Choices between red clover and fescue in the diet can be reliably estimated in heifers post-weaning using n-alkanes.

Measuring diet choice in grazing animals is challenging, complicating the assessment of feed efficiency in pasture-based systems. Furthermore, animals may modify their intake of a forage species depending on its nutritive value and on their own physiological status. Various fecal markers have been used to estimate feed intake in grazing animals. However, plant-wax markers such as n-alkanes (ALK) and long-chain alcohols may provide reliable estimates of both dietary choices and intakes. Still, their use in beef cattle has been relatively limited. The present study was designed to test the reliability of the ALK technique to estimate diet choices in beef heifers. Twenty-two Angus-cross heifers were evaluated at both post-weaning and yearling age. At each age, they were offered both red clover and fescue hay as cubes. Following 3-week acclimation periods, daily intake of each forage species was assessed daily for 10 days. During the final 5 days, fecal grab samples were collected twice daily. The ALK fecal concentrations were adjusted using recovery fractions compiled from literature. Diet composition was estimated using two statistical methods. Post-weaning, dietary choices were reliably estimated, with low residual error, regardless of the statistical approach adopted. The regression of observed on estimated red clover proportion ranged from 0.85±0.08 to 1.01±0.09 for fecal samples collected in the p.m. and for daily proportions once averaged, respectively. However, at yearling age, the estimates were less reliable. There was a tendency to overestimate the red clover proportion in diets of heifers preferring fescue, and vice versa. This was due to greater variability in ALK fecal concentrations in the yearling heifers. Overall, the ALK technique provided a reliable tool for estimating diet choice in animals fed a simple forage diet. Although further refinements in the application of this methodology are needed, plant-wax markers provide opportunities for evaluating diet composition in grazing systems in cattle.

Technical note: Development of a noninvasive respiration rate sensor for cattle.

The measurement of the respiration rate (RR) in cattle is a valuable tool for monitoring health status. Thus, an RR sensor can be essential for stress detection, especially heat stress. Heat stress leads to a deviation of the normal RR and results in a decrease of milk production and fertility. Therefore, continuous monitoring of the RR can help early detection of heat stress and, thus, initiate timely counteractive actions to minimize physical stress. The most common method to measure the RR in cattle is to count the flank movement visually; however, this method is time-consuming and labor-intensive. In addition, the continuous measurement of the RR is difficult to implement and can be physically strenuous. Therefore, a device based on a differential pressure sensor that can record RR automatically has been developed to make continuous long-term studies possible. The aim of this study was to validate the data measured by the device with the help of a reference method. The reference method used was counting the flank movements of a total of 6 cows (Holstein-Friesian). The rear flank movements of each cow were recorded by a camera and counted independently of the device by an observer. Eight videos of 1 min each were recorded per cow. The data analysis was done with cows in 3 different body positions: dozing, lying, and standing. A total of 48 RR measurements of the device were compared with the counted RR frequencies of the video recording. The results were highly correlated during dozing [correlation coefficient (r) = 0.92, n = 13], lying (r = 0.98, n = 15), and standing (r = 0.99, n = 20). The evaluation showed that the device is suitable for automated RR counting. Further development of a marketable device is planned.

Feed intake and diet selection in Angus-cross heifers of two frame sizes at two stages of growth.

Assessing feed efficiency in pasture-based systems can be challenging due to difficulties in measuring feed intake and diet preference. Furthermore, heifers may modify their intake of a particular forage species depending on its nutritive and physical attributes and on their own physiological status. For instance, heifers growing to larger mature sizes have higher maintenance requirements, which may affect their dietary preferences. The present study was designed to determine the influence of frame size (FS) on feed intake and diet selection at 2 age subclasses: postweaning, at, on average, 313 d of age (317 kg BW for larger FS and 285 kg BW for smaller FS), and as yearlings, at, on average, 403 d of age (391 kg BW for larger FS and 343 kg BW for the smaller FS). Twenty-four Angus-cross heifers were evaluated at these ages. They were housed in a drylot equipped with a Broadbent Feeding System and had ad libitum access to cubed red clover and cubed fescue hay in separate buckets. Following 3-wk acclimation periods, DMI of each forage species was assessed daily for 10 d. Body weights were also recorded daily over those 10 d. Larger and smaller FS cattle did not differ in ADG, feed conversion ratio, and Kleiber ratio at either age (P > 0.05). However, heifers from larger FS category had higher total and red clover DMI at both ages (P < 0.05) and higher proportions of red clover in their diet as yearlings (P < 0.001). Cumulative differences between clover and fescue DMI were similar at postweaning in both FS (P > 0.05); however, at yearling age, the larger FS cattle ate consistently and cumulatively more red clover (P < 0.001). The intake and diet selection of heifers across ages were not consistent for either FS category (P = 0.748), suggesting difficulties in predicting lifetime feed efficiencies based on an early measure. Although gains and feed conversion ratios were similar between FS categories, the larger FS heifers ate more. At yearling age, these heifers of larger metabolic size also selected a greater proportion of red clover in their diet. Because the FS and, thereby, BW of cattle affect intakes and diet selections, they also may impact the composition and sustainability of grasslands generally. Therefore, the relationship between FS and pasture usage likely needs to be integrated into descriptions of cow efficiency in pasture-based operations.

Forage systems for cow-calf production in the Appalachian region.

Small cow-calf operations are common in the Appalachian region. Tall fescue [Lolium arundinaceum (Schreb.) S. J. Darbyshire] is the dominant forage in these systems for direct grazing as well as for stockpiling. The present study was conducted from 2001 to 2005. A total of 108 Angus and Angus crossbred cows were allotted randomly to 6 forage systems and then to 3 replicates within each system. In brief, system 1 had a stocking rate of 0.91 ha/cow in a Middleburg 3-paddock (A, B, and C) system. System 2 was similar to system 1 except for a stocking rate of 0.71 ha/cow. A stocking rate of 0.71 ha/cow also was used in systems 3 through 6. All A paddocks had tall fescue, whereas B paddocks had tall fescue/white clover (Trifolium repens L.) except in system 6, which had tall fescue/lespedeza [Lespedeza cuneata (Dum. Cours.) G. Don]. System 3 evaluated a 2-paddock (A and B) rotational grazing system, and system 4 evaluated a 3-paddock (A, B, and C) rotational grazing system, with paddock C containing orchardgrass (Dactylis glomerata L.) and alfalfa (Medicago sativa L.). Systems 5 and 6 differed from system 2 in the areas of paddocks B and C as well as in the forage mixtures used. In paddock C, system 5 had switchgrass (Panicum virgatum L.) and system 6 had tall fescue and birdsfoot trefoil (Lotus corniculatus L.). System 1 had the greatest average herbage availability from weaning until breeding (P < 0.05) with the least amount of hay fed (P = 0.03) when compared with the remainder of the systems. Differences (P > 0.05) in percentage of ground cover were not detected among systems. There was no year x system interaction effect on the cow or calf performance variables evaluated and no treatment effect on cow performance variables. There was a treatment effect on calf performance variables. System 2 produced the greatest adjusted weaning weight, kilograms of calf weaned per hectare, and kilograms of calf per kilograms of cow at weaning (P < 0.05). Numerical ranking for total calf production per hectare from the greatest to least was system 2, 6, 3, 5, 4, and 1. Systems evaluated did not affect cow performance although differences in calf performance and overall productivity of the systems were observed.

Parenteral selenium and vitamin E supplementation of weaned beef calves.

BACKGROUND: The weaning process in beef calves elicits physiological stress responses that can negatively affect performance and health. Supplementation of vitamins and minerals, particularly selenium (Se) and vitamin E, might be warranted. HYPOTHESIS: That parenteral administration of Se or vitamin E would correct or prevent deficiencies of these nutrients in postweaned beef calves during a backgrounding period (42 days after weaning). ANIMALS: One hundred and forty-four weaned steers (200-250 kg) in 3 trials. METHODS: One trial was conducted with cattle on a dry lot fed a total mixed ration and 2 trials were conducted on cattle on pasture. Selenium was administered at 0.05 mg/kg BW (SC) and vitamin E was administered at 1500 IU on days 0 and 28 (SC). RESULTS: A treatment effect attributable to Se or vitamin E supplementation on average daily gain was not detected in any trials. Parenteral supplementation with Se on days 0 and 28 resulted in higher serum Se concentrations as compared with controls on day 42. Parenteral supplementation with Se on days 0 and 28 improved Se status from marginal to adequate in 1 trial. Parenteral supplementation with vitamin E did not improve serum vitamin E concentrations in any experiment. CONCLUSIONS AND CLINICAL IMPORTANCE: Supplementation with vitamin E or Se or a combination of both did not have a significant effect on calf performance during the 42-day backgrounding period.

No linkage or association of telomeric and centromeric T-cell receptor beta-chain markers with susceptibility to type 1 insulin-dependent diabetes in HLA-DR4 multiplex families.

The T-cell receptor beta locus (TCRB) on chromosome 7q35 was studied as a candidate region for genetic susceptibility to type 1 insulin-dependent diabetes (IDDM). A highly polymorphic microsatellite marker mapping to the TCRBV6.7 gene and a TCRB C-region RFLP were used to genotype the members of a total of 21 multiplex IDDM families from two different geographical areas. There was no evidence to support linkage to either of these markers with IDDM, and conventional two-point analysis excluded linkage to the telomeric end of the TCRB complex, in the region of the highly informative TCRBV6.7 marker. There was significant linkage of IDDM to the class II HLA-D locus with significant lod scores > 3.0 obtained for the HLA-DRB1 and HLA-DQB1 genes. Affected sib-pair (ASP) and transmission disequilibrium (TDT) association tests confirmed these findings.

Clinical pathogenesis and diagnosis of osteoarthritis.

New insights into the metabolism of cartilage have increased respect for efforts designed to prevent osteoarthritis. The aging of the population adds to the desire to diagnose and manage the disease before patients become seriously disabled.

Axial skeletal changes in paralysed patients may mimic ankylosing spondylitis.

Patients with paralysis may develop radiographic changes in the axial skeleton and sacroiliac joints that resemble those seen in ankylosing spondylitis. These similarities can result in confusion when evaluating paralysed patients with back pain. We report on a patient with paralysis secondary to amyotrophic lateral sclerosis who developed back pain, apparent sacroiliac joint fusion, and a 'bamboo spine', leading to the misdiagnosis of ankylosing spondylitis. Serial radiographs of the bony changes in our patient are presented, along with a brief review of the literature on axial skeletal abnormalities in paralysis and a discussion of the subtle changes that distinguish immobilization spondyloarthropathy from ankylosing spondylitis.

Zinc-induced sideroblastic anemia: report of a case, review of the literature, and description of the hematologic syndrome.

Zinc ingestion has become increasingly popular in the lay and food faddist population. Herein described by way of a case report and review of the 13 cases in the literature is the syndrome of severe anemia associated with excessive and prolonged intake of oral zinc. The syndrome is characterized by anemia, granulocytopenia, and bone marrow findings of vacuolated precursors and ringed sideroblasts. Serum analysis reveals increased zinc levels, decreased copper levels, and a decrease in ceruloplasmin. The mechanism appears to be zinc-induced copper deficiency, which is instrumental in producing the profound bone marrow abnormalities, as zinc itself is of low toxicity. Importantly, the syndrome is totally reversible with cessation of zinc intake. Hematologists should be aware of this form of reversible sideroblastic anemia.