References of "Hanzen, Christian"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailStudy on reproductive performance of Holstein x Lai Sind crossbred heifers and cows at smallholdings in Ho Chi Minh City, Vietnam.
Nguyen-Kien, Cuong; Nguyen, Van Khanh; Hanzen, Christian ULg

in Tropical Animal Health and Production (2017), 49

The reproductive performance of Holstein x Lai Sind crossbred dairy heifers and cows was evaluated at small-holdings in Ho Chi Minh City (HCMC). The data of 232 heifers and 244 cows (261 lactations) from ... [more ▼]

The reproductive performance of Holstein x Lai Sind crossbred dairy heifers and cows was evaluated at small-holdings in Ho Chi Minh City (HCMC). The data of 232 heifers and 244 cows (261 lactations) from 35 small dairy farms was collected over a 2-year period, from 2013 to 2014. The overall mean for age at first service (AFS), days between first and last service (DFLS), and age at conception (AC) of heifers was 479 (±80), 38 (±80), and 517 (±114) days, respectively. Average number of services per conception (NSC), conception rate (CR), and conception rate at first ser-vice (CRFS) was 1.8 (±1.4), 55, and 58%, respectively. The overall mean for the waiting period (WP), DFLS, and days open (DO) of cows was 109 (±52), 133 (±114), and 242 (±129) days, respectively. The mean for NSC, CR, and CRFS was 4.3 (±2.7), 23, and 14%, respectively. A very sig- nificant decrease in AFS and AC according to the year of birth, and a significant increase in AFS according to body weight at first insemination (>320 kg) were observed. The CRFS of heifers inseminated in 2013 was significantly higher than in 2014. Monthly mean CR in heifers and cows was negatively correlated with THI. The WP, DFLS, DO, and NSC of cows significantly decreased according to the year of calving. Cows that calved in rainy season had a significant-ly longer WP than in dry season. The occurrence of postpar-tum (PP) diseases was accompanied by an increase in WP, DO, and NSC. A decrease in body condition score (BCS) between calving and 60th day (C60) and also between 60th and 120th day of lactation resulted in a significant increase in WP and DO. A decrease in BCS between C60 was also ac-companied by a considerable reduction in CRFS of cows. Season and BCS at insemination had a significant effect on NSC and CR of cows. Reproductive performance was satis-factory for heifers, but poor for cows. Losses of BCS during the first months of lactation and at insemination were the major risk factors for this poor performance. Moreover, the season had a more negative effect on fertility in cows than in heifers. [less ▲]

Detailed reference viewed: 27 (2 ULg)
Full Text
See detailProduction laitière et santé mammaire (Bio Ingénieurs)
Hanzen, Christian ULg

Learning material (2016)

Ce cours de 2 heures s'inscrit dans cadre du module "Production laitière par le ruminant" dispensé aux étudiants de master bio-ingénieur en sciences agronomiques. Les objectifs spécifiques ont été définis ... [more ▼]

Ce cours de 2 heures s'inscrit dans cadre du module "Production laitière par le ruminant" dispensé aux étudiants de master bio-ingénieur en sciences agronomiques. Les objectifs spécifiques ont été définis en accord avec le professeur Yves Beckers co-responsable du module. Ce cours a pour objectif général de définir la mammite, ses conséquences, ses signes d'alerte au niveau de l'individu et du troupeau, son approche diagnostique, ses facteurs de risque au niveau individuel et d'élevage et ses grandes lignes d'approche thérapeutique. [less ▲]

Detailed reference viewed: 411 (103 ULg)
Full Text
Peer Reviewed
See detailThe effects of timing of insemination and GnRH treatment on pregnancy rates of N’Dama females after induction of oestrus with progestin
Okouyi M’foumou W’otari, Marcel; Hanzen, Christian ULg

in Revue d'Elévage et de Médecine Vétérinaire des Pays Tropicaux (2016), 69(2), 73-78

The aim of this clinical trial was to quantify the results of pregnancy after treating trypanotolerant N'Dama female cattle (n=168) using a CIDR® (1.38g of progesterone) inserted for seven days. An ... [more ▼]

The aim of this clinical trial was to quantify the results of pregnancy after treating trypanotolerant N'Dama female cattle (n=168) using a CIDR® (1.38g of progesterone) inserted for seven days. An intramuscular (IM) PG injection (500µg of cloprostenol) was administered two days before removal of the device. Subsequently, an IM injection of 400UI of eCG was administered when the device was removed. The animals were inseminated respectively 48 (Group 1) and 72 hours (Group 2) after removal of the CIDR®. In both groups, half the animals were treated with 4.2µg of buserelin acetate and the other half with 1ml of physiological saline. Four protocols were thus tested: CIDR-PG-eCG/IA48h, CIDR-PG-eCG/IA48h/GnRH+, CIDR-PG-eCG/IA72h, and CIDR-PG-eCG/IA72h/GnRH+. A pregnancy diagnosis has been done by echography 45 to 60 days after insemination. The average pregnancy rate was 37.5% (n=168). That of the adult cows (43.2%, n=111) was significantly (P < 0.03) higher than that of the heifers (26.3%, n=57). The pregnancy rate observed in animals in Group 2 (48.8%) was significantly higher (P < 0.002) than that observed in the animals in Group 1 (26.2%). Physiological condition and the injection of GnRH at the time of insemination had no significant impact on the pregnancy rate. The hormonal protocol using CIDR-PG-eCG (400UI) and a timed artificial insemination 72 h later improves the pregnancy rates in the N’Dama female. [less ▲]

Detailed reference viewed: 28 (3 ULg)
Full Text
Peer Reviewed
See detailEffects of equine chorionic gonadotropin (eCG) on the sexual behaviour and ovulatory characteristics of female african N'Dama cattle.
Okouyi, M.W. Marcel; Hanzen, Christian ULg

in Revue de Médecine Vétérinaire (2016), 167(7-8), 211-215

This paper evaluated the effects of eCG on the characteristics of oestrus and ovulation after heifers and cows had been synchronised following vaginal administration of progesterone for seven days ... [more ▼]

This paper evaluated the effects of eCG on the characteristics of oestrus and ovulation after heifers and cows had been synchronised following vaginal administration of progesterone for seven days (Controlled Internal Drug Released) and a PGF2α injection two days after the end of treatment. The animals were randomly split into a non-treated control group (n=26) and four groups with increasing doses of eCG: 300 IU (n=25), 400 IU (n=24), 500 IU (n=23) and 600 IU (n=23), which were injected on the day of CIDR withdrawal. The animals were then followed (24 hours a day) for six days. Oestrus was confirmed on the basis of identifying 'standing oestrus', i.e., when the cow stood to be mounted. Seven to ten days after the CIDR® was withdrawn, the animals were slaughtered, and their ovaries were examined to identify and count the number of follicular and/or luteal structures. The onset of heat was 48.6 ± 5.3 hours after eCG injection, and the average length of oestrus was 9.9 ± 2 hours. The eCG dosage had no significant effect on these two parameters. In contrast, the observed rate of oestrus was significantly (p<0.05) higher in animals that had been treated (70.8 to 84.0%) in comparison with animals that had not been treated (50%). Similarly, the ovulation rate was significantly (p<0.05) higher in treated animals (88.0 to 100%) than in untreated animals (73.1%). The percentage of animals that presented multiple ovulations increased significantly (p <0.001) with the dosage of eCG administered (4.5% to 36.4%). [less ▲]

Detailed reference viewed: 29 (13 ULg)
Full Text
See detailPostpartum anoestrus in Holstein x Lai Sind crossbred dairy cows in small farms of Ho Chi Minh City
Nguyen, Kien Cuong; Hanzen, Christian ULg

in Vo Thi, Tra; Ho Thi Kim, Hoa; Le Thanh, Hien (Eds.) et al Proceedings of the 19th Federation of Asian Veterinary Association Congress (2016, September 08)

The aim of the study was to assess the prevalence of postpartum (PP) anestrus and the effect of factors on this prevalence in small dairy farmers. The data of 419 calvings and PP periods from 35 small ... [more ▼]

The aim of the study was to assess the prevalence of postpartum (PP) anestrus and the effect of factors on this prevalence in small dairy farmers. The data of 419 calvings and PP periods from 35 small dairy farms was collected during two years 2013 and 2014. Cows which failed to express estrus signs by day 60th after calving were submitted for manual palpation and transrectal ultrasonography to evaluate ovarian state. 49.9% of observed cows were not detected in estrus by the stockman during the first 60 days PP. The prevalence of type I, type II, cystic, pyometral and detective anestrus (or subestrus) was 27.0, 6.7, 0.5, 0.7 and 15.0%, respectively. The presence of dystocia or uterine infection was accompanied by an increase in risk of the type I anestrus (36.7% vs 23.1%, P = 0.005; 41.4% vs 21.5% , P < 0.001, respectively). Cows with a low BCS at calving (< 3) or at the 30th day PP (< 2.5) significantly showed a high risk of the type I anestrus than cows with a medium or high BCS at the same periods. In conclusion, the anestrus type I and subestrus mainly contriduted to high risk of PP anestrus in small dairy farms in HCMC. The dystocia, uterine infection, low BCS at calving and at day 30th PP constituted major causes of the type I anestrus. [less ▲]

Detailed reference viewed: 16 (1 ULg)
Full Text
See detailBetween bovine milk production and reproduction : the challenge.
Hanzen, Christian ULg; Nguyen Kien, Cuong

in Vo Thi Tra; Ho Thi Kim, Hoa; Le Thanh, Hien (Eds.) et al Proceedings of the 19th Federation of Asian Veterinary Association Congress (2016, September 07)

Huge differences in dairy milk production can be observed around the world. They can be explained by differences in genetic, nutritional resources and management including the capacities of the farmers ... [more ▼]

Huge differences in dairy milk production can be observed around the world. They can be explained by differences in genetic, nutritional resources and management including the capacities of the farmers and veterinarian to prevent and treat the different pathologies inducing of the wellbeing of the animals. According to the world market of milk production, the challenge of each farm is not only to produce a milk of quality but also to reduce the costs of milk production by improving reproductive performances. Anywhere in the world we are responsible to encourage and develop a sustainable approach of milk production and agriculture development according to his three pillars: environment, economic and social. Our presentation will present (1) the mains figures about the milk production in the world, (2) the definitions and prevalences of the different periods involved in the reproductive life of a cow, (3) the nutritional, genetic and pathological factors involved in the milk production on general and more specifically in reproduction (dystocia, placental retention, uterine infections, postpartum anoestrus), the relationships between these factors, (‘) the state of art of the definition, methods of diagnostic state of art of the main reproduction pathologies (dystocia,) affecting the dairy cows during the waiting and reproduction periods. [less ▲]

Detailed reference viewed: 80 (7 ULg)
Full Text
Peer Reviewed
See detailLe sexe ratio chez les bovins : facteurs de variation
Hanzen, Christian ULg; Chastant-Maillard, Sylvie; Rao, Anne-Sophie ULg et al

in Point Vétérinaire (Le) : Expert Rural (2016), 367

Le sexe ratio secondaire, défini comme la proportion de mâles à la naissance, est de 52% chez les bovins, avec des variations selon les populations étudiées de 46 à 57%. Il est plus élevé lors des ... [more ▼]

Le sexe ratio secondaire, défini comme la proportion de mâles à la naissance, est de 52% chez les bovins, avec des variations selon les populations étudiées de 46 à 57%. Il est plus élevé lors des premières étapes du développement embryonnaire, et les conceptus mâles meurent proportionnellement plus au cours de la gestation que les conceptus femelles. Les facteurs de variation potentiels sont nombreux, mais peu d’effets sont unanimement observés. L’effet de la parité ou du statut social de la vache ne sont pas clairement démontrés. Les ovulations sur l’ovaire droit donneraient naissance à une plus forte proportion de mâles ; le rôle du taureau est probablement limité et la répétabilité du sexe du veau d’une gestation à l’autre est faible. Le moment de l’insémination par rapport à l’ovulation ne semble pas avoir d’influence alors qu’il aurait pu constituer un moyen de maîtrise assez simple à mettre en œuvre. [less ▲]

Detailed reference viewed: 37 (2 ULg)
Full Text
Peer Reviewed
See detailLe sexe ratio chez les bovins : mécanismes potentiels.
Hanzen, Christian ULg; Chastant-Maillard, Sylvie; Rao, Anne-Sophie ULg et al

in Point Vétérinaire (2016), 367

Le sexe ratio (proportion de veaux mâles nés) peut varier sous l’effet de nombreux facteurs (voir l’article dans un numéro précédent). Les mécanismes d’action biologiques expliquant ces variations sont ... [more ▼]

Le sexe ratio (proportion de veaux mâles nés) peut varier sous l’effet de nombreux facteurs (voir l’article dans un numéro précédent). Les mécanismes d’action biologiques expliquant ces variations sont potentiellement nombreux. Tout d’abord l’origine des ovocytes (le sexe ratio varie entre l’ovaire droit et l’ovaire gauche), alors que l’influence de la corne qui héberge le fœtus ne semble pas avoir d’influence. Les spermatozoïdes porteurs du chromosome Y seraient plus rapides mais moins résistants que les spermatozoïdes porteurs du X, expliquant l’influence du moment de l’insémination par rapport à l’ovulation (influence néanmoins non systématiquement observée). La glycémie de la mère orienterait le sexe ratio par un impact sur la maturation ovocytaire et sur le début du développement embryonnaire, les embryons montrant des différences dans leur métabolisme et dans leur résistance au stress. Néanmoins, ces mécanismes restent hypothétiques et mal élucidés. [less ▲]

Detailed reference viewed: 37 (1 ULg)
Full Text
See detailPathologies of the puerperium in the cow. How to define, diagnose, understand and treat.
Hanzen, Christian ULg

Learning material (2016)

The aim of this conference is to answer to the 8 following questions In which economical context are we working ? Is puerperium important for the reproductive performance of the cow ? How to define the ... [more ▼]

The aim of this conference is to answer to the 8 following questions In which economical context are we working ? Is puerperium important for the reproductive performance of the cow ? How to define the pathologies of the puerperium ? What’s the prevalence of these pathologies ? How to diagnose the pathologies of the puerperium ? When to detect these pathologies ? What kind of relations exist between these pathologies ? How to treat these pathologies ? [less ▲]

Detailed reference viewed: 162 (3 ULg)
Full Text
See detailContribution à l'optimisation technico-économique des élevages laitiers en Wallonie : l'intervalle vêlage
Dalcq, Anne-Catherine ULg; Beckers, Yves ULg; Dogot, Thomas ULg et al

Conference given outside the academic context (2016)

Au cours des dernières décennies, l’intervalle vêlage des vaches laitières a eu tendance à s’allonger au niveau mondial, européen et belge. Les causes sont multiples : évolution du système de production ... [more ▼]

Au cours des dernières décennies, l’intervalle vêlage des vaches laitières a eu tendance à s’allonger au niveau mondial, européen et belge. Les causes sont multiples : évolution du système de production laitière, augmentation du niveau de production,… Les conséquences sont nombreuses également mais se traduisent-elles par un impact économique pour l’éleveur laitier ? La recherche présentée aujourd’hui se base sur près de 1800 bilans comptables de 400 exploitations laitières, fournis par le service technico-économique de l’Association Wallonne de l’Elevage, entre 2007 et 2014, pour déterminer l’impact économique de la durée de l’intervalle vêlage et définir l’optimum technico-économique de ce paramètre de management. Faut-il garder en tête « le veau par vache et par an » ou est-il intéressant économiquement d’allonger la période entre deux vêlages pour une même vache ? L’étude révèle qu’il y a bien une relation entre l’intervalle vêlage et les résultats économiques d’une exploitation. De plus, il n’y aurait pas un seul optimum d’intervalle vêlage mais plusieurs, dépendant du type d’exploitation et plus particulièrement du mode d’alimentation. L’optimum de l’intervalle vêlage a tendance à être plus court pour les exploitations à alimentation plutôt intensive et plus long pour les exploitations à alimentation plutôt extensive. Cependant il ne s’agit que de tendances observées, un travail plus approfondi doit encore être réalisé pour confirmer ces tendances et définir des objectifs plus précis à poursuivre pour maximiser la rentabilité de son exploitation. [less ▲]

Detailed reference viewed: 134 (5 ULg)
Full Text
See detailChoisir le sexe de son veau. Est-ce possible et comment ?
Hanzen, Christian ULg

Conference given outside the academic context (2016)

Le but de ces deux heures de formation continue pour les vétérinaires est de(1) énoncer les facteurs propres à l’animal et à l’environnement susceptibles d’influencer le sexe ratio, (2) d’en expliquer les ... [more ▼]

Le but de ces deux heures de formation continue pour les vétérinaires est de(1) énoncer les facteurs propres à l’animal et à l’environnement susceptibles d’influencer le sexe ratio, (2) d’en expliquer les mécanismes d’effet et (3) de recommander une utilisation raisonnée du sperme sexé. [less ▲]

Detailed reference viewed: 439 (17 ULg)
Full Text
Peer Reviewed
See detailMediation analysis to estimate direct and indirect milk losses associated with bacterial load in bovine subclinical mammary infections
Detilleux, Johann ULg; Theron, Léonard ULg; Duprez, Jean-Noël ULg et al

in Animal (2016)

Milk losses associated with mastitis can be attributed to either effects of pathogens per se (i.e. direct losses) or to effects of the immune response triggered by the presence of mammary pathogens (i.e ... [more ▼]

Milk losses associated with mastitis can be attributed to either effects of pathogens per se (i.e. direct losses) or to effects of the immune response triggered by the presence of mammary pathogens (i.e. indirect losses). Test-day milk somatic cell counts (SCC) and number of bacterial colony forming units (CFU) found in milk samples are putative measures of the level of immune response and of the bacterial load, respectively. Mediation models, in which one independent variable affects a second variable which, in turn, affects a third one, are conceivable models to estimate direct and indirect losses. Here, we evaluated the feasibility of a mediation model in which test-day SCC and milk were regressed toward bacterial CFU measured at three selected sampling dates, 1 week apart. We applied this method on cows free of clinical signs and with records on up to 3 test-days before and after the date of the first bacteriological samples. Most bacteriological cultures were negative (52.38%), others contained either staphylococci (23.08%), streptococci (9.16%), mixed bacteria (8.79%) or were contaminated (6.59%). Only losses mediated by an increase in SCC were significantly different from null. In cows with three consecutive bacteriological positive results, we estimated a decreased milk yield of 0.28 kg per day for each unit increase in log2-transformed CFU that elicited one unit increase in log2-transformed SCC. In cows with one or two bacteriological positive results, indirect milk loss was not significantly different from null although test-day milk decreased by 0.74 kg per day for each unit increase of log2-transformed SCC. These results highlight the importance of milk losses that are mediated by an increase in SCC during mammary infection and the feasibility of decomposing total milk loss into its direct and indirect components. © The Animal Consortium 2016 [less ▲]

Detailed reference viewed: 44 (3 ULg)
Full Text
See detailLes infections utérines chez la vache : quels diagnostics pour quels traitements ?
Hanzen, Christian ULg

Learning material (2016)

Ce cours de 2heures a pour objectif spécifiques de rendre les étudiants capables de définir les 4 types d’infections utérines décrites chez la vache, d’en expliquer brièvement la pathogénie, de faire le ... [more ▼]

Ce cours de 2heures a pour objectif spécifiques de rendre les étudiants capables de définir les 4 types d’infections utérines décrites chez la vache, d’en expliquer brièvement la pathogénie, de faire le choix propédeutique optimal pour en faire le diagnostic, d’en comprendre les avantages et inconvénients, d'adapter la stratégie thérapeutique qu’elle soit de nature hormonale ou anti-infectieuse, à la situation clinique de l’animal. [less ▲]

Detailed reference viewed: 355 (4 ULg)
Full Text
See detailBases histo-physio-anatomiques et propédeutique de l’appareil génital de la vache
Hanzen, Christian ULg

Learning material (2016)

Cours donné à l’attention des étudiant(e)s de 3ème année en médecine vétérinaire de l'Université Saad Dahlab de Blida (Algérie) à l'Institut des Sciences Vétérinaires le 20 janvier 2016.

Detailed reference viewed: 263 (2 ULg)
Full Text
Peer Reviewed
See detailRisk Factors of Clinical and Subclinical Endometritis in Cattle: a Review.
Adnane, Mounir; Kaidi, Rachid; Hanzen, Christian ULg et al

in TURKISH JOURNAL OF VETERINARY AND ANIMAL SCIENCES (2016)

Detailed reference viewed: 52 (2 ULg)