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Orientador: Alexandre Secorun Borges / Banca: Márcio Rubens Graaf Kuchembuck / Banca: Ivan Roque de Barros Filho / Resumo: O presente trabalho teve como objetivo determinar os elementos minerais no soro sangüíneo (magnésio, cobre, selênio, zinco, fósforo, cálcio, potássio, ferro) e no tecido hepático (cobalto, cobre, selênio, manganês, molibdênio e zinco) em seis diferentes momentos durante um período de dezesseis meses e verificar se houve variação entre eles. Foram utilizadas 25 novilhas mestiças Nelore, com idade média de 18 meses, que permaneceram durante todo o tempo do experimento no mesmo pasto de Brachiaria brizantha. Os animais ainda receberam mistura mineral comercial em cocho coberto e água à vontade e foram submetidos à coleta de fragmentos hepáticos e sangue para obtenção de soro. Análises da pastagem também foram realizadas nos mesmos momentos em que foram colhidas as amostras de soro e fígado (exceto em fevereiro 2003). A água e o sal mineral também foram analisadas. Os níveis médios dos elementos no tecido hepático foram, respectivamente para as seis diferentes colheitas: Co 0,27;0,27; 0,23;0,21; 0,23 e 0,24 ppm; Mn 9,07; 8,55; 8,67; 8,40; 7,90 e 7,25 ppm; Mo 4,18; 3,85; 3,68; 3,32; 3,54; 3,19 ppm; Zn 113,4; 101,94; 97,91; 92,46; 88,29 e 81,74 ppm; Cu 40,76; 36,33; 24,50; 24,70; 77,75 e 128,03 ppm e Se 0,86; 1,09; 0,72; 1,21; 0,91 e 0,75 ppm. Destes, os níveis de Co, Mn, Mo, Se e Zn foram considerados adequados para bovinos. Os níveis médios dos elementos no soro foram, para as quatro diferentes colheitas: Ca 118,72; 129,36; 125,19; 112,90; 96,76; 85,37 mg/L; P 109,28; 106,30; 117,03; 103,39; 115,78 e 107,75 mg/L; Mg 19,75; 23,62; 26,54; 20,96; 20,80 e 23,12 mg/L; K 139,64; 134,85; 114,19; 131,65; 130,57 e 116,60 mg/L; Cu 0,52; 0,73; 0,41; 0,59; 0,60 e 0,73 mg/L; Zn 1,19; 1,87; 1,38; 1,13;1,28 e 1,37 mg/L; Fe 2,52; 3,44; 2,21; 3,08; 3,00 e 2,89 mg/L e Se 1,19; 1,87; 0,19; 0,44, 0,40 e 0,51 mg/L...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objective of the present work was to determinate the mineral levels in beef cattle blood serum (magnesium, copper, selenium, zinc, phosphorus, calcium, potassium, iron) and liver (cobalt, copper, selenium, manganese, molibdenium and zinc) at six different moments throughout sixteen months, to verify the occurrence of variation among them. Twenty-five half-breed nelore heifers, all of them about 18 months old, stayed during the experiment in the same Brachiaria brizantha pasture. They also received commercial mineral mixture in appropriate feeders and free acess to water. Pasture were also analised at the same moments we did for serum and liver (except february 2003). Water and mineral mixture were analised as well. The average levels of the elements in the liver, respectively for the six different moments: Co 0.27,0.27, 0.23, 0.21, 0.23 and 0.24 ppm; Mn 9.07, 8.55, 8.67, 8.40, 7.90 and 7.25 ppm; Mo 4.18, 3.85, 3.68, 3.32, 3.54, 3.19 ppm; Zn 113.4, 101.94, 97.91, 92.46, 88.29 and 81.74 ppm; Cu 40.76, 36.33, 24.50, 24.70, 77.75 and 128.03 ppm and Se 0.86, 1.09, 0.72, 1.21, 0.91 and 0.75 ppm. The levels of Co, Mn, Mo, Se and Zn were considered appropriate for cattle. The average levels of the elements in the serum were, for the six different moments: Ca 118.72, 129.36, 125.19, 112.90, 96.76, 85.37 mg/L; P 109.28, 106.30, 117.03, 103.39, 115.78 and 107.75 mg/L; Mg 19.75, 23.62, 26.54, 20.96, 20.80 and 23.12 mg/L; K 139.64, 134.85, 114.19, 131.65, 130.57 and 116.60 mg/L; Cu 0.52, 0.73, 0.41, 0.59, 0.60 and 0,73 mg/L; Fe 2,52; 3,44; 2,21; 3,08; 3,00 and 2,89 mg/L; Se 1.19, 1.87, 0.19, 0.44, 0.40 and 0.51 mg/L and Zn 1.19, 1.87, 1.38, 1.13,1.28 and 1.37 mg/L. In the serum, Ca, P, Mg, Zn, Fe and Se levels were considered appropriate for beef cattle. There was correlation between the hepatic and serum levels of Cu...(Complete abstract, click electronic address below) / Mestre

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 1991. / The contribution of browse and grass to the diets of cattle and goats was assessed in relation to the total biomass of woody foliage and grass available in the study area. Livestock made less use of browse during the dry season than was shown by studies conducted in the Sahel and Nylsvley, northern Transvaal. Goats fed more selectively, utilised newly flushed foliage more and fed upon a greater variety of woody plant species than did cattle. Browse contribute nore to goat diets than to cattle diets although goats were less often supplied with browse. For goats, feeding on standing browse, 'supplied browse and leaf litter occupied 34.7 % of observation time before the tree/shrub flush and 8.3 % post-flush; for cattle the contributions were 14.7 % and 5.8 %, respectively. Fruits, flowers and bark were utilised only during the pre-flush period and only by goats. Goats spent significantly more time grazing and more time browsing than did cattle during the post-flush period. Agave sisalana (sisal) contributed to cattle diets during the preflush and post-flush periods, and to goat diets during the pre-flush period. Since relatively little standing woody foliage is accessible to the animals (16.6 % preflush and 30.7 % post-flush of the wet season maximum), lopping of woody foliage by herders substantially increases the amount of food accessible to livestock, and supplied browse was eaten wherever it was encountered. Aerial cover of grass averaged less than 20 %, grass biomass ,less than 120 kgDM.ha·t and biomass concentration of grass less than 553.5 gDM.m"3 for catena toplands, catena bottomlands and drainage line thickets. The low contribution of browse to livestock diets during this study was due to the scarcity of accessible, palatable forage, exacerbated by the late flush 011 woody plants. In addition, local people harvesting live wood for fuel may compete with foraging livestock. To increase the supply of food for livestock further the rollowing practices could be encouraged: storage of woody foliage litter until the late dry season, use of chemicals to increase the nutritional value of poor quality browse and establishment of woodlots of palatable, perhaps leguminous, evergreen woody species for use as livestock fodder. / GR2017

In KwaZulu-Natal the production of beef in summer from veld is a common enterprise. Many techniques are available to optimise the productivity of this enterprise, from improving the quality of the grazing resource (planted pastures) to improving the diet of animals using nutritional supplements. To gain an insight into the production potential and financial returns possible from such improvements a trial was established at the Ukulinga Research Farm during two consecutive summer growing seasons (1997-1998 and 1998-1999). The aim was to determine the optimum beef production system for the area from both veld and kikuyu pastures. To evaluate the benefits of supplying supplementary nutrition, four alternate feed supplements, namely: 1) a Standard commercially available molasses-based protein/mineral/energy supplement; 2) a Brewers grain based protein/mineral/energy supplement, and two supplements consisting of the Brewers grain ration with either; 3) Avoparcin (an additive that improves dietary energy) or 4) Bentonite (an additive that increases the bypass of protein) were compared. As stocking rate has been shown to influence the quality of the diet consumed, the kikuyu pasture was grazed at both the recommended (1.92 LSD ha¯¹) and half the recommended stocking rate for the region. In addition, a commercial hormonal implant was applied to half of the cattle in each treatment. Grazing was monitored using the falling plate disc meter to measure pasture bulk density and laboratory analyses of herbage grab samples for digestibility and crude protein percentage. Cattle were weighed on a weekly basis and their condition was scored prior to slaughter. All enterprise costs and returns were recorded to facilitate financial analyses of the five treatments. Low rainfall and high midsummer temperatures had a detrimental effect on the productivity of the grazing and hence it was difficult to optimise production in either season. In the first season, a midsummer drought decreased the quality and quantity of both veld and kikuyu, limiting mass gain during the latter part of the season. A delay in the onset of rain at the start of the second season limited the available grazing season to 121 days as opposed to 154 days, though fodder production during the season was not limited. Trends in herbage production (quality and quantity) from veld showed moderate quality (Crude protein 7.02%; digestibility 50.2%) with an average available herbage of 1670 kg DM ha¯¹. As anticipated, kikuyu had higher quality (Crude protein 10.84%; digestibility 53.5%) and available herbage (2730 kg DM ha¯¹). These results were similar to regional benchmarks. The variable rainfall highlighted both the drought tolerance of veld and the minimum water requirements of kikuyu pastures. Lighter stocking rates tended to reduce the negative impact of moisture stress on Kikuyu pastures. The best method of producing beef (averaged over two seasons) was from heavily stocked Kikuyu pastures using the Standard supplement (1107.63 kg livemass ha¯¹). Cattle grazing veld and utilising the Avoparcin supplement produced beef at a rate of 95.96 kg ha¯¹. In comparison, the unsupplemented cattle grazing Kikuyu produced 834.87 kg ha¯¹, whilst veld grazing produced 64.43 kg ha¯¹. Hormonal implants significantly (P≤0.05) improved beef production from all sources of grazing. A lack of rain limited grazing time, causing all the cattle to be marketed whilst too lean - this negatively affected live mass gain and, hence, net financial. Although improved biological production is desirable, it is important to ensure that these gains are financially sustainable. Within the trial environment, implanted cattle fed the Standard supplement and grazing Kikuyu pastures at a high stocking rate provided the highest average gross margin of R 859.59 ha¯¹. Changing to this production system from unsupplemented veld improved expected profit by R 632.58 ha¯¹ (averaged over both seasons). Further financial analyses indicated that beef purchase price had the greatest influence on the added profit from switching from the control treatment. From a scientific standpoint these data are conclusive but it is important to remember that consumer pressure and concerns can often limit the introduction of production improvements. Such is the case with both hormonal implants and antibiotic feed additives (Avoparcin) although considering the impact of such limitations is speculative and beyond the scope of this trial. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

Three experiments compared ruminal, physiological, and performance responses of beef steers consuming hay ad libitum and receiving grain-based supplements with (CAM) or without (CO) inclusion of camelina meal. In Exp. 1, 9 steers fitted with ruminal cannulas received CAM (2.04 kg of DM/d) or CO (2.20 kg of DM/d). Steers receiving CAM had reduced (P = 0.01) total DMI and tended to have reduced (P = 0.10) forage DMI compared to CO. No treatment effects were detected (P ≥ 0.35) for ruminal hay degradability parameters. In Exp. 2, 14 steers receiving CAM (1.52 kg of DM/d) or CO (1.65 kg of DM/d) were assigned to corticotropin-releasing hormone (CRH; 0.1 μg/kg of BW) and thyrotropin-releasing hormone (TRH; 0.33 μg/kg of BW) challenges. Steers receiving CAM had greater (P < 0.05) serum concentrations of PUFA compared to CO prior to challenges. Upon CRH infusion, mean plasma ceruloplasmin concentrations increased at a lesser rate in CAM compared with CO (P < 0.01). Upon TRH infusion, no treatment effects were detected (P ≥ 0.55) for serum TSH, T₃, and T₄. In Exp. 3, 60 steers were allocated to 20 drylot pens. Pens were randomly assigned to receive CAM (2.04 kg of DM/steer daily) or CO (2.20 kg of DM/steer daily) during preconditioning (PC; d -28 to 0). On the morning of d 0, steers were transported for 24 h. Upon arrival from transport on d 1, pens were randomly assigned to receive, in a 2 x 2 factorial arrangement, CAM or CO during feedlot receiving (FR; d 1 to 29). During PC, CAM had reduced (P < 0.01) forage and total DMI, and tended to have reduced (P = 0.10) ADG compared to CO. Plasma linolenic acid concentrations increased during PC for CAM, but not for CO (P = 0.02). Steers that received CAM during FR had greater (P < 0.05) mean plasma concentrations of PUFA, and reduced mean rectal temperature and concentrations of haptoglobin and ceruloplasmin during FR compared to CO. Therefore, camelina supplementation reduced forage and total DMI, did not alter thyroid gland function, increased PUFA concentrations in blood, and attenuated the acute-phase protein reaction elicited by neuroendocrine stress responses. In conclusion, camelina meal is a feasible ingredient to reduce stress-induced inflammatory reactions and potentially promote cattle welfare and productivity in beef operations. / Graduation date: 2012

Perennial ryegrass (PRG, Lolium perenne) is a hardy cool-season grass that is infected with the endophytic fungus Neotyphodium lolii, which enables the plant to be insect repellant and drought resistant, lowering the use of insecticides and fertilizers. However, this fungus produces the compound lolitrem B (LB, m/z 686.4) which causes the tremorgenic neurotoxicity syndrome 'ryegrass staggers' in livestock consuming forage which contains <2000 ppb LB. Ergovaline (EV, m/z 534) is a vasoconstrictor normally associated with tall fescue (Festuca arudinacea), but has also been found in endophyte-infected PRG. Past research has shown a strong linear correlation between levels of LB and EV in PRG. The purpose of this study was to examine the linear relationship between EV and LB in feces and determine common metabolites. To accomplish this, four groups of steers (n=6/group) consumed endophyte- infected PRG over 70 days consumed the following averages of LB and EV: group I 2254ppb LB/633 ppb EV; group II 1554ppb LB/ 373ppb EV, group III 1011ppb LB/259ppb EV, and group IV 246ppb LB/<100ppb EV. Group I in week 4 was inadvertently given a washout period at which time the steers consumed the amount of LB and EV given to group IV (control). Both feed and feces samples were extracted using difference solid phase extraction methods and quantified by HPLC-fluorescence for LB and EV. Concentrations of EV and LB obtained through HPLC-fluorescence in both PRG and feces showed a linear relationship. Additional screening for metabolites was conducted LC-MS/MS and showed possible oxidation and reduction metabolites for both toxins. / Graduation date: 2013

Twenty four Jersey calves were randomly blocked according to sex and birth date, to determine the effects of supplementing Carica papaya seed (Linn) meal (CPSM) on health and growth performance of calves. In the first study, calves were fed CPSM for only 2 days to determine faecal pathogen population. In the second study; calves were randomly assigned at birth to three treatments and fed until weaning at 42 days. Each treatment had six calves. Treatments were; 1) a control group, which did not receive additive; 2) a group that was supplemented 5 g/d of Carica papaya seed meal (CPSM) and 3) the last group that was supplemented 5 g/d of a commercial product containing Lactobacillus acidophilus (Lact). After receiving milk with colostrum from their dams for 3 consecutive days after birth, calves had commercial starter pellet and fresh water ad lib. Treatments were added to whole milk from day 4 and fed to calves before being allowed to suckle from the dams for 30 min three times a day (08:00; 12:00 and 17:00). Calf starter dry matter intake (DMI) was evaluated daily while body weight (BW) and body structural growth were measured weekly. Faecal samples were collected directly from the rectum on day 7 and 10, before and after receiving CPSM respectively. The DMI; DMI/BW; BW and BWG of calves did not differ among treatments, and averaged 305.4 g/d; 7.7 g/d per BW; 39.4 kg and 32.1 kg, respectively. The initial BW, 22.2 ± 1.49 kg did not differ among groups, but the weaning BW was higher (p<0.05) for CPSM fed calves compared to control diet fed calves. It did not differ between control and Lact calves. Calves in Lact and CPSM treatments had similar average daily gain (ADG) and heart girth (HG), which were higher (p<0.05) than calves fed the control treatment. Calves fed CPSM had higher (p<0.05) hip width (HW) and shoulder height (SH) than control calves. There were effects of time (p<0.001) for starter DMI/BW, ADG and all structural body parameters, and effects (p<0.05) of interaction between time and treatments for only starter DMI/BW, ADG and HG. The CPSM treatment reduced faecal coliforms and E. coli (p<0.05) by 93.6% and 96.1%, respectively; and tended to reduce Enterobacteriaceae (p=0.056) by 96.4%. The present study revealed that feeding CPSM to calves during the pre-weaning period increased growth performance by improving average daily gain, feed efficiency and enhancing health status due to low faecal pathogen count / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)

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)

Made available in DSpace on 2014-06-11T19:23:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-01-26Bitstream added on 2014-06-13T20:11:42Z : No. of bitstreams: 1 mouraesilva_fc_me_botfmvz.pdf: 536732 bytes, checksum: b483c8eb0344fa45e6c29e1db8477c14 (MD5) / Fundação para o Desenvolvimento da UNESP (FUNDUNESP) / O presente trabalho teve como objetivo determinar os elementos minerais no soro sangüíneo (magnésio, cobre, selênio, zinco, fósforo, cálcio, potássio, ferro) e no tecido hepático (cobalto, cobre, selênio, manganês, molibdênio e zinco) em seis diferentes momentos durante um período de dezesseis meses e verificar se houve variação entre eles. Foram utilizadas 25 novilhas mestiças Nelore, com idade média de 18 meses, que permaneceram durante todo o tempo do experimento no mesmo pasto de Brachiaria brizantha. Os animais ainda receberam mistura mineral comercial em cocho coberto e água à vontade e foram submetidos à coleta de fragmentos hepáticos e sangue para obtenção de soro. Análises da pastagem também foram realizadas nos mesmos momentos em que foram colhidas as amostras de soro e fígado (exceto em fevereiro 2003). A água e o sal mineral também foram analisadas. Os níveis médios dos elementos no tecido hepático foram, respectivamente para as seis diferentes colheitas: Co 0,27;0,27; 0,23;0,21; 0,23 e 0,24 ppm; Mn 9,07; 8,55; 8,67; 8,40; 7,90 e 7,25 ppm; Mo 4,18; 3,85; 3,68; 3,32; 3,54; 3,19 ppm; Zn 113,4; 101,94; 97,91; 92,46; 88,29 e 81,74 ppm; Cu 40,76; 36,33; 24,50; 24,70; 77,75 e 128,03 ppm e Se 0,86; 1,09; 0,72; 1,21; 0,91 e 0,75 ppm. Destes, os níveis de Co, Mn, Mo, Se e Zn foram considerados adequados para bovinos. Os níveis médios dos elementos no soro foram, para as quatro diferentes colheitas: Ca 118,72; 129,36; 125,19; 112,90; 96,76; 85,37 mg/L; P 109,28; 106,30; 117,03; 103,39; 115,78 e 107,75 mg/L; Mg 19,75; 23,62; 26,54; 20,96; 20,80 e 23,12 mg/L; K 139,64; 134,85; 114,19; 131,65; 130,57 e 116,60 mg/L; Cu 0,52; 0,73; 0,41; 0,59; 0,60 e 0,73 mg/L; Zn 1,19; 1,87; 1,38; 1,13;1,28 e 1,37 mg/L; Fe 2,52; 3,44; 2,21; 3,08; 3,00 e 2,89 mg/L e Se 1,19; 1,87; 0,19; 0,44, 0,40 e 0,51 mg/L... / The objective of the present work was to determinate the mineral levels in beef cattle blood serum (magnesium, copper, selenium, zinc, phosphorus, calcium, potassium, iron) and liver (cobalt, copper, selenium, manganese, molibdenium and zinc) at six different moments throughout sixteen months, to verify the occurrence of variation among them. Twenty-five half-breed nelore heifers, all of them about 18 months old, stayed during the experiment in the same Brachiaria brizantha pasture. They also received commercial mineral mixture in appropriate feeders and free acess to water. Pasture were also analised at the same moments we did for serum and liver (except february 2003). Water and mineral mixture were analised as well. The average levels of the elements in the liver, respectively for the six different moments: Co 0.27,0.27, 0.23, 0.21, 0.23 and 0.24 ppm; Mn 9.07, 8.55, 8.67, 8.40, 7.90 and 7.25 ppm; Mo 4.18, 3.85, 3.68, 3.32, 3.54, 3.19 ppm; Zn 113.4, 101.94, 97.91, 92.46, 88.29 and 81.74 ppm; Cu 40.76, 36.33, 24.50, 24.70, 77.75 and 128.03 ppm and Se 0.86, 1.09, 0.72, 1.21, 0.91 and 0.75 ppm. The levels of Co, Mn, Mo, Se and Zn were considered appropriate for cattle. The average levels of the elements in the serum were, for the six different moments: Ca 118.72, 129.36, 125.19, 112.90, 96.76, 85.37 mg/L; P 109.28, 106.30, 117.03, 103.39, 115.78 and 107.75 mg/L; Mg 19.75, 23.62, 26.54, 20.96, 20.80 and 23.12 mg/L; K 139.64, 134.85, 114.19, 131.65, 130.57 and 116.60 mg/L; Cu 0.52, 0.73, 0.41, 0.59, 0.60 and 0,73 mg/L; Fe 2,52; 3,44; 2,21; 3,08; 3,00 and 2,89 mg/L; Se 1.19, 1.87, 0.19, 0.44, 0.40 and 0.51 mg/L and Zn 1.19, 1.87, 1.38, 1.13,1.28 and 1.37 mg/L. In the serum, Ca, P, Mg, Zn, Fe and Se levels were considered appropriate for beef cattle. There was correlation between the hepatic and serum levels of Cu...(Complete abstract, click electronic address below)

Made available in DSpace on 2016-12-08T16:24:23Z (GMT). No. of bitstreams: 1 PGCV04MA001.pdf: 365827 bytes, checksum: 83549fc5b733303769d0838e07c56a4e (MD5) Previous issue date: 2004-12-17 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work the effects of the total and partial substitution of ground corn for dry rolled barley on the production and composition of milk was evaluated. Twenty-eight primiparous and multiparous Holsteins cows were used, with an average of 125 days in milk at the beginning of the experiment. The design of the experiment was a 4x4 latin square, each square being repeated seven times. Once a day, the diet was supplied in a totally mixed ration (TMR). Four levels of barley substitution for corn were tested, based on the dry matter of the concentrate (T1 - 0% barley; T2 - 33 % barley; T3 - 67% barley; and T4 - 100% barley). Diets were balanced according to the results of nutrient analysis of the feedstuffs. The ratio forageconcentrate, based on the dry matter intake (DMI), was of 55% to 45%. The experiment had a total duration of 105 days, including an initial adaptation period of 21 days and four periods of 21 days for treatment. The first 14 days of each treatment period were destined to the adaptation to the diet and the seven remaining days for data collection. The cows were milked twice a day (05:00 and 16:00 h), in a 4x4 milking parlour. The milk production was registred electronically measured. The contents of fat, protein, total solids of the milk, as well as the somatic cell count (SCC) were obtained on the 18th and 21rst day of each treatment period and the milk urea nitrogen (MUN) was determined at the end of each period. The body condition score (BCS) was evaluated at the beginning and end of each period. The mean values of dry matter intake (DMI), milk yield, production of 4% fat-corrected milk (FCM), and fat and protein contents, as well as their standard error of the mean were of 19.64±0.18kg, 26,95±0.12kg, 25.76±0.13kg, 3.72±0.02% and 3.23±0.01%, respectively. DMI decreased in a linear fashion when barley substituted for corn in the diet. The intake of crude protein (CP), neutral fiber detergent (NDF) and acid fiber detergent (ADF) however were not affected when substituting corn by barley. Linear reduction was observed in milk yield, FCM production and fat and protein contents of the milk as a function of the level of corn substitution by barley, while the protein percentages increased in a linear manner. No effect was registered concerning the levels of substitution on the protein production, total solids of the milk, SCC, MUN and on the conversion efficiency / O objetivo deste trabalho foi avaliar os efeitos da substituição total e parcial de grãos de milho moídos por grãos de cevada laminados sobre a produção e composição do leite, bem como, verificar quais os níveis de substituição são mais adequados. Foram utilizadas 28 vacas Holandesas, primíparas e ,multíparas, com média de 125 dias de lactação ao início do experimento, em um delineamento do tipo Quadrado Latino 4x4, sendo cada quadrado repetido 7 vezes. A dieta foi fornecida na forma de dieta totalmente misturada (DTM), 1 vez ao dia. Foram testados 4 níveis de substituição de milho por cevada, com base na matéria seca do concentrado (T1 0% cevada; T2 33 % cevada; T3 66% cevada; e T4 - 100% cevada). As dietas foram balanceadas com base na análise bromatológica dos alimentos utilizados. A relação volumoso:concentrado, baseada na ingestão de matéria seca (IMS), foi de 55%:45%. O experimento teve uma duração total de 105 dias, constituído de um período de adaptação de 21 dias e 4 períodos de 21 dias por tratamento, sendo os 14 primeiros dias de cada período para adaptação à nova dieta e os 7 dias restantes para a coleta de dados. As ordenhas foram feitas 2 vezes ao dia (05:00 e 16:00 hs), em sala de ordenha 4x4, sendo que a medição do leite foi feita eletronicamente. A percentagem de gordura, proteína e extrato seco total do leite, bem como a contagem de células somáticas foram determinadas 2 vezes nos dias 18 e 21 de cada período e a determinação do nitrogênio ureíco no leite (NUL) foi efetuada ao final de cada período. A avaliação do escore da condição corporal (ECC) foi feita no início e no fim de cada período. Os valores médios de IMS, produção de leite, produção de leite corrigido para 4% (LCG), e percentagens de gordura e proteína , bem como seus erros-padrão foram de 19,64±0,18 kg, 26,95±0,12 kg, 25,76±0,13 kg, 3,72±0,02% e 3,23±0,01%, respectivamente. A IMS decresceu linearmente quando a cevada substituiu o milho na dieta. Porém a ingestão de proteína bruta (PB), fibra em detergente ácido (FDA) e fibra em detergente neutro (FDN) não foram afetadas pela substituição do milho pela cevada. Foi observada redução linear na produção de leite, LCG, produção e na percentagem de gordura do leite em função do nível de substituição de milho por cevada, enquanto a percentagem de proteína aumentou linearmente. Não houve efeito do nível de substituição sobre a produção de proteína, extrato seco total (EST), contagem de células somáticas (CCS), NUL e na eficiência alimentar (EA)