Effect of feeding wet distillers grains on performance, marbling deposition, and fatty acid content of beef from steers fed low- or high-forage diets.

One hundred thirty-eight Angus cross yearling steers (initial BW 390 ± 0.5 kg) were allotted by BW to a 3 × 2 factorial arrangement of 6 treatments (4 pens per treatment) to determine the effect of wet distillers grains (WDG) concentration (0, 20, 40% of dietary DM) in low-forage (12% hay) and high-forage (50% hay) diets on growth performance and marbling. Steers were implanted on d 0 with Component TE-S (VetLife, Overland Park, KS) and were slaughtered in 3 groups when final BW averaged 578 kg. Steers fed a low-forage diet gained BW faster (P < 0.001) than did steers fed a high-forage diet; the amount of WDG fed did not affect (P = 0.25) daily BW gain. Hot carcass weight and dressing percentage were greater (P < 0.001) for steers fed low-forage diets than for steers fed high-forage diets. Dressing percentage increased (P = 0.08) as WDG concentration increased. Longissimus muscle area (P = 0.08) and yield grade (P < 0.01) were greater for steers fed low-forage diets compared with steers fed high-forage diets. Longissimus muscle area (P = 0.02) and yield grade (P = 0.03) increased as WDG concentration increased. An interaction occurred for marbling (P < 0.01), fat thickness (P = 0.08), and PUFA content (P < 0.01). In steers fed low-forage diets, marbling score (325, 306, 265) and fat thickness (1.22, 1.07, 1.07 cm) decreased with WDG inclusion rates of 0, 20, and 40%, respectively, but in steers fed high-forage diets, marbling score (249, 282, 262) and fat thickness (0.89, 0.97, 0.81 cm) increased from the 0 to 20% inclusion rate and then decreased from the 20 to 40% inclusion rate. The inclusion of 0, 20, or 40% WDG increased PUFA content of beef from steers fed low-forage diets (6.9, 9.3, 10.6 g/100 g) but decreased PUFA content of beef from the 0 to 20% inclusion rate and then increased PUFA content of beef from the 20 to 40% inclusion rate in steers fed high-forage diets (8.5, 5.9, 7.8 g/100 g). In conclusion, when fed to a common BW end point, concentration of WDG in feedlot diets alters lean and adipose tissue deposition in beef cattle.

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)2 D3) 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 x 10(6) IU 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-microg 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 < 0.01) the concentration of vitamin D3 and 25-OH D3 in all muscles sampled. Feeding steers 25-OH D3 increased (P < 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 < 0.10) shear force values; however, there was a trend (P < 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 < 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 < 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.

Short-term feeding of vitamin D3 improves color but does not change tenderness of pork-loin chops.

The objective of this study was to determine the effect of short-term feeding of vitamin D3 (D3) on blood plasma calcium concentrations and meat quality of pork-loin chops. Three experiments were carried out to meet this objective. Experiment 1 used 250,000 IU and 500,000 IU/d to determine the effective dose of dietary D3 to raise blood plasma calcium concentration. Experiment 2 used 500,000 IU D3/d to determine the appropriate length of feeding time to elevate blood plasma calcium prior to harvest. Experiment 3 used 500,000 IU D3/d to determine the effectiveness of increased blood plasma calcium in improving postmortem quality and tenderness of pork-loin chops. Pigs fed 500,000 IU D3/d in Exp. 1 exhibited higher (P < 0.05) and more stable plasma calcium concentration over a 14-d feeding trial compared with pigs fed 250,000 IU D3/d and control pigs. Therefore, 500,000 IU D3/d was the dose chosen for Exp. 2, in which pigs fed 500,000 IU D3/d for 3 d prior to harvest exhibited elevated and stable plasma calcium concentrations; this length of time was deemed sufficient in which to observe differences in postmortem meat tenderness in Exp. 3. Vitamin D3 supplementation resulted in lower (P < 0.02) L* values and higher (P < 0.03) a* values of loin chops at 7 and 14 d of shelf storage. Vitamin D3 supplementation did not affect quality characteristics (measured by use of subjective scores) or tenderness (quantified via Warner-Bratzler shear force or Star probe values). On the basis of these findings, feeding 500,000 IU D3/d to finishing pigs improved most Hunter color values at 14 d of storage but did not improve pork-loin chop tenderness at 1 to 21 d of retail shelf storage.

The use of vitamin D3 to improve beef tenderness.

An experiment was designed to test the hypothesis that short-term oral administration of dietary vitamin D3 to beef cattle before slaughter would increase beef tenderness through greater calcium-activated calpain activity in postmortem aged skeletal muscle. Thirty continental crossbred steers were allotted randomly to three treatment groups housed in one pen. One group served as a control; two other groups were administered boluses with either 5 x 10(6) or 7.5 x 10(6) IU of vitamin D3 daily for 9 d. Cattle were slaughtered 1 d later. The longissimus lumborum was excised from each carcass 72 h postmortem and steaks removed at 3, 7, 14, and 21 d postmortem. The semimembranosus muscle (top round) was excised from each carcass 72 h postmortem and steaks removed at 7, 14, and 21 d postmortem. Blood plasma calcium concentration of cattle treated with 5 or 7.5 x 10(6) IU of vitamin D3 was higher (P < .05) than that of controls. Strip loin and top loin steaks from cattle fed supplemental doses of vitamin D3 had lower (P < .05) Warner-Bratzler (W-B) shear values at 14 d postmortem but were not significantly different from controls at 3, 7, or 21 d (strip loins) or 7 or 21 d (top rounds). No significant difference in strip loin steak tenderness was observed by sensory panel at 14 d postmortem (P < .17) between steaks from control and vitamin D3-treated steers. At 14 d postmortem, strip loin and top round steaks from cattle fed 5 x 10(6) IU of vitamin D3, but not from those given 7.5 x 10(6) IU, showed more proteolysis (P < .05) than did steaks from control cattle, based on Western blotting analysis. Therefore, the use of supplemental dietary vitamin D3 given daily for 9 d before slaughter did improve tenderness (lower W-B shear values) of 14-d postmortem aged beef. Increased proteolysis seems to be the mechanism of tenderization.

Pregnancy, parturition, and lactation in hypophyseal stalk-transected beef heifers.

Progesterone secretion is crucial for maintaining pregnancy to parturition in mammalian species, and in cattle the corpus luteum is the primary source of this hormone. This study determined the roles of prolactin (PRL), growth hormone (GH) and luteinizing hormone (LH) in the luteotropic process in beef heifers hypophyseal stalk-transected (HST, n=7) or sham operated (sham operated controls, SOC, n=9) during midgestation. The main finding was that endogenous PRL and GH maintained progesterone secretion in HST heifers in a similar manner to that in SOC throughout pregnancy. Serum PRL averaged 37 vs 187 and GH 2 vs 4 ng/ml in HST heifers compared with SOC, whereas LH abruptly decreased to undetectable levels after HST compared with a modest 0.4 ng/ml in SOC heifers. The second finding was that parturition and lactation occurred in HST heifers with calf delivery induced to occur at the same time as SOC. Milk production in HST animals was severely limited, and postpartum estrus obliterated compared with SOC. The suckling stimulus sustained milk ejection in HST heifers in spite of diminished PRL, GH, thyroid stimulating hormone, thyroxine and tri-iodothyronine secretion. The results suggest that PRL, GH and possibly placental lactogen are luteotropic during pregnancy in cattle.

Long-term growth after hypophyseal stalk transection and hypophysectomy of beef calves.

Hypothalamic hormones regulate episodic and basal secretion of hormones from the anterior pituitary gland that affect metabolism and growth in cattle. This study focused on long-term growth in young calves subjected to hypophysectomy (HYPOX), hypophyseal stalk transection (HST), and sham operation control (SOC). Cross-bred (Hereford x Aberdeen Angus) and Hereford, and Aberdeen Angus calves were HYPOX (n = 5), HST (n = 5), or SOC (n = 8) at 146 +/- 2 days of age, whereas another group was HST (n = 5) or SOC (n = 7) at 273 +/- 5 days of age. Body weight was determined every 21 days from birth to 1008 days of age. Anterior vena cava blood was withdrawn at 4-day intervals from day 64-360 for RIA of GH, TSH, T4, T3, and LH, and at 20-min intervals for 480 min to determine episodic hormone secretion. Daily feed intake was determined in HST and SOC calves during an 80-day period. Birth weight averaged 35 +/- 1 kg (+/- SE) and was 142 +/- 4 kg at 126 days and 208 +/- 8 kg at 252 days before surgery. From day 146-1008, growth was arrested (P < 0.001) in HYPOX (0.06 +/- 0.01 kg/day) compared with SOC (0.50 +/- 0.04 kg/day) calves. Growth continued but at a significantly lower rate (P < 0.05) in calves HST at 146 days (0.32 +/- 0.07 kg/day) and 273 days (0.32 +/- 0.06 kg/day) compared with SOC (0.50 +/- 0.09 kg/day). Growth continued to be impaired to 1008 days, but more so in those HST at 146 days (432 +/- 43 kg BW) than 273 days (472 +/- 5 kg BW) and less (P < 0.05) than SOC (586 +/- 37 kg BW). Daily feed intake was consistently less (P < 0.05) in HST compared with SOC calves. Although episodic GH secretion was abolished and peripheral serum GH concentration remained consistently lower in HST (2.4 ng/ml) than SOC (5.5 ng/ml; P < 0.01), the calves continued to grow throughout 1008 days. Peripheral serum TSH concentration was less (P < 0.05) HST compared with SOC calves. There was an abrupt decrease (P < 0.001) in serum T4 (4-fold) and T3 (3-fold) concentration after surgery that remained to 360 days in HST compared with SOC calves. At the time calves were killed, pituitary gland weight was markedly reduced (P < 0.001) in HST (0.18 +/- 0.01 g/100 kg BW) compared with SOC (0.54 +/- 0.03 g/100 kg BW). Histological examination of pituitary glands from HST calves indicated the persistence of secretory GH and TSH cells in the same areas of the adenohypophysis as SOC calves. Coronal sections of the gland stained with performic acid-Alcian blue-periodic acid-Schiff-orange G, revealed GH and TSH secreting cells in HST calves similar to controls. These results indicate that long-term growth continues, but at a slower rate, after hypophyseal stalk transection of immature calves in spite of complete abolition of episodic GH secretion and consistently decreased basal secretion of GH, TSH, T4, and T3 compared with sham-operated animals. Growth was abolished after hypophysectomy of immature calves in which circulating GH and TSH was undetectable.

Growth hormone concentrations in plasma of healthy pigs and pigs with atrophic rhinitis.

Plasma concentrations of porcine growth hormone (PGH) were similar in healthy pigs and those with atrophic rhinitis (AR), therefore, observed reduced growth rates and feed efficiency in naturally infected pigs with AR were not attributed to low concentrations of plasma PGH. Also, pituitary glands in both groups of pigs were responsive to growth hormone-releasing hormone (GHRH) challenge by increasing PGH secretion. Administration of clonidine hydrochloride to pigs naturally infected with AR failed to elicit any significant change (5.3 +/- 1.4 ng/ml) in the plasma concentration of PGH within a 45-minute bleeding interval. The pretreatment concentrations of PGH were similar in specific-pathogen-free toxin-treated and specific-pathogen-free control groups, but they increased significantly in toxin-treated pigs (20.7 +/- 8.2 ng/ml) within 15 minutes after GHRH injection. Porcine growth hormone release in toxin-treated pigs was variable; however, all pigs did not respond to GHRH administration: 3 responded with an increase in PGH release (35.6 +/- 10.6 ng/ml), 2 did not respond (6.7 +/- 0.5 ng/ml), and 1 had a decrease in PGH release (3.9 ng/ml). Therefore, the observed reduced growth rates reported in the literature may be attributed to factors at the target level of PGH action, such as insufficient or down-regulation of PGH receptors, changes or impaired ability in the PGH receptor-binding characteristics, and inability of PGH receptor complex to transduce signal. Toxins are known to modulate signal transduction pathways. It has been speculated that serotype-D Pasteurella multocida toxin may influence growth by its effect on signal transduction from PGH receptor complex on the cell membrane to the interior of the cell.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in hormone and metabolite concentrations in plasma of steers during a prolonged fast.

Two Brown Swiss and two Holstein steers, average weight of 226 kg, were fasted 8 d. Two days before the fast, jugular vein catheters were installed. Blood samples were collected every 15 min from 0800 to 1400 h on d 0, 2, 5 and 8 of fasting. Plasma from each sample was analyzed for concentrations of growth hormone, and from selected samples for insulin, glucagon, glucose, beta-hydroxybutyrate, free fatty acids, urea N and glycerol. Both growth hormone and insulin concentrations decreased by d 2 of the fast and remained at that concentration. Glucagon, however, remained constant. From d 0 to 2, concentrations of beta-hydroxybutyrate, free fatty acids and glycerol increased but then changed little for d 5 and 8. From d 0 to 2, glucose decreased and urea N increased. In contrast to the other metabolites, glucose and urea N concentrations stabilized between 3 and 5 d of fasting. The ratio of growth hormone to insulin decreased threefold and the ratio of glucagon to insulin decreased fivefold from d 0 to 2; both ratios remained constant during the rest of the fast. The data indicate that fasting cattle adapt by decreasing concentrations in plasma of growth hormone and insulin but not glucagon. These endocrine changes, therefore, seem responsible for greater rates of free fatty acid mobilization and glucose sparing during an energy deficit.

Effects of in vitro ronnel on metabolic activity in subcutaneous adipose tissue and skeletal muscle from steers.

Ronnel [0,0-dimethyl 0-(2,4,5-trichlorophenyl) phosphorothioate] is an organophosphate pesticide with growth-promoting properties. Experiments were conducted to determine effects of ronnel on oxidation of and fatty acid synthesis from acetate and glucose as indices of metabolic activity in subcutaneous adipose tissue and skeletal muscle from 6-, 12- and 18-mo-old steers. Ronnel depressed metabolic activity in adipose tissue from 6- and 12-mo-old steers without concomitantly decreasing metabolic activity in skeletal muscle. Production of CO2 and fatty acids from acetate and glucose in tissues from 18-mo-old steers was influenced less by ronnel than in tissues from younger steers. Interactions of ronnel with thyroxine or growth hormone on acetate oxidation and conversion to fatty acids in adipose tissue also were investigated. Thyroxine increased acetate oxidation and decreased fatty acid synthesis. Ronnel interfered with the metabolic effects of thyroxine. Growth hormone, with or without ronnel, did not affect metabolic activity of adipose tissue. Ronnel seemingly alters the partitioning of acetate and glucose between major metabolic processes in adipose tissue and skeletal muscle.

Insulin binding on cultured chick muscle cells: decrease in binding associated with cell fusion.

Binding of 125I-bovine and chicken insulin to cultured embryonic chick skeletal muscle cells was studied. Bovine and chicken insulin bound cultured cells with high affinities of 2.4 X 10(9)M-1 and 4.8 X 10(9)M-1 and low affinities of 2.4 X 10(7)M-1 and 3.7 X 10(7)M-1, respectively. Maximum insulin binding was achieved after 90 min of incubation at 20 degrees C and the maximum value was maintained for an additional 3 hr. Insulin binding increased in a linear manner with increasing nuclei number over a 5-fold range. Maximum insulin binding per nuclei decreased as cell fusion increased between 24 and 72 hr in culture, primarily due to a decrease in the number of low affinity insulin receptors.

Growth and differentiation of chicken embryo muscle cell cultures derived from fast- and slow-growing lines. Intrinsic differences in growth characteristics and insulin response.

Primary myogenic cell cultures derived from 12-day embryos of genetically fast-growing chickens (fast cultures) and slow-growing chickens (slow cultures) were grown under identical conditions to examine differences in growth and differentiation at the cellular level. The two types of cultures exhibited significant (P less than 0.01) differences in proliferation, protein accumulation, response to the addition of insulin to the culture medium and the amount of insulin bound per nucleus. The fast cultures exhibited a larger number of both total nuclei and fused nuclei at 48, 72 and 96 h in culture, accumulated more protein per nucleus at 24, 48 and 72 h in culture and demonstrated a greater response to the addition of insulin to the culture medium, as reflected by increased fusion rate and protein accumulation at 24 h in culture. Maximal response to insulin in both types of cultures was obtained at 24 h to added insulin concentrations of 10(-10)-10(-9) M. Slow cultures bound more [125I]-insulin than fast cultures at 24 h in culture. These experiments suggest that different muscle growth potentials in animals of the same species are at least partly due to intrinsic cellular differences in the myogenic cells that give rise to adult muscle tissue.