Lactating cows were exposed to moderate and hot, humid weather to determine the effect of increasing ambient temperature, relative humidity, or temperature-humidity index (THI) on intake, milk yield, and milk temperature. Minimum and maximum temperatures averaged 17.9 and 29.5 degrees C (cool period) and 22.5 and 34.4 degrees C (hot period), and minimum and maximum THI averaged 63.8 and 76.6 (cool period) and 72.1 and 83.6 (hot period). Environmental conditions had minor effects on intake and milk yield during the cool period. During the hot period, the THI 2 d earlier and mean air temperature 2 d earlier had the greatest impact on milk yield and DMI, respectively. Both breeds maintained milk temperature within normal ranges during the cool period, but Holstein and Jersey p.m. milk temperatures averaged 39.6 and 39.2 degrees C during the hot period. Current day mean air temperature during the hot period had the greatest impact on cow p.m. milk temperature, and minimum air temperature had the greatest influence on a.m. milk temperature. Dry matter intake and milk yield declined linearly with respective increases in air temperature or THI during the hot period and milk temperature increased linearly with increasing air temperature. Dry matter intake and milk yield both exhibited a curvilinear relationship with milk temperature. Environmental modifications should target the effects of high temperatures on cow body temperature and should modify the environment at critical times during the day when cows are stressed, including morning hours when ambient temperatures are typically cooler and cows are not assumed to be stressed.

A study was undertaken to compare Tifton 85 (T85) and Coastal (CBG) bermudagrasses for effects of cultivar and age at harvest on yields of DM and digestible DM, in vitro digestion, nutrient content, cell wall composition, in situ digestion kinetics, and feed intake and digestion by growing beef steers. In Exp. 1, T85 and CBG forages staged for growth in May or July of 1993 were harvested at 3, 4, 5, 6, 7, and 8 wk from subplots. Tifton 85 bermudagrass had 7.1% greater DM yield, 18.2% higher (P < .05) digestible DM yield, and 7.1% greater IVDMD than CBG, and, after 5 wk of forage growth, IVDMD of both T85 and CBG decreased with increased age at harvest (P < .05). In Exp. 2, T85 and CBG forages staged for growth in July 1997 were harvested at 2, 3, 4, 5, 6, and 7 wk from subplots. Even though T85 had higher concentrations of NDF and ADF than CBG, T85 had 34.1% higher DM yield, 47.9% higher digestible DM, 55.0% higher digestible NDF, 91.7% higher digestible ADF, greater IVDMD, in vitro NDF and ADF disappearances, and higher in situ DM and NDF digestion (P < .05). Coastal bermudagrass had higher concentrations of lignin and lower concentrations of total neutral sugars, arabinose, glucose, and xylose than T85 (P < .05). In vitro digestibilities of DM, NDF, and ADF were lower and concentrations of ADF and lignin were greater for 7- vs 6-wk harvests of both T85 and CBG (P < .05). In Exp. 3, T85 and CBG forages staged for growth in July 1997 were harvested as hay at 3, 5, and 7 wk from .8-ha pastures and fed to 36 individually penned growing beef steers (initial BW = 244 kg) to quantify ad libitum intake without supplementation. Tifton 85 bermudagrass had lower concentrations of lignin and ether-linked ferulic acid and greater concentrations of NDF, ADF, hemicellulose, and cellulose than CBG (P < .05). Steers fed T85 had higher (P < .05) digestion of DM, OM, NDF, ADF, hemicellulose, and cellulose than steers fed CBG. Digestion of NDF, ADF, hemicellulose, and cellulose decreased (P < .05) with increased age at harvest for both cultivars. In conclusion, T85 produced more DM and had more digestible nutrients in vitro, in situ, and in vivo than CBG, and 3 and 5 wk of growth would be recommended ages to harvest either cultivar.

Two 4 x 4 replicated Latin square studies, each containing 8 lactating Holstein cows, were conducted simultaneously in south Georgia during the summer. The effects of dietary cation source (Na or K) and increasing dietary cation-anion balance (milliequivalents of Na + K - Cl per kilogram of feed DM) within cation source (control = 120.4 meq/kg of feed DM; Na source = 219.7, 347.8, 464.1 meq/kg of feed DM; K source = 231.2, 352.6, 456.0 meq/kg of feed DM) were determined on performance and acid-base chemistry during hot, humid weather. Cow body temperatures were elevated by environmental conditions but were not affected by dietary cation-anion balance. Differences in body temperature from dietary cation source probably were related to differences in cow BW. Intake of DM increased linearly, but yields of milk and FCM did not change with increasing dietary cation-anion balance, and cation source had no effect. Milk fat and protein percentages were not altered by dietary cation-anion balance, and greater milk fat and protein percentages from cows offered the Na versus K source diets probably were due to differences between cows in the two Latin squares. Alterations in blood acid-base chemistry with increasing dietary cation-anion balance were as expected. Greater blood buffering capacity, indicated by blood base excess and bicarbonate content, may be responsible for the improved feed intake.

Two Latin square studies, each containing eight primiparous cows (four Holstein, four Jersey), were conducted to determine the effect of changing dietary electrolyte balance during cool and hot environmental conditions on performance of lactating dairy cows. Electrolyte balance, expressed as Na + K - Cl in milliequivalents per kilogram of diet, was altered by changing K and Cl content in the diet using potassium bicarbonate or calcium chloride. Maximum and minimum temperatures averaged 26.7 and 15.0 degrees C during the cool phase and 32.3 and 22.5 degrees C during the hot phase of the study. Milk yield improved linearly with increasing electrolyte balance with nonsignificant treatment by phase interaction, whereas DMI of cows improved quadratically with increasing dietary electrolyte balance. A treatment by phase interaction for DMI was detected, although intake of DM reached a plateau at a similar dietary electrolyte balance during the cool and hot phases. Body (milk) temperature of cows appeared to be related to the level of feed consumed and varied by treatment within phase. Body (milk) temperature was higher during the hot phase of the experiment. Blood bicarbonate and pH were lowest in cows offered the low electrolyte balance (high Cl) diet, and blood and urinary Na + K-Cl increased linearly with increasing dietary electrolyte balance. The response to dietary electrolyte balance appeared to be mediated through blood buffering and the impact on physiologic systems of the cow.

both in the national and international markets (Carter and Wilson, 1998;Boerma and Mian, 1998). Soyfoods Soybean [Glycine max (L.) Merr.], an important component of have been reported to provide protection against heart the Asian diet, is gaining popularity as a source of vegetable protein and phytochemicals in the USA. However, soybean cultivars with disease, cancer, menopausal symptoms, and other disdesirable agronomic traits and biochemical components that enhance eases (Carter and Wilson, 1998; Messina and Messina, the quality of soyfoods have not been identified for cultivation in the 1991). Because of the nutraceutical value of soybean, USA. Twelve soybean genotypes, including three from Japan, were there is a growing demand for soyfoods, such as soymilk, evaluated for their agronomic performance, genotype ϫ environment several types of tofu, soybean sprouts, and soynuts. Soy-(GE) interactions, and yield stability at four locations in the USA food sales in the USA have been growing steadily at a from 1994 to 1997. At maturity, seed yield, biomass, harvest index rate of 10 to 25% yr Ϫ1 (Kuhn, 1996) and exceeded $600 (HI), and 100-seed dry weight were determined using plants harvested million in 1998. About 9 to 10 million t of soybean seed from the middle two rows of each plot. Genotypic differences for the are imported into Asia for manufacturing soyfoods and traits examined were significant. The mean seed yield across locations for oil extraction. Tofu, a cottage cheese-like soybean and years ranged from 2.0 to 3.0 Mg ha Ϫ1 . The Japanese cultivars had larger seeds but were outyielded by the American genotypes by ≈10% curd, has high nutritional value and is rich in proteins, and up to 35% by 'Hutcheson'. The genotype effects were significantly vitamins, and minerals, particularly Ca. Tofu consumplarger than the location ϫ year effects for plant height, seed weight, tion is growing at an annual rate of 20% in the USA and HI, but not for biomass or seed yield. Biomass and HI were and among health-conscious people around the world important determinants of seed yield. S90-1056, V81-1603, V71-370, (Carter and Wilson, 1998). Thus, the increasing market 'Enrei', 'Nakasennari', 'Ware', and 'York' were stable for seed weight for soyfoods and health benefits associated with them across years. Hutcheson, S90-1056, York, MD86-5788, Nakasennari, indicate the economic potential and emphasize the need and BARC-8 showed yield stability across environments and years.for the identification and development of high-yielding S90-1056, York, and Nakasennari were stable for both seed weight and U.S. soybean cultivars suitable for food processing and seed yield; therefore, they could be used for commercial production in human consumption. the USA or for breeding soybean cultivars suitable for tofu preparation.