Orientador: José Luiz Moraes Vasconcelos / Resumo: Este estudo avaliou o efeito de injeções de GnRH (hormônio liberador de gonadotrofina) ou hCG (gonadotrofina coriônica humana) no dia 5 após inseminação artificial (IA) nas taxas de concepção em vacas lactantes durante o verão. Vacas holandesas, n=158, produzindo 26±9 kg de leite/dia e 213±112 dias pós-parto (DPP), foram aleatoriamente distribuídas em 3 grupos: Controle (GC; n=52); GnRH (GG; n=55), 100 mcg IM. de gonadorelina (Cystorelinâ); e hCG (GH; n=51), 2500 UI IM de hCG (Vetecorâ). A temperatura retal foi verificada no momento da IA, e as amostras de sangue coletadas nos dias 5; 7 e 12 após IA para avaliar as concentrações séricas de progesterona (P4). A prenhez foi determinada entre os dias 42 e 49 após IA. Os dados foram analisados pelo procedimento MIXED do SAS, e foram incluídos no modelo efeitos do tratamento, ordem de lactação, produção de leite, temperatura retal no momento da IA e suas interações. O tratamento com GnRH ou hCG aumentou a P4 sérica (P<0,01). As concentrações séricas de P4 (ng/ml; média ± EPM) para GC, GG, e GH foram, respectivamente, no dia 5: 2,71±0,43; 2,45±0,44 e 3,23±0,45, no dia 7: 4,79±0,43; 4,15±0,44 e 5,75±0,45, e no dia 12 após IA: 5,21±0,43; 6,91±0,44 e 8,50±0,45. Devido ao aumento proporcional na concentração sérica de P4 entre os dias 5 e 7 após IA (GC: 77, GG: 69, GH: 77%; P<0,01) é provável que os tratamentos não tenham induzido o efeito luteotrópico no CL existente, porém devido ao grande aumento na P4 sérica no dia 12 nos animais tratados (GG: 112, GH: 87%; P<0,01) em relação aos animais controle (GC: 16%; P=0,31), provavelmente houve a indução de um novo CL. A temperatura retal média das vacas no momento da IA foi de 39,7°C e o tratamento com GnRH ou hCG aumentou as taxas de concepção (média ± EPM) nas vacas com temperatura retal abaixo de 39,7°C... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study evaluated the effect of GnRH (gonadotropin releazing hormone) or hCG (human chorionic gonadotropin) injection on day 5 after artificial insemination (AI) on conception rates in lactating dairy cows during the summer. Holstein cows, 158, producing 26 ± 9 kg milk/d and 213 ± 112 days in milk, were randomly assigned to one of 3 treatments groups: control (CG: n=52); GnRH (GG: n=55), injection of 100 mcg i.m. of gonadorelin (Cystorelin®) and hCG (HG: n=51), injection of 2500 UI hCG i.m. (Vetecor®). Rectal temperature was checked at the moment of AI and blood samples collected on days 5, 7 and 12 after AI to evaluate serum progesterone (P4) concentrations. Pregnancy was determined between 42 and 49 d after AI. Data were analyzed by the MIXED procedure of SAS and were included in the model the effects of treatment, parity, milk production, rectal temperature at the moment of AI and interactions. Treatment with GnRH or hCG increased serum P4 (P<0,01). Serum P4 concentrations (ng/ml, mean±SEM) for CG, GG and HG were, respectively, on day 5 2.71±0.43, 2.45±0.44 and 3.23±0.45, on day 7, 4.79±0.43, 4.15±0.44 and 5.75±0.45 and on day 12 after AI, 5.21±0.43, 6.91±0.44, 8.50±0.45. Due to the proportional increase in serum P4 concentration from d 5 to 7 after AI (CG: 77, GG: 69, HG: 77%, P<0,01), it is likely that treatments did not have luteotropic effect on the existing CL, but due the higher increase in serum P4 on day 12 in the treated animals (GG: 112, HG: 87%; P<0,01) in relation to the control group animals (GC: 16%; P=0,31), probably induced the formation of a new CL. The average rectal temperature of cows at time of AI was 39,7°C. Treatment with GnRH and hCG increased conception rates (mean±SEM) in cows with rectal temperature below 39,7°C (CG: 10.1±0.075, n= 26, GG: 36.8±0.073, n=27, HG: 32.8±0.088%, n=21; p<.01)... (Complete abstract click electronic address below) / Mestre

The thesis deals with analysis the influence to effectiveness of Holstein cows bred on the School farm in Haklovy Dvory. I studied the most frequent reasons of culling cows on the farm and the influence on the cost accounts.

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Durante o puerpério há muita incidência de doenças reprodutivas acarretando aumento do intervalo entre partos, bem como diminuição na taxa de concepção. A endometrite é uma enfermidade puerperal que se caracteriza por um processo inflamatório superficial do endométrio. Com o intuito de se obter novas ferramentas diagnósticas não invasivas, precisas e que proporcionam resultados precoce à reprodução, faz-se uso da ultrassonografia convencional associada a ferramenta Doppler que fornece informações em tempo real sobre a arquitetura vascular e os aspectos hemodinâmicos dos vasos em diversos órgãos. Este estudo tem por objetivo descrever, através da ultrassonografia Doppler, as alterações hemodinâmicas no útero de fêmeas bovinas causadas pela endometrite. Avaliou-se o trato reprodutivo feminino de vacas entre 25 a 35 dias pós-parto utilizando a vaginoscopia, ultrassonografia convencional e Doppler, além de citologia e exame microbiológico em 89 vacas Holandesas sendo 33 sadias (controle) e 56 com endometrite diagnosticadas por citologia (saudáveis &lt;10% de polimorfonucleares). Os resultados obtidos destacam-se a que animais com endometrite apresentavam aumento de cérvix (p=0,04), e de útero representado pelo corno esquerdo (p=0,02). Porém não foi observado diferença quando comparado os escore de condição corporal (ECC). Quanto a ultrassonografia notou-se que animais com fluido intrauterino (FIU) e conteúdo heterogêneo intrauterino (CHIU) tinham endometrite (p&lt;0,0001), além de correlação com a presença de Trueperella pyogenes e leveduras. Com o modo cores do Doppler obteve-se a vascularização de mesométrio (p=0,004) e endométrio (p=0,025) associada aendometrite. Entretanto não foi observado diferença estatística nas medidas do Doppler espectral (índice de resistividade, pulsatilidade e fluxo sanguíneo). Portanto a busca de novas técnicas, menos invasivas e de rápido resultado, como a ultrassonografia Doppler, podem fornecer respostas satisfatórias quanto a evolução de alterações uterinas e com isso associar os resultados à precocidade reprodutiva. / During the puerperium period there is a high incidence of reproductive diseases resulting in increased calving interval and decrease in conception rate. The endometritis is a postpartum disease that is characterized by a superficial inflammation of endometrium. With the aim to obtain new non-invasive and accurate diagnostic tools, that provide early results in reproduction, it is possible to be used the conventional ultrasound associated to Doppler that provides real time information about vascular architecture and hemodynamic aspects of vessels in several organs. This study aims to describe, through Doppler ultrasound, hemodynamic changes in the uterus of cows caused by endometritis. Were evaluated the female reproductive tract of 89 Holstein cows between 25 to 35 days postpartum using vaginoscopy, conventional ultrasound and Doppler, as well as cytology and microbiological examination. From the 89 animals that were studied, 33 were healthy (control) and 56 with endometritis diagnosed by cytology (healthy &lt;10% polymorphonuclear). The obtained results show that animals with endometritis had increase in cervix (p = 0.04) and the uterus represented by left uterine horn (p = 0.02). However, it was not detected difference when compared the body condition score (BCS). About the ultrasound was noted that animals with intrauterine fluid (IUF) and intrauterine heterogeneous content (IUHC) had endometritis (p &lt;0.0001) correlation with the presence of Trueperella pyogenes and yeasts. With the color Doppler mode it was possible to obtain the vascularization of mesometrium (p = 0.004) and endometrium (p = 0.025) associated with endometritis. However, it was not observed statistical difference in the measurements of the spectral Doppler (resistance index, pulsatility and blood flow). Therefore, the search for new techniques, less invasive and fast result, as the Doppler ultrasound can provide satisfactory answers as the evolution of uterine changes and thereby associate the results to the reproductive precocity.

No description available.

Doctor of Philosophy / Department of Animal Sciences and Industry / Twig T. Marston / The primary study investigated the use of ractopamine HCl and implants in cull beef cows. Thirty-two cull cows were used to determine the effects of feeding ractopamine HCl and/or implanting on feedlot performance and carcass composition. Cows were individually fed a high concentrate diet for 60 days. Carcass data were collected and carcasses were fabricated. Implanted cows had greater dressing percentages and tended to have heavier hot carcass weights than non-implanted cows. Cows that had been treated with implant and ractopamine HCl tended to be fatter than those not treated. Ractopamine HCl fed cows had more marbling than their contemporaries. The data also indicated that younger cows (< 6 years of age) had greater feedlot performance than the older cows. An experiment was conducted to determine if corn and grain sorghum dried distillers grains could be effective protein supplements for growing cattle. Crossbred heifers (n = 78) were individually fed 2.72 kg·head·-1d·-1 of supplements containing corn, soybean meal, and grain sorghum; or cracked corn and corn distillers grains with solubles; or cracked corn, sorghum distillers grains with solubles, and ground grain sorghum (all formulated to equal 20% CP). Heifers grazed native-grass and were fed smooth broom hay. A digestion trial was done during the last week of the trial. No differences were noted in weight gain or total diet digestibility, however, DMI was less for heifers receiving either distiller’s based supplement. Ninety-six pregnant, mature, spring-calving cows grazing native grass pasture were used to determine if early weaning calves reduced subsequent winter supplementation cost. Previous to the feeding trial, calves had been weaned at 115 or 212 d of age. Cows were fed either 1.4 kg·hd-1·d-1 or 1.27 kg·hd-1·d-1 of a common 45% CP supplement. Cows were supplemented for an average of 110 d of pregnancy. Earlyweaned cows were heavier and had greater body condition scores than contemporaries at the commencement of supplementation. At calving the early-weaned cows fed the lesser supplemental amount had similar body weight and body condition scores as later-weaned cows fed the greater amount of supplement, thus, the early weaning routine allowed a 30% savings of winter protein supplement.

During spring kikuyu-ryegrass pasture has a low dry matter (DM) content (10-12%), is highly digestible and has high levels of soluble carbohydrates. Low rumen pH values have been recorded for cows grazing these pastures even when supplemented with low levels of concentrate. The rumen environment and extent of rumination may therefore be sub-optimal. Supplementation of the pasture with dry roughage may improve rumination, the rumen environment and therefore also milk production performance. The aim of the study was to determine if strategic supplementation of lucerne hay will improve milk production, milk composition and the rumen environment of cows grazing high quality kikuyu/ryegrass during spring and receiving low levels of concentrate. Forty eight high producing Jersey cows were blocked and randomly allocated to one of the following treatments: control (no supplemental roughage), supplementation of 1.0 kg lucerne hay and supplementation of 2.0 kg lucerne hay after morning milking. Cows received 5 kg of dairy concentrate per day during milking. Cows grazed as one group and pasture was allocated to ensure a post grazing height of 10-12 on the rising plate meter (5-6 cm). The average post grazing pasture height for the experimental period was 10.83±1.68 (n=73) on the RPM (5.42 cm). There were no differences (P >0.10) between the treatments for 4% fat corrected milk production, which were 22.2 kg/d for the control, and 22.5 kg/d and 22.9 kg/d for the 1 kg and 2 kg lucerne treatments respectively. Milk fat and protein percentage was not affected (P >0.10) by supplementation of lucerne hay. The milk lactose content of cows receiving the control and 1 kg lucerne hay treatments were higher (P <0.05) than those of cows receiving the 2 kg lucerne hay treatment. Eight rumen cannulated Jersey cows were randomly allocated to either the control or the 2 kg lucerne hay treatment in a cross-over design. These cows grazed together with the cows of the production study and received the same dairy concentrate. Rumen pH was measured for 48 hours with 10 minute intervals using an automated pH logging system. Rumen samples were taken at 08:00, 14:00, 20:00 and 02:00 and were analysed for ammonia-nitrogen (NH3-N), volatile fatty acids (VFA) and pH. An in sacco study was conducted to determine DM and neutral detergent fibre (NDF) disappearance of ryegrass. There were no differences (P >0.10) between treatments in overall mean pH, measured with either the logging systems or with the portable pH meters averaging 6.18 and 6.11 for cows receiving the control and the 2 kg lucerne treatment respectively. The mean rumen NH3-N did not differ (P >0.10) between treatments. The mean concentration of acetic acid and the total VFA concentration was higher (P <0.05) for cows receiving the 2 kg lucerne treatment compared to the control. There were no differences (P >0.10) between treatments in the DM or NDF disappearance of ryegrass after 24 hours. Supplementation of lucerne hay to cows grazing well managed kikuyu-ryegrass pasture during spring did not improve milk production, milk composition, rumen pH or in situ NDF disappearance of ryegrass Results suggest that cows grazing kikuyu/ryegrass pastures supplemented with low levels of concentrate consume sufficient eNDF to maintain a favourable rumen environment and normal milk composition. Copyright / Dissertation (MSc(Agric))--University of Pretoria, 2012. / Animal and Wildlife Sciences / unrestricted

Energy is the first-limiting nutrient for cows grazing pasture therefore, energy supplementation is necessary for high producing animals. In pasture-based systems, the concentrate is fed twice a day in the dairy parlour during the milking procedure. Consumption of large amounts of fermentable carbohydrates results in a drop in rumen pH and this may induce rumen acidosis. This may lead to reduced intake, lower fibre digestion and depressed milk yield. Supplemental yeast offer great possibilities in stabilising the rumen fermentation patterns and, therefore, improving dry matter intakes (DMI). This may increase milk production, milk composition parameters, rumen volatile fatty acid concentrations (VFA) which leads to higher profits. Investigating these responses, a trial was conducted, where live yeast (Levucell SC 10 ME-Titan) was supplemented to Jersey cows grazing ryegrass/kikuyu pastures, supplemented with 6 kg (as is) dairy concentrate per day split over two milking periods. Thirty multiparous high-producing Jersey cows between 30 and 120 days in milk (DIM) were selected, blocked and randomly allocated to control (no yeast) or live yeast treatment groups. Ten fistulated lactating cows were added in a cross-over design (two periods and two treatments) and all 40 cows strip grazed Italian ryegrass (Lollium multiflorum) and kikuyu pastures as one group. A new pasture strip was allocated after each milking and pasture was measured using a rising plate meter (RPM). The yeast product Levucell SC 10 ME – Titan containing Saccharomyces cerevisiae CNCM I-1077 was supplied by Lallemand S.A.S (19 rue des Briquetiers, 31702 Blagnac cedex, France). The Levucell SC 10 ME – Titan is a micro-encapsulated formulation for premix and pelleted feeds. The yeast treatment group had the yeast pelleted in with the dairy concentrate at a concentration of 167 g of yeast per ton of concentrate, to obtain the required intake of 1 g yeast per cow per day as specified by Lallemand. Milk yields were recorded daily and composite milk samples were taken every two weeks to determine, milk fat, protein, lactose, milk urea nitrogen (MUN) and somatic cell count (SCC) contents. The fistulated cows were adapted to their respective diets and treatments for 21 days after which the pH measurment, rumen fluid sampling, and In sacco study were conducted. Milk yield, 4% fat corrected milk (FCM) yield, milk protein and lactose percentages, SCC, body condition score (BCS), and live weight did not differ (P > 0.05) between treatments. The milk fat% however, was higher for the yeast supplemented cows at 4.24% compared to the control group of cows of 3.99% (P < 0.05). The mean acetic and total VFA concentration (mmol/L) for the control treatment was higher compared to the yeast treatment (P < 0.05). There was no difference in the fermentation patterns of VFA, the pH and NH3-N values measured between treatments (P > 0.05). The mean In sacco neutral detergent fibre (NDF), organic matter (OM) and DM disappearance was higher for the yeast treatment group of cows after a 12 and 24 hour incubation compared to the control group (P < 0.05). The mean ruminal NDF disappearance of ryegrass in cows supplemented with yeast increased by 11.9% and 6.3% compared to the control at the 12 and 24 hour incubation periods, respectively. With higher fibre digestibilities in the rumen and more acetate available at the mammary gland and subsequently higher milk fat percentages, the yeast effects on stimulating the cellulolytic bacteria in the rumen, may be a possible explanation for the results in the current study and it is well documented in previous studies. Live yeast supplementation resulted in higher milk fat percentages which improved milk price. / Dissertation (MSc(Agric))--University of Pretoria, 2011. / Animal and Wildlife Sciences / unrestricted

Rumen-undegradable protein might be the first limiting nutrient for high producing dairy cows receiving high levels of maize supplementation while grazing pasture. To test this hypothesis two trials were conducted using fishmeal as a high quality protein source rich in rumen-undegradable protein, Methionine and Lysine. In the first trial cows grazed annual ryegrass for two months in spring. In the second trial cows grazed kikuyu for two months in late summer. In addition to the pasture cows received 6 kg (as is) of a maize-based supplement, including minerals, fed in two equal portions in the milking parlour. A randomised complete block design was used. Three groups of 15 (ryegrass) or 14 (kikuyu trial) cows received control (no fishmeal), low fishmeal (4 % fishmeal replacing maize) or high fishmeal (8 % fishmeal replacing maize) treatments. Multiparous, high producing, Jersey cows in early to mid lactation were used. Milk production was measured and milk samples taken fortnightly. Simultaneous studies were conducted using eight rumen cannulated cows receiving the control and high fishmeal treatments in a cross over design experiment. Ruminal pH, ammonia-N and volatile fatty acid concentrations were measured. In the ryegrass trial milk yield, 4 % fat-corrected milk yield and milk fat and protein percentages of cows on the low and high fishmeal treatments (21.9 and 22.1 kg milk/d, 24.1 and 24.2 kg 4 % fat-corrected milk/d, 4.73 and 4.67 % fat and 3.49 and 3.45 % protein) were significantly higher than the control (20.5 kg milk/d, 20.4 kg 4 % fat-corrected milk/d, 3.97 % fat and 3.25 % protein). There was no treatment effect on milk urea N (16.8, 17.4 and 17.9 mg/dl, for the control, low fishmeal and high fishmeal treatments, respectively). The ruminal ammonia-N concentration was significantly higher in the cows on the high fishmeal treatment than the control (16.67 vs. 14.16 mg/dl). Fishmeal supplementation to cows on ryegrass is profitable under any realistic price scenarios in South Africa. In the kikuyu trial cows on the high fishmeal treatment produced significantly more milk (19.5 kg/d) than the cows on the control (18.2 kg/d), neither differing from the low fishmeal treatment (18.9 kg/d). The cows on the low fishmeal treatment had significantly higher milk fat percentage (4.18 %) than the control (3.71 %), neither differing from the high fishmeal treatment (3.91 %). The cows on the two fishmeal treatments produced significantly more 4 % fat-corrected milk than the control (19.4 and 19.2 vs. 17.3 kg 4 % fat-corrected milk/d). There was no treatment effect on milk protein percentage (3.30, 3.41 and 3.34 % for the control, low and high fishmeal treatments, respectively). Milk urea N was significantly higher for the high fishmeal treatment (10.80 mg/dl) than the control and low fishmeal treatments (9.09 and 9.44 mg/dl). Ruminal ammonia-N concentration was significantly higher in the cows on the high fishmeal treatment than the control (6.52 vs. 4.74 mg/dl). Fishmeal supplementation to cows on kikuyu could be profitable under certain price scenarios. / Dissertation (MSc(Agric) (Animal Science))--University of Pretoria, 2008. / Animal and Wildlife Sciences / unrestricted

The widespread increase in use of maize-based feedstuffs in California dairy cow rations has raised concerns of reduced efficiency of CP utilization due to the low lysine content of maize and maize by-products. The objectives of this research were to determine the impact of increased dietary maize CP levels on animal performance using three metabolic models of dairy cows in order to predict limiting AA’s in California dairy rations to identify a ruminally protected AA package to supplement similar rations. Since lysine was the most consistently predicted limiting AA among dairies, and metabolic models, the dairy with the ration calculated to be the most limiting in lysine was chosen to determine effects of feeding an RPL product on milk production and composition, as well as on N balance. Nutrient profiles of 16 high multiparity cow rations were evaluated and limiting AA predicted by the metabolic models Amino Cow, CPM Dairy and Shield. Higher inclusion levels of maize products in rations increased the contribution of maize CP to the total CP content of the TMR, to between 20 – 40%, but had no impact on cow performance. Even though the lysine to methionine ratio decreased as more maize CP was included in the TMR, it did not have a major impact on the final predicted AA profile of MP, or milk component levels, but, according to Shield, it had an effect on milk yield. Methionine, isoleucine and lysine were predicted to be most limiting according to Amino Cow, CPM Dairy and Shield respectively. The models suggested three dramatically different AA packages but the high degree of consistency within model in predicting the limiting AA sequence among dairies, suggest that there may be sufficient consistency in the nutrient profiles among rations to support production of a ruminally protected AA complex. The second experiment used a double (i.e., early and mid-lactation multiparity dairy cows) 2 x 2 factorial with 28 day experimental periods. Feeding the RPL, with estimated rumen escape of lysine between 18 and 23% suggesting an increased intestinal absorption of lysine between 8 and 22 g/d/cow, did not influence DMI or milk, true protein and lactose yields. Milk fat yield and concentration decreased, while MUN percentages increased when RPL was fed. Blood plasma levels of almost all AA’s, except lysine, decreased when RPL was fed, suggesting that lysine was the limiting AA and that its supplementation led to increased absorption and utilization of other AA. The lack of response in milk protein synthesis and the decrease in plasma 3-MH concentrations when RPL was fed suggests that muscle protein synthesis was stimulated, and degradation reduced, with RPL feeding. It is possible that lysine had an effect, either directly or indirectly, on muscle protein turnover and energy metabolism that, impacted intakes, metabolism and absorption of AA and milk production in mid lactation cows, but it had no major impact on early lactation cows. Copyright / Dissertation (MSc(Agric))--University of Pretoria, 2009. / Animal and Wildlife Sciences / unrestricted