Effects of Dietary Phosphorous and Trace Mineral Source on Immune Function,Mineral Status,and Performance of Stressed Steers

Two experiments were conducted to determine the effects of dietary P and trace mineral source on immune response, mineral status, and performance in steers stressed by weaning and disease exposure. In Experiment 1, 24 Angus and 24 Simmental weaned steers were used. Treatments consisted of 1) inorganic trace minerals, 2) organic trace minerals, 3) 0.15% supplemental P + inorganic trace minerals, and 4) 0.15% supplemental P + organic trace minerals. Copper, Mn, and Zn were added to provide 10, 25, and 25 mg/kg DM, respectively. The organic treatments supplied 50% of the supplemental Cu and Mn, and 66% of the supplemental Zn from metal proteinates, with the remainder supplied by inorganic sulfate forms. Inorganic treatments supplied all of the supplemental Zn, Cu, and Mn from sulfate forms. The basal diet was a corn silage-soybean meal-based diet. On d 2 following weaning, steers received an intranasal inoculation of infectious bovine rhinotracheitis virus (IBRV). Rectal temperatures in response to IBRV inoculation were similar across treatments. On d 9, steers were injected with 10 ml of a 25% pig red blood cell (PRBC) suspension. Total Ig titers against PRBC concentrations were higher (P<0.05) in steers receiving no supplemental P on d 7 postinjection. However, IgG and IgM titers were unaffected by treatment. Cell-mediated immune response (CMI) to phytohemagglutinin (PHA), plasma Cu and Zn concentrations, and 38-d performance were unaffected by treatment. In Experiment 2, 35 Angus steers were fed diets containing either inorganic or organic trace minerals. Performance and percent morbidity were unaffected by treatment. Plasma Cu was higher for steers fed organic trace minerals. Results indicate that increasing dietary P or replacing inorganic trace minerals with organic forms had little effect on immunity or performance of steers stressed by weaning.     

Inheritance and interaction of immune traits in beef calves

Three sets of blood samples were obtained from beef calves of two experimental populations and assayed for various immunological measurements. The first set of samples was taken between 24 and 48 h after birth and quantified for IgG1 concentration. A second set was taken immediately prior to vaccination for infectious bovine rhinotracheitis virus (IBRV; at an average age of 164 d) and a third set taken 60 d post-vaccination. These later samples were quantified for antibodies specific to IBRV. Level of complement C3 was also quantified in the samples taken immediately prior to vaccination. Three hundred sixty-seven calves were from four Hereford lines; three lines were previously selected for growth traits and the fourth was a randomly selected control line. There were no consistent differences in immune traits among these lines. The second group of 165 animals were Angus, Hereford and Red Poll calves. While Angus calves had a higher mean IgG1 concentration at 24 to 48 h of age than Hereford or Red Poll calves, no differences among breeds were found for the other immune traits measured. Calves from older dams (greater than 3 yr old) tended to have higher mean IgG1 concentrations, pre-vaccination IBRV antibody titers and complement C3 levels than calves from 2- and 3-yr-old cows. However, these calves had lower 60-d post-vaccination IBRV titers than calves from the younger cows (P less than .05). As pre-vaccination IBRV antibody titer increased, post-vaccination IBRV antibody titer decreased (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Estimated copper requirements of angus and simmental heifers

In Exp. 1, Simmental (n = 21) and Angus (n = 21) heifers, approximately 9 mo of age, were used in a 160-d study to determine the effect of dietary Cu on growth and Cu status. Two- or three-yr-old first-calf heifers (21 Angus and 21 Simmental) entering into their last trimester of pregnancy were used in Exp. 2 to estimate Cu requirements of the two breeds during gestation and early lactation. Treatments in both studies consisted of 0 (control), 7, or 14 mg of supplemental Cu (as CuSO4)/kg of DM. The control corn silage-based diets contained 6.4 and 4.4 mg of Cu/kg of DM in Exp. 1 and 2, respectively, and 1.2 mg of Mo/kg. Dietary Cu did not affect performance in either breed in Exp. 1. Copper supplementation generally did not affect plasma Cu concentrations in Angus heifers, but increased (P < 0.05) plasma Cu in Simmental heifers from d 37 until the end of Exp. 1. Final liver Cu concentrations were lower (P < 0.05) than initial concentrations in control Angus and Simmental heifers; however, liver Cu increased (P < 0.01) in Cu-supplemented heifers. In Exp. 2, Cu supplementation of the control diet increased (P < 0.05) plasma Cu during gestation and greatly increased (P < 0.01) liver Cu in both breeds. Calves born to cows not supplemented with Cu also had lower plasma Cu concentrations than Cu-supplemented calves by 73 d of age. In both studies, control Simmental heifers had lower (P < 0.05) plasma Cu concentrations than Angus on most sampling dates. When Cu was supplemented at 7 or 14 mg/kg of DM,few differences in plasma Cu concentrations were observed between breeds. Results suggest that Angus heifers have a lower minimal Cu requirement than Simmental. Based on liver Cu, the control diets containing 4.4 or 6.4 mg of Cu/kg of DM did not meet the Cu requirement of either breed during gestation and lactation or growth. Addition of 7 mg of Cu/kg of DM to the control diets met Cu requirements of both breeds.     

The effects of low-copper diets with or without supplemental molybdenum on specific immune responses of stressed cattle

Angus bull calves (n = 42; 7 mo of age; 254 kg initial BW) were used to investigate the effects of dietary Cu and Mo on immune function of stressed cattle. Randomly selected calves (n = 22) were injected with 90 mg of Cu as Cu glycinate 28 d before weaning and castrated at weaning. These calves received 7.5 and 5 mg of supplemental Cu/kg of DM during a 41-d receiving phase and a 196-d growing phase, respectively. The remainder of the steers received no supplemental Cu during the experiment. Copper-supplemented steers had adequate Cu status at weaning, whereas unsupplemented calves were marginally Cu-deficient. Cell-mediated response to intradermal injection of phytohemagglutinin was not affected by dietary treatment during the receiving phase. During the growing phase, half of the steers in each Cu treatment were given 5 mg of supplemental Mo/kg of DM. Copper supplementation increased (P<.05) humoral response to ovalbumin injected on d 133 of the growing phase. On d 168 of the growing phase, calves receiving only supplemental Mo were severely Cu-deficient based on plasma and liver Cu concentrations. The other treatment groups had adequate Cu status. Before feeding on d 168 of the growing phase, half of the steers were loaded onto trailers and transported 2.5 h, and they remained on the trailers an additional 9.5 h. Humoral response to porcine erythrocytes (PRBC) and delayed-type hypersensitivity (DTH) to dinitrochlorobenzene was tested at the end of the stress period. There was a Cu x stress interaction for humoral response to PRBC, with Cu decreasing antibody titers in unstressed calves and increasing titers in stressed steers. Stressed steers had lower (P = .03) ADG during the 28 d following stress. The results of this study indicate that Cu deficiency and 5 mg of supplemental Mo/kg of DM do not dramatically alter the specific immunity of stressed cattle.     

Periodic changes in body composition and in priorities for tissue storage and retrieval in mature beef cows.

Sixty mature (4 to 6 yr), nonpregnant, nonlactating beef cows of two breed types, Angus (n = 30) and Simmental (n = 30), were used in a four-period, split-plot study (371 d) to determine the seasonal differences in body composition. Periods were chosen to represent each of the four seasons in one year that ran consecutively from June 14, 1986 to June 20, 1987. Initially, all cows were assigned randomly within breed type to one of four feeding levels based on the cows' estimated maintenance requirement (75, 87.5, 112.5, and 125% of weight maintenance) and were rotated such that all animals were fed at all four feeding levels during the course of the study. Body composition was estimated via isotope dilution initially and at the end of Periods 1 through 3 and via derived regression relationships after Period 4. Body composition differed by breed; Simmental cows had greater (P less than .05) amounts of empty body protein (79.4 vs 55.8 kg, respectively) and less (P less than .05) empty body fat (85.3 vs 93.9 kg, respectively) than the Angus cows. These differences also were apparent when expressed as a percentage of live weight. Season altered components of the empty body. On the average, both breeds mobilized (P less than .05) empty body protein (-3.6 and -5.4 kg for Angus and Simmental cows, respectively) in the summer while simultaneously gaining (P less than .05) empty body fat (15.3 and 30.1 kg for Angus and Simmental cows, respectively). Both breeds subsequently tended to gain empty body protein in the winter and spring.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of Charolais and Limousin as terminal cross sire breeds

Birth, weaning, feedlot and carcass traits were evaluated on 1,181 calves sired by Charolais and Limousin bulls out of eight crossbred dam groups (Hereford X Angus, Angus X Hereford, Simmental X Angus, Simmental X Hereford, Brown Swiss X Angus, Brown Swiss X Hereford, Jersey X Angus, Jersey X Hereford). Calves were born in the spring over a 4-yr period during which dams ranged from 3 to 8 yr of age. Charolais-cross calves were 2.7 kg heavier (P less than .01) at birth and had a 9.9% higher (P less than .01) incidence of difficult calvings and 4.6% greater (P less than .05) preweaning death loss than did Limousin crosses. Charolais-sired calves out-gained Limousin-sired calves by 31 g/d (P less than .01) from birth to weaning and were 9 kg heavier (P less than .01) at weaning. After weaning, calves were self-fed a finishing diet and slaughtered as each animal attained an estimated carcass grade of low Choice. Charolais-cross calves gained 60 g/d faster (P less than .01) than Limousin crosses, were fed 6.8 fewer d and were 17.3 kg heavier (P less than .01) at slaughter. Feed efficiency was similar for both sire breeds. On a grade-equivalent basis, Charolais crosses produced 7 kg heavier (P less than .01) carcass and had 22 g more carcass weight per day of age (P less than .01). Charolais crosses had slightly less internal and external fat. Dressing percentage was higher for Limousin cross calves (64.6 vs 63.9%, P less than .01). Longissimus muscle area and carcass cutability were similar for crosses of both sire breeds.     

Influence of yeast culture on feeder calves and lambs.

Four experiments were conducted to determine the influence of yeast culture on 1) the health and performance of feeder calves, 2) the response of calves to an infectious bovine rhinotracheitis virus (IBRV) infection, and 3) nutrient utilization in lambs fasted for 3 d. In Exp. 1, 108 feeder calves were transported from Tennessee to Texas (1,600 km) and fed receiving diets containing 0 or .75% yeast culture and .35 or .69% P in a 2 x 2 factorial arrangement of treatments. In Exp. 2, 101 calves were transported 950 kg from Austin, TX to Bushland, TX and fed receiving diets containing 0, .75, 1.125, or 1.5% yeast culture. Yeast culture did not significantly affect the health or performance of calves in either experiment, although morbid calves fed yeast culture required fewer (P less than .05) days of antibiotic therapy in Exp. 2. In Exp. 3, feeder steers were fed diets containing 0 or .75% yeast culture and challenged intranasally with IBRV. Calves fed yeast culture tended to maintain heavier weights and higher DMI during IBRV infection than did steers fed the control diet. In Exp. 4, feeder lambs were fasted for 3 d and refed diets containing 0, .75, 1.125, or 1.5% yeast culture during a N and mineral balance trial. Lambs fed yeast culture had greater (P less than .08) N balance and tended to have greater Zn and Fe balance than control lambs. Results of these studies are interpreted to suggest that supplementation of morbid calves with yeast culture can have beneficial effects (fewer sick days, higher feed intakes) and that these effects may be mediated by improved N, Zn, and Fe metabolism.     

Effect of calving period on herbage intake and nutrient turnover of Simmental and Angus suckler cows with Angus sired calves grazing subalpine and alpine pastures

Herbage intake and utilisation were measured in 12 Simmental and 12 Angus suckler cows with Angus sired calves grazing one subalpine (1000 m o.d. (ordinance datium)) and two alpine pastures (first and secondary growth; 2000 m). Calving periods were late autumn and late winter for both breeds. Herbage dry matter intake of cows and calves, determined with slow-release alkane capsules, increased from subalpine to alpine pastures from 11.9 to 15.8 and 1.1 to 3.5 kg/day, respectively. Nitrogen (N) intake was highest on regrowth pasture. Simmental cows consumed more herbage than Angus cows, even when corrected for metabolic body weight. Their calves did not differ in herbage consumption although crossbred calves had significantly higher daily gains (+16%) than Angus calves. Dam breed effects on N and phosphorous (P) excretion and N utilisation were small when corrected for differences in intake (higher in the Simmental groups). Compared to winter-calving, autumn-calving resulted in cows gaining weight but also resulted in lower daily gains of the calves despite higher herbage intake. This increased N and P losses per unit of weight gain even when calculated for cows and calves together. Accordingly, late-winter calving is advantageous for this type of alpine grazing system.     

Genetic and environmental factors associated with incidence of infectious bovine keratoconjunctivitis in preweaned beef calves

Infectious bovine keratoconjunctivitis (IBK) is one of the most economically important diseases in preweaned calves. This study examined the health records of 45,497 calves over a 20-yr period to determine environmental and genetic factors influencing the incidence of IBK. Three data sets were analyzed with an animal model. The first data set (n = 41,986) evaluated environmental factors and genetic differences among nine purebred (Angus, Braunvieh, Charolais, Gelbvieh, Hereford, Limousin, Pinzgauer, Red Poll, and Simmental) and three composite breeds (MARC I, MARC II, and MARC III). Weaning weights of calves diagnosed with IBK were 8.9 kg lighter (P < 0.05) than weights of healthy calves. Incidence of IBK was related to age of the calf and the seasonal life cycle of the face fly (Musca autumnalis). Incidence of IBK increased in the spring (June), peaked during the summer months (July to September), and then decreased in the fall. Herefords were the most susceptible breed (P < 0.05) compared with all other purebreds and composites. Estimates of direct heritability for the incidence of IBK were generally low and ranged from 0.00 to 0.28 by breed. The maternal permanent environmental and genetic effects of the dam on the incidence of IBK were not significant for most breeds. The second data set (n = 9,606) was used to estimate heterosis for the incidence of IBK from a Hereford and Angus diallel design. The heterosis effect for the incidence of IBK in reciprocal Hereford/Angus crossbred calves was slightly negative (P = 0.12) but not large. The higher incidence of IBK in Angus x Hereford calves compared with Hereford x Angus calves (13.3 vs. 8.9%) suggests a maternal effect related to the incidence of IBK. Incidence of IBK in crossbred calves sired by tropically adapted breeds (Brahma, Boran, Tuli) compared with purebred and crossbred Bos taurus types was investigated in the third data set (n = 2,622). Crossbred calves sired by tropically adapted breeds had a lower incidence of IBK than most Bos taurus types (P < 0.05), but they were not different than either reciprocal crosses of Hereford and Angus or purebred Angus calves. Response to selection for decreasing the incidence of IBK is likely to be slow because of low heritability and low incidence in most breeds. Significant breed differences for incidence of IBK may be important to some producers and management systems.     

Metabolism and morphology of brown adipose tissue from Brahman and Angus newborn calves

The objective of this study was to compare adipocyte morphology and lipogenesis between breed types (Angus vs Brahman) in brown adipose tissue (BAT) and white adipose tissue (WAT) from newborn calves. The Brahman calves (n = 7) were born during the fall season, whereas the Angus calves were born in fall (n = 6) or the following spring (n = 4). At parturition, Brahman cows were lighter than fall Angus cows, but were heavier than spring Angus cows (P < .05). Birth weights and perirenal BAT weights were greater in spring-born, but not in fall-born Angus calves, than in Brahman calves (P < .05). Fall-born Angus BAT contained 63% more (P < .05) adipocytes/100 mg tissue and contained a greater proportion (P < .05) of adipocytes with mean diameters of 40 to 50 microm, and fewer adipocytes with diameters of 60 microm or greater, than Brahman BAT. Brahman BAT contained two-to-three times as many beta-receptors as Angus BAT (P < .05), although the dissociation constant (Kd) was not different between breed types. Mitochondria in Brahman BAT were primarily spherical, whereas Angus BAT mitochondria were elongated, and mitochondrial cross-sectional area tended (P = .08) to be greater in Brahman BAT than in Angus BAT. The mitochondrial uncoupling protein (UCP) mRNA concentration (per 10(6) cells) was greater in Brahman BAT than in BAT from fall-born Angus calves. Lipogenesis from acetate was greater in Angus BAT than in Brahman BAT (P < .05), and glucose and palmitate contributed a greater proportion of carbon to lipogenesis in Brahman BAT than in Angus BAT. These differences in lipogenesis between breed types were not observed in s.c. WAT. The WAT from both breed types contained adipocytes with distinct brown adipocyte morphology, suggesting an involution of BAT to WAT in utero. We conclude that differences in UCP gene expression cannot cause the greater peak thermogenesis of Angus calves; however, differences between breed types in lipid metabolism and(or) mitochondrial morphology may contribute to this phenomenon.     

Factors influencing intermuscular fat and other measures of beef chuck composition.

Carcasses from 59 steers produced from the mating of Braford, Simbrah, Senepol, and Simmental bulls to Brahman- and Romana Red-sired cows and Brahman bulls mated to Angus cows were used in this study. Effects of sire breed and feeding calves vs yearlings on fat depots in the chuck, when steers were fed to 1.0 cm external fat, were determined. Breed of sire and feeding calves vs yearlings had no effect (P greater than .05) on percentage of intermuscular fat. However, carcasses from Braford-sired steers had a higher (P less than .05) percentage of dissectable subcutaneous fat on the chuck than did those from other breed groups. Carcasses from Simmental-sired steers were superior (P less than .05) to those from Braford-sired steers in USDA yield grade and had a higher average marbling score (P less than .05) than the Simbrah-sired group. Estimated kidney, pelvic, and heart (KPH) fat was higher (P less than .05) in carcasses from Brahman-, Simbrah-, and Senepol-sired steers than in Braford-sired steers. Steers fed as calves had higher percentages (P less than .05) of KPH fat and major chuck muscles than did those fed as yearlings. The best single predictor of percentage of intermuscular fat within the chuck was adjusted fat over the ribeye (R2 = .46).     

Evaluation of crossbred Brahman and continental European beef cattle in a subtropical environment for birth and weaning traits

A total of 528 birth and 475 weaning records collected over a 3-yr period were analyzed to evaluate the productivity of several beef cattle breed crosses. The calves were produced by artificial insemination using 17 Brahman, 15 Chianina, 15 Maine Anjou and 16 Simmental sires bred to Angus and Hereford dams varying in age from 3 to 11 yr. Breed-of-sire effects were important (P less than .05 to P less than .001) for gestation length, birth weight, conformation score and condition score, but were not observed for birth weight adjusted for gestation length, percentage calving assistance, survival rate or weaning weight. Brahman crosses had the longest gestation lengths, being 4.7 d longer than Simmental crosses, which were the shortest in length. Chianina crosses were the heaviest at birth and experienced the most calving difficulty. Simmental crosses had the highest survival rate. Although breed-of-sire differences were observed in conformation score, the difference was less than one-third of a grade between the highest-scoring Simmental crosses and the lowest-scoring Brahman and Chianina crosses. Brahman crosses had the highest condition scores, being approximately one-third of a grade higher than the lowest-ranking Chianina crosses. Differences among the sire breeds for weaning weight were surprisingly small, varying only 3 kg from the heaviest to lightest breed-of-sire groups. Angus dams had shorter gestation lengths (P less than .001) and produced calves that weighed more at weaning (P less than .001) and scored higher for conformation (P less than .001) and condition (P less than .001) score than Hereford dams.(ABSTRACT TRUNCATED AT 250 WORDS)     

Brown adipose tissue development and metabolism in ruminants

We conducted several experiments to better understand the relationship between brown adipose tissue (BAT) metabolism and thermogenesis. In Exp. 1, we examined perirenal (brown) and sternum s.c. adipose tissue in 14 Wagyu x Angus neonates infused with norepinephrine (NE). Perirenal adipocytes contained numerous large mitochondria with well-differentiated cristae; sternum s.c. adipocytes contained a few, small mitochondria, with poorly developed cristae. Lipogenesis from acetate was high in BAT but barely detectable in sternum s.c. adipose tissue. In Exp. 2, we compared perirenal and tailhead adipose tissues between NE-infused Angus (n = 6) and Brahman (n = 7) newborn calves. Brahman BAT contained two-to-three times as many total beta-receptors as Angus BAT. The mitochondrial UCP1:28S rRNA ratio was greater in Brahman BAT than in BAT from Angus calves. Lipogenesis from acetate and glucose again was high, but lipogenesis from palmitate was barely detectable. Tail-head s.c. adipose tissue from both breed types contained adipocytes with distinct brown adipocyte morphology. In Exp. 3, three fetuses of each breed type were taken at 96, 48, 24, 14, and 6 d before expected parturition, and at parturition. Lipogenesis from acetate and glucose in vitro decreased 97% during the last 96 d of gestation in both breed types, whereas the UCP1 gene expression tripled during gestation in both breed types. At birth, palmitate esterification was twice as high in Angus than in Brahman BAT and was at least 100-fold higher than in BAT from NE-infused calves from Exp. 2. Uncoupling protein-1 mRNA was readily detectable in tailhead s.c. adipose tissue in all fetal samples. In Exp. 4, male Brahman and Angus calves (n = 5 to 7 per group) were assigned to 1) newborn treatment (15 h of age), 2) 48 h of warm exposure (22 degrees C) starting at 15 h of age, or 3) 48 h of cold exposure (4 degrees C) starting at 15 h of age. Brahman BAT adipocytes shrank with cold exposure, whereas Angus BAT adipocytes did not. Similarly, BAT from neonatal lambs (Exp. 5; n = 6 per group) was depleted of lipid in response to cold exposure, although UCP1 gene expression persisted. In Exp. 4, NE stimulated lipogenesis from palmitate in BAT incubated in vitro. Lipogenesis from palmitate was higher in Angus than in Brahman BAT, and increased with both warm and cold exposure. These studies suggest that BAT from Brahman calves may be exhausted of lipid shortly after birth during times of cold exposure.     

Effects of gastrointestinal parasites on parasite burden, rectal temperature, and antibody titer responses to vaccination and infectious bovine rhinotracheitis virus challenge

Thirty-three colostrum-deprived Holstein bull calves (initial BW of 131 ± 4 kg) were used to determine the effect of timing of anthelmintic administration relative to vaccination on antibody titer response to vaccine component antigens. When calves were at least 3 mo of age, they were sorted randomly into individual pens and assigned to 1 of 3 treatment groups, treatments consisted of 1) dewormed 2 wk before vaccination (DPV), 2) dewormed at the time of vaccination (DV), or 3) control, vaccinated but not dewormed (CONT). All calves were inoculated with infective larvae of brown stomach worms (Ostertagia ostertagi) and intestinal worms (Cooperia spp.) on d 1, 7, 10, 14, and 18 for a total dose of 235,710 infective larvae per calf. Calves (DPV and DV) were dewormed on d 21 or 35 with a 10% fenbendazole suspension at 5 mg/kg of BW. On d 35, all calves were vaccinated with a modified-live virus respiratory vaccine containing IBRV (infectious bovine rhinotracheitis virus), BVDV-1 (bovine viral diarrhea virus genotype 1), BVDV-2 (BVDV genotype 2), PI-3 (parainfluenza-3), and BRSV (bovine respiratory syncytial virus). During the 103-d experiment, weekly fecal egg counts, blood, and rectal temperatures were collected and health status was recorded daily. Blood samples were obtained weekly to determine serum neutralizing (SN) antibody titers to IBRV, BVDV-1, BVDV-2, and PI-3 and cytokine levels for IL-4, IL-6, TNF-α (tumor necrosis factor-α), and IFN-γ (interferon-gamma). There was a tendency (P < 0.09) for CONT calves to have greater IL-4 concentrations. By design, control calves had greater (P < 0.01) fecal egg counts during the experiment. All calves developed antibody titers to IBRV, BVDV-1, BVDV-2, and PI-3 by d 15 postvaccination. On d 88, all calves were challenged with IBRV and blood samples were obtained on d 88, 89, 90, 93, 95, 98, 99, and 103. All calves had increased rectal temperatures during the final 7 d of the IBRV challenge. However, the CONT group had greater (P < 0.01) rectal temperatures on each sampling day except d 90 compared with the DPV and DV treatments. Therefore, deworming before or at vaccination reduced parasite burden and decreased rectal temperature increase after an IBRV challenge. Deworming strategy had no effect on antibody response to vaccination or IBRV challenge.     

Maternal breed of sire effects on postweaning performance of heifer and steer progeny: postweaning growth and carcass characteristics.

Heifer and steer progeny of 2-yr-old first-cross (F1) heifers and 3- to 6-yr-old F1 cows, from Hereford dams and five sire breeds, were evaluated for postweaning feedlot growth and carcass composition. Breeds of sire of dam were Angus (A), Red Poll (RP), Tarentaise (T), Simmental (Sm), and Pinzgauer (P). Calves from 2-yr-old heifers were sired by Shorthorn, and calves from 3- to 6-yr-old dams were sired by Charolais. Breed of sire of dam was significant (P less than .05 to P less than .01) for total gain and final weight for female progeny from 2-yr-old dams. At all weights, Sm, P, and T ranked above A and RP. Progeny of A, P, Sm, and T F1 2-yr-old dams were not significantly different but were higher (P less than .05) than RP heifers in total feedlot gain. Breed of sire of dam was significant (P less than .05) for carcass weight and longissimus muscle area; T ranked highest and RP lowest. Breed was not significant for any growth traits of steer progeny of 2-yr-old dams. Breed was significant for marbling score; A ranked highest and exceeded (P less than .01) both RP and Sm steers. Breed was significant (P less than .05) for most growth traits in the heifer progeny of the 3- to 6-yr-old dams bred to Charolais sires. Heifer calves of the Sm group were heavier (P less than .05) than all other groups for most weights and total gain. For total gain, P and T were intermediate and A and RP lowest. For heifer carcass traits from 3- to 6-yr-old dams, breed was significant (P less than .05 to P less than .01) for carcass weight, longissimus muscle area, percentage of cutability, and estimated kidney, heart, and pelvic fat. Heifers from Sm-sired dams were heavier (P less than .05) than those from all other groups but ranked second to heifers from P for percentage of cutability. Marbling scores of RP heifer carcasses ranked highest of all groups. Breed was not significant (P greater than .05) for any of the weights or gains in steer progeny of 3- to 6-yr-old dams; however, the Sm and P groups ranked above A and RP for all feedlot test weights.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in metabolites, metabolic hormones, and luteinizing hormone before puberty in Angus, Braford, Charolais, and Simmental heifers

We determined changes in insulin, glucose, free fatty acids (FFA), growth hormone (GH), insulin-like growth factor I (IGF-I) and LH before puberty in Angus, Braford, Charolais, and Simmental heifers. Our primary objective was to identify metabolites and metabolic hormones that serve as metabolic cues for onset of puberty. Angus (n = 12). Braford (n = 7), Charolais (n = 9), and Simmental (n = 7) heifers were assigned at weaning (289 +/- 25 d of age; 264 +/- 23 kg) to open-sided pens with slotted floors, and they were fed a corn silage-concentrate diet formulated to provide gains of .91 kg/d. Puberty was defined as the 1st d (d 0) that serum progesterone (determined in blood samples collected at weekly intervals) exceeded 1 ng/ml. Blood samples were collected before and after feeding at 15-min intervals for 8 h at 21-d intervals before puberty in a subsample of heifers (at least five per breed). Angus and Simmental heifers weighed less and were younger (P less than .05) at puberty than Charolais and Braford heifers. Serum FFA before feeding and frequency of LH release increased (P less than .05) from d-40 +/- 3 to d-17 +/- 3 in all breeds. Conversely, concentrations of insulin were greater (P less than .05) at -40 than at -17 d from puberty in Angus, but not in Braford, Charolais, or Simmental heifers. Frequency of GH release was greater at d -40 than at d -17 in Angus heifers; however, in Braford and Charolais heifers frequency of GH release was greater at d -17 than at d -40. Concentrations of IGF-I (measured every 2 wk) increased linearly (P less than .07) from d -56 to 0 from puberty in Angus but not in other breeds. In conclusion, frequency of LH release and concentrations of FFA increased before puberty in all breeds; however, consistent changes in other metabolites and hormones were observed only in Angus heifers.     

Effect of calf age and dam breed on intake,energy expenditure,and excretion of nitrogen,phosphorus, and methane of beef cows with calves

The effects of calf age and dam breeds of different milk yield potential on turnover of energy and nutrients were followed in 16 Simmental and 16 Angus beef cows with Angus-sired calves. Calf ages investigated were 1, 4, 7, and 10 mo. The forage offered for ad libitum access consisted of hay for the calves and of a constant mixture of grass silage, meadow hay, and straw (1:0.7:0.3 on a DM basis) for the cows. Calves of 10 mo of age received an additional 2.6 kg DM/d of crushed barley. The animals were kept in groups of four cows and four calves except in the respiration chambers, where only one cow (tethered) and her calf (loose) were grouped together. Indicator techniques were applied to obtain individual data on feces and urine volumes during group housing. In the Simmental cows, heavier on average by 22 kg, voluntary DMI was higher than in the Angus cows (14.0 vs 12.3 kg/d). In calves, DMI from supplementary feeds was 1.6, 3.9, and 6.3 kg/d, on average, at 4, 7, and 10 mo of age, respectively. Dam breed had no significant effect on DMI and ADG of calves and on BW changes of cows. System retention of energy, N, and P showed a curvilinear development with calf age. System energy expenditure, which linearly increased with calf age, was higher with Simmental than with Angus dams (11%), even when adjusted for metabolic BW (8%). Energy loss through methane linearly increased with NDF intake and, consequently, with calf age from 18 to 30 MJ/d (446 to 751 L/d) for cows and calves together. Similarly, fecal and urinary N excretion and fecal P excretion steadily increased with calf age. In calves, the easily volatile N percentage of manure N rapidly decreased from very high levels in young calves. The resulting changes in inclination to gaseous N loss during manure storage for 8 wk were more than compensated by alterations in N intake of the calves, resulting in an increased total system N loss with progressing lactation. Overall, the present results indicate a difference between Angus and Simmental in efficiency of nutrient and energy utilization that might be explained by the difference in amount of delivery of nutrients to the calves via milk vs forage. Suggestions are made as to how the emissions of N, P, and methane, which were excessive in relation to productivity, could be reduced by nutritional means.     

Proportion of corn silage in diets of feedlot steers fed to achieve stepwise increases in growth.

Two experiments were conducted to investigate the effects of proportion of dietary corn silage during periods of feed restriction on performance of steers. In Exp. 1, Simmental x Angus steer calves (n = 107; initial BW = 273 +/- 3.8 kg) were allotted to 12 pens with eight or nine steers/pen and four pens/treatment. Periods of growth were 273 to 366 kg BW (Period 1), 367 to 501 kg BW (Period 2), and 502 to 564 kg BW (Period 3). In two of the dietary regimens, steers were given ad libitum access to feed throughout the experiment and were fed either a 15% corn silage diet in each period or an 85, 50, and 15% corn silage diet in Periods 1, 2, and 3; respectively. In the third feeding regimen, a programmed intake feeding regimen was used. Steers were fed a 15% corn silage diet in each period. However, feed intake was restricted to achieve a predicted gain of 1.13 kg/d in Period 1 and 1.36 kg/d in Period 2, and feed was offered for ad libitum consumption in Period 3. For the entire experiment, ADG was similar (P = 0.41) among treatments and feed efficiency was lower (P < 0.10) for steers in the corn silage regimen than for steers in the programmed intake and ad libitum regimens. In Exp. 2, Simmental x Angus steer calves (n = 106; initial BW = 233 +/- 2 kg) were allotted by BW to 12 pens (three pens/treatment) and fed in three periods similar to those described in Exp. 1. Four feeding regimens were investigated: 1) AL; steers were offered a 15% corn silage diet for ad libitum consumption in all three periods; 2) PI; DMI was programmed to achieve gains as described in Exp. 1; 3) CS-HLL; programmed intake as described above except diets contained 85, 15, and 15% corn silage in Periods 1, 2, and 3, respectively; and 4) CS-HIL; same feeding regimens as CS-HLL, except diets contained 85, 50, and 15% corn silage in Periods 1, 2, and 3, respectively. Steers were given ad libitum access to feed in Period 3. Overall ADG was lower (P < 0.05) for steers in the CS-HLL and CS-HIL feeding regimens than for steers in the AL and PI regimens; feed efficiency was greatest for steers in the PI regimen. Few effects of feeding regimen on carcass characteristics were observed.     

Physiological responses of cattle consuming tall fescue to environmental temperature and supplemental phenothiazine

The influence of supplemental phenothiazine (P) on growth and physiological criteria was studied in parasite-controlled calves consuming endophyte (Acremonium coenophialum)-infected tall fescue (TF). In Exp. 1, nine Angus heifer calves (312 kg) were supplemented with 227 g corn-mineral (CM) mix twice daily and allowed ad libitum access to either high-endophyte (HE) G1-307 (greater than 90% infected) or low-endophyte (LE) Kenhy (less than 1% infected) tall fescue hay, or HE G1-307 plus 2 g/d P in the daily supplement. Calves were kept in temperature-controlled rooms for 12 d at 21 degrees C followed by 7 d at 34 degrees C. In Exp. 2, 48 Angus steer calves (312 kg) were assigned to treatment groups consisting of calves grazing HE Kentucky-31 (57% infected) or LE Johnstone (less than 1% infected) TF, and supplemented daily with either .91 kg of a control CM mix or .91 kg of the CM mix containing 2 g P. The 112-d experiment was initiated on May 4 with BW and rectal temperature (RT) measurements and blood collected at 28-d intervals. In both experiments, calves receiving HE TF had lower (P less than .01) serum prolactin concentrations (PRL) at elevated ambient temperature and lower (P less than .01) serum alkaline phosphatase activities (AP) but higher (P less than .01) RT than calves consuming LE TF regardless of ambient temperature.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genetic x environment interactions on blood constituents of Angus, Brahman, and reciprocal-cross cows and calves grazing common bermudagrass or endophyte-infected tall fescue

Over a 2-yr period, effects of genotype and forage on blood metabolites, enzymes, and minerals were determined in Angus, Brahman, Angus x Brahman (sire x dam), and Brahman x Angus cows, and 129 calves from these cows sired by Hereford bulls. Cows and calves continuously grazed either common bermudagrass or endophyte-infected 'Kentucky-31' tall fescue pastures throughout the year. Blood samples were collected via jugular venipuncture in April, August, October (weaning), and November (after 30 d in a feedlot) of each year. Plasma urea N concentrations of cows and calves were affected by forage (P < 0.01) and breed (P < 0.05). Plasma cholesterol and FFA concentrations of cows were affected by forage (P < 0.01) and breed (P < 0.05). In calves, antibody titers to infectious bovine rhinotracheitis virus were not affected by forage but were affected by breed. Serum inorganic P concentrations of calves and cows were affected by forage (P < 0.05). Serum P concentrations and alkaline phosphatase activity of calves were affected by breed (P < 0.05). Calves grazing bermudagrass had higher (P < 0.05) serum concentrations of Fe and total iron binding capacity (TIBC). There was evidence of maternal heterosis for concentrations of free fatty acids, cholesterol, aspartate aminotransferase, Ca, Mg, alkaline phosphatase, ceruloplasmin, Fe, and TIBC. There was evidence of grandmaternal effects for plasma concentrations of urea N, cholesterol, Ca, P, Mg, and alkaline phosphatase. These results suggest that calves and cows grazing tall fescue are generally on a lower plane of nutrition than those grazing bermudagrass and that Brahman x Angus and Angus x Brahman crossbred cows and their calves seen to be more tolerant of the negative effects of tall fescue than the average of their purebred contemporaries.