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Milk yield and quality were observed on 93 Angus, Brahman, and reciprocal-cross cows over 3 yr to evaluate the interactions of direct and maternal breed effects and heterosis with forage environment. Forage environments were common bermudagrass (BG), endophyte-infected tall fescue (E+), and a rotational system (ROT) of both forages, in which each forage (BG or E+) was grazed during its appropriate season, usually June through October for BG and November through May for E+. Milk yield was estimated each of 6 mo (April through September) via milking machine and converted to a 24-h basis. Milk fat, milk protein, and somatic cell count were analyzed by a commercial laboratory. Heterosis for milk yield was similar among forages, averaging 2.4 kg (P< 0.01). Expressed as percentages of purebred means, heterosis for milk yield was largest on E+ (52.8%), intermediate on ROT (39.3%), and smallest on BG (23.7%). Direct breed effects for milk yield favored Brahman, and they were similar among forages but tended to be larger for E+ (2.5 kg) and ROT (2.8 kg) than for BG (1.3 kg). Direct breed effects for milk fat favored Brahman and were similar among forages but tended to be larger for E+ (1.0%) and ROT (1.0%) than for BG (0.6%). Purebred cows exceeded crossbreds in milk protein by 0.1% on ROT (P< 0.10). Crossbred cows had lower somatic cell counts than purebreds on BG (P< 0.05), E+ (P< 0.01), or ROT (P> 0.30). Heterosis for somatic cell counts as percentages of purebred means was similar for BG (−68.3%) and E+ (−68.9%) and less favorable for ROT (−31.6%). Maternal breed effects for somatic cell count favored Angus on ROT (P< 0.10) with a similar nonsignificant trend on BG and E+. Direct breed effects for somatic cell count favored Brahman on ROT (P< 0.10) with similar nonsignificant trends on BG and E+. These results suggested that a rotation of cows from E+ to BG in the summer can partially alleviate negative effects of E+ on milk yield. Conclusions also indicated an advantage to crossbred cows in somatic cell count and provided evidence of both direct and maternal breed effects for this trait. The results also suggested that direct breed effects for milk yield, milk fat, and somatic cell count and heterosis for milk yield and somatic cell count (as percentages of purebred means) tended to vary with forage environment, indicating a potential for genotype × environment interaction for these traits.

Data from 403 calves from Angus, Brahman, and reciprocal-cross cows sired by Polled Hereford bulls were used to evaluate the impact of postweaning backgrounding forages on postweaning BW, gains, and carcass traits. Calves were born (spring of 1991 through 1994) and reared on either endophyte-infected tall fescue or common bermudagrass pastures. After weaning, calves were transported 360 km to the Grazinglands Research Laboratory, west of El Reno, OK, and, within breed and preweaning forage, were assigned to one of the following winter stocker treatments: 1) winter wheat pasture or 2) dormant native prairie plus supplemental CP. In March, winter stocker treatments were ended and calves were grazed as a single group on cool-season grasses until early July (1992, 1993, and 1994) or late May (1995), when the feedlot phase began. In the feedlot, calves were fed a high concentrate diet for an average of 120 d until a backfat thickness of > 10 mm was reached. Calves were shipped in truck load lots to Amarillo, TX (350 km), for processing and collection of carcass data. Averaged over calf breed group, calves wintered on wheat pasture gained faster (P< 0.01) during the stocker phase (0.71 vs 0.43 kg); had heavier (P< 0.01) final feedlot weights (535 vs 512 kg); lower feedlot (P< 0.01) ADG (1.37 vs 1.53 kg); heavier (P< 0.01) carcass weights (337 vs 315 kg); larger (P< 0.01) longissimus muscle (84.9 vs 81.8 cm2); higher percentage (P< 0.01) of kidney, heart, and pelvic fat (2.32 vs 2.26); and higher (P< 0.01) dressing percentage (62.2 vs 61.3) than calves backgrounded on native prairie. Maternal heterosis for stocker ADG was evident in calves backgrounded on native prairie but not on winter wheat (P< 0.10), but the two environments were similar in maternal heterosis for feedlot ADG and carcass traits. Calves wintered on native prairie were restricted in growth and expressed compensatory gain during the feedlot phase but not during the spring stocker phase. Dormant native grasses can be used to winter stocker calves excess to the winter wheat pasture needs, but ownership of these calves would have to be retained through the feedlot phase to realize any advantage of built-in compensatory gain. Finally, these data suggest that expression of maternal heterosis for weight gain is more likely in calves backgrounded on native prairie than in calves grazed on winter wheat.

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

Reproductive and preweaning data on 190 Angus (A × A), Brahman (B × B), and reciprocal-cross cows (A × B and B × A) and 434 two- and three-breed-cross calves managed on common bermudagrass (BG), endophyte-infected tall fescue (E+), or a combination of both forages (ROT) were used to evaluate the interaction of forage type with individual and maternal heterosis and maternal and grandmaternal breed effects. Cows were born from 1988 to 1991, and calves sired by 13 Polled Hereford bulls were born from 1995 to 1997. Heterosis for calving rate was larger on E+ than on BG or ROT (P< .05), whereas maternal effects were larger on BG than on ROT (P< .10). Maternal heterosis for birth weight was negative on BG (P< .11) but positive on E+ and ROT (P< .10). Grandmaternal effects were evident on BG (P< .10) and E+ (P< .01) but not on ROT. Forage effects were generally substantial for 205-d weight, calf weaning hip height, and calf weaning weight:height ratio; BG was highest, ROT was intermediate, and E+ was lowest. Maternal heterosis for these traits was generally greater on E+ than on BG (P< .10). Grandmaternal effects for 205-d weight, hip height, and weight:height ratio were not important on any forage. Heterosis for weaning weight per cow exposed was substantial on all forages (P< .01) and was significantly greater on E+ (P< .01) than on BG or ROT, but maternal effects were not significant. Thus, we observed more advantage to Brahman-cross cows over purebreds on E+ than on BG. We also observed that moving cows and calves from E+ to BG in the summer will alleviate some, but not all, of the deleterious effects of E+ on calf growth, although it may be more beneficial for reproductive traits in purebred cows.

Reproductive and preweaning data on 233 Angus (A), Brahman (B), and reciprocal-cross cows (AB, BA) and 455 two- and three-breed cross calves managed on common bermudagrass or endophyte-infected tall fescue were used to evaluate the interaction of forage type with individual and maternal heterosis and maternal and grandmaternal breed effects. Cows were born from 1988 to 1991 and calves from 15 Polled Hereford sires were born from 1991 to 1994. Heterosis for calving rate was similar and important on both forages (P< .01), but maternal effects were small on each forage. Maternal heterosis for birth weight differed between common bermudagrass and tall fescue (P< .10) and grandmaternal effects were evident on bermudagrass (P< .05) but not tall fescue. Forage effects were generally substantial for 205-d weight, weaning hip height, and weaning weight:height ratio (P< .01), and maternal heterosis for these traits was larger on tall fescue than on common bermudagrass (P< .01). Grandmaternal effects were in favor of Angus for 205-d weight, hip height, and weight:height ratio on common bermudagrass (P< .05) but not on tall fescue. Heterosis for 205-d weight per cow exposed was substantial on both forages (P< .01) and was numerically larger on tall fescue than on bermudagrass, but maternal effects were not significant. These results suggest more advantage for Brahman-cross cows over purebreds on endophyte-infected tall fescue than a similar comparison on common bermudagrass. They also suggest an advantage for Angus in grandmaternal effects on bermudagrass but not tall fescue.

Calculated energy consumed in 284 cow yr by individually fed Angus, Charolais and reciprocal cross cows was partitioned into maintenance, weight change and milk production requirements. Total digestible nutrient (TDN) consumed in 94 heifer yr was partitioned into maintenance and weight change requirements. The cow year was subdivided into midgestation, late gestation and lactation periods that were 69 ± 1, 90 ± 0 and 203 ± 1 d long, respectively. Variables affecting TDN intake (P<.25) in all periods studied were mean body weight (MWT), weight change and age of dam. Previous parity influenced TDN consumption during midgestation and milk production influenced TDN consumption during lactation. Mean body weight was evaluated by three methods as one of the variables influencing TDN consumption; MWT1.00, MWT to a fractional exponent (MWTx) calculated from the data and MWT with the regression line forced through the origin (zero intercept) were substituted in the multiple regression model. Equations were used to predict daily TDN for cows over a range of weights. Results indicate that method of analysis influenced predicted daily TDN requirements. Use of MWT1.00and MWTxresulted in similar predictions, while the zero intercept technique underestimated energy requirements for small cows and overestimated energy requirements for large cows. Inclusion of an intercept allowed the best fitting regression line to intersect the Y axis at the point determined by the data. Quadratic effects of weight were nonsignificant in all periods. Total energy requirements of cows and heifers in this study exceeded previously published recommendations because of environmental influences.

Breed group differences in feed energy requirements (estimated total digestible nutrient or TDN intake) per unit weaning weight, slaughter weight and retail product yield were evaluated in Angus, Charolais and reciprocal cross cows and their two- and three-breed cross calves born from 1972 to 1976. Even though there were significant breed group differences in cow weight, annual cow TDN, milk production, calf preweaning and postweaning TDN and retail cut yield, there was little evidence of breed group differences in feed energy requirements per unit weaning weight or per unit retail product yield. However, Angus cows and their calves were more efficient in total TDN per unit slaughter weight. Feed energy requirements per unit slaughter weight and per unit retail product yield were adjusted to a common age, weight or longissimus muscle fat basis. There was little evidence of an interaction of breed group with any covariate, and adjustment to common endpoints did not significantly affect differences among breed groups. There was little evidence of individual or maternal heterosis in cow traits or calf preweaning traits, respectively; but there was evidence of adverse maternal heterosis in postweaning TDN per unit of gain and total feed energy requirements per unit slaughter weight. Correlations among traits measured suggested favorable relationships between feed energy per unit output (weaning weight, slaughter weight, retail product yield) and milk production, weaning weight, slaughter weight and slaughter age.

Data including 122 records collected from 73 individually-fed drylot cows and their calves produced from 1972 through 1974 were analyzed to evaluate the comparative accuracy of weaning weight vs the ratio of calf weight to cow weight or calf weight to metabolic cow weight as predictors of feed required to produce 1 kg of calf at weaning. Results indicate that weaning weight was the best single predictor of efficiency followed closely by the ratio of calf weight to metabolic cow weight and the ratio of calf weight to cow weight. There appears to be no advantage in using cow weight in a ratio to predict efficiency, but it can be combined with weaning weight to achieve a 3% increase in the coefficient of determination for efficiency.

One-hundred-fourteen cows (30 Guernsey and 84 Holstein), diagnosed as having ovarian cysts via rectal palpation, were treated at randon with a single IM injection of either 50, 100 or 250 µg synthetic gonadotropin-releasing-hormone (GnRH) or a sham injection of the carrier vehicle for GnRH (0 µg). All animals were from one Guernsey and three Holstein herds maintained on a reproductive herd health program where routine examinations were performed at weekly or biweekly intervals. Clinical diagnosis of ovarian cysts was based upon the finding of a single or multiple formation of smooth, fluctuant, rounded structures of 2.5 cm in diameter or larger on one or both ovaries. Response to treatment was recorded as positiveif the animal established a normal estrous cycle or conceived and negativeif no change in character, size or location of the cystic structure could be determined in a 2-to 4-week period. Positive response to treatment was not significantly different among the groups that received GnRH (50, 100 and 250 µg), but each was different from the animals receiving 0 µg GnRH (P<.01). Positive response of cows in the 50, 100 and 250 µg groups was 18 of 28 (64%), 23 of 28 (82%) and 23 of 30 (77%), respectively, in contrast to 6 of 28 (21%) given 0 µg. For cows positively responding to treatment, the mean time in days from treatment to estrus, conception rates and services per conception for cows receiving 0, 50, 100 and 250 µg GnRH were 24.0, 4 of 6 (67%) and 1.5; 22.8, 13 of 18 (72%) and 1.6; 22.4, 20 of 23 (87%) and 1.6; and 22.2, 17 of 23 (74%) and 1.9, respectively.