Effects of reduced in utero and post-weaning nutrition on milk yield and composition in primiparous beef cows.

Development and long-term retention of replacement beef females in a semi-arid environment are of a major concern for extensive livestock producers. Furthermore, the demand of not only producing a thriving, healthy calf, but having sufficient milk to support that first calf is essential. To address this issue, we conducted a 3-year study measuring milk production and milk constituent yields in primiparous beef heifers (n=48; 16/year reared under two different feeding regimens) raising steer calves. Cows received 1.8 or 1.2 kg/day winter supplementation for ~80 day before parturition and their heifer calves were then randomly assigned to heifer development treatments that provided ad libitum (AL) or 80% (less than ad libitum (LAL)) of ad libitum feed post weaning. Heifers developed on the AL treatment also received 1.8 kg/day winter supplementation for life, whereas heifers developed on the LAL treatment received 1.2 kg/day winter supplementation for life. Milk production of primiparous cows was measured with a portable milking machine every other week from days 27 to 125 postpartum. Milk yield for the 125-day lactation period was calculated from area under the lactation curve approximated by trapezoidal summation. The ANOVA model included in utero winter nutrition, post-weaning heifer development treatment, year and their interaction. Heifers subjected to the AL treatment reached peak milk yield ~12.3 day later (P=0.02) than heifers receiving LAL treatment. In addition, an in utero nutrition×post-weaning heifer treatment×year interaction existed (P⩽0.04) for milk peak yield, average daily milk yield (kg/day) and nutrient composition (protein, lactose, fat, solids non-fat, g/day). These interactions manifest as changes in magnitude and rank across the 3 years of the study. Livestock production in extensive environments is subject to variations in seasonal precipitation patterns and quality and quantity of grazeable forage and these fluctuations have a large impact on milk yield. In summary, the gestational nutritional environment of a heifer's mother may interact with the heifer's nutrient consumption during post-weaning growth and the current year to trigger variation in year-to-year milk production.

TRIENNIAL REPRODUCTION SYMPOSIUM: Beef heifer development and lifetime productivity in rangeland-based production systems.

Nutritional and environmental factors have been shown to cause epigenetic changes that influence characteristics of the offspring throughout life. In livestock, small differences in nutrition during gestation may alter lifetime production efficiency of offspring. Therefore, the potential for fetal programing should be considered when determining supplemental feeding strategies during gestation. For example, female offspring born to cows grazing dormant winter pasture supplemented with 1.1 kg/d of alfalfa hay during the last third of gestation were 10 kg heavier and had greater BCS at 5 yr of age than those from dams supplemented with 1.8 kg/d of alfalfa hay. These differences were beneficial for maintaining reproductive performance in offspring managed with fewer harvested feed inputs. Evaluation of female offspring from cows wintered on either low-quality or high-quality pasture for 30 to 45 d during the fifth to sixth month of gestation indicated a trend for longer duration of productivity in daughters from cows wintered on improved pasture. In recent studies comparing offspring from cows with or without protein supplementation while grazing dormant winter range during late gestation, heifers from protein-supplemented dams had greater BW at weaning. This BW increase persisted throughout pregnancy and to subsequent calving, and pregnancy rates were greater in heifers from protein-supplemented dams. Heifers from protein-supplemented dams had lower G:F compared with heifers from unsupplemented dams. Therefore, in utero exposure to nutritionally limited environments (nonsupplemented dams) may promote greater feed efficiency in the heifer offspring later in life. Nutrition during postweaning development may also affect lifetime productivity. Heifers developed on low-quality native range with RUP supplementation had greater retention beyond 3 yr of age than cohorts developed in a feedlot with higher quality feed and greater ADG. Collectively, these examples show nutritional management strategies used during gestation and development may influence lifetime productivity.

Water temperature impacts water consumption by range cattle in winter.

Water consumption and DMI have been found to be positively correlated, and both may interact with ingestion of cold water or grazed frozen forage due to transitory reductions in the temperature of ruminal contents. The hypothesis underpinning the study explores the potential that cows provided warm drinking water would have increased in situ NDF and OM disappearances and a more stable rumen temperature, drink more water, and lose less BW during the winter. This hypothesis was tested in 3 experiments. In Exp. 1, ruminal extrusa (93.1% DM, 90.2% OM, 81.1% NDF [DM], and 4.9% CP [DM]) were randomly allocated to 1 of 5 in vitro incubation temperatures. In 2 independent trials, temperatures evaluated were 39, 37, or 35°C (trial 1) and 39, 33, or 31°C (trial 2). In Exp. 2, 4 pregnant rumen cannulated cows grazing in January were fitted with Kahne (KB1000) temperature continuous recording boluses for 22 d. Two grazed in a paddock provided cold water (8.2°C) and 2 in a paddock provided warm water (31.1°C). Two in situ trials were conducted placing 6 in situ bags containing 2 g of winter range ruminal extrusa in each of the 4 ruminally cannulated cows and incubating bags for 72 h for measurement of NDF disappearance. In Exp. 3, 6 paddocks ( = 3/water treatment) were grazed by 10 to 13 pregnant crossbred Angus cows from December through February across 3 yr from 2009 to 2012. Water intake per paddock was measured daily and ambient temperature was recorded. Motion-activated cameras were used to determine the time of day water was consumed and the number of cow appearances at water. In Exp. 1, rate and total gas production ( < 0.05) and NDF disappearance ( < 0.001) at 48 h was reduced by each incubation temperature below 39°C. In Exp. 2, ruminal temperature for cows supplied with warm water dropped below 38°C 1.5% of the time whereas ruminal temperature for cows provided cold water dropped below 38°C 9.4% of the time ( < 0.01). Drinking water temperature did not alter in situ OM or NDF disappearance. In Exp. 3, cows with access to warm water consumed 30% ( < 0.05) more water than cows provided cold water. In this study, there were energetic costs to range cows proportional to consumption of water at temperatures less than body temperature. The magnitude of these costs were found to be less than the heat increment because no improvement to BW gain, BCS change, or calf birth weight were found for cows consuming warmed water.

Effects of fat and/or methionine hydroxy analog added to a molasses-urea-based supplement on ruminal and postruminal digestion and duodenal flow of nutrients in beef steers consuming low-quality lovegrass hay.

Five crossbred beef steers (initial BW = 338.6 ± 7.8 kg) fitted with ruminal and duodenal cannulas were used in a 5 × 5 Latin square design experiment to evaluate the effects of methionine hydroxy analog (MHA) and/or yellow grease (fat) added to a molasses-urea-based supplement on intake and characteristics of digestion. Steers were fed low-quality hay (long-stem lovegrass : 3.3% CP, 76.8% NDF; DM basis) ad libitum and supplemented with 0.91 kg/d (as fed) of 1 of 4 supplements in a 2 × 2 + 1 factorial arrangement of treatments. Supplemental treatments were 1) control (no supplement, NC); 2) molasses-urea liquid supplement (U); 3) U containing (as-fed basis) 1.65% MHA (UM); 4) U containing (as-fed basis) 12% fat (UF); and 5) U containing (as-fed basis) 1.65% MHA and 12% fat (UMF). Total and forage OM intake (kg/d and as % of BW) increased ( < 0.01) with molasses-urea, decreased ( ≤ 0.04) with MHA, and were not affected ( = 0.61) with fat supplementation. Total tract NDF digestibility increased ( = 0.01) with molasses-urea supplementation, and was less ( = 0.01) for fat than for nonfat supplementation. Total and microbial N flowing to the duodenum increased ( = 0.01) with molasses-urea supplementation. Although, total N flowing to duodenum was not affected ( = 0.27), microbial N decreased ( = 0.01), and nonammonia nonmicrobial N (NANMN) increased ( = 0.01) with fat supplementation. Extent of in situ OM and NDF digestibility at 96 h increased ( = 0.01) with molasses-urea supplementation, but were not affected ( ≥ 0.14) by either MHA or fat supplementation. Duodenal flow of total AA, essential AA, and nonessential AA increased ( ≤ 0.02) with molasses-urea supplementation. Total and nonessential serum AA concentration decreased ( < 0.01) with molasses-urea supplementation. Total ruminal VFA concentration increased ( = 0.01) with molasses-urea supplementation, and was not affected ( ≥ 0.14) by MHA or fat supplementation. Fat can be used in molasses-urea liquid supplements for cattle consuming low-quality forage to increase energy intake without negatively affecting forage intake or characteristics of digestion. However, adding MHA did not further improve the response to urea supplementation of cattle consuming low-quality forage. Conversely, the inclusion of MHA on urea supplement decreased forage intake.

BEEF SPECIES SYMPOSIUM: Can we build the cowherd by increasing longevity of females?

Increasing longevity of beef cows by decreasing the proportion culled due to reproductive failure provides an efficient process to rebuild a cow herd and can reduce number of replacements needed to sustain a constant herd size. Rate of reproductive failure varies due to cow age, where failure in cows 2 to 4 yr of age is often greater than in cows 5 to 7 yr of age. In addition, BW of cow and calf at weaning increase as cows advance from 2 to 5 yr of age. The cumulative effect of increasing retention of young cows is improved production efficiency through decreased replacement rate and changing age structure of the herd resulting in a greater proportion of cows at maximal production potential for calf BW at weaning and cow BW at time of culling. Calculations from cow age-specific culling and BW data from commercial and research herds indicated that reducing replacement rate from 18% to 14% resulted in a 23% increase in calf BW weaned and a 2% increase in cull cow BW per pregnant replacement heifer going into the herd. Although improving longevity increases production efficiency, genetic advancement in sustained reproductive function is challenging, as it is the sequential culmination of the annual repetition of numerous discrete physiological processes, each ending in a qualitative response. Successful completion of one process is prerequisite to evaluating subsequent processes. These physiological processes are subject to nutritional threshold requirements that may vary due to genetic potential for other production traits such as milk, growth, and mature size resulting in genetic-by-nutrition interactions. This is in contrast to most traits for which EPD exist, where genetic-by-environment interactions are not considered to be significant. Extensive research concerning impact of limited nutrition on reproduction has led to recommendations that heifers and cows be fed to a threshold BW or BCS to ensure reproductive success; a process that masks nutritional interactions that might otherwise result in reproductive failure. This management approach minimizes selection for animals capable of sustained reproductive function under limited nutritional environments. Rearing and managing cows under nutritionally limited environments may lead to adaptations that result in relatively high levels of reproductive success under lower input levels. Such adaptation may improve chances for longer retention in their offspring in nutrient-limited environments.

Sources of variability in livestock water quality over 5 years in the Northern Great Plains.

Concentrated dissolved minerals in naturally occurring water accessible to livestock grazing semiarid landscapes can negatively influence animal productivity and well-being. Twelve indicators of water quality (Ca, Cl, Fe, F, Mg, Mn, Na, nitrate N, pH, SO4, total dissolved solids [TDS], and temperature) were measured at 45 livestock water sites over 5 yr from 2009 through 2013 at the 22,257-ha USDA-ARS Fort Keogh Livestock and Range Research Laboratory (Miles City, MT) to estimate variation. Water was sampled from 4 sources: 1) flowing surface water, 2) groundwater, 3) reservoirs, and 4) springs. The sampled area was classified by 3 cardinal compass bearings (locations): 1) north, 2) southeast, and 3) southwest of the Yellowstone River. Samples were collected twice yearly in 2 seasons, May (wet) and September (dry). Year, location, source, and season and their interactions were analyzed as a 5 × 3 × 4 × 2 factorial arrangement of treatments. A location × year interaction (P < 0.04) was found for Mg, Na, SO4, and TDS. The southwest location had the greatest concentrations in 2012 of Na, SO4, and TDS. A source × year interaction (P < 0.02) was found for Ca, Fe, F, Mg, Mn, Na, SO4, TDS, and temperature. Iron, Mg, and Mn had the greatest concentrations in flowing surface water in 2012. Greater and then lower precipitation in 2011 followed by below-average precipitation in 2012 was associated with elevated mineral concentrations in sources in the southwest location and flowing surface water sources demonstrating sources of water quality variability within time and space at the study site. Average concentrations of Ca, Cl, Mg, and nitrate N and pH levels across sources and locations did not exceed the upper maximum intake level for beef cattle. In contrast, concentrations of F, Fe, Na, SO4, and TDS at times exceeded the upper maximum level for beef cattle, indicating these minerals may negatively impact range beef cattle performance.

Differing manifestations of respiratory syncytial virus-associated severe lower respiratory tract infections in human immunodeficiency virus type 1-infected and uninfected children.

BACKGROUND: Respiratory syncytial virus (RSV) causes increased morbidity and mortality in immunocompromised children. The outcome of RSV-associated lower respiratory tract infections (LRTI) in HIV-infected children, is less well described. METHODS: Children from a prospective study evaluating the etiology of

Acylated flavonol glycosides from cabbage leaves.

Seven flavonol glycosides were isolated from a leaf extract of cabbage and characterized by chemical and spectroscopic methods including 1H and 13C NMR and negative ion FAB-MS. Five compounds were new natural products or were fully characterized for the first time. They are derivatives of kaempferol-3-O-beta-D-sophoroside-7-O-beta-D-glucoside acylated at C-2"' with either caffeic acid, p-coumaric acid or ferulic acid, and of quercetin-3-O-beta-D-sophoroside-7-O-beta-D-glucoside acylated with either caffeic acid or ferulic acid. Kaempferol-3-O-beta-D- sophoroside-7-O-beta-D-glucoside and kaempferol-3-O-beta-D-(2-sinapoylsophoroside)-7-O-beta-D-glucoside were found for the first time in cabbage, but they have previously been found in other Brassica species.

Effects of varying levels of undegradable intake protein on endocrine and metabolic function of young post-partum beef cows.

Twelve Hereford x Angus heifers, 2.5 year, 492 +/- 17 kg (BCS = 5 +/- 0.5), were randomly assigned to one of three supplements, stratified by calving date and calf sex. Treatments consisted of a daily equivalent of: (1) low undegradable intake protein (UIP) (L: 908 g per cow per day; 36% CP, 108 g UIP), (2) middle UIP (M: 908 g per cow per day; 36% CP, 165 g UIP), and (3) high UIP (H: 908 g M + 243 g feather meal per cow per day; 46% CP, 335 g UIP). Cows were fed sudan grass hay (7.3% CP, as fed) daily at 2% BW (as fed). Supplement was individually fed twice weekly from Week 2 to Week 11 post-partum. Cow body weight (BW), backfat (BF) and rumpfat (RF) thicknesses decreased in all cows, (P < 0.05) yet did not differ among treatments (P > 0.10). There were no differences among treatments in calf BW (P > 0.10). Serum insulin, blood urea nitrogen (BUN), milk components and yield did not differ among treatments (P > 0.10). Area under the curve (AUC) for serum LH was greater (P = 0.07) in H versus L and M (809 versus 599 and 607 +/- 69 U, respectively). No differences were observed in FSH AUC or mean serum concentrations (P > 0.10). Uterine pH did not differ among treatments or between supplement versus non-supplement days (P > 0.10). Serum progesterone remained below I ng/ml for all cows indicating absence of return to estrus. Under the conditions of this study, BW, BF, RF, serum insulin, BUN, milk components, and yield, uterine pH and serum FSH were not affected by level of UIP. However, supplement containing high levels of UIP enhanced GnRH-induced LH release.

Influence of DL-methionine supplementation on growth, ruminal fermentation and dilution rates in heifers.

A 3 X 3 replicated Latin square design was used to evaluate three isonitrogenous supplements designed to supply 250 g crude protein (CP) daily. Measurements included in situ dry matter (DM) and neutral detergent fiber (NDF) fermentation and ruminal dilution rates. Supplements contained beet pulp plus DL-methionine and urea (MET), ammonium sulfate and urea (U) or soybean meal (SBM). Six mature, ruminally cannulated crossbred beef cows were individually fed supplement and a mixture (63% NDF and 6.1% CP) of chopped 75% grass hay and 25% barley straw in ad libitum. Fermentation rate of DM was increased (P less than .05) by 30% with MET in comparison to SBM or U (9.54 vs 7.28% and 7.74%/h for MET, SBM and U, respectively). Even though MET improved fermentation rate by 30%, particle dilution rate was more important in affecting ruminal digestibility than fermentation rate. Two 90-d heifer growth trials were conducted to evaluate similar supplements. Supplements similar to those used in the in situ trial were mixed with roughage to provide a complete diet balanced for .3 kg daily gain. Heifers consumed 112% of the National Research Council CP requirement. Weight gain, intake and feed conversion were similar (P greater than .10) for all treatments. In heifer trial 2, 90% of the National Research Council CP requirement was fed. The heifers supplemented with MET and SBM had faster (P less than .05) weight gains than heifers receiving U. These studies show that feeding DL-methionine with urea, as compared with feeding an isonitrogenous supplement containing SBM, increased the fermentation rate of DM.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of ruminal escape protein or fat on ruminal characteristics of pregnant winter-grazing beef cows.

The effects of ruminal escape protein and added fat on ruminal characteristics were determined at 9, 4 and 1 wk prior to calving in 20 prepartum beef cows. Cows grazed native foothills range from mid-December to early March in two different years. Cows were randomly allotted to five groups (four cows per group) and fed (g/d) either no supplement (control); 570 soybean meal (SOY); 450 soybean meal and 230 blood meal (SOY+BM); 140 soybean meal, 16 urea and 450 corn gluten mean (SOY+CGM); or 570 soybean meal and 210 animal fat (SOY+FAT). Supplements were designed to supply similar quantities of ruminally degraded protein while varying in escape protein quantity and source (SOY+BM and SOY+CGM). Control animals had the lowest (P less than .03) ruminal ammonia concentration (4.5 to 8.9 mg/dl), but values were similar (8.1 to 12.3 mg/dl) for the other treatments. In both trials, NDF disappearance rate was lowest for the control, 1.85%/h (P less than .01), and tended to be lower (P less than .07) in SOY (2.25%/h) than for the mean of SOY+BM and SOY+CGM (2.62 and 2.84%/h). Ruminal fluid volume tended to be greater (P less than .14) and dilution rate lower (P less than .13) for the mean of SOY+BM and SOY+CGM than for SOY in both trials. Particulate dilution rate was lower (P less than .01) for the mean of SOY+BM and SOY+CGM (2.33 and 2.75%/h) than for SOY+FAT (3.17%/h) in Trial 2. These results indicate that supplemental escape protein from blood meal or corn gluten meal can influence ruminal characteristics, perhaps due to a continuous release of amino acids and(or) branched-chain organic acids.

Influence of protein degradability in range supplements on abomasal nitrogen flow, nitrogen balance and nutrient digestibility.

Two metabolism trials were conducted with yearling steers fed mature native forage to measure the effect of supplemental protein degradability on selected metabolic variables. Supplements contained 40% crude protein equivalence. In Trial 1, four abomasal-cannulated steers weighing 290 to 379 kg were fed supplements containing the following N sources: (1) 15% corn, 85% urea (U); (2) 100% soybean meal (SBM); (3) 10% corn, 40% soybean meal, 50% urea (SBM-U) and (4) 14% corn, 36% blood meal, 50% urea (BM-U). Equal portions of the daily diet (2.2% of body weight) were fed every 2 h. Treatment differences were not significant for organic matter digestibility, abomasal organic matter flow, nonammonia N flow, feed N flow, bacterial N flow and efficiency of microbial protein synthesis. There was a positive (P less than .05) relationship between quantity of slowly degraded protein fed and nonammonia N flow (r = .97) or feed N flow (r = .98). Escape N was determined to be 21.5, 16.5 and 54.2% in SBM, SBM-U and BM-U supplements, respectively. In the second trial, no supplement, SBM, SBM-U and BM-U were fed in a N balance trial. Dry matter, crude protein and neutral detergent fiber digestibilities were higher (P less than .05) for steers fed supplemented diets. Acid detergent fiber digestibility was higher (P less than .05) for steers supplemented with SBM than steers fed the unsupplemented diets. Nitrogen retention was greater (P less than .05) for cattle fed SBM and BM-U than for cattle fed SBM-U or no supplement.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of supplemental protein source and metabolizable energy intake on nutritional status in pregnant ewes.

Two experiments were conducted to evaluate effects of supplemental protein source and ME intake (Exp. 1) on ewe nutritional status during pregnancy. Forty-two mature Targhee ewes were allotted randomly in Exp. 1 to one of six treatments (n = 7) using a 2 x 3 factorial arrangement. Ewes were individually fed chopped barley straw and supplements containing either urea (U), soybean meal (SBM), or blood meal (BM) plus SBM during the 84-d experiment. Straw and supplement intakes were adjusted to meet either 80 or 100% of ME requirements. In Exp. 2, 30 pregnant Targhee ewes that were allotted randomly to one of three groups (n = 10) were individually fed protein supplements similar to those in Exp. 1 and had group access to long-stem barley straw. In Exp. 1, ewes fed BM + SBM gained more (P less than .05) weight, lost less (P less than .05) body condition, and had increased (P less than .05) wool fiber length compared with ewes fed U; SBM ewes were intermediate (P less than .05) in response. Ewes fed BW + SBM had increased (P less than .05) blood urea N and albumin concentrations compared with ewes fed U. Metabolizable energy intake did not affect (P greater than .05) ewe performance or serum metabolite concentrations. Ewes fed BM + SBM in Exp. 2 gained more (P less than .05) weight than ewes fed either SBM or U, and ewes fed SBM lost less weight (P less than .05) than ewes fed U.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of supplemental protein source on passage of nitrogen to the small intestine, nutritional status of pregnant ewes, and wool follicle development of progeny.

Rambouillet wethers, surgically fitted with ruminal and duodenal cannulas, were used to determine the influence of substituting soybean meal (SBM) with blood meal (BM) in grass hay diets (8.0% CP) on N flow to the small intestine. Treatments were arranged in a 3 x 4 Latin square design and included diets (10.6% CP) supplemented with SBM; 2/3 SBM:1/3 BM; 1/3 SBM:2/3 BM; or BM. Ruminal NH3 N concentration decreased linearly (P = .03) as BM replaced SBM; however, feeding BM did not affect (P > .10) the total N, microbial N, or nonammonia N flows to the small intestine. A second experiment was conducted to determine the influence of substituting SBM with BM on ewe BW and condition score changes, blood metabolite profiles, wool growth, and progeny wool follicle development. Thirty-two pregnant Targhee ewes fed a grass hay diet were allotted randomly to four groups (n = 8) and supplemented with either SBM; 2/3 SBM:1/3 BM; 1/3 SBM:2/3 BM; or BM. Soybean meal, BM, or their combinations provided 22 g of dietary CP daily. Dietary treatments had no influence on ewe BW (P = .40) or body condition score (P = .77) changes, and ewes gained 7.6 kg of BW during the 84-d experiment. Protein source did not influence (P > .10) serum protein, urea N, creatinine, glucose, or nonesterified fatty acid concentrations. Lamb wool follicle density per square millimeter and secondary:primary follicle ratios were 22.4 and 10.8, respectively, and were not different (P > .10) among dietary treatments. Compared with SBM, no advantages were detected for BM supplementation of grass hay diets in these studies.

The influence of timing and the addition of urea to supplements containing DL-methionine on ruminal fermentation and cow weight change in beef cows.

A study was conducted to determine an optimal time for supplementation of DL-methionine in relation to time of forage intake by mature British breed-type crossbred cows, and two other experiments were conducted to determine whether ruminal ammonia concentration limited changes in disappearance rates in situ and ruminal functions caused by supplements containing DL-methionine. Experiments 1 and 2 used 4 x 4 Latin square designs with four cows in each experiment. Treatments in Exp. 1 were no supplement (CON), DL-methionine at feeding (0800), DL-methionine 4 h after feeding (1200), and DL-methionine 7 h after feeding (1500). Treatments in Exp. 2 were .5 kg of beet pulp (CON), .5 kg of beet pulp plus 16.5 g of DL-methionine (MET), .5 kg of beet pulp plus 16.5 g of DL-methionine and 55 g of urea (METU), and .4 kg of soybean (SOY). Experiment 3 was conducted in a 326-ha pasture with treatments of no supplement (CON), .5 kg of beet pulp plus 12.5 g of DL-methionine and 30 g of urea (METU), and .4 of kg soybean meal (SOY). In Exp. 1, in situ NDF disappearance rates of cows supplemented at 1200 and 1500 were greater (P less than .01) than those of cows supplemented at 0800. In Exp. 2, ruminal ammonia concentration was greatest (P less than .001) for METU (5.2 mg/dl) and least for CON (1.5 mg/dl). Disappearance rates in situ for DM differed (P less than .01) among treatments; METU was similar (P greater than .2) to SOY but faster (P less than .01) than MET. Disappearance rates of NDF were greatest (P less than .001) for METU-supplemented cows. In Exp. 3, DM and NDF disappearance rates were faster (P less than .10) for SOY than for METU. Cow BW change was positive for METU and SOY, and decrease in condition score was least (P less than .10) for METU- and SOY-treated cows. These studies indicate favorable ruminal responses to DL-methionine supplementation; however, the response depended on time of supplementation and ruminal ammonia concentration.

The effects of ruminal escape protein or fat on nutritional status of pregnant winter-grazing beef cows.

This study was designed to determine the influence of soybean meal supplementation, with or without additional ruminal escape protein or fat, on the nutritional status of pregnant winter-grazing beef cows. During two winters (Trials 1 and 2), approximately 60 prepartum beef cows grazed native foothills range each year. Cows were allotted randomly to five groups and supplemented (g/d) with either none (control); 570 soybean meal (SOY); 450 soybean meal plus 230 blood meal (SOY + BM); 140 soybean meal, 16 urea plus 450 corn gluten meal (SOY + CGM); or 570 soybean meal plus 210 animal fat (SOY + FAT). These supplements were designed to supply similar quantities of ruminal degraded protein while varying in escape protein quantity and source (SOY + BM and SOY + CGM). Condition scores and body weights were determined at trial initiation (mid-December) and conclusion (early March). Eight blood samples obtained over 4 d during three periods (9, 4 and 1 wk prior to parturition) were analyzed for concentrations of glucose, urea nitrogen (N), total bilirubin, creatinine, albumin, total protein and cholesterol. Cows in the control treatment experienced the greatest BW loss in both trials. In Trial 2, escape protein tended to decrease (P less than .06) BW loss compared to SOY, though loss tended to be greater (P less than .08) with SOY + CGM than with SOY + BM. Escape protein can enhance nutritional status when supplemented with .6 kg/d of soybean meal.

Production from first-calf beef heifers fed a maintenance or low level of prepartum nutrition and ruminally undegradable or degradable protein postpartum.

Two experiments were conducted in consecutive years to determine the effects of prepartum nutrient level and postpartum ruminally undegraded protein intake on nutrient status, milk production, subsequent calf production, and reproductive performance of 126 crossbred, primiparous beef heifers. Prepartum treatments were low nutrient intake (LN) (approximately 2.5 kg of TDN, .5 kg of CP animal-1.d-1 and maintenance nutrient intake (MN) (5 kg of TDN, 1 kg of CP animal-1.d-1), which were fed for 75 d before parturition. Two postpartum protein supplements were formulated to provide 250 g/d of ruminally degradable protein (RD) and one to supply ruminally undegraded protein (UD) at 250 g/d of additional UD CP compared to the RD supplement. Cholesterol was lower (P less than .01) in heifers given UD than in heifers given RD. Blood urea nitrogen was higher (P less than .01) for UD-fed heifers than for RD-fed heifers and was higher in LN heifers (P less than .06) than in MN heifers. Milk production did not differ (P greater than .11) as a result of LN, MN, UD, or RD. Postpartum cow weight gain was greatest (P less than .01) for UD and LN heifers. The percentage of heifers bred during the first estrous cycle of the breeding season was greater (P less than .02) for UD than for RD. Overall, prepartum nutrition did not interact with postpartum protein supplement, nor did it have any effect on postpartum interval, whereas UD increased cow weight gain postpartum and reduced postpartum interval.

Reproductive efficiency of range beef cows fed different quantities of ruminally undegradable protein before breeding.

Two studies, using 128 crossbred, multiparous beef cows grazing native winter and spring rangeland, were conducted to determine effects of protein supplementation on nutrient status and subsequent calf and reproductive performance. Postparturient cows (body condition score [BC] = 3.9) were fed 1.82 kg of one of two supplements (54% CP at 490 g of CP/d) per cow on alternate days. Supplements were formulated to contain 50% (245/490 g of CP) ruminally undegradable (UD) CP (RU50) or 25% (119/490 g of CP) UD CP (RU25) and were fed until breeding (BC = 4.2). Late-calving cows (Study 1) were individually fed supplement while grazing native range. Early-calving cows (Study 2) were group-fed supplement on alternate days while grazing native range and were daily fed approximately 5.4 kg of medium-quality grass hay (10.5% CP). Late-calving cows had similar (P > .22) BW losses postpartum, whereas early-calving cows fed RU50 lost 39 kg less (P < .01) BW than did cows fed RU25. Cows that received RU25 returned to estrus sooner (P < .02), in the late-calving study, than cows fed RU50 (47 vs 56 d, respectively). The percentage of cows serviced in the first 21 d of breeding (96 and 100% for late- and early-calving studies, respectively) and pregnancy rates (88 and 86% for late- and early-calving studies, respectively) did not differ regardless of postpartum protein supplement. When adequate CP was provided in the diet for optimum function of the rumen, addition of ruminally undegraded CP decreased weight loss of mature, postpartum beef cows grazing native range.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of barley variety and restricted versus ad libitum intake on rate, site, and extent of digestion by wethers fed a high-energy diet.

Twelve ruminally cannulated wethers (four with duodenal cannulas) were used in a replicated 4 x 4 Latin square to investigate effects of barley variety and restricted vs ad libitum intake on site, rate, and extent of digestion. Diets were based on Ottus (52.7% starch; O) or Steptoe (56.7% starch; S) barley fed at either 90% of prestudy ad libitum feed intake (R) or ad libitum consumption (A). Diets were formulated to be equal in starch content (38%). Periods consisted of 10 d for adaptation followed by 10 d in which fecal, duodenal, ruminal, and in situ collections were made. With the exception of ruminal starch digestion, barley variety did not interact with level of feed intake (P > .26). Intake of OM was 1,009, 996, 1,124, and 881 g.wether-1.d-1 for O, S, A, and R, respectively. Intake by R wethers of OM and starch was 78% (P < .01) of intake by A wethers. Duodenal flow of OM and ruminal pH were not affected (P > .28) by either intake restriction or barley variety. Although restricted intake did not affect ruminal (P = .84) and duodenal (P = .39) ammonia nitrogen, the O barley had higher (P = .01) ruminal and duodenal ammonia nitrogen than did S barley. Restricted intake had no effect (P > .30) on rate of ruminal barley digestion, ruminal and total tract starch digestion, or total tract OM digestion. This may be due to the rapid digestion rate of barley.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of ruminally undegradable protein, propionic acid, and monensin on puberty and pregnancy in beef heifers.

Two hundred ten spring-born English crossbred beef heifers were used in two experiments in consecutive years using a randomized complete block design. The objectives were to determine the effects of increasing dietary intake of ruminally undegradable protein or propionic acid on the occurrence of puberty and to elucidate the mechanism by which monensin decreases age of puberty in beef heifers. Diets were fed for 120 d beginning in mid-November and consisted of mature grass hay and barley straw with .45 kg.animal-1 x d-1 supplement (CON) formulated to obtain .4 kg.animal-1 x d-1 of BW gain; .5 kg of supplement similar to CON and containing an additional 250 g of ruminally undegradable intake protein supplied from blood and corn gluten meal (UIP); .45 kg of supplement similar to CON composition and containing 400 g.animal-1 x d-1 of a 50% water and 50% propionic acid mixture (PROP); or .45 kg of supplement similar to CON supplying 200 mg.animal-1 x d-1 of monensin (MON). The hay:straw ratio in each diet was adjusted biweekly, to maintain similar BW gains for heifers fed each dietary treatment. As planned, BW gains were similar (P > .1) for all heifers. The heifers fed MON were 21 d younger (P < .05) at first estrus than heifers fed UIP; CON and PROP were intermediate and similar to heifers fed MON and UIP. The heifers fed UIP were 7 to 8 kg heavier (P < .05) at puberty than CON- or PROP-treated heifers. The heifers fed PROP were 6 kg heavier (P < .1) at puberty than heifers fed MON. Heifers that received UIP required less (P < .05) TDN than did heifers that received CON or PROP to achieve similar gain. Pregnancy rate was similar for all treatment groups. Feeding UIP in excess of NRC CP requirements may improve energy utilization of heifers fed mature roughages but may delay the onset of puberty compared with heifers fed monensin. This study demonstrated that nutrient composition of the diet may influence age of puberty independent of growth rate.