Effects of treating corn silage with alpha-amylase and(or) sorbic acid on beef cattle growth and carcass characteristics

The effects on beef cattle growth performance and carcass characteristics of feeding silages produced by altered fermentations were determined. Alpha-amylase was added at 0 or .05% (wet basis) and sorbic acid was added at 0 or .10% (wet basis) to chopped whole corn plants before ensiling in a 2 x 2 factorial arrangement of treatments. For three successive years, 40 beef heifers (224 kg) were fed these silages for 80 d, finished on corn-and-cob meal (107 d) and slaughtered when backfat thickness over the 13th rib reached 12 mm. Silages treated with alpha-amylase had a slightly higher percentage of N-free extract (P less than .10). Silages treated with sorbic acid had lower percentages of ADFN (P less than .10). During the silage-feeding phase, heifers fed silages treated with alpha-amylase gained more (P less than .01) daily than heifers fed the other two silages (.84 vs .78 kg) and they were more efficient (P less than .01) in weight gain per unit of dry feed consumed (.149 vs .139 kg). During the finishing phase, heifers that previously had been fed the alpha-amylase-treated silage continued to have higher (P less than .05) ADG (.93 vs .87 kg), although all were fed the same diet during this period. Added sorbic acid had no effect on ADG in either period. The percentage of kidney fat in heifers on the alpha-amylase treatments was increased (P less than .02, 2.2 vs 2.0). The biological mechanisms associated with the beneficial results of alpha-amylase addition are not understood yet.     

Effects of ractopamine and protein source on growth performance and carcass characteristics of feedlot heifers

An experiment was conducted to determine the relationship between feeding ractopamine and different amounts of MP on growth and carcass characteristics of feedlot heifers. Seventy-two crossbred heifers (475 kg of initial BW) were fed individually a diet based on steam-flaked corn for ad libitum intake for 29 d. Heifers were implanted with 140 mg of trenbolone acetate and 14 mg of estradiol-17beta 60 d before the experiment. Treatments were arranged as a 2 x 3 factorial and included 0 or 200 mg of ractopamine-HCl (23 ppm)/ d, and urea, solvent soybean meal, or expeller soybean meal (ESBM) as the predominant protein supplement. The amounts of MP supplied by the urea, solvent soybean meal, and ESBM diets were 688, 761, and 808 g/ d, respectively, calculated according to level 1 of the NRC model. Body weights were obtained 1 d before ractopamine feeding and at slaughter. Blood samples were obtained 1 d before starting the experiment and 13 d later. Ractopamine improved ADG, efficiency of gain, carcass-adjusted ADG, and carcass-adjusted efficiency of gain (P < 0.01). For ADG, heifers demonstrated a ractopamine x protein source interaction (P < 0.05); heifers not fed ractopamine had greater ADG when fed ESBM than when fed urea, whereas for heifers fed ractopamine there were no differences (P > or = 0.10) among protein supplements. This interaction was not observed for carcass-adjusted ADG (P = 0.60). Final live weights (P = 0.02) and carcass weights (P = 0.01) were greater with ractopamine feeding. Carcass marbling scores and yield grades were not affected by ractopamine or protein source (P > or = 0.39). Plasma total alpha-amino N and glucose concentrations decreased more from pretreatment concentrations when heifers were fed ractopamine (P < 0.05). Feeding ractopamine to heifers for 28 d before slaughter improved ADG and efficiency of gain without any large effects on carcass characteristics. The MP supply does not need to be increased from that provided by finishing diets based on steam-flaked corn with urea as the primary N supplement to allow the maximal response to ractopamine by finishing heifers.     

Feedlot performance and pregnancy inhibition of heifers treated with depot-formulated melengestrol acetate

In dose titration trials beef heifers received depot-formulated melengestrol acetate (DEPO-MGA) in single s.c. ear injections to determine effects on performance and pregnancy inhibition. In a 112-d feedlot trial, 105 heifers were assigned to light, medium and heavy weight blocks on five treatments: dietary MGA (.5 mg.hd-1.d-1), control (no MGA) or DEPO-MGA on d 1 at .5, 1.0 or 1.5 ml/hd (30, 60 or 90 mg MGA/hd, respectively). A high-energy cracked corn diet was fed to all heifers ad libitum. At d 56 and d 112, ADG and feed/gain were not affected (P greater than .05) by dietary MGA or DEPO-MGA treatments, although dietary MGA tended to increase 112-d ADG (1.67 vs 1.58 kg) compared with controls. In a pasture trial, 100 beef heifers were assigned by weight to five treatments: control (no MGA) or DEPO-MGA injected on d 1 at .5, 1.0, 1.5 or 2.0 ml/hd (30, 60, 90 or 120 mg MGA/hd, respectively). Heifers were pastured as a single herd and were exposed to fertile bulls from d 7 to d 181. Weights and pregnancy data were recorded at d 62, 90, 134, 181 and 225. Heifer ADG was not affected (P greater than .05) by DEPO-MGA treatment at any weighing date. By d 90, 90% of control heifers were pregnant, and 100% were pregnant by d 134. Pregnancy inhibition rates of 90% to 100% for each DEPO-MGA treatment at d 62, 90 and 134 were higher (P less than .01) than those in control heifers. Pregnancy was inhibited in 90% of heifers on 60-mg and 90-mg DEPO-MGA treatments through d 181, and in 95% of heifers on the 120 mg DEPO-MGA treatment through d 225.     

Forage mineral concentration, animal performance, and mineral status of heifers grazing cereal pastures fertilized with sulfur.

Thirty yearling Santa Gertrudis-sired heifers (average initial weight 238 kg) were continuously grazed (five heifers/pasture) on six 2-ha oat-wheat small grain pastures for 112 d to determine the effect of fertilization of pastures with urea (U) vs ammonium sulfate (AS) on mineral status and performance of heifers. Pastures were fertilized with either U, at 200 kg/ha, or AS, at 438 kg/ha, to provide 92 kg of N/ha in November 1987 and March 1988. Ammonium sulfate provided 107 kg of S/ha. Forage samples were collected during each month. Heifers were initially weighed following an overnight fast and at the end of four consecutive 28-d intervals (Periods 1 to 4). Serum and ruminal fluid were collected on d 56 and 112. Pastures fertilized with AS had a greater (P less than .10) in vitro dry matter disappearance during Periods 2 and 3. Ammonium sulfate-fertilized pastures had greater than (P less than .05) S concentrations from January 29 through termination of the trial. There were no differences in ADG (P less than .28) or gain/ha (GPH; P less than .43) over 112 d; however, heifer ADG was greater (P less than .08) in Period 3 and tended to be greater (P less than .16) in Period 2 for those animals grazing U-fertilized pastures. Pastures receiving AS produced less (P less than .04) GPH during Period 2. Ammonium sulfate fertilization in this trial had no effect on forage K, Ca, P, Mg, Cu, or Mo mineral concentrations or on serum mineral and ruminal VFA concentrations, but it did result in an increase in IVDMD and a trend for decreased ADG apparently associated with a decrease in forage intake.     

Effects of energy and protein supplementation of ammoniated tropical grass hay on the growth and carcass characteristics of cull cows

Laboratory, digestion and growth studies were used to evaluate energy and protein supplements for ammoniated (4% of the forage DM) stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) hay. Ammoniation increased (P less than .05) total N concentration (.7 to .9% vs 1.7 to 2.0%) and in vitro digestion of OM, NDF and ADF and reduced (P less than .05) NDF concentration of stargrass hay. Two digestion (3 x 3 Latin square, 250-kg steers) and two growth (400-kg Brahman crossbred cull cows, eight head per pasture, two pastures per treatment, November through February) trials evaluated citrus pulp or liquid cane molasses (Trial 1) and molasses or molasses plus cottonseed meal (Trial 2) supplementation of ammoniated hay. Supplementation with byproduct energy sources, citrus pulp or molasses (either alone or with cottonseed meal), improved (P less than .05) OM digestibility but reduced (P less than .05) NDF and ADF digestibilities. Apparent nutrient digestibilities were similar (P greater than .05) between diets supplemented with citrus pulp and molasses and between diets supplemented with molasses and molasses plus cottonseed meal. In Trial 1, ADG by cull cows was greater (P less than .05) for citrus pulp- (.71 kg) or molasses-(.68 kg) supplemented diets than for hay fed alone (.49 kg). In Trial ADG was greater (P less than .05) for cull cows fed ammoniated hay supplemented with molasses plus cottonseed meal (.85 kg) than for those supplemented with molasses only (.69 kg). Feeding cows over the winter increased their (P less than .05) carcass weight, marbling score, USDA quality grade and lipid percentage of the 9-10-11 rib section compared with cows slaughtered at the beginning of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nonpuberal estrus in beef heifers

The frequency of occurrence of behavioral estrus without subsequent development of functional luteal tissue (termed nonpuberal estrus, NPE), was determined in 43 Simmental X Hereford-Brahman heifers. Blood samples were collected weekly from the start of the study to first behavioral estrus and then daily from d 1 (d 0 = estrus) through d 14 following first and subsequently observed estrous behaviors. All blood samples were analyzed for serum progesterone (P4) concentrations by radioimmunoassay. More heifers (62.8%) exhibited NPE than had luteal development after their first behavioral estrus (37.2%). There was a tendency for fewer light-weight heifers (less than or equal to 240 kg at the start of the experiment) to exhibit a puberal first estrus compared with the heavy-weight (greater than 240 kg at the start of the experiment) heifers (31.2% vs 68.8%, respectively; P = .12). Heifers that had a puberal first estrus were older (376 +/- 12 d vs 334 +/- 9 d, P less than .05) compared with heifers that had NPE. Weight at first behavioral estrus was similar between heifers that had a puberal first estrus and those that had NPE (298 +/- 8 kg and 289 +/- 6 kg, respectively). More heifers that had a puberal first estrus also had an elevation in serum P4 concentrations before that first estrus (64.3% vs 20.0%, P less than .05), and the serum P4 elevation was greater (2.5 +/- .4 ng vs 1.2 +/- .1 ng, P less than .05) than heifers that had NPE. We have concluded from these results that NPE is a common occurrence in heifers approaching puberty.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of growth-promoting agents and season on yearling feedlot heifer performance

Angus x crossbred heifers (270 per trial) were used in an experiment conducted over one 105-d summer and one 104-d winter feeding period. Treatments were identical for each trial and included: 1) control, 2) estrogenic implant (E), 3) trenbolone acetate implant (TBA), 4) E + TBA (ET), 5) melengestrol acetate (MGA) in the feed, and 6) ET + MGA (ETM). Each treatment was replicated in five pens, with nine heifers per pen in each season. Initial weights (mean = 384 kg, SE = 57) were the same for each season. There were no treatment x season interactions for final BW, ADG, G:F, water intake, or carcass characteristics. Heifers receiving a growth-promoting agent were 11.6 kg (SE = 4.08) heavier and gained 0.108 kg/d (SE = 0.04) more (P < 0.05) than control heifers. Heifers receiving ET gained 0.09 kg/d (SE = 0.032) more (P = 0.05) than heifers not receiving ET. Heifers receiving ET (with and without MGA) had greater G:F (P < 0.05) than control, E, and TBA heifers. Carcass weights of ET-treated heifers were greater (P < 0.05) than carcass weights for unimplanted heifers, those fed MGA only, and heifers receiving either E or TBA implants. Marbling scores were increased (P < 0.05) by feeding MGA to ET-treated heifers. Water intake was greater (P < 0.01) in the summer (31 L/d) than in the winter (18 L/ d), with no difference among implant treatments. Heifers fed in the winter had heavier carcasses, less 12th-rib fat, greater marbling scores, larger LM area, and a greater incidence of liver abscesses than heifers finished in the summer (P < 0.01). A treatment x season interaction (P = 0.07) was evident for DMI during the 35-d coldest and hottest portions of the year. Heifers fed MGA and implanted with ET tended (P = 0.07) to have greater DMI in the summer but lesser DMI in the winter. In general, differences among growth-promotant programs were relatively similar over the entire summer and in winter.     

Efficacy of vaginal spaying and anabolic implants on growth and carcass characteristics in beef heifers

Ninety crossbred beef heifers averaging 260 kg were blocked by weight and allotted randomly to 15 pens of six heifers each, with three replicates per treatment. The treatments were spayed heifers (S); intact heifers (I); S + Synovex-H7 (SH); I + Synovex-H (IH); and S + Synovex-S7 (SS). The heifers were spayed vaginally with a Willis instrument; intact heifers were rectally palpated for reproductive soundness. Heifers were fed a growing diet (55 d), re-implanted and subsequently fed a finishing ration (73 or 101 d). All heifers were observed for estrus daily at approximately 0600 and 2000 until d 69. A jugular vein blood sample was obtained from each heifer on d 48, 55, 62 and 69 for blood progesterone analysis. Results of blood progesterone analysis and reproductive tract examination indicated that two spayed heifers were incompletely spayed, a 96% success rate. The SH and SS heifers continued to exhibit estrous behavior despite being successfully spayed. Heifers implanted with Synovex-H had greater (P less than .01) ADG and were more efficient (P less than .03) than nonimplanted heifers. The SS heifers had greater ADG (P less than .05) during the finishing phase than SH heifers, but no advantage of SS over SH was apparent during the growing phase. The overall ADG response to implantation was fourfold greater (P less than .07) in the spayed heifers than in the intact heifers (32 vs 8%). Heifers implanted with Synovex-H had greater adjusted hot carcass weight (P less than .02) and ribeye area (P less than .002) than nonimplanted heifers. For adjusted live weight and ribeye area, the response to implantation was approximately threefold greater in the spayed heifer than the intact heifer. These results demonstrate that spaying and implanting heifers can increase rates and efficiency of gain even though behavioral estrus is not eliminated.     

Intake restriction strategies and sources of energy and protein during the growing period affect nutrient disappearance, feedlot performance, and carcass characteristics of crossbred heifers.

Two trials were conducted to evaluate intake restriction, energy, and protein source on the performance and carcass merit of heifers limit-fed corn gluten feed. Trial 1 crossbred heifers (n = 140) were allotted to ad libitum wet corn gluten feed (WCGF)-hay, ad libitum WCGF-corn, WCGF-corn continuously limit-fed to achieve a gain of 1.1 kg/d or WCGF-corn fed in the following sequence: 70% of ad libitum for 20 d, ad libitum for 20 d, and 2 d common intake during the 84-d growing period. One-half of these restricted-refed heifers received a rumen-undegraded protein supplement, and the other half received a rumen degraded protein supplement. Heifers were fed a common finishing diet ad libitum subsequent to the growing period. Heifers offered ad libitum WCGF-hay and WCGF-corn were slaughtered at a common compositional fat end point. Heifers limit-fed WCGF-corn were slaughtered at the same time as heifers offered ad libitum WCGF-corn, regardless of subcutaneous fat cover. Limit-feeding WCGF-corn diets to growing heifers reduced ADG (P < or = 0.01) but did not compromise feed efficiency. Method of intake restriction, continuous or ad libitum-interrupted, and supplemental protein source did not affect combined growing-finishing performance. However, when fed for a common length of time, the average of the limit-fed heifers had lighter carcass weights (P < or = 0.01) and lower (P = 0.04) marbling scores. Heifers offered ad libitum WCGF-hay gained slower (P < or = 0.01) and less efficiently (P < or = 0.01) than heifers offered WCGF-corn. Trial 2 crossbred heifers (n = 222) were allotted to dry corn gluten feed (DCGF)-corn ad libitum or restricted to 80% of ad libitum for 42, 84, or 126 d; or ad libitum corn silage or DCGF-corn silage at 80% of ad libitum for 84 d. Feed efficiency (P = 0.07) and ADG (P = 0.08) tended to behave quadratically, being poorer for heifers limit-fed for 126 d during the growing period. Heifers limit-fed DCGF-corn gained more efficiently (P = 0.05) than heifers grown on ad libitum corn silage. Limit-feeding CGF-corn to growing beef heifers can be used to achieve moderate rates of gain without compromising feed efficiency. However, limit-feeding during the growing period may result in lighter weight carcasses with lower quality grades if not fed to the same fat end point as heifers grown with free access to concentrate.     

Fetal growth of beef calves. I. Effect of prepartum dietary crude protein on birth weight, blood metabolites and steroid hormone concentrations

Fifty-nine crossbred heifers (427 kg) bred to one Hereford sire were randomly assigned at 75 d prepartum to two diets. Heifers were individually fed, and diets were isocaloric but contained either a low (LP = 81% NRC, .56 kg/d) or high (HP = 141% NRC, .98 kg/d) level of crude protein. Jugular vein cannulae were inserted into 16 LP and 16 HP heifers at 10 prepartum. Daily preprandial blood samples that were collected until parturition were analyzed for serum estradiol-17 beta (E2), progesterone (P4), glucose (G) and urea nitrogen (UN). Heifers fed LP gained slower than HP-fed heifers before calving (.73 vs 1.02 kg/d; P less than .01); immediate post-calving weights and condition scores were 418 vs 444 kg (P less than .01) and 5.4 vs 6.1 (P less than .01; LP vs HP, respectively). Calf birth weights (35.3 vs 36.1 kg), average calving difficulty score (1.6 vs 1.6) and percent assisted births (35.5 vs 35.7%) did not differ (P greater than .10; LP vs HP, respectively). Prepartum concentrations of UN (6.2 vs 13.5 mg/dl) and G (52.9 vs 58.2 mg/dl) were lower (P less than .05) and P4 (5.94 vs 4.26 ng/ml) was higher (P approximately equal to .07) in LP heifers. Prepartum concentration profiles were related to calving difficulty score (CD, 1 = no assistance to 3 = hard pull) for E2 (CD1 vs CD2 + CD3, P less than .01; CD2 vs CD3, P approximately equal to .01), P4 (CD1 vs CD2 + CD3, P less than .05), G (CD1 vs CD2 + CD3, P less than .05) and UN (CD2 vs CD3, P less than .05). After calving, all dams were maintained together on pasture and supplemented with alfalfa hay and grain mix until adequate range forage was available to maintain weight gains. Dams that were fed LP prepartum gained faster than HP dams during this period (.49 vs .15 kg/d; P less than .01). Prebreeding weights (443 vs 453 kg; LP vs HP) and condition scores (5.1 vs 5.1) did not differ, nor was the postpartum interval affected (44 vs 40 d; LP vs HP). There was no effect of dietary protein on dystocia or postpartum interval, although there were diet-induced differences in body weight and condition of the dams at calving. Results indicate that differences in prepartum profiles of serum steroid hormones and metabolites may be related to dystocia, in addition to relative fetal oversize.     

Feedlot performance of beef heifers implanted with Synovex-H: effect of melengestrol acetate, ovariectomy or active immunization against GnRH

The effects on anabolic steroid implantation on feedlot performance and carcass composition and quality were examined in control (CNTRL), ovariectomized (OVX) or melengestrol acetate-fed (MGA) beef heifers or heifers actively immunized against GnRH (Anti-GnRH). Heifers (n = 112) were assigned randomly to a 2 x 4 factorial experiment. The two classes were made up of heifers not implanted and those implanted with Synovex-H. The four treatments were 1) CNTRL, 2) MGA, 3) OVX and 4) Anti-GnRH. Heifers were housed in individual pens and fed a high-energy diet for the 4-mo study. Synovex-H increased final live weight (P less than .005), carcass weight (P less than .005), ADG (P less than .0001) and feed efficiency (P less than .005) but did not alter carcass quality and yield grade (P greater than .05). Synovex-H increased deposition of protein (P less than .0001) and reduced deposition of fat (P less than .0001). Oral administration of MGA had no significant effect on feedlot performance or carcass quality. For heifers not implanted, active immunization against GnRH, but not ovariectomy, depressed ADG (P less than .05) and increased fat deposition (P less than .05) while reducing protein deposition (P less than .05). These effects of active immunization were reversed by concurrent administration of Synovex-H. Feedlot performance and carcass composition of heifers were improved by administration of anabolic steroids. When heifers were housed singly, neither ovariectomy, active immunization against GnRH nor oral administration of MGA improved feedlot performance of heifers implanted with Synovex-H.     

Effects of breed and wintering diet on heifer postweaning growth and development

Fifteen spring-born Angus (AN) and 25 Brangus (BN) weanling heifers were used in a 2x5 factorial arrangement of treatments to evaluate the effects of breed and postweaning winter diet on heifer growth and development. Dietary treatments were warm-season perennial grass hay (H), ammoniated H (AH), H plus .68 kg/d cottonseed meal (HP), H plus .45 kg/d cottonseed meal plus 1.37 kg/d ground corn (HPE) and HPE plus 200 mg/d monensin (HPEM). Mean initial weight and age for the 107-d feed trial were 207 kg and 270 d. Brangus had .06 kg greater (P less than .05) ADG than AN during the trial. Although digestible DM intake (DDMI) relative to body weight was greater (P less than .10) for AN than for BN, ADG:DDMI was greater (P less than .05) for BN than for AN. Heifers fed H and AH lost weight, but heifers fed AH had 50% (P less than .05) less daily weight loss than those fed H. Daily gain increased (P less than .05) incrementally in response to sequential supplement additions of cottonseed meal (AH vs HP; -.10 vs .17 kg), ground corn (HP vs HPE; .17 vs .29 kg) and monensin (HPE vs HPEM; .29 vs .39 kg). Hay DM intake relative to body weight and DDMI were increased (P less than .01) by ammoniation. Intake did not differ between HPE and HPEM. Diet affected age at puberty (P less than .05), which decreased with increased dietary components. Weight differences among diet groups following the winter feed trial were largely eliminated prior to breeding. Nevertheless, H- and AH-fed heifers collectively weighed less (P less than .01) prior to breeding than did heifers of supplemented diet groups. Reproductive development tended to be adversely affected by weight loss during the postweaning period.     

Effect of early weaning on the performance of three-year-old,first-calf beef heifers and calves reared in the subtropics

The objective of this study was to investigate the effectiveness of early weaning fall-born calves on heifer and calf performance in Florida. Over two consecutive years, 3-yr-old Braford and Brahman x Angus first-calf heifers were assigned randomly to one of two treatments; early-weaned (EW, n = 20 and 30 for yr 1 and 2, respectively) and normal-weaned (NW, n = 20 and 38 for yr 1 and 2, respectively). Calves were EW on January 23 and 3 for yr 1 and 2, respectively. Following EW, all first-calf heifers were returned to bahiagrass (Paspalum notatum) pastures with the mature cowherd. Early-weaned calves were maintained on annual ryegrass (Lolium multiflorum) pastures at 8.2 and 10.7 calves/ha for yr 1 and 2, respectively, and were provided supplemental grain mixture (14% CP) at 1.0% of BW daily. Normal-weaned calves remained with their dams in the mature cowherd on bahiagrass. Final calf BW was collected on April 17 (d 84) and April 24 (d 111) for yr 1 and 2, respectively. Early-weaned calves had a greater (P < 0.001) ADG (0.17 kg/d) in yr 1, but a lower (P < 0.001) ADG (-0.24 kg/d) in yr 2 compared with NW calves. Early weaning resulted in heavier first-calf heifers with greater BCS at the time of normal weaning (August 1; 491 vs. 452 kg, with BCS = 6.34 vs. 4.75 for EW and NW heifers, respectively; SEM = 5.0 and 0.07). Heifers with EW calves had a higher (P < 0.07) pregnancy rate during both years than normal-weaned heifers (89.5 vs. 50.0 and 96.7 vs. 80.0% pregnant during yr 1 and 2, respectively). Early-weaned, first-calf heifers also had a lower (P < 0.05) calving interval in yr 2 (384 vs. 404 d; SEM = 6.0). These data suggest that EW will improve body condition of first-calf heifers resulting in an increased pregnancy rate. Early-weaned calves maintained on winter ryegrass provide producers with the ability to optimize early-weaned calf performance, while capitalizing on low cost of gain and favorable spring markets.     

Reproductive performance and profitability of heifers fed to weigh 272 or 318 kg at the start of the first breeding season

Reproductive performance and weaning weight of the first calf was determined in 221 Brahman crossbred heifers fed to weigh either 272 (TW1) or 318 kg (TW2) at the start of their first breeding season (target weight). Heifers were divided into light- (below average) and heavyweight (above average) groups on the basis of initial weight. Within each target weight, heifers were fed in three lots. One lot contained lightweight heifers, the second contained heavy heifers and the third was composed of one-half heavy- and one-half lightweight heifers. Heifers were fed for 200 d before the start of the first breeding season. More heifers in TW2 showed estrus and became pregnant in the first 20 d of the breeding season and more were pregnant at the end of the first breeding season. These same differences in reproductive performance were also noted the second year. Each heifer exposed in TW2 weaned 43.4 kg more calf than those in TW1. An average heifer in TW2 was fed 220 kg more corn and 100 kg less hay than a corresponding heifer in TW1. Estrus and pregnancy rate for lightweight heifers in TW1 and TW2 were not improved by sorting and feeding them separately.     

A new phytase expressed in yeast effectively improves the bioavailability of phytate phosphorus to weanling pigs

We have recently expressed a new phytase enzyme in a yeast system. Three experiments with a total of 140 weanling crossbred pigs were conducted to examine the efficacy of this enzyme in improving the bioavailability of phytate-P in corn-soybean meal diets to young pigs. Experiment 1 compared the efficacy of this new phytase with a commercially available phytase (Natuphos, BASF) for 4 wk at an inclusion level of 1,200 U/kg of diet. Experiment 2 compared the responses of pigs to four doses of the new phytase supplementation (300, 600, 900, and 1,200 U/kg of diet) for 4 wk. Experiment 3 compared the efficacy of this new phytase and Natuphos at a marginally optimal dose (700 U/kg of diet) for 5 wk. A group of pigs were fed the P-deficient basal diet as a negative control in Exp. 1, and a group of pigs were fed the basal diet plus .17 or .22% inorganic P as a positive control in all experiments. In Exp. 1, pigs fed the two sources of phytase had similar ADG (564 vs 567 g), gain/feed (.597 vs .589), plasma inorganic P concentrations (8.9 vs 8.4 mg/dL), and mobility scores (4.25 vs 4.46) that were higher (P < .05) than those of the negative control. In Exp. 2, plasma inorganic P concentration was a fairly linear response to the phytase dose (r > .83) at wk 1 and 2. Overall ADG of pigs also tended to increase with the phytase dose (P = .15). In Exp. 3, pigs fed the two sources of phytase had ADG (483 vs 506 g) similar to that of the positive control (508 g). These two groups also had similar plasma inorganic P concentrations (7.7 vs 7.4 mg/dL) that were lower (P < .05) than those of the positive control group (9.7 mg/dL). There was no significant effect of dietary treatments on ADFI in all three experiments. In conclusion, our new phytase was as effective as Natuphos, at the inclusion level of 700 or 1,200 U/kg of a P-deficient, corn-soybean meal diet, in improving phytate-P utilization by young pigs.     

Growth and reproductive traits in beef heifers implanted with zeranol

Weaned replacement heifers were implanted with zeranol at 8 and 11 mo of age in two trials to evaluate growth and reproductive traits. Approximately 100 beef heifers were used in each trial, and the heifers were divided into categories of heavier than average (H) and lighter than average (L) weaning weight. Weight categories were further divided into control (HC and LC) and zeranol-implanted (HI and LI) groups. Heifers were kept in drylot from weaning to just before the start of the breeding season and were fed to reach a predetermined body weight by the start of the breeding season and were fed to reach a predetermined body weight by the start of the breeding season. Rates of gain in the drylot were greater in implanted than in control heifers in both trial 1 (.53 vs .48 kg/d; P less than .09) and trial 2 (.70 vs .63 kg/d; P less than .01). Pelvic areas were greater (P less than .01) in implanted than in control heifers of both trial 1 (175 vs 159 cm2) and trial 2 (175 vs 164 cm2). This increase in pelvic size was still present at the end of the summer pasture period, which followed the drylot period. Zeranol had no major effect (P greater than .10) on age of weight at puberty. Fall pregnancy rate was 16% lower in implanted heifers than in control heifers in trial 1 (62 vs 78%, P = .08) but did not differ in trial 2 (88 vs 87%, I and C, respectively).     

Effects of recombinant DNA-derived somatotropin and dietary energy intake on development of beef heifers: I. Growth and puberty

The effects of dietary energy intake and somatotropin (STH) on growth and puberty were studied in 40 Angus heifers. At an average age of 7 mo (208 +/- 8 d), 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 15.5 mo of age. Body weights (BW), hip heights (HH) and areas of pelvic openings (PA) were measured every 28 d and backfat thicknesses (BF) were measured every 56 d. Plasma progesterone was measured in blood samples taken three times per week beginning at 9 mo of age to determine age at first ovulation. Heifers fed HE were heavier (P less than .01), gained faster (P less than .01) and had greater BF (P less than .01) than those fed LE. Animals treated with STH gained faster (P less than .01) and were heavier (P less than .05) between 12 and 15 mo of age than V-treated heifers. Heifers treated with STH also had less BF (P less than .05) and a tendency for a greater (P = .08) increase in HH than in V-treated heifers. Somatotropin interacted with energy (P less than .05) and age (P less than .01) to influence PA. Somatotropin increased (P less than .01) PA in heifers fed the HE diet but not in those fed the LE diet.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of monensin, estradiol controlled release implants and supplement on performance in grazing steers

Five trials in five locations in the United States involving 512 steers were conducted to evaluate the effect of monensin [200 mg/d in .9 kg of supplement (Ru mensin )] and estradiol-controlled release implants ( Compudose ) administered alone and in combination on average daily gain (ADG) in steers on pasture. The effect of energy supplementation on rate of gain was also evaluated in these same trials. The initial weight of steers averaged 250 kg and the average duration of the five trials was 124 d. Estradiol-controlled release implants increased ADG by 15.6% (.095 kg/d; P less than .0001) and monensin increased ADG by 8.1% (.054 kg/d; P less than .05). The combination of estradiol-controlled release implant and monensin increased ADG by 27.4% (.168 kg/d). Treatment responses were additive relative to ADG response, with no interaction observed between the treatments. Nine-tenths kilograms of an energy supplement/d increased ADG by 12.4% (.073 kg/d; P less than .01).     

Bovine corpus luteum regression and estrous response following treatment with alfaprostol

Two trials evaluated bovine corpus luteum (CL) regression and estrous response following treatment with alfaprostol (AP), a prostaglandin F2 alpha analogue. Expression of at least one estrous cycle (16 to 26 d) and a palpable mid-cycle CL were required prior to random assignment of females to receive 0, .38, .75, 1.50 or 2.25 mg AP/100 kg body weight. Alfaprostol was evaluated in Brahman cows and heifers that were treated on d 11 to 13 (trial 1) and in Simmental X Brahman-Hereford (crossbred) heifers that were treated on d 8 to 10 or d 11 to 13 of the estrous cycle (trial 2). In trial 1, Brahman heifers appeared to require a higher AP dose (greater than .38 mg/100 kg body weight) to elicit luteolysis and expression of estrus than Brahman cows. Alfaprostol treatment (greater than or equal to .75 mg/100 kg body weight) induced (P less than .0001) luteolysis followed by estrus in Brahman cows and heifers. In trial 2, crossbred heifers that received AP on d 8 to 10 appeared to require a higher dose of AP (greater than .38 mg/100 kg body weight) to elicit luteolysis and estrus than heifers that received AP on d 11 to 13 of the estrous cycle. Alfaprostol treatment greater than or equal to .75 mg/100 kg body weight on d 8 to 10 and d 11 to 13 of the estrous cycle induced (P less than .0001) luteolysis followed by estrus in crossbred heifers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of dairy food processing wash water solids as a protein source: I. Forage intake, animal performance, ruminal fermentation, and site of digestion in heifers fed medium-quality hay.

Twelve ruminally, duodenally, and ileally cannulated (average initial BW 313 +/- 20 kg) and 27 intact Hereford heifers (average initial BW 256 +/- 17 kg) were used in two experiments to evaluate dairy food wash water solids (WWS) as a protein source in medium-quality hay diets. Heifers received a basal diet of orchardgrass hay (7.4% CP) and were assigned to one of three supplement treatments: control (C; .9% CP), WWS (18.8% CP)-, and soybean meal (SBM; 19.1% CP)-based supplements (fed at 1.5 kg of DM/d). Supplements were formulated to have similar ME concentrations. Ruminal ammonia concentrations were greater (P less than .10) for WWS- and SBM-supplemented heifers than for C heifers at most sampling times. Moreover, WWS and SBM increased (P less than .10) total VFA (mM) and acetate (mol/100 mol) and lowered propionate (mol/100 mol) at several sampling times. Ruminal fluid volume (liters) was unchanged (P greater than .10) by treatment; however, fluid dilution and flow rate (liters/h) were less (P less than .10) in C heifers than in heifers fed SBM or WWS supplements. Wash water solids and SBM supplementation increased (P less than .10) OM, NDF, and ADF digestibilities compared with C heifers. Feeding WWS and SBM supplements increased BW at 84 d (P less than .10) compared with C-supplemented heifers. Forage intake at 54 and 84 d by heifers supplemented with SBM or WWS was greater (P less than .10) than by C heifers. Control-supplemented heifers had the least, WWS intermediate, and SBM the greatest ADG at 84 d (P less than .10; .14 vs .35 vs .48 kg/d, respectively). These data indicate that WWS may be used as a protein source without serious adverse effects in heifers consuming medium-quality hay for 84 d.