Search

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)

Pastures of Sarasota stargrass, Callie Bermuda grass and Bigalta limpograss were evaluated in comparison with the currently recommended forage cultivar in South Florida, Ona stargrass, by year-long grazing with yearling steers. Pastures, 2 ha in size, were divided into four .5 ha units and rotationally grazed at initial stocking rates of five 200 kg steers/2-ha pasture. A “put-and-take” stocking system was used to adjust animal numbers beyond the initial stocking rate to maintain relatively uniform levels of standing forage. Differences in individual animal performance were not obtained among grasses over a 3-yr period. However, carrying capacity during the warm season differed (P<.01) with 975, 969, 829 and 739 animal days of grazing for Sarasota, Ona, Callie and Bigalta, respectively, during this 230-d period. Beef production of 619, 607, 513 and 532 kg/ha on pastures of Sarasota, Ona, Callie and Bigalta, respectively, differed only at the P=.18 level, but this is probably of economic importance. Average daily gain was closely correlated (r=.419 for Bigalta to r=.577 for Ona with P<.0001 for each of the four grasses) with forage in vitro organic matter digestibility (IVOMD). However, equations involving forage IVOMD and forage quantity did not account for much more of the variation in animal performance than did IVOMD alone.

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.

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

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.

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.

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.

Mai (1964) considered that there were less than 100 nematode diseases of serious proportions, but many more causing less obvious or severe damage were still unrecognized. A rather general account is here given of the role of nematodes in plant disease, using as examples nematodes and crops of economic importance–-including cyst-forming, root-knot, burrowing and reniform nematodes on crops such as potatoes, sugar beet, temperate cereals, citrus, bananas, cotton and soya beans.

Variations in the times to reach steam temperature by surgeons' gowns within a steam steriliser with air elimination by downward displacement and evacuation have been examined. Using surgeons' gowns equilibrated with normal atmospheric conditions, about 60 to 70 per cent relative humidity, the times taken for the gowns to attain steam temperature were variable, whichever method of air removal was employed. Gowns dried at 50° rapidly attained steam temperature and then superheated to a considerable degree. The superheat was maintained for long periods.

The rapid cooling of bottles in an autoclave after steam sterilisation has been investigated. A coarse cold water spray caused breakage by thermal shock, whereas a fine spray prevented this. The time of cooling using this method has been compared with the usual cooling cycle and with that achieved when air was circulated in the chamber. Experimental data for a steriliser containing a charge of 200 × 1 litre bottles is given.

A modified sterilising cycle has been evolved after studying the temperature distribution and effects of moisture in fabrics in the pre-sterilisation phase. A vacuum of 20 mm. Hg abs. followed by the introduction of steam to raise the pressure to about 200 mm. abs. and then re-applying a vacuum of 20 mm. Hg abs. was found to produce the required conditions to give even heating throughout the materials.

Six lots of 12 steer calves each were fed a basal ration of cottonseed hulls, cottonseed meal, citrus pulp and mineral mixture during a 140-day depletion period. Daily additions per calf to the basal ration during a 56-day supplemental period were: Lot 1, control; Lot 2, 0.23 kg hay; Lot 3, 0.91 kg hay; Lot 4, 0.23 kg hay+12,000 IU vitamin A; Lot 5, 0.91 kg hay+48,000 IU vitamin A; and Lot 6, 12,000 IU vitamin A. Rations were palatable as shown by the 2.5 kg to 2.8 kg eaten daily per 100 kg body weight. There was no significant difference in daily gain by the six treatments of 12 calves during either the depletion or supplemental periods.Vitamin A per gram fresh liver was reduced (P<.01) from 106 µg intially to 9 µg after 140 days on the basal ration. Livers from Lot 5 during the supplemental period increased (P<.01) from 6 µg to 17 µg per g, the same level as at the 84th day of depletion period. There was a small decrease in level of liver vitamin A in Lots 1, 2, 3 and 4 during the supplemental period with Lot 6 at the same level at end of both periods. Carotene level decreased (P<.01) from 15 µg per g of liver initially to 5 µg after 140 days on basal ration with little change during supplemental period for any lot. Basal ration+combination of hay and vitamin A or vitamin A alone increased (P<.01) plasma level of vitamin A. Calves fed the highest level of both hay and vitamin A had the lowest level of plasma carotene.