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1.
Two digestion and metabolism experiments were conducted to determine effects of monensin in low-protein diets. Monensin supplementation (27 mg/kg of diet dry matter) of steers (303 kg) fed 8.7% crude protein increased (P less than .01) apparent N digestibility and N retention and decreased (P less than .01) percentage of N apparently absorbed lost in urine. Apparent digestibilities of dry matter, gross energy and acid detergent lignin were increased (P less than .05). Digestibilities of neutral detergent and acid detergent fibers were not affected by monensin. In growing wether goats (15 kg) fed 8.5% crude protein, monensin (23 mg/kg of diet dry matter) improved (P less than .01) apparent N digestibility and apparent N absorption. However, urinary N excretion also increased (P less than .05), resulting in no difference in N retention. Monensin did not affect digestibilities of dry matter or gross energy. Efficiency of feed conversion and average daily gain were improved with monensin supplementation of growing goats fed a low-protein, high-roughage diet. Monensin resulted in typical shift of acetate-to-propionate ratio in both experiments. Results suggest that improved N utilization may account for some benefits of feeding monensin.  相似文献   

2.
Two comparative slaughter trials and a metabolism trial were conducted. Treatments consisted of: 1) 0 fat, 0 monensin; 2) 4% yellow grease, 0 monensin; 3) 0 fat, 33 mg/kg monensin and 4) 4% yellow grease, 33 mg/kg monensin. Trial 1 involved 104 crossbred beef steers (267 kg) in a 140-d comparative slaughter trial. There were no interactions (P greater than .20) between supplemental fat and monensin on steer performance. Monensin supplementation decreased rate of weight gain (P less than .10) and feed intake (P less than .05) with no effect on energy value of the diet (P greater than .20). Fat supplementation increased (P less than .01) rate of weight gain 12.5% and increased the net energy for maintenance (NEm) and net energy for gain (NEg) value of the diet 8.5 and 9.4%, respectively. Trial 2 involved 154 Holstein steers (290 kg) in a 94-d comparative slaughter trial. There were no interactions between supplemental fat and monensin (P greater than .20). Monensin supplementation did not affect rate or composition of gain (P greater than .20), but supplementation reduced (P less than .05) feed intake and feed required per unit weight gain 3.6%. Fat supplementation increased (P less than .01) fat and energy gain 12.5 and 10.3%, respectively, and the NEm and NEg content of the diet 7.5 and 8.4%, respectively. Trial 3 utilized four crossbred beef steers (220 kg) with cannulas in the rumen, proximal duodenum and distal ileum. There were no interactions between supplemental fat and monensin with respect to site of digestion (P greater than .20). Supplemental fat did not affect (P greater than .20) organic matter, starch, fiber or N digestion. Intestinal digestibility of fat averaged 77.3%. Monensin increased (P less than .10) intestinal digestibility of fat 7.4%. There were negative associative effects between supplemental fat and monensin on ruminal acetate:propionate ratios and estimated methane production. It was concluded that the feeding value of feed fat is underestimated in tables of feed standards currently in use, and that the net effects of monensin on these estimates are additive.  相似文献   

3.
Sixty-four Angus steers initially averaging 354 kg were allotted to a 2 X 2 factorial arrangement of treatments to determine the effects of dietary Ni (0 or 5 mg/kg supplemental), monensin (0 or 33 mg/kg) and their possible interaction on performance, methane production and N metabolism. The basal diet was a high energy, corn-cottonseed hull based diet containing 10.2% crude protein and .30 mg/kg Ni on a dry matter basis. Monensin reduced (P less than .05) feed intake, did not affect average daily gain and improved (P less than .05) feed conversion over the 102-d study. Nickel supplementation did not significantly alter or interact with monensin to affect steer performance. However, steers fed Ni tended to have higher average daily gains and improved feed conversions. Monensin decreased (P less than .05) in vitro methane production, altered several carcass traits, increased (P less than .05) molar proportion of ruminal propionate and decreased (P less than .05) molar proportion of ruminal acetate. Nickel did not alter methane production, carcass characteristics or ruminal volatile fatty acid proportions. Both monensin and Ni increased (P less than .05) ruminal fluid urease activity when samples were obtained before feeding. A significant monensin X Ni interaction was found to affect ruminal epithelial urease activity. Monensin increased ruminal epithelial urease in steers not receiving supplemental Ni, but had no effect on ruminal epithelial urease activity in steers fed supplemental Ni. Ruminal fluid protein and ammonia-N were decreased (P less than .05) by monensin. Results of this study indicate that Ni may interact with monensin to affect ruminal epithelial urease activity but not performance or methane production in finishing steers.  相似文献   

4.
Four hundred and thirty-two Spanish Giant rabbits were fed 12 diets of variable energy to protein ratio [kcal digestible energy (DE)/g digestible crude protein (DCP)] from weaning to slaughter, both at different ages and weights. Body composition analysis for various chemical components indicated that body weight accounted for the greatest part of the variation in these constituents. Sex influenced only the N content (P less than .05). Dietary E/P accounted for greater variability in body composition than crude protein or crude fiber content of the diet. High dietary E/P increased (P less than .001) the proportion of body fat and reduced the proportion of body protein. This effect was made more obvious by adjustment to equal rate of weight gain and it showed that there may be a greater influence of dietary E/P on body composition than previously recognized.  相似文献   

5.
Influence of monensin on the performance of cattle   总被引：13，自引：0，他引：13  
Performance data on nearly 16,000 head of cattle that were used in trials to document effects of monensin on feedlot cattle were summarized. Cattle fed monensin-containing diets gained 1.6% faster, consumed 6.4% less feed and required 7.5% less feed/100 kg gain than cattle fed control diets. Monensin resulted in the greatest improvement in feed/gain at 2.9 Mcal metabolizable energy (ME)/kg diet dry matter (DM). Within the range of monensin concentrations used in the trials that were summarized (31.8 +/- 7.5 mg/kg DM), high monensin concentrations did not improve feed/gain over that obtained with lower concentrations. Carcass characteristics were not significantly influenced by monensin. Responses of cattle to monensin and implants were additive. Energy metabolism data suggested that monensin improved digestibility of DM, reduced fasting heat production and increased dietary net energy maintenance (NEm) values more than it increased net energy gain (NEg) values. Data showing the response of cattle to monensin when fed various dietary protein concentrations or sources of supplemental N suggested that monensin had a protein sparing effect. Monensin has also been shown to reduce lactic acid production, aid in the control of coccidia and bloat and to be toxic to face and horn fly larva in feces of monensin-fed cattle. In pasture trials, monensin improved daily gains. When fed to beef cows, monensin reduced amounts of feed required to maintain cow weight.  相似文献   

6.
Thirty-six crossbred gilts were fed three levels of protein (146, 255 and 364 g/d) and two levels of energy (6,200 and 7,440 kcal of digestible energy/d) throughout gestation in a 3 x 2 factorial arrangement of treatments. Five-day N balance studies were conducted in early (0 to 30 d), mid- (30 to 60 d) and late (60 to 90 d) gestation. At slaughter (90 d of gestation), reproductive tracts were weighed and evaluated for reproductive performance and samples of the reproductive tract, liver and semimembranosus muscle (SM) were analyzed for crude protein. The right half of the carcass was subjected to a physical separation of fat, lean and bone. Neither dietary protein nor energy level significantly affected weight gain or reproductive performance. Nitrogen retention increased as dietary protein level increased and stage of gestation progressed (linear effect, P less than .01), but efficiency of N utilization and dry matter digestibility decreased with increasing protein intakes (quadratic effect, P less than .05 and linear effect, P less than .01, respectively). Nitrogen retention (P less than .01), efficiency of N retention (P less than .05) and dry matter digestibility (P less than .01) were higher in gilts fed high (H) energy compared with gilts receiving moderate (M) energy diets. Increasing dietary protein increased total carcass separable lean tissue (quadratic effect, P less than .01), liver weight (linear effect P less than .01) SM weight (quadratic effect, P less than .05) and SM percentage M (linear effect P less than .10). Similarly, total carcass N and carcass lean N increased as protein level increased (quadratic effect, P less than .10, P less than .05, respectively). In contrast to the increase in muscle N, N in uterine tissue and fluids was not affected by dietary protein level. The results of this experiment suggest that 146 g of crude protein/d during gestation is just as effective as higher levels of crude protein for litter size or storage of N in reproductive tissue, but 255 to 364 g of protein/d are required to maximize muscle N.  相似文献   

7.
A study consisting of two trials was conducted to determine the effects of monensin on the apparent absorption and retention of magnesium (Mg), phosphorus (P), calcium (Ca) and zinc (Zn) and to determine mineral changes in tissue and ruminal fluid. Eight lambs (39 kg) were used in trial 1, and 10 lambs (37 kg) were used in trial 2. Animals were blocked by weight and fed a high concentrate diet with or without 20 mg/kg monensin. Trials began with a dietary adjustment period lasting 18 d in trial 1 and 21 d in trial 2. Animals were then placed in metabolism stalls for a 10-d stall adjustment period followed by a 12-d collection period. Collections to determine mineral balance were made during the first 10 d of the collection period. Blood and ruminal fluid samples were taken on d 11 of the collection period. Lambs were slaughtered on d 12 of the collection period and tissue samples were collected. Monensin supplementation increased (P less than .05) Mg retention 42.0%. Urinary Ca excretion decreased (P less than .05) 60.0% when monensin was fed. Monensin supplementation decreased (P less than .05) liver Ca and bone Ca, 45.5 and 2.9%, respectively. Apparent P digestibility increased (P less than .05) 40.0% and P retention increased (P less than .10) 26.8% due to monensin supplementation. Both apparent absorption and retention of Zn increased (P less than .01) 50.0 and 45.0%, respectively, with monensin supplementation. Ruminal fluid Zn concentrations decreased (P less than .05) 33.0% with the addition of monensin.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

8.
Thirty-two pigs (average 26.6 kg live weight) were individually housed and fed to study the effect of an infection of Ascaris suum (either 0, 600, 6,000 or 60,000 A. suum eggs/pig) on performance of growing-finishing pigs. Increasing the level of A. suum infection produced linear (P less than .07) and quadratic (P less than .09) effects on final weight, weight gain and average daily gain. Feed to gain ratio and number of A. suum worms recovered from the intestines of pigs at slaughter increased linearly (P less than .01) with increasing doses of A. suum eggs. Pigs receiving 60,000 A. suum eggs were 13% less (P less than .01) efficient than the noninfected controls. In each of two trials, eight crossbred barrows (15.7 kg in trial 1 and 16.1 kg body weight in trial 2) were examined for the effects of two levels of A. suum infection (0 and 20,000 eggs/pig) on digestibility coefficients for dry matter, crude protein and gross energy. The infection did not affect (P greater than .05) digestibility coefficients during the first two collection periods (d 6 through 10 and 19 through 23). However, digestion coefficients for dry matter, crude protein and gross energy obtained from the total collection period on d 33 through 37 postinfection were greater (P less than .01) for control pigs than for pigs given 20,000 A. suum eggs each. Also, N retention was greater (P less than .05) for control pigs than for infected pigs.  相似文献   

9.
Forty-eight Angus and Hereford cows were used in a completely random design with a 2 X 2 factorial arrangement of treatments to evaluate the effects of monensin and two sources of Mg on performance, ruminal characteristics and mineral status of mature beef cows. Cows were fed wheat straw treated with NH3 during late gestation and straw treated with NH3 plus bromegrass haylage after calving along with a protein supplement that contained either MgO (7.5 g/kg) or MgSO4 (11 g/kg). One half of the cows received monensin (1 g/kg) in their protein supplement. During the precalving period, MgO without monensin increased (P less than .01) plasma Mg compared with Mg in plasma of cows receiving MgSO4 or MgO with monensin. Magnesium oxide also increased cow weight gains during late gestation (P less than .05) compared with weight gains of cows supplemented with MgSO4, but magnesium source had no effect on weight gain postcalving. Plasma glucose was increased by monensin (P less than .05) and by MgSO4 (P less than .01) during early lactation. Monensin increased the proportion of propionate before (P less than .05) and after (P less than .10) calving in the ruminal fluid of cows. Monensin also increased (P less than .05) cow weight gain precalving and tended to decrease (P less than .10) milk fat in lactating cows. Calf weight gains were not affected by treatment of dam. Magnesium oxide appeared to have higher Mg bioavailability than MgSO4 for cows precalving, but Mg bioavailability was not different postcalving. Monensin increased cow weight gains precalving and improved feed efficiency postcalving.  相似文献   

10.
The influences of pelleting and beta-glucanase supplementation on the digestibility of dietary components in a barley-based diet were investigated in pigs fitted with cannulas in the terminal ileum. The diet contained 49.0% starch, 18.9% crude protein and 14.8% dietary fiber, with arabinoxylans (4.9%), mixed-linked beta-glucans (3.4%) and cellulose (3.3%) as the main fiber components. Pelleting increased mixed-linked beta-glucan solubility from 45 to 62%. Neither treatment influenced the ileal or fecal apparent digestibilities of dry matter (64 and 80%, respectively), energy (62 and 79%), crude protein (53 and 75%), crude fat (26 and 27%) or dietary fiber (58 and 72%). However, pelleting increased (P less than .01) the pre-ileal apparent digestibility of starch from 91.5 to 95.3% and decreased (P less than .03) that of ash from -10 to -23%, while increasing (P less than .005) the fecal apparent digestibility of starch from 98.6 to 99.7%. The solubility of mixed-linked beta-glucans in ileal digesta was lower (P less than .001) in pelleted (26%) than in unpelleted (58%) diets. beta-glucanase supplementation also increased (P less than .05) the ileal apparent digestibility of starch, from 92.6 to 94.3%, and of mixed-linked beta-glucans, from 95.7 to 97.1%. Significant between-pig differences in the apparent digestibility of dietary components were observed. In conclusion, treatments that disrupt the endosperm cell walls in barley can increase the proportion of the diet digested prior to the large intestine.  相似文献   

11.
Monensin in ruminant diets increases production of propionic acid. We have tested the hypothesis that propionic acid may be elevated to such an extent by monensin that it cannot be optimally metabolized by the methyl malonyl-CoA pathway requiring vitamin B12 (B12) in the liver. Thus, the effects of weekly B12 injections (10 mg X head-1 X wk-1, intramuscularly) with and without dietary monensin (25 mg/kg diet) on average daily gain (ADG), dry matter intake (DMI), feed to gain ration (F/G), liver and serum B12 concentrations and liver activity of propionate metabolizing enzymes were examined in an 84-d trial. Sixteen lambs (27.5 kg average initial wt) were assigned randomly to one of four treatments in a factorial arrangement: monensin plus B12, monensin without B12, no monensin plus B12 and no monensin without B12. Lambs were fed an 80% concentrate diet and slaughtered at the end of the trial. Liver samples were obtained by biopsy on d 0 and at slaughter on d 84 to determine activity of propionate metabolizing enzymes and B12 concentrations. Serum samples were taken on d 0, 28, 56 and 84 to determine serum B12 concentration. Neither monensin nor B12 affected (P greater than .10) ADG, DMI or F/G. Lambs receiving B12 had higher (P less than .01) serum B12 concentrations, but this was not reflected (P greater than .10) in higher liver B12 concentrations. No difference (P greater than .10) in liver propionate metabolizing activity among treatments was detected; however, monensin decreased (P less than .05) fumarate and malate formation by liver homogenates. Liver B12 concentrations were highly correlated with endogenous propionate metabolizing activity at d 0 (r = .73, P less than .01) and d 84 (r = .51, P less than .05). Results suggest no advantage to providing supplemental B12 to lambs fed monensin-supplemented, high-concentrate diets.  相似文献   

12.
Peanut skins were fed at 15% of steer diets in metabolism and feedlot trials. Elevation of dietary protein using soybean meal or soybean meal plus urea and ammoniation of skins were evaluated as methods of overcoming detrimental performance and digestibility effects of tannins in peanut skins. Digestibility of dry matter, crude protein and energy were not different (P greater than .05) for steers fed a control diet with 11.4% crude protein with no skins compared with high-protein 15% peanut skin diets with soybean meal (15.5% crude protein) or soybean meal plus urea (16% crude protein). Dry matter, crude protein and energy digestibilities of control and of high-protein peanut skin diets were higher (P less than .05) compared with an 11.4% crude protein peanut skin diet and a 12.2% crude protein diet with ammoniated peanut skins. Ether extract digestibility was higher (P less than .05) for all peanut skin diets compared with the control. Nitrogen retention (g/d) was not different (P greater than .05) for control and high-protein peanut skin diets, and nitrogen retention on these diets was higher (P less than .05) compared with the lower protein and ammoniated peanut skin diets. Diets fed in the metabolism trial, except for the ammoniated peanut skin diet, were fed to 96 steers (345 kg initial wt) in a 109-d feedlot trial. Performance was lower (P less than .05) for steers fed the lower-protein peanut skin diet compared with other treatments through d 56; this diet was discontinued as a treatment on d 62.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

13.
Fourteen trials were conducted to evaluate the effects of feeding monensin at 33 ppm alone, tylosin at 11 ppm alone and the two feed additives in combination on the average daily gain, average daily feed intake, feed:gain ratio and the incidence of liver abscesses in feedlot cattle. Monensin reduced feed intake and improved feed efficiency (P less than .05), and had no effect on average daily gain. Tylosin improved average daily gain (P less than .05) and had no effect on daily feed intake. The effect of tylosin on feed efficiency approached significance. The interaction of monensin and tylosin was nonsignificant for daily gain, daily feed intake and feed:gain ratio. Monensin had no effect on liver abscess incidence, while tylosin reduced abscess incidence from 27 to 9%.  相似文献   

14.
A series of experiments was conducted to determine the effects of limit-feeding high-concentrate (LFHC) diets on dietary CP requirements of steer calves. When steer calves were fed 80% concentrate diets at 78 g/kg of BW.75, increasing dietary CP resulted in increased ADG (P less than .001). Average daily gain was increased in steers as daily monensin dosage increased from 120 to 180 mg (P less than .05). Increasing the daily monensin dosage to 240 mg did not increase ADG further. There were no (P greater than .10) CP X monensin interactions, suggesting that the monensin response was caused by improved energy utilization and not be the possible protein-sparing effects of ionophores. Steer calves in the second feedyard experiment expressed similar ADG when provided equal NEg as limit-fed, high-moisture ear corn (HMEC) or when given ad libitum access to corn silage. The basal diet did not affect the steers' daily N requirement for growth. Gain per unit of protein intake declined quadratically (P less than .05) with increasing CP intake, indicating that CP requirements were near NRC estimates on both diets. The corn silage-based diet was less digestible (70.3 vs 77.4%; P less than .01) than the HMEC diet when fed to lambs. Fecal output differed (P less than .10) substantially (342 g/d of corn silage vs 205 g/d of HMEC), whereas fecal N output was only slightly higher (6.97 vs 6.34 g/d, respectively; P less than .10). Limited feeding of higher-concentrate diets to steer calves seemed to be an effective management procedure and did not cause acute digestion upset.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

15.
邓培华  王娟  洼桑措  付建 《中国饲料》2021,1(6):107-110
本研究旨在探讨马铃薯藤饲喂水平对山羊生长性能、养分消化率和胴体特征的影响。试验将平均初始体重为（14.42±0.24）kg的40头山羊随机分为4组,每组5个重复,每个重复2头。T1组仅饲喂干草,T2组饲喂干草+100%马铃薯藤,T3组饲喂干草+50%马铃薯藤+50%浓缩料,T4组饲喂100%浓缩料。在为期10周的饲养试验后屠宰,分析胴体特征。结果：T2～T4组山羊的末重、增重、日增重和饲料效率显著高于T1组（P＜0.05）,其中T1组山羊的日增重和增重均表现出负增长。T2～T4组山羊的干物质、有机物、粗蛋白质和代谢能摄入量均显著高于T1组（P＜0.05）,但T2和T3组山羊中性洗涤纤维摄入量显著高于T1和T4组（P＜0.05）。T2、T3和T4组山羊干物质和有机物表观消化率显著高于T1组（P＜0.05）,T4组山羊粗蛋白表观消化率显著高于T1和T2组（P＜0.05）。T2、T3和T4组山羊屠体重、热胴体重、眼肌面积、可食用内脏和不可食用内脏重量均显著高于T1组（P＜0.05）。T3组山羊的屠宰率显著高于其他组（P＜0.05）。结论：在干草为基础的日粮中添加马铃薯藤可以提高山羊采食量、饲料转换率、养分消化率、屠宰率和胴体特征。 [关键词]马铃薯藤|山羊|生长性能|消化率|胴体特征  相似文献   

16.
To evaluate the effect of zeranol implants in steers on compensatory ++growth, 80 steer calves (9 mo of age; 200 kg) were fed at two feeding levels (RO = 9.2 MJ ME/kg DM; R1 = 6.9 MJ ME/kg DM) for 119 d (Period 1). During Period 2, steers were full-fed to 400 kg BW with (Z1) or without (ZO) zeranol implants. Ten steers were slaughtered at the end of Period 1 to estimate carcass composition. Differences of 100 kg in BW were achieved by restriction in Period 1. Subsequent to restriction, cumulative ADG remained greater (P less than .05) up to the 24th wk of recuperation and implants increased (P less than .001) BW gain by 31% and 24% for RO and R1, respectively. The average daily energy intake (ME/W(.75) in Period 2 was similar for all treatments. Feed conversion was improved by 21.5% (P less than .05) by implants. At the end of Period 2 the R1ZO had 8.6 kg less muscle (P less than .001), 2.9 kg less bone (P less than .001) and 5.9 kg more fat (P less than .05) than the ROZO. In comparison, the carcasses of the implanted animals did not show significant differences (P greater than .05) due to restriction. Carcass daily gains were increased by previous restriction (P less than .01) and implants (P less than .05). Zeranol increased daily live weight gain and feed conversion in animals in continuous growth as well as in those observed in compensatory growth an tended to eliminate a tendency for higher content of fat in carcasses of nonimplanted animals making compensatory growth.  相似文献   

17.
Crossbred wethers (n = 48) were assigned randomly to 1 of 12 experimental diets, arranged in a 3 X 2 X 2 split plot to evaluate three levels of cotton plant by-product (25, 50 and 75% CPB), two levels of NaOH treatment of CPB (0 and 4%) and two levels of monensin supplementation (0 and 30 ppm, DM basis) at two intake levels (70 and 90% of ad libitum). Intake was a within-lamb variable. Ad libitum intake was established over an initial 17-d adjustment period. Feed intake and fecal output were recorded during collection periods with aliquots retained for laboratory analysis. Intake was affected by a linear CPB X monensin interaction (P less than .06) with monensin depressing intake more at higher CPB levels. Neutral detergent fiber (NDF) digestibility decreased linearly (P less than .001) as the dietary level of CPB increased. NaOH treatment of CPB improved (P less than .001) the digestibility of organic matter (OM) and NDF. The supplementation of 30 ppm monensin resulted in greater (P less than .004) apparent digestibilities of NDF and hemicellulose (HC). Increasing daily feed intake from 70 to 90% of ad libitum decreased (P less than .004) digestibility of NDF, HC and ADF.  相似文献   

18.
Two experiments were conducted to determine the apparent ileal digestibility of DM and N by young pigs fed diets supplemented with different protein sources or organic acids. Pigs were surgically fitted with silicone cannulas at 2 wk of age. Following surgery, pigs were allowed to recuperate with their dams while suckling normally. After weaning at 24 d, pigs were assigned to treatment diets at 28 d of age. A 3-d adjustment and 4-d collection sequence was followed for the duration of the 4-wk experiment. Four treatment diets were fed in each experiment in a weekly rotation until each diet had been fed to each pig. Diet samples and digesta collected through the ileal cannulas were analyzed for chromic oxide (used as an indigestible marker), DM, and N. Pigs in Exp. 1 were fed isolysinic (1.0%) corn-based diets supplemented with casein, soybean meal, soy protein concentrate, or isolated soy protein. Casein addition resulted in improved DM (P less than .001) and N (P less than .05) digestibility but reduced gain (P less than .05) compared with the average of the soy protein sources. Nitrogen from diets formulated with soybean meal was digested more completely (P less than .05) than N from diets based on soy protein concentrate and isolated soy protein. Experiment 2 was an evaluation of the effect of dried skim milk (25%) and fumaric acid (2%) addition on apparent ileal digestibility of N and DM in corn-soybean meal diets. Addition of dried skim milk improved DM (P less than .01) and N (P less than .05) digestibility and daily gain (P less than .001). Fumaric acid supplementation did not affect nutrient digestibility or gain (P greater than .10).  相似文献   

19.
The effects of ionophores on liver weight and function were determined in finishing steers (n = 24; avg weight 440 kg). Steers were group-fed one of three treatments (control, lasalocid or monensin at 33 mg/kg feed) for 46 d prior to slaughter. Three days prior to slaughter, blood was collected for the determination of serum Ca and Mg. At slaughter, the liver was removed, weighed, sampled, frozen in liquid nitrogen and subsequently analyzed for concentrations of carbohydrate metabolites and minerals. Liver weight (5.9 kg) was unaffected by treatment. Serum and hepatic Ca and Mg were not affected by ionophore treatment. Hepatic glycogen levels in steers fed ionophores were unaffected by treatment. Fructose 1,6-bisphosphate was 21% lower (P less than .10) in hepatic tissue of steers fed ionophores, whereas dihydroxyacetone phosphate was 15 to 37% greater in hepatic tissue of steers fed monensin (P less than .20) or lasalocid (P less than .10). Glyceraldehyde 3-phosphate was elevated more extensively by lasalocid than by monensin with increases of 72 (P less than .05) and 132% (P less than .001), respectively, over controls. Glycerol 3-phosphate levels were 37% (P less than .05) and 12% (NS) greater with these ionophores. Hepatic levels of pyruvate were elevated 12 (NS) to 36% (P less than .17) for monensin and lasalocid. Fructose 2,6-bisphosphate levels were 25% lower (P less than .25) in hepatic tissue of steers fed ionophores than in hepatic tissue from control steers. Other metabolites of carbohydrate metabolism in hepatic tissue were not altered appreciably. Changes in levels of intermediary metabolites of carbohydrate metabolism suggest alterations in hepatic carbohydrate metabolism favoring gluconeogenesis in steers fed ionophores.  相似文献   

20.
Rates of growth and partitioning of nutrients among tissues were measured in large (Simmental x [Hereford x Brahman]; n = 34) and very large (Chianina x Angus and Maine Anjou x Angus; n = 37) steers implanted with different anabolic growth regulators. All cattle were fed individually a whole shelled corn (13% crude protein) diet. Implant strategies were: none (n = 13), Ralgro 36 mg (n = 15), Ralgro 72 mg (n = 14), Synovex-S (n = 15) and Ralgro 36-Synovex-S (n = 14) administered at d 0 and 90. Empty body composition of all cattle was measured initially and at 90 d by D2O dilution procedures and at slaughter (average, 182 +/- 4.1 d) by carcass specific gravity. Empty body weight for large and very large cattle averaged 274 and 324 kg (P less than .05) initially and 497 and 603 kg (P less than .05) at slaughter. Empty body protein differed (P less than .05) for large and very large steers and averaged 51 and 61, 67 and 79, and 87 and 103 kg initially, at midpoint and at slaughter, respectively. Percentage empty body fat was lower for very large steers (13.5 vs 15.6%) initially (P less than .05) but was similar for very large and large steers at the midpoint (18.7 vs 18.1%) and at slaughter (23.2 vs 21.9%). Daily rates of empty body gain (DEBG) were greater (P less than .05) for very large vs large steers for both growing and finishing periods and averaged 1.53 vs 1.26 kg/d overall. Daily rates of protein gain (DPG) were similar for very large and large steers for the growing phase (204 vs 202 g/d) but greater (P less than .05) in very large steers for the finishing phase and overall (253 vs 204, and 229 vs 202 g/d). All implant strategies, except R36, increased DEBG and DPG and tended to decrease the percentage of fat in daily gain. In both large and very large cattle, implant growth regulators increased growth rate and partitioned nutrient use away from fat toward protein accretion, with the magnitude of partitioning toward protein increasing with greater rates of growth. These data indicate that anabolic growth regulators are viable strategies to enhance lean beef production in steers, regardless of animal size.  相似文献   

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