首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Two experiments were conducted to compare the performance and physiological responses of forage-fed beef females supplemented with either a molasses-based (ML) or a citrus pulp-based (CT) supplement. In Exp. 1, BW gain, reproductive performance, and concentrations of blood urea N (BUN), plasma glucose, insulin, IGF-I, and progesterone (P4) were assessed in 60 Brahman x Angus heifers supplemented 3 times weekly with either ML or CT. Supplement intakes were formulated to be isocaloric and isonitrogenous. Reproductive performance was not affected by treatments, but mean BW gain was greater (P < 0.01) for heifers fed CT than for those fed ML (0.40 vs. 0.30 kg/d). Mean plasma concentrations of glucose, insulin, and IGF-I were greater (P < 0.05) for heifers fed CT, whereas BUN was greater (P < 0.05) for heifers fed ML. Mean plasma P4 concentration did not differ between treatments, but both groups had lower plasma P4 concentrations during days that supplements were offered (P < 0.01). In Exp. 2, forage DMI and concentrations of BUN, plasma glucose, insulin, IGF-I, and P4 were assessed in 24 Brahman x British mature cows supplemented with the same treatments described in Exp. 1. Overall forage DMI did not differ between treatments, but a day effect and a treatment x day interaction were detected (P < 0.05). Both groups consumed less forage during the days on which the supplements were offered (P < 0.01), and forage DMI for cows fed CT was less (P < 0.05) than for cows fed ML during those days. No differences were detected in any blood or plasma measurement. In addition, no differences in concentrations of P4 were detected between CT- and ML-fed cows. We concluded that CT-supplemented heifers had greater BW gain compared with ML-supplemented heifers, but no differences in reproductive performance were observed. We also observed that CT-supplemented cows had a greater variability in forage DMI compared with ML-supplemented cows.  相似文献   

2.
  相似文献   

3.
Two experiments were conducted at the Kansas State University Beef Cattle Research Center to determine the effects of feeding ground flaxseed (flax) during the receiving period on the growth, health, and subsequent finishing performance of heifers. Crossbred heifers (Exp. 1: n = 363, 214 +/- 1 kg of initial BW; Exp. 2: n = 377, 222 +/- 1 kg of initial BW) were purchased during January and April of 2006. Heifers were fed receiving rations based on steam-flaked corn with 0, 2, 4, or 6% ground flax (DM basis) for 56 d. Following the receiving period, cattle in Exp. 1 and 2 were fed steam-flaked corn-based diets for 150 and 147 d, respectively, and then slaughtered. Heifers were implanted 91 and 109 d before slaughter for Exp. 1 and 2, respectively. In Exp. 1, DMI during the receiving period tended to increase linearly (P = 0.09) with increasing flax in the diet. Average daily gain was 1.46, 1.56, 1.58, and 1.61 kg for heifers fed 0, 2, 4, and 6% flax, respectively (linear, P = 0.03). Final BW in Exp. 1 after the finishing period was increased (linear, P = 0.04) with increasing inclusion of flax in the receiving diets. In Exp. 2, growth performance and mortality during the receiving period were not different among treatments (P > 0.12). During the receiving period in Exp. 2, incidence of the first respiratory treatment tended to be greatest (P = 0.09) for heifers fed 4% flax. During the finishing period, DMI were 8.4, 8.4, 8.0, and 8.1 kg/d for 0, 2, 4, and 6% flax, respectively (linear, P = 0.05). In Exp. 2, LM areas were greatest (quadratic, P = 0.04) for cattle fed 2% flax at receiving. In general, feeding flax during the receiving period may have the potential to improve growth performance; however, performance between experiments was variable, and many factors excluding flax feeding may have contributed to this response.  相似文献   

4.
Four experiments were conducted to clarify the effect of intravenous (i.v.) administration of recombinant bovine tumor necrosis factor alpha (rbTNF) on selected metabolites and on hormone secretion in Holstein heifers (n = 6; 347.0 kg average BW). In Exp. 1, rbTNF was injected at three dosage levels in a Latin square; 0 (CONT), 2.5 (TNF2.5), or 5.0 (TNF5) microg/kg BW. Plasma glucose and triglyceride concentrations were at first elevated (P < .05) by rbTNF treatment and then were decreased (P < .05) by TNF2.5 and TNF5. Plasma NEFA concentrations were increased (P < .05) in rbTNF-treated groups. The injection of rbTNF resulted in an increase in plasma insulin levels (P < .05 with TNF5) during the period between 2 and 24 h, except for the period between 6 and 8 h, after the treatment. In Exp. 2, 3, and 4, each heifer received i.v. injections of glucose (.625 mM/kg BW) + rbTNF (5 microg/kg) or glucose + saline (10 mL) (Exp. 2), insulin (0.2 U/kg) + rbTNF or insulin + saline (Exp. 3), and GHRH (0.25 microg/kg) + rbTNF or GHRH + saline (Exp. 4) at 1-wk intervals. In Exp. 2, rbTNF inhibited (P < .05) glucose-stimulated insulin secretion during the initial phase. Thereafter, plasma insulin was higher (P < .01) with the glucose + rbTNF treatment than with the glucose + saline treatment. Treatment with rbTNF inhibited the insulin-stimulated glucose utilization (Exp. 3) and GHRH-stimulated GH secretion (Exp. 4) during the initial phase. These results suggest that rbTNF directly and(or) indirectly affects the intermediary metabolism and hormone secretion in Holstein heifers.  相似文献   

5.
The effects of somatotropin (STH) and energy intake on serum concentrations of glucose (GLU), insulin (INS), nonesterified fatty acids (NEFA), urea nitrogen (UN) and insulin-like growth factor-I (IGF-I) were determined in 40 Angus heifers. At 7 mo (208 +/- 8 d) of age heifers were assigned to four treatment groups: 1) vehicle (V) + high energy (HE; 2.68 Mcal ME/kg DM), 2) recombinant DNA-derived STH (20.6 mg/d; s.c.) + HE, 3) V + low energy (LE; 2.22 Mcal ME/kg DM) or 4) STH + LE. Animals remained on treatments until an average of 15.5 mo of age. Blood samples were taken every 30 min for 4 h at 9, 11, 13 and 15 mo of age to determine circulating concentrations of metabolites and hormones. Serum IGF-I was increased (P less than .01) by STH injections, but this effect appeared to diminish with age (STH x age; P less than .01). Energy intake did not influence IGF-I levels. Somatotropin increased (P less than .01) serum GLU in heifers fed the HE diet but only tended (P = .08) to increase GLU in those fed the LE diet (STH x energy; P = .05). Although STH increased (P less than .01) serum INS in both energy groups, the response in heifers fed the HE diet was greater (P less than .02) than that in heifers fed the LE diet (STH x energy; P less than .05). Heifers fed LE had higher (P less than .01) concentrations of NEFA than heifers fed HE.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

6.
Six hundred sixty-five crossbred beef heifers initially weighing 225 kg were used in a completely randomized design to measure plasma glucose, lactate, and urea N concentrations at time of initial processing, determine the incidence of apparent bovine respiratory disease (BRD) in receiving cattle, and evaluate the effect of apparent BRD on subsequent cattle growth and carcass characteristics. Heifers were processed within 24 h of arrival, and processing included vaccination against common viral and clostridial diseases, recording rectal temperature, and sampling whole blood for subsequent measurement of plasma glucose, lactate, and urea concentrations. Heifers were monitored for clinical signs of apparent BRD, including depression, lethargy, anorexia, coughing, rapid breathing, and nasal or ocular discharge. Heifers exhibiting signs of apparent BRD received antibiotic therapy, and the number of times a heifer was treated for apparent BRD was recorded. Following the 36-d receiving period, heifers were transported to native grass pastures and allowed to graze for 136 d. At the end of the grazing season, heifers were transported to a commercial feedlot where they were adapted to a common finishing diet offered for ad libitum consumption. Following the 124-d finishing period, heifers were slaughtered and carcass data were collected. Heifers treated for apparent BRD had decreased plasma glucose (linear, P < 0.01), lactate (linear, P < 0.01), and urea N concentrations (linear, P < 0.06) measured at time of initial processing. Rectal temperature measured at time of initial processing tended to be greater (linear, P < 0.11) for heifers treated for apparent BRD. Heifers treated for apparent BRD during the receiving period had decreased overall ADG (linear, P < 0.10), final BW (linear, P < 0.01), HCW (linear, P < 0.01), fat thickness (linear, P < 0.01), and marbling score (linear, P < 0.03). These data suggest that initial plasma glucose and lactate concentrations might be affected by the health status of receiving cattle and that increased incidence of apparent BRD in cattle decreases ADG and carcass quality.  相似文献   

7.
The objective of this study was to determine the relationships among plasma concentrations of leptin, insulin, and IGF-I with dynamic changes in body condition scores (BCS) in heifers. Nineteen Zebu-Brown Swiss crossbred heifers, 24 to 30 mo old, weighing 322 +/- 9 kg, and with an initial BCS of 2.6 +/- 0.11 (range = 1 to 9) were used. Heifers were fed 60% of their maintenance requirements until they reached a BCS of < or = 2. Heifers were then maintained at that level for 25 d, after which they were fed to gain 1 kg of body weight daily until a BCS of 6 was reached. Heifers were weighed weekly and BCS was measured every 2 wk. Plasma samples were collected twice weekly, and leptin and insulin were determined by RIA. An immunoradiometric assay was used to measure IGF-I from one sample every 2 wk. Plasma concentrations of leptin were positively correlated during nutritional restriction (NR) and weight gain (WG) periods with BCS (r = 0.47 for NR, and r = 0.83 for WG; P < 0.01) and body weight (r = 0.40 for NR, and r = 0.78 for WG; P < 0.01). Plasma concentrations of leptin decreased during nutritional restriction (P < 0.01) as BCS decreased. During weight gain, leptin concentration increased at BCS 3 and thereafter for each integer change in the BCS. Regression analysis showed that changes in body weight affect leptin concentrations within a given BCS. There was a decrease in IGF-I as BCS declined (P < 0.01). During weight gain, by contrast, IGF-I increased significantly (P < 0.01) with every unit change in body condition up to BCS of 4 and plateaued thereafter. Insulin concentrations did not change during nutritional restriction when BCS decreased from 3 to 1. However, once the diet was improved, there was a large increase in insulin concentrations in heifers with BCS 1 (P < 0.01). Among heifers of BCS 2 and 3, insulin did not differ and was lower than in heifers of BCS 1 (P < 0.01). Insulin increased (P < 0.01) among heifers at BCS 4 to 6. Leptin was positively correlated (P < 0.01) with both IGF-I (r = 0.34 for NR, and r = 0.36 for WG) and insulin (r = 0.18 for WG). Insulin was correlated with IGF-I (r = 0.60; P < 0.01). During nutritional restriction, insulin did not correlate with leptin (r = -0.05), BCS (r = -0.03), or IGF-I (r = 0.07). It was concluded that leptin serves as a dynamic indicator of body condition in heifers, as well as an indicator of nutritional status.  相似文献   

8.
The objective of this study was to compare performance, physiological, and reproductive responses of beef heifers consuming forages differing in nutritional quality and offered a low-starch energy supplement at 2 different frequencies. Forty-eight Brahman × British heifers (initial age = 294 ± 3 d) were allocated into 1 of 16 drylot pens (3 heifers/pen) which were randomly assigned to receive, in a 2 × 2 factorial arrangement of treatments: 1) low-quality hay [LQ; stargrass (Cynodon nlemfuensis) with 8% CP and 81% NDF, DM basis] and daily supplementation (S7); 2) LQ and supplementation 3 times weekly (S3); 3) medium-quality hay [MQ; bermudagrass (C. dactylon) with 12% CP and 74% NDF, DM basis] and S7; and 4) MQ and S3. Throughout the study (d 0 to 120), hay was offered in amounts to ensure ad libitum access, and a supplement based on soybean hulls and wheat middlings was offered at weekly rates of 15.8 and 7.9 kg/heifer (DM basis) for LQ and MQ, respectively. Forage and total DMI were evaluated daily, from d 20 to 26, d 34 to 40, and d 48 to 54. Blood samples were collected weekly for determination of plasma progesterone to evaluate puberty attainment. Blood samples were also collected daily, from d 13 to 16, d 27 to 30, d 41 to 44, and d 55 to 58 for determination of plasma urea nitrogen (PUN), glucose, insulin, IGF-I, and NEFA. On d 60, heifers were reallocated by treatment into 4 paddocks and exposed to Angus bulls (1:12 bull:heifer ratio) until d 120. Date of conception was estimated retrospectively by subtracting gestation length (286 d) from the calving date. Heifers receiving S7 had similar (P = 0.52) ADG compared with S3 heifers (0.27 vs. 0.25 kg/d). Heifers provided S7 had less daily variation in hay DMI and plasma concentrations of glucose, NEFA, and IGF-I compared with S3 cohorts (supplementation frequency × day interaction; P < 0.01). Similarly, heifers offered MQ and LQ and receiving S7 had less daily variation in total DMI, energy and protein intake, and plasma concentrations of PUN compared with heifers offered MQ and LQ and receiving S3 (hay quality × supplementation frequency × day interaction; P < 0.01). Attainment of puberty and pregnancy were hastened in S7 heifers compared with S3 heifers (supplementation frequency × week interaction; P < 0.02). Therefore, reproductive development of beef replacement heifers consuming diets based on low- and medium-quality forages are enhanced when low-starch energy supplements are offered daily instead of 3 times weekly.  相似文献   

9.
In experiment 1, nine light horse geldings (three 3 x 3 Latin squares) received dexamethasone (DEX; 125 microg/kg BW, i.m.), glucose (0.2 g/kg BW, i.v.), or nothing (control) once per day for 4 days. DEX increased (P < 0.001) glucose, insulin, and leptin concentrations and resulted in a delayed increase (P < 0.001) in IGF-I concentrations. In experiment 2, mares were similarly treated with DEX (n = 6) or vehicle (n = 6). DEX again increased (P < 0.01) glucose, insulin, and leptin concentrations; the delayed elevation in IGF-I concentrations occurred on day 10, 12, and 19, relative to the first day of treatment. In experiment 3, six light horse geldings received either 200 IU of adrenocorticotropin (ACTH) i.m. or vehicle twice daily for 4 days. ACTH increased (P < 0.001) cortisol concentrations. Further, ACTH resulted in increases (P < 0.01) glucose, insulin, and leptin concentrations. In experiment 4, plasma samples from four light horse stallions that were fed 6-n-propyl-2-thiouracil (PTU) at 6 mg/kg BW for 60 days to induce hypothyroidism were compared to samples from control stallions. On day 52, stallions receiving PTU had lower concentrations of thyroxine (P < 0.05) and triiodothyronine (P < 0.01) and higher (P < 0.01) concentrations of TSH. Leptin concentrations were higher (P < 0.01) in PTU-fed stallions from day 10 through 52. In conclusion, circulating concentrations of leptin in horses was increased by administering DEX. Treatment with ACTH increased cortisol and resulted in lesser increases in leptin, glucose, and insulin. In addition, PTU feeding results in lesser increases in leptin concentrations.  相似文献   

10.
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.  相似文献   

11.
We studied effects of protein intake at two protein-free energy intake levels on plasma glucose and insulin concentrations, urinary glucose excretion and on liver and intestinal fat content in milk-fed veal calves. Two experiments were performed at body weights (BW) of 80-160 kg (mean 120 kg; Exp. 1) and 160-240 kg (mean 200 kg; Exp. 2). In each experiment, 36 calves were allocated to one of six protein intake levels, at each of two energy intake levels. Digestible protein intakes ranged between 0.90 and 2.72 g nitrogen (N)/(kg BW(0.75) x d) in Exp. 1 and between 0.54 and 2.22 g N/(kg BW(0.75)x d) in Exp. 2. The two energy intake levels were kept constant on a protein-free basis and were 663 and 851 kJ/(kg BW(0.75) x d) in Exp. 1 and 564 and 752 kJ/(kg BW(0.75)x d) in Exp. 2. Blood samples were taken between 5 and 6h post-feeding at 14-d intervals until calves reached target BW, and liver fat mass was determined at slaughter. Urinary glucose excretion was quantified at 120 and 200 kg BW in Exps. 1 and 2, respectively. Increased protein-free energy intake increased plasma glucose concentrations and urinary glucose losses in 200 kg calves, but not in 120 kg calves. Increasing protein intake decreased plasma glucose, urinary glucose and plasma insulin in both experiments. Liver fat content decreased with increasing protein intake. In conclusion, long-term low-dietary protein intake increased hyperglycemia, hyperinsulinemia, glucosuria and hepatic steatosis in heavy milk-fed calves, likely associated with increased insulin resistance.  相似文献   

12.
The objective of this study was to determine if alterations in dietary intake of heifers can influence IGF-I concentrations in plasma and(or) follicular fluid (FFL), size of follicles, and steroid concentrations in FFL (as an indicator of steroidogenic capacity). Cyclic heifers [n = 23; mean +/- SE body weight (BW) = 373 +/- 7 kg] were individually fed for 10 weeks either: a) 1.8% of BW in dry matter (DM) per d (GAIN; n = 7), b) 1.1% of BW in DM per d (MAINT; n = 8) or c) 0.7% of BW in DM per d (LOSE; n = 8). After 10 wk of treatment, heifers were ovariectomized 36-40 hr after the second injection of prostaglandin F2 alpha analog (2 injections 11 d apart), and plasma and ovaries were collected. Heifers weighed 444 +/- 13,387 +/- 8 and 349 +/- 9 kg in the GAIN, MAINT and LOSE groups, respectively, at time of ovariectomy. Mean diameter of follicles greater than or equal to 10 mm was greater (P less than .05) for GAIN (15.6 mm) than for MAINT (11.0 mm) or LOSE (12.5 mm) heifers. Numbers of follicles and concentrations of IGF-I in plasma and FFL did not differ (P greater than .20) between LOSE, MAINT and GAIN heifers. Progesterone concentrations were greater (P less than .05) in small and medium follicles of GAIN than MAINT or LOSE heifers, but were unaffected by diet in large follicles. Estradiol concentrations in FFL in small, medium and large follicles were unaffected (P greater than .20) by dietary treatment.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

13.
Two experiments were conducted to evaluate the effects of Cu and Zn source on performance, morbidity, and humoral immune response in lightweight, newly received beef heifers. A 2 x 2 factorial arrangement of treatments was used in both experiments, with either a sulfate or a polysaccharide mineral complex (SQM) source of both Cu and Zn as the factors. Supplemental Cu and Zn were included in the receiving diet at concentrations designed to provide 10 mg of Cu/kg and 75 mg of Zn/kg (DM basis). In Exp. 1, 219 newly received beef heifers (British x Continental, average initial BW = 208 kg) were given ad libitum access to a 65% concentrate diet for 35 d to determine treatment effects on DMI, ADG, G:F, and bovine respiratory disease (BRD) morbidity. In Exp. 2, 24 heifers (average initial BW = 272 kg) were fed a diet with no supplemental Cu or Zn for 35 d, followed by fasting-refeeding-fasting stress, after which the same treatment diets used in Exp. 1 were fed for 21 d to examine the effects on humoral immune response (plasma IgG titer determined by ELISA on d 7, 14, and 21) to an ovalbumin (OVA) vaccine given on d 0 and 14. Copper source x Zn source interactions were not detected in either experiment. In Exp. 1, neither Cu nor Zn source affected (P > 0.10) DMI, ADG, G:F, or BRD morbidity. In Exp. 2, d 14 (P = 0.02) and 21 (P = 0.06) OVA titers were greater for heifers that received SQM Zn compared with heifers receiving ZnSO4, but heifers receiving CuSO4 had greater OVA titers than did heifers on the SQM Cu treatment on d 14 (P = 0.01) and 21 (P = 0.001). In summary, neither supplemental Cu nor Zn source affected performance or morbidity of lightweight, newly received heifers; however, source of both Cu or Zn affected the humoral immune response to OVA, although source effects were not consistent for the two minerals.  相似文献   

14.
The primary objective of this study was to investigate the impact of animal-level factors including energy balance and environmental/management stress, on the ovarian function of Bos indicus heifers treated to synchronize ovulation. Two-year-old Brahman (BN) (n = 30) and BN-cross (n = 34) heifers were randomly allocated to three intravaginal progesterone-releasing device (IPRD) treatment groups: (i) standard-dose IPRD [Cue-Mate(?) (CM) 1.56 g; n = 17]; (ii) half-dose IPRD [0.78 g progesterone (P(4)); CM 0.78 g; n = 15]; (iii) half-dose IPRD + 300 IU equine chorionic gonadotrophin at IPRD removal (CM 0.78 g + G; n = 14); (iv) and a control group, 2× PGF(2α) [500 μg prostaglandin F(2α) (PGF(2α))] on Day -16 and -2 (n = 18). Intravaginal progesterone-releasing device-treated heifers received 250 μg PGF(2α) at IPRD insertion (Day -10) and IPRD removal (Day -2) and 1 mg oestradiol benzoate on Day -10 and -1. Heifers were managed in a small feedlot and fed a defined ration. Ovarian function was evaluated by ultrasonography and plasma P(4) throughout the synchronized and return cycles. Energy balance was evaluated using plasma insulin-like growth factor 1 (IGF-I) and glucose concentrations. The impact of environmental stressors was evaluated using plasma cortisol concentration. Heifers that had normal ovarian function had significantly higher IGF-I concentrations at commencement of the experiment (p = 0.008) and significantly higher plasma glucose concentrations at Day -2 (p = 0.040) and Day 4 (p = 0.043), than heifers with abnormal ovarian function. There was no difference between the mean pre-ovulatory cortisol concentrations of heifers that ovulated or did not ovulate. However, heifers that ovulated had higher cortisol concentrations at Day 4 (p = 0.056) and 6 (p = 0.026) after ovulation than heifers that did not ovulate.  相似文献   

15.
Effects of bovine respiratory disease (BRD) on stocker cattle systems are unknown under extensive rangeland environments. Three experiments were conducted to test the hypothesis that BRD-based morbidity is a major factor affecting the productivity and profitability of stocker cattle grazing Southern Plains rangelands. In Exp. 1 (658 male calves; average BW = 231 kg), 17% of the cattle were treated for BRD <8 d, 6% for 8 to 14 d, and 8% for >14 d. Morbid cattle had lower ADG than did healthy cattle (P < 0.10). Cattle requiring 14 d of pharmaceutical therapy gained less than cattle having <14 d therapy (P < 0.01). In Exp. 2, (279 steers and bulls; average BW = 216 kg), the ADG by steers (0.74 kg x animal(-1) x d(-1)) was greater (P < 0.05) than by bulls castrated after arrival (0.64 kg x animal(-1) x d(-1)). Castration after arrival led to a 13.5% loss in daily gain and a 10.3% loss in season-long gain. More (P < 0.05) bulls castrated after arrival (60%) were morbid compared with steers (28%). In Exp. 3, 633 heifers (average BW = 251 kg) were used to test the effects of morbidity on weight gain and reproduction. Heifers with lower initial weights exhibited increased (P < 0.05) morbidity. Heifers requiring two or more antibiotic treatments gained 0.03 kg/d less (P < 0.10) than did healthy heifers and had lower (P < 0.05) conception rates (66 vs. 81%). Conception rate in twice-treated heifers was 19% less than healthy heifers. Morbid heifers conceived 0.6 mo later (P < 0.05) than healthy heifers. Under the conditions of Exp. 1 and Exp. 2, morbidity decreased net returns 9.7 to 21.3% per animal. Adjusted gross returns per animal in Exp. 3 for replacement heifers were 3 to 7.8% less for morbid heifers.  相似文献   

16.
Two experiments were conducted to evaluate receiving-period performance, morbidity, and humoral immune response, as well as finishing performance and carcass characteristics of heifers fed different sources of supplemental Zn. In Exp. 1, 97 crossbred beef heifers (initial BW = 223.4 kg) were fed a 65% concentrate diet with no supplemental Zn (control) or 75 mg of supplemental Zn/kg of DM from Zn sulfate, Zn methionine, or Zn propionate. During a 35-d receiving period, heifers were monitored daily for signs of bovine respiratory disease. Serum samples were collected for Zn analysis on d 0, 14, and 28. After the receiving period, heifers were adapted to and fed a high-concentrate diet with no supplemental Zn for 42 d. Heifers were then assigned to finishing diet treatments, with the same concentrations and sources of supplemental Zn as during the receiving period and fed for an average of 168 d. Serum samples also were obtained on d 0 and 56 of the finishing period and at the end of the study. During the receiving period, control heifers had a greater (P < or = 0.05) BW and G:F on d 35 than heifers in the other treatments, but no differences were observed among treatments for morbidity or serum Zn concentrations (P > or = 0.50). For the finishing period, DMI and ADG did not differ among treatments; however, overall G:F tended (P = 0.06) to be less for control heifers than for heifers in the 3 supplemental Zn treatments. On d 56 of the finishing period, control heifers tended (P = 0.06) to have a lower serum Zn concentration than heifers in the 3 supplemental Zn treatments. In Exp. 2, 24 crossbred beef heifers (initial BW = 291.1 kg) were fed the same 4 treatments as in Exp. 1 for a 21-d period. The humoral immune response to treatments was determined by measuring specific antibody titers after s.c. injection of ovalbumin on d 0 and 14. Body weights and blood samples for serum Zn concentration and ovalbumin IgG titers were collected on d 0, 7, 14, and 21. Serum Zn concentration and specific ovalbumin IgG titers did not differ (P > 0.10) among the 4 treatments on any sampling day. Results from these 2 studies showed no major differences among the sources of supplemental Zn for receiving period morbidity, ADG, DMI, and humoral immune response of beef heifers; however, a lack of supplemental Zn during an extended finishing period tended to negatively affect G:F.  相似文献   

17.
The objective of these experiments was to establish the relationship of plasma ghrelin concentrations with feed intake and hormones indicative of nutritional state of cattle. In Exp.1, 4 steers (BW 450 +/- 14.3 kg) were used in a crossover design to compare plasma ghrelin concentrations of feed-deprived steers with those of steers allowed to consume feed and to establish the relationship of plasma ghrelin concentrations with those of GH, insulin (INS), glucose (GLU), and NEFA. After adaptation to a once-daily feed offering (0800), 2 steers continued the once-daily feeding schedule (FED), whereas feed was withheld from the other 2 steers (FAST). Serial blood samples were collected via indwelling jugular catheter from times equivalent to 22 h through 48 h of feed deprivation. Average plasma ghrelin concentrations were greater (P < 0.001) in FAST compared with FED (690 and 123 +/- 6.5 pg/mL) steers. Average plasma ghrelin concentrations for FED steers prefeeding were elevated (P < 0.001) when compared with those postfeeding (174 and 102 +/- 4.2 pg/mL, respectively). Average plasma GH concentration was elevated (P < 0.05) for FAST steers compared with FED steers. Plasma GLU concentrations were not different; however, for FAST steers, NEFA concentrations were elevated (P < 0.001) and INS concentrations were decreased (P < 0.001). In Exp. 2, 4 steers (BW 416 +/- 17.2 kg) were used in a crossover design to determine the effects of i.v. injection of bovine ghrelin (bGR) on plasma GH, INS, GLU, and NEFA concentrations; length of time spent eating; and DMI. Steers were offered feed once daily (0800). Serial blood samples were collected from steers via indwelling jugular catheter. Saline or bGR was injected via jugular catheter at 1200 and 1400. A dosage of 0.08 microg/kg of BW bGR was used to achieve a plasma ghrelin concentration similar to the physiological concentration measured in a FAST steer in Exp. 1 (1,000 pg/mL). Injection of bGR resulted in elevated (P < 0.005) plasma GH concentrations after the 1200 but not the 1400 injection. Plasma INS, GLU, and NEFA concentrations were not affected by bGR injection. For the combined 1-h periods postinjection, length of time spent eating was greater (P = 0.02) and DMI tended to be increased (P = 0.06) for bGR steers. These data are consistent with the hypothesis that ghrelin serves as a metabolic signal for feed intake or energy balance in ruminants.  相似文献   

18.
Three experiments were conducted to evaluate the response of supplementing primiparous heifers based on the metabolizable protein (MP) system during pregnancy and lactation. In Exp. 1, 12 pregnant, March-calving heifers (432 +/- 10 kg) grazing Sandhills range were randomly allotted to one of two treatments: supplementation based on either the MP system (MPR) or the CP system (CPR). Supplements were fed to individual heifers from October to February and no hay was offered. Grazed forage organic matter intake (FOMI) was measured in November, January, and February. In Exp. 2, 18 heifers (424 +/- 8 kg) were randomly allotted to one of three treatments: 1) supplementation based on the MP system with hay fed in January and February (average 2.0 kg/d; MPR/hay), 2) supplementation based on the CP system, with hay fed in January and February (CPR/hay), or 3) supplementation based on the MP system, with no hay fed (MPR/no hay). Supplements were fed from October to February, and FOMI was measured in December and February. In Exp. 3, lactating 2-yr-old cows (394 +/- 7 kg) maintained on meadow hay were supplemented to meet either 1) MP requirements (LMPR) or 2) degradable intake protein requirements (LDIPR). Body weight (BW) and body condition score change, hay intake, and milk production were measured. In Exp. 1, grazed FOMI decreased (P = 0.0001) from 1.9% of BW in November to 1.2% in February, but no differences among treatments were detected for FOMI or BW change. In Exp. 2, grazed FOMI declined (P = 0.0001) from 1.7% of BW in December to 1.1% in February, with no differences among treatments. Heifers on the MPR/hay and CPR/hay treatments had higher (P = 0.0018) total intake (grazed forage + hay intake) in February (1.7% BW) than the MPR/no hay heifers (1.1% BW). Heifers on the MPR/no hay treatment had a lower weight (P = 0.02) and tended (P = 0.11) to have a lower BCS than heifers on other treatments. In Exp. 3, the LMPR cows had higher (P = 0.02) ADG than LDIPR cows (0.41 and 0.14, respectively), but treatment did not affect milk production. Organic matter hay intake averaged 2.4% of BW. We conclude that supplementation to meet MP requirements had little benefit to heifer performance during gestation, but increased weight change during lactation. Because grazed forage intake decreased from 1.9 to 1.1% of BW with advancing gestation, supplemental energy is necessary to reduce weight and condition loss of gestating hefiers grazing dormant Sandhills range.  相似文献   

19.
Serum concentrations of leptin increase linearly from approximately 16 wk before until the week of pubertal ovulation in beef heifers. To test the hypothesis that exogenous leptin can hasten the onset of puberty in heifers, we examined the effects of chronic administration of recombinant ovine leptin (oleptin) on timing of puberty, pulsatile and GnRH-mediated release of LH, and plasma concentrations of GH, IGF-I, and insulin. Fourteen fall-born, prepubertal heifers (Brahman x Hereford, 12 to 13 mo; 304.7+/-4.12 kg) were used. Heifers were stratified by age and BW and assigned randomly to one of two groups (seven animals per group): 1) Control; heifers received s.c. injections of saline twice daily (0700 and 1900) for 40 d; and 2) Leptin; heifers received s.c. injections of oleptin (19.2 microg/kg) twice daily at 0700 and 1900 for 40 d. Blood samples were collected at 10-min intervals for 5 h on. d 0, 5, 10, 20, 30, and 40, and twice daily, just before each treatment injection, throughout the study. On d 41, heifers received i.v. injections of GnRH at 0 (0.0011 microg/kg) and 90 min (0.22 microg/kg), with additional sampling for 5.5 h to examine releasable pools of LH. Diets promoted a gain of 0.32+/-0.09 kg/d, which did not differ between groups. Plasma concentrations of leptin increased markedly in leptin-treated heifers and were greater (P < 0.001) than controls throughout (27.8+/-0.8 vs. 4.9+/-0.12 ng/mL). None of the heifers reached puberty during the experiment, but did so within 45 d of its termination. Mean concentrations of plasma LH, GH, IGF-I, and insulin were not affected by treatment, nor was there an overall effect on the frequency of LH pulses. However, a treatment x day interaction (P = 0.02) revealed that the frequency of LH pulses (pulses/ 5 h) was greater (P = 0.03) in controls (3.6+/-0.36) than in leptin-treated heifers (1.7+/- 0.28) on d 10. Characteristics of GnRH-induced release of LH were not affected by treatment. In summary, chronically administered leptin failed to induce puberty or alter endocrine characteristics in beef heifers nearing the time of expected puberty.  相似文献   

20.
One hundred twelve crossbred feedlot heifers were used in two experiments to assess the impact of heat stress and its relief by shade and(or) water misting on behavior, physiology, performance, and carcass traits. Treatments were 1) no shading or misting (CONT); 2) only misting (MIST); 3) only shading (SHADE); and 4) shading plus misting (SHMI). Head in the feed bunk, head in or above the waterer, walking, standing, and lying behaviors were observed. Rectal temperature, respiration rate, and carcass traits were measured, as well as DMI, ADG, and feed:gain. Dietary NEm and NEg concentrations were calculated from performance data. In Exp. 1, (32 heifers; average BW 288 kg) the CONT heifers spent more time lying down than all others (P < 0.01). In addition, CONT heifers spent less time (P < 0.01) standing than SHADE and MIST heifers. Misting decreased (P < 0.01) rectal temperature and MIST as well as SHADE lowered (P < 0.05) respiration rates. In Exp. 2 (80 heifers; average BW = 336 kg), lying and walking behaviors did not differ among treatments, but shade increased (P < 0.01) standing behavior in heifers. The MIST cattle performed less (P < 0.05) head-above-water behavior than unmisted cattle. Rectal temperatures did not differ among treatments, but respiration rate was lower in shaded than in unshaded heifers (P < 0.05). Shaded compared with unshaded heifers had greater DMI (9.46 vs 8.80 +/- 0.14 kg/d, P < 0.01) and ADG (1.6 vs 1.41 +/- 0.1 kg/d, P < 0.01). Heifers provided with shade reached their target BW 20 d earlier than the unshaded heifers and differed in final BW (547 vs 520 +/- 6 kg, P < 0.01). Feed:gain and calculated NEg and NEm concentrations did not differ among treatments, and carcass traits were generally similar among treatments. In conclusion, cattle without shade had a physiological and behavioral stress response to heat that negatively affected productivity. Providing shade for beef cattle was a suitable solution to decrease heat stress and to lower the negative effects of heat on performance, whereas misting was largely ineffective.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号