Post-weaning feed efficiency decreased in progeny of higher milk yielding beef cows.

Current trends in the beef industry focus on selecting production traits with the purpose of maximizing calf weaning weight; however, such traits may ultimately decrease overall post-weaning productivity. Therefore, the objective of this study was to evaluate the effects of actual milk yield in mature beef cows on their offspring's dry matter intake (DMI), BW, average daily gain, feed conversion ratio (FCR) and residual feed intake (RFI) during a ~75-day backgrounding feeding trial. A period of 24-h milk production was measured with a modified weigh-suckle-weigh technique using a milking machine. After milking, cows were retrospectively classified as one of three milk yield groups: Lower (6.57±1.21 kg), Moderate (9.02±0.60 kg) or Higher (11.97±1.46 kg). Calves from Moderate and Higher milk yielding dams had greater (P<0.01) BW from day 0 until day 75 at the end of the backgrounding feeding phase; however, day 75 BW were not different (P=0.36) between Lower and Moderate calves. Body weight gain was greater (P=0.05) for Lower and Moderate calves from the day 0 BW to day 35 BW compared with Higher calves. Overall DMI was lower (P=0.03) in offspring from Lower and Moderate cows compared with their Higher milking counterparts. With the decreased DMI, FCR was lower (P=0.03) from day 0 to day 35 in calves from Lower and Moderate milk yielding dams. In addition, overall FCR was lower (P=0.02) in calves from Lower and Moderate milk yielding dams compared with calves from Higher milk yielding dams. However, calving of Lower milk yielding dams had an increased (P=0.04) efficiency from a negative RFI value compared with calves from Moderate and Higher milking dams. Results from this study suggest that increased milk production in beef cows decreases feed efficiency during a 75-day post-weaning, backgrounding period of progeny.

High milk production decreases cow-calf productivity within a highly available feed resource environment.

The beef cattle industry tends to focus on selecting production traits with the purpose of maximizing cow-calf performance. One such trait is milking ability, which is considered the primary influence on weaning weight of the calf. Therefore, the objective of this study was to determine the effect of actual milk yield on reproductive performance, circulating blood metabolites, and calf performance in beef cows in the Southeastern US. Over a 2 yr period, data were collected from 237, 3- to 9-yr-old Angus-sired beef cows on 3 research stations in Tennessee. On approximately d 58 and 129 postpartum, 24-hr milk production was measured with a modified weigh-suckle-weigh technique using a milking machine. Subsamples of milk were collected for analysis of milk components. Milk yield data were used to retrospectively classify cows on actual milk yield as High ( ≥ 10 kg/d), Mod (8 to 9 kg/d), or Low ( < 8 kg/d). Cow body weight (BW) and body condition score (BCS) were collected weekly at each location through breeding. Calf BW was recorded at birth, mid-weight at d 58, and weaning. At d 58 and 129 of postpartum, milk yields were different (P < 0.001) among the treatment groups. Cow BW during the entire study were not different (P ≥ 0.22) with increasing milk yield. Timed-AI pregnancy rate were the lowest (P = 0.02) in the High milk producing cows with no difference (P > 0.05) between Low and Mod milk cows. In addition, overall pregnancy rate continued to be the lowest (P = 0.04) in High milk producing cows with the greatest pregnancy rate in Mod milk cows. Calf mid-weight at ∼d 58 was increased (P < 0.001) in calves from Mod and High milking cows. However, calf BW at weaning was not different (P = 0.22) among calves from different milk treatment groups. Results from this study suggest that even in management systems that modify the grazing environments with harvested feedstuffs, high milk production decreases reproductive efficiency. In addition, increasing milk production up to d 129 postpartum did not result in increased calf BW at weaning, indicating that the genetic potential for calf BW at weaning could not be improved with increased genetic potential for milk production.

Circulating beta-hydroxybutyrate concentration may be a predictive measurement for young cows that have a greater probability to conceive at a fixed-time artificial insemination.

Timing of conception, which has been indicated to be negatively influenced by metabolic dysfunctions, can influence lifetime productivity within the cow herd. Therefore, our objective was to analyze the association of milk production, serum metabolites as an indicator of nutrient status, cow BW and BW change, and calf BW with timing of pregnancy in 183 spring-calving beef cows. Cows were retrospectively classified by timing of pregnancy as cows that were diagnosed pregnant by timed AI (TAI; = 118) or natural breeding (NAT; = 65). In addition, cows were grouped by age to represent young (3 to 4 yr old), mature (5 to 6 yr old), and old (7 to 9 yr old) cows. Starting approximately d 30 postpartum, cow BW and BCS were recorded and blood samples were collected weekly through the end of breeding. Weekly serum samples were composited by cow within 2 production periods: 1) prebreeding and 2) TAI to end of NAT. Cow BW and BCS did not influence ( ≥ 0.40) timing of pregnancy during the entire study. Similarly, calf BW at birth and weaning were not different ( ≥ 0.30) between timing of pregnancy groups. However, calf BW at weaning and calf value the subsequent year of the study were greater ( < 0.01) for TAI cows than for NAT cows. An age group × treatment interaction ( < 0.01) occurred for serum ß-hydroxybutyrate (BHB). Serum BHB concentrations for mature and old cows were similar regardless of timing of pregnancy. However, serum BHB concentrations for young NAT cows were greater than for young TAI cows. In addition, serum NEFA exhibited ( = 0.04) a timing of pregnancy × sampling period interaction. Prebreeding serum NEFA concentrations were greater for NAT cows than for TAI cows. In contrast, serum NEFA concentrations during the NAT season were similar regardless of timing of pregnancy. Area under the curve of the receiver-operating characteristic curve for young cows' circulating BHB concentrations (0.66) was an acceptable predictor for pregnancy by TAI ( < 0.01). Results from this study indicate that only the young, postpartum beef cows during early lactation were susceptible to the measured metabolic dysfunctions of elevated blood BHB concentrations, which may have caused a delay in the timing of pregnancy.

Structural characterization of isolated mitochondrial cytochrome c1.

Resonance Raman spectroscopy (RRS) has been employed to characterize cytochromes c1 isolated from bc1 complexes of beef heart mitochondria and Rhodopseudomonas sphaeroides. The data obtained in this study extend the physical characterization of cytochromes c1 and focus on the effects of the local protein environment on the heme active site. While the general characteristics of the cytochromes c1 are similar to those of smaller soluble cytochromes c, the behavior of several core-size and ligation-sensitive heme modes reveal that significant systematic differences exist between those species. These, most likely, result from changes in the heme axial-ligand interactions.

Structural characterization of heme sites in spinach cytochrome b6f complexes: a resonance Raman study.

Resonance Raman spectra of cytochrome b6f complexes isolated from spinach chloroplasts have been obtained. Selective resonance enhancements and partial reductions of the complex by redox mediators were used to isolate and identify the contributions of heme b6 and heme f sites to the observed spectra. Corresponding spectra for turnip cytochrome f have also been obtained. Power-dependent photoreduction was observed in cytochrome f of the complex as well as in the isolated cytochrome f during the course of the Raman experiments.

FORAGES AND PASTURES SYMPOSIUM: Improving efficiency of production in pasture- and range-based beef and dairy systems.

Despite overall increased production in the last century, it is critical that grazing production systems focus on improving beef and dairy efficiency to meet current and future global food demands. For livestock producers, production efficiency is essential to maintain long-term profitability and sustainability. This continued viability of production systems using pasture- and range-based grazing systems requires more rapid adoption of innovative management practices and selection tools that increase profitability by optimizing grazing management and increasing reproductive performance. Understanding the genetic variation in cow herds will provide the ability to select cows that require less energy for maintenance, which can potentially reduce total energy utilization or energy required for production, consequently improving production efficiency and profitability. In the United States, pasture- and range-based grazing systems vary tremendously across various unique environments that differ in climate, topography, and forage production. This variation in environmental conditions contributes to the challenges of developing or targeting specific genetic components and grazing systems that lead to increased production efficiency. However, across these various environments and grazing management systems, grazable forage remains the least expensive nutrient source to maintain productivity of the cow herd. Beef and dairy cattle can capitalize on their ability to utilize these feed resources that are not usable for other production industries. Therefore, lower-cost alternatives to feeding harvested and stored feedstuffs have the opportunity to provide to livestock producers a sustainable and efficient forage production system. However, increasing production efficiency within a given production environment would vary according to genetic potential (i.e., growth and milk potential), how that genetic potential fits the respective production environment, and how the grazing management fits within those genetic parameters. Therefore, matching cow type or genetic potential to the production environment is and will be more important as cost of production increases.

Canine model for microvascular reconstruction of the larynx.

The experimental use of jejunal free grafts with microvascular anastomosis in the head and neck region has been reported in pharyngeal and esophageal reconstruction. Lack of a suitable animal model has limited basic research for cutaneous or myocutaneous microvascular techniques. This investigation upon appropriate graft sites in the canine was instituted. Following a vertical hemilaryngectomy, reconstruction of the laryngeal defect was accomplished by transferring 2.5 to 3.5 centimeters square of a free myocutaneous graft from the caudal ventral abdominal region. The skin surface of the graft was placed inward to reline the laryngeal lumen. The epigastric artery and vein attached to the free graft were anastomosed to the superior thyroid or laryngeal artery or vein. Four of the six animals survived the procedure. All animals which survived the surgery showed excellent preservation of the airway lumen, pseudocord formation, and viability of the graft.

Conserved nonplanar heme distortions in cytochromes c.

A nonplanar distortion of the heme of c-type cytochromes is conserved in the proteins isolated from diverse species based upon a comprehensive analysis of available high-resolution X-ray crystal structures. This distortion is induced through the cysteine thioether linkages between the porphyrin pyrrole groups and the polypeptide and results in an asymmetric pyrrole distortion. This asymmetry in the heme distortion is also conserved. For other heme proteins which lack these covalent bonds, nearly planar porphyrins are observed. Resonance Raman evidence indicates that nonplanar distortion of porphyrins containing metals, like iron, with large core sizes (> or = 2.00 A) is energetically unfavorable and can occur only in the presence of significant environmental perturbations. Further, energy minimization and dynamics calculations on the ferric form of yeast iso-1-cytochrome c, starting from the crystallographic coordinates and using a molecular mechanics force field which accurately reproduces nonplanar distortions in metalloporphyrins, suggest that this distortion is indeed maintained by the protein tertiary structure. It is proposed that this protein-linked heme distortion modulates electron transfer function through modification of redox potentials of the porphyrin ring and the protein binding properties of c-type cytochromes.

Resonance Raman characterization of Chromatium vinosum cytochrome c'. Effect of pH and comparison of equilibrium and photolyzed carbon monoxide species.

Resonance Raman spectra of Chromatium vinosum cytochrome c' have been obtained for the five pH-dependent states of the protein [i.e., types I (pH 7), II (pH 10), and III (pH 12) of the ferric protein and type a (pH 7) and type n (pH 12) of the ferrous protein]. The raman spectra of type II and type a are consistent with those of high-spin, 5-coordinate heme proteins, such as deoxyhemoglobin, while spectra of type III and type n correspond more closely to those of low-spin, ferric and ferrous cytochrome c, respectively. Spectra of the CO-bound equilibrium species qualitatively resemble those of carbon monoxy human HbA. However, both the Fe-C and C = O stretching modes of the ligated species exhibit pH-dependent frequency shifts. Our data also indicate that CO photolysis is much more efficient at pH 7 than at pH 12. Moreover, the spectra of the photolytic transients suggest that unique, high-spin species are formed subsequent to CO photolysis from both type a and type n species.

Transient and time-resolved resonance Raman investigation of photoinitiated electron transfer in ruthenated cytochromes c.

Ruthenation of exterior amino acid residues of heme proteins provides an effective means by which biological ET reactions can be studied within the context of highly complex protein environments. Resonance Raman spectroscopy can probe both ET kinetics and structural dynamics at the molecular level. Here we present the first comprehensive use of time-resolved and transient resonance Raman spectroscopies to examine photoinduced ET in cytochromes. Two ruthenated cytochromes c, Ru(lys72)-cyt.c and Ru(cyt102)cyt.c, were studied with TRRS using 10 ns laser pulses and with TRRRS on a 10 ns to 10 ms time scale. It was found that resonance Raman protocols can effectively trace ET kinetics and associated heme--protein structural dynamics. Care must be exercised, however, when drawing comparisons to measurements made by other methods (i.e., transient absorbance). The TRRS studies directly probe the heme and its local environment and reveal that the heme dynamics accompanying ET are very rapid relative to phenomenological ET kinetics. The heme and its local environment evolve to their equilibrium (ferrous) structure in less than 10 ns subsequent to ET, with no evidence for the existence of metastable heme pocket geometries analogous to those observed in the dynamic response of hemoglobins and oxidases. Finally, species-specific differences are observed in the photoinduced ET kinetics and heme structural dynamics. However, these differences are confined to nanosecond or faster time scales.