The primary objective of this research was to study the effects of breed, age, season, and their interactions on semen morphological characteristics. The study was done on 329 bulls (271 Friesland and 58 Jersey) aged 12, 24, 36,48, 60, 72, 84, 96 and> 96 months. The collection of semen was carried out using the artificial vagina method in all four seasons of the year. Spermatozoa were screened for the percentages normal sperm, percentage and total major defects such as knobbed acrosome, pyriform, abnormal lose head, dag defects, nuclear vacuole, degenerative heads, mid-piece reflexes, percentages and total minor defects such as normal lose heads, distal droplets, curled end-piece, lose acrosome. Statistical analyses of the data were done using the general linear model (GLM) procedure of the Statistical Analyses System (SAS, 1999). The results of the study indicate that breed did not significantly affected the percentage normal sperm and percentage major sperm defects, but significantly affected the percentage minor defects (P = 0.01). The Least square means (LSM±SE) for the percentage normal sperm, major defects and minor defects in Friesland and Jersey bulls were 80.6 ±1.06%; versus 78.9±2.31 %; 14.8±0.90% versus 15.0± 2.62%, 5.1±0.43% versus 7.6±0.94%, respectively. The results obtained show that the prevalence of sperm defects that differed significantly between breeds was higher in Jersey bulls compared to Friesland bulls. The results of the study indicated the percentage of normal sperm to differ (P = 0.01) with season. The percentage of normal sperm during the summer, autumn, winter and spring, were 72.8±1.6%, 79.4±2.2%, 82.5±2.4% and 84.4±2.4% respectively. Season also affected the percentage of major defects (P = 0.01) and percentage of minor defects (P = 0.03). The results demonstrate that even though there was a higher variation in sperm morphology with season, better sperm morphology was recorded in spring and winter than summer and autumn. Results also indicate the percentage of normal sperm (P = 0.05) and major defects (P = 0.01) to be affected significantly by age. On the other hand, the percentage of minor defects did not differ significantly with age. Bulls of 36-48 months of age showed better semen quality than bulls older than 72 months and bulls younger than 36 months. The percentage of major defects, particularly the incidence of major defects such as knobbed acrosomes, pyriforms, dag defects and broken flagella were significantly affected by the interaction between age and breed (P = 0.05) and age and season (P = 0.05). There was an increase in the susceptibility to these sperm defects in Jersey bulls with an increase in age, while no variation was observed in Friesland bulls. With age and season combined, young bulls recorded poor semen morphology during winter, while old bulls showed poor morphology during summer. In conclusion, the study suggested that breed, age and season and their interactions are important sources of variation in sperm morphology. For a successful AI programme, semen collection should be done at the age of 36-48 months for both breeds. It is therefore recommended that age, breed and season should be given urgent attention in any bull management system employed in South Africa in order to obtain the best semen quality. / Dissertation (M Inst Agrar (Animal Production))--University of Pretoria, 2003. / Animal and Wildlife Sciences / unrestricted

Alternatives to antibiotic growth promoters have been widely exploited due to concerns about antimicrobial resistance. These feed additives improve growth, in part, by modulating intestinal microbiota. However, their impact on male reproductive performance is not well elucidated. Therefore, the objective of this study was to evaluate the impacts of a yeast fermentation product (YP) and Bacillus subtilis on rooster semen quality and microbiota. Dietary supplementation of YP linearly increased the concentration of yeast and bacteria in semen, whereas it linearly decreased sperm motility, suggesting that bacteria attached to yeast were excreted from the gut, contaminated semen at the cloaca and then decreased sperm movement. However, direct in vitro exposure of semen or dietary supplementation with B. subtilis did not affect semen quality or seminal concentration of this bacterium, likely because Bacillus naturally occur in semen. In conclusion, unlike B. subtilis, dietary YP can alter semen quality by altering semen microbiota.

The objectives were to: 1) determine if im treatments of Lutalyse expedited the training of sexually inexperienced boars for semen collection and increased spermatozoal output, and 2) determine the effects of dietary L-carnitine supplementation on boar libido, semen quality, sperm production, and maintenance of sperm motility during liquid storage. Experiment 1 utilized lean-type, terminal-line boars (National Pig Development, Roanoke Rapids, NC) (n = 40; 177.4 ± 2.4 d of age and 112.8 ± 2.0 kg body weight) that had not previously experienced natural mating. Boars were individually moved twice weekly for 6 weeks (total of 12 training sessions) to a semen collection room equipped with an artificial sow. Upon entering the semen collection room, boars received in treatments of either deionized water (4 mL, n = 10) or Lutalyse at doses of 5 mg (n = 10), 10 mg (n = 10), or 20 mg (n = 10), and subsequently received a libido score of 1 to 5 (1 = no interest in the artificial sow; 5 = mounting the artificial sow and allowing semen collection). The percentages of boars successfully trained for semen collection during the experimental period were similar (P > 0.05) for controls (20%) and boars receiving 5 mg (30%), 10 mg (20%), or 20 mg (10%) of Lutalyse. Average libido score for boars receiving 10 mg Lutalyse (2.35 ± 0.08) was greater (P < 0.05) than for controls (2.14 ± 0.06). Libido score for the 20 mg treatment group were (1.78 ± 0.06) lower (P < 0.05) compared to the other treatment groups. Characteristics of ejaculates (volume, gel weight, sperm concentration, total spermatozoa) from control boars and boars treated with Lutalyse at doses of 5, 10, or 20 mg were similar (P > 0.05). For Exp. 2, the same group of boars was utilized in two similar trials (Trial 1, 1a, 1b: n = 9 for control and L-carnitine-treated boars; Trial 2, 2a, 2b: n = 10 for control and L-carnitine-treated boars). Boars were fed a fortified, corn and soybean meal-based diet at a rate of 2 kg/d. Boars that were randomly selected for L-carnitine treatment received the same diet mixed with L-carnitine to achieve supplementation of 500 mg/d. For 16 wk, semen was collected weekly via the gloved hand method and was analyzed for gel-free volume, gel weight, sperm concentration, sperm per ejaculate, and characteristics of sperm motility. Time to ejaculation (reaction time), duration of ejaculation, and number of false mounts were also recorded for each collection. Trials 1a and 2a were conducted during weeks 16 and 17 for each respective trial. Boars were collected once on 4 consecutive days, allowed 4 d of rest, and then collected again, to estimate daily spermatozoal production. At the end of 16 wk, a semen sample was also processed and extended in Beltsville Thawing Solution (BTS) to achieve a dilution of 3 x 109 spermatozoa/100 mL-dose for Trials 1b and 2b. The extended semen was stored in plastic bottles at 18°C and motility was evaluated daily for 7 d post collection. L-carnitine supplementation for 16 wk had no effects on semen volume, gel weight, total number of sperm cells per ejaculate, reaction time, or sperm motility (P > 0.1). Boars receiving the L-carnitine-supplemented diet displayed an increase in the number of false mounts before ejaculating and an increase in sperm concentration (P < 0.05) in Trial 2. A treatment by week interaction was detected for sperm concentration in Trial 2 (P < 0.005). Increased sperm concentrations in L-carnitine-treated boars were demonstrated after only one week of feeding the respective diets. Given that the production of a mature sperm cell requires 7 to 8 wk in boars, it is therefore difficult to conclude that differences in sperm concentration were due solely to treatment. Daily spermatozoal production was similar between control boars and boars supplemented with L-carnitine (P > 0.1) for both Trials 1a and 2a. L-carnitine supplementation did not affect percent motility in Trials 1b and 2b or sperm progressive motility in Trial 2b during 7 d storage (P > 0.1). A treatment by day interaction was determined for sperm velocity (P < 0.05) in Trial 2b. L-carnitine supplementation decreased mean sperm velocity significantly after 2 d of storage. Overall, L-carnitine had no beneficial effects on boar libido, semen quality, sperm production, or maintenance of sperm motility during liquid storage. However, Lutalyse increased libido scores, but did not affect the number of boars trained for semen collection or number of spermatozoa ejaculated. / Master of Science

No Brasil, assim como em outros países tropicais, a criação de bovinos é feita de maneira extensiva e, portanto é suscetível às intempéries climáticas. Esse tipo de criação pode levar ao estresse térmico, mesmo em animais zebuínos. Sob condições de estresse térmico é possível a ocorrência de degeneração testicular, e por isso, há a procura por animais tolerantes ao calor. Desta maneira, este trabalho objetivou a avaliação da tolerância ao calor de touros da raça Brahman utilizando o teste de tolerância ao calor, e também a análise da qualidade seminal relacionada à disponibilidade de sombra nos pastos. Para tal, foram utilizados 10 touros da raça Brahman com idades entre 24 e 30 meses. Duas semanas antes do início das análises, três amostras de sêmen foram colhidas de cada animal para o nivelamento biológico do sêmen, e então os touros foram separados em dois grupos: 5 touros foram alocados em pasto com disponibilidade de sombra enquanto 5 touros foram alocados em pasto sem qualquer tipo de sombra. O teste de tolerância ao calor foi realizado em três dias consecutivos típicos de verão, e as colheitas de sêmen foram realizadas em 14 dias durante 2 meses, totalizando 4 colheitas. Anteriormente a todas as colheitas foram avaliadas a consistência testicular e o perímetro escrotal. As características seminais avaliadas foram volume, aspecto, turbilhonamento, motilidade, vigor e concentração e morfologia espermáticas. Os dados obtidos foram analisados com o pacote estatístico Statistical Analysis System (SAS Institute Inc., 2004). Não houve diferenças estatísticas entre os dois grupos de animais. O resultado do teste de tolerância ao calor mostrou que os animais testados são tolerantes ao calor e apresentam boa capacidade termolítica. / In Brazil, similarly to others tropical countries, bovines are bred under environmental conditions of extensive system. This breed system type may lead to heat stress even on zebu animals. Under heat stress conditions, testicular degeneration can occur and, therefore, there is a search for animals that are heat tolerant. Therefore, the aim of this work was to evaluate the heat tolerance of Brahman bulls using the heat tolerance test and to verify the occurrence of any possible effect of shadow availability on pasture on semen quality. Ten Brahman bulls aging between 24 and 30 months were used in this work. For biological semen evaluation, three semen samples were collected from each animal two weeks before beginning. The bulls were then separated into two groups: 5 animals were allocated on pasture with shadow availability and 5 bulls were allocated on pasture without any kind of shadow. The heat tolerance test were performed in three consecutive typical summer days and the semen samples were collected each 14 days during 2 months, in a total of 4 semen samples per animal. Testicular consistence and scrotal circumference were measured just before every semen collection. The semen\'s characteristics evaluated were volume, aspect, mass movement, motility, straight movement, sperm concentration and morphological exam. Data obtained from experimental proceedings were analyzed by Statistical Analysis System program (SAS Institute Inc., 2004). No difference was observed (P>0.05) in any of the characteristics analyzed when Brahman bulls were maintained on pastures with or without shadow availability. The performance of tested animals on the heat tolerance test shows that these animals are heat tolerant and present good thermolitic ability.

No Brasil, assim como em outros países tropicais, a criação de bovinos é feita de maneira extensiva e, portanto é suscetível às intempéries climáticas. Esse tipo de criação pode levar ao estresse térmico, mesmo em animais zebuínos. Sob condições de estresse térmico é possível a ocorrência de degeneração testicular, e por isso, há a procura por animais tolerantes ao calor. Desta maneira, este trabalho objetivou a avaliação da tolerância ao calor de touros da raça Brahman utilizando o teste de tolerância ao calor, e também a análise da qualidade seminal relacionada à disponibilidade de sombra nos pastos. Para tal, foram utilizados 10 touros da raça Brahman com idades entre 24 e 30 meses. Duas semanas antes do início das análises, três amostras de sêmen foram colhidas de cada animal para o nivelamento biológico do sêmen, e então os touros foram separados em dois grupos: 5 touros foram alocados em pasto com disponibilidade de sombra enquanto 5 touros foram alocados em pasto sem qualquer tipo de sombra. O teste de tolerância ao calor foi realizado em três dias consecutivos típicos de verão, e as colheitas de sêmen foram realizadas em 14 dias durante 2 meses, totalizando 4 colheitas. Anteriormente a todas as colheitas foram avaliadas a consistência testicular e o perímetro escrotal. As características seminais avaliadas foram volume, aspecto, turbilhonamento, motilidade, vigor e concentração e morfologia espermáticas. Os dados obtidos foram analisados com o pacote estatístico Statistical Analysis System (SAS Institute Inc., 2004). Não houve diferenças estatísticas entre os dois grupos de animais. O resultado do teste de tolerância ao calor mostrou que os animais testados são tolerantes ao calor e apresentam boa capacidade termolítica. / In Brazil, similarly to others tropical countries, bovines are bred under environmental conditions of extensive system. This breed system type may lead to heat stress even on zebu animals. Under heat stress conditions, testicular degeneration can occur and, therefore, there is a search for animals that are heat tolerant. Therefore, the aim of this work was to evaluate the heat tolerance of Brahman bulls using the heat tolerance test and to verify the occurrence of any possible effect of shadow availability on pasture on semen quality. Ten Brahman bulls aging between 24 and 30 months were used in this work. For biological semen evaluation, three semen samples were collected from each animal two weeks before beginning. The bulls were then separated into two groups: 5 animals were allocated on pasture with shadow availability and 5 bulls were allocated on pasture without any kind of shadow. The heat tolerance test were performed in three consecutive typical summer days and the semen samples were collected each 14 days during 2 months, in a total of 4 semen samples per animal. Testicular consistence and scrotal circumference were measured just before every semen collection. The semen\'s characteristics evaluated were volume, aspect, mass movement, motility, straight movement, sperm concentration and morphological exam. Data obtained from experimental proceedings were analyzed by Statistical Analysis System program (SAS Institute Inc., 2004). No difference was observed (P>0.05) in any of the characteristics analyzed when Brahman bulls were maintained on pastures with or without shadow availability. The performance of tested animals on the heat tolerance test shows that these animals are heat tolerant and present good thermolitic ability.

Background: A growing body of evidence has found links between endocrine disruptor phthalates and male reproductive disorders, but the mechanisms underlying these relationships are poorly known. Seminal plasma metabolomes may mediate associations of phthalate exposure with impaired semen quality. Objective: To identify seminal plasma metabolomes associated with poor semen quality and evaluate their associations with urinary phthalate metabolites among 660 Chinese adult men. Method: The seminal plasma metabolic profiles were acquired using an untargeted approach based on liquid chromatography-high resolution mass spectrometry. We explored the differences in seminal plasma metabolites between participants with poor and good semen quality and evaluated cross-sectional associations between discriminatory metabolic biomarkers and urinary phthalate metabolites. Results: Differences between poor and good semen quality groups were observed in relation to 25 seminal plasma metabolites, mostly related to the metabolism of polyunsaturated fatty acids (PUFA) and acylcarnitine (all p < 0.05). After adjusting for various confounders and multiple tests, metabolites were all significantly associated with one or more individual sperm quality parameters (motility, concentration, total count, and morphology) (all p < 0.05). Among identified metabolic biomarkers, seminal plasma L-palmitoylcarnitine, linoelaidyl carnitine, and oleic acid were inversely associated with urinary mono-(2-ethylhexyl) phthalate (MEHP), and seminal plasma L-acetylcarnitine was inversely associated with the proportion of di-(2-ethylhexyl)-phthalate metabolites (DEHP) excreted as MEHP in urine (%MEHP) (all p < 0.05). Mediation analysis revealed that oleic acid and L-acetylcarnitine mediated significant proportions (6.7% and 17%, respectively) of the positive associations between urinary DEHP metabolites and the percentage of spermatozoa with an abnormal head. Conclusions: Elevated urinary phthalate metabolites may impact semen quality by causing metabolic disorders of seminal plasma PUFAs and acylcarnitine. These pathways warrant further investigation.

Seminal plasma (SP) is the microenvironment of spermatozoa whose composition reflects semen quality and constitutes an excellent source for detecting non-invasive biomarkers. This study characterizes good vs. poor quality semen using seminal extracellular vesicles coupled proteins and miRNA. Fresh boar semen samples were screened, centrifuged, and SP supernatants were collected for near-infrared spectroscopy (NIRS) analysis. EVs were extracted from SP (SP-EVs), characterized, and those of extremely poor or good sperm quality groups were subjected to proteomics and small RNA sequencing. Significant differences were set for P

<p>Ve&scaron;tačko osemenjavanje (VO) je najznačajnija reproduktivna biotehnologija u<br />intenzivnoj proizvodnji svinja. Efikasan izbor visoko fertilnih genetski superiornih<br />nerastova i visok fertilitet ve&scaron;tački osemenjenih krmača, ima veliki ekonomski uticaj na<br />efikasnost praktične primene ove biotehnologije. Međutim, prethodna istraživanja<br />pokazuju da procena klasičnih parametara fertiliteta ejakulata (koncentracija, ukupan<br />broj, pokretljivost i morfologija spermatozoida) nisu dovoljni pokazatelji fertiliteta i<br />reproduktivne performanse nerastova. Sa druge strane, pokazalo se da je fertilitet<br />ve&scaron;tački osemenjenih krmača, često, niži od onog kod prirodno osemenjenih krmača.<br />Kao osnovni razlog nižeg fertiliteta kod VO krmača, navodi se osemenjavanje sa<br />prekomerno razređenim dozama i/ili dozama dugotrajno čuvanim (3 do 5 dana).<br />Rezultati prethodnih istraživanja ukazuju da komponente semene plazme imaju ključni<br />uticaj na fertilizacioni potencijal spermatozoida in vivo i in vitro, kao i na fiziolo&scaron;ke<br />procese važne za uspe&scaron;nu oplodnju i razvoj embriona u uterusu.<br />Zbog toga je glavni cilj ovog istraživanja bio da se: (a) odredi sadržaj proteina u<br />spermalnoj plazma nerastova koji se koriste za VO na nekoliko komercijalnih farmi<br />svinja u Srbiji, (b) oceni uticaj sadržaja proteina u spermalnoj plazmi na pokretljivost i<br />morfologija spermatozoida u nativnoj i razređenoj spermi, nakon 3 dana čuvanja u<br />razređenom stanju i (c) ispita uticaj intrauterine infuzije spermalne plazme, pre<br />aplikacije klasične VO doze, na fertilitet krmača.<br />Sadržaj proteina u spermalnoj plazmi se kretao između 1% i 6,5%, &scaron;to je<br />ustanovljeno kod 212 uzoraka, dobijenih iz ejakulata 106 nerastova, koji se koriste za<br />VO na 6 farmi u AP Vojvodini. Nizak nivo proteina (1-3.5%, prosečno 2,4%) je<br />ustanovljen kod 69%, a visok nivo proteina (3.6-6.5%, prosečno 4,2%) kod 31%<br />ispitivanih nerastova. Nije ustanovljen značajan (P&gt;0,05) uticaj rase ili starosti nerasta,<br />kao ni godi&scaron;nje sezone, na sadržaj proteina u spermalnoj plazmi. Citomorfolo&scaron;ka<br />svojstva spermatozoida su testirana sistemom CASA i protočnom citometrijom. U<br />nativnoj spermi testiranih nerastova, prosečno je bilo 71% živih, 13% spermatozoida sa<br />o&scaron;tećenim akrozomom i 32% spermatozoida sa morfolo&scaron;kim anomalijama. Volumen<br />ejakulata, koncentracija, ukupan broj i pokretljivost spermatozoida bili su značajno<br />(P&lt;0,01) veći kod nerastova sa visokim, u poređenju sa niskim sadržajem proteina u<br />spermalnoj plazmi. Progresivna pokretljivost - PP (64%) i broj živih spermatozoida - ŽS<br />(66%) bio je značajno veći, dok su broj spermatozoida sa o&scaron;tećenom ćelijskom<br />membranom - OM (19%), akrozomom - OA (29%) i hromozomima - OH (13%) bili<br />značajno (p&lt;0,01) niži u uzorcima sperme sa visokim sadržajem proteina, koji su bili<br />čuvani 72h u razređenju 1:4, od ovih vrednosti kod uzoraka sa niskim sadržajem<br />proteina (PP = 48%, ŽS = 44%, OM = 27% OA = 45% i OH = 22%). Zamena autologne<br />spermalne plazme iz ejakulata sa niskim sadržajem proteina od jednog nerasta, sa<br />homologom spermalnom plazmom iz ejakulata drugog nerasta sa visokim sadržajem<br />proteina, značajno (p&lt;0,01) povećava progresivnu pokretljivost spermatozoida, sa 52%<br />na 65%, kod uzoraka čuvanih 72h u razređenju 1:4. Intrauterina infuzija 30 ml semene<br />plazme, pre aplikacije klasične VO doze, značajno (p&lt;0,05) povećava vrednost<br />pra&scaron;enja (94%) i prosečan broj živo rođene prasadi po leglu (12.3) (p&lt;0,01), u<br />poređenju sa kontrolom grupom krmača (83% i 10.5 prasadi).<br />Na osnovu dobijenih rezultata, može se zaključiti: (1) postoje značajne razlike u<br />sadržaju proteina u spermalnoj plazmi između pojedinih nerastova, (2) uzorci sperme sa<br />visokim sadržajem proteina, imaju veće vrednosti fertilizacionog potencijala<br />spermatozoida, od uzoraka sa niskim sadržajem proteina u spermalnoj plazmi, posle 72h<br />čuvanja u razređenju 1:4 i (3) infuzija spermalne plazme, pre aplikacije klasične VO<br />iv<br />doze, značajno povećava fertilitet tako tretiranih krmača, u poređenju sa kontrolnim<br />krmača. Ovi rezultati pokazuju da određivanje sadržaja proteina u spermalnoj plazmi,<br />može biti korisno sredstvo za predviđanje stepena fertiliteta nerasta, pre njegove<br />upotrebe za VO, kao i da se spermalna plazma može koristi za povećanje fertiliteta<br />ve&scaron;tački osemenjenih krmača. Dobijenim rezultatima su, u potpunosti, potvrđene radne<br />hipoteze i ostvareni postavljeni ciljevi istraživanja.</p>

[Truncated abstract]Judgements of physical attractiveness are thought to reflect evolved preferences for a high quality mate. The central aim of this thesis was to investigate the hypothesis that female preferences are adaptations for finding good quality mates and that faces and bodies signal honest information about mate quality. To date, most human mate preference studies have examined face or body attractiveness alone, and many have created stimuli using computer graphic techniques. Throughout these studies, I endeavoured to maximise the biological relevance of my studies by incorporating both face and body attractiveness, and using photographs of individual participants. Most research on attractiveness has focused on faces or bodies separately, while our preferences have evolved based on both seen together. A fundamental requirement of studying face and body attractiveness independently is that there is no interaction between the two. My first study confirmed that the face and body did not interact when an overall attractiveness judgment was made. I also investigated the independent contributions of rated attractiveness of the face and the body to ratings of overall attractiveness. Face and body attractiveness each made significant independent contributions to overall attractiveness in males and females. For both sexes, facial attractiveness predicted overall attractiveness more strongly than did body attractiveness, and this difference was significant in males. ... This study indicates that although current levels of T covary with male mating success, this effect may not be mediated by women's preferences for visual cues to T levels conveyed in static face or body features. The fourth study in this thesis investigated the phenotype-linked fertility hypothesis, which proposes that females obtain reliable information on male fertility from male expression of sexual traits. A previous study of Spanish men reported that facial attractiveness was positively associated with semen quality. I aimed to determine whether this effect was widespread by examining a large sample of Australian men. I also extended my study to determine whether cues to semen quality are provided by components of attractiveness: masculinity, averageness, and symmetry. I found no significant correlations between semen quality parameters and attractiveness or attractive traits. While male physical attractiveness may signal aspects of mate quality, my results suggest that phenotype-linked cues to male fertility may not be generalised across human populations. Together, these studies challenge current methodologies and theories of preferences for secondary sexual traits as honest signals of mate quality. The findings show that it is important to study human mate preferences in biologically relevant contexts, for example by using photographs of both faces and bodies, to maximise the real life application of results. In addition, the findings suggest that male attractiveness does not signal cues to testosterone or semen quality, although testosterone is associated with mating success. The implications of these findings and possible avenues for future research are discussed.

Tesis por compendio / [ES] Cualquier mejora en el conocimiento de la nutrición y el manejo de los futuros conejos reproductores debe considerarse como prioritario en la producción cunícola. Sin embargo, los principales esfuerzos en investigación se han centrado en estos animales durante la fase de reproducción propiamente dicha. La hipótesis inicial de esta tesis fue que alcanzar un desarrollo temprano adecuado durante la gestación, lactancia, engorde y recría, con la ayuda de programas ajustados de alimentación en algunos de estos períodos, mejoraría el rendimiento reproductivo y la vida útil de los futuros conejos reproductores. Para evaluar esta hipótesis, se llevaron a cabo dos tipos de ensayos, tanto en conejos hembra de líneas maternas como en machos de líneas seleccionadas por velocidad de crecimiento y destinadas a la inseminación artificial. El primero de estos ensayos se centró en los diferentes patrones de crecimiento, desde el nacimiento hasta el final de la fase de recría, y su influencia en la carrera reproductiva y la vida útil del conejo. En el segundo tipo de pruebas, se evaluó el efecto del uso de diferentes dietas o programas de alimentación durante el período de recría en la productividad a corto y medio plazo. Los resultados muestran dos fases importantes en el desarrollo temprano, de acuerdo con sus efectos sobre el rendimiento reproductivo y la vida útil. Mostrar un mayor desarrollo corporal desde el nacimiento hasta los 63 días de vida parece tener una influencia positiva en el grado de madurez y la productividad al comienzo de su vida reproductiva, además de poder mejorar su supervivencia a corto plazo, pero con posibles efectos negativos en la esperanza de vida a largo plazo. Sin embargo, el desarrollo durante el período de recría (desde los 63 días de vida hasta el comienzo de la carrera reproductiva) parece tener un mayor impacto en la productividad y la esperanza de vida de nuestros futuros conejos reproductores. Las hembras más engrasadas en la primera inseminación tuvieron tamaños de camada más pequeños y un mayor riesgo de ser sacrificadas que las magras (P<0.05). Además, los machos que mostraron una mayor ganancia media diaria durante el período de recría tuvieron un número y porcentaje de eyaculados viables más bajos a lo largo de su vida productiva y mayor riesgo de muerte o sacrificio. Estos resultados podrían indicar que la clave para llevar a cabo un desarrollo adecuado durante el período de recría debería basarse tanto en conseguir que los conejos alcancen un grado de madurez apropiado, tanto fisiológica como reproductivamente, así como evitar un excesivo engrasamiento al inicio de su vida productiva. En los ensayos destinados a evaluar los programas de alimentación durante la recría, el uso de una restricción alimentaria en hembras, y especialmente el uso de dietas fibrosas (de 8.5 a 10 MJ ED/kg MS) permiten un desarrollo corporal gradual y adecuado a la edad de cubrición, con suficientes reservas corporales para afrontar el comienzo de la vida reproductiva y mejorando tanto su rendimiento reproductivo como su vida útil. El éxito de estos programas de alimentación de recría depende del momento y la duración de la aplicación de estos, mejorándose con la aplicación de un cambio a un pienso enriquecido energéticamente alrededor del primer apareamiento. En los machos, se observó que un programa de alimentación durante la recría adecuado debería adaptarse a la capacidad de ingesta de estos y a sus necesidades nutricionales en períodos concretos de la recría, consiguiendo así mejoras en algunos parámetros del semen al inicio de su vida reproductiva. En conclusión, tanto un desarrollo temprano adecuado desde la gestación hasta el comienzo de su vida reproductiva, como el uso de programas adecuados de alimentación durante la recría podrían mejorar significativamente el rendimiento reproductivo futuro, así como la esperanza de vida, tanto en conejos he / [CA] Qualsevol millora en el coneixement tant de la nutrició com del maneig dels futurs conills de criança ha de considerar-se com a prioritari en la producció de conills. No obstant açò, els principals esforços en investigació s'han centrat en aquests animals durant la fase de reproducció pròpiament dita. La hipòtesi inicial d'aquesta tesi va ser que aconseguir un desenvolupament primerenc adequat durant la gestació, lactància, engreix i criança, amb l'ajuda de programes ajustats d'alimentació en alguns d'aquests períodes, milloraria el rendiment reproductiu i la vida útil dels futurs conills reproductors. Per a avaluar aquesta hipòtesi, es van dur a terme dos tipus d'assajos, tant en conills femella de línies maternes, com en mascles de línies seleccionades per a la velocitat de creixement i destinades a la inseminació artificial. El primer d'aquests assajos es va centrar en els diferents patrons de creixement, des del naixement fins al final de la fase de criança, i la seua influència en la carrera reproductiva i la vida útil del conill. En el segon tipus de proves, es va avaluar l'efecte de l'ús de diferents dietes o programes d'alimentació durant el període de criança, en la productivitat a curt i mig termini. Els resultats obtinguts semblen indicar que podríem diferenciar dues fases en el desenvolupament primerenc, d'acord amb els seus efectes sobre el rendiment reproductiu i la vida útil. Mostrar un major desenvolupament corporal des del naixement fins als 63 dies de vida sembla tenir una influència positiva en el grau de maduresa i la productivitat al començament de la seua vida reproductiva, a més de poder millorar la seua supervivència a curt termini, però amb possibles efectes negatius en l'esperança de vida a llarg termini. No obstant açò, el desenvolupament durant el període de sembla tenir un major impacte en la productivitat i l'esperança de vida dels nostres futurs conills reproductors. Les femelles més greixades en la primera inseminació van tenir grandàries de ventrada més xicotets (tant nascuts com deslletats) i un major risc de ser sacrificades que les magres (P<0.05). A més, els mascles que van mostrar un major guany mitjà diari durant el període de criança van tenir un nombre i percentatge d'ejaculats viables més baixos al llarg de la seua vida productiva i major risc de mort o sacrifici. Aquests resultats podrien indicar que la clau per a dur a terme un desenvolupament adequat durant el període de criança hauria de basar-se tant a aconseguir que els conills aconseguisquen un grau de maduresa apropiat, per a afrontar els futurs desafiaments productius, com evitar un excessiu greixatge a l'inici de la seua vida productiva. En els assajos destinats a avaluar els programes d'alimentació durant la criança, l'ús d'una restricció alimentària en femelles, i especialment l'ús de dietes fibroses (de 8.5 a 10 MJ ED/kg MS) permeten un desenvolupament corporal gradual i adequat a l'edat de cobriment, amb suficients reserves corporals per a afrontar el començament de la vida reproductiva i millorant tant el seu rendiment reproductiu com la seua vida útil. L'èxit d'aquests programes d'alimentació de criança depèn del moment i la durada de l'aplicació d'aquests, millorant-se amb l'aplicació d'un canvi a un pinso enriquit energèticament al voltant del primer cobriment. En els mascles, es va observar que un programa d'alimentació durant la criança adequat hauria d'adaptar-se a la capacitat d'ingesta d'aquests i a les seues necessitats nutricionals en períodes concrets de la criança, aconseguint així millores en alguns paràmetres del semen a l'inici de la seua vida reproductiva. En conclusió, tant un desenvolupament primerenc adequat des de la gestació fins al començament de la seua vida reproductiva, com l'ús de programes adequats d'alimentació durant la criança podrien millorar significativament el rendiment reproductiu futur, així com l'esperança / [EN] Any improvement on the knowledge of both nutrition and management of the future rabbit breeders should be considered as crucial. However, main research efforts have been focused on animals during reproduction phase. The initial hypothesis of this thesis was that achieving an adequate early development during young rabbits' gestation, lactation, fattening and rearing, with the help of fitted feeding programmes in some of these periods, would be improved reproductive performance and lifespan of the future breeding rabbits. To evaluate this hypothesis, two types of trials, both in rabbit females from maternal lines selected for litter size at weaning and males from paternal lines selected for growth rate and intended on artificial insemination, were carried out. The first of these trials were mainly focused on the different growth patterns, from birth to the end of the rearing age, and their influence on rabbit's reproductive career and lifespan. In a second type of trials, the effect of the use of different diets or feeding programs during the rearing period in the performance in the short- medium-term was evaluated. The results obtained from the evaluation of the different growth patterns trials seem to indicate that, we could differentiate two parts on the early development according to their effects on reproductive performance and lifespan. To show a greater body development from birth to 63 days of life seems to have a positive influence on the maturity degree and productivity at the beginning of their reproductive life, as well as being able to improve their survival in the short-term, but it could be even negative for long-term lifespan. However, the development during the rearing period (from 63 days of life to the beginning of reproduction career) seems to have a higher impact on the productivity and lifespan of our rabbit breeders. Fatter rabbit females at first insemination had smaller litter sizes (born and weaned) and a higher risk of being culled (+13% per positive change in mm of perirenal fat) than lean ones (P<0.05). Also, rabbit males that showed a greater average daily gain during rearing period had a lower number and percentage of profitable ejaculates through it productive life (-10.1 and -4.9% per each 10 g of daily gain increase, respectively; P<0.05) and higher risk of death or culling (+16.2% per each increase in one standard deviation unit on live weight; P<0.05). These results could indicate that the key to carrying out an adequate development during the rearing period should allow the rabbits to reach an appropriate degree of physiological and reproductive maturity to face the future productive challenges, avoiding an excessive fatness at the beginning of their productive life. The use of a feeding restriction in rabbit females, and especially the use of fibrous diets (from 8.5 to 10 MJ DE/ kg DM) lead a gradual and adequate body development at mating, with enough body reserves to face the beginning of reproduction life and improving their whole reproductive performance and lifespan. The success of these rearing feeding programs depends in the moment and duration of application of them and improved with the application of a nutritional flushing around first mating. In rabbit males, it was observed that an adequate rearing feeding program should adapt it to the male's intake capacity and their nutritional requirements rearing period, especially to their high DP needs at the beginning of rearing period or when their requirements were close to maintenance, to improve some semen parameters at the beginning of their reproduction life. In conclusion, both the adequate early development of future rabbit breeders, from their own gestation to the beginning of their reproductive life, and the use of appropriate rearing feeding programs could significantly improve their future reproductive performance, as well as their life expectancy, both in rabbit females and males. / Martínez Paredes, EM. (2019). Rearing programmes for breeding rabbits. Effect of early development and feeding on future reproductive performance of rabbit females and males [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/124969 / Compendio