Circulating ghrelin concentrations fluctuate relative to nutritional status and influence feeding behavior in cattle

The objective of these experiments was to establish the relationship of plasma ghrelin concentrations with feed intake and hormones indicative of nutritional state of cattle. In Exp.1, 4 steers (BW 450 +/- 14.3 kg) were used in a crossover design to compare plasma ghrelin concentrations of feed-deprived steers with those of steers allowed to consume feed and to establish the relationship of plasma ghrelin concentrations with those of GH, insulin (INS), glucose (GLU), and NEFA. After adaptation to a once-daily feed offering (0800), 2 steers continued the once-daily feeding schedule (FED), whereas feed was withheld from the other 2 steers (FAST). Serial blood samples were collected via indwelling jugular catheter from times equivalent to 22 h through 48 h of feed deprivation. Average plasma ghrelin concentrations were greater (P < 0.001) in FAST compared with FED (690 and 123 +/- 6.5 pg/mL) steers. Average plasma ghrelin concentrations for FED steers prefeeding were elevated (P < 0.001) when compared with those postfeeding (174 and 102 +/- 4.2 pg/mL, respectively). Average plasma GH concentration was elevated (P < 0.05) for FAST steers compared with FED steers. Plasma GLU concentrations were not different; however, for FAST steers, NEFA concentrations were elevated (P < 0.001) and INS concentrations were decreased (P < 0.001). In Exp. 2, 4 steers (BW 416 +/- 17.2 kg) were used in a crossover design to determine the effects of i.v. injection of bovine ghrelin (bGR) on plasma GH, INS, GLU, and NEFA concentrations; length of time spent eating; and DMI. Steers were offered feed once daily (0800). Serial blood samples were collected from steers via indwelling jugular catheter. Saline or bGR was injected via jugular catheter at 1200 and 1400. A dosage of 0.08 microg/kg of BW bGR was used to achieve a plasma ghrelin concentration similar to the physiological concentration measured in a FAST steer in Exp. 1 (1,000 pg/mL). Injection of bGR resulted in elevated (P < 0.005) plasma GH concentrations after the 1200 but not the 1400 injection. Plasma INS, GLU, and NEFA concentrations were not affected by bGR injection. For the combined 1-h periods postinjection, length of time spent eating was greater (P = 0.02) and DMI tended to be increased (P = 0.06) for bGR steers. These data are consistent with the hypothesis that ghrelin serves as a metabolic signal for feed intake or energy balance in ruminants.     

Use of 25-hydroxyvitamin D3 and dietary calcium to improve tenderness of beef from the round of beef cows

The objective of this trial was to determine how 25-hydroxyvitamin D(3) (25-OH D(3)) supplementation, altering supplemental dietary calcium, or their combination influence postmortem biochemical and tenderness changes in muscles from the round of mature cows. Twenty-seven Angus cows (3 to 7 yr old) were allotted randomly to 9 pens with 3 cows per pen. Treatments were arranged in a 3 x 3 factorial design with 3 dosages of 25-OH D(3) (0, 250, or 500 mg of 25-OH D(3) administered as a 1-time oral bolus 7 d before slaughter) and 3 percentages of supplemental limestone (0.5, 0.75, and 1.0%) replenished in the diet for 3 d before slaughter and after a 2-wk limestone withdrawal. Plasma samples were obtained during the feeding period. Upon slaughter, adductor, gracilus, pectineus, sartorius, semimembranosus, vastus intermedius, and vastus lateralis muscles were obtained and aged for 1, 3, or 7 d. Calcium concentrations were increased in plasma when 250 or 500 mg of 25-OH D(3) were administered (P 相似文献   

In Vivo and In Vitro Sperm Interaction with Oviductal Epithelial Cells of Llama

Sperm reservoirs in South American Camelids would be crucial for successful fertilization. Since ovulation occurs approximately 36 h after mating, the maintenance of the sperm viability in the oviduct waiting for the ovum is a critical reproductive event. Our study aimed at determining whether the isthmus or the utero tubal junction (UTJ) could function as a sperm reservoir in llama by means of in vivo and in vitro experiments. For the in vivo experiments, the oviducts of adult females with a dominant follicle bigger than 7 mm were examined for the presence of sperm at 6, 18, 24, 28 and 35 h after mating. The results using scanning and transmission electron microscopy showed ultrastructural differences between isthmus and UTJ with respect to (1) predominance of secretory cells in the UTJ and ciliated cells in the isthmus epithelium and (2) cytoplasmic bulbous projection of the secretory cells in the UTJ. Sperm adhered by a mucus‐like substance were seen only in the UTJ at 6, 18, 24 and 28 h post‐mating. Lack of sperm adhered to oviductal mucosa was observed around ovulation (35 h). In vitro experiments demonstrated higher ability of UTJ epithelial cell explants with respect to isthmus explants to bind sperm in a co‐cultured system. The anatomical features and the presence of a sperm bonding agent in the UTJ together with the in vitro differential binding of sperm to UTJ explants strongly suggest that both may be feasible mechanisms that facilitate sperm storage in this oviductal region in llama.     

Estimation of relationships between mineral concentration and fatty acid composition of longissimus muscle and beef palatability traits

The objective of this study was to determine the influence of beef LM nutrient components on beef palatability traits and evaluate the impact of USDA quality grade on beef palatability. Longissimus muscle samples from related Angus cattle (n = 1,737) were obtained and fabricated into steaks for trained sensory panel, Warner-Bratzler shear force (WBSF), lipid oxidation measured by thiobarbituric acid reactive substances (TBARS), fatty acid, and mineral composition analysis. Pearson phenotypic correlations were obtained by the correlation procedure of SAS. Beef palatability data were analyzed by the GLM procedure of SAS with USDA quality grade as the main effect. Specific mineral concentrations did not demonstrate strong correlations with WBSF or sensory traits (r = -0.14 to 0.16). However, minerals appeared to have a stronger relationship with flavor; all minerals evaluated except Ca and Mn were positively correlated (P < 0.05) with beef flavor. Stearic acid (C18:0), C18:2, C20:4, and PUFA were negatively correlated (P < 0.05) with all 3 panelist tenderness traits (r = -0.09 to -0.22) and were positively correlated (P < 0.05) with WBSF (r = 0.09 to 0.15). The MUFA were positively correlated (P < 0.05) with panelist tenderness ratings (r = 0.07 to 0.10) and negatively associated (P < 0.05) with WBSF (r = -0.11). The strongest correlations with juiciness were negative relationships (P < 0.05) with C18:2, C18:3, C20:4, and PUFA (r = -0.08 to -0.20). Correlations with beef flavor were weak, but the strongest was a positive relationship with MUFA (r = 0.13). Quality grade affected (P < 0.05) WBSF, TBARS, and all trained sensory panel traits, except livery/metallic flavor. As quality grade increased, steaks were more tender (P < 0.05), as evidenced by both WBSF and sensory panel tenderness ratings. Prime steaks were rated juiciest (P < 0.05) by panelists, whereas Select and Low Choice were similarly rated below Top Choice for sustained juiciness. Quality grade influenced (P < 0.05) beef flavor, but not in a linear fashion. Although there were significant correlations, these results indicate tenderness, juiciness, and flavor are not strongly influenced by individual nutrient components in beef LM. Furthermore, the positive linear relationships between USDA quality grade and beef palatability traits suggest quality grade is still one of the most valuable tools available to predict beef tenderness.     

Evaluation of urea dilution as a technique for estimating body composition of beef steers in vivo: validation of published equations and comparison with chemical composition

Urea dilution equations for prediction of empty body water in live cattle, developed by three separate groups of investigators, were evaluated by comparing empty body water calculated by these equations with that measured chemically in 6-, 12- and 18-mo-old crossbred beef steers (n = 10, 9 and 9, respectively). Of four equations for prediction of percent empty body water, one derived from mixed-breeds of steers overestimated empty body water in the 6-mo-old steers by 7.59% (P less than .05). For the 12- and 18-mo-old steers, calculated and measured percent empty body water did not differ (P greater than .05). Of seven equations for calculation of empty body water volume, two derived from Angus steers with an without live weight in the equation, and one derived from a combination of Angus and mixed-breeds of steers overestimated empty body water (P less than .05) in the 6-mo-old steers. No differences (P greater than .05) between calculated and measured empty body water volume were observed for either the 12- or 18-mo-old steers. When calculated empty body water values were regressed against that measured directly, all regression slopes were not different from 1 (P greater than .05). Intercepts from regressions involving percent empty body water (four equations) were not different from 0. Three of the seven equations for calculation of empty body water volume, one derived from bulls and the others from Angus steers had intercept estimates not different (P greater than .05) from 0. Validity required that these regressions have slopes not different from 1 and intercepts not different from 0. Empty body water calculated from equations that combined live weight and urea space were more highly correlated with directly measured empty body water than that calculated from equations derived only from urea space. Urea space correlations with body composition of our steers also were improved when live weight was included with urea space in multiple regression models. Results of this study suggest that before using any prediction equation for calculating body composition of cattle in vivo, equations should be tested with a sub-sample of cattle from the population for which its use is intended.     

The relationship between certain blood cations in cows with milk fever and both the state of consciousness and the position of cows when attended

In one study, a comparison was made of the concentrations and ratios of certain blood cations in 2 groups of cows with milk fever, one showing normal consciousness (n = 8) and the other depressed consciousness (n = 24). There were no significant differences in the mean concentrations of serum total calcium, plasma inorganic phosphorus and potassium, erythrocyte sodium and potassium, the serum calcium/serum magnesium ratio or the plasma sodium/erythrocyte sodium ratio. There were significant differences (all P less than 0.05) in the mean (+/- SD) concentrations of serum magnesium and plasma sodium concentrations, and the plasma sodium/serum magnesium ratio of 0.8 +/- 0.28 vs 1.2 +/- 0.37 mmol/l, 155 +/- 3.0 vs 147 +/- 6.4 mmol/l and 180 +/- 40.1 vs 116 +/- 34.1 for normal vs depressed cows, respectively. In a second study, a comparison was made of the concentrations and ratios of the same blood cations in 3 groups of cows in different positions when attended for milk fever, namely standing (n = 6), sternal recumbency (n = 24) and lateral recumbency (n = 31). There were no significant differences between the mean concentrations or ratios of any of the cations.     

Black soil blindness: A new mycotoxicosis of cattle grazing Corallocytostroma-infected Mitchell grass (Astrebla spp)

A new, fatal mycotoxicosis of cattle has been recognised in north-western Australia. A feeding trial confirmed the toxicity of a previously unknown species of Corallocytostroma that grows on Mitchell grass (Astrebla spp). The disease has been colloquially named ‘black soil blindness’ because its most prominent features are its confinement to pastures on black soil, and blindness and death of affected animals. Over 500 cattle have died and considerable subclinical disease is present. Above average wet season rainfall and extended growing seasons may explain the emergence of the fungus. The disease is important because cattle production in large areas of Australia utilise Mitchell grass pastures.