Effect of live weight gain of steers during winter grazing: III. Blood metabolites and hormones during feedlot finishing

Two experiments were conducted using 48 Angus x Angus-Hereford steers in each experiment to determine the effect of previous winter grazing BW gain on jugular concentrations of metabolites and hormones during feedlot finishing. In each experiment, steers were randomly assigned to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range (NR) with 0.91 kg/d of a 41% CP (DM basis) supplement. Steers grazed for 120 or 144 d in Exp. 1 and 2, respectively. Plasma and serum were collected from all steers before placement into a feedlot, and six or seven times during finishing in Exp. 1 and 2, respectively. In Exp. 1, before steers entered the feedlot, concentrations of insulin, triiodothyronine (T3), and thyroxine (T4) were greater (P < 0.05) in HGW than in LGW or NR steers, and concentrations of IGF-I and plasma urea-N were greater (P < 0.05) in steers that grazed wheat pasture than in NR steers. In Exp. 2, concentrations of glucose, T3, T4, and IGF-I were greater (P < 0.05) in steers that grazed wheat pasture than NR steers. In Exp. 1 (P < 0.19) and 2 (P < 0.86), glucose concentration did not differ among treatments during finishing. In Exp. 1, insulin concentration across days on feed was greater for HGW than LGW steers, which were greater than for NR steers (treatment x day interaction, P < 0.03). In Exp. 2, insulin concentration increased (P < 0.001) as days on feed increased. Concentrations of IGF-I were greater in steers that had grazed wheat pasture, whereas the increase in IGF-I with increasing days on feed was greater for NR steers (treatment x day interaction, P < 0.003). Concentrations of T3 and T4 during finishing were greater (P < 0.001) in HGW and LGW than in NR steers in Exp. 1. In Exp. 2, T4 concentration also differed (P < 0.009) among treatments (HGW > LGW > NR). In Exp. 2, final concentration of glucose was greater (P < 0.01) in NR than in HGW and LGW steers, and serum insulin concentration was greater (P < 0.04) in NR than LGW steers. Final concentrations of T3 (P < 0.01) and T4 (P < 0.004) were greater in NR than in HGW steers. Our data show that previous BW gain can affect blood metabolites and hormones in steers entering the feedlot. However, lower concentrations of T3, T4, and IGF-I in steers when they entered the feedlot did not inhibit the growth response of previously restricted steers.     

Effect of live weight gain of steers during winter grazing: I. Feedlot performance, carcass characteristics, and body composition of beef steers

Two experiments were conducted to examine the effect of previous BW gain during winter grazing on subsequent growth, carcass characteristics, and change in body composition during the feedlot finishing phase. In each experiment, 48 fall-weaned Angus x Angus-Hereford steer calves were assigned randomly to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range (NR) supplemented with 0.91 kg/d of cottonseed meal. Winter grazing ADG (kg/d) for HGW, LGW, and NR steers were, respectively, 1.31, 0.54, 0.16 (Exp. 1) and 1.10, 0.68, 0.15 (Exp. 2). At the end of winter grazing, four steers were selected randomly from each treatment to measure initial carcass characteristics and chemical composition of carcass, offal, and empty body. All remaining steers were fed a high-concentrate diet to a common backfat end point. Six steers were selected randomly from each treatment for final chemical composition, and carcass characteristics were measured on all steers. Initial fat mass and proportion in carcass, offal, and empty body were greatest (P < 0.001) for HGW, intermediate for LGW, and least for NR steers in both experiments. Live BW ADG and gain efficiency during the finishing phase did not differ (P = 0.24) among treatments, but DMI (% of mean BW) for NR and LGW was greater (P < 0.003) than for HGW steers. Final empty-body composition did not differ (P = 0.25) among treatments in Exp. 1. In Exp. 2, final carcass and empty-body fat proportion (g/kg) was greater (P < 0.03) for LGW and NR than for HGW steers. Accretion of carcass fat-free organic matter was greater (P < 0.004) for LGW than for HGW and NR steers in Exp. 1, but did not differ (P = 0.22) among treatments in Exp. 2. Fat accretion in carcass, offal, and empty body did not differ (P = 0.19) among treatments in Exp. 1, but was greater (P < 0.05) for LGW and NR than for HGW steers in Exp. 2. Heat production by NR steers during finishing was greater (P < 0.02) than by HGW steers in Exp. 1 and 2. Differences in ADG during winter grazing and initial body fat content did not affect rate of live BW gain or gain efficiency during finishing. Feeding steers to a common backfat thickness end point mitigated initial differences in carcass and empty-body fat content. However, maintenance energy requirements during finishing were increased for nutritionally restricted steers that were wintered on dormant native range.     

Effect of the live weight gain of steers during winter grazing on digestibility, acid-base balance, blood flow, and oxygen consumption by splanchnic tissues during adaptation and subsequent feeding of a high-grain diet

Ten multicatherized steers were used in a completely random design to determine the effect of previous BW gain on blood flow, acid-base balance, and oxygen consumption across portal-drained viscera and liver of growing beef steers fed a high-grain diet. Treatments were high (1.31 +/- 0.09 kg/d) or low (0.68 +/- 0.07 kg/d) daily BW gain during an 82-d winter wheat pasture grazing period and a subsequent 37-d transition period. Blood flow, blood gas measurements, and oxygen consumption were determined on d 0, 14, 28, 42, and 64 of a high-grain finishing period. Compensatory growth was evident in low-gain steers; ADG (1.50 vs. 1.11 kg/d, P < 0.05) and gain efficiency (0.221 vs. 0.109 kg/kg, P < 0.01) were greater from d 14 through 28 than for high-gain steers. Arterial base tended (P < 0.12) to be greater in low-gain than in high-gain steers, whereas calculated HCO3- (mmol/L; P < 0.20) did not differ between treatments. Arterial O2 concentration was not different (P < 0.97) between treatments but increased (P < 0.001) with increasing days on feed. Portal blood flow increased with days on feed (P < 0.001) but did not differ (P < 0.34) between treatments. Hepatic blood flow scaled to metabolic BW was 19.7% greater (P < 0.02) in low-gain than in high-gain steers. Across the feeding period, O2 consumption and CO2 flux by PDV, liver, and total splanchnic tissue (TST) did not differ (P < 0.33) between treatments. However, TST O2 consumption (mmol/[h x kg BW(0.75)]) tended (P < 0.12) to be greater in low- than in high-gain steers. Compensating steers' arterial blood acid-base measurements did not change with days on feed, indicating that they were not more susceptible to metabolic acidosis than high-gain steers. However, steers that had lower BW gain before high-grain feeding exhibited increased hepatic blood flow and TST O2 consumption (metabolic BW basis) during the finishing period compared with high-gain steers. Greater hepatic blood flow and energy expenditure by TST of previously restricted steers might have facilitated compensatory growth.     

Effect of high-selenium wheat on visceral organ mass, and intestinal cellularity and vascularity in finishing beef steers

Twelve crossbred steers (351 +/- 24 kg initial BW) were used to determine effects of high-Se wheat on visceral tissue mass, intestinal cell growth, and intestinal cellularity and vascularity. Steers were allotted randomly by BW to one of two treatments consisting of 75% concentrate diets that supplied 1) adequate Se concentration (7 to 12 microg x kg x BW(-1) x d(-1)) or 2) high-Se concentration (60 to 70 microg x kg x BW(-1) x d(-1)). Diets were similar in composition, including 25% grass hay, 25% wheat, 39% corn, 5% desugared molasses, and 6% wheat middlings supplement on a DM basis. In the Se treatment, high-Se wheat (10 ppm Se, DM basis) was replaced with low-Se wheat (0.35 ppm Se, DM basis). Diets were formulated to be similar in CP and energy (14.0% CP, 2.12 Mcal of NEm/kg, and 1.26 Mcal NEg/kg of DM) and were offered daily (1500) to individual steers in an electronic feeding system. Diets were fed at 2.38% BW. After 126 d, steers were slaughtered, and individual visceral tissue weights determined. Concentrations of DNA, RNA, and protein of duodenum, ileum, and total small intestine were not affected (P > or = 0.33) by treatment. Similarly, RNA:DNA and protein:DNA ratios in duodenum, jejunum, ileum, and whole small intestine were not (P > or = 0.33) affected by feeding high-Se wheat. Conversely, jejunal weight was greater (P < 0.002) in steers fed high-Se wheat than in controls (916 vs. 1,427 +/- 84 g). Jejunal DNA was increased (P < 0.04) in steers fed high-Se wheat (2.95 vs. 3.56 +/- 0.19 mg/g), suggesting increased cell number. Concentrations of jejunal RNA and protein were not altered by treatment; however, because the jejunal weight increased in high-Se steers, DNA, RNA, and protein contents (grams) were greater than in control steers (P < 0.05). Vascularity of jejunal tissue decreased (P < 0.10) with high-Se wheat; however, because jejunal mass was greater for the high-Se wheat treatment, total microvascular volume was not affected by treatment. Percentage of jejunal crypt cell proliferation was not affected (P = 0.48) by treatment; however, total number of cells proliferating within the jejunum was increased in steers fed high-Se wheat. Data indicate that the lower jejunal vascularity in the diet high in Se (provided from wheat) may have resulted in increased jejunal mass to meet physiological nutrient demand. Therefore, negative effects of Se level used in this study on productive performance of feedlot steers are not expected.     

Low quality roughages for steers grazing wheat pasture. I. Effect on weight gains and bloat

The effect of feeding low quality roughages (LQR) on live and carcass weight gains and the incidence and severity of bloat of stocker cattle grazed on wheat pasture was evaluated in a 3 yr study. One hundred eighty-five steer calves (172 kg mean initial weight) grazed clean-tilled wheat pasture and were either fed no LQR or had ad libitum access to wheat straw (WS) or sorghum-Sudan hay (SS). Grazing periods were (I) fall grazing, (II) winter grazing, (III) period of lush spring growth of wheat forage and (IV) period of advancing forage maturity and declining quality. Mean dry matter (DM), crude protein and acid detergent fiber (ADF) content (percentage of DM) of wheat forage averaged across years ranged, respectively, from 23.8 to 33.0, 19.8 to 26.4 and 21.5 to 27.7. Mean daily consumption (kg DM/head) of WS and SS by steers ranged from .076 to .100 and .199 to .248, respectively. Live and carcass weight gains of steers during Periods I through III (i.e., the usual wheat pasture grazing period) were not influenced (P greater than .05) by treatments. Carcass weight gains were about 74% of live weight gains. Bloat was observed only during the last 2 wk of Period III of the first year. The incidence (steer days of bloat) and severity (bloat score) of control, WS- and SS-fed steers were 9.5 and 1.2, .5 and .5 and 2.0 and 1.0, and were not different (P greater than .05) among treatments. Intake of WS and SS [g/body weight (BW).75kg] during Periods I to III was, respectively, only about 5 and 12% of roughage intakes (i.e., 37.5 g/BW.75kg) reported in the literature to "effectively control" or aid the prevention of bloat. It seems unlikely that LQR consumed to amounts similar to those of this study would control bloat of stocker cattle on wheat pasture.     

Technical note: utilization of sainfoin by grazing steers and a method for predicting daily gain from small-plot grazing data.

Sainfoin (Onobrychis viciaefolia Scop.) is adapted to the calcareous soils of the southern Great Plains and can provide early season forage that does not induce bloating; however, little is known about performance by ruminants grazing sainfoin. Our objective was to determine the effect of plant growth stage and grazing pressures on potential animal production from sainfoin as predicted from energy intake as a multiple of maintenance. Nitrogen-fertilized (100 kg of N/ha) Renumex sainfoin was grown under irrigation on a Pullman clay loam (fine, mixed, thermic Torretic Paleustoll) near Lubbock, TX. Light (L), medium (M), and heavy (H) grazing pressures were applied with steers grazing sainfoin that was at the bud (B), flower (F), and seed shatter (S) stages of growth. The L, M, and H pressures were grazed to remove 50, 75, and 90% of the standing plant height. Across growth stages, L, M, and H grazing pressures averaged 52, 69, and 87% removal of pregrazed herbage mass. Dry matter intake as a percentage of BW of steers averaged 3.9, 2.8, and 1.7 for L, M, and H grazing pressures. Across growth stages, predicted live weight gain for L, M, and H grazing pressures averaged .86, .67, and .03 kg/d. Our findings indicate that the multiple of maintenance method may be useful for evaluating treatments from small-plot grazing experiments.     

Effects of a monensin ruminal delivery device on daily gain, forage intake and ruminal fermentation of steers grazing irrigated winter wheat pasture

Two trials evaluated the effects of a monensin ruminal delivery device (MRDD) on steers grazing winter wheat pasture. In Trial 1, 60 Hereford steers (initial wt 238.5 kg) grazed a 21.9-ha paddock of Vona-variety winter wheat for 112 d. Steers were assigned to either MRDD or control (C) treatments in a randomized complete block design. In Trial 2, eight ruminally cannulated steers (avg wt 234.4 kg) grazed a 2.4-ha paddock of Vona-variety wheat and were assigned randomly to either MRDD or C treatments. Three 11-d collection periods were conducted during early February, early March and early April. Chromic oxide was dosed to determine fecal output, and ruminal samples were collected on d 6 of each period. Nylon bags containing ground wheat forage were incubated ruminally beginning on d 8. In Trial 1, steers with MRDD tended (P less than .11) to gain more weight than C steers (.44 vs .38 kg/d). In Trial 2, wheat forage intake, in situ DM disappearance, ruminal pH, ruminal ammonia concentrations and ruminal proportions of acetate and total VFA concentrations were not affected by treatment. Ruminal proportions of propionate were increased (P less than .05) slightly by MRDD (20.3 and 19.2 mol/100 mol for MRDD and C, respectively). Butyrate proportions in ruminal samples were decreased (P less than .05) by MRDD during March but not in other sampling periods. Ruminal fluid chlorophyll concentration was less (P less than .05) for MRDD-treated vs C steers during early March but was greater (P less than .10) for MRDD-treated steers during early April. The MRDD shows promise as a method of supplying monensin to cattle grazing winter wheat forage.     

Ruminal escape protein supplementation and zeranol implantation effects on performance of steers grazing winter annuals.

Fifty-four crossbred steers (275 kg) were assigned randomly to one of three isoenergetic but not isonitrogenous ruminal escape protein (EP) supplements: high ruminal escape protein (HEP), low ruminal escape protein (LEP), or corn. The supplements contained corn, distillers' dried grains with solubles (DDGS), and fish meal. Supplements were fed at approximately 1.5 kg/d; the HEP and LEP supplements provided .25 and .12 kg more EP per day than corn, respectively. These supplements also supplied .20 and .10 kg more CP per day than corn. Fish meal and DDGS provided 66.7 and 33.3% of the supplemental EP, respectively. One-half of the steers in each supplement treatment were implanted once with 36 mg of zeranol. Steers grazed wheat (Triticum aestivum L.)-annual ryegrass (Lolium multiflorum Lam.) pastures for 73 d (March 1 to May 12). Daily gains (kg/d) increased linearly (P less than .07) as EP increased (HEP, 1.61; LEP, 1.54; corn, 1.47); responses were apparent only during the later periods as forage quality declined. Zeranol implants increased (P less than .02) ADG (kg/d) by 9.7% (1.58 vs 1.44). After grazing, all cattle were fed a finishing ration for 76 d. Pre-feedlot EP level produced a negative linear (P less than .04) response on feedlot ADG (kg/d) (HEP, 1.44; LEP, 1.50; corn, 1.59). Zeranol implantation during the grazing phase did not affect (P greater than .2) performance during the feedlot phase or carcass characteristics other than increased ribeye area (P less than .08). Compensatory feedlot performance negated all weight gain advantages elicited by EP supplementation during the grazing period.(ABSTRACT TRUNCATED AT 250 WORDS)     

补饲控释尿素对放牧牦牛和藏羊日增重的影响

以藏羊和牦牛为研究对象,采用单因素分期分组设计,分两期进行。分别在海北同保牧场暖季、冷季做补饲控释尿素对藏羊和牦牛增重试验。结果表明：在冷季补饲时,试验期藏羊对照组、试验组只均增重分别为0.79 kg&#177;0.32 kg、1.85kg&#177;0.50 kg;试验期牦牛对照组、试验组只均增重分别为4.59 kg&#177;1.63 kg、7.52 kg&#177;1.30 kg,两组间增重差异均极显著（P〈0.01）。而在暖季补饲控释尿素,效果不显著。     

Effects of body weight, frame size and rate of gain on the composition of gain of beef steers

Energy concentration of gain (EG) is an inherent component in beef cattle feeding systems. The National Research Council (NRC) uses equations based on body weight, rate of gain and cattle type to predict EG and, in turn, to calculate dietary energy requirements. From EG, fat and protein deposition can be calculated directly. A dynamic computer growth model also can be used to estimate EG. In both the NRC and the computer model, EG increases from about 3 to 6 Mcal/kg as body weight increases from 200 to 500 kg if daily gain is 1 kg. Both NRC and the model predict EG of calves to be about .3 Mcal/kg greater than a previous NRC system. In contrast to the NRC, model-predicted EG of yearlings is lower at lighter and greater at heavier body weights. Rate of gain affects estimates of EG more for the dynamic model than for the NRC systems. When predicted EG was compared with observed EG for 46 pens of feedlot steers in comparative slaughter trials, NRC estimates exhibited a narrow range compared with observed values with correlation coefficients of r = .38 and r = .71 (previous NRC). Model estimates of EG were closer (r = .85). The NRC predictions of EG systematically erred with initial body composition, diet metabolizable energy and length of feeding period (P less than .01) and with initial body weight and rate of gain (P less than .05). No systematic errors in model-predicted EG were detected. Enhanced model sensitivity to compensatory growth and rate of gain should reduce both EG and body weight gain prediction errors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Impact of grazing intensity on herbage intake, composition, and digestibility and on live weight gain of sheep on the Inner Mongolian steppe

High grazing pressure during the last decades caused severe ecological problems in the steppe of Inner Mongolia, China. The objective of the present study was to determine the effects of grazing intensity of sheep on herbage mass (HM) and intake, chemical composition and digestibility of herbage, and on live weight gain (LWG). A grazing experiment with six different grazing intensities (1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 sheep/ha) was conducted in the growing season of 2005 in the Xilin River Basin. HM decreased from 1.5 t DM/ha at the lowest grazing intensity to 0.6 t DM/ha at the highest grazing intensity. NDF content of the herbage was high (> 700 g/kg DM) and relatively constant, whereas acid detergent lignin (ADL) content increased with grazing intensity and with proceeding grazing season. Digestibility of organic matter ingested (DOM) tended to decrease with grazing intensity as well as intake of organic matter (OMI) and of digestible organic matter (DOMI) per sheep (P = 0.090 and P = 0.065, respectively), whereas LWG per sheep decreased with increasing grazing intensity (P = 0.018). DOM and OMI were negatively related to ADL content. However, herbage intake and LWG per ha increased with grazing intensity (P < 0.001) and reached their maximum at 9 and 7.5 sheep per ha, respectively. This observation confirms the current farmers' practise of high grazing pressure ignoring long term grassland productivity and ecological problems. Therefore, the studies are continued to provide further information on long term effects. This study could show pronounced effects of grazing intensity on animal and grassland productivity and the suitability of the methods applied to measure intake and digestibility of herbage in a large scale grazing experiment with sheep.     

Effects of grass species on grazing steers: II. Dry matter intake and digesta kinetics

Animal responses to treatments in grazing experiments frequently remain unexplained because of inadequate pasture and(or) animal measurements. This 2-yr study examined DMI, gastrointestinal tract fill of undigested DM (FILL), rate of digesta passage (ROP), and digesta mean retention time (MRT) for steers grazing tall fescue (Festuca arundinacea Schreb.), switchgrass (Panicum virgatum L.), flaccidgrass (Pennisetum flaccidum Griseb.), and bermudagrass (Cynodon dactylon [L.] Pers.). A randomized complete block design was used with two agronomic replicates. Comparisons in June (yr 1) among continuously grazed switchgrass (SG), flaccidgrass (FG), and bermudagrass (BG) or in May (yr 2) among tall fescue (TF), SG, and FG showed similar digesta kinetics, but different DMI (kg.d-1.100 kg BW-1), among these forages within each sampling. In the June evaluation, the DMI of SG and FG were similar (means = 3.09), DMI of bermudagrass (BG) was lowest (2.23), and fecal DM output (FO) was similar among forages. In the May evaluation, DMI by steers grazing SG (3.90) was higher than that by steers grazing FG (2.97); DMI of tall fescue (TF) was intermediate (3.41) but similar to DMI of FG. Differences in DMI were due to differences in diet in vitro DM disappearance (IVDMD) rather than to differences in digesta kinetics. In July (yr 2), the MRT was highest for BG (84 h) and similar for SG and FG (57 h). Steers grazing different forages exhibited similar ROP and FILL, but FO (kg.d-1.100 kg BW-1) among steers varied (.37 for steers fed BG; .74 for steers fed SG and FG).(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of live weight gain and live weight loss on body composition of merino wethers: chemical composition of the dissected components.

Chemical composition of the dissected side parts and dissected side was measured during live weight gain (LWG) and live weight loss (LWL) to determine effects on the chemical composition of the dissected side parts. Thirty-five Merino wethers had ad libitum access to the experimental diet (17.23% CP and 12.09 MJ/kg of DE) to grow from 23.0 to 33.0 kg live weight and then were fed to lose a total of 10 kg in three periods of 25 d each at the rate of 133 g/d. Groups of five animals were slaughtered at live weights of 23.0, 26.3, 29.6, and 33.0 kg during LWG and 29.6 kg (first period), 26.3 kg (second period), and 23.0 kg (third period) during LWL. The greater dissected side weight in LWL animals than in LWG animals at 23.0 kg of live weight was due to the significantly greater chemical fat (P < .05) in the LWL animals than in the LWG animals at 23.0 kg. There were no significant differences between treatments in the protein and water weights in the dissected side. The general increase in the chemical fat in the dissected side of the LWL animals was due to the significant increase in the chemical fat in the muscle (P < .01) and bone (P < .01, 23.0 and 26.3 kg and P < .05, 29.6 kg) at each common slaughter weight and subcutaneous fat (P < .05), intermuscular fat (P < .05) kidney and channel fat (P < .05), and total side fat (P < .01) at 23.0 kg.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of lasalocid on weight gains, ruminal fermentation and forage intake of stocker cattle grazing winter wheat pasture

Fifty fall-weaned heifers with initial weights of 209 kg (yr 1) and 222 kg (yr 2) were used to determine effects of lasalocid on weight gains, forage intake and ruminal fermentation of stocker cattle grazing winter wheat pasture. The heifers grazed a single wheat pasture for about 100 d each year, and were individually fed 1.06 kg of supplement (6 d/wk) pro-rated to supply 0, 100 or 200 mg lasalocid.head-1.d-1. Also, eight mature Hereford steers with large rumen cannula were used to evaluate further effects of lasalocid (0 or 300 mg) on ruminal fermentation during two grazing periods (immature and mature wheat forage) of yr 2 and an additional third year. Daily gains of heifers fed 200 mg lasalocid/d were .11 kg greater (P less than .05) than those of heifers fed 0 or 100 mg lasalocid/d. One hundred milligrams lasalocid did not increase weight gains. Digestibilities of forage dry matter (DM) and organic matter (OM) were similar (P greater than .05) among treatments, and lasalocid did not affect (P greater than .10) forage intake. Ruminal ammonia concentrations (10.57, 15.22 and 17.81 mg/dl +/- 1.71) were increased (P less than .05) by both levels of lasalocid in yr 1, but differences among treatment means of 8.32, 11.95 and 11.66 (SE +/- 1.44) were not significant in yr 2. Lasalocid did not consistently affect total volatile fatty acids concentrations. The acetic:propionic acid ratios in heifers were not different (P greater than .05) among treatments, but were decreased (P less than .10) by lasalocid in cannulated steers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Digestion, feed intake, and live weight gain by cattle consuming bermudagrass hay supplemented with whey.

Three experiments were conducted with cattle consuming bermudagrass hay to determine whether low-level supplements of whey alone, corn alone, or whey plus corn affect feed intake, digestion, and(or) BW gain. Six ruminally and duodenally cannulated beef cows (574 kg), used in a Latin-square trial (Exp. 1), were fed bermudagrass hay without supplementation (control) or with 2.8% whey (low whey, LW), 5.6% whey (high whey, HW), 17.4% ground corn (C), 2.8% whey plus 14.9% corn (C-LW), or 5.6% whey plus 12.4% corn (C-HW). Supplementing with whey and(or) corn increased ruminal butyrate (8.8, 9.4, 10.0, 9.6, 10.5, and 11.0 mol/100 mol of total VFA for control, LW, HW, C, C-LW, and C-HW, respectively; SE = .20). Supplements did not affect microbial N flow at the duodenum. Six Holstein steer calves (158 kg) in a Latin square (Exp. 2) consumed bermudagrass hay ad libitum alone (control) or with .075 or .15% BW whey (LW and HW, respectively), .5% BW ground corn (C), or corn-whey mixes made by substituting whey for corn (C-LW and C-HW). Substituting .15% BW of whey for corn increased (P less than .05) total OM intake slightly (3.99, 3.84, 3.75, 4.11, 4.28, and 4.47 kg for control, LW, HW, C, C-LW, and C-HW, respectively; SE = .10). In an 84-d randomized block experiment (Exp. 3), 96 beef calves (194 kg) consumed (ad libitum) low-quality bermudagrass hay alone or with C, LW, HW, C-LW, or C-HW supplements.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of maternal nutrition and stage of gestation on body weight, visceral organ mass, and indices of jejunal cellularity, proliferation, and vascularity in pregnant ewe lambs

Peripubertal ewe lambs (44.3 +/- 1.1 kg of initial BW) were used in a 2 x 3 factorial design to test the effects of plane of nutrition (diet) and stage of gestation on maternal visceral tissue mass, intestinal cellularity, crypt cell proliferation, and jejunal mucosal vascularity. Singleton pregnancies to a single sire were established by embryo transfer, and thereafter ewes were offered a control (Control) or high (High) amount of a complete diet (2.84 Mcal/kg and 15.9% CP; DM basis) to promote slow or rapid maternal growth rates. After d 90 of gestation, feed intake of the Control group was adjusted weekly to maintain BCS and meet the increasing nutrient demands of the gravid uterus. Ewes were slaughtered at 50 d (n = 6 Control; n = 5 High), 90 d (n = 8 Control; n = 6 High), or 130 d (n = 8 Control; n = 6 High) of gestation. Ewes were eviscerated and masses of individual organs were recorded. The jejunum was sampled and processed for subsequent analyses. Final ewe BW for Control-fed ewes was similar at d 50 and 90 and increased (P = 0.10) from d 90 to 130 (46.0, 48.9, and 58.2 +/- 1.6 kg, respectively), whereas final BW increased (P 相似文献   

Effects of level and source of dietary selenium on maternal and fetal body weight, visceral organ mass, cellularity estimates, and jejunal vascularity in pregnant ewe lambs

Pregnant Targhee ewe lambs (n = 32; BW = 45.6 +/- 2.2 kg) were allotted randomly to 1 of 4 treatments in a completely randomized design to examine the effects of level and source of dietary Se on maternal and fetal visceral organ mass, cellularity estimates, and maternal jejunal crypt cell proliferation and vascularity. Diets contained (DM basis) either no added Se (control) or supranutritional Se from high-Se wheat at 3.0 ppm Se (SW) or from sodium selenate at 3 (S3) or 15 (S15) ppm Se. Diets were similar in CP (15.5%) and ME (2.68 Mcal/kg of DM) and were fed to meet or exceed requirements. Treatments were initiated at 50 +/- 5 d of gestation. The control, SW, S3, and S15 treatment diets provided 2.5, 75, 75, and 375 microg of Se/kg of BW, respectively. On d 134 +/- 10 of gestation, ewes were necropsied, and tissues were harvested. Contrasts, including control vs. Se treatments (SW, S3, and S15), SW vs. S3, and S3 vs. S15, were used to evaluate differences among Se levels and sources. There were no differences in ewe initial and final BW. Full viscera and liver mass (g/kg of empty BW and g/kg of maternal BW) and maternal liver protein concentration (mg/g) and content (g) were greater (P < 0.04) in Se-treated compared with control ewes. Maternal liver protein concentration was greater (P = 0.01) in SW vs. S3 ewes, and content was greater (P = 0.01) in S15 compared with S3 ewes. Maternal jejunal mucosal DNA concentration (mg/g) was greater (P = 0.08) in SW compared with S3 ewes. Total number of proliferating cells in maternal jejunal mucosa was greater (P = 0.02) in Se-fed compared with control ewes. Capillary number density within maternal jejunal tissue was greater (P = 0.08) in S3 compared with SW ewes. Selenium treatment resulted in reduced fetal heart girth (P = 0.08). Fetal kidney RNA (P = 0.04) and protein concentrations (mg/g; P = 0.03) were greater in Se-treated compared with control ewes. These results indicate that supranutritional dietary Se increases cell numbers in maternal jejunal mucosa through increased crypt cell proliferation. No indications of toxicity were observed in any of the Se treatments.     

Effects of grass species on grazing steers: I. Diet composition and ingestive mastication.

In traditional grazing trials, per animal and per hectare productivity are determined, but pasture and animal measurements are generally inadequate to address reasons for different treatment responses. This 2-yr study examined the diet and diet characteristics of steers grazing tall fescue (Festuca arundinacea Schreb.), switchgrass (Panicum virgatum L.), flaccidgrass (Pennisetum flaccidum Griseb.), and bermudagrass (Cynodon dactylon [L.] Pers.) pastures. A randomized complete block design was used with two agronomic replicates. In vitro DM disappearance (IVDMD) of masticates from tall fescue (TF), switchgrass (SG), and flaccidgrass (FG) generally were similar; all exceeded 70% (70.3 to 79.9%), except for bermudagrass (BG), which was lowest (63.5 to 65.0%). Sieving the masticate DM showed BG to contain the highest proportion (20 to 29%) of particles passing a .5-mm sieve and the lowest proportion (6 to 8%) of particles retained on a 2.8-mm sieve. This resulted in BG having the smallest mean (1.29 mm) and median (1.08 mm) particle sizes in yr 1 and a mean (1.10 mm) and median (.91 mm) particle size smaller than SG in yr 2. Except for BG, the IVDMD of the masticate DM was lowest for small particles. Canopies showed BG and SG to have the highest proportion of stem (47 and 52%, respectively); the BG canopy was composed of fractions that were consistently lowest in IVDMD. In general, BG offered the grazing animal a canopy inferior in IVDMD concentration and had canopy characteristics that limited the animals' selection of a diet with quality as high as that of TF, SG, or FG.     

Effects of zeranol and trenbolone acetate on testis function, live weight gain and carcass traits of bulls

The ability of zeranol and trenbolone acetate (trenbolone) to alter testis function, weight gain and carcass traits of young bulls was studied. In Exp. 1, the effects of age at initial zeranol implantation was determined. After a 235-d experimental period, sequential implantation (56-d intervals) beginning at 100 or 150 d of age had reduced testis growth (P less than .01), sperm production (P less than .01) and serum testosterone concentration in response to gonadotropin releasing hormone (GnRH; P less than .01). The 200-d age group was partially suppressed, while the 250-d age group was not affected. Body weights were similar to controls in all groups. In Exp. 2, bulls previously implanted with zeranol at 175 and 231 d of age received single implants of zeranol, trenbolone or trenbolone plus zeranol at approximately 300 d of age. At slaughter (135 d later), body weight and carcass characteristics in all treatments were similar to controls. However, trenbolone reduced sperm production (P less than .05), zeranol reduced sperm production and testes weight (P less than .05), but trenbolone plus zeranol was similar to controls. Mean testosterone response to GnRH was suppressed in all implant groups on d 65 (P less than .01), but only in trenbolone or trenbolone plus zeranol groups on d 112 (P less than .05). Results indicate that zeranol suppresses spermatogenesis and testosterone production if implanted before approximately 200 d of age. Reduction of endogenous testosterone without alteration of weight gain or carcass characteristics may be of benefit if behavioral or masculinity traits of bulls are altered. Also, it appears that no benefit is derived from implanting bulls with both trenbolone and zeranol.     

日粮不同能量水平对育成鸡体增质量、血液生化指标及内脏器官发育的影晌

选用60日龄体质量均匀、健康的塞北乌骨鸡120只,随机分为I～V个试验组,每个试验组设4个重复,每个组6只乌骨鸡（雌雄各半）,探讨饲粮中添加不同水平能量（10．38,10．94,11．51,12．34,12．96MJ／kg）,对塞北乌骨鸡体增质量、血液指标和免疫器官的影响。结果表明。育成期公鸡在12．34MJ／kg时体增质量最高,母鸡在12．96MJ／kg时体增质量最高;80日龄时公鸡调节血糖的能力优于母鸡,对肝脏具有很好的保护力;LDL—C与日粮能量引起体质量的变化具有一定的相关性。总胆固醇的含量在育成期随着日粮中能量水平的增加而逐渐下降。日粮能量水平不同,对内脏器官的影响也不同,都存在不同的显著性差异。