Effects of dietary copper source and concentration on carcass characteristics and lipid and cholesterol metabolism in growing and finishing steers

We conducted an experiment to determine the effects of dietary copper (Cu) source and level on carcass characteristics, longissimus muscle fatty acid composition, and serum and muscle cholesterol concentrations in steers. Sixty Angus and Angus x Hereford steers were stratified by weight and initial liver Cu concentration within a breed and randomly assigned to treatments. Treatments consisted of: 1) control (no supplemental Cu); 2) 20 mg Cu/kg DM from Cu sulfate (CuSO4); 3) 40 mg Cu/kg DM from CuSO4; 4) 20 mg Cu/kg DM from Cu citrate; 5) 20 mg Cu/kg DM from Cu proteinate; and 6) 20 mg Cu/kg DM from tribasic Cu chloride. A corn silage-soybean meal-based diet was fed for 56 d. Steers were then switched to a high-concentrate diet. Equal numbers (n = 5) of steers per treatment were slaughtered after receiving the finishing diets for either 101 or 121 d. Serum cholesterol was not affected by treatment during the growing phase but was decreased (P < .05) in steers supplemented with Cu by d 84 of the finishing period and remained lower (P < . 05) at subsequent sampling periods. Longissimus muscle cholesterol concentration tended to be reduced (P < .11) by Cu supplementation. Hot carcass weight and backfat were lower (P < .05) in animals receiving supplemental Cu. However, Cu-supplemented and control steers had similar marbling scores. Longissimus muscle polyunsaturated fatty acid concentrations (18:2 and 18:3) were increased (P < .07) and saturated fatty acid concentrations tended (P < . 11) to be reduced by Cu supplementation. These results indicate that as little as 20 mg of supplemental Cu/kg diet can reduce backfat and serum cholesterol and increase muscle polyunsaturated fatty acids in steers fed high-concentrate diets.     

Dietary copper effects on lipid metabolism, performance, and ruminal fermentation in finishing steers

Sixty Angus steers (391.1+/-6.1 kg) were used to determine the effects of dietary Cu concentration on lipid metabolism and ruminal fermentation. Steers were stratified by weight and randomly assigned to treatments. Treatments consisted of 0 (control), 10, or 20 mg of supplemental Cu (as CuSO4)/kg diet DM. Steers were housed in pens equipped with individual electronic Calan gate feeders. On d 86 and 92, ruminal fluid was collected from two steers/treatment for IVDMD determination. Equal numbers of steers per treatment were slaughtered after receiving the finishing diets for 96 or 112 d. Gain, feed intake, feed efficiency, IVDMD, and ruminal VFA molar proportions were not affected by Cu supplementation. Copper supplementation increased (P < .05) liver Cu concentrations, and steers supplemented with 20 mg Cu/kg DM had higher (P < .05) liver Cu concentrations than steers supplemented with 10 mg Cu/kg DM. Serum total cholesterol concentrations were reduced by d 56 and at subsequent sampling dates in steers receiving supplemental Cu. Longissimus muscle cholesterol concentrations were lower (P < .10) in steers supplemented with Cu. Backfat depth was less (P < .05) in steers receiving supplemental Cu, but marbling scores were similar across treatments. Unsaturated fatty acid composition of longissimus muscle was increased (P < .05) and saturated fatty acid composition tended (P < .12) to be reduced in Cu-supplemented steers. Polyunsaturated fatty acid concentrations were higher (P < .05) in steers receiving Cu. These results indicate that addition of 10 or 20 mg Cu/kg to a high-concentrate diet containing 4.9 mg Cu/kg DM alters lipid and cholesterol metabolism in steers but does not affect ruminal fermentation.     

Dietary copper effects on lipid metabolism and circulating catecholamine concentrations in finishing steers

Forty-eight Angus and Hereford x Angus steers were used to determine the effects of copper (Cu) on lipid and catecholamine metabolism. Steers were stratified by weight within breed and randomly assigned to treatments. Treatments consisted of 0 (control, no supplemental Cu), 10, or 40 mg of supplemental Cu (from Cu2(OH)3Cl)/kg DM. Steers were fed a corn silage-soybean meal-based growing diet for 42 d. Animals were then switched to a high-concentrate finishing diet and remained on the same dietary treatments. On d 70, indwelling jugular catheters were nonsurgically inserted into five steers per treatment. Blood samples were obtained from steers after a 24-h period of feed withdrawal, 1 h after feeding, and after i.v. administration of norepinephrine and were subsequently analyzed for nonesterified fatty acid (NEFA) and catecholamine concentrations. Average daily gain over the finishing period was higher (P < 0.06) in steers receiving supplemental Cu. Serum total cholesterol concentrations were reduced (P < 0.05) on d 84 and 112 in steers supplemented with Cu. Serum norepinephrine (P < 0.14) and NEFA concentrations following feed withdrawal tended (P < 0.12) to be higher in Cu-supplemented steers. Postfeeding norepinephrine concentrations tended to be higher (P < 0.14) in Cu-supplemented steers. Nonesterifled fatty acid concentrations were lower (P < 0.10) in Cu-supplemented steers after norepinephrine administration. Backfat depth was decreased (P < 0.10) and longissimus muscle polyunsaturated fatty acid percentages were increased (P < 0.10) in steers receiving supplemental Cu. These results indicate that Cu addition to a finishing diet containing 5 mg Cu/kg DM alters lipid metabolism. The reduction in backfat depth may be due to copper altering catecholamine metabolism in steers.     

Suppression of testicular function using two dose rates of a reversible water soluble gonadotrophin releasing hormone (GnRH) vaccine in colts

Objective: To investigate the effect of two dose rates (200 and 400 ng) of a gonadotrophin releasing hormone (GnRH) vaccine on testicular function. Design: A vaccination dose rate experiment. Procedure: Two injections were administered 4 weeks apart to six colts in each treatment group. To maintain immunosuppression until the end of the breeding season, a third injection was given if antibody titres fell below 1000. Results: Effective antibody titres were present for 12 to 27 weeks. Testosterone concentrations decreased from 2.22 to 0.31 nmol/L 6 weeks after primary vaccination. Androstenedione concentrations decreased from 1.78 to 0.28 nmol/L 5 weeks after vaccination. Testosterone and androstenedione concentrations above 0.69 and 0.87 nmol/L were attained 31 to 43 weeks after vaccination. Mean scrotal widths and lengths decreased over 29 weeks from 9.2 cm and 9.7 cm to 6.7 cm and 7.6 cm. At surgical castration these dimensions were 10.1 cm and 11.0 cm. Mean semen characteristics before vaccination and after recovery were: gel-free volume 16.5 and 13.5 mL, sperm concentration 295.5 times 10⁶ 315.6 times 10⁶/mL, total sperm per ejaculate 4041 times 10⁶ 4657 times 10⁶ live normal spermatozoa 32% and 60%. Histologically, the testes showed active spermatogenesis. The mean testicular parenchyma weights for the 200 and 400 mg groups were 129.0 g and 109.8 g. Daily sperm production per testis and per gram of testis for the 200 and 400 mg groups were 3.7 times 10⁸ 2.8 times 10⁶ 2.3 times 10⁸ 2.0 times 10⁶. Conclusions: Both dose rates suppressed testicular function. Data showed that the vaccine effects were reversible. Individual immune response was less varied in the 200 mg group. Further work is necessary to achieve a less variable response in the immunosuppression of testicular function.     

A comparison of noninvasive cardiac output measurement by partial carbon dioxide rebreathing with the lithium dilution technique in anesthetized foals

Newer techniques for cardiac output (Q) determinations that are minimally invasive remain to be validated in neonatal foals against other accepted techniques such as the lithium technique (LiDCO). This study compares Q determinations using the partial CO₂ rebreathing technique (NICO) with LiDCO in anesthetized neonatal foals. Ten foals were instrumented for NICO and LiDCO determinations. For each foal low, intermediate and high levels of cardiac output were achieved in that order using an end‐tidal isoflurane (ETI) concentration of 1.3 – 2.1% for the lowest rate; an ETI of 0.85–1.4% and a constant‐rate infusion of dobutamine (1–3 ?g/kg/min) for the intermediate rate; and an ETI of 0.83–1% and dobutamine (2–6 ?g/kg/min) for the highest rate. Four foals also received IV intermittent doses (total cumulative dose of 1.1–1.7 mg) of phenylephrine at the highest rate of Q. The measurements were obtained in duplicate or triplicate for each Q technique after achieving a stable hemodynamic plane for at least 15 minutes at each rate of Q. For the lithium technique, all foals received 1.1–1.9 mL (0.16–0.28 mmol) of lithium. A Bland‐Altman analysis was used to compare the bias and precision of the two techniques. Eighty seven comparisons were determined between the two techniques. Eight were excluded due to more than 20% variation between the LiDCO determinations or technical errors at the time of determination. The correlation coefficient between the two methods was 0.67 for all Q determinations. Mean LiDCO and NICO values from 79 measurements were 130 ± 40 mL^–1 kg minute^–1 (range, 68– 237) and 152 ± 31 mL^–1 kg minute^–1 (89 – 209), respectively. The mean ( mL^–1 kg minute^–1) of the differences of LiDCO – NICO was = –0.7248 + 0.8602 NICO. The precision (1.96 SD) of the differences between LiDCO and NICO was 58.9 mL^–1 kg minute^–1 (–80.9–+36.9) with a mean difference of –22 mL^–1 kg minute^–1 (bias; 95% CI – 15.2 to ‐28.7). In conclusion, given the small bias compared to the limits of agreement, the NICO technique for determining Q deserves further consideration for adoption into clinical practice in neonatal foals.     

Markov models of land cover dynamics in a southern Great Plains grassland region

Grassland regions of the southern Great Plains are fragmented by agricultural activity and many habitat remnants have experienced encroachment by juniper (Juniperus virginiana L.). Recently, many cropland areas have been converted to monoculture grassland (pastures) and enrolled into the Conservation Reserve Program (CRP). Our objectives were to develop spatial and temporal Markov models to characterize land cover dynamics relative to juniper expansion and CRP using aerial photography from 1965, 1981, and 1995. We used landscapes surrounding three Breeding Bird Survey routes with varying levels of juniper encroachment in Oklahoma as study areas. As expected, land cover changes from 1965 to 1995 included increases in juniper woodland, mixed juniper-deciduous woodland, and pastures from CRP activity. Markov models revealed that juniper had a low likelihood of self-replacement in early stages of encroachment. In all areas, relatively little native grassland was lost to juniper encroachment, but other native habitat types such as deciduous woodland were heavily impacted. Transition probabilities for land cover dynamics varied significantly both spatially and temporally. Projections of these raw transition matrices produced widely varying models of future land cover conditions. By modifying the matrices to account for recent and potential socio-political and ecological changes occurring in this region, a number of more plausible land cover scenarios were produced than those resulting from simple projections of raw transition matrices.     

纯种日本和牛与西门塔尔杂交牛与西门塔尔牛肉品质对比分析

[目的]旨在研究和牛杂交牛(日本和牛♀×西门塔尔牛♂)与西门塔尔牛的肉品质性能。[方法]选择相同月龄、体重相近的和牛杂交牛和西门塔尔牛各5头,屠宰后选取背最长肌分析肉品质特性。[结果]结果表明,和牛杂交牛的粗脂肪显著高于西门塔尔牛(P0.05);粗蛋白、成人必需氨基酸和鲜味氨基酸相比西门塔尔牛表现出良好的优势(P0.05);饱和脂肪酸含量降低,单不饱和脂肪酸和多不饱和脂肪酸含量相比西门塔尔牛有所升高(P0.05)。[结论]说明和牛杂交牛具有较好的营养价值,其肉品质略优于西门塔尔牛。     

Microbial factor-mediated development in a host-bacterial mutualism

Tracheal cytotoxin (TCT), a fragment of the bacterial surface molecule peptidoglycan (PGN), is the factor responsible for the extensive tissue damage characteristic of whooping cough and gonorrhea infections. Here, we report that Vibrio fischeri also releases TCT, which acts in synergy with lipopolysaccharide (LPS) to trigger tissue development in its mutualistic symbiosis with the squid Euprymna scolopes. As components of PGN and LPS have commonly been linked with pathogenesis in animals, these findings demonstrate that host interpretation of these bacterial signal molecules is context dependent. Therefore, such differences in interpretation can lead to either inflammation and disease or to the establishment of a mutually beneficial animal-microbe association.     

Reducing Catfish Farm Losses Due to Dockages Assessed by Processing Plants

Dockages can have a significant effect on catfish, Ictalurus punctatus, farm revenues. This study was conducted to quantify common dockages, examine seasonal and yearly variations in dockages assessed, and determine optimal production practices given various dockage scenarios. A convenience survey of invoice records from 30 commercial catfish farms and 10 processing plants provided 3686 daily catfish load records that were used to quantify dockages. A linear programming model was developed to examine optimal production practices given 11 alternative production scenarios with five size‐grading technologies subject to 24 types and levels of dockages. The survey revealed that 95% of catfish loads delivered to processing plants between 1997 and 2002 were assessed dockages that resulted in average losses of 2.45% per load or $0.066/kg of catfish marketed over the study period. Out‐of‐size discounts constituted the greatest losses. Dockage losses can be reduced by shifting either to longer‐term single‐batch production or more intensive grading. Longer‐term production results in fewer smaller fish that would incur dockage losses. However, cash flow constraints require more intensive early‐season grading. The grader choice depended on the dockage tolerance level and rate, the frequency distribution of sizes of catfish in the population, the efficiency of the grading technology, and the cost of the grading method. Larger farms minimize losses with intensive active grading (University of Arkansas at Pine Bluff grader).