Effects on performance and carcass and meat quality attributes following immunocastration with the gonadotropin releasing factor vaccine Bopriva or surgical castration of Bos indicus bulls raised on pasture in Brazil.

Bos indicus bulls 20 months of age grazed on pasture in Minas Gerais, Brazil either received 2 doses of the GnRF vaccine Bopriva at d0 and d91 (group IC, n=144) or were surgically castrated on d91 (group SC, n=144). Slaughter on d280, was 27 weeks after castration. Adverse safety issues in 8% of group SC bulls following surgery contrasted with 0% in group IC bulls. At d105 testosterone levels were suppressed to similar levels in both groups. Importantly, group IC bulls had higher live weight, hot carcass weight, ADG (P<0.005) and dressing percentage (P<0.0001) compared to group SC animals. There were no negative effects on carcass or meat quality traits, thus immunocastration was concluded to offer a safe and effective method that provides production gains, and improves animal welfare in Bos indicus beef bulls without impacting meat and carcass quality.

A comparison of progestin-based protocols to synchronize ovulation and facilitate fixed-time artificial insemination in postpartum beef cows.

The experimental objective was to compare pregnancy rates after fixed-time AI in postpartum suckled beef cows following administration of two progestin-based protocols to synchronize ovulation. Cows (n = 424) at three locations (n = 208, 122, and 92 per location) were stratified by age, BCS, and days postpartum (DPP) and assigned randomly to one of the two treatment protocols. The MGA Select-treated cows (MGA Select; n = 213) were fed melengestrol acetate (MGA, 0.5 mg x cow(-1) x d(-1)) for 14 d and carrier for 8 d, and then GnRH (100 microg i.m. Cystorelin; d 26) was injected 12 d after MGA withdrawal, and PG (25 mg i.m. Lutalyse) was administered 7 d after GnRH. Cows assigned to the 7-11 Synch protocol (7-11 Synch; n = 209) were fed carrier for 15 d and MGA for 7 d, and then injected with PG on d 22 (d 7 of MGA), GnRH on d 26, and PG again on d 33. Artificial insemination was performed at fixed times for cows in both treatments at 60 or 72 h after d 33 PG for 7-11 Synch and MGA Select groups, respectively. All cows were injected with GnRH (100 microg of i.m. Cystorelin) at AI. There was no treatment x location interaction for age (P = 0.90), BCS (P = 0.64), or DPP (P = 0.93), and the results were therefore pooled for the respective treatments (age [7-11 Synch, 5.5 +/- 0.2; MGA Select, 5.5 +/- 0.2], BCS [7-11 Synch, 5.7 +/- 0.1; MGA Select, 5.6 +/- 0.1], and DPP [7-11 Synch, 41.1 +/- 1.1; MGA Select, 42.1 +/- 1.1]). Blood samples were collected 8 and 1 d before MGA or carrier to determine pretreatment estrous cyclicity (progesterone >or=1 ng/mL; 7-11 Synch, 59/209 [28%]; MGA Select, 54/213 [25%]; P = 0.50) and again on d 33 PG to evaluate treatment response as a percentage of cows with progesterone concentrations in serum >or=1ng/mL (7-11 Synch, 184/209 [88%]; MGA Select, 177/213 [83%]; P = 0.15). Pregnancy rates resulting from fixed-time AI did not differ (P = 0.25) between treatments (7-11 Synch, 128/209 [61%]; MGA Select, 142/213 [67%]), nor did pregnancy rates (P = 0.77) at the end of the breeding season (7-11 Synch, 198/208 [95%]; MGA Select, 204/213 [96%]). These data indicate that pregnancy rates were comparable after fixed-time AI, following administration of the 7-11 Synch and MGA Select protocols. Both protocols provide opportunities for beef producers to use AI and eliminate the need to detect estrus.

A comparison of progestin-based protocols to synchronize estrus in postpartum beef cows.

Two progestin-based protocols for estrus synchronization in postpartum beef cows were compared following treatment administration on the basis of estrous response, interval to and synchrony of estrus, and pregnancy. Cows were assigned to one of the two treatment protocols by age, body condition score (BCS), and days postpartum (DPP). The MGA Select-treated cows (MGA Select; n = 109) were fed melengestrol acetate (MGA; 0.5mg x cow-1 x d(-1)) for 14 d, fed carrier for 8 d, GnRH (100 microg of Cystorelin) was injected i.m. 12 d after MGA withdrawal, and PG (25 mg of Lutalyse) was administered i.m. 7 d after GnRH. Cows assigned to the 7-11 Synch protocol (7-11 Synch; n = 111) were fed carrier for 15 d, fed MGA for 7 d, injected with PG on d 22 (d 7 of MGA), injected with GnRH on d 26, and injected with PG on d 33. Mean BCS (4.8 +/- 0.1, MGA Select; 4.7 +/- 0.1, 7-11 Synch) and DPP (40 +/- 1, MGA Select; 40 +/- 1, 7-11 Synch) did not differ between treatments. Blood samples were collected 8 d and 1 d before feeding of MGA or carrier to determine the pretreatment estrous cyclicity (progesterone > or = 1 ng/mL; 10/109 [9%], MGA Select; 12/111 [11%], 7-11 Synch), and again at PG on d 33 to evaluate treatment response (81/109 [74%], MGA Select; 84/111 (76%), 7-11 Synch). Serum concentrations of progesterone at PG on d 33 differed (P < 0.01) between treatments (3.3 +/- 0.3 ng/mL [MGA Select] vs. 1.7 +/- 0.1 ng/mL [7-11 Synch]). HeatWatch was used for 6 d after PG on d 33 to detect estrus, and AI was performed 12 h after the onset of estrus. Estrous response did not differ between treatments (100/109 [92%], MGA Select; 101/111 [91%], 7-11 Synch). Mean interval to estrus (65 +/- 2.7 h, MGA Select; 52 +/- 1.8 h, 7-11 Synch) and synchrony of estrus differed (P < 0.01) between treatments. Synchronized conception and pregnancy rates (61/100 [61%], 61/109 [56%], MGA Select; 71/101 [70%], 71/111 [64%], 7-11 Synch), and final pregnancy rates (94/109 [86%], MGA Select; 99/110 [90%], 7-11 Synch) did not differ between treatments. In summary, estrous response and fertility did not differ among cows assigned to the MGA Select or 7-11 Synch protocols. Synchrony of estrus, defined as the variance in the interval to estrus from PG, however, was improved following treatment with the 7-11 Synch protocol.

Follicular dynamics and steroid profiles in cows during and after treatment with progestin-based protocols for synchronization of estrus.

Two progestin-based protocols for the synchronization of estrus in beef cows were compared. Cyclic, nonlactating, crossbred, beef cows were assigned by age and body condition score to one of two treatments. Cows assigned to the MGA Select protocol were fed melengestrol acetate (MGA; 0.5 mg x cow(-1) x (-1)) for 14 d, GnRH was administered (100 microg i.m. of Cystorelin) 12 d after MGA withdrawal, and PGF2alpha (25 mg of i.m. Lutalyse) was administered 7 d after GnRH. Cows assigned to the 7-11 Synch protocol were fed MGA for 7 d and were injected with PG on d 7 of MGA, GnRH on d 11, and PG on d 18. Transrectal ultrasonography was performed daily to monitor follicular dynamics from the beginning of MGA feeding through ovulation after the synchronized estrus. All cows exhibited estrus in response to PG. Mean interval to estrus was shorter (P < 0.01) for 7-11 Synch-treated cows (56 +/- 1.5 h) than for cows assigned to the MGA Select protocol (73 +/- 4.7 h). Mean interval from estrus to ovulation did not differ between treatments (P > 0.10). Variances for interval to estrus differed (P < 0.01) between treatments. Mean follicular diameter at GnRH injection, PG injection, and estrus did not differ (P > 0.10) between treatments. Relative to MGA Select, serum estradiol-17beta concentrations were higher (P < 0.01) for 7-11 Synch 2 d and 1 d before, on the day of GnRH injection, in addition to 4 d after GnRH, and 24 h after PG. Mean progesterone concentrations were greater (P < 0.01) for MGA Select cows from 4 d before to 7 d after GnRH. Forty-four percent of the variation in interval to estrus between treatments was explained by differences in estradiol-17beta concentrations 24 h after PG. This study suggests that follicular competence is likely related to steroidogenic capacity of the follicle and the endocrine environment under which growth and subsequent ovulation of the dominant follicle occurs.

Fixed-time artificial insemination of postpartum beef cows at 72 or 80 h after treatment with the MGA Select protocol.

The objective was to determine the appropriate timing of fixed-time artificial insemination (AI) following administration of the MGA Select protocol. Cows at two locations (Location 1, n=114; Location 2, n=97 ) were assigned to fixed-time AI at 72 or 80 h by age, body condition score (BCS), days postpartum (DPP), AI technician, and sire. All cows were synchronized with the MGA Select protocol, consisting of oral administration of melengestrol acetate (MGA; 0.5mg/hd per day) for 14 days, GnRH (Cysotrelin, 100 microg, i.m.; Day 26) 12 days after MGA withdrawal, followed in 7 days with PGF(2alpha) (PG; Lutalyse, 25mg i.m.; Day 33). Cows were inseminated at 72 h ( n=108 ) or 80 h ( n=103 ) after PG and GnRH (100 microg) was given at insemination. Location was not significant and, therefore, was removed from the model. Mean BCS ( 5.2+/-0.1, 72 h; 5.3+/-0.1, 80 h) and DPP ( 34+/-2, 72 h; 35+/-2, 80 h) did not differ ( P>0.1 ) between treatments. Serum progesterone concentrations 7 and 1 day prior to MGA were used to determine pre-treatment cyclicity: cows with at least one sample with progesterone > or =1 ng/ml were defined as cyclic (33/108, 31%, 72 h, versus 32/103, 31%, 80 h; P>0.1). Cows with serum progesterone concentrations > or =1 ng/ml on the day of PG were defined as responding to the synchronization protocol (74/108 (69%), 72 h versus 69/103 (67%), 80 h; P>0.1 ). Although pregnancy rates were higher ( P<0.05 ) for cows inseminated at 72 h (69/108, 64%) versus 80 h (52/103, 50%) after PG, pregnancy rates at the end of the breeding season did not differ ( P>0.1 ) between treatments (98/108 (91%), 72 h; 88/103 (85%), 80 h). In conclusion, pregnancy rates were higher when postpartum beef cows synchronized with the MGA Select protocol were inseminated at 72 h versus 80 h after PG.

Effects of a high polyunsaturated fat diet and vitamin E supplementation on high-density lipoprotein oxidation in humans.

Oxidative modification of high-density lipoproteins (HDL) impairs several biologic functions critical to its role in reverse cholesterol transport. We therefore investigated the effect of dietary polyunsaturated fat and vitamin E on the kinetics of HDL oxidation. Ten subjects were fed sequentially: a baseline diet in which the major fat source was olive oil; a high polyunsaturated fat diet in which the major fat source was safflower oil; and the safflower oil diet plus 800 I.U. vitamin E per day. Plasma lipoprotein levels, vitamin E content, fatty acid composition, and oxidation lag time and rate were determined after 3 weeks on each diet. The polyunsaturated fat diet increased the mean HDL(2) lag time from 45.8+/-12.5 to 83.3+/-11.6 min with no change in oxidation rate. Addition of vitamin E further increased the HDL(2) lag time to 115.6+/-4.4 min and decreased the HDL(2) oxidation rate 10-fold. Neither the polyunsaturated diet alone nor the diet with vitamin E supplementation had any effect on HDL(3) oxidation. We conclude that under conditions of controlled dietary fat intake, a high polyunsaturated fat intake does not increase the oxidation susceptibility of HDL subfractions, and that in this setting, vitamin E supplementation reduces the oxidation susceptibility of HDL(2). These data suggest that antioxidants could influence HDL function in vivo.

Pro-oxidant effect of vitamin E in cigarette smokers consuming a high polyunsaturated fat diet.

Dietary polyunsaturated fats and vitamin E are associated with reduced risk for atherosclerosis, but in smokers, they could promote lipid oxidation. Therefore, we examined the effects of a high polyunsaturated fat diet and vitamin E supplementation on measures of lipid oxidation in cigarette smokers. Ten subjects who smoked >1 pack of cigarettes per day were sequentially fed the following: a baseline diet in which the major fat source was olive oil, a diet in which the major fat source was high-linoleic safflower oil, and finally, the safflower oil diet plus 800 IU vitamin E per day. LDL oxidation lag time and rate and plasma total F(2)-isoprostanes and prostaglandin F(2alpha) (PGF(2alpha)) were determined after 3 weeks on each diet. The safflower oil diet increased total F(2)-isoprostanes from 53.0+/-7.2 to 116.2+/-11.2 nmol/L and PGF(2alpha) from 3.5+/-0.2 to 5.5+/-0.5 nmol/L, without changing LDL oxidation parameters. Addition of vitamin E prolonged mean LDL oxidation lag time but, paradoxically, further increased F(2)-isoprostanes to 188.2+/-10.9 nmol/L and PGF(2alpha) to 7.8+/-0.4 nmol/L. These data suggest that vitamin E may function as a pro-oxidant in cigarette smokers consuming a high polyunsaturated fat diet.

Gas chromatographic method using photoionization detection for the determination of breath pentane.

Lipid peroxidation is thought to be an important event in the pathogenesis of atherosclerosis. It has been suggested that pentane, which can be formed during the oxidation of omega-6 fatty acids, is a marker of lipid peroxidation. Previous studies have reported elevated breath pentane and serum markers of lipid peroxidation in smokers. However, chromatographic separation of pentane from isoprene in virtually all of these studies was incomplete and the methods used did not resolve pentane into its isomers, n-pentane and isopentane. Additionally, most current methods are complicated, requiring trapping and concentrating steps to obtain adequate sensitivity prior to hydrocarbon analysis. The purpose of the current study was to develop a gas chromatographic system to analyze breath pentane, that addresses the above technical problems and that would provide a simple in vivo method for measuring lipid. n-Pentane and isopentane standards were easily separated from isoprene with a Al2O3/KCI capillary column contained in a portable gas chromatograph equipped with a photoionization detector. The analysis of repeated measures showed a low coefficient of variation for measurements of n-pentane (10%) and isopentane (9%). We measured breath pentane in 27 subjects (15 smokers, 12 non-smokers). There were no significant difference between the baseline and 4 week interval measurements of n-pentane for smokers both before and after cigarette smoking. The within-subject variability data showed that the assay is highly reproducible for both low and high pentane levels in smokers. Smokers were found to have higher levels of both n-pentane and isopentane than non-smokers (P < 0.001). In addition, smokers had further significant elevation of pentane levels 10 min after smoking (P < 0.001), which returned to baseline by 1 h. These studies demonstrate that measurement of breath pentane, using a gas chromatograph with a photoionization detector, is simple and reproducible. Additionally, these results suggest that pentane elevation associated with smoking is secondary to the oxidant effects of cigarette smoke and an important temporal relationship exists between cigarette smoking and breath sample analysis.

A comparison of two tests for the assessment of blood pressure responses to sodium.

In order to assess the congruity of two different methods for the characterization of blood pressure responsivity to alterations in sodium and extracellular fluid volume balance, we studied 40 normotensive and hypertensive humans. All subjects were initially studied with a protocol of rapid sodium and volume expansion induced by intravenous administration of 0.9% saline (2 L over 4 h) followed by a day of sodium and volume depletion achieved by a low (10 mmol) sodium diet and three 40 mg oral doses of furosemide. Subsequently the subjects underwent a dietary protocol consisting of 5 days of a high (> or = 200 mmol/da) sodium diet followed by 7 days of a low (< or = 15 mmol/day) sodium diet. Blood pressure measurements as well as urinary sodium, potassium, and creatinine excretion measurements were made daily in both studies. A significant (P < .01) correlation was observed between the blood pressure responses to the separate techniques in the same individual. However, not all subjects responded in a similar qualitative fashion to the two maneuvers. The discrepancy was more frequent among subjects having a salt-resistant response to the rapid protocol. The renin response to sodium and volume depletion induced by the low sodium diet and furosemide correlated significantly (P < .001) with the subsequent blood pressure response to the low sodium diet. Subjects defined as salt-sensitive differed from the salt-resistant group by more sluggish renal adaptation to dietary sodium restriction. These findings demonstrate the congruity of two different approaches for the assessment of salt responsivity of blood pressure in humans.(ABSTRACT TRUNCATED AT 250 WORDS)