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There is a common misconception that internal IP networks (intranets) are secure and that only external networks such as the Internet and extranets are vulnerable and unsecured. The truth is that information on a network is not secure. With increases in network connectivity, the potential of bridging multiple networks on a single device, shared knowledge bases, and Web 2.0 integration of legacy applications, the problems are compounded. Traditional reliance on perimeter devices and security has proven to be ineffective in securing information in today's highly connected environments. This lack of security on increasingly powerful handheld devices, which tap into our information assets, will lead inevitably to increased exposure for our enterprise networks. The very nature of devices being networked makes them vulnerable on an IP network to various attacks and spoofs. This paper proposes a new model to identify and examine threats to information assets from private, Internet, and enterprise sources.

Reproductive, calf growth, and cow weight data were collected during a 16-yr period in southern Florida. Data included 1,767 calves at weaning from purebred, F1, backcross, F2, and three-breed crossbred cows of the Angus (A), Brahman (B), and Charolais (C) breeds. The purebred cows primarily produced purebred calves, the F1and F2Cows produced inter secrossbred calves, and the backcross cows produced 3/8:5/8 calves. The 1/2 C:1/4 A: 1/4 B three-breed crossbred cows were mated to A sires, whereas three-breed crossbred dams with breed compositions of 1/2 B:1/4 A: 1/4 C, and 1/2 A: 1/4 B:1/4 C were mated to C and B sires, respectively. For analysis of additive breed and heterosis effects, pregnancy rate and cow weight were considered to be traits of the dam alone. The A additive breed effect increased (P< .05) pregnancy rate but reduced (P< .001) cow weight. The effects of AB, AC, and BC heterozygosity all increased pregnancy rate, but the advantage was greater for the crosses that involved B. Both AB and BC heterozygosity increased (P< .001) cow weight, whereas AC did not. The additive direct effect of B and C increased birth weight (BWT) and weaning weight (WWT). The additive maternal effect of B reduced BWT. The direct effect of AB heterozygosity increased BWT and WWT, and that of BC increased only WWT (P< .001). A comparable pattern was observed for maternal heterosis on weight traits. A much smaller effect of AC maternal heterosis on WWT was found. Pregnancy rates of F1, backcross, and three-breed dams were similar. (ABSTRACT TRUNCATED AT 250 WORDS)

Genotype × environment interactions for postweaning performance traits of bulls produced by different lines of Hereford cattle were investigated in the contrasting environments of Miles City, Montana and Brooksville, Florida. During Phase 1 of the study (1966 to 1973), the performance of bull progeny from two unrelated lines (M1and F6previously developed in Montana and Florida, respectively) was compared at each of the two experimental sites. During Phase 2 (1967 to 1974), performance of bulls from two related lines (M1of Montana origin and F4derived from an M1foundation through selection in Florida) was compared at each of the two locations. The line × location interaction effect in Phase 1 was highly significant for weaning weights and average daily gain during the postweaning test, and for end-of-test weight, conformation score, condition score and forecannon circumference. The interaction effect in Phase 2 was highly significant for 205-d and end-of-test weights and significant for all other traits except end-of-test conformation score. These results, consistent with results for traits covered in other papers of the same series (reproductive traits, birth-to-weaning traits of bull and heifer calves combined, and postweaning traits of heifers), indicated the existence of economically important genotype × environment interactions in beef cattle. Results from the series of papers indicated that adaptation to local environment should receive consideration in planning breeding programs, performance tests and interregional transfers of beef cattle.

Angus (A), Brown Swiss (S) and A × S reciprocal F1(AS) dams were mated to A, S and AS (also reciprocal F1) sires resulting in nine breed groups of progeny with varying proportions of Angus and Brown Swiss breeding. Breed group of dam and of sire significantly influenced birth weight, preweaning daily gain, weaning weight, 205-d weight, condition score and frame size. The means for birth weight and weaning weight were 33 and 213 kg, respectively. Brown Swiss bulls sired calves with the heaviest birth and weaning weights. Calves produced by S dams likewise were heavier at birth and weaning. Pregnancy rates were influenced significantly by year, age and breed of dam and averaged 79, 95 and 92% for S, AS and A cows, respectively. Survival rate averaged 97% and was not influenced significantly by any of the effects examined. Because survival rates were similar for all breed groups, the results for weaning rate paralleled those for pregnancy rate. Genetic influences on preweaning growth traits and survival rate were partitioned into additive breed differences (B) and heterosis (H) effects for direct (d) and maternal (m) components. Pregnancy and weaning rates were examined using similar analyses except that genotype of service sire of dam replaced that of the offspring for the direct additive breed and direct heterosis components. The Bdvalues indicated that the Angus breed was inferior (P<.01) to the Brown Swiss breed for all preweaning growth traits except for condition score, in which the Angus breed surpassed (P<.01) the Brown Swiss. The Bmvalues also showed an advantage for the Brown Swiss breed for all preweaning growth traits. The additive maternal effect (the genotype of the females exposed), Bm, was important for pregnancy rate and weaning rate (P<.001 and P<.05) but not for survival rate (P>.10). The direct additive breed effect was not important for any reproductive trait. Direct heterosis did not affect any of the preweaning or reproduction traits; however, maternal heterosis (Hm) significantly affected all traits except birth weight, frame score and survival rate. The Hmestimates were 12.0 and 8.4 kg for weaning weight and 205-d weight, respectively. The Hmestimates for pregnancy rate, survival rate and weaning rate were 10, 2 and 13%, respectively.

Angus (A), Brahman (B) and Charolais (C) bulls were mated in all combinations to A, B, C, and reciprocal firstcross AB, AC and BC females in a 3 × 6 design. A total of 455 steer progeny and their carcasses were evaluated for additive breed and heterosis effects on individual and maternal influences. The traits measured were average daily gain (ADG), chilled carcass weight (CCW), thickness of fat over the rib eye (FOE), rib eye area/100 kg carcass weight (RER), Warner-Bratzler shear (WB) and USDA carcass quality grade (QG). The steer progeny were fed an average of 174 d from shortly after weaning until slaughter at an average age of 439 d. Mean values for the various traits were 976 g for ADG, 240.1 kg for CCW, .77 cm for FOE, 27.9 cm2for RER, 5.12 kg for WB and 14.5 for QG. The additive genetic effects for the Angus breed were positive for FOE (P<.05), RER and QG (P<.01) and nonsignificantly negative for ADG, CCW and WB. Brahman breed effects were positive for FOE (P<.01) and WB (P<.01) while negative for ADG (P<.01), CCW (P<.01), RER (P<.01) and QG. Additive effects for the Charolais breed were positive for ADG (P<.01), CCW (P<.01) and RER (P<.01) while being negative for FOE (P<.01), WB (P<.01) and QG (P<.05). Individual heterosis effects for reciprocal AB, AC and BC crosses, respectively, were 163 (P<.01), 36 and 91 (P<.01) g for ADG; 37.4 (P<.01), 16.0 (P<.01) and 24.5 (P<.01) kg for CCW; .18 (P<.01), −.07 and .01 cm for FOE; −1.46 (P<.05), .10 and −.63 for RER; −.69 (P<.05), .15 and −.08 kg for WB and .12, −.43 and .43 (P<.05) for QG. Additive maternal effects for Angus dams were nonsignificant for all traits. Effects for Brahman dams were significantly positive for RER and negative for ADG and FOE. The additive maternal effects for Charolais dams were significantly positive for FOE and negative for RER. Significant maternal heterosis effects were observed only for CCW and FOE (P<.01) for firstcross AB dams and for CCW (P<.05) in AC dams.

Breed and heterosis effects on reproductive performance were examined by the mating of Angus (A), Brahman (B) and Charolais (C) sires to A, B, C, AB, AC and BC dams, each sire mated to all dam groups. Reciprocals for each of the three F1groups of dams were combined. Contrasts between least-squares group means were used to evaluate breed of sire, breed group of dam and maternal heterosis effects on calving rate, calf survival and weaning rate. The most important influences on calving rate were breed of sire (90, 83 and 80% for B, C and A sires, respectively, P<.01) and class of dam (88 vs81% for crossbreds vspurebreds, P<.01). Breed of sire × breed group of dam interactions were negligible for this trait. The highest calving rate among dam groups was 92%, for reciprocal AB crossbreds; the lowest 82%, for A and AC dams. Survival rate of calves from A dams was 86%, compared with values of 92 to 96% for other breed groups of dams (P<.01). Calf survival rates were 94, 93 and 91% for A, B and C sires, respectively. The most important influence on weaning rate was breed group of dam. Means varied from 70% for A to 87% for AB dams. The mean weaning rate for F1dams was 82% vs75% for purebreds (P<.01). Among the crossbred cows, the two groups of B crosses, AB and CB (86%), excelled the AC crosses (76%) (P<.01).

Angus (A), Brahman (B), and Charolais (C) cattle were straightbred and reciprocally crossed in all possible 2-breed combinations. An average of 91 progeny were produced in each of the nine subclasses. The traits studied included weaning age, condition score, 205-day weight and weaning weight.Overall least squares means for calf age at weaning, condition score, 205-day weight and weaning weight were 222 days, 9.6, 194 kg and 207 kg, respectively.Breed of sire effects were significant (P<.01) for all traits. Weaning age was similar for calves sired by Angus and Charolais bulls (225 vs227 days) and lowest for those sired by Brahman (215 days). Condition scores were highest for calves sired by Angus (9.9) and Charolais (9.6) bulls and lowest for Brahman (9.4) sired calves. Average weaning and 205-day weights were highest for Charolais sires with calves by Brahman and Angus sires being similar. Breed of dam effects were significant (P<.01) for all traits except conditions score of calves. Angus dams weaned the oldest calves, 230 days, compared with 220 and 218 days respectively, for Charolais and Brahman dams. Weaning and 205-day calf weights were highest for Charolais dams with Brahman dams next in order and Angus dams lowest.Significant (P<.01) breed of sire × breed of dam interactions occurred for condition score, 205-day weight, and weaning weight of calves. Crossbred progeny excelled purebreds for all production traits (P<.01), averaging 9.8 vs9.2; 199 kg vs185 kg; 211 kg vs198 kg, respectively for condition score, 205-day weight, and weaning weight. Heterosis levels for reciprocal AB, BC and AC crossbred progeny, respectively, were 9.8, 5.5 and 5.3% for condition score; 13.1, 7.0 and 2.8% for 205-day weight; and 12.2, 7.1 and 2.1% for weaning weight.

Records on 3,327 matings, involving Angus (A), Brahman (B), Hereford (H) and all possible two-breed rotational crosses (AB, AH and BH), were analyzed to determine the effects of mating group (M), generation (G), sires within mating group and M × G interaction on pregnancy, survival and weaning rates. Three generations of rotational crosses along with contemporary straightbreds were included.Mating group affected pregnancy rate (P<.05) with group averages varying from 89.9% for the AH rotational crosses to 72.0% for the straightbred Brahmans. Generation was not a significant source of variation and interaction effects for M × G likewise were nonsignificant. Mean hybrid vigor levels for successive generations of crossbred dams were 6.0 (P<.05), 3.7 and 5.9%, respectively, for F1, backcross and 3/8–5/8 dams.Survival rate was affected by generation (P<.01), but effects for mating group and M × G interaction were nonsignificant. Survival rate increased in both straightbred and rotational crossbred groups over generations. This resulted in decreasing heterosis levels for this trait during successive generations, being 7.5 (P<.05), 2.4 and −.5%, respectively, for G1through G3.Weaning rate for all mating groups showed an increase during each successive generation except for the straightbred Brahmans and Brahman-Hereford crosses which had slightly lower weaning rates in G2than in G1and G3. Hybrid vigor for weaning rate averaged 13.6 (P<.01), 3.4 and 7.6% (P<05), respectively, for AB, AH and BH crosses. Heterosis levels were 14.0 (P<.01), 6.1 (P<05), and 4.6%, respectively, for G1, G2and G3. The M × G interaction was nonsignificant. This decline, as for survival, was due to straightbreds making more progress over generations than did the crossbreds.

Three successive generations of crossbreeding involving the Angus (A), Brahman (B) and Hereford (H) breeds in all possible two-breed-of-sire rotational crosses were evaluated in the Everglades of south Florida. Contemporary straightbred and crossbred progeny were produced each generation. The three successive generations of crossbred dams included first crosses (Fl), reciprocal first backcrosses (1/4-3/4 breed combinations) and reciprocal second backcrosses (3/8-5/8 combinations). The traits considered were birth weight, weaning condition score, weaning weight and the ratio of annual production to cow weight.Heterosis levels for the Brahman crosses (AB and BH) were highly signifiant and positive for all traits with values pooled over generations averaging 14.5% for birth weight, 10.5% for condition score, 17.5% for weaning weight and 24.5% for annual production/cow weight. Corresponding values for AH crosses were −3, 3 (P<.01), 5 (P<.01) and 5%, respectively.Heterosis levels, averaged over all crosses, for generations 1 through 3, were 7, 10 and 11%, respectively, for birth weight; 9, 5 and 10% for condition score; 15, 9 and 17% for weaning weight; and 28, 13 and 14% for annual production/cow weight.The two-breed rotations included in this study were effective in maintaining relatively high levels of heterosis for three generations. The average level of heterosis pooled over all crosses and generations was 18% (P<.01) for annual production/cow weight. The performance of each of the crossbred groups surpassed that of any of the straightbred groups by 3 to 50%.

Angus (A), Brahman (B), and Charolais (C) cattle were striaghtbred and reciprocally crossed in a study involving an average of 121 matings during 11 years for each of the nine possible combinations of the parent breeds. Overall least squares means for pregnancy rate, calf survival, and weaning rate were 78.6, 94.3 and 74.1%, respectively. Pregnancy rate was significantly influenced by breed of sire and was 74.4%, 82.3% and 79.1% for cows bred to Angus, Brahman and Charolais bulls, respectively. Effects due to breed of dam and sire × dam interactions were nonsignificant. Pregnancy rate for all cows crossbred (77.1%) was lower (P<.05) than for cows straightbred (81.5%).Calf survival was not significantly affected by breed of sire. However, breed of dam had a highly significant effect with Angus, Brahman and Charolais dams having calf survival rates of 88.7, 97.2 and 96.9%, respectively. The low calf survival rate for Angus dams was the result of a high death loss of F1progeny sired by Brahman (13%) and Charolais (13.5%) sires. Average survival rates for straightbred and F1calves were similar, 94.3 and 94.2%.Weaning percent was influenced (P<.05) by breed of dam and averaged 69.8, 76.5 and 75.9% for Angus, Brahman and Charolais cows, respectively. A highly significant sire × dam interaction resulted from Charolais sire × Angus dam matings having the lowest (63.8%) and Charolais sire × Brahman dam matings having the highest (82.2%) weaning rates. There was a nonsignificant advantage in weaning rate for straightbreds (76.9%) vscrossbreds (72.7%). Average weaning percentages for reciprocal combinations were 70.0% for AB + BA, 67.7%for AC + CA, and 80.2% for BC + CB (P<.05). Heterosis levels for pregnancy, calf survival and weaning rates were negative for the AC and AB reciprocals while for the CB combinations they were −2.1% for pregnancy rate but 4.0% for calf survival and 2.0% for weaning rate. These data indicate that mating of cows of the smaller breeds with sires of the large breeds may result in a net decrease for weaning rate

Mature Angus cows and yearling Angus heifers were used during a 3-year period to compare the performance of animals wintered (December to March) with supplements of (1) cottonseed meal cubes (CSM) containing 41% crude protein, (2) citrus pulp cubes with feed-grade biuret (CPB) containing 38% crude protein or (3) citrus pulp cubes without biuret (CP) containing 7% crude protein. The supplements were provided three times weekly at rates of 2.0 lb (.9 kg), 2.2 lb (1.0 kg) and 1.9 lb (.86 kg) per head daily, respectively. All animals remained on Argentine bahiagrass (Paspalum notatum) pasture, and Pangola digitgrass (Digitaria decumbens) hay was provided as the main supplemental energy feed during the winter. Cattle were randomly assigned to treatments in August of each year. For the 3-year period, mature cows receiving CSM cubes lost 108 lb (49 kg), those receiving CPB cubes lost 132 lb (60 kg) and those receiving CP cubes lost 154 lb (70 kg) per cow during the winter period. All values differed significantly (P<.01). Winter weight gain by heifers was not affected (P>.05) by treatment during the first year, but during the second year, heifers receiving CP cubes gained more weight. Conception rate, calf survival and time required to reconceive was not influenced by wintering treatment. Cows receiving CPB cubes weaned lighter weight (P<.01) calves, 356 lb (162 kg) than did cows receiving CP cubes 365 lb (166 kg) or CSM cubes 367 lb (167 kg).

Heterosis levels were estimated for the progeny of F1and F2crossbred sires representing all two-breed combinations of the Brahman, Angus and Charolais breeds. Crossbred sires were mated to purebred dams to produce backcross and three-breed cross calves and to F1dams to produce F2 progeny. Contemporary purebred controls were produced annually. The data from progeny of F1 and F2sires were similar, thus, they were combined to simplify presentation. Mean heterosis levels for backcross calves sired by crossbred bulls were 1.9, 2.1 and 2.9%, respectively, for weaning weight, 205-d weight and condition score. Mating crossbred bulls to females of a third breed resulted in heterosis levels of 5.5, 7.3 and 5.1%, respectively, for weaning weight, 205-d weight and condition score, which were similar to those observed for F1calves during the two previous phases of the study. Among the different three-breed combinations, only calves sired by Angus × Charolais crossbred sires mated to Brahman dams showed significant levels of heterosis for weaning or 205-d weights. Heterosis levels for inter se crossbred calves were 13.7, 11.6 and 9.7%, respectively, for weaning weight, 205-d weight and condition score. These values were similar to those observed during an earlier phase of this study for F1cows nursing backcross calves and indicate that crossbred sires potentially may be useful in commercial crossbreeding programs.

The postweaning performance of heifers from contrasting lines of Hereford cattle was compared simultaneously at Miles City, Montana and at Brooksville, Florida in an experiment designed to evaluate the importance of genotype × environment interactions in beef cattle. During Phase 1 of the study (1964 to 1973), the performance of two unrelated lines, M1and F6, was compared at the two locations. During Phase 2 (1967 to 1974), two related lines, M1 of Montana origin and F4derived from M1by selection in Florida, were compared at each of the two locations. The line × location interaction term was highly significant in either Phase 1, Phase 2 or both for weaning weight, daily gain from weaning to spring, spring yearling weight, daily gain from weaning to fall, fall yearling weight, yearling condition score, conformation score, wither height, body depth, body length, shoulder width, hook width and forecannon circumference. Daily gain of yearlings from spring to fall was the only objective measurement for which the interaction term was nonsignificant in both phases. These results, consistent with the results on performance to weaning age reported previously, indicate the existence of highly significant genotype × environment interactions in beef cattle. The results indicate that genetic adaptation to the local environment is important in beef cattle production and should be considered in designing breeding programs or performance testing procedures and in interregional transfer of breeding stock.

Breed and heterosis effects for maternal and calf components for weaning traits were measured in the progeny of Angus (A), Brahman (B) and Charolais (C) sires mated to A, B, C and reciprocal AB, AC and BC dams. Additive breed effects for the calf component for weaning weight were −3.0 ± 3.2, −26.6 ± 3.1 and 29.6 ± 3.3 kg for A, B and C, respectively. Corresponding maternal breed effects were −1.7 ± 2.4, 7.8 ± 2.3 and −6.1 ± 2.6 kilograms. Heterosis effects on weaning weight for the calf component were 21.2 ± 3.6 for AB, 1.4 ± 3.7 for AC and 16.5 ± 3.4 for BC crosses, while heterosis levels for the maternal component were 28.9 ± 2.7 for AB, 16.5 ± 3.2 for AC and 18.7 ± 2.9 kg for BC dams. The corresponding estimates for condition scores tended to parallel those for weaning weight. Approximate relative production efficiency rates were computed for the different mating groups as (calf weight + cow weight) × weaning rate. These values were .34 for purebred matings, .36 for purebred dams raising F1calves, .40 for F1cows raising back-cross calves and .43 for F1dams raising three-breed crossbred calves.

The effects of Brahman, Brangus, Beef-master, Limousin, Simmental and Maine-Anjou sires when mated to Angus, Brangus and Hereford females were studied on calf crops from 1972 to 1976. Preweaning data were available on 755 observations and feedlot and carcass data were available on 207 steers.Preweaning traits studied were birth weight, 205-day weight, type and condition score. Birth weight, 205-day weight, type and condition score were influenced (P<.01) by breed of sire and breed of dam. Breed of sire × breed of dam interaction affects were significant for 205-day weight. Calves by Brahman sires were heaviest at birth (34.2 kg) with Brangus sired calves the lightest (29.2 kg). The 205-weight was heaviest for Maine-Anjou sired calves (218.1 kg) and lightest for Brangus sired calves (202.2 kg). Brangus dams produced calves that were heavier at birth and weaning than did Angus and Hereford dams.Feedlot and carcass data from steers fed on a time-constant basis indicated that initial weight, final weight and ribeye area were affected by breed of sire and breed of dam (P<.01). Feed-lot average daily gain, fat thickness and yield grade were influenced by breed of sire (P<.01). Breed of dam affected marbling, fat thickness, quality grade and yield grade (P<.05). The breed of sire × breed of dam interactions influenced longissimusmuscle area (P<.01) and initial and final weight (P<.05).

The birth and weaning performance of different lines of Hereford cattle were compared in the dissimilar climates of Brooksville, FL, and Miles City, MT, from 1961 through 1975. During phase 1 of the study, two unrelated lines (F6and M1) previously developed at the two respective stations were compared over an 11-year period following a reciprocal exchange of cattle. Concurrently, a Florida derivative of M1cattle (F4) was selected for performance in Florida; thus, a later comparison of related lines (F4and M1) developed at the two locations (phase 2 of the study) was made possible. Traits of primary interest included birth weight, daily gain from birth to weaning, estimated 205-day weight, body length, condition score and annual production per cow.Location effects differed with lines. In the Montana origin lines (M1and F4), there was a significant advantage for the Montana location for all traits except condition score which was identical at the two locations. In line F6there was a slight advantage for the Florida location for all traits except birth weight which was 5.2 kg heavier in Montana.Line by location interactions were highly significant for all traits during both phases of the study. When results over the two phases were pooled, advantages for the local over introduced groups were 1.2 kg for birth weight, 58 g for daily gain, 13 kg for 205-day weight, 2.1 cm for body length, .5 units for condition score and 24.8 kg for annual production per cow. These results agree with previous indications from this study that genetic adaptation to the local environment is important in commercial beef cattle production and merits serious consideration in performance testing procedures, interregional exchange of seedstock and sources of semen used for artificial insemination.

Genotype by environment interactions involving the reproductive performance of different lines of Hereford cattle in the contrasting environments of Brooksville, FL and Miles City, MT, were studied in a cooperative, interregional project from 1961 through 1974. During phase 1 of the study, performance of two unrelated lines (M1and F6), previously developed at the two stations, were compared at each of the two locations. Simultaneously, a derivative of M1cattle (F4) was selected for performance in Florida. Reproductive performance of these related lines (M1and F4) were compared at each of the two locations during phase 2 of the study.Line by location interaction effects were highly significant for pregnancy and weaning rates during both phases of the study. In phase 1, the advantage of the local over the introduced lines was 6.7 (P<.01) for pregnancy percentage and 6.1 (P<.01) for weaning percentage. Corresponding values for phase 2 were 11.6 (P<.01) and 12.5 (P<.01), respectively. These results suggest that genetic adapation to the local environment is important in beef cattle production and should be considered in designing commercial breeding programs.

Angus (A), Brahman (B) and Charolais (C) sires were mated in all combinations to dams of the same breeds in a 3 × 3 design. A total of 351 steer carcasses from the nine breed subclasses were evaluated to estimate average breed, maternal and heterosis effects on chilled carcass weight (CWT), thickness of fat over the longissimusmuscle (FOE), ribeye area per 100 kg of carcass weight (REA), estimated retail yield (RY) and USDA carcass quality grade (QG). The steers were full-fed an average of 176 days from shortly following weaning to slaughter at an average age of 440 days.Mean values for the various traits were 2 36.9 kg for CWT, .74 cm for FOE, 27.9 cm2for REA, 50.9% for RY and 14.5 for QG. Heterosis, in units, for the various traits for the reciprocal AB, AC and BC crosses, respectively, were 39.1 (P<.01), 13.4 (P<.01) and 23.6 (P<.01)kgfor CWT; .18 (P<.01), .01 and .06 cm for FOE; −1.81 (P<.01), −1.01 (P<.05) and −1.33 (P<.01) cm2/100 kg for REA;−.55 (P<.01),−.30 and −.39 (P<.05) percentage for RY and .09, −.14 and .48 (P<.05) for QG.Direct effects of Angus breeding were positive for QG, FOE and REA and negative for CWT. Effects of Brahman breeding were negative for REA, RY and QG. The direct effects of Charolais breeding were positive for CWT and Y, but negative for FOE and QG.Angus dams had a positive effect on FOE and QG but a negative influence on RY. Brahman dams had a positive effect on RY and REA but negative effect on FOE and QG. Charolais dams had a positive effect on CWT but negative effect on REA and RY.

Records of birth weight (BW), weaning weight (WW) and condition score (CS) from 1,467 Brahman and Brahman × Angus crossbred calves from Brahman and crossbred Brahman sires and Brahman, crossbred Brahman and Angus dams were collected at the Subtropical Agricultural Research Station, Brooksville, Florida, from 1971 to 1982. Best linear unbiased estimates (BLUE) of Brahman sire and dam group additive genetic effects (as deviations from Angus) and Brahman × Angus dam and calf group nonadditive (intralocus) genetic effects (as deviations from intralocus group genetic effects in the parental breeds) were obtained. Linear combinations of these were used to compute direct and maternal Brahman additive and Brahman × Angus nonadditive (intralocus) group genetic effects. The respective BLUE of these four effects were 5.99±2.08, -5.70±1.91,. 52±1.81 and 2.85±.72 kg for BW;9.60±10.29, 8.76±9.47, 9.47 ± 8.96 and 20.95±3.56 kg for WW; and -1.10±.55, 1.64±.50, 1.47±.47 and .05±.19 units for CS. Linear combinations of the BLUE of sire, dam and calf group genetic effects can be used to predict the genetic worth of crossbred groups composed of any combination of Brahman and Angus breeding. Nonadditive maternal group genetic effects were the most important factor for BW and WW, whereas nonadditive direct group genetic effects were the most important for CS.

Pregnancy rate, calf survival rate to weaning and calf age at weaning of several types of crossbred cows (2/3 or more Brahman) were compared to those of straightbred Brahman and Angus cows over a 12-yr period at Subtropical Agricultural Research Station near Brooksville, FL. The purpose of this study was to determine the relative importance of additive vs nonadditive genetic effects on reproductive and calf survival traits in a population of cattle whose foundation was selected on the basis of superior reproductive performance under harsh environmental conditions. Best linear unbiased estimates (BLUE) of direct additive effect (measured as the deviation of Brahman additive breed effect from Angus) for pregnancy rate and calf age, measured as traits of the dam, were 6 ± 3% and -7.2 ± 2.1 d, respectively. Thus, Bos taurusgerm plasm did not increase pregnancy rate but resulted in an earlier calving date. The BLUE of nonadditive (intralocus) direct genetic effects measured as deviations from intralocus group genetic effects in the parental breeds on pregnancy rate and calf age at weaning were 25 ± 4% and -6.4 ± 2.5 d. Nonadditive effects on pregnancy rate were the primary cause of the superior reproductive rates observed in Brahman crossbred cows. Calf survival was considered to be a trait of the calf, and BLUE of direct additive, direct nonadditive, maternal additive and maternal nonadditive genetic effects were obtained. Only maternal nonadditive genetic effects were found to have a significant effect on survival rate (9 ± 4%).

Anderson (1944) reported an average estrous cycle length of 22 and 23 days, respectively, for European x Zebu and purebred Zebu cattle. The average duration of estrus was 7.4 and 4.8 hr., respectively. Other workers (Clamohoy, 1952; Rollinson, 1955; Villacorta, 1960) using small numbers of Zebu cattle found estrus to be longer than that reported by Anderson (1944) but shorter than that given in the literature for Bos tauruscattle in the temperate zone. A seasonal influence on reproductive performance was reported by Wilson (1946). The highest frequency of conception for 17,000 Zebu cows with year-round breeding in Nyassaland was found to be during the hottest months of October and November. Seasonal variations in lengths of estrus and the estrous cycle were observed by Hammond (1927) and Anderson (1944).The purpose of the present study was to determine length and regularity of the estrous cycle, duration of estrus and time of ovulation in relation to season as well as to obtain data on fertilization rate and embryo survival in grade Brahman heifers.

A study of the effects of age at castration on feedlot performance and various carcass criteria of bulls and steers has shown a need to re-evaluate current carcass evaluation and grading methods if young bulls are to be used as a red meat source. Bulls gained faster and more efficiently than all castrate groups. Differences in slaughter characteristics were small except in dressing percent where bulls were superior. The castrate groups graded higher than bulls due mainly to superior marbling scores. Bulls yielded approximately 4 percentage points more trimmed, boneless retail cuts. An increasing trend toward a higher yield of trimmed, boneless retail cuts was noted with each increase in castration age. The U.S.D.A. formula for trimmed, boneless retail cuts underestimated true yield of bull carcasses by approximately 2 percentage points. No differences were found in either Warner-Bratzler shear or taste panel data for tenderness among groups. Differences in carcass characteristics and feedlot performance attributable to castration age were small and, in most instances, nonsignificant.

Age and weight at puberty and correlated response in reproductive performance were determined for two lines of mice (L1 and L2) selected for individual 42-day weight. L1 was maintained on a high-energy diet (D1) and L2 on a low-energy diet (D2). Mice from each of the two lines were also maintained on the opposite diet. The L1/D1, L1/D2, L2/D1 and L2/D2 respective subgroup means for age at puberty (days) were 30.8, 38.4, 29.0 and 36.2 and weight at puberty (g) were 20.9, 18.5, 19.2 and 17.7. Pooled heritability estimates of age and weight at puberty were respectively 0.43 and 0.33. Linear regressions of age on weight at puberty were 0.49 (L1/D1), 0.69 (L1/D2), 0.29 (L2/D1) and 0.57 (L2/D2). Age at puberty was negatively correlated with first litter size (−.11), first litter birth weight (−.25) and number of embryos, second litter (−.35). Weight at puberty was positively correlated with first litter size (0.24), first litter birth weight (0.27) and number of embryos, second litter (0.38).

Two herds of Hereford cows, one originating at the U.S. Range Livestock Experiment Station, Miles City, Montana, and the other originating at the Brooksville Beef Cattle Research Station, Brooksville, Florida, were subdivided and half of each transferred to the opposite location. During the first 7 years (1962 through 1968) subsequent to the initial transfer, location-origin interactions were apparent in birth, weaning and yearling weights (P<.01) for both sexes. Performance to yearling ages favored Montana-originating cattle at the Montana location and cattle of Florida origin at the Florida location. Interactions were not apparent in traits of 5-year-old cows, with the exception of reproductive performance. Percent pregnant and percent weaned were lower for the cows of Montana origin located in Florida than for the other three location-origin subgroups, which were similar. Significant differences in most traits measured were observed between locations and between origin groups.

Using 72 weanling pigs fed in drylot, an experiment has been conducted to study the feeding value of two low gossypol cottonseed meals as compared to a good quality soybean oil meal. It was also possible to compare the growth stimulating value of procaine penicillin with a combination of procaine penicillin and erythromycin.The results conclusively demonstrated that a degossypolized solvent extracted cottonseed meal (free gossypol content of 0.01% and nitrogen solubility 89.0%) was superior to an expeller cottonseed meal (free gossypol content of 0.01%, and nitrogen solubility of 42.2%). When either of the cottonseed meals was partially replaced (25, SO or 75%) with soybean oil meal the gains were significantly improved. In the case of the degossypolized solvent cottonseed meal it was observed that the combinations were equal or superior to soybean oil meal only.The feeding of erythromycin in combination with procaine penicillin as an antibiotic fortification produced faster gains with all nine rations than did the feeding of procaine penicillin alone.The results of this study indicate that low gossypol cottonseed meal can be used to good advantage as a protein supplement for weanling pigs, either as the sole source of supplementary protein or in combination with soybean oil meal. The most efficient rations in this study were those containing mixtures of the degossypolized solvent meal and soybean oil meal.

Two hundred and twenty pigs weaned at 9 to 11 days of age were used to evaluate the effects of supplementing various type rations with digestive enzymes. Sugar and/or corn were used in conjunction with combinations of dried skim milk, soybean meal, poultry meal and feather meal to form the major constituents in all rations.There were no statistically significant differences in average daily gain between the control groups and the groups supplemented singly with diastase, pepsin and pancreatin or with various combinations of these enzymes; a similar situation existed when Ethmoid C/15 or sucrase was combined with these enzymes. The differences in gain, while small, were consistently in favor of the enzyme supplemented groups.Feed efficiency was significantly improved (P<.05) for a 21-day period by the addition of pepsin, pancreatin and a combination of the two with and without sucrase to a ration composed essentially of sugar, corn, soybean meal and feather meal. Although in general the differences between the control and treated groups were not statistically significant, feed efficiency in most instances was improved by enzyme supplementation.The performance of pigs fed enzyme supplemented rations for 21 days was similar to that of pigs supplemented over a 49-day period.Pigs fed rations containing a dried skim milk-soybean meal combination gained significantly faster (P<.05) than those receiving a mixture of feather meal and soybean meal.

For a number of years research workers have been conducting investigations in search of anatomical, physiological or chemical factors which could be used to differentiate between dwarf-carrier and non-carrier cattle. To aid in this search investigations were undertaken on certain blood constitutents of non-carrier cattle and of carriers of the gene for dwarfism described by Johnson et al. (1950).The literature reveals only limited information on the blood constituents of dwarfs and dwarf-carrier animals as compared with those of noncarrier animals. Studies by Fransen and Andrews (1954), Andrews et al. (1956) and Cornelius et al. (1956) indicated that the formed elements of the blood were similar in dwarf and normal cattle. Foley et al. (1956) reported cell counts and blood sugar levels were similar in dwarf-free and carrier cattle, but that changes due to insulin shock were different in the two genotypes.A study by Leuchtenberger et al. (1956) showed that the desoxyribonucleic acid (DNA) content of individual spermatogeuic cells from one dwarf and two suspected carriers was markedly deficient as compared with corresponding cells of normal bulls.

The phosphatase activity of 321 pigs was determined when they were 1 and 7 days of age. Both birth weight and phosphatase activities were correlated with weaning weight at 56 days. A significant, but small, correlation coefficient (r=0.31) was found between birth weight and weaning weight. Male pigs weighed significantly more than female pigs at birth, but there were no significant sex differences in 56-day weaning weights.Phosphatase activity at either 1 or 7 days of age was not significantly correlated with weaning weight. At 1 day of age female pigs exhibited a significantly higher phosphatase activity than male pigs. No sex differences were found in the 7th day determinations.A significant difference among breeds was found with all criteria studied.

The number of calves weaned relative to the number of cows exposed to bulls is one of the most important economic traits in beef cattle production. High costs of production make it of the utmost importance to achieve the highest weaning rate possible with the forage resources available. Thus, it is important to assess the productivity of various breed groups in alternative production systems in order to design economical production programs. Little information is available on the comparative reproductive behavior of Brahman, European-origin and crossbred cattle under contolled environmental conditions imposed by nutritional or management regimes.At the time the trial was initiated, information was not available on the comparative reproductive performance of different breed groups. Reliable data on the reproductive rates on native versusimproved pastures in Florida were unavailable. Reports from Florida (Koger et al., 1962; Gonzales-Padilla et al., 1969), Texas (Cartwright et al., 1964) and Louisiana (Turner, Farthing and Robertson, 1968) have indicated heterosis for weaning rate in Brahman-British crossbred cows.

Records were obtained on 3,938 Brahman calves from four ranches with limited breeding seasons in Florida to evaluate reproductive performance of their dams. The adjusted mean for 2,924 calving intervals was 409.9±2.2 days, and the effect of the dam's age when her first calf was born, the dam's age at calving, sex of the calf and location were highly significant (P<.01). The location x age at calving interaction was significant (P<.05). The repeatability of 2,778 calving intervals of 613 cows was 0.08.When long intervals, resulting from the cow's failure to calve in consecutive years, were excluded the adjusted mean for 2,527 intervals was 374.7±1.0 days with highly significant differences due to age at calving and location. The location x age at calving interaction was also highly significant. The repeatability of 2,346 intervals of 566 cows was 0.03.Location differences appeared to be due to differences in the length of the breeding season. Age differences were caused by the tendency of the intervals between calvings in consecutive years to shorten with increasing age of the cow. Four- to 5-yr.-old cows were more likely to fail calving than older cows.The interval from exposure to conception was greater the longer the breeding season lasted. Heifers conceived 64.5±1.7 days after first exposure to a bull, while cows which had calved at least 1 month before the breeding season started conceived after 45.5±1.1 days, the difference being highly significant (P<.01).The mean interval from parturition to conception was 65.3±1.3 days for 911 calvings which took place during the breeding season. There was a highly significant (P<.01) difference between the four herds, and seemed to be related to the length of the breeding season.The results suggest that selection for reproductive performance during a short breeding season will decrease the average calving interval, and thus increase overall reproductive efficiency.

Dates of breeding and birth dates of Brahman calves were obtained from two ranches in south Florida. The length of 1323 gestation periods was calculated. Errors due to the nature of this field study are discussed. The mean gestation length of 1048 gestation periods which were between 271 and 310 days was 292.8 days.The frequency distribution for the length of gestation periods is reported as well as the results of a variance analysis for location, sire and sex effects. While there was no difference between locations, sex and sire differences contributed significantly to the total variance, showing that the genotype of the calf affects the length of time it is carried in utero. The results are discussed in relation to the literature for Bos indicusand Bos tauruscattle.

The ovaries of 252 Brahman heifers and 60 Brahman crossbred heifers at three ranches in North Central and South Florida were palpated at monthly intervals for different periods of time. The heifers came from well-managed herds with better than average nutritional levels. Puberty was determined by occurrence of the first corpus luteum. The average age of puberty for 83 Brahman heifers with complete data was 19.4 mo., with a range of 14 to 24 mo. Incomplete data from additional 41 heifers suggested that puberty occurred in some Brahman females as late as 26 mo. of age and earlier than 14 mo. The average age of puberty in 17 Brahman-Shorthorn heifers was 17 mo. with a range of 15 to 20 mo. In 5 crossbred heifers with incomplete data, puberty occurred earlier than 7 to 13 mo. of age.There was no significant difference in age at puberty due to season of birth or ranch location. There was a correlation between 205-day weaning weight and age of puberty of −.46 (P<.01) and −.41 (P<.05) for the Brahman and crossbreds, respectively.Brahman heifers exhibited a definite seasonal variation in sexual activity as measured by frequency of corpora lutea, and by size and tonus of the uterus. Sexual activity increased during the spring and was highest in the summer. After a low incidence of corpora lutea during the winter, it increased again during the second spring, especially following exposure to bulls. Seasonal fluctuation in frequency of corpora lutea did not occur in Brahman-British heifers. The crossbreds had a higher frequency of ovulation than Brahman females throughout the year. It is suggested that temperature, nutrition or the presence of bulls influences the levels and balance of the endocrine system, resulting in seasonal variation in sexual activity in Brahman heifers.

Loin steaks, rib roasts, kidney and livers from papain-injected cattle were significantly more tender than those from noninjected control cattle. A marked difference in tenderness was found between breed groups. In general, Angus and Angus × Hereford cattle were more tender than other breed groups while Brahman were the least tender. A significant interaction was found between breed group and papain injection, indicating a differential response by breeds to papain injection.Steaks and roasts from full-fed steers were more tender than those from equalized-fed steers. The effect of level of feeding on tenderness was more pronounced in some breed groups than others as indicated by a significant breed group × feed level interaction.