Past Events

Milk replacers (MR) formulated to contain more lactose than whole milk could potentially reduce insulin sensitivity and gut barrier function in dairy calves. Three studies were conducted to characterize the impact of fat, protein and lactose content, and the fatty acid composition, of MR on glucose-insulin kinetics, gastrointestinal tract (GIT) growth and func-tion. In the first study, thirty-four calves were fed either a high lactose (HL; 46.1%DM lactose) or a high fat (HF; 24.6%DM crude fat) MR during the first week of life.

Reproductive inefficiency is one of the main reasons for culling in both the dairy and beef industry, with pregnancy losses being a contributing factor. Most pregnancy losses occur early after fertilization which may be due to reduced cow and/or bull fertility.  Cattle fertility is a complex trait affected by many physiological events that genomic selection fails to account for, including a non-receptive uterine environment or inadequate semen quality. By identifying highly fertile animals, production efficiency in the cattle industry can be maintained.

Cup plant (Silphium perfoliatum Sp.) is characterized by high biomass yields and the ability to grow on mar-ginal lands where common dairy forage sources are unable to thrive. The objective of this research was to as-sess its feeding value for dairy cows by comparative evaluations of DM degradability in vitro and in situ, and lactational performance in vivo when fed in partial replacement (13% of ration DM) of corn and alfalfa silag-es. In vitro results showed that cup plant silage only had lower DMD than the alfalfa silages, and lower pH than corn silage.

Johne’s disease is a chronic wasting disease in dairy cattle caused by the bacterium Mycobacterium avium subspecies paratuberculosis (MAP). Genetic selection can help to control this disease, and one candidate gene of interest is the gene encoding for interleukin-10 receptor subunit alpha (IL10Rα). A bovine mammary epithelial cell line was created with the gene encoding IL10Rα knocked out (IL10KO). This cell line was ex-posed to live MAP, and mRNA was extracted. The differentially expressed genes were compared between the IL10KO and wild-type cell lines, and gene ontology was performed.

Mastitis is a very challenging disease in the dairy industry that affects the animal’s health, as well as the producer’s profit and management. Although it has been studied in depth over the years, we have still yet to eliminate it due to the fact that there are numerous pathogens that can cause a mastitis infection, and they are extremely prevalent in the cow’s environment. For this reason, emphasis is being placed on identifying cows that are more able to prevent or recover from a mastitis infection based on her genetics.

Research into the genetic aspects of calf health traits is an emerging field for the dairy industry. Calf respiratory illness and diarrhea remain the two highest causes of calf morbidity and mortality in Canada and worldwide. Previous research has shown there are long term effects to an animal as a result of calfhood morbidity. The goal of the research described in this thesis was to understand the quantity and quality of calf health information available, specifically respiratory illness and diarrhea, that could be used in future genetic research.

Due to the high prevalence of gastrointestinal diseases and disorders in dairy calves, optimizing nutritional strategies to enhance gastrointestinal (GIT) development and improve calf health is at the forefront of industry concerns. This thesis investigates the effects of whole milk powder (WP) and milk replacer (MR) of similar macronutrient composition on GIT development, function, and composition in male Holstein calves.

Free-stalls are an important area of dairy production where cow comfort should be maximized. Comfortable free-stalls con-tribute to the cows’ ability to achieve adequate rest, which translates into improved health and production. However, free-stalls are generally designed to promote cleanliness and reduce the labour required for maintenance through restricting cow behaviour. The overall objective of this thesis was to evaluate a novel free-stall designed to improve cow comfort using an increased stall slope, minimal stall partitioning, a heat abatement system, and supplemental lighting.

Bones are a highly complex tissue capable of adapting to changes in muscle usage through specialized cells which respond to mus-cle strain. As such, the way in which birds utilize their wings has a direct impact on strain production of the flight muscles, and sub-sequently the keel bone to which the muscles anchor. Currently, adaptations of muscle and bone in response to a decrease in wing use is unknown in laying hens. Therefore, the first study (Chapter 2) sought to investigate if a loss of flight feathers (reduction to wing area) would reduce wing activity.