Comparisons among Tuli-, Brahman-, and Angus-sired heifers: intake, digesta kinetics, and grazing behavior

As part of an evaluation of Tuli crossbred cattle, forage intake, digesta kinetics, and grazing behavior were estimated in two Texas environments. In humid east Texas, Tuli x Brahman heifers were compared with purebred Angus and Brahman and Angus x Brahman heifers. Fecal output, forage intake, compartmental mass, and compartmental residence time did not differ among breeds. Angus and Brahman heifers had different (P < . 02) gastrointestinal residence times (51.1+/-1.56 vs 43.1+/-1.56 h, respectively), but values for the purebreds did not differ from those for Tuli x Brahman or Angus x Brahman heifers. Angus heifers had shorter (P < .05) 24-h grazing times (398+/-15.4 min/d) and fewer (P < .05) grazing periods (7+/-.4) than Tuli x Brahman (552+/-16.8 min/d and 10+/-.4), Angus x Brahman (507+/-18.4 min/d and 9+/-.5), and Brahman (560-/+ 16.8 min/d and 9+/-.4, respectively) heifers. In semiarid southwest Texas, Tuli x Angus heifers were compared with purebred Angus and Brahman and Brahman x Angus heifers. Fecal output and forage intake were similar in Tuli x Angus and Brahman x Angus heifers (14.2+/-.69 and 14.9+/-.91 g fecal DM/ [d.kg BW] and 24.5+/-1.33 and 25.6+/-1.75 g/d of forage DMI, respectively) but higher (P < .05) than those of purebred Brahman heifers (12.2+/-.64 and 20.3+/-1.23 g/[d.kg BW] of fecal DM and forage DMI, respectively). Grazing times did not differ among breeds. We conclude that Tuli-sired heifers are likely to be as productive as Brahman crossbred heifers in Texas, based on the similarities in intake, digesta dynamics, and grazing behavior.     

Simulated influence of postweaning production system on performance of different biological types of cattle: III. Biological efficiency

Methods were developed and incorporated into a previously published computer model to predict ME intake and calculate biological efficiencies in terms of grams of empty BW (EBW) and fat-free matter (FFM) gained/megacalorie of ME consumed from weaning to slaughter. Efficiencies were calculated for steers from F1 crosses of 16 sire breeds (Hereford, Angus, Jersey, South Devon, Limousin, Simmental, Charolais, Red Poll, Brown Swiss, Gelbvieh, Maine Anjou, Chianina, Brahman, Sahiwal, Pinzgauer, and Tarentaise) mated to Hereford and Angus dams, grown under nine backgrounding systems, finished at either a low (1.0 kg) or high (1.36 kg) ADG, and slaughtered at 300 kg carcass weight, small or greater degree of marbling, and 28% carcass fat. Backgrounding systems were high ADG (.9 kg) for 111, 167, or 222 d, medium ADG (.5 kg) for 200, 300, or 400 d, and low ADG (.25 kg) for 300 or 400 d, and 0 d backgrounding. The high ADG finishing system was more biologically efficient than the low ADG finishing system, and generally backgrounding systems were less biologically efficient than direct finishing after weaning (0 d backgrounding). Large-framed breeds were more efficient at the constant carcass weight and carcass fatness end point, and breeds that achieved the marbling end point at low levels of carcass fatness were more efficient at this end point. Some small-framed breeds gained EBW more efficiently but gained FFM less efficiently than some of the large-framed breeds. Variation in efficiency between genotypes was greatest with 0 d backgrounding and decreased in the other backgrounding systems.     

Heterogeneity of variances for carcass traits by percentage Brahman inheritance

Heterogeneity of carcass trait variances due to level of Brahman inheritance was investigated using records from straightbred and crossbred steers produced from 1970 to 1988 (n = 1,530). Angus, Brahman, Charolais, and Hereford sires were mated to straightbred and crossbred cows to produce straightbred, F1, back-cross, three-breed cross, and two-, three-, and four-breed rotational crossbred steers in four non-overlapping generations. At weaning (mean age = 220 d), steers were randomly assigned within breed group directly to the feedlot for 200 d, or to a backgrounding and stocker phase before feeding. Stocker steers were fed from 70 to 100 d in generations 1 and 2 and from 60 to 120 d in generations 3 and 4. Carcass traits included hot carcass weight, subcutaneous fat thickness and longissimus muscle area at the 12-13th rib interface, carcass weight-adjusted longissimus muscle area, USDA yield grade, estimated total lean yield, marbling score, and Warner-Bratzler shear force. Steers were classified as either high Brahman (50 to 100% Brahman), moderate Brahman (25 to 49% Brahman), or low Brahman (0 to 24% Brahman) inheritance. Two types of animal models were fit with regard to level of Brahman inheritance. One model assumed similar variances between pairs of Brahman inheritance groups, and the second model assumed different variances between pairs of Brahman inheritance groups. Fixed sources of variation in both models included direct and maternal additive and nonadditive breed effects, year of birth, and slaughter age. Variances were estimated using derivative free REML procedures. Likelihood ratio tests were used to compare models. The model accounting for heterogeneous variances had a greater likelihood (P < .001) than the model assuming homogeneous variances for hot carcass weight, longissimus muscle area, weight-adjusted longissimus muscle area, total lean yield, and Warner-Bratzler shear force, indicating improved fit with percentage Brahman inheritance considered as a source of heterogeneity of variance. Genetic covariances estimated from the model accounting for heterogeneous variances resulted in genetic correlations of or near unity. These results suggest that different genetic values be considered for genetic evaluation of carcass yield and shear force traits from steers with different degrees of Brahman inheritance.     

Effects of growth rate on carcass composition and lipid partitioning at puberty and growth hormone, insulin-like growth factor I, insulin, and metabolites before puberty in beef heifers

The effect of three rates of gain on carcass composition, lipid partitioning, age and BW at puberty, and concentrations of growth hormone (GH), IGF-I, insulin, glucose, and NEFA in plasma were evaluated in 38 Angus x Hereford heifers. Heifers were allotted by BW and age to three treatments with a replication in each of 2 yr: full-fed (n = 13; FF) to gain 1.36 kg/d; limit-fed (n = 12; LF) to gain .68 kg/d; maintenance-full-fed (n = 13; MFF) to gain .23 kg/d for 16 wk, then full-fed to gain 1.36 kg/d. Heifers were slaughtered within 10 d after the onset of puberty. At slaughter, kidney, pelvic, and heart fat (KPH) and udder (UDDER) were separated from carcass, as was fat surrounding viscera (OM). After 48 h at 4 degrees C a carcass side was dissected into subcutaneous fat (SC), intermuscular fat (SEAM), soft tissue (SFT = inseparable lean and fat), LEAN, and BONE. In yr 1, LF heifers (431 d) were older (P < .05) than MFF heifers (371 d) at puberty, but age of FF heifers (389 d) did not differ (P > .10) from that of LF and MFF heifers. In yr 2, FF heifers (351 d) were younger (P < .05) than LF and MFF heifers (398 and 434 d, respectively). The FF heifers had greater (P < .05) BW and a greater (P < .01) percentage of lipid in the carcass at puberty than LF and MFF heifers. During the first 16 wk of treatment, concentrations of NEFA were greater in heifers with slower daily gains (MFF > LF > FF; P < .01). Concentrations of NEFA were lesser and concentrations of IGF-I and insulin were greater in plasma of FF than in that of MFF heifers during the 10 wk before puberty. Treatment significantly altered age, BW, carcass composition, and lipid partitioning at puberty in beef heifers. We conclude that the percentage of body fat is not the sole regulator of puberty, and age may be an important modulator in determining the onset of puberty in beef heifers.     

Germplasm evaluation in beef cattle-cycle IV: birth and weaning traits

Gestation length, unassisted calving percentage, perinatal mortality, calf crop weaned (survival from birth to weaning), birth weight, and 200-d weaning weight of 2,597 calves born and 2,433 calves weaned are reported for F1 crosses resulting from matings of Angus, Hereford, Charolais, Gelbvieh, Pinzgauer, Shorthorn, Galloway, Longhorn, Nellore, Piedmontese, and Salers sires to Angus and Hereford dams (> or = 3 yr of age) in Cycle IV of the Germplasm Evaluation (GPE) Program at the U.S. Meat Animal Research Center. Hereford and Angus sires included 1) reference sires born from 1963 to 1971 used in previous cycles of the GPE Program, 2) sires born from 1982 to 1985 (1980s), and 3) sires born from 1983 to 1985 used in natural service clean-up matings. Effects of sire breed of calf were significant for gestation length, unassisted calving percentage, birth weight, and 200-d weaning weight. Gestation length was significantly longer for Nellore than for Charolais, Galloway, Longhorn, Piedmontese, and Salers, which were in turn longer than for Hereford-Angus and Shorthorn. Rankings for birth weight tended to be inversely related to those for calving ease, except for Shorthorn and Salers sires, which required low assistance relative to their heavy birth weights. Rankings for 200-d weight among AI-sired progeny were as follows: Charolais (231.3), Nellore (229.7), Salers (225.5), Shorthorn (223.8), 1980s Hereford-Angus (223.1), Piedmontese (220.0), Galloway (209.5), reference Hereford-Angus (210.1), and Longhorn (199.0); differences > or = 6.5 kg were significant.     

Covariance components and prediction for additive and nonadditive preweaning growth genetic effects in an Angus-Brahman multibreed herd

Estimates of covariances and sire expected progeny differences of additive and nonadditive direct and maternal genetic effects for birth and weaning weights were obtained using records from 1,581 straightbred and crossbred calves from the Angus-Brahman multibreed herd at the University of Florida. Covariances were estimated by Restricted Maximum Likelihood, using a Generalized Expectation-Maximization algorithm applied to multibreed populations. Estimates of heritabilities and additive genetic correlations for straightbred and crossbred groups were within the ranges of values found in the literature for these traits. Maximum values of interactibilities (ratios of nonadditive genetic variances to phenotypic variances) and nonadditive correlations were somewhat smaller than heritabilities and additive genetic correlations. Sire additive and total direct and maternal genetic predictions for birth and weaning weight tended to increase with the fraction of Brahman alleles, whereas nonadditive direct and maternal genetic predictions were similar for sires of all Angus and Brahman fractions. These results showed that it is feasible to evaluate sires for additive and nonadditive genetic effects in a structured multibreed population. Data from purebred breeders and commercial producers will be needed to accomplish the same goal at a national level.     

Genotypic effects on norepinephrine-induced changes in thermogenesis, metabolic hormones, and metabolites in newborn calves

Heat production was measured in newborn Angus-, Brahman-, and Tuli-sired calves born to Angus (n = 20) and Brahman (n = 26) dams, before (thermoneutral metabolic rate, TMR) and after norepinephrine (NE) infusion (peak metabolic rate, PMR), to assess genotypic effects on nonshivering thermogenesis in brown adipose tissue. Calves were fed pooled colostrum, fitted with jugular catheters, and placed in a temperature-controlled (37 degrees C) water immersion system. Heat production, determined by indirect calorimetry, and tympanic temperature were measured continuously in calves from approximately 3 to 6 h of age. Blood samples were collected at birth and at 0, 5, 20, 40, 60, 80, 100, and 120 min relative to NE infusion (35 micrograms.min-1.kg BW-1 for 4 min), and plasma was analyzed for metabolites (glucose, NEFA, and urea nitrogen [PUN]) and hormones (cortisol, triiodothyronine [T3] and thyroxine [T4]). Weight-specific TMR (cal.min-1.kg-1) was not affected by breed of sire or dam, although weight-specific PMR (cal.min-1.kg-1) was lower (P < .01) in Brahman-sired calves than in Angus- or Tuli-sired calves and was lower (P < .001) in calves born to Brahman rather than Angus dams. The reduction in weight-specific PMR due to the maternal Brahman influence was sire-breed dependent, and the reduction was largest (P < .01) for Tuli-sired (34.3%), intermediate (P < .05) for Brahman-sired (15.1%), and lowest (P > .25) for Angus-sired calves (4.1%). The PMR:TMR ratio was 1.80 and 2.21 +/- .06 in calves born to Brahman and Angus dams, respectively. Peak tympanic temperature was .6 degree C lower (P < .01) in calves born to Brahman rather than Angus dams. At birth, plasma NEFA concentrations were higher (P < .001) and glucose tended (P = .13) to be higher in calves born to Brahman rather than Angus dams. Cortisol, T3, and T4 concentrations at birth were higher in calves born to Brahman dams than in those born to Angus dams. These results suggest that calves born to Brahman dams may have less thermogenically active brown adipose tissue than calves born to Angus dams, which may contribute to the relative cold intolerance of calves with Bos indicus inheritance.     

Reproductive performance of cows mated to and preweaning performance of calves sired by Brahman vs alternative subtropically adapted breeds

Comparisons involving Brahman and Brahman-derivative (Brangus, Santa Gertrudis, Beef-master, Simbrah, Braford) sires indicate the following: 1) cows mated to Brangus and Santa Gertrudis bulls had a shorter gestation length than cows mated to Brahman bulls, 2) calves sired by Brangus and Beefmaster bulls were lighter at birth and weaning than calves sired by Brahman bulls, and 3) birth and weaning weights were similar for calves sired by Santa Gertrudis and Brahman bulls and for calves sired by Simbrah and Brahman bulls. Comparisons involving Brahman and other Zebu (Sahiwal, Nellore, Gir, Indu-Brazil, Boran, Romana Red) sires indicate that gestation length was slightly longer for cows mated to Sahiwal and Nellore bulls and that, relative to the Brahman, birth and weaning weights were similar to or lighter for calves sired by bulls of the other Zebu breeds. The only exception to this pattern was birth weight of Indu-Brazil-sired calves, which were heavier than calves sired by Brahman bulls. Comparisons involving Brahman and non-Zebu subtropically adapted (Tuli, Senepol) sires indicate that cows mated to Tuli bulls had a slightly shorter gestation length than cows mated to Brahman bulls and that birth and weaning weights of calves sired by Tuli and Senepol bulls were lighter than those of calves sired by Brahman bulls.     

Comparison of sire breed solutions for growth traits adjusted by mean expected progeny differences to a 1993 base

Records on growth traits were obtained from five Midwestern agricultural experiment stations as part of a beef cattle crossbreeding project (NC-196). Records on birth weight (BWT, n =3,490), weaning weight (WWT, n = 3,237), and yearling weight (YWT, n = 1,372) were analyzed within locations and pooled across locations to obtain estimates of breed of sire differences. Solutions for breed of sire differences were adjusted to the common base year of 1993. Then, factors to use with within-breed expected progeny differences (EPD) to obtain across-breed EPD were calculated. These factors were compared with factors obtained from similar analyses of records from the U. S. Meat Animal Research Center (MARC). Progeny of Brahman sires mated to Bos taurus cows were heaviest at birth and among the lightest at weaning. Simmental and Gelbvieh sires produced the heaviest progeny at weaning. Estimates of heritability pooled across locations were .34, .19, and .07 for BWT, WWT, and YWT, respectively. Regression coefficients of progeny performance on EPD of sire were 1.25+/-.09, .98+/-.13, and .62+/-.18 for BWT, WWT, and YWT, respectively. Rankings of breeds of sire generally did not change when adjusted for sire sampling. Rankings were generally similar to those previously reported for MARC data, except for Limousin and Charolais sires, which ranked lower for BWT and WWT at NC-196 locations than at MARC. Adjustment factors used to obtain across-breed EPD were largest for Brahman for BWT and for Gelbvieh for WWT. The data for YWT allow only comparison of Angus with Simmental and of Gelbvieh with Limousin.     

Genotype x environment interactions in preweaning traits of purebred and reciprocal cross Angus and Brahman calves on common bermudagrass and endophyte-infected tall fescue pastures

Preweaning data on 486 Angus, Brahman, and reciprocal cross calves (AB, BA) managed on common bermudagrass or endophyte-infected tall fescue were used to evaluate the interactions of forage type and sex of calf with direct effects, individual heterosis, and maternal effects. Calves were spring-born in 1988, 1989, 1990, and 1991 to five sires of each breed. Male calves were castrated at birth, and calves were not creep-fed. Average values of heterosis for birth weight, 205-d weight, weaning hip height, and weaning weight:height ratio (WT/HT) were important (P < .01) and consistent across forage environment. Heterosis for birth weight was larger in bull calves than in heifer calves (P < .05), whereas heterosis for other preweaning traits were consistent across sex of calf. Average maternal effects for WT/HT (P < .10) were important and consistent across forage environment. Maternal effects for birth weight were larger with bull calves than with heifer calves (P < .01). Maternal effects for weaning hip height favored the Angus dam managed on bermudagrass (P < .05) but not managed on fescue. A similar but nonsignificant trend occurred in maternal effects for 205-d weight. Direct effects for birth weight were larger in bull calves than in heifer calves (P < .01). Direct effects for weaning height were larger in calves managed on bermudagrass than in calves managed on tall fescue (P < .07). A similar but nonsignificant trend was evident in direct effects for 205-d weight. Direct effects for WT/HT were relatively small and unimportant.(ABSTRACT TRUNCATED AT 250 WORDS)     

Heat tolerance in Tuli-, Senepol-, and Brahman-sired F1 Angus heifers in Florida

We investigated heat tolerance and growth rate in two trials under ambient conditions in central Florida. Trial 1 (1994) involved 38 Brahman (B), 21 Senepol (S), 19 B x Angus (A), 20 S x A, and 20 Tuli (T) x A heifers. Trial 2 (1995) involved 13 A, 35 B, 30 S, 23 B x A, 17 S x A, and 28 T x A heifers. Measurements were made on three consecutive weeks during the hotter and cooler seasons of each year and included rectal temperature (RT, degrees C), respiration rate (RR, bpm), temperament score (TS; 1 = very docile, 5 = very aggressive), blood packed-cell volume (PCV), and plasma cortisol concentration (CORT). Data for RT were transformed (log10 [RT - 37]) before analysis. On the hottest date in Trial 1, log10 RT was not different between B (.39 +/- .011) and B x A (.37 +/- .016) or between T x A (.35 +/- .015) and B x A, but log10 RT was lower (P < .05) in S x A (.30 +/- .015) than in either S (.35 +/- .015) or T x A. On all dates in Trial 1, RR was lower (P < .05 to .001) and PCV was higher (P < .05 to .001) in B than in B x A. There were few differences in TS except on two dates when B scored higher (P < .01 to .001) than B x A, and these differences were associated with higher (P < .05) CORT in B than in B x A. Using initial BW as a covariate, adjusted ADG (kg) of T x A (.52 +/- .023) was not different from adjusted ADG of B x A (.57 +/- .024) or S x A (.54 +/- .023). On the hottest date in Trial 2, log10 RT and RR were higher (P < .001) in A (.59 +/- .017, 74 +/- 2.7) than in B (.47 +/- .010, 39 +/- 1.6), S (.42 +/- .011, 50 +/- 1.8), and crossbred heifers (.47 +/- .011, 60 +/- 1.8; .43 +/- .014, 55 +/- 2.4; and .50 +/- .012, 48 +/- 2.0 for T x A, S x A and B x A, respectively), and RR was higher (P < .001) in B x A than in B. On the coolest date in Trial 2, RR was slightly lower in B (32 +/- .5) than in A(34 +/- .7, P < .01) and B x A (36 +/- .6, P < .001) and was associated with higher PCV in B than in A. On both dates, TS and CORT were higher (P < .01) in B than in A. In Trial 2, adjusted ADG (kg) was higher (P < .01) in B (.43 +/- .017) than in A (.32 +/- .033), higher (P < .001) in S (.45 +/- .018) than in A, and higher (P < .001) in crossbreds (B x A [.53 +/- .023] + S x A [.44 +/- .025] + T x A [.46 +/- .019]) than in A. These data indicate that heat tolerance in F1 crosses of tropically adapted breeds (Tuli, Senepol, Brahman) with a temperate breed (Angus) is similar to heat tolerance displayed by purebred tropical breeds (Senepol, Brahman).     

Effect of nutritional management, trace mineral supplementation, and norgestomet implant on attainment of puberty in beef heifers

We conducted a study to evaluate the influences of nutritional management, trace mineral supplementation, and exogenous progesterone on attainment of puberty in beef heifers. Heifers (n = 180) were assigned at weaning to blocks and treatments. Treatments included two dietary regimens (corn silage vs pasture + oatlage), trace mineral supplementation, and puberty induction strategy (with or without progestin implant). Heifers that received pasture + oatlage were managed on grass-legume pastures from October 14 until December 14 and were then placed in pens and fed an oatlage-based diet through May 1994. Heifers fed the corn silage-based diet were housed in pens throughout the study. Norgestomet was implanted in half of the heifers on April 11 for 10 d. Progestin implant increased (P < .05) the number of heifers that had attained puberty by the end of the study, compared with nonimplanted heifers (89% vs 71%). Trace mineral supplementation did not affect percentage of heifers that reached puberty before the implant period. Plasma copper levels were below recommended levels in heifers fed oatlage-based diets without trace minerals. We conclude that heifers can be placed on regrowth in irrigated pastures during the fall and still make acceptable gains for attainment of puberty the following spring and that progestin treatment can aid in inducing heifers to reach puberty.     

Genetic components for milk production of tarentaise, hereford, and tarentaise x hereford cows

The objective of this study was to estimate genetic components for milk production of Hereford (HH), Tarentaise (TT), and Hereford x Tarentaise or Tarentaise x Hereford (HT) cows under range conditions at the Northern Agricultural Research Center, Havre, MT. Milk production of 494 cow-calf pairs was estimated by the weigh-suckle-weigh procedure from 1989 to 1994. Milk production and cow and calf weights were measured at 40 d (early) and 120 d (late) of lactation. The mating scheme was a 3 x 3 design in which HH, HT, and TT cows were mated with HH, HT, and TT sires, producing calves that were varying percentages of Hereford and Tarentaise. Data were analyzed by least squares procedures according to a model that included year, age of cow, sex of calf, linear regression on calf age, and linear regressions on coefficients that coded for various genetic components. These genetic components were breed individual, breed maternal, breed grand maternal, individual heterosis (calf heterosis), and maternal heterosis (cow heterosis). Coefficients for genetic components were such that breed effects estimated TT-HH and regressions on heterosis values estimated the full effect of heterosis. The breed individual genetic component was significant only for calf early and late weights; Tarentaise calves were lighter. Breed maternal was significant for most traits, and these effects were positive for milk production (2.16 and 3.77 kg/d for early and late, respectively) and calf weights but negative for cow weights. Individual heterosis was not significant for early milk production but was significant for late milk production (1.05 kg/d) and calf weights (2.3 and 8.1 kg for early and late, respectively). Maternal heterosis was significant for most traits and increased early milk production (1.25 kg/d), calf weights (4.5 and 5.8 kg for early and late, respectively), and cow weights (18.1 and 6.0 kg for early and late, respectively).     

Experimental infection of pregnant cattle with the vaccine candidate Brucella abortus strain RB51: pathologic, bacteriologic, and serologic findings

To determine the placental tropism and abortigenicity of the vaccine candidate Brucella abortus strain RB51 (SRB51), a rough mutant of the virulent strain 2308, ten Polled Hereford heifers were inoculated intravenously in the 6th month of gestation. Heifers were euthanatized and examined at postinoculation week (PIW) 8 (n = 5) or at full term (n = 5). Four of five infected heifers sampled at PIW 8 and three of four infected heifers at term had placentitis, whereas reproductive tissues of three normal cows used for comparison had no placentitis. Numerous macrophages, immunoreactive for SRB51 antigen, as well as neutrophils, fibrin, and cell debris filled the arcade zone between chorion and maternal septae. Trophoblastic epithelium of the placentomal arcade zone had intracellular bacteria that were immunoreactive for SRB51 antigen. The tips of maternal septa had a lymphoplasmacytic infiltrate with small multifocal erosions and ulcerations of maternal epithelium. SRB51 was cultured from all tissues in which lesions were seen. Placentae of one cow from each group had no placentitis and contained no SRB51. In mammae, interstitial lymphoplasmacytic infiltrates and suppurative infiltrates within alveoli and intralobular ductules were seen in two of five heifers at PIW 8. SRB51 was cultured from liver, spleen, lung, and bronchial lymph nodes in four of five calves at PIW 8 and three of four full-term calves, but no lesions were seen. One near-term heifer had disseminated infection, placentitis, and lymphoplasmacytic endometritis, and delivered a premature weak calf. These results establish that SRB51 is less abortifacient than previously published reports with strain 19, in that only one of four heifers delivered prematurely following intravenous inoculation with SRB51, whereas intravenous inoculation with strain 19 leads to 100% abortion. However, it also shows that SRB51 can infect the bovine placenta, mammary gland, and fetus, can induce placentitis, and, in some cases, can lead to preterm expulsion of the fetus.     

Efficacy of a temperature-sensitive modified-live bovine herpesvirus type-1 vaccine against abortion and stillbirth in pregnant heifers

OBJECTIVE: To evaluate the efficacy of a commercially available temperature-sensitive modified-live bovine herpesvirus type-1 (BHV-1) vaccine against BHV-1 challenge-induced abortion and stillbirth. DESIGN: Prospective randomized control trial. ANIMALS: 20 cycling, nonpregnant, BHV-1 seronegative heifers of various breeds and weights, 12 to 15 months old. PROCEDURE: Heifers were randomly assigned to a vaccinate (n = 10) or nonvaccinate control (n = 10) group. Seventeen to 26 days after members of the vaccinate group received a second dose of vaccine, all heifers were artificially inseminated. Heifers were challenged intravenously with Cooper strain BHV-1 between days 177 and 187 of gestation. Aborted fetuses and stillborn calves were necropsied, and tissues collected for histologic examination and virus isolation. Heifers, calves, and fetuses were tested for BHV-1 antibody throughout the study. RESULTS: The difference in number of abortions or stillbirths between vaccinated heifers (1/10) and control heifers (10/10) was significant (P < 0.003). Seven of 10 control heifers had a virus neutralization antibody titer to BHV-1 at abortion or stillbirth that declined or remained unchanged from their titer at a previous serologic evaluation (7 to 66 days earlier). CLINICAL IMPLICATIONS: Prebreeding vaccination of replacement heifers with modified-live BHV-1 vaccine provides fetal protection at 6 months of gestation (7 months after vaccination) and appears to be a reasonable precaution to control economic losses associated with BHV-1 infection. Abortions induced by BHV-1 are not necessarily associated with rising or markedly high virus neutralization antibody titers. These titers should be used cautiously when assessing the role of BHV-1 in bovine abortion and stillbirth.     

Adrenal responses of Angus x Hereford cattle to the stress of weaning

To test adrenal responsiveness of beef cattle to stress, plasma norepinephrine, epinephrine, and cortisol responses of Angus x Hereford cattle to weaning were measured in blood samples taken from 1) eight cows and their 4- to 6-mo-old calves before and after separation and, the following day, before and after being reunited and 2) an equal number of control animals. After separation and before they were reunited, dams were returned to their original pen and calves to an adjacent pen. Experimental trials were conducted every 2 wk and included two cow/calf pairs per trial. Norepinephrine concentrations tended to increase in calves after separation, were increased (+82 pg/mL, P < .01) on the 2nd d before animals were reunited, and decreased (-88 pg/mL, P < .01) after animals were reunited. Epinephrine concentrations tended to increase in calves after separation, were increased in calves (+128 pg/mL, P < .001) and dams (+104 pg/mL, P < .001) on the 2nd d before animals were reunited, and decreased after calves (-162 pg/mL, P < .001) and dams (-101 pg/ml, P < .001) were reunited. There were no significant effects of time on catecholamine concentrations for control animals. Cortisol concentrations for treated and control animals tended to increase in sequential samples each day; however, the increases were small (approximately 1 ng/mL) and concentrations remained low (> 5 ng/mL). In conclusion, peripheral catecholamine concentrations in beef calves and epinephrine concentrations in dams increased in response to stress associated with weaning and separation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of ignoring random sire and dam effects on estimates and standard errors of breed comparisons

Data were weights of F1 calves and weaning weights of top-cross progeny from sires and maternal grandsires of 13 breeds. Three analyses were performed on each trait to obtain estimates and standard errors of breed effects needed to calculate across-breed EPD and accuracies. Model (R) for records of F1 progeny contained fixed effects for birth year and date of birth, sex, age and breed of dam, and breed of sire, and a random residual effect. The second analysis included random effects for sires (RS), and the third analysis included random effects for sires and dams (RSD). In maternal analysis of top-cross progeny, model (Rm) contained fixed effects for cycle of experiment, age of dam, year of birth, sex, breeds of maternal grandam and grandsire, and breed of sire, and a random residual effect. In addition, the second and third analyses fit random effects for maternal grandsires (RSm) and for maternal grandsires and daughters of maternal grandsires (RSDm). Estimates of breed of sire effects changed only slightly for different models. Total variance increased in RSD and RS relative to R. Standard errors of breed of sire comparisons were underestimated with Model R, compared to Models RS and RSD. Standard errors of other contrasts were generally not affected. Variance components, breed effects, and standard errors followed patterns for Rm, RSm, and RSDm similar to those for R, RS, and RSD. Ignoring random variation due to sires and dams underestimated standard errors of breed of sire comparisons.     

Protein requirements of sheep in late pregnancy: partitioning of nitrogen between gravid uterus and maternal tissues

The objective of this study was to quantify effects of maternal protein nutrition on N accretion or loss in conceptus and maternal tissues of ewes during late pregnancy. Ewes, pregnant with twins, were fed low (LP, 79 g CP/kg DM), medium (MP, 116 g CP/kg DM), or high (HP, 157 g CP/kg DM) protein diets, each with an estimated ME concentration of 2.7 Mcal/kg DM, between d 111 and 140 of pregnancy; all ewes had been fed the same diet (2.7 Mcal ME, 120 g CP/kg DM) for the previous 30 d (d 80 to 110). Dry matter intakes were varied (LP = 1.0, MP = 1.2, and HP = 1.4 kg/d) according to predicted energy costs of protein deposition for each diet. Nitrogen accretion was estimated by comparative slaughter (d 140 minus d 110) and by collection of excreta between d 120 and 130. Fresh weights of maternal and gravid uterine tissues were measured at slaughter, before proximate analysis of these components. Whole-body N retention was directly and linearly related to N intake, but efficiency of deposition of apparently absorbed N decreased linearly with increasing N intake (LP, .79; MP, .70; HP, .62). Nitrogen accretion in the gravid uterus, maternal viscera, and mammary gland was significantly less in LP than in MP or HP ewes. Nitrogen balance in maternal carcass tissues was linearly related to N intake, ranging from a negative value in LP ewes to a positive value in HP ewes (LP, -63 g; MP -39 g; HP, 55 g). These data provide the basis for estimating N requirements for protein accretion in the conceptus and in maternal tissues during late pregnancy. They also highlight the capacity of maternal carcass tissues to mobilize or deposit amino acids in response to variations in dietary protein supply.     

Preweaning growth traits for Senepol, Hereford, and reciprocal crossbred calves and feedlot performance and carcass characteristics of steers

We conducted a multiyear study in two phases to determine preweaning performance traits of Senepol (S x S), Hereford (H x H), and reciprocal (S x H and H x S) F1 crossbred calves and feedlot performance and carcass characteristics of steers. In Phase I, from 1985 to 1989, data from S x S (n = 194), H x H (n = 383), and S x H (n = 120) calves were used. Numbers of S x S cows were increased during Phase I so that data from H x S (n = 74) calves could be included in Phase II (1990 to 1992) in addition to S x S (n = 118), H x H (n = 130), and S x H (n = 56) calves. Also during Phase II, feedlot performance and carcass characteristics were determined for S x S (n = 30), H x H (n = 26), H x S (n = 36), and S x H (n = 26) steers. In Phase I, S x S calves had heavier (P < .01) birth weights and heavier (P < .01) 205-d adjusted weaning weights than H x H calves. Birth weights of S x H calves were heavier (P < .01) than the mean of the purebred calves, but 205-d adjusted weaning weights did not differ (P > .10). In phase II, direct heterosis was 3.5% for birth weight (P < .05) and 5.1% for 205-d adjusted weaning weight (P < .01). Senepol maternal breed effects were 1.9 kg for birth weight (P < .10) and 37.9 kg for 205-d adjusted weaning weight (P < .01). Levels of direct heterosis, Senepol maternal breed effects, and Hereford direct breed effects were significant for most feedlot performance traits of steer calves that were fed to a common end point. Breeds did not differ (P > .10) for USDA yield and quality grades, and direct heterosis was not significant for Warner-Bratzler shear force. These results demonstrate significant levels of heterosis in preweaning performance between S x S and H x H calves and in feedlot performance of steers. Levels of heterosis were smaller and nonsignificant for most carcass traits including meat tenderness, which did not differ between S x S and H x H steers in this study.     

Norgestomet implants prevent pregnancy in beef heifers on pasture

The efficacy of erodible norgestomet implants for preventing pregnancy in postpubertal heifers was evaluated in two experiments at five locations each. Heifers (n = 896) within each study location were stratified by weight and allotted randomly to receive an ear implant containing either 0, 24, 36, or 48 mg of norgestomet (d 0). Heifers were exposed to fertile bulls immediately after implantation for 75 d (d 0 to 74) in Exp. 1 (n = 476) or for 80 d (d 75 to 154) in Exp. 2 (n = 420). Weights were recorded on d 0 and 74 (Exp. 1 and 2) and d 154 (Exp. 2). Each heifer was palpated rectally for pregnancy at the end of each experiment. Pregnancy rates were higher (P < .01) for control heifers (0 mg implant) than for heifers that received 24, 36, or 48 mg of norgestomet. In Exp. 1, pregnancy rates were 96, 29, 6, and 4% for heifers that received 0, 24, 36, and 48 mg implants of norgestomet, respectively. In Exp. 2, pregnancy rates were 85, 36, 19, and 9% for heifers that received 0, 24, 36, and 48 mg implants of norgestomet, respectively. Estrous activity during the first 3 wk of bull exposure was reduced (P < .05) among heifers that received norgestomet implants compared to control heifers but was not completely abolished at any dosage in Exp. 1. During the first 75 d of Exp. 1 and 2, heifers treated with 36 or 48 mg norgestomet implants gained weight faster (P < .05) than control heifers. Combined across both experiments, ADG during the first 74 d were .53, .56, .59, and .60 kg/d for heifers treated with 0, 24, 36, and 48 mg implants of norgestomet, respectively. These data indicate that norgestomet implants increased rate of weight gain, reduced estrous activity, and reduced the occurrence of pregnancy in heifers on pasture.