Effects of feeding diets containing endophyte-infected fescue seed on luteinizing hormone secretion in postpartum beef cows and in cyclic heifers and cows.

Two experiments were conducted to investigate the effect of feeding endophyte (Acremonium coenophialum)-infected fescue (Festuca arundinacea Shreb.) seed on LH secretion in postpartum beef cows and in cycling heifers and cows. In Exp. 1, spring-calving primiparous Angus cows (n = 16) were pair-fed for 75 d diets that contained endophyte-free or endophyte-infected (95%) fescue seed that contained 1.3 micrograms/g of ergovaline and 5.2 mg/g of saturated pyrrolizidines. Serial blood samples for basal and GnRH-stimulated serum LH analysis were obtained on d 7, 28, 42, and 56 of the study. The endophyte had no effect on LH secretion (basal, pulse frequency, and amplitude) or milk production. Average daily gain was decreased (P < .05) in cows that consumed infected fescue seed compared with controls (-.20 vs -.01 kg, respectively). Basal serum prolactin concentrations were reduced (P < .01) in treated compared with control cows (8.9 vs 25.4 ng/mL, respectively) on d 70. In Exp. 2, cycling Angus heifers (n = 8; age = 2 yr) and cows (n = 8; age = 4 yr) stratified by age were pair-fed for 40 d diets that contained the noninfected or the highly infected fescue seed. Estrus was synchronized by prostaglandin F2 alpha (d 18 and 28). Serial blood samples for serum LH analysis were obtained on d 28 (luteal phase) and d 30 (follicular phase). The endophyte did not affect LH (P > .28) or prolactin (P > .16) secretion, whereas ADG was decreased (P < .05) in treated compared with control animals (.32 vs .70 kg/d, respectively).     

Physiological and digestive effects of Neotyphodium coenophialum-infected tall fescue fed to lambs

The digestive responses and degradation of ergovaline and production of lysergic acid in the rumen of sheep offered Neotyphodium coenophialum-infected tall fescue straw at 2 ergovaline levels were investigated. Six crossbred wethers (56 +/- 3.0 kg of BW) were used in a randomized crossover design involving 2 treatments, for a total of 6 observations per treatment. The experiment consisted of two 28-d feeding periods with a 14-d washout period between them. The treatments were 1) tall fescue straw containing <0.010 mg of ergovaline/kg (E-), and 2) tall fescue straw containing 0.610 mg of ergovaline/kg (E+). Feed, orts, and feces were measured and analyzed for DM, ADF, and CP, and used to determine digestibilities. Feed and water intake were monitored throughout the feeding periods. Body weight and serum prolactin levels were measured at the beginning and end of each feeding period. Ruminal fluid was sampled 3 times (d 0, 3, and 28) during each 28-d feeding period for determination of ergovaline, lysergic acid, ammonia, and pH. Samples were collected before feeding (0 h) and at 6 and 12 h after feeding. Total fecal and urine collection commenced on d 21 and continued until d 25 of each feeding period. Ruminal ammonia, ruminal pH, and rectal temperature were not influenced by ergovaline concentration (P > 0.10). Digestion of DM, ADF, and CP was not different between treatments (P > 0.10). Daily water intake was less for the E+ diet (2.95 vs. 2.77 L/d; P < 0.05) as was serum prolactin (22.9 vs. 6.4 ng/mL; P < 0.05). Ergovaline concentration in ruminal fluid increased over sampling days at each sampling time (P < 0.05). Lysergic acid concentration in ruminal fluid increased over time from d 0 to 3 (P < 0.05) but was not different between d 3 and 28 (P > 0.10). In the E+ treatment, ergovaline was not detectable in the urine, whereas the concentration in the feces was 0.480 mg/kg. Lysergic acid was detected in the diet of the E+ treatment at 0.041 g/kg, lysergic acid in the urine was 0.067 mg/kg and in the feces was 0.102 mg/kg. The apparent digestibility of the alkaloids was 64.2% for ergovaline and -12.5% for lysergic acid. Approximately 35% of dietary ergovaline and 248% of dietary lysergic acid were recovered in the feces and urine. The appearance of lysergic acid in the feces, urine, and ruminal fluid is likely due to microbial degradation of ergovaline in the rumen and further breakdown in the lower digestive tract.     

Daily and alternate day supplementation of urea or biuret to ruminants consuming low-quality forage: I. Effects on cow performance and the efficiency of nitrogen use in wethers

Two experiments were conducted to determine the influence of supplemental nonprotein N (NPN) provided daily (D) or every other day (2D) on ruminant performance and N efficiency. Treatments included an unsupplemented control (CON) and a urea (28.7% CP) or biuret (28.6% CP) supplement provided D or 2D at 0700. In Exp. 1, five wethers (39 +/- 1 kg BW) were used in an incomplete 5 x 4 Latin square with four 24-d periods to determine the influence of supplemental NPN source and supplementation frequency (SF) on the efficiency of N use in lambs consuming low-quality grass straw (4% CP). The amount of CP supplied by each supplement was approximately 0.10% of BW/d (averaged over a 2-d period). In Exp. 2, 80 Angus x Hereford cows (540 +/- 8 kg BW) in the last third of gestation were used to determine the effect of NPN source and SF on cow performance. The NPN treatments were formulated to provide 90% of the estimated degradable intake protein requirement. The supplemented treatments received the same amount of supplemental N over a 2-d period; therefore, the 2D treatments received double the quantity of supplemental N on their respective supplementation day than the D treatments. In Exp. 1, total DM, OM, and N intake; DM, OM, and N digestibility; N balance; and digested N retained were greater (P < 0.03) for supplemented than for CON wethers, with no difference (P > 0.05) between NPN sources or SF. Plasma urea-N (PUN) was increased with N supplementation compared with CON (P < 0.01), and urea treatments had greater PUN than biuret (P < 0.01). In addition, PUN was greater (P = 0.02) for D than for 2D treatments. In Exp. 2, pre- and postcalving (within 14 d and 24 h after calving, respectively) cow weight and body condition score change were more positive (P < 0.05) for supplemented groups than for CON. These results suggest that supplements containing urea or biuret as the primary source of supplemental N can be effectively used by lambs and cows consuming low-quality forage, even when provided every other day.     

Effects of prepartum supplementation of linoleic and mid-oleic sunflower seed on cow performance, cow reproduction, and calf performance from birth through slaughter, and effects on intake and digestion in steers

Two experiments were conducted to determine the effects of sunflower seed supplements with varying fatty acid profiles on performance, reproduction, intake, and digestion in beef cattle. In Exp. 1, 127 multiparous spring-calving beef cows with free-choice access to bermudagrass hay were individually fed 1 of 3 supplements for an average of 83 d during mid to late gestation. Supplements (DM basis) included 1) 1.23 kg/d of a soybean hull-based supplement (control treatment); 2) 0.68 kg/d of linoleic sunflower seed plus 0.23 kg/d of the control supplement (linoleic treatment); and 3) 0.64 kg/d of mid-oleic sunflower seed plus 0.23 kg/d of the control supplement (oleic treatment). During the first 62 d of supplementation, the BW change was 11, 3, and -3 kg for cows fed the control, linoleic, and oleic supplements, respectively (P < 0.001). No difference in BW change was observed during the subsequent period (-65 kg, P = 0.83) or during the entire 303-d experiment (-31 kg, P = 0.49). During the first 62 d of supplementation, cows fed sunflower supplements tended (P = 0.08) to lose more body condition than cows fed the control diet, but BCS was not different (P > 0.22) for any subsequent measurement. At the beginning of the breeding season, the percentage of cows exhibiting luteal activity was greater for cows fed the control diet (43%; P = 0.02) than for cows fed either linoleic (20%) or oleic (16%) supplementation; however, first-service conception rate (67%; P = 0.22) and pregnancy rate at weaning (92%; P = 0.18) were not different among supplements. No differences were detected in calf birth (P = 0.46) or weaning BW (P = 0.74). In Exp. 2, 8 ruminally cannulated steers were used to determine the effects of sunflower seed supplementation on forage intake and digestion. Treatments (DM basis) included 1) no supplement; 2) a soybean hull-based supplement fed at 0.29% of BW/d; 3) whole linoleic sunflower seed fed at 0.16% of BW/d; and 4) whole high-oleic sunflower seed fed at 0.16% of BW/d. Hay intake was not influenced (P = 0.25) by supplement (1.51% of BW/d); however, DMI was greatest (P < 0.01) for steers fed the soybean hull-based supplement (1.93% of BW/d). Sunflower seed supplementation reduced (P < 0.01) NDF and ADF digestibility while increasing (P < 0.01) apparent CP and apparent lipid digestibility. In conclusion, whole sunflower seed supplementation resulted in reduced cow BW gain during mid to late gestation, but this reduction did not influence subsequent cow BW change, pregnancy rate, or calf performance.     

Whole soybean supplementation and cow age class: effects on intake, digestion, performance, and reproduction of beef cows

Two experiments were conducted to determine the effects of whole soybean supplementation on intake, digestion, and performance of beef cows of varying age. Treatments were arranged in a 2 x 3 factorial with 2 supplements and 3 age classes of cows (2-yr-old, 3-yr-old, and mature cows). Supplements (DM basis) included 1) 1.36 kg/d of whole raw soybeans, and 2) 1.56 kg/d of a soybean meal/hulls supplement. Supplements were formulated to provide similar amounts of protein and energy, but a greater fat content with the whole soybeans. Supplements were individually fed on Monday, Tuesday, Thursday, and Saturday mornings. During the treatment period, cows had free choice access to bermudagrass hay [Cynodon dactylon (L.) Pers.; 8.4% CP; 72% NDF; DM basis]. In Exp. 1, 166 spring-calving Angus and Angus x Hereford crossbred beef cows were individually fed supplements for an average of 80 d during mid to late gestation. During the first 50 d of supplementation, cows fed soybean meal/hulls gained more BW (10 kg; P < 0.001) and body condition (0.18 BCS units; P = 0.004) than cows fed whole soybeans. However, BW change (P = 0.87) and BCS change (P = 0.25) during the 296-d experiment were not different between supplements. Although calves from cows fed soybean meal/hulls were 2 kg heavier at birth, there was no difference in calf BW at weaning between supplements. Additionally, first service conception rate (68%; P = 0.24) and pregnancy rate (73%; P = 0.21) were not different between supplements. In Exp. 2, 24 cows from Exp. 1 were used to determine the effect of supplement composition on forage intake and digestion; cows remained on the same supplements, hay, and feeding schedule as Exp. 1. Crude fat digestibility was the only intake or digestibility measurement influenced by supplement composition; fat digestibility was higher for cows fed whole soybeans compared with cows fed the soybean meal/hulls supplement (58.1 vs. 48.8%). Hay intake and DMI averaged 1.63 and 1.92% of BW daily, respectively. Dry matter, NDF, and CP digestibility averaged 54.1, 55.1, and 63.2%, respectively. Compared with supplementation with soybean meal/ hulls, whole soybean supplementation during mid to late gestation resulted in reduced BW weight gain during supplementation, inconsistent effects on reproduction, no effect on calf weaning weight, and no effect on forage intake or digestion.     

The influence of high-nitrogen forages on the voluntary feed intake of sheep

The objective of this research was to examine the effect of high concentrations of nonprotein nitrogen (NPN) on the voluntary food intake of sheep fed high-quality grasses. Wether lambs (n = 6 per treatment) were fed dried switchgrass (Panicum virgatum L.; Exp. 1) or dried tall fescue (Festuca arundinacea Schreb.; Exp. 2). In both experiments, urea was added to the dried forage at 0 (control), 12, or 24 g of N/kg of DM to increase the NPN concentration. Acid detergent fiber concentrations were 305 g/kg of DM in both experiments, although DM digestibility was 663 and 618 g/ kg of DM in Exp. 1 and Exp. 2, respectively. Voluntary feed intake of the control forage was 28.2 and 19.1 g/ kg of BW in Exp. 1 and Exp. 2, respectively, and decreased for the high-urea treatments to 25.2 and 16.2 g/kg of BW in Exp. 1 (P = 0.07) and Exp 2 (P = 0.03), respectively. Total feed N concentrations increased from 29.5 g to 45.7 g of N/kg of DM in Exp. 1 (P < 0.01) and from 28.4 to 55.9 g of N/kg of DM in Exp. 2 (P < 0.01). Nonprotein N concentrations increased from 28.3 to 53.8% of the total N in switchgrass diets (Exp. 1; P < 0.01), and from 26.4 to 64.0% in tall fescue diets (Exp. 2; P < 0.01). Plasma urea concentrations of the lambs increased from 3.1 to 6.6 mM (Exp. 1; P < 0.01) and from 2.9 to 5.8 mM (Exp. 2; P < 0.01) as the amount of urea added to the diets increased. These changes resulted in an increase in plasma osmolality from 298 to 307 mOsm/kg (Exp. 1; P = 0.04), and from 299 to 307 mOsm/kg (Exp. 2; P = 0.06). Increasing feed N and NPN concentrations through the addition of urea caused a significant decrease in the voluntary feed intake of sheep fed tall fescue and switchgrass. These responses showed no significant cause-and-effect relationship between voluntary feed intake, plasma urea concentrations, and plasma osmolality.     

Supplementation of dried distillers grains with solubles to beef cows consuming low-quality forage during late gestation and early lactation

Three experiments were conducted to evaluate supplementation of dried distillers grains with solubles (DGS) to spring-calving beef cows (n = 120; 541 kg of initial BW; 5.1 initial BCS) consuming low-quality forage during late gestation and early lactation. Supplemental treatments included (DM basis) 1) 0.77 kg/d DGS (DGSL); 2) 1.54 kg/d DGS (DGSI); 3) 2.31 kg/d DGS (DGSH); 4) 1.54 kg/d of a blend of 49% wheat middlings and 51% cottonseed meal (POS); and 5) 0.23 kg/d of a cottonseed hull-based pellet (NEG). Feeding rate and CP intake were similar for DGSI and POS. In Exp. 1, cows were individually fed 3 d/wk until calving and 4 d/wk during lactation; total supplementation period was 119 d, encompassing 106 d of gestation and 13 d of lactation. Tall-grass prairie hay (5.6% CP, 50% TDN, 73% NDF; DM basis) was fed for ad libitum intake throughout the supplementation period. Change in cow BW and BCS during gestation was similar for DGSI and POS (-5.0 kg, P = 0.61 and -0.13, P = 0.25, respectively) and linearly increased with increasing DGS level (P < 0.01). Likewise, during the 119-d supplementation period, BW and BCS change were similar for DGSI and POS (-72 kg, P = 0.22 and -0.60, P = 0.10) and increased linearly with respect to increasing DGS (P < 0.01). The percentage of cows exhibiting luteal activity at the beginning of breeding season (56%, P = 0.31), AI conception rate (57%, P = 0.62), or pregnancy rate at weaning (88%, P = 0.74) were not influenced by supplementation. In Exp. 2, 30 cows from a separate herd were used to evaluate the effect of DGS on hay intake and digestion. Supplementation improved all digestibility measures compared with NEG. Hay intake was not influenced by DGS (P > 0.10); digestibility of NDF, ADF, CP, and fat linearly increased with increasing DGS. In Exp. 3, milk production and composition were determined for cows (n = 16/treatment) of similar days postpartum from Exp. 1. Daily milk production was not influenced by supplementation (6.3 kg/d, P = 0.25). Milk fat (2.1%) and lactose (5.0%) were not different (P > 0.10). Milk protein linearly increased as DGS increased (P < 0.05) and was greater for DGSI compared with POS. Similar cow performance was achieved when cows were fed DGS at the same rate and level of CP as a traditional cottonseed meal-based supplement. Increasing amounts of DGS did not negatively influence forage intake or diet digestibility.     

Nonstructural carbohydrate supplementation of yearling heifers and range beef cows

A digestion study with 28 yearling heifers (428 +/- 9.9 kg; Exp. 1) and a 2-yr winter grazing trial with 60 crossbred cows (552 +/- 6.9 kg; Exp. 2) were used to determine the effects of level of nonstructural carbohydrate (NSC) supplementation on intake and digestibility of low-quality forage. Treatments were as follows: 1) control, no supplement; 2) 0.32 kg of NSC (1.8 kg/d of soybean hulls and soybean meal; DM basis); 3) 0.64 kg of NSC (1.7 kg/d of wheat middlings; DM basis); and 4) 0.96 kg of NSC (1.7 kg/d of barley and soybean meal; DM basis). Supplements provided 0.34 kg of CP/d and 5.1 Mcal of ME/d. In Exp. 1, heifers were individually fed hay (5.5% CP, DM basis) and their respective supplements in Calan gates for 28 d. Data were analyzed as a completely randomized design. In Exp. 2, cows were individually fed supplement on alternate days, and grazed a single rangeland pasture stocked at 1.8 ha/ animal unit month. Two ruminally cannulated cows were used per treatment to obtain forage extrusa and to measure in situ DM disappearance (DMD) and carboxymethylcellulase (CMCase) activity of particle-associated ruminal microbes. Data were analyzed as a completely randomized design with the effects of treatment, year, and their interaction. In both experiments, Cr2O3 boluses were used to determine fecal output, individual animal was the experimental unit, and contrasts were used to test linear and quadratic effects of NSC level and control vs. supplemented treatments. In Exp. 1, hay and diet DM, NDF, and CP intakes and digestibilities were increased (P < 0.01) by NSC supplementation compared with the control. In Exp. 2, 72-h in situ DMD and CMCase were decreased linearly (P < 0.08) with increasing NSC supplementation. Intake of forage DM, NDF, and CP was decreased linearly (P < 0.01) with increasing NSC supplementation during both years. Supplementation with NSC decreased (P = 0.01) cow BW loss compared with the control in yr 1, whereas in yr 2, cow BW loss was linearly increased (P = 0.03) by increasing NSC supplementation. Supplements containing NSC improved forage digestion and intake when heifers consumed forage deficient in CP relative to energy (digestible OM:CP > 7), but decreased forage digestion and intake when cows grazed forage with adequate CP relative to energy (digestible OM:CP < 7). Forage and supplement digestible OM:CP seemed to be superior predictors of response to supplementation with NSC compared with forage CP levels alone.     

Effect of supplementation frequency and supplemental urea level on dormant tallgrass-prairie hay intake and digestion by beef steers and prepartum performance of beef cows grazing dormant tallgrass-prairie

Effect of supplementation frequency and supplemental urea level on forage use (Exp. 1) and performance (Exp. 2 and 3) of beef cattle consuming low-quality tallgrass-prairie were evaluated. For Exp. 1 and 2, a 2 x 2 factorial treatment structure was used, such that two supplements (30% CP) containing 0 or 30% of supplemental degradable intake protein (DIP) from urea were fed daily or on alternate days. In Exp. 1 and 2, supplement was fed at 0.41% BW daily or at 0.83% BW (DM basis) on alternate days. For Exp. 3, a 2 x 4 factorial treatment structure was used, such that four supplements (40% CP) containing 0, 15, 30, or 45% of supplemental DIP from urea were fed daily or 3 d/wk. Supplements were group-fed at 0.32% BW daily or at 0.73% BW (DM basis) 3 d/wk. In Exp. 1, 16 Angus x Hereford steers (initial BW = 252 kg) were blocked by BW and assigned to treatment. Urea level x supplementation frequency interactions were not evident for forage intake, digestion, or rate of passage. Forage OM intake (OMI) and total digestible OMI (TDOMI) were not significantly affected by treatment. Total-tract digestion of OM (P = 0.03) and NDF (P = 0.06) were greater for steers supplemented daily. In Exp. 2, 48 Angus x Hereford cows (initial BW = 490 kg) grazing winter tallgrass prairie were used. Significant frequency x urea interactions were not evident for BW and body condition (BC) change; similarly, the main effects were not substantive for these variables. In Exp. 3, 160 Angus x Hereford cows (initial BW = 525 kg) grazing dormant, tallgrass prairie were used. Supplement refusal occurred for cows fed the highest urea levels, particularly for cows fed the supplement with 45% of the DIP from urea 3 d/wk, and supplement refusal increased closer to calving. A frequency x urea interaction (P = 0.02) was observed for prepartum BW changes. As supplemental urea level increased, prepartum BW loss increased quadratically (P = 0.02); however, a greater magnitude of loss occurred when feeding supplements containing > or = 30% of DIP from urea 3 d/ wk. Cumulative BC change followed a similar trend. In conclusion, moderate protein (< or = 30% CP) supplements with < or = 30% of supplemental DIP from urea can be fed on alternate days without a substantive performance penalty. However, infrequent feeding of higher protein (> 30% CP) supplements with significant urea levels (> 15% of DIP from urea) may result in decreased performance compared with lower urea levels.     

Thiamin supplementation and the ingestive behavior of beef cattle grazing endophyte-infected tall fescue

Livestock grazing endophyte (Acremonium coenophialum Morgan-Jones and Gams)-infected tall fescue (Festuca arundinacea Schreb.) perform poorly due to tall fescue toxicosis, especially when animals are under heat stress. In order to determine whether thiamin promotes recovery from tall fescue toxicosis, 1 or 0 g of thiamin per day, as mononitrate, was fed orally to adult Angus (Bos taurus) cows (380 +/- 8 kg) grazing either tall fescue pasture with and without endophyte or alfalfa (Medicago sativa L.). A tethered grazing system employing a split-plot design was used to estimate intake and components of ingestive behavior. No significant differences attributable to thiamin supplements were seen in rates of intake and biting, grazing time and intake per bite when cows grazed endophyte-infected tall fescue during the first 4 d of exposure. When cows grazed endophyte-infected (greater than 95%) tall fescue with 2,091 micrograms/g loline alkaloids after 4 d of exposure, the untreated animals ingested herbage dry matter (DM) at 1.19 kg/h, whereas the cows receiving thiamin ate 1.57 kg/h (P less than .05). Cattle achieved these rates of DM intake by forming bites of 1.0 and 1.2 g DM at 24 and 26 bites/min when treated with 0 and 1 g of thiamin per day, respectively. Thiamin supplements had no effect on ingestive behavior of cows grazing endophyte-free tall fescue or alfalfa after exposure to these forages for 4 d. Responses to thiamin generally were greater when cattle grazing endophyte-infected tall fescue were exposed to heat stress. Oral thiamin supplementation may alleviate tall fescue toxicosis of beef cattle during warm weather.     

Efficacy of using a combination of rendered protein products as an undegradable intake protein supplement for lactating, winter-calving, beef cows fed bromegrass hay

Seventy-two (36 in each of two consecutive years) lactating, British-crossbred cows (609 +/- 19 kg) were used to evaluate effects of feeding a feather meal-blood meal combination on performance by beef cows fed grass hay. Bromegrass hay (9.6% CP, DM basis) was offered ad libitum and intake was measured daily in individual Calan electronic headgates. Acclimation to Calan gates began approximately 20 d after parturition, and treatments were initiated 21 d later. Cows were assigned randomly to one of four treatments (DM basis) for 60 d: 1) nonsupplemented control (CON), 2) energy control (ENG; 790 g/d; 100% beet pulp), 3) degradable intake protein (DIP; 870 g/d; 22% beet pulp and 78% sunflower meal), or 4) undegradable intake protein (UIP; 800 g/d; 62.5% sunflower meal, 30% hydrolyzed feather meal, and 7.5% blood meal). Net energy concentrations of supplements were formulated to provide similar NE(m) intakes (1.36 Mcal/d). The DIP and UIP supplements were calculated to supply similar amounts of DIP (168 g/d) and to supply 64 and 224 g/d of UIP, respectively. Forage DMI (kg/d) decreased in supplemented vs. nonsupplemented (P = 0.03) and DIP vs. UIP (P = 0.001); however, when expressed as a percentage of BW, forage DMI was not different (P = 0.23). Supplemented cows tended (P = 0.17) to lose less BW than CON. Body condition change was not affected (P = 0.60) by postpartum supplementation. No differences were noted in milk production (P = 0.29) or in calf gain during the supplementation period (P = 0.74). Circulating insulin concentrations were not affected by treatment (P = 0.42). In addition, supplementation did not affect circulating concentrations of NEFA (P = 0.18) or plasma urea nitrogen (P = 0.38). Results of the current study indicate that supplementation had little effect on BW, BCS, milk production, or calf BW when a moderate-quality forage (9.6% CP) was fed to postpartum, winter-calving cows in optimal body condition (BCS > 5). Supplemental UIP did not enhance cow performance during lactation. Forage UIP and microbial protein supply were adequate to meet the metabolizable protein requirements of lactating beef cows under the conditions of this study.     

Effects of supplemental Bermuda grass hay or corn on intake, digestion and performance of cattle consuming endophyte-infected fescue

Effects of supplemental Bermuda grass hay (BG) or ground corn on intake, digestion and performance of cattle consuming endophyte-infected fescue (I) were studied. In Exp. 1, a Latin square study, five growing Holstein steers (158.1 kg) consumed I ad libitum and were offered 0, .3, .6, .9 or 1.2% body weight (BW) of BG daily. Total dry matter (DM) intake rose linearly (P less than .05) with increasing BG, although intake was numerically similar with .6, .9 and 1.2% BW of BG. Digestibility was constant with diet (P greater than .10). Six growing Holstein steers used in Exp. 2, a Latin square with a 2 x 3 factorial arrangement of treatments, ingested I or noninfected (NI) fescue hay ad libitum with 0, .5 or 1.0% BW of ground corn. Total DM intake increased linearly as the level of corn rose (P less than .05). Total intake with I increased more with the first than with the second addition of corn, and the opposite occurred with NI (interaction between fescue infection and the quadratic effect of corn level, P less than .10). Organic matter digested (g/d) was greater for NI than for I and rose linearly with increasing corn ingestion (P less than .05). Ninety-six crossbred beef heifers and steers (184.2 kg avg initial live weight) were used in a 77-d fall grazing experiment (Exp. 3) with a 2 x 3 factorial treatment arrangement. Cattle grazed I or NI paddocks and were given no supplement or .34% BW of BG or .65% BW of ground corn on a daily basis (DM).(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of residual feed intake classification on forage intake by grazing beef cows

Although feed intake and efficiency differences in growing cattle of low and high residual feed intake (RFI) classification have been established, little is known about the difference in grazed forage intake between beef cows of known RFI classification. Two experiments were conducted using Hereford cows for which RFI had been determined as heifers using the GrowSafe 4000E feed intake system, after which heifers had been divided into thirds as low RFI, mid RFI, and high RFI. During Exp. 1, 2 replicates of low and high RFI cows (n = 7/replicate) in mid- to late-gestation were blocked to 1 of 4 non-endophyte-infected tall fescue paddocks (1.8 to 2.4 ha), which they grazed continuously for 84 d during summer. Using grazing exclosures, weekly rising plate meter readings, and forage harvests every 21 d, average forage DMI was calculated. Low and high RFI groups did not differ (P > 0.05) in BW change or BCS change over the trial (19.5 vs. 22.1 kg of BW gain and 0.11 vs. 0.10 BCS gain), but low RFI cows had a 21% numerically lower DMI than high RFI cows (12.4 vs. 15.6 kg/d; P = 0.23). The average area needed per paddock over the trial was similar for low and high RFI cows (1.71 vs. 1.82 ha; P = 0.35), and the average DM on offer over the trial was less for low RFI than for high RFI cows (4,215 vs. 4,376 kg; P = 0.06). During Exp. 2, 3 replicates of low and high RFI cows with their calves (n = 4 pair/replicate) strip-grazed stockpiled and early spring growth tall fescue paddocks (0.7 to 0.9 ha) for 60 d in late winter and early spring. Because of limiting forage availability and quality at trial initiation, cow-calf pairs were also fed 3.31 kg/pair of pelleted soyhulls daily. Pre- and post-grazed forage samples were harvested for 4 grazing periods, and forage growth was estimated using a growing degree days calculation and on-site weather station data. Performance did not differ (P > 0.05) between low and high RFI cows throughout the experiment (18.4 vs. 26.6 kg of BW gain and -0.04 vs. 0.15 BCS gain). Despite the utilization of forage offered being similar for low and high RFI cow-calf pairs (P > 0.05), low RFI cows and their calves had an 11% numerically lower DMI than high RFI pairs (12.5 vs. 14.1 kg/d; P = 0.12). We concluded that either no intake differences existed between low and high RFI cows or that current methodology and small animal numbers limited our ability to detect differences.     

Impacts of increasing amounts of supplemental soybean meal on intake and digestion by beef steers and performance by beef cows consuming low-quality tallgrass-prairie forage

Two experiments were conducted to evaluate the impacts of increasing levels of supplemental soybean meal (SBM) on intake, digestion, and performance of beef cattle consuming low-quality prairie forage. In Exp. 1, ruminally fistulated beef steers (n = 20; 369 kg) were assigned to one of five treatments: control (forage only) and .08, .16, .33, and .50% BW/d of supplemental SBM (DM basis). Prairie hay (5.3% CP; 49% DIP) was offered for ad libitum consumption. Forage OM intake (FOMI) and total OM intake (TOMI) were increased (cubic, P = .01) by level of supplemental SBM, but FOMI reached a plateau when the daily level of SBM supplementation reached .16% BW. The concomitant rises in TOMI and OM digestibility (quadratic, P = .02) resulted in an increase (cubic, P = .03) in total digestible OM intake (TDOMI). In Exp. 2, spring-calving Hereford x Angus cows (n = 120; BW = 518 kg; body condition [BC] = 5.3) grazing low-quality, tall-grass-prairie forage were assigned to one of three pastures and one of eight treatments. The supplemental SBM (DM basis) was fed at .08, .12, .16, .20, .24, .32, .40, and .48% BW/d from December 2, 1996, until February 10, 1997 (beginning of the calving season). Performance seemed to reach a plateau when cows received SBM at approximately .30% BW/d. Below this level, cows lost approximately .5 unit of BC for every .1% BW decrease in the amount of supplemental SBM fed. Providing supplemental SBM is an effective means of improving forage intake, digestion, and performance of beef cattle consuming low-quality forages.     

Effects of stocking rate and corn gluten feed supplementation on performance of young beef cows grazing winter-stockpiled tall fescue-red clover pasture

A winter grazing experiment was conducted to evaluate the effects of stocking rate and corn gluten feed supplementation on forage mass and composition and the BW and BCS of bred 2-yr-old cows grazing stockpiled forage during winter. Two 12.2-ha blocks containing Fawn, endophyte-free, tall fescue and red clover were each divided into 4 pastures of 2.53 or 3.54 ha. Hay was harvested from the pastures in June and August of 2003 and 2004, and N was applied at 50.5 kg/ha at the initiation of stockpiling in August. On October 22, 2003, and October 20, 2004, twenty-four 30-mo-old Angus-Simmental and Angus cows were allotted by BW and BCS to strip-graze for 147 d at 0.84 or 1.19 cow/ha. Eight similar cows were allotted to 2 dry lots and fed tall fescue-red clover hay ad libitum. Corn gluten feed was fed to cows in 2 pastures to maintain a mean BCS of 5 (9-point scale) at each stocking rate and in the dry lots (high supplementation level) or when weather prevented grazing (low supplementation level) in the remaining 2 pastures at each stocking rate. Mean concentrations of CP in yr 1 and 2 and IVDMD in yr 2 were greater (P < 0.10) in hay than stockpiled forage over the winter. At the end of grazing, cows fed hay in dry lots had greater (P < 0.05) BCS in yr 1 and greater (P < 0.10) BW in yr 2 than grazing cows. Grazing cows in the high supplementation treatment had greater (P < 0.10) BW than cows grazing at the low supplementation level in yr 1. Cows in the dry lots were fed 2,565 and 2,158 kg of hay DM/cow. Amounts of corn gluten feed supplemented to cows in yr 1 and 2 were 46 and 60 kg/ cow and did not differ (P = 0.33, yr 1; P = 0.50, yr 2) between cows fed hay or grazing stockpiled forage in either year. Estimated production costs were greater for cows in the dry lots because of hay feeding.     

Effects of offering different amounts and types of supplemental feeds to growing dairy steers fed endophyte-infected fescue hay ad libitum on intake, digestion, passage rate and serum prolactin concentration

Ten Holstein steers (141 kg) were used in two 5 X 5 Latin-square experiments conducted simultaneously to determine the effects of offering different levels and types of feeds with endophyte-infected fescue given ad libitum. In Exp. 1, steers were given ad libitum access to infected fescue hay in the afternoon; in the morning fescue was given ad libitum (basal) or bermudagrass or clover hays were fed at .5 or 1.0% of body weight (BW). Supplementation did not affect total dry matter intake (P greater than .10), but supplementation at 1.0% of BW yielded total intake greater than supplementation at .5% of BW (P less than .05). Supplementation did not change digestibilities of dry or organic matter (P greater than .10). Particulate passage rate was greater (P less than .10) with supplementation at 1.0 than at .5% of BW, and increasing the level of supplementation from .5 to 1.0% of BW affected fluid passage rate positively with clover but negatively with bermudagrass (interaction, P less than .05). Serum prolactin increased (P less than .05) with all supplementation treatments, although no differences were observed between supplement type-supplementation level combinations (P greater than .10). Ground corn and wheat hay were supplements in Exp. 2. Total intake of dry matter was greater with supplements provided at 1.0 rather than at .5% of BW and for corn rather than wheat hay (P less than .05). Neutral detergent fiber digestion (percent of intake and grams per day) rose when wheat hay was offered at 1.0 vs .5% of BW but declined when the level of supplemental corn increased from .5 to 1.0% of BW (interaction, P less than .05). There were no differences among diets in particulate and fluid passage rates and serum prolactin concentration. Supplementation with nontoxic forage of a basal diet of infected fescue yielded intake substitution when forage was offered at .5% of BW, although incomplete substitution occurred with 1.0% of BW of supplemental forage such that total intake increased as compared to the lower level of supplementation.     

Performance, forage utilization, and ergovaline consumption by beef cows grazing endophyte fungus-infected tall fescue, endophyte fungus-free tall fescue, or orchardgrass pastures.

Two 120-d trials (May to September, 1988 and 1989) determined the effects of grazing tall fescue (two varieties) or orchardgrass on forage intake and performance by beef cows. Each summer, 48 cow-calf pairs grazed endophyte-infected Kentucky-31 tall fescue (KY-31), endophyte-free Mozark tall fescue (MOZARK), or Hallmark orchardgrass (OG) pastures (16 pairs/treatment). Forage OM intakes and digestibilities were determined during June and August each year. Cow and calf BW and milk production were determined every 28 d. During June of both years, OM intakes did not differ (P greater than .10) among treatments. During August of 1988, intakes were 18% lower (P less than .05) by KY-31 cows (1.6% of BW) than by MOZARK or OG cows (average 1.95% of BW); however, no differences (P greater than .10) were measured in August of 1989. Estimates of ergovaline consumption during June from KY-31 were between 4.2 (1988) and 6.0 mg/d (1989), whereas August estimates were between 1.1 (1988) and 2.8 mg/d (1989). Ergovaline in MOZARK estrusa was below detection limits, except in August of 1989. Cows that grazed KY-31 lost three times (P less than .01) more BW than cows that grazed MOZARK or OG (42 vs 9 and 13 kg, respectively). Milk production by KY-31 cows was 25% lower (P less than .01) than that by cows that grazed MOZARK or OG (6.0 vs average of 8.0 kg/d). Similarly, slower (P less than .01) calf gains were noted for KY-31 than for MOZARK or OG (.72 vs .89 and .88 kg/d, respectively). Cows grazing KY-31 experienced accelerated BW loss and reduced milk production and weaned lighter calves than did cows grazing MOZARK or OG. Decreased performance was not explained by consistently reduced forage intakes; hence, altered nutrient utilization was suspected.     

Influence of protein supplementation frequency on cows consuming low-quality forage: performance, grazing behavior, and variation in supplement intake

The objectives of this research were to determine the influence of protein supplementation frequency on cow performance, grazing time, distance traveled, maximum distance from water, cow distribution, DMI, DM digestibility, harvest efficiency, percentage of supplementation events frequented, and CV for supplement intake for cows grazing low-quality forage. One hundred twenty pregnant (60 +/- 45 d) Angus x Hereford cows (467 +/- 4 kg BW) were used in a 3 x 3 Latin square design for one 84-d period in each of three consecutive years. Cows were stratified by age, BCS, and BW and assigned randomly to one of three 810-ha pastures. Treatments included an unsupplemented control (CON) and supplementation every day (D; 0.91 kg, DM basis) or once every 6 d (6D; 5.46 kg, DM basis) with cottonseed meal (CSM; 43% CP, DM basis). Four cows from each treatment (each year) were fitted with global positioning system collars to estimate grazing time, distance traveled, maximum distance from water, cow distribution, and percentage of supplementation events frequented. Collared cows were dosed with intraruminal n-alkane controlled-release devices on d 28 for estimation of DMI, DM digestibility, and harvest efficiency. Additionally, Cr2O3 was incorporated into CSM on d 36 at 3% of DM for use as a digesta flow marker to estimate the CV for supplement intake. Cow BW and BCS change were greater (P < or = 0.03) for supplemented treatments compared with CON. No BW or BCS differences (P > or = 0.14) were noted between D and 6D. Grazing time was greater (P = 0.04) for CON compared with supplemented treatments, with no difference (P = 0.26) due to supplementation frequency. Distance traveled, maximum distance from water, cow distribution, DMI, DM digestibility, and harvest efficiency were not affected (P > or = 0.16) by protein supplementation or supplementation frequency. The percentage of supplementation events frequented and the CV for supplement intake were not affected (P > or = 0.58) by supplementation frequency. Results suggest that providing protein daily or once every 6 d to cows grazing low-quality forage increases BW and BCS gain, while decreasing grazing time. Additionally, protein supplementation and supplementation frequency may have little to no effect on cow distribution, DMI, and harvest efficiency in the northern Great Basin.     

Intake, digestion, and digestive characteristics of Neotyphodium coenophialum-infected and uninfected fescue by heifers offered hay diets supplemented with Aspergillus oryzae fermentation extract or laidlomycin propionate

Tarentaise heifers fitted with a rumen cannula (539 +/- 7.5 and 487 +/- 15.7 kg avg initial BW in Exp. 1 and 2, respectively) were used in two Latin square metabolism experiments having 2 x 2 factorial treatment arrangements to determine the effects of supplementation with Aspergillus oryzae fermentation extract (AO) or laidlomycin propionate (LP) on intake, digestion, and digestive characteristics of Neotyphodium coenophialum-infected (IF) or uninfected (FF) tall fescue (Festuca arundinacea) hay diets consumed ad libitum. Heifers were housed in individual stanchions in a metabolism facility with ambient temperatures controlled to range between 26.7 and 32.2 degrees C daily. Total feces and urine were collected for 5 d following a 21-d dietary adaptation period. In situ DM and NDF disappearance and ruminal fermentation characteristics were also determined. In Exp. 1, DMI was 24% greater (P < 0.01) by heifers offered FF than by those offered IF (6.7 vs 5.4 kg/d). Heifers fed 2 g/d AO tended (P = 0.09) to consume 4% more DM than those fed a diet without AO. Degradable DM and NDF fractions of IF were greater (P < 0.01) than those of FF, but AO supplementation did not affect situ disappearance (P > or = 0.42). In Exp. 2, DMI was 18.9% greater (P < 0.01) by heifers offered FF than by those offered IF (6.6 vs 5.5 kg/d). Heifers fed LP (50 mg/d) consumed 10.6% less (P < 0.05) DM than those not fed LP (5.7 vs 6/5 kg/d). Digestibility of NDF tended to be greater (P = 0.08) and digestibility of ADF was greater (P < 0.05) from FF than from IF. Conversely, apparent N absorption (%) was greater (P < 0.05) from IF than from FF. Heifers fed LP had lower (P < 0.05) ADF digestibility than those not fed LP. In situ degradable DM and NDF fractions were greater (P < 0.01) from IF than from FF. Diets supplemented with LP had higher (P < 0.01) indigestible DM and NDF fractions than those without LP. Propionic acid and total VFA concentrations were greater (P < 0.05) from heifers offered FF than from those offered IF and from heifers fed LP than from those not fed LP. Therefore, it appears the major effect of N. coenophialum was a reduction in forage intake and total-tract fiber digestibility in certain situations. Response to the feed additives was similar whether heifers were offered IF or FF and no evidence was apparent that either additive would improve performance substantially by animals consuming low-quality fescue hay diets.     

Voluntary consumption and digestion of diets high in endophyte-infected fescue by growing Holstein steers

Holstein steers (112 to 258 kg BW) were fed diets high in endophyte-infected fescue (80 to 100%) in 15 latin square experiments to determine the relationships among BW, forage composition, voluntary consumption and digestion. Fescue DM intake (kg/d) increased linearly (P less than .05) with increasing BW (-.513 + .0275 BW; R2 = .69). Regressing log fescue intake (DM) on log BW resulted in a BW exponent of 1.1034 (R2 = .66) but did not account for any more variation in intake than the simple regression did. The percentage NDF in fescue was not related (P greater than .10) to fescue intake (kg/d) and was correlated only slightly with fescue intake as a percentage of BW (r = -.13; P less than .10). Adding the percentage of fescue in the diet or NDF in the fescue to the regression of DM intake on BW did not increase explained variation. Organic matter intake (kg) and digestibility (%) were not related (P greater than .10). Based on standardized partial regression coefficients, differences in voluntary intake accounted for 60% of the variation in the total quantity of OM digested, whereas differences in digestibility accounted for 40%. In conclusion, ingestibility of endophyte-infected fescue hay in relation to changing BW did not vary greatly. Concentrations of chemical constituents such as NDF and ADL in fescue were poorly correlated with feed consumption and digestibility.