Experiments were conducted to elucidate mechanisms of increased milk protein percentage in cows fed diets containing steam flaked (SFS) vs dry rolled (DRS) sorghum grains. In experiment 1 treatments were: DRS diet plus duodenal infusion of 30% sodium acetate (DA), or SFS diet plus duodenal water infusion (SFS). In the experiment 2 the DRS diet plus duodenal infusion of 23% sodium propionate (DP), was compared with the DRS diet plus ruminal infusion of 21% glucose (RG). Sorghum was 35% of DM in all diets and infusates were 5L/d. The SFS diet tended (P .19) to increase milk protein content and decrease ruminal pH. The DA infusion increased FCM, and tended to increase fat% and yield. The RG infusion increased milk protein percent and decreased ruminal pH, and the DP infusion tended to decrease DMI. In experiment 3 treatments were: (1) SFS, (2) DA, and (3) RG. Diets and infused amounts were similar to previous trials. No parameters was affected by treatment, but milk protein percent, yield of milk and milk protein were numerically higher SFS than DA, similar to the previous study. Milk composition and production for cows fed DRS plus RG were the same as for cows fed SFS. An in situ trial was conducted to better characterize ruminal starch degradation. The same (DRS and SFS) diets were used as in infusions trials. Treatments were divided into diets and grains as follows: (1) diet DRS, (2) diet SFS, (3) grain DRS, and (4) grain SFS. Material for incubation was ground to pass a 2 mm screen and placed in the rumen for 2, 4, 8, 12, 24 and 48h. DM degradability was not affected by treatment. Starch degradability at 4, 8 and 12h and were higher for the SFS than for DRS diets or grains. In situ data support the infusion data which of higher ruminal starch degradability with SFS than DRS. The studies suggest that increased milk protein content resulting from feeding SFS compared with DRS relates more to increased ruminal starch fermentability (as stimulated by RG) than to greater absorption of acetate or propionate.

Three experiments were conducted to determine the effects of grain processing and NDF levels on performance, ruminal parameters and in situ degradation of nutrients in lactating dairy cows. Higher efficiency was achieved by using SF diets, with major impact on peak of lactation. Higher starch digestibility and lower fiber digestibility were obtained in SF diets, mainly at low fiber level. In a 72 d trial, four cannulated cows were allotted to four treatments containing 49% or 39% alfalfa hay, with 32 or 40% SF or DR sorghum. Milk yield and intake were increased at the lowest NDF/Ruminally degradable starch (RDS) ratio. Ruminal pH and ammonia were decreased in SF diets mainly at low forage level. Ruminal fermentation was stimulated in SF diets with low forage level, resulting in a faster passage rate of the solid phase, however with reduced passage rate of the liquid phase. In a third trial, four cannulated cows were used in a 4 x 4 Latin square design to determine the effects of RDS and NDF levels on in situ degradation of nutrients. Alfalfa hay, sorghum grain (DR or SF) and diets were incubated on experimental diets ranging from 2.3 to 1.3 NDF/RDS ratio. Low ratios stimulated starch degradation and decreased fiber degradation. SF diets improved by 4.9% DM and by 7.5% starch degradation when compared with DR. Maximum degradation rates of diets were obtained at intermediary NDF/RDS ratios due to the associative effects.

Two trials were conducted, the first of which was a 56 d trial with 24 Holstein cows in mid lactation. Treatments were 100% water (T1) or 100% liquid acid whey (T2). Cows on T2 had decreased DM intake and 3.5% FCM, and increased milk fat and protein. Milk fatty acids shifted towards higher medium chained fatty acids for cows on T2 and higher C18 and C18:1 for cows on T1. Molar % of rumen VFA's for cows on T2 decreased for C2, C3, and branched chain fatty acids and increased for C4, C5, and C6. There was no correlation between storage time of whey and whey intake. In the second trial, treatments were arranged in a repeated 3 x 3 latin square design. Six lactating cows were fitted with duodenal cannulae (2 fitted with ruminal cannulae). Treatments were 100% water (T1), 50% water and 50% whey (T2) and 100% whey (T3). The digesta marker was Cr₂O₃. Periods were 12 d with sampling on the last 4 d. Compared to T1, rumen C2 decreased on T2 and T3 and rumen C5 increased on T3 while milk fatty acids shifted towards higher C12 and C14 and lower C18.

Eighty lactating Holstein cows were randomly assigned to one of two treatments: Placebo(C) or 500 mg recombinant methionyl bovine somatotropin (BST). Cows were intramuscularly injected with C or BST every 14 d for 36 wk beginning 60 d postpartum. Factors analyzed for differences in milk yield response to BST included: production level, genetic potential, stage of lactation, and heat stress. Response of low producing cows to BST was numerically greater than that of medium or high producers (averaging 27%, 13%, and 20%, respectively, above controls). However, there was not a significant interaction between BST treatment and production group. Cows of a lower genetic potential exhibited a greater response to BST than cows of a higher potential, but the treatment x genetic potential interaction was not significant. Response of cows to BST in mid to late lactation was slightly greater than in cows in early lactation (13.7% and 15.1% vs. 9.6%, respectively) but no significant interaction was noted. No difference in response was noticed during periods of high ambient temperature.

A total of 450 isolates of Staphylococcus aureus were typed using multilocus sequence typing (MLST). They were isolated from the cattle and environment of a UK organic dairy farm, 43 dairy herds in the USA, the mammary glands of cattle in Chile and the UK, and also included the reference strain Newbould 305 (NCIMB 702892). Strains were compared to investigate differences between isolates from varying sites of isolation and the population detected on a single farm. MLST was suitable for the differentiation of bovine associated S. aureus, and thirty different sequence types were detected. These contained a number of novel alleles detected at each loci, agreeing with previous reports of host-specialisation, and indicating localised strain evolution. MLST was also able to discriminate between isolates detected in milk and on teat skin. The N ewbould 305 strain was significantly (p<0.05) associated with teat skin, and this may have important implications for future studies. The majority of isolates (87.4%) were present within one previously undescribed clonal complex (CC97), which contained representatives from all three geographic locations. Analysis of isolates from a single farrri demonstrated the clonality of the organism, supporting the theory of cow-to-cow spread of disease. No isolates were detected in heifer mammary secretions, suggesting transmission to these animals did not occur. Typing of multiple colonies from a single sample demonstrated strain heterogeneity within individual quarters. Environmental isolates were detected, though it is unlikely that they formed a significant reservoir of infection on the farm studied.

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No description available.

No description available.

Fatty acid binding proteins (FABPs) are a family of proteins involved in the transport of a wide variety of hydrophobic molecules within the cytosol of cells. Tissues with high levels of fatty acid (FA) metabolism such as adipocytes, intestine and liver have a correspondingly high levels of FABPs which correlate to the rate of cellular FA uptake and utilization. Moreover, many of the 11 FABP family members are mainly expressed in a tissue specific manner. For example, FABP6 is predominantly expressed in adult animals in the ileum where it is involved in intracellular transport of bile acids, however it has also been identified in the steroid hormone producing cells of the ovary and adrenal glands in mammals and zebrafish where it may participate in steroid metabolism. Since very few studies have been conducted in aves, the objective of the present study was to determine the tissue and cell specific distribution of FABP6 transcripts and protein through the use of PCR, sequence verification, immunoblotting, and immunohistochemical staining approaches in both female and male chickens and turkey embryos. The purpose of this study is to compose a comparative analysis between FABP6 gene expression in mammals and poultry, and identify the similarities between bile acid and steroid hormone metabolism that may further identify the role of this protein in cellular physiology. Unlike mammals, FABP6 was not restricted to the distal region of the small intestine, but rather distributed across the intestine with a significant abundance in the ileum in the embryo, broilers, and layers. This was confirmed by immunohistochemical images that have a high reactivity of FABP6 in the epithelium of the ileum, with lower quantities found in the duodenum. This study is the first to identify the presence of FABP6 mRNA and protein in the testis, supporting the proposed overlapping function of FABP6 in bile acid and steroid hormone metabolism. Furthermore, FABP6 was examined in various stages of follicular development, being identified in all phases of follicular development, with the greatest abundance in the small yellow follicles. In mammals, FABP6 was identified strictly in the progesterone producing cells of the luteum; while in chickens FABP6 is found in both the granulosa and theca cells that are not limited to progesterone production. / Les protéines de liaison des acides gras (FAPBs) sont une famille de protéines impliquées dans le transport d'une grande variété de molécules hydrophobes dans le cytosol des cellules. Les tissus avec des niveaux élevés d'acides gras (AG) du métabolisme tels que les adipocytes, l'intestin et le foie ont un niveau élevé de FABPs qui sont en corrélation avec le taux important d'absorption cellulaire et d'utilisation de FA. De plus, plusieurs des 11 membres de la famille FABP sont principalement exprimés dans un tissu spécifique. Par exemple, FABP6 est principalement exprimé chez les animaux adultes au niveau de l'iléon, où il est impliqué dans le transport intracellulaire des acides biliaires, mais il a également été identifié dans les cellules de l'ovaire et des glandes surrénales chez les mammifères et chez les poissons zèbres où il peut participer dans le métabolisme des stéroïdes. Étant donné le petit nombre d'études qui ont été menées chez Aves, l'objectif de la présente étude était de déterminer le tissu et la distribution de cellules spécifiques des transcrits de FABP6 et des protéines grâce à l'utilisation de la PCR, de la vérification séquentielle, de l'immunoblot et des approches à la fois dans la coloration immunohistochimique dans des embryons féminins et masculins de poulets et de dindes. Le but de cette étude est de composer une analyse comparative entre l'expression des gènes FABP6 chez les mammifères et chez la volaille, et d'identifier les similitudes entre les acides biliaires et le métabolisme des hormones stéroïdiennes qui peuvent également préciser le rôle de cette protéine dans la physiologie cellulaire. Contrairement aux mammifères, FABP6 n'était pas limitée à la région distale de l'intestin grêle, mais plutôt répartis dans l'intestin avec une abondance significative dans l'iléon dans l'embryon, les poulets de chair, et les couches. Cela a été confirmé par des images immunohistochimiques qui ont une forte réactivité de FABP6 dans l'épithélium de l'iléon, avec des quantités plus faibles dans le duodénum. Cette étude est la première à identifier la présence d'ARNm de FABP6 ainsi que celle de la protéine dans le testicule, en soutenant la fonction proposée dans le chevauchement des acides biliaires FABP6 et du métabolisme des hormones stéroïdes. Par ailleurs, FABP6 a été examiné à divers stades de développement folliculaire et a été identifié dans toutes les phases du développement folliculaire, avec la plus grande abondance dans les petits follicules jaunes. Chez les mammifères, FABP6 a été strictement identifié dans les cellules du corps jaune produisant la progestérone, tandis que chez les poulets, FABP6 se trouve dans les cellules de la granulosa et de la thèque qui ne sont pas limités à la production de progestérone.

The first part of the thesis discusses about the fatty acid composition of bovine milk fat. One morning milk sample was collected from each of 3185 dairy cows between February and June 2010 from 52 commercial herds enrolled in the Quebec Dairy Production Centre of Expertise, Valacta. Individual fatty acid percentages (g/100g of total fatty acids) were determined for each sample by gas chromatography. After necessary editing, final data included 2573 cows representing 46 herds. The objectives of the first study were to study the effects of parity, age at calving and stage of lactation on fatty acid composition of milk of Canadian Holsteins. The model included the fixed effects of parity, age at calving and stage of lactation nested within parity and random effects of herd-year-season of calving and residual. The mixed model was fitted using restricted maximum likelihood (REML) methodology. Parity of cow was significantly (P < 0.05) related to the variation in most fatty acids in milk fat. First parity cows had relatively higher proportions of some beneficial fatty acids and lower proportions of potentially harmful saturated fatty acids as compared to later parity cows. Stage of lactation significantly affected fatty acid composition of cows. The short and medium chain fatty acids were low in the beginning of lactation and increased during the early part of lactation, whereas, an opposite trend was observed for long chain fatty acids. The objective of the second study was to estimate heritabilities of and genetic and phenotypic correlations among fatty acids in milk of Canadian Holsteins using fatty acid data from the first study. Genetic parameters were estimated using multitrait animal models fitted under REML. The estimates of heritability ranged from 0.01 to 0.39 with standard errors ranging from 0.01 to 0.06. Generally, monounsaturated (0.20 to 0.39) and saturated fatty acids (0.02 to 0.34) showed higher heritability estimates than polyunsaturated fatty acids (0.01 to 0.21) and trans fatty acids (0.01 to 0.05). Overall, saturated fatty acids were negatively genetically correlated with monounsaturated and polyunsaturated fatty acids. Most of the genetic correlation estimates between monounsaturated and polyunsaturated fatty acids were positive. In order to change milk fat composition in a desirable direction, selection for one or more monounsaturated fatty acids may be more effective than selection against saturated fatty acids.The objective of the third study (Part 2 of thesis) was to estimate genetic correlations between feed intake and type traits with a view to considering the potential of indirect genetic selection for feed intake using type traits in dairy cattle. Feed intake data on 119388 first lactation Holstein cows were obtained from the Quebec Dairy Production Centre of Expertise, Valacta. The two trait animal models were fitted under restricted maximum likelihood (REML). Estimates of heritabilities ± standard errors for DMI, NELI and CPI were 0.12 ± 0.01, 0.13 ± 0.01 and 0.13 ± 0.01, respectively. Estimates of heritabilities ± standard errors of dairy strength, angularity, body depth, stature and final score were 0.31 ± 0.01, 0.24 ± 0.01, 0.30 ± 0.01, 0.50 ± 0.01 and 0.22 ± 0.01, respectively. All phenotypic and genetic correlation estimates between feed intake and type traits were positive. Angularity showed the highest genetic correlation estimates with feed intake traits (0.60 to 0.65) followed by dairy strength (0.48 to 0.54), stature and body depth (0.29 to 0.36) with all three feed intake traits. Angularity, dairy strength, stature and body depth may be useful for indirect selection of feed intake traits in dairy cattle. / La première partie du mémoire traite sur la composition en acides gras de la matière grasse du lait de bovins. Un échantillon de lait du matin a été recueilli de chacune des 3185 vaches laitières entre Février et Juin 2010 à partir de 52 troupeaux commerciaux inscrits dans le Centre d'Expertise de Production Laitière du Québec, de Valacta. Pourcentages individuels d'acides gras (g/100 g d'acides gras totaux) ont été déterminées pour chaque échantillon par chromatographie de phase gazeuse. Après l'édition de l'information, les données finales ont inclus 2573 vaches représentant 46 troupeaux. Les objectifs du premier étude on été d'étudier les effets de la parité, l'âge au vêlage et le stade de lactation sur la composition en acides gras du lait de vaches Holstein canadiennes. La parité de la vache a été significativement (P <0,05) liée à la variation dans la plupart des acides gras dans la graisse du lait. Vaches primipares ont des proportions relativement élevées de certains acides gras bénéfiques et de plus faibles proportions de potentiellement dangereux comme les acides gras saturés par rapport aux vaches de parité plus tard. Le stade de lactation a significativement affectée la composition en acides gras du lait des vaches. Les acides gras à chaîne courte et moyenne ont été faibles au début de la lactation et ont augmenté au cours de la première partie de la lactation, alors qu'une tendance inverse a été observée pour les acides gras à chaîne longue.L'objectif du second étude a été d'estimer l'héritabilité de et les corrélations génétiques et phénotypiques entre les acides gras dans le lait de vaches Holstein canadiennes en utilisant des données d'acides gras du premier étude. Les paramètres génétiques ont été estimés en utilisant des modèles animaux plusieurs caractéristiques montés sous REML. Les estimations de l'héritabilité variaient de 0,01 à 0,39 avec une erreur standard allant de 0,01 à 0,06. En règle générale, acides gras mono insaturés (0,20 à 0,39) et acides gras saturés (0,02 à 0,34) ont montré des estimations d'héritabilité plus élevés que les acides gras polyinsaturés (0,01 à 0,21) et les acides gras trans (0,01 à 0,05). Dans l'ensemble, les acides gras saturés ont été négativement corrélée génétiquement avec acides gras mono insaturés et polyinsaturés. La plupart des estimations de corrélation génétique entre mono insaturés et polyinsaturés acides gras ont été positifs. Afin de modifier la composition en matières grasses laitières dans une direction souhaitable, la sélection pour un ou plusieurs acides gras mono insaturés peut être plus efficace que la sélection contre les acides gras saturés.L'objectif du troisième étude (Partie 2 de la thèse) était d'estimer les corrélations génétiques entre la consommation alimentaire et les traits de type avec une vue d'examiner le potentiel de la sélection génétique indirecte sur la consommation alimentaire en utilisant les caractères propres des bovins laitiers. Les modèles ont été ajustés au titre du REML. Les estimations d'héritabilité ± erreurs standards pour DMI, NELI et de l'CPI était de 0,12 ± 0,01, 0,13 ± 0,01 et 0,13 ± 0,01, respectivement. Les estimations d'héritabilité ± erreurs standards de la force laitière, angularité, la profondeur du corps, la stature et le score final était de 0,31 ± 0,01, 0,24 ± 0,01, 0,30 ± 0,01, 0,50 ± 0.01and 0,22 ± 0,01, respectivement. Toutes les estimations de corrélation phénotypiques et génétiques entre la prise alimentaire et les traits de type ont été positifs. Angularité montré les estimations les plus élevées de corrélation génétiques avec les traits ingestion (0,60 à 0,65), suivie par la force des produits laitiers (0,48 à 0,54), la stature et la profondeur du corps (0,29 à 0,36) avec les trois traits ingestion d'aliments. Profondeur Angularité, puissance laitière, la stature et le corps peut être utile pour la sélection indirecte des traits ingestion chez les vaches laitières.