4%, P < .10) and ruminal degradation of dietary CP (DIP, 8.1%, P < .10). Decreasing the NPN:N ratio decreased microbial N flow to the small intestine (7.5%, P < .10) and DIP (15%, P < .01) and increased (6%; P < .05) the flow of indispensable amino acids to the small intestine. Supplemental LP increased (P < .10) ruminal pH. There were no treatment effects (P > .10) on ruminal molar proportions of acetate or propionate. In Trial 2, 120 Holstein steers (122 kg) were used to evaluate treatment effects on growth performance. Decreasing the NPN:N ratio increased ADG (P < .01) by 36, 40, and 16%, respectively, for the initial three 56-d periods of the trial. Overall, ADG was 17% greater (P < .01) for cattle consuming diets containing 20 vs 40% NPN. Decreasing the NPN:N ratio increased (P < .01) gain efficiency by 17 and 14%, respectively, for the initial two 56-d periods. Overall, gain efficiency was 6% greater (P < .01) for diets containing 20% NPN. Dietary NPN:N ratio did not influence (P > .10) the NE value of diets. Supplemental LP did not affect DMI (P > .10) but increased ADG (6%, P < .01) and gain efficiency (5%, P < .05) and decreased (11%, P < .05) the maintenance energy requirements. Protein nutrition limited growth performance of calves receiving the 20% NPN diets during the initial 112 d of the trial. With the 40% NPN diets, protein nutrition limited growth performance throughout most of the trial (d 1 to d 224). We conclude that LP will enhance daily weight gain and gain efficiency of calf-fed Holstein steers. Conventional urea-based diets will not diminish response to LP, although they may not meet the metabolizable amino acid requirements of calf-fed Holsteins during the first three-quarters of the feeding period.

No abstract

We used 216 Holstein steers (151 kg) in a 262-d trial to evaluate the influence of dietary magnesium level (.19, .25, and .32%) and laidlomycin propionate (LP; 0 vs 11 ppm, air-dry basis) on growth performance and NE value of the diet. During the initial 112 d of the trial, LP increased (P < .01) ADG (6.3%) and feed efficiency (4.2%). From d 112 until slaughter, LP increased (P < .05) ADG (9.7%) and feed efficiency (4.5%). Across the 262-d feeding period, LP supplementation enhanced (P < .01) ADG (8.9%) and feed efficiency (6.3%). There was an interaction (P < .05) between dietary Mg and LP on NE value of the diet. The enhancement in NE value of the diets owing to LP with .19, .25, and .32% dietary Mg were .5, 3.0, and 5.9%, respectively. Six Holstein steers (302 kg) were used in a 6 x 6 Latin square experiment to evaluate treatment effects on characteristics of ruminal and total tract digestion. There were no treatment interactions (P > .10) on site and extent of digestion of OM, starch, and N. Supplemental Mg increased (quadratic effect, P < .10) ruminal OM digestion. Neither LP nor dietary Mg level affected (P > .10) ruminal digestion of starch and feed N. Supplemental LP decreased (15%, P < .05) ruminal microbial efficiency. Total tract digestion of OM and N increased (linear effect, P < .01) with increasing dietary Mg level. There were interactions between LP and dietary Mg level on ruminal soluble-Mg concentration (linear effect, P < .01) and Mg absorption (quadratic effect, P < .05). Apparent total tract Mg digestion increased owing to LP (P < .01) and dietary Mg level (linear effect, P < .01). There were no treatment effects (P > .10) on ruminal pH. Dietary Mg level did not influence (P > .10) ruminal VFA concentrations or molar proportions. Supplemental LP increased (14%; P < .10) total ruminal VFA concentration but did not affect (P > .10) VFA molar proportions. We conclude that LP will increase daily weight gain and feed efficiency of calf-fed Holstein steers and that this response may be enhanced by increasing dietary Mg level.

One hundred twenty crossbred steers (294 kg, initially) were used in a 141-d finishing trial. Four concentrations (8, 16, 24, and 32% of diet DM) of cottonseed meal (CSM, prepressed solvent-extracted) replaced steam-flaked corn in a corn-based finishing diet. Increasing level of CSM decreased ADG (linear component, P < .10), feed efficiency (linear component, P < .01), and dietary NE (linear component, P < .01). Observed dietary NE was 99% of expected at 8 and 16% CSM but 95% of expected at higher levels of inclusion (linear component, P < .05). Level of CSM did not influence (P > .10) dressing percentage, longissimus area, fat thickness, or retail yield. Eight Holstein steers (285 kg) were used in a replicated 4 x 4 Latin square design to evaluate treatment effects on characteristics of digestion. Ruminal digestibility of OM decreased (linear component, P < .05) as CSM increased, although ruminal digestibility of starch and feed N were not affected (P > .10). Ruminal escape protein from CSM was 58%. Total tract starch digestion was not altered (P > .10), but total tract digestibility of OM and GE decreased (linear component, P < .05) and digestion of N increased (linear component, P < .01) as CSM replaced steam-flaked corn. The ratio of observed to expected DE value of the diets was similar across CSM levels, averaging .99. Thus, comparative DE value of CSM was not affected by level of inclusion, averaging 3.32 Mcal/kg. We conclude that the NEm and NEg values of CSM are 1.88 and 1.24 Mcal/kg, respectively, and in close agreement with tabular values. However, CSM should not exceed 16% of DMI, because higher levels may depress cattle performance and replacement value of CSM.