Linseed meal (LSM) was fed to ovariectomized ewes exposed to estradiol 17-ß (E2) implants over time, and LSM was supplemented to beef cows during late gestation and early lactation to evaluate the estrogenic potential of the phytoestrogen secoisolariciresinol diglycoside (SDG) found in LSM. Forty-eight ovariectomized ewes were fed a diet containing 12.5% LSM for 0, 1, 7, or 14 d and implanted with estradiol-17ß (E2) for 0, 6, or 24 h before tissue collection. Uterine cellular proliferation, vascularity, and the expression of the angiogenic factors and their receptors were recorded. There was an interaction of LSM and E2 on uterine mass (P = 0.05). At 24 h of E2 exposure, proliferation was reduced (P < 0.001) when ewes were fed for 14 d compared to being fed 0 or 1 days. There was a LSM x E2 interaction (P ≤ 0.03) on VEGF receptor-2 (KDR) and hasicfihrohlast growth factor receptor (FGFR2) decreasing by 24 h E2 exposure. Exposure of LSM and E2 may impact the estrogenic response of sensitive tissue. Two studies were conducted to examine the effects of supplementing beef cows with LSM during late gestation or early lactation on calf growth and development. In Experiment 1, multiparous cows received either LSM or a control (CON) supplement (approximately 10% diet dry matter) for the last 60 d of gestation. Offspring weights, ADG, heifer age at puberty, conception percentage and steer carcass characteristics were recorded. In Experiment 2, multiparous cows received LSM or CON supplements (approximately 10% diet dry matter) during the first 60 d of lactation, and only heifer calf development performance was observed and recorded. Heifer calf weight, average daily gain, and attainment of puberty were assessed. For both experiments, birth weight, weaning weight and ADG were not affected (P > 0.31) by LSM supplementation. While final body weights were heavier (P = 0.04) for steer calves in Experiment 1, there was no effect (P = 0.09) of supplementation on carcass characteristics. In Experiment 1 and 2, attainment of puberty in heifer calves was not influenced (P > 0.58) by supplement type. Linseed meal supplementation during late gestation or early lactation does not appear to have a negative impact on calf growth, onset of puberty in heifer calves, or steer carcass quality, implicating that it may make a good supplement choice in cattle.

Excessive dietary protein may affect MP use because of energetic costs of excreting excess N. Amino acids also may influence post-ruminal digestion. Therefore, two experiments were designed to evaluate the effects of MP intake and post-ruminal flow of AA on growth performance and pancreatic digestive enzymes. In experiment 1, treatments supplied different amounts of MP intake to cattle and the effects on growth performance and feeding behavior were evaluated. In experiment 2, duodenal infusion of glutamate or casein was examined and the effects on pancreatic enzymes were measured. Experiment 1 suggests that feeding steers 906 g MP/d in finishing diets supplied enough MP for the greatest growth performance and carcass characteristics. Interestingly, MP intake caused different responses on feeding behavior with greater effects on steers fed 626 and 1444 g MP/d. In experiment 2, casein infusion increased α-amylase activity but not trypsin activity. Glutamate did not influence pancreatic digestive enzymes.

Corn-based ethanol production has increased dramatically in the past ten years, causing an increase in demand for corn by ethanol producers and an increase in production of ethanol by-products such as distillers' grains. The increase in ethanol production can be attributed to ethanol policy at the state and federal levels. Because of the increase in production of corn-based ethanol, cattle producers face greater competition for a major feed source, corn, and greater supply of an emerging feed source, distillers' grains. The objective of this study is to analyze and quantify the effects of ethanol policy on cattle production. A theoretical model and an econometric model are used to fulfill the objectives of this study. The theoretical model contains an ethanol model and a general livestock model. Results of the theoretical model present the possibilities of ethanol policy affecting cattle production. The econometric model identifies the indirect and direct effects of ethanol policy on cattle production. The results of the econometric model indicate that there is a relationship between ethanol policy, specifically the Renewable Fuel Standard, and cattle production.

Leafy spurge (Euphorbia esula L.) is a costly noxious weed to manage in the Northern Great Plains; it invades rangelands and displaces native and desirable vegetation. Our first objective was to test the recommended full rate and half rate of selected herbicides applied in September following a spring burn on a leafy spurge invaded plant community. Our second objective was to determine if raffinate (desugared beet molasses) applied to leafy spurge invaded rangeland would attract cattle to consume leafy spurge. The aminocyclopyrachlor with chlorosulfuron treatment had the best leafy spurge control at the full rate, with stem density reductions of 95 percent for both sites nine and twelve months after treatment. The salt block treatment had the best success at reducing leafy spurge stem density. Herbicides can be the most common and effective type of management; however, manipulating livestock to graze noxious weeds converts a weed into a useable forage.

Explanatory feeder cattle basis models were developed for 16 different Virginia markets by season, futures contract month, weight, lot size, sex, breed and USDA grade differentials. The models are more disaggregated and explain up to 80 percent more of feeder cattle basis variation than any previous research. Since the variables in these explanatory models are all known in advance, these basis models are also predictive. Basis estimates from these models make it possible for a Virginia feeder cattle forward pricing agency to offer forward price and minimum price contracts to small size operators. / Master of Science

Two trials using 32 heifers each evaluated response to undegraded intake protein (UIP) (30 or SO% CP), energy (supporting .S9 or .91 kg ADG), and source of UIP (blood meal or combination protein supplement). Trial one was a 2x2 factorial, with two levels of energy and UIP. High UIP was achieved with blood meal supplementation. From 6-13 mo of age (phase I), high energy increased ADG and DMI, and high UIP decreased DMI. DM efficiencies (kg DMIlkg BW gain) improved with high energy and high UIP, and roN efficiencies (kg IDN/kg BW gain) improved with high UIP. From 13 mo until calving (phase n), heifers were housed together and fed a common diet. Low energy, high UIP treatment had the highest ADG (1.01 kg/day) for phase I, but the lowest for phase n (.33 kg/day), and low energy, low UIP treatment had the lowest ADG (.62 kg/day) for phase I, but the highest for phase n (.S3 kg/day). Overall ADG from 6 mo until calving averaged .S9 kg/day, and was not affected by energy or UIP. In trial 2, two levels of energy and two sources ofUIP were compared, resulting in four treatments: low energy, high UIP with combination protein supplement; low energy, high UIP with blood meal; low energy, low VIP with soybean meal; and high energy, low UIP with soybean meal. Combination protein supplement contained blood meal, com gluten meal, and fish meal. Trial was 300 days long, and began at 6.5 mo. of age. Dry matter intake and ADO were increased with high energy, but not affected by VIP. Overall DM efficiency was not affected by VIP or energy level. Results of both trials indicate VIP may improve feed efficiency of growing Holstein heifers. / Master of Science

Experiments were conducted to investigate effects of endophyte (Acremonium coenophialum Morgan-Jones and Gams) infection of tall fescue (Festuca arundinacea Schreb.) on grazing cattle and subsequent feedlot performance, serum minerals and prolactin, intake, digestibility, bite size, and biting rate. Grazing animal performance was measured April to October, 1989 and 1990, at two locations in VA. Effects of grazing low (<5%) and high (>70%) endophyte infected tall fescue, with and without white clover (Trifolium repens L.), were studied with yearling steers. At each location, two replicates were used with a stocking rate of .3 ha/steer (116 steers/yr). At the end of grazing, all animals were finished on a high corn silage diet and slaughtered. Daily gains of steers grazing low endophyte-infected pastures were higher (P<.01) than for those grazing high endophyte-infected pastures. Cattle grazing high endophyte-infected tall fescue with clover at Glade Spring gained at the same rate as those grazing the low endophyte-infected tall fescue without clover during Summer, 1989. During 1990, cattle at Glade Spring had higher (P<.05) daily gains than did those at Blackstone. Rectal temperatures were .5 to 1 °C higher (P<.05) for steers grazing infected pastures by June of each year at both locations. Prolactin concentrations were lower (P<.01) in cattle grazing endophyte-infected fescue within 28 d of initiation of grazing at both locations. Visual evaluation indicated that steers grazing high-endophyte pastures had rough hair coats compared to those grazing low endophyte pastures (P<.01), showing evidence of tall fescue toxicosis. Serum mineral analyses indicated no consistent influence of the endophyte. During feedlot finishing, there were no detrimental effects from previously grazing endophyte-infected tall fescue on animal performance. Forage DM yield, and CP in 1990, and IVDMD in 1989 and 1990 from Glade Spring were higher (P<.05) compared to Blackstone. Forage from Blackstone was typically higher in NDF, ADF, and lignin compared to Glade Spring. Forage from Glade Spring was higher in Ca, Mg, P, and Cu, compared to Blackstone. Diet selection, digestibility, biting size, and biting rate were measured with esophageally-fistulated steers grazing low (<5%) and high (>70%) endophyte-infected tall fescue, with and without white clover. Bite size was smaller (P<.05) in July compared to May, corresponding to decreased quantity of forage available. Bite size and biting rate were not affected by endophyte infection or inclusion of clover. In vitro DM digestibility was higher (P<.05) for high endophyte-infected tall fescue in July. Animals consumed a higher percentage of clover than was available in the sward. Intake and digestibility were estimated using 48 experimental animals and four esophageally-fistulated steers. Chromic oxide sustained-release boluses and forage IVDMD were used to estimate intake. The chromic oxide boluses were determined to be reliable for predicting intake of steers during a 21 d trial involving total fecal collection. Intake was higher (P<.01) in cattle grazing low endophyte-infected tall fescue compared to animals grazing high endophyte-infected fescue. Twenty-one Angus steers (256 kg) were used to compare the effect of 0 and 40% endophyte-infected tall fescue and orchardgrass hay on DM intake, daily gain, body temperature, serum minerals, and prolactin concentrations during an 8 wk study. Quality of the diets was low, as indicated by low CP (8.1 to 10.3%), and IVDMD (41.3 to 47.1%). Daily DM intake and daily gain were higher (P<.05) for animals consuming the noninfected tall fescue compared to animals fed the other hays. Body temperature and serum prolactin were not affected by diet. These data suggest that other factors, besides endophyte infection, are important in the etiology of tall fescue toxicosis. Some of the decreased performance of steers grazing endophyte-infected tall fescue was related to lower intake. Additional research is needed to evaluate higher levels of clover to possibly ameliorate some of the problems of tall fescue toxicosis. / Ph. D.

Growth and body composition of 121 Holstein heifers (4.6 to 18 mo and 129 to 407 kg) reared on pasture, drylot and pasture-drylot systems were evaluated in 6 experiments. Heifers were switched from drylot to pasture or the reverse to study carry-over effects from previous treatments; both systems were satisfactory. Alternate 28-day periods of supplement feeding to grazing heifers did not affect final body weight nor wither height, but ADF and heart girth varied during 2 yr. When switching drylot heifers previously fed low and high TDN, to pasture, gains were best for heifers fed the lower TDN diet; also, gains on pasture were best for light heifers. Gains by all heifers grazing mainly orchardgrass-clover pasture were acceptable, but supplementing with a 19% CP concentrate or lasalocid, usually improved gains. Heifers with lowest BW during grazing made compensatory gains in drylot. Urea space estimation technique showed that compensatory gains were mainly fat. Lasalocid feeding increased daily gain and subcutaneous fat deposition but reduced feed intake and ribeye area. When moving grazing heifers to drylot a total mixed ration with fishmeal or soybean meal as protein sources gave similar responses. DM intake of grazing heifers ranged from 8.1 to 10.1 kg/d, vs 7.5 kg/d for arylot. Supplementing grazing heifers with degradable or undegradable protein gave similar responses in growth and body composition. Based on growth and body composition, seasonal grazing of Holstein heifers may reduce costs for rearing replacement heifers. A corn silage-alfalfa silage-orchardgrass hay mixed ration without concentrates when fed ad libitum to heifers in drylot resulted in gain of 934 g/d. Pasture alone heifers gained from 368 to 755 g/d depending on drought and heifer age. Calculations of costs of rearing Holstein replacement heifers were prepared accounting for observations of response to grazing, supplements to grazing and drylot diets. Well managed grazing reduces costs of rearing. / Ph. D.

Forage of beta-carotene-fortified orange-fleshed sweet potato is essential for alleviation cattle malnutrition. The study aims were to determine effects of supplementing sweet potato (SP) roots and sun dried forage on degradation of dietary legumes, intake and milk yield in dairy cattle. Mature SP roots were oven dried and forage vines and leaves (V&L) sun dried. Lactating dairy were supplied meals with total mixed ration (TMR) constituting varying levels of sweet potato forage and concentrate. The SP flour was rapidly and completely degraded In Sacco while degradability of V&L was comparable to that of Lucerne hay. Rumen degradation of Lucerne was reduced when the legume was incubated proximal to SP. Substitution of TMR with fresh SP forage and flour meal increased degradability of diets. Glucose post-feeding was increased (P<0.05) by SP roots but no change in milk yield. Orange-fleshed SP forage is recommended for improving energy supply in lactating cow diets / Agriculture and  Animal Health / M. Sc. (Agriculture)

Thesis (MScAgric)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The objectives of this study were to determine the effects of supplementing oat silage (OS) with lucerne (LH) and oat hay (OH) on the production performance of lactating Jersey cows, as well as comparing the ruminal degradability of LH, OH and OS III Holstein and Jersey cows receiving a high forage diet and a high concentrate diet. In the first trial, five diets containing different combinations of OS and LH together with concentrate mixtures providing 26, 23, 20, 17 and 14% crude protein (CP) were fed to lactating Jersey cows. Lucerne hay was fed at 0, 2, 4, 6, and 8 kg DM/day while OS was fed ad libitum. Cows receiving only OS as a forage source had a lower (P<0.05) dry matter (DM) intake and produced less milk protein (P<0.05). Milk and fat yields as well as milk urea nitrogen (MUN) levels did not differ (P>0.05) between treatments. In the second trial, OS was fed with OH and a concentrate mixture containing 26% CP to lactating Jersey cows. Oat hay was fed at 0, 2, 4, 6, and 8 kg DMiday while OS was fed ad libitum. Cows that received OS together with 4 and 6kg OH, respectively had higher (P<0.05) DM intakes. Milk, fat, and protein yields as well as MUN levels did not differ (P>O.05) between treatments. The ruminal degradability of LH, OH and OS in Holstein and Jersey cows receiving (i) a high forage and (ii) a high concentrate diet was determined. The two breeds were also compared in terms of rumen pH levels, volatile fatty acids (VF A) and rumen ammonia nitrogen (NH3-N) concentrations as affected by time after feeding. The ruminal degradability of freeze dried (FD), oven dried (OD) and fresh oat silage (FS) in Jersey cows receiving a high forage diet was also determined. The ruminal DM, CP and NDF degradability of LH was higher (P<O.05) than that of OH and OS in both Holstein and Jersey cows when they were fed either a high forage or a high concentrate diet. When cows were fed a high forage diet, the effective DM degradability of OS was higher (P<O.05) in Holsteins although the CP degradation rates of LH and OH were higher (P<O.05) in Jerseys. When they were fed a high concentrate diet, Jerseys had higher (P<O.05) effective DM and NDF degradabilities and higher (P<O.05) DM and NDF degradation rates in LH while Holsteins had higher (P<O.05) effective CP degradability levels than Jerseys in OS. After feeding a high forage diet, pH levels declined while VFA and NH3-N concentrations increased (P<O.05) in both breeds. Jerseys had higher rumen pH, lower (P<O.05) VFA and lower NH3-N concentrations than Holsteins throughout the study. When cows were fed a high concentrate diet, Jerseys had higher (P<O.05) pH than Holsteins. A post-feeding decline (P<O.05) in pH was observed in both breeds. Fresh oat silage had a lower (P<O.05) effective degradability and degradation rates for DM, CP and NDF in comparison to FD and OD oat silage. The DM, CP and NDF degradation rates, as well as effective NDF degradability were higher (P<O.05) for FD silage, but effective DM and CP degradabilities were higher (P<O.05) for OD oat silage. It was concluded that on an oat silage diet, lactating Jersey cows should receive a minimum of 2kg LH or 4 to 6kg oat hay together with ad libitum OS to improve DM intake. When cows were fed a high concentrate diet, the ruminal degradability appeared to be superior in Jerseys than Holsteins. Jerseys also had higher rumen pH levels lower VFA and NH3-N concentrations than Holsteins. Feeding interval affects the rumen environment, pH declines while VF A and NH3-N concentrations increased. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die effek van die aanvulling van hawerkuilvoer met lusemhooi (LH) en hawerhooi (HH) op die melkproduksie van Jerseykoeie te bepaal. Hiermee saam is die rumen degradeerbaarheid van hawerkuilvoer en lusemhooi ondersoek in Jersey en Holsteinkoeie wat 'n hoe-ruvoer en 'n hoe-kragvoer gebaseerde dieet ontvang het. In die eerste proef is vyf diete met verskillende peile van hawerkuilvoer en lusernhooi saam met kragvoere van verskillende ruproteienpeile (26, 23, 20, 17 en 14% RP) aan 10 lakterende Jerseykoeie gevoer. Hawerkuilvoer is ad libitum voorsien en lusemhooi is teen vlakke van 0, 2, 4,6 en Skg droemateriaal (DM) per dag gevoer. Die DM-inname en melkproteienproduksie van koeie wat hawerkuilvoer as die enigste ruvoerbron ontvang het, was laer (P<0.05) as ander ruvoerkombinasies. Die melk- en vetproduksie, asook melk-ureumstikstofpeile het nie tussen behandelings verskil nie (P>0.05). In die tweede proef is hawerkuilvoer saam met hawerhooi (soortgelyk as Proef 1) gevoer. Die kragvoerkomponent van al die ruvoerkombinasies het 26% RP bevat. Die koeie wat hawerkuilvoer en 4 of 6kg hawerhooi as ruvoere ontvang het, het hoer (P<O.05) droemateriaalinnames gehad. Melk, vet en proteienproduksie asook melk-ureumstikstofpeile het nie tussen ruvoerkombinasies verskil nie (P>O.05). Die rumendegradeerbaarheid van lusemhooi, hawerhooi en hawerkuilvoer is bepaal in Holstein en Jerseykoeie wat (i) 'n hoe ruvoer- en (ii) 'n hoe kragvoerdieet ontvang het. Die rumen pH, vlugtige vetsuur en rumen-ammoniakkonsentrasies, soos beinvloed deur tyd na voeding, is ook tussen rasse vergelyk. Die rumendegradeerbaarheid van vars, oondgedroogde en vriesgedroogde hawerkuilvoer is ook bepaal. Die rumen DM, RP en NDF degradeerbaarhede van lusemhooi was hoer (P<O.05) as by hawerhooi en hawerkuilvoer in beide Holstein en Jerseykoeie wat (i) 'n hoe ruvoer- en (ii) 'n hoe kragvoerdieet ontvang het. Op 'n hoe ruvoerdieet, was effektiewe DM degradeerbaarheid van hawerkuilvoer by Holsteins hoer (P<O.05) as by Jerseys. Jerseykoeie het egter 'n hoer (P<O.05) RP degradeerbaarheidstempo van lusemhooi en hawerhooi gehad. Jerseykoeie op 'n hoe kragvoerdieet, het hoer (P<O.05) effektiewe DM en NDF degradeerbaarhede getoon. Hulle het egter 'n laer (P<O.05) effektiewe ruprotein (RP) degradeerbaarheid by hawerkuilvoer as Friese gehad. Jerseykoeie op lusemhooi het ook 'n hoer (P<O.05) DM en NDF degradeerbaarheidstempo getoon. Jerseykoeie wat 'n hoe ruvoerdieet ontvang het, het 'n hoer (P<O.05) rumen- pH en laer (P<O.05) vlugtige vetsuur- en rumen-ammoniak konsentrasies as Holsteinkoeie gehad. Jerseykoeie wat 'n hoe kragvoerdieet ontvang het, het ook 'n hoer (P<O.05) rumen- pH as Holsteinkoeie gehad. By al die koeie is gevind dat rumen- pH na voeding afgeneem het (P<O.05). Vlugtige vetsuur- en rumen-ammoniakkonsentrasies was laag voor voeding en het daama toegeneem (P<O.05). Vars hawerkuilvoer het laer (P<O.05) effektiewe DM, RP en NDF degradeerbaarhede en degradeerbaarheidstempo's as oond- en vriesgedroogde hawerkuilvoer gehad. Die vriesgedroogde kuilvoer het hoer (P<O.05) DM, RP en NDF degradeerbaarheidstempo's sowel as effektiewe NDF degradeerbaarhede gehad. Oondgedroogde kuilvoer het daarinteen hoer (P<O.05) effektiewe DM en RP degradeerbaarhede gehad. Die gevolgtrekking is gemaak dat lakterende Jerseykoeie ten minste 2kg lusemhooi of 4- 6kg hawerhooi per dag moet ontvang wanneer hulle hawerkuilvoer as ruvoerbron ontvang. Op 'n hoe kragvoerdieet, het dit gebleik dat die rumendegradeerbaarheid van vesel by Jerseys beter is as by Holsteins. Die rumen- pH is hoog voor voeding, maar dit neem af nadat die koeie gevreet het. Die rumen- pH van Jerseys was hoer as by Holsteins. Die vlugtige vetsure en rumen-ammoniakkonsentrasies blyk laag te wees voor voeding en neem daama toe. Konsentrasies was hoer by Holstein as by Jerseys.