Performance by spring and fall-calving cows grazing with full, limited, or no access to toxic Neotyphodium coenophialum-infected tall fescue.

Replacing toxic, wild-type Neotyphodium coenophialum-infected tall fescue (E+) with nontoxic, N. coenophialum-infected tall fescue (NE+) has improved cow performance, but producer acceptance of NE+ has been slow. The objective was to compare performance by spring- and fall-calving cows grazing either E+ or NE+ at different percentages of the total pasture area. Gelbvieh×Angus crossbred cows (n=178) were stratified by BW and age within calving season and allocated randomly to 1 of 14 groups representing 5 treatments for a 3-yr study: i) Fall-calving on 100% E+ (F100); ii) Spring-calving on 100% E+ (S100); iii) Fall-calving on 75% E+ and 25% NE+ (F75); iv) Spring-calving on 75% E+ and 25% NE+ (S75); and v) Spring-calving on 100% NE+ (SNE100). Groups allocated to F75 and S75 grazed E+ until approximately 28 d before breeding and weaning, then were then moved to their respective NE+ pasture area for 4 to 6 wk; those allocated to F100, S100, and SNE100 grazed their pastures throughout the entire year. Samples of tall fescue were gathered from specific cells within each pasture at the time cows were moved into that particular cell (∼1 sample/mo). Blood samples were collected from the cows at the start and end of the breeding season. Stocking rate for each treatment was 1 cow/ha. Forage IVDMD, CP, and total ergot alkaloid concentrations were affected (P<0.05) by the treatment×sampling date interaction. Hay offered, cow BW, and BCS at breeding, end of breeding, and at weaning were greater (P<0.05) from fall-calving vs. spring-calving. Cow BW at weaning was greater (P<0.05) from F75 and S75 vs. F100 and S100. The calving season×NE+ % interaction affected (P<0.05) calving rates. Preweaning calf BW gain, actual and adjusted weaning BW, ADG, sale price, and calf value at weaning were greater (P<0.05) from fall-calving vs. spring-calving and from SNE100 vs. S75 except for sale price which was greater (P<0.05) from S75 vs. SNE100. Cow concentrations of serum prolactin at breeding and serum NEFA at the end of breeding were affected (P<0.05) by the calving season×NE+ % interaction. Serum Zn and Cu concentrations from cows were affected (P<0.05) by calving season. A fall-calving season may be more desirable for cows grazing E+, resulting in greater calving rates, cow performance, and calf BW at weaning, whereas limited access to NE+ may increase calving rates, serum prolactin, and NEFA concentrations during certain times in the production cycle, particularly in spring-calving cows.

Testis development and gonadotropin secretion in broiler breeder males.

One-day-old chicks were used to evaluate testis development and concentrations of luteinizing hormone, follicle-stimulating hormone (FSH), and testosterone during ontogenesis. Males on a conventional breeder program (control) were reared on a 15L:9D photoperiod and ad libitum food and water intake for 2 wk. On the third week, males were placed on a restricted diet and the photoperiod was reduced to 8L:16D. Males on a pedigree breeder program (broilerized) were reared on a 23L:1D photoperiod and unrestricted food and water intake for 6 wk. At 7 wk, males were placed on a restricted diet and the photoperiod was reduced to 8L:16D. On wk 18, both treatment groups were photostimulated (16L:8D) until the end of the experiment (50 wk). After photostimulation, there was an exponential increase in testis weight (TW), FSH, and testosterone concentrations. At 28 wk, TW from broilerized males were significantly heavier than those from control birds, and concentrations of luteinizing hormone, FSH, and testosterone were maximal at that time. After 28 wk, there was a significant decrease in FSH and testosterone concentrations that were associated with reduced TW. No correlation was observed between BW and TW. However, TW was highly correlated with FSH concentrations and daily sperm production. Our data suggest that management and photoperiod had a profound effect on testicular function that was associated with FSH concentrations in male broiler breeders.

Influence of body condition and bovine somatotropin on estrous behavior, reproductive performance, and concentrations of serum somatotropin and plasma fatty acids in postpartum Brahman-influenced cows.

Ninety-nine multiparous Brahman-influenced (1/4 to 3/8 Brahman) cows were managed to achieve low (BCS = 4.3 +/- 0.1; n = 50) or moderate (BCS = 6.1 +/- 0.1; n = 49) body condition (BC) to determine the influence of bovine somatotropin (bST) on estrous characteristics, reproductive performance, and concentrations of serum GH and plasma NEFA. Beginning 32 d postpartum, cows within each BC were assigned randomly to treatment with or without bST. Non-bST-treated cows received no treatment, and treated cows were administered bST (Posilac, 500 mg s.c.) on d -35, -21, and -7 before initiation of the breeding season. On d -7, all cows received an intravaginal, controlled internal drug-releasing (CIDR) device. On d 0 (initiation of the 70-d breeding season), the CIDR were removed and cows received prostaglandin F2alpha (PGF2alpha). Blood samples were collected from the median caudal vein of the cows at each bST treatment and at d -28 and 0. Estrous behavior was monitored by radiotelemetry during the first 30 d of the breeding season. Growth hormone was increased (P < 0.05) in low and moderate BC cows treated with bST. The percentage of cows detected in estrus during the first 30 d of the breeding season was decreased (P = 0.05) for low BC (64%) compared with moderate BC (82%) cows. The interval to first estrus tended (P = 0.07) to be shorter in low BC-bST-treated cows (3.7 +/- 1.9 d) than in moderate BC-bST-treated cows (9.6 +/- 1.8 d). During the first 30 d of the breeding season, cows in low BC had a decreased (P = 0.02) number of mounts received and increased (P = 0.001) quiescence between mounts compared with cows in moderate BC. The number of mounts received was reduced (P = 0.04) in bST-treated cows. More (P = 0.02) cows treated with bST became pregnant during the first 3 d of the breeding season compared with non-bST-treated cows. The cumulative first-service conception rate tended (P = 0.07) to be greater for bST-low BC cows than non-bST-treated cows in low or moderate BC. On d 0, NEFA were greater (P < 0.05) in bST-treated vs. non-bST-treated cows. Low BC and bST reduced the intensity of behavioral estrus in postpartum Brahman-influenced cows. However, bST increased the first-service conception rate during the first 30 d of breeding and pregnancy rates during the first 3 d of breeding in postpartum Brahman-influenced cows.

Estrous behavior and initiation of estrous cycles in postpartum Brahman-influenced cows after treatment with progesterone and prostaglandin F2alpha.

Spring-calving, crossbred (1/4 to 3/8 Brahman) primiparous (n = 56) and multiparous (n = 102) beef cows were used to evaluate the effects of progesterone, delivered via a controlled internal drug-releasing (CIDR) device, and prostaglandin F(2alpha) (PGF(2alpha)) on estrous behavior, synchronization rate, initiation of estrous cycles, and pregnancy rate during a 2-yr period. To determine luteal activity, weekly blood samples were collected 3 wk before initiation of a 75-d breeding season. Treated cows received a CIDR for 7 d beginning on d -7 of the breeding season. On d 0, CIDR were removed, and cows receiving CIDR were administered PGF(2alpha); control cows received no treatment. Cows were exposed to bulls, and estrous activity was monitored using a radiotelemetry system for the first 30 d of the breeding season. Treatment with CIDR-PGF(2alpha) increased (P < 0.05) the number of mounts received (22.5 +/- 3.0 vs. 13.7 +/- 3.9 for CIDR-PGF(2alpha) vs. untreated control cows, respectively) but did not influence duration of estrus or quiescence between mounts. Number of mounts received and duration of estrus were greater (P < 0.05) in multiparous compared with primiparous cows. Synchronization of estrus was greater (P < 0.05) in cows treated with CIDR-PGF(2alpha) (56%) compared with control cows (13%) during the first 3 d of the breeding season. More (P < 0.05) anestrous cows treated with CIDR-PGF(2alpha) than anestrous control cows were in estrus during the first 3 d (59 vs. 12%) and 30 d (82 vs. 63%) of the breeding season. Treatment with CIDR-PGF(2alpha) decreased (P < 0.05) the interval to first estrus after treatment during the first 30 d of the breeding season compared with control cows (5.5 +/- 1.1 vs. 9.0 +/- 1.4 d). First service conception rate was greater (P < 0.05) in CIDR-PGF(2alpha)-treated cows compared with control cows. Cyclic cows at initiation of the breeding season had an increased (P < 0.05) 75-d pregnancy rate compared with anestrous cows, and the pregnancy rate tended (P = 0.10) to be greater in multiparous compared with primiparous cows. We conclude that treatment of Brahman-influenced cows with progesterone via a CIDR for 7 d, along with administration of PGF(2alpha) at CIDR removal, increases the number of mounts received, improves synchronization and first service conception rates, decreases the interval to first estrus after treatment, and may be effective at inducing estrous cycles in anestrous cows.

Clostridial antibody response from injection-site lesions in beef cattle, long-term response to single or multiple doses, and response in newborn beef calves.

Experiments were conducted to compare clostridial antibody response of beef heifers that do and do not develop injection-site lesions, evaluate long-term antibody response of a single- and multiple-dose toxoid, and evaluate the ability of a clostridial toxoid to elicit an active antibody response in newborn calves. In Exp. 1, 37 weaned heifers were vaccinated (d 0) with a clostridial vaccine (Alpha-7, 2 mL, s.c.). Serum samples were collected on d 0, 28, 56, 84, and 112 to determine clostridial antibody titers. On d 28, heifers were visually inspected and palpated for injection-site lesions. The percentage of heifers that developed lesions was 64.9%. Lesioned heifers had elevated antibody titers for Clostridium chauvoei (CC) on d 28 (P < 0.08) and 84 (P < 0.07) compared with non-lesioned heifers. Clostridium sordellii (CS) and perfringens type D (CPD) antibody titers were greater in lesioned heifers than in non-lesioned heifers on d 28 and 56. In Exp. 2, long-term antibody response of Alpha-7 (A7) and Ultrabac 7 (UB7) was investigated in stocker heifers. The A7 heifers (n = 15) received one 2-mL vaccination (d 0), and the UB7 heifers (n = 15) received a 5-mL vaccination on d 0 and 28. Blood samples were collected on d 0, 28, 56, 84, 112, 140, and 180. Clostridium chauvoei, CPD, and Cl. novyi (CN) antibody titers from the A7 heifers were greater than those from the UB7 heifers on d 28. Due to the second UB7 injection, CC, CS, CN, and Cl. perfringens type C (CPC) antibody titers were greater in UB7 heifers than in A7 heifers on d 56. By d 112, titers were not different, and by d 140 all antibody titers were below detectable levels. In Exp. 3, 58 pregnant, mature, crossbred cows were vaccinated with A7 before calving. At birth, calves were carefully observed to ensure consumption of colostrum. Calves were blocked according to parturition date, and calves in each block were randomly allocated to receive A7 (s.c. at 3 +/- 3 d of age) or remain unvaccinated controls. Calves were bled at the time of vaccination (d 0) and on d 28, 56, 84, and 112. Antibody titers for CC, CPC, and CPD were elevated on d 0 and decreased throughout the experimental period (P < 0.01), but no titer differences (P > 0.10) were detected between treatment groups on any of the days sampled. These data indicated that antibody titers against clostridial diseases are enhanced when injection-site lesions develop. One injection of Alpha-7 seemed to provide the same length of protection as two injections of Ultrabac 7.

Ovulation rate and litter size in gilts immunized against androstenedione and 17alpha-hydroxyprogesterone.

Two experiments were conducted to evaluate the effects of the immunization of gilts against ovarian steroids on ovulation rate and litter size. In Exp. 1, gilts (n = five gilts/treatment) at 165+/-1.6 d of age were immunized against either carrier (Control), androstenedione, or 17alpha-hydroxyprogesterone. Age at puberty and estrous cycle length averaged 208+/-5.5 (P = 0.67) and 20.3+/-2.8 d (P = 0.41), respectively, and were not affected by treatment. The androstenedione- and 17alpha-hydroxyprogesterone immunized gilts had higher (P < 0.02) ovulation rates than Controls (14.2, 14.2, and 11.4+/-0.8, respectively). Total pigs born (P = 0.66) and pigs born live (P = 0.65) for the androstenedione-treated group were not different from Controls. Gestation length was not different (P = 0.36) between any of the treatments and the Controls (115+/-0.9 d). Procedures used in Exp. 2 were similar to those in Exp. 1, except that only Control (n= 18) and 17alpha-hydroxyprogesterone (n = 16) treatments were included and only litter size at farrowing was measured. Total pigs and pigs born live were higher in the 17a-hydroxyprogesterone-treated gilts than in the Controls (12.6 vs 10.5+/-0.6, P < 0.02; and 11.4 vs 9.2+/-0.6; P < 0.01, respectively). Data from this study indicate that litter size in gilts can be increased by immunization against 17alpha-hydroxyprogesterone.

Effects of transient prepubertal 6-N-propyl-2-thiouracil treatment on testis development and function in the domestic fowl.

It has been well established that thyroid hormones play an important role in regulating the onset of puberty and reproductive function in birds. In mammals it has been shown that transient hypothyroidism induced with the reversible goitrogen 6-N-propyl-2-thiouracil (PTU) can result in tremendous increases in testis size and sperm production and that the timing of hypothyroidism must correspond to the period of Sertoli cell proliferation. As the period of Sertoli cell proliferation is not precisely known in the fowl, an experiment was conducted to determine whether chicken testes have a similar window of sensitivity to PTU treatment. Broiler breeder male chicks (Peterson) were placed in floor pens at one day of age and reared according to the breeder's management guide for the entire 28-wk duration (controls) or up to the point of dietary treatment with PTU (0.1% w:w) for 6 wk that began at 2-wk intervals (2-8, 4-10, 6-12, 8-14, and 10-16 wk of age); after treatment, birds were returned to feed restriction and photostimulated at 20 wk of age. Birds were bled and killed, and testes were collected at 4-wk intervals. At 28 wk, one testis was fixed for histological examination and one was immediately placed in liquid N2 for sperm counts. Treatment with PTU from 6 to 12 wk of age resulted in a 96% increase in mean testis weight at 28 wk of age (treated 39.3 +/- 4.1 g per testis vs. control 20.0 +/- 1.6 g per testis). These testes exhibited normal morphology and increased relative sperm production. Treatment with PTU from either 8 to 14 or 10 to 16 wk of age resulted in approximately a 35% increase in testis mass at 28 wk of age relative to the control value (27.2 +/- 2.0 g and 27.7 +/- 3.6 g vs. 20.0 +/- 1.6 g per testis, respectively). However, both of these groups clearly demonstrated precocious puberty and abnormal spermatogenesis. These results suggest that appropriately timed PTU treatment may result in permanent increases in testis size and sperm production in the domestic fowl.

Characterization of porcine endometrial, myometrial, and mammary oxytocin binding sites during gestation and labor.

Changes in oxytocin (OT) receptor expression have been found to be an important determinant of the physiological effect of OT in several species. To date there are no published studies of OT binding sites during pregnancy in the pig. The purpose of the present study is to improve understanding of the role of OT in porcine parturition. The concentration and affinity of OT binding sites were determined for myometrium and endometrium from pregnant and postpartum gilts. Tissues were obtained after slaughter from 7 animals in each of four groups: 1) 90 days gestation, 2) 112 days gestation, 3) term after milk letdown (before delivery), and 4) within 1-3 h after farrowing. Mammary tissues were obtained for some animals in each group (n = 3-5/group). Before slaughter, blood was collected from each animal and assayed for estradiol-17 beta, progesterone, 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM), and OT. Binding of 3H-OT in the three tissues was concentration- and time-dependent. Sites of 3H-OT binding (fmol/mg protein +/- SEM) increased toward term for each tissue and remained elevated in the postpartum group. Endometrial and mammary tissues displayed the most acute increases in OT binding site concentrations while myometrial tissues displayed a more gradual increase in OT binding sites over the times studied. The binding sites displayed high affinity for 3H-OT and were characterized by linear Scatchard plots. Concentrations of estradiol-17 beta, PGFM, and OT (pg/ml +/- SEM) were positively correlated with 3H-OT binding site concentrations, whereas progestrone concentrations (ng/ml +/- SEM) were negatively correlated with binding site concentration, as determined by Pearson's Correlation Analysis. The data represent the first account of changes in the expression of OT binding sites on porcine tissues during gestation and labor.

Use of virulent hemorrhagic enteritis virus for the induction of colibacillosis in turkeys.

Three hundred fifty 1-day-old large white turkeys were reared in brooding batteries to 10 days of age, after which they were moved to floor pens on litter. At 7 weeks of age, poults were allotted into four treatment groups as follows: 1) virulent hemorrhagic enteritis virus (HEV) alone (100 turkeys), 2) Escherichia coli alone (100 turkeys), 3) HEV + E. coli (100 turkeys), and 4) negative controls (50 turkeys). HEV was given orally at 7 weeks of age, followed by E. coli challenge in the drinking water 2 days later for 10 consecutive days. All groups were observed daily for mortality, both during and after challenge. Turkeys that died or were moribund were necropsied, and cultures were taken from the liver and bone marrow for bacterial isolation. Total mortality rates were 23% in the HEV + E. coli group, 10% in the HEV-only group, 3% in the E. coli-only group, and 0% in the negative control group. Cumulative mortality values were significantly different from those of the negative controls (P < or = 0.05) for HEV only and the HEV + E. coli group. E. coli was isolated from the liver and bone marrow of almost all turkeys that died.

Use of an enzyme-linked immunosorbent assay to measure antibody levels in turkey breeder hens, eggs, and progeny following natural infection or immunization with a commercial Bordetella avium bacterin.

Twelve large white turkey hens were immunized with a commercially available Bordetella avium bacterin. Hens and eggs were tested using an enzyme-linked immunosorbent assay (ELISA) to determine the response to the bacterin. Three hundred poults were then obtained from two commercial flocks, the hens of one flock having been immunized with the same bacterin used on the group of 12 turkeys. Titers of the poults were monitored for 7 weeks, and poults were challenged by exposure to infected poults at 1, 7, 14, and 21 days post-hatch. Hens produced an antibody response following immunization, with a parallel antibody response being detected in eggs. Maternal antibodies were present in poults from immunized hens. Poult titers declined to near the level of poults from unimmunized hens by 14 days of age. Poults from immunized hens challenged at 1 and 7 days were resistant to development of clinical disease and gross lesions, whereas all poults from unimmunized hens exhibited clinical signs and gross lesions. After 14 days, the resistance of both groups to development of clinical disease, became near equal, neither group being affected as severely as the unimmunized hens challenged at days 1 and 7. Six commercial turkey breeding flocks and their progeny that had not been vaccinated for B. avium and had no history of B. avium infection were evaluated with the B. avium ELISA. There were variations between the flocks, with poult titers reflecting those found in the hens.

Variability in a commercially available enzyme-linked immunosorbent assay system. I. Assay variability.

Three experiments were conducted to characterize the variation in enzyme-linked immunosorbent assay (ELISA) kits for infectious bronchitis virus (IBV) and infectious bursal disease virus (IBDV). Expt. 1 was carried out to determine the variation in assay results when the same pools of low-, medium-, and high-titered serum were assayed. Significant variation occurred among separate lots and among test plates within the same lots for the IBV and IBDV assays. In most cases, variability between days and among technicians was not significant. Coefficients of variation were larger than is acceptable for immune-type assays. In the IBDV assay with high-titered serum, most of the wells in the plates reached maximum absorbance and were not capable of detecting titers above 1:8000-1:9000. Expt. 2 was conducted to determine the effects of varying the length of the ortho-phenylene-diamine (OPD) incubation time upon assay results. Either 7-, 12-, or 15-minute OPD incubation times were used. Incubation time significantly affected mean titer at all combinations of assay types and times, except determinations on the low-titered IBV samples. Expt. 3 was conducted to determine the effects of three different dilution methods on observed IBDV titer. The use of non-standard dilutions had significant effects on observed titer. In the medium- and high-titered samples, the use of two different dilution methods at 1:5000 rather than 1:500 resulted in titers that were three to four times those observed at the 1:500 dilution.

Variability in a commercially available enzyme-linked immunosorbent assay system. II. Laboratory variability.

An experiment was conducted to determine the amount of variability that occurred in enzyme-linked immunosorbent assays when samples from common serum pools were assayed in five different labs on three consecutive days. Low- (approximately 1:2000), medium- (approximately 1:4000), and high-titered (approximately 1:8000) serum pools were distributed to five poultry industry laboratories that cooperated in the study. Results varied significantly among different laboratories and among different days in the same lab. Variation among days within the same laboratory and among laboratories were large. The greatest variability occurred among labs. Correlations between mean daily titer and laboratory ambient temperature were small and not significant. The amount of variability within and among different laboratories that were observed indicate that single determinations on individual serum samples are not likely to give a reliable estimate of antibody titer. The large variability within labs further indicates the need for standard reference pools of positive serum to be included in assays in order to substantiate assay results.

Histological development and histochemical localization of enzymes in rumen and reticulum in bovine fetuses.

Thirty Holstein fetuses from 100 to 251 d after conception were utilized to study prenatal anatomical development of the epithelium of the rumen and reticulum. Four calves at birth were included in the study for comparison. Tissue sections were frozen and stained to locate specific enzymes. At 100 d, the epithelial layer of the rumen was differentiated into a thin basal zone and a thickened superficial zone of undifferentiated cells. The basement membrane was straight, and in both zones cells were perpendicular to it. At 120 to 141 d, low, primary undulations were detected in the basal zone, basement membrane and underlying lamina propria. At 150 to 166 d, secondary undulations and incipient papillae began to resemble the papillae of mature mucosa. In rumen papillae of 192-d to 215-d fetuses, shallow furrows began to separate papillae apexes from the mass of epithelium. In fetuses 244 to 251 d, the papillae began to be a separate entity. At birth, the basal position of the papillae still remained fused. An incipient separation between the papillae was seen. Several dehydrogenase enzymes, including those associated with the Krebs cycle and reductase associated with energy transformation, were observed in both ruminal and reticular tissue. Alkaline phosphatase activity was localized in the stratum corneum and in blood vessels. Development of the honeycomb configuration of reticular epithelium was evident in the 100-d fetus and progressed rapidly with age.

In vivo studies with dimethyldithiocarbamate, a possible new antimicrobial for use against Aspergillus fumigatus in poultry.

Dimethyldithiocarbamate (DmDTC), the carbamate analogue, was tested for therapeutic efficacy in a series of in vivo challenge trials using 5- and 10-week-old white leghorn chickens. Challenge organisms were Pasteurella multocida X-73, Escherichia coli O1:K1, and Aspergillus fumigatus. Birds were evaluated for survival rates, lesion scores, and the rate at which the bacteria or mold could be reisolated following challenge. Results showed DmDTC to be ineffective against P. multocida and E. coli at the treatment levels and in the form used in these trials, but DmDTC significantly reduced lesion scores and inhibited the rate of isolation of A. fumigatus compared with untreated infected birds.

In vitro studies with dimethyldithiocarbamate, possible new antimicrobial for use in poultry.

Tests were conducted to determine the in vitro efficacy of the dithiocarbamate analogue, dimethyldithiocarbamate (DmDTC), against selected poultry pathogens. Organisms studied were two bacteria, Pasteurella multocida and Escherichia coli, and a mold, Aspergillus fumigatus. Zone of inhibition and the minimum inhibitory concentration were determined for each organism. DmDTC was effective in vitro against all organisms tested, with A. fumigatus showing greatest overall sensitivity.

Apparent digestibility of nitrogen and nitrogen retention of forages fed to steers in metabolism stalls.

Holstein steers in metabolism stalls were utilized to determine apparent digestibility of N (DN), N retention (NR) expressed as a percentage of total N consumed, and Mcal/kg digestible energy (DE) when diets of seven different classes of forages were fed. The best predictive equation for digestibility of N in the 153 forages studied was DN(%) = -98.1065 + 11.4724 (%CP) + 41.4475 (DE) - .1498 (%CP)2 - 1.2541 (DE)2 - 1.9309 (CP) (DE), with R2 = .74 and Sy.x = 8.63, where %CP is the percent crude protein of the forage. The best predictive equation for DN of sorghum silages, corn silages, legume hays and temperate grass hays contained both %CP and DE as predictor variables. The best predictive equations for DN of sorghum-sudan and bermudagrass hays contained only %CP and (%CP)2 as predictor variables. The predictive equation for DN of 14 alfalfa hays involved only the linear relationship to %CP. The best scheme for predicting NR as a percentage of N consumed in 116 forages was a combination of three equations as follows: 1) NR(%) = -47.0797 + 6.4733 (%CP) - .1542 (%CP)2 for forages, where DE = less than 2.42 Mcal/kg; 2) NR(%) = -67.6306 + 10.1354 (%CP) - .2726 (%CP)2, where DE = 2.42 - 2.87 Mcal/kg; and 3) NR(%) = 28.3458 + 4.4722 (%CP) - .1263 (%CP)2, where DE = greater than 2.87 Mcal/kg; R2 = .42 and Sy.x = 14.86.(ABSTRACT TRUNCATED AT 250 WORDS)