Adolescent Pregnancy

More than 14 million adolescents in the world annually give birth, and nearly 800,000 adolescents in the United States become pregnant each year. This chapter considers concepts of teen pregnancy including risks to the mother as well as offspring, the adolescent father, issues related to abortion, and concepts of prevention of unwanted pregnancy in youth. Adolescent pregnancy is global phenomenon affecting all societies and cultures

The use of vitamin D3 and its metabolites to improve beef tenderness

Three experiments were conducted to determine whether feeding 25-hydroxyvitamin D3 (25-OH D3) or 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) improves the tenderness of longissimus dorsi (LD), semimembranosus (SM), and infraspinatus (IF) muscles similar to supplemental vitamin D3 without leaving residual vitamin D3 and its metabolites in muscle. In the first two experiments, 24 crossbred steers were used to determine the effects of different oral amounts of 1,25-(OH)2 D3 (Exp. 1; n = 12) and 25-OH D3 (Exp. 2; n = 12) on plasma Ca2+concentrations. In the third experiment, crossbred steers were allotted randomly to one of four treatments: 1) control placebo (n = 7); 2) 5 × 106IU of vitamin D3/d (n = 9) for 9 d and harvested 2 d after last treatment; 3) single, 125-mg dose of 25-OH D3 (n = 8) 4 d before harvest; or 4) single, 500-μg dose of 1,25-(OH)2 D3 (n = 9) 3 d before harvest. The LD and SM steaks from each animal were aged for 8, 14, or 21 d, whereas steaks from the IF were aged for 14 or 21 d. All steaks were analyzed for tenderness by Warner-Bratzler shear force and for troponin-T degradation by Western blot analysis. Supplementing steers with vitamin D3 increased (P \u3c 0.01) the concentration of vitamin D3 and 25-OH D3 in all muscles sampled. Feeding steers 25-OH D3 increased (P \u3c 0.05) the concentration of 25-OH D3 in meat, but to an amount less than half that of cattle treated with vitamin D3. Supplemental 1,25-(OH)2 D3 did not affect (P \u3c 0.10) shear force values; however, there was a trend (P \u3c 0.10) for supplemental vitamin D3 and 25-OH D3 to produce LD steaks with lower shear values after 8 and 14 d of aging, and lower (P \u3c 0.10) shear force values for the SM aged for 21 d. Analysis of Western blots indicated that LD steaks from cattle supplemented with vitamin D3 and 25-OH D3 had greater (P \u3c 0.05) troponin-T degradation. Antemortem supplementation of 25-OH D3 seems to increase postmortem proteolysis and tenderness in the LD and SM without depositing large concentrations of residual vitamin D3 and its metabolite 25-OH D3

Use of 25-hydroxyvitamin D3 to Improve Tenderness of Beef

Tenderness is one of the most important quality characteristics of beef to both consumers and producers. To date, no practical method of producing consistently tender beef has been adopted by the beef industry. Researchers have demonstrated that feeding a supernatural dosage (0.5 to 7.5 million IU) of vitamin D3 to beef cattle for 7 to 10 days before slaughter will result in more tender carcasses (Swanek et al., 1999; Montgomery et al., 2000; Montgomery et al., 2002; Karges et al., 2001). Feeding this amount of vitamin D3 results in elevated plasma and muscle calcium concentrations (Swanek et al., 1999; Montgomery et al., 2000; Montgomery et al., 2002; Karges et al., 2001). The assumed mechanism for this tenderization effect is that the elevated muscle calcium concentration enhances the action of the calcium-dependent protease system of myofibrillar (troponin-T) protein degradation postmortem. Enhanced myofibrillar protein degradation results in more tender beef that is more desirable to consumers. For producers, being able to produce a “guaranteed tender” product even may warrant a price premium

Use of Vitamin D3 and its Metabolites to Improve Beef Tenderness

Our previous work has shown that feeding 5 million international units (IU) of vitamin D3 to beef steers can produce tender strip loin and top round steaks. Our current experiment was designed to determine whether feeding two metabolites of vitamin D3, 25- hydroxyvitamin D3, and 1,25-dihysroxyvitamin D3, produces tender strip loin, top round, and top blade steaks more effectively than does supplemental vitamin D3 without leaving a substantial amount of residual vitamin D3 in muscle. Thirty-three continental crossbred steers were randomly allotted to one of four treatment groups. The first group was fed a placebo. The second group received 5 million IU of vitamin D3 each day for nine days and was slaughtered two days later. The third group received one dose of 125 mg of 25-hydroxyvitamin D3 four days before harvest, and the fourth group received one dose of 500 mg of 1,25- dihydroxyvitamin D3 three days before harvest. Blood samples were collected before treatment and at the time of slaughter for subsequent analysis of calcium, vitamin D3, 25-hydroxyvitamin D3, and 1,25-dihydroxyvitamin D3 concentrations in plasma. Steaks from the longissimus lumborum (strip loin) and semimembranous (top round) muscles were collected from each animal and aged for 8, 14, and 21 days, and steaks from the infraspinatus were collected and aged for 14 and 21 days. All steaks were analyzed for tenderness by Warner-Bratzler shear force determination. Concentrations of vitamin D3 in plasma were higher in vitamin D3- treated cattle (P \u3c 0.0001). Concentrations of plasma 25-hydroxyvitamin D3 were increased in 25- hydroxyvitamin D3-treated cattle, but not as high as vitamin D3-treated cattle (P \u3c 0.0001). 1,25- Dihydroxyvitamin D3 concentrations were higher in 1,25-dihydroxyvitamin D3-treated animals compared with all treatments (P \u3c 0.0001). Supplementing steers with vitamin D3 increased the concentration of vitamin D3 and 25-hydroxyvitamin D3 in the meat of all muscles sampled (P \u3c 0.0001). Supplementing steers with 25-hydroxyvitamin D3 increased the concentration of 25-hydroxyvitamin D3 in meat, but to an amount less than half that of cattle treated with vitamin D3. Warner-Bratzler shear force analysis showed that feeding 1,25- dihydroxyvitamin D3 did not significantly lower shear force values, but supplemental vitamin D3 and 25-hydroxyvitamin D3 produced longissimus lumborum and semimembranous steaks with lower shear force values (P \u3c 0.06). Analysis of Western blots showed that longissimus lumborum and semimembranous steaks from cattle fed supplemental vitamin D3 and 25-hydroxyvitamin D3 (but not steaks from cattle fed 1,25- dihydroxyvitamin D3), had greater proteolysis of troponin T to a 30 kDa component

Use of 25-hydroxyvitamin D3 and vitamin E to improve tenderness of beef from the longissimus dorsi of heifers

The objective of this trial was to determine whether a single bolus of 25-hydroxyvitamin D3 (25-OH D3), vitamin E, or a combination of the 2 would improve the tenderness of steaks from the LM of beef heifers. Forty-eight Angus crossbred heifers were allotted randomly to 8 pens. Six heifers were in each pen, and there were 2 pens per treatment. The 4 treatments included control (no 25-OH D3 or vitamin E); 25-OH D3 (500 mg of 25-OH D3 administered as a one-time oral bolus 7 d before slaughter); vitamin E (1,000 IU of vitamin E administered daily as a top-dress for 104 d before slaughter); or combination (500 mg of 25-OH D3administered as a one-time oral bolus 7 d before slaughter and 1,000 IU of vitamin E administered daily as a top-dress for 104 d before slaughter). Blood samples were obtained on the day that heifers were allotted to treatments, on the day 25-OH D3 was administered, and on the day before slaughter. Plasma calcium concentration was increased when 25-OH D3 was administered with or without vitamin E (P \u3c 0.007). In LM, calcium concentration tended to increase (P = 0.10) when 25-OH D3 was administered alone but not when 25-OH D3 was administered with vitamin E. Concentrations of 25-OH D3 and 1,25-dihydroxyvitamin D3 in plasma were increased when 25-OH D3 was administered with or without vitamin E (P \u3c 0.001). Steaks from heifers treated with 25-OH D3or vitamin E, but not both, tended to have lower Warner-Bratzler shear force than steaks in the control group at 14 d postmortem (P = 0.08). Postmortem protein degradation as measured by Western blot of the 30-kDa degradation product of troponin-T was increased with all treatments after 3 d postmortem (P ≤ 0.07), but not at 7 or 14 d postmortem. Unexpectedly, the use of 500 mg of 25-OH D3 fed as an oral bolus 7 d before slaughter or 1,000 IU of vitamin E administered daily for 104 d before slaughter alone, but not in combination, effectively decreased Warner-Bratzler shear force

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 D3(25-OH D3) 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 × 3 factorial design with 3 dosages of 25-OH D3 (0, 250, or 500 mg of 25-OH D3 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 D3 were administered (P ≤ 0.05). Calcium concentrations in muscle increased (P ≤ 0.001) when 500 mg of 25-OH D3 were administered. Concentrations of 25-OH D3 in meat and in plasma and 1,25-dihydroxyvitamin D3 [1,25-(OH)2 D3] in plasma were increased when 25-OH D3 was administered (P≤ 0.05). The percentage of limestone replenished in the diet had no effect on 25-OH D3 or 1,25-(OH)2 D3 in meat or in plasma. Calpastatin activity was affected by treatments only in the gracilus and vastus intermedius muscles (P ≤ 0.05). Among all muscles and aging periods, calpastatin activity and intensity of troponin-T degradation product were related inversely. Results indicate that supplemental 25-OH D3 has some influence on muscle characteristics known to improve tenderness, but improved tenderness was not observed

Use of 25-Hydroxyvitamin D3 to Improve Beef Tenderness

Feeding the 25-hydroxyvitamin D3 (25-OH D3) metabolite of vitamin D3 has been reported to improve beef tenderness and result in lower vitamin D3 metabolite concentrations in meat. Because 25-OH D3 remains elevated in plasma for at least 8 d subsequent to feeding, we believe that 25-OH D3 can be fed as a one-time oral bolus and allow a flexible time frame for harvest with the same improvement in postmortem calcium-dependent proteolysis and beef tenderness. To test this hypothesis, 108 crossbred steers were allotted, six steers per pen to 18 pens and treatments were assigned randomly to pen. Treatments were 25-OH D3 dosage (62.5 or 125 mg) and time of administration of the one-time oral bolus (4, 7, 21, or 35 d before harvest). Control steers received no 25-OH D3. Regardless of time of bolusing relative to harvest, the one-time oral bolus elevated plasma 25-OH D3 concentration and it remained elevated through harvest for steers assigned to either dosages of 25-OHD3. Plasma calcium concentration, however, remained unchanged compared with that of controls, regardless of dosage or time of bolusing relative to harvest. The one-time oral bolus of 25-OH D3 did not result in an improvement in tenderness as determined by Warner-Bratzler shear force or an improvement postmortem proteolysis as determined by troponin-T degradation. We conclude that a one-time oral bolus of 62.5 or 125 mg of 25-OH D3 was sufficient to elevate plasma 25-OH D3 concentration and maintain an elevated plasma 25-OH D3 concentration for up to 35 d. The dosage of 25-OH D3, however, was insufficient to result in elevated plasma calcium and therefore did not enhance calcium-dependent proteolysis postmortem to result in beef that is more tender

Comparison of Gain and Carcass Traits from Pasture- and Feedlot-Finished Beef Steers Supplemented with Distillers Grain Co-Products

As the ethanol and renewable fuel industries grow, the availability of distillers grains and other co-products continues to increase. These co-products are valuable feedstuffs for ruminants because of their high protein content and also their high fiber content. However, as more acres are dedicated to corn production, less pasture will be available for grazing livestock and less corn may be available for use as feed. As such,supplementing pasture-fed cattle with distillers grains may be an option for some producers to utilize. Therefore, the objective of this research was to evaluate pasture-finishing steers with supplementation of a distillers co-product

Fatty Acid Profiles and Content of Pasture- and Feedlot-Finished Beef Steers Supplemented with 25-Hydroxyvitamin D3 Prior to Harvest

Pasture- and feedlot-finished beef steers (n = 48) were supplemented with 25-hydroxyvitamin D3 (25-OH D3) on d 7 prior to harvest. The longissimus (LM), semimembranosus (SM), and gracilis (GR) muscles were collected after harvest for evaluation of lipid percentage, fatty acid profiles, and fatty acid content. Lipid percentages did not differ between pasture- and feedlot-finished steers. Muscles, however, did differ in lipid percentage with the GR having the least lipid followed by the SM and LM. Fatty acid profiles differed as a result of dietary treatment and also were different among muscles. Monounsaturated fatty acids (MUFA) were greater in steaks from feedlotfinished steers than pasture-finished steers. Polyunsaturated fatty acids (PUFA) were greatest in the GR muscle as compared with the LM and SM. Conjugated linoleic acid (CLA) was greater in the longissimus and semimembranosus of pasture-finished steers than other muscles and feedlot-finished steers. Concentrations of C18:3n3 were also greater in the LM of pasture-finished steers. Data for fatty acid content were similar to those for fatty acid profiles, indicating that 100 g of tissue would contain 14 mg of CLA and that the LM had the greatest total content of saturated fatty acids (SFA), MUFA, and PUFA