Made available in DSpace on 2014-06-11T19:35:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-02-23Bitstream added on 2014-06-13T20:26:14Z : No. of bitstreams: 1 bertipaglia_eca_dr_jabo.pdf: 1381681 bytes, checksum: 745ba23720e8cec6ab76449426629614 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo deste estudo foi avaliar os efeitos das características do pelame e da taxa de sudação (TS) sobre o desempenho reprodutivo de vacas da raça Braford e estimar as herdabilidades e correlações genéticas destas características. Dados da TS, espessura da capa (E), refletância da superfície da capa (R), comprimento dos pêlos (C), diâmetro dos pêlos (D) e número de pêlos por unidade de área (N) foram observados. Ainda, foram avaliadas as seguintes variáveis da reprodução: intervalo de partos (IEP); dias para o parto (DPP); idade ao primeiro parto (IPP); taxa de detecção de cio (Dcio); taxa de gestação para a primeira inseminação (G1IA) e taxa de gestação para a estação de monta (GEM). Os dados de desempenho reprodutivo referem-se aos partos dos anos de 2003 e 2004. Foram avaliadas as inseminações referentes às gestações da estação de monta do período de outubro de 2003 a janeiro de 2004. Durante este período, foram observadas temperatura máxima do ar (Ta), pressão parcial de vapor (Pv) e carga térmica radiante (CTR). As variáveis contínuas (todas as características do pelame, TS, IEP, DPP e IPP) foram analisadas pelo método dos quadrados mínimos. Os seguintes efeitos fixos foram considerados no modelo de todas as características do pelame: pais; grupos de contemporâneos; mês da observação; genótipo e idade. O pai da vaca foi importante para todas as características do pelame, exceto para N. Grupos de contemporâneos afetou todas as variáveis, o mês afetou a variação do C e da R. O genótipo foi importante para C, D e R e a idade afetou R. Na análise da TS foram considerados: grupos de contemporâneos; pais; genótipo; E; C; D; N; R; hora da observação; idade; Ta; Pv e CTR. Todos os fatores meteorológicos e grupos de contemporâneos foram significativos... / This study deals with the effects of hair coat characteristics and sweating rate on reproduction of Braford cows and estimation of heritabilities and genetic correlations of these traits. Data on hair length (L), coat thickness (T), hair diameter (D), number of hairs per unit area (N), coat reflectance (R) and sweating rate (SR) were recorded. In addition, calving interval (CI); days to calving (DC); age at first calving (AFC); Estrous detection rate (EDR); conception rate at first insemination (CR1AI) and conception rate at breeding season (CBS) were evaluated. The continuous data were analyzed by least squares methods; considering the following fixed effects on the model for hair coat traits: sires and contemporary groups; month; genotype and age. The effect of sire was important for all hair coat traits, except for N; contemporary groups affected all hair coat traits; the effect of sampling month was important for L and R; genotype affected L, D and R; age was important only for R. The model of SR considered the following fixed effects: contemporary groups; sires; genotype; T, L, D, N, R; time of day, age, air temperature (Ta), partial vapour pressure (Pv) and radiant heat load (RHL). All the meteorological factors and contemporary groups were significant on SR. Age at calving, genotype, sire, R, T, L, N, D and SR were considered as fixed effects on analyses of CI. For the analyses of DC were considered: R, T, L, N, D, SR, genotype, age and sire. Age, genotype and SR were significant on CI and DC. Age at first calving of heifers born from January to March (AFC1) and from July to October (AFC2) were analyzed. Only sire was significant on AFC1; sire, E and D affected the variation of AFC2. The binary traits EDR; CR1AI and CBS were analyzed by logistic regression models...(Complete abstract, acess undermentioned eletronic address)

Resumo: Está sendo amplamente difundida no Brasil e no mundo a sexagem de sêmen bovino através de citometria de fluxo. Considerando que não só o processo de criopreservação como também o processo de separação causam danos às células, esses danos têm sido amplamente estudados buscando-se alcançar maior proteção para o sêmen sexado durante a congelação. O objetivo deste trabalho foi desenvolver uma metodologia de congelação de sêmen sexado bovino com a utilização de dois diferentes diluentes. Para isso, 2 ejaculados de 10 touros em idade reprodutiva foram coletados em vagina artificial, avaliados e preparados para a separação por citometria de fluxo. Após a passagem pelo citômetro, as amostras foram divididas em 3 grupos (diferentes metodologias). Todos os grupos foram divididos em 2 subgrupos (diferentes diluentes: TRIS meio extensor padronizado pelo laboratório em questão e o diluente Botu- Bov®, meio extensor comercializado no Brasil Biotech Botucatu). Para o grupo 1 (GI) a medotologia utilizada foi a mesma padronizada pelo protocolo Sexing Technologies do Brasil; para o grupo 2 (GII), foi utilizado glicerol para o inicio da refrigeração; e para o grupo 3 (GIII) a glicerilização foi realizada a 18ºC e não a 5ºC como no controle (GI). A avaliação do sêmen foi realizada através de análise computadorizada (CASA) e por sondas fluorescentes para função mitocondrial e integridade da membrana plasmática e acrossomal. Para análise estatística utilizou-se o método Tukey com nível de significância p<0,05...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The sexed semen using flow citometry has been widely spread in Brazil and all over the world. The damage caused by the process of cryopreservation and separation is well known. Therefore, the sexed semen needs a higher protection during freezing process. The aim of the present study was to develop a bovine sexed semen freezing methodology with two different extenders. Thus 2 ejaculates of 10 bulls in reproductive age were collected with artificial vagina, analyzed and than prepared for the separation with flow citometry. After this procedure the samples were divided in 2 groups (different methodologies) and both groups were divided in 2 subgroups (different extenders: TRIS and Botu- Bov®). For group 1 (GI) the methodology applied was the same standardized by the protocol of Sexing Technologies of Brazil; for group 2 (GII) it was used glycerol for the beginning of the freezing and for group 3 (GIII) addition of glycerol was made at 18°C. The semen evaluation was made through CASA and fluorescent probes for the plasmatic and acrossomic membrane integrity and mitochondrial function. The statistic analysis was achieved using the Tukey method with significant level p < 0,05. There was no significant statistic difference for the analyzed parameters in regard to the methodology used; only the percentual of intact plasmatic membrane from GII with TRIS presented a smaller value compared to the other groups, also using TRIS. A significant difference between the extenders occurred in the main parameters evaluated, and Botu-bov® presented better results. The Botu-Bov® extender presented higher motility and higher number of cells after percoll...(Complete abstract, click electronic address below) / Orientador: Fernanda da Cruz Landim e Alvarenga / Coorientador: José Antonio Dell'Aqua Junior / Banca: Rubens Paes de Arruda / Banca: Frederico Ozanam Papa / Mestre

Made available in DSpace on 2014-06-11T19:29:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-02-23Bitstream added on 2014-06-13T20:38:44Z : No. of bitstreams: 1 freitas_cp_me_botfmvz.pdf: 357251 bytes, checksum: 6d07b31986079df6a989f919c5fd3069 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Está sendo amplamente difundida no Brasil e no mundo a sexagem de sêmen bovino através de citometria de fluxo. Considerando que não só o processo de criopreservação como também o processo de separação causam danos às células, esses danos têm sido amplamente estudados buscando-se alcançar maior proteção para o sêmen sexado durante a congelação. O objetivo deste trabalho foi desenvolver uma metodologia de congelação de sêmen sexado bovino com a utilização de dois diferentes diluentes. Para isso, 2 ejaculados de 10 touros em idade reprodutiva foram coletados em vagina artificial, avaliados e preparados para a separação por citometria de fluxo. Após a passagem pelo citômetro, as amostras foram divididas em 3 grupos (diferentes metodologias). Todos os grupos foram divididos em 2 subgrupos (diferentes diluentes: TRIS meio extensor padronizado pelo laboratório em questão e o diluente Botu- Bov®, meio extensor comercializado no Brasil Biotech Botucatu). Para o grupo 1 (GI) a medotologia utilizada foi a mesma padronizada pelo protocolo Sexing Technologies do Brasil; para o grupo 2 (GII), foi utilizado glicerol para o inicio da refrigeração; e para o grupo 3 (GIII) a glicerilização foi realizada a 18ºC e não a 5ºC como no controle (GI). A avaliação do sêmen foi realizada através de análise computadorizada (CASA) e por sondas fluorescentes para função mitocondrial e integridade da membrana plasmática e acrossomal. Para análise estatística utilizou-se o método Tukey com nível de significância p<0,05... / The sexed semen using flow citometry has been widely spread in Brazil and all over the world. The damage caused by the process of cryopreservation and separation is well known. Therefore, the sexed semen needs a higher protection during freezing process. The aim of the present study was to develop a bovine sexed semen freezing methodology with two different extenders. Thus 2 ejaculates of 10 bulls in reproductive age were collected with artificial vagina, analyzed and than prepared for the separation with flow citometry. After this procedure the samples were divided in 2 groups (different methodologies) and both groups were divided in 2 subgroups (different extenders: TRIS and Botu- Bov®). For group 1 (GI) the methodology applied was the same standardized by the protocol of Sexing Technologies of Brazil; for group 2 (GII) it was used glycerol for the beginning of the freezing and for group 3 (GIII) addition of glycerol was made at 18°C. The semen evaluation was made through CASA and fluorescent probes for the plasmatic and acrossomic membrane integrity and mitochondrial function. The statistic analysis was achieved using the Tukey method with significant level p < 0,05. There was no significant statistic difference for the analyzed parameters in regard to the methodology used; only the percentual of intact plasmatic membrane from GII with TRIS presented a smaller value compared to the other groups, also using TRIS. A significant difference between the extenders occurred in the main parameters evaluated, and Botu-bov® presented better results. The Botu-Bov® extender presented higher motility and higher number of cells after percoll...(Complete abstract, click electronic address below)

In presented thesis the chosen parameters of reproduction {--} days to first service, days open, calving interval, insemination index - were evaluated in dairy cattle. There were 222 of dairy cows observed (53 Czech Pied and 169 Holstein cows). The results of reproduction were evaluated as unsatisfactory. Length of calving interval overreached recommended 400 days in 56,25 % of Holstein and in 33,33% of Czech Pied cows. Also the mean value of insemination index 2,39 exceeds the optimum of 1,8-2,0.

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.

Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The aim of this study was to provide scientifically founded guidelines to enhance the understanding of beef production from natural pastures in arid sweet veld regions. Cattle from four breed types ranging from large to small frame sizes (Simmentaler cross > Bonsmara cross > Afrikaner > Nguni) were compared in terms of cow production and efficiency as well as the growth performance, carcass and meat quality of steers slaughtered at 18, 24 and 30 months of age. Eighteen and 30 month old steers were slaughtered at the end of the wet summer season, while the 24 month old steers were slaughtered at the end of the dry winter season. The Afrikaner herd (59.8 ± 9.0 %) had lower (p < 0.05) pregnancy rates than the Simmentaler cross (79.3 ± 12.2 %), Bonsmara cross (76.5 ± 11.1 %) and Nguni herds (86.1 ± 5.8 %). Breed differences (p < 0.05) for weaning weight and preweaning gain were observed (Simmentaler cross > Bonsmara cross > Afrikaner > Nguni). The Nguni cow herd (46.5 ± 5.7 kg/100 kg mated) was more (p < 0.05) efficient than the Simmentaler cross (36.2 ± 5.5 kg/100 kg mated), Bonsmara cross (37.7 kg/100 kg mated) and Afrikaner herds (29.5 ± 5.9 kg/100 kg mated). During the dry winter season steers gained 23.4 ± 1.5 kg from 7 to 12 months of age and from 18 to 24 months of age they gained 20.9 ± 2.0 kg. During the wet summer season steers gained 109.7 ± 1.8 kg from 12 to 18 months and 120.3 ± 4.1 kg from 24 to 30 months of age. The best (p > 0.05) fat classification codes were attained at 30 months of age and the worst (p < 0.05) at 24 months of age. Simmentaler cross steers attained the lowest (p < 0.05) fat classification at all three age classes. At 30 months of age, 15 of the 63 steers slaughtered had 3 or 4 permanent incisors, while 47 steers had 2 permanent incisors. The total amount as well as the percentage kidney and omental fat were the highest (p < 0.05) at 30 months of age and the lowest (p < 0.05) at 24 months. Back fat thickness followed the same pattern. Although breed differences for some meat quality parameters were observed, slaughter age had a much more pronounced effect on meat quality parameters. The percentage cooking loss was the lowest (p < 0.05) at 30 months of age. The meat was also darker (p > 0.05) and more red (p < 0.05) at 30 months than at 18 or 24 months of age. The pH24 was higher (p < 0.05) at 24 (5.68 ± 0.05) and 30 months (5.65 ± 0.03) than at 18 months of age (5.48 ± 0.04). A trained sensory panel only detected that Longissimus muscle samples from 18 month old steers were more tender (p < 0.05) than that from 30 month old steers. Similar results were found for Warner-Bratzler shear force values. Marketing steers at 30 months of age resulted in higher production outputs for all the breed types than marketing weaners. For marketing both weaners and 30 month old steers the Nguni herd produced more marketable kilograms live weight than the Simmentaler cross, the Bonsmara cross and the Afrikaner herds. Different marketing systems suitable to the Arid Sweet Bushveld were identified. Each marketing system is discussed in terms of its application, advantages, disadvantages and adaptability to arid regions. It is maintained throughout that a conservative approach to grazing as well as cattle management is critical to ensure stable production systems in arid regions with erratic rainfall patterns. / AFRIKAANSE OPSOMMING: Die oogmerk van hierdie studie is om wetenskaplik gefundeerde riglyne daar te stel wat die begrip van beesvleis produksie vanaf natuurlike weidings in ariede soetveld streke sal verbeter. Beeste van vier ras tipes wat wissel van groot- tot kleinraam tipes (Simmentaler kruis > Bonsmara kruis > Afrikaner > Nguni) is vergelyk in terme van koeiproduksie en effektiwiteit sowel as die groei prestasie, karkas- en vleiskwaliteit van osse op 18-, 24- en 30-maande ouderdom. Osse wat op 18 en 30 maande ouderdom geslag is, is aan die einde van die nat somerseisoen geslag, terwyl osse wat op 24 maande ouderdom geslag is, aan die einde van die droë winterseisoen geslag is. Die Afrikaner kudde (59.8 ± 9.0 %) het ’n laer (p < 0.05) reproduksietempo as die Simmentaler kruis (79.3 ± 12.2 %), Bonsmara kruis (76.5 ± 11.1 %) en die Nguni kuddes (86.1 ± 5.8 %) gehandhaaf. Ras verskille (p < 0.05) ten opsigte van speenmassas en voorspeense groeitempo’s is waargeneem (Simmentaler kruise > Bonsmara kruise > Afrikaners > Ngunis). Die Nguni koei kudde (46.5 ± 5.7 kg/100 kg gedek) was meer (p < 0.05) effektief as die Simmentalerkruis (36.2 ± 5.5 kg/100 kg gedek), Bonsmarakruis (37.7 kg/100 kg gedek) en die Afrikaner kuddes (29.5 ± 5.9 kg/100 kg gedek). Gedurende die droëwinter seisoen het die osse vanaf 7 to 12 maande ouderdom 23.4 ± 1.5 kg in liggaamsmassa toegeneem en vanaf 18 tot 24 maande ouderdom het hulle 20.9 ± 2.0 kg toegeneem. Gedurende die nat somerseisoen het die osse vanaf 12 tot 18 maande ouderdom 109.7 ± 1.8 kg in liggaamsmassa toegeneem en van 24 tot 30 maande ouderdom het hulle 120.3 ± 4.1 kg toegeneem. Die beste (p < 0.05) vetklassifikasie kodes is op 30 maande ouderdom verkry en die swakste (p < 0.05) op 24 maande ouderdom. Simmentalerkruisosse het by alle ouderdomsgroepe die swakste (P < 0.05) vetklassifikasie kodes behaal. Op 30 maande ouderdom het 15 van die 63 osse wat geslag is 3 of 4 permanente snytande gehad, terwyl 47 osse 2 permanente snytande gehad het. Die totale hoeveelheid sowel as die persentasie nier- en omentumvet was die hoogste (p < 0.05) op 30 maande ouderdom en die laagste (p < 0.05) op 24 maande ouderdom. Rugvetdikte het dieselfde patroon gevolg. Alhoewel rasverskille vir sommige vleiskwaliteitsparameters waargeneem is, het slagouderdom’n groter effek hierop. Die persentasie kookverlies was die laagste (p < 0.05) op 30 maande ouderdom. Die vleis was ook donkerder (p < 0.05) en meer rooi (p < 0.05) op 30 maande ouderdom as op 18 en 24 maande ouderdom. Die pH24 was hoër (p < 0.05) op 24 (5.68 ± 0.05) en 30 maande ouderdom (5.65 ± 0.03) as op 18 maande ouderdom (5.48 ± 0.04). Behalwe vir sagtheid, is geen ander ras- of slagouderdomsverskille in die longissimus spiermonsters vir enige van die sensoriese eienskappe wat geëvalueer is, waargeneem nie. ’n Opgeleide sensoriese paneel het slegs waargeneem dat die longissimus spiermonsters van 18 maand oue osse sagter (p < 0.05) was as dié van 30 maand oue osse. Soortgelyke resulte is vir die Warner-Bratzler snyweerstand gevind. Die bemarking van 30 maand oud osse het hoër produksie uitsette vir al die ras tipes opgelewer as die bemarking van speenkalwers. Met die bemarking van beide speenkalf en 30 maand oue osse, het die Ngunikudde meer bemarkbare kilogram lewendige massa as die Simmentalerkruis, die Bonsmarakruis en die Afrikaner kuddes geproduseer. Verskillende bemarkingstelsels wat as geskik vir die Ariede Soet Bosveld beskou word, is geïdentifiseer. Elke bemarking stelsel is in terme van sy toepassing, voor- en nadele asook die toepaslikheid daarvan in ariede streke bespreek. Dit word deurgaans aanbeveel dat ’n konserwatiewe benadering tot beide weidings- en kuddebestuur, krities is om stabiele produksiestelsels in ariede streke met wisselvalige reënvalpatrone te verseker.

Dairy farming is one of the most important agricultural industries in South Africa, and thus improving the performance of dairy cows, with respect to economically important dairy traits, would be beneficial. Selection of dairy cows has traditionally been phenotypic, but new molecular techniques have made it possible to evaluate phenotypic dairy traits at the DNA level, providing the possibility of more accurate selection. The economically important dairy traits, milk production and reproductive performance, are quantitative traits, and are therefore controlled by many genes and the environment. A number of genes have been identified that have been shown to influence economically important dairy traits, including the lep gene. This gene encodes the hormone leptin, which has been proven to regulate feed intake, energy balance, fertility and immune function. A polymorphism has been identified in the lep gene, which may be associated with economically important dairy traits. This study on a South African Jersey herd investigated the possible association of the polymorphism, RFLP-Kpn 21, with milk production and reproductive performance. The lactation records of fifty Jersey cows that completed their first lactation between 1997 and 2004 were collected, and these cows were genotyped for the RFLP-Kpn 21 polymorphism, located at exon 2 of the lep gene. This involved the extraction of DNA from venous blood, using a salting out technique. The extracted DNA was amplified using PCR primers; the reverse primer included a purposeful mismatch. The role of the purposeful mismatch was to create a recognition site for a restriction enzyme (Kpn 21), thus allowing the alleles of the polymorphism to be identified through a restriction digestion protocol. Two alleles were identified, the C- and the Tallele. The genotype of each cow was identified using PAGE. The significance of the genotype effects on the milk production traits and the reproductive performance traits were estimated using the F-statistic provided by a GLM Univariate analysis. In conclusion, no significant effect of the RFLP-Kpn 21 polymorphism was found for milk yield, butterfat and protein percentage, ICP and SPC (p > 0.05), but a possible association with lactose percentage was suggested by the statistical analysis (p < 0.05). Further investigation of South African Jersey cows will be necessary in order for conclusive results to be obtained. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

Incidences of uterine infections in dairy cattle are high between parturition and Day 21 postpartum. Dairy cows with uterine infections are at risk for prolonged periods of days open and multiple services before becoming pregnant. Neutrophils are the first wave of immune system defense against uterine contamination. Neutrophil function seems to be mediated by reproductive hormones and good uterine health is related to properly functioning neutrophils. To elucidate the interaction between reproductive hormones, neutrophils and uterine health in dairy cows the objectives of this research were to evaluate: 1) changes in circulating white blood cell populations during the estrous cycle, 2) the effects of prostaglandin F₂[subscript α](PGF₂[subscript α]) on circulating white blood cell populations and 3) the effects of a two-injection PGF₂[subscript α] regimen on uterine neutrophil and bacterial populations and numbers of days open and services per conception. In the first experiment, the effect of stage of the estrous cycle on plasma neutrophil numbers was evaluated. Neutrophils were observed throughout the entire estrous cycle and numbers were greatest (P<0.05) on Day 14 (mid-cycle), when the corpus luteum was the dominant ovarian structure and plasma progesterone was at its acme. In the second experiment, plasma neutrophil numbers were examined in cows after injections of saline or the PGF₂[subscript α] pharmaceutical product, Lutalyse. Compared to saline, numbers of neutrophils were greater (P<0.05) 4 and 8 hr after Lutalyse injection. In the third experiment, neutrophil numbers were examined after injections of saline, Lutalyse or the PGF₂[subscript α] analog, Estrumate. Compared to saline, numbers of neutrophils did not differ (P>0.10) from cows injected with Lutalyse or Estrumate. In the fourth experiment, uterine bacterial populations and numbers of neutrophils were quantified in cows treated with Lutalyse or saline on Days 0 and 14 or 14 and 28 postpartum. Compared to saline, Lutalyse treatment decreased (P<0.05) total bacteria present in the uterus and increased (P<0.05) the number of uterine neutrophils. In experiment five, numbers of days open and services per conception were evaluated in cows treated with Lutalyse or saline on Days 0 and 14 or 14 and 28 postpartum. Compared to saline, Lutalyse decreased days open (154.7 ± 14.1 vs. 120.1 ± 7.9 days, respectively; P<0.05) and services per conception (3.0 ± 0.4 vs. 2.3 ± 0.2 services, respectively; P=0.09). These results suggest PGF₂[subscript α] treatment can increase neutrophil and depress bacterial cell populations in favor of the dairy cow's uterine health and may explain why fertility is improved when PGF₂α is administered early in the postpartum period. / Graduation date: 2012

A positive phenotypic correlation between milk protein percentage and reproductive performance in dairy cattle, especially during early lactation has been recently reported. The objective of this study was to quantify the relationship between milk protein percentage and different measures of fertility in Irish, seasonal calving, dairy cattle using data from experiments comparing strains of Holstein-Friesian cows under different feeding systems. The relationships between body condition score, milk production and fertility were also investigated. The data used in this study consisted of 584 lactation records over a 5-yr period. Principal component analysis and logistic regression was used to study the relationship between milk protein percentage and fertility performance of the cow. Greater milk protein percentage during the first 60 days post-calving was associated with better reproductive performance. The probability of a cow being submitted in the first 21 days of the breeding season increased with increased milk protein percentage during early lactation. Similarly, the probability of a cow becoming pregnant to its first service or to the whole breeding season also increased. Cows were classified as either high or low milk protein percentage based on their protein percentage over the whole lactation. Cows in the high milk protein group had a 7% greater conception rate compared to cows in the low protein percentage group. In conclusion, cows with higher protein percentage, especially during early lactation are submitted earlier in the breeding season, and have a higher conception rate. Physiologically, the shortage of glucose caused by negative energy balance restricts the synthesis of milk protein in the udder. On the other side, negative energy balance also causes the reduction of IGF-I, LH and oestradiol, which consequently delay the ovarian follicular development and finally reduces fertility. Therefore, there is a biological explanation for the association between milk protein percentage and fertility performance.

The aim of this thesis is to evaluate chosen influences on the extent of reproduction of randomly chosen milk cows that are bred in the same conditions. The chosen influences such as breed, age of the first calving, time of year of calving and level of yield were observed within breeds of Czech Fleckvieh and Holstein cattle. Evaluation was carried out in ZOD "Podhradí" Choustník company, specifically in Budislav farm. 191 cows were chosen for the basic sample. 95 of them were Holstein cattle and 96 were Czech mottled cattle. Chosen influences were evaluated according to data gained from the set of milk yield inspections. A statistically significant difference was observed between Czech ticks and Holstein cows in the length of service period per second and first lactation where Holstein cows have a second lactation period longer than 44 days (P <0.001). Evaluation of first calving age did not show any influence on the level of reproduction neither within Czech Fleckvieh nor within Holstein cattle. During the annual evaluation, it emerged that Holstein cows calved in spring and winter have significantly bigger insemination interval compared to cows that were calved during summer or autumn. This fact was also proven by correlation analysis. This analysis also confirmed the relation between annual period and insemination interval Rxy=0,21(P<0,05). The correlation analysis also proved the relation between annual period and service period as well as interim of Czech Fleckvieh cattle Rxy= 0,327 (P<0,01). Statistically significant influence was not proven within Holstein cattle. Correlation analysis only pointed out the relation between yield and service period Rxy=0,213 (P<0,05). Unlike Holstein cattle, gradual increase of service period figures and interim depending on yield was noticed. Breeding cows milking more that 7,5 thousand kg of milk per lactation had service period of 132 days (P<0,01) and interim 407 days (P<0,01). Economical losses caused by prolonged interim during monitored herd of cattle reached 400.490 CZK in year of 2016.