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Doctor of Philosophy / Department of Animal Sciences and Industry / Barry J. Bradford / Jeffrey S. Stevenson / Four experiments were conducted to assess nutritional and hormonal strategies to improve fertility in lactating dairy cows. In experiment 1, metabolites (-4, -2, +1, +2, +5, and +7 wk) and steroid hormones in ovarian follicular fluid (FF) and blood serum (BS) were examined in Holstein cows (n = 59) individually fed Saccharomyces cerevisiae fermentation product from -4 through +7 wk (calving = wk 0). Neither metabolites nor hormonal concentrations in BS or FF differed between treatments. In experiment 2 a rumen-protected glucose (RPG) product was supplemented at varying doses in the diet of lactating dairy cows with the objective to increase concentrations of glucose and insulin resulting in decreased activity of liver cytochrome P450 2C and P450 3A, thus increasing blood progesterone concentration. Neither pre-feeding nor post-feeding concentrations of glucose differed among treatments. Pre-feeding insulin did not differ among treatments, but a difference in the concentration of insulin (postprandial minus pre-prandial) was detected (P = 0.01). The increase in insulin was greater in control cows relative to the mean of the 3 RPG doses. We conclude that the insulin response to the RPG diets was diminished relative to the control. Supplementation with RPG did not impact concentrations of progesterone. Experiment 3 tested: (1) a shortened version of Ovsynch (SS: GnRH-1 -7 d - PGF2α - 24 h - PGF2α - 32 h - GnRH-2 - 16 h - AI) that excluded GnRH-1 to resynchronize ovulation in cows bearing a corpus luteum (CL) after a non-pregnancy diagnosis (NPD); (2) the value of including progesterone-releasing intravaginal insert + Ovsynch (OVS + CIDR) in absence of a CL compared with presence of a CL + OVS; and (3) the accuracy of detecting a functional CL by transrectal ultrasonography. Pregnancy per AI (P/AI) risk tended (P = 0.09)) to be greater for OVS than SS but did not differ from OVS + CIDR at 32 d (30.3% [n = 644], 25.7% [n = 678], and 25.9% [n = 270]), respectively. In SS cows, P/AI was greater (P = 0.01) when cows had a functional CL (progesterone was ≥ 1 ng/mL) vs. a nonfunctional CL at d 0, but did not differ from OVS cows. Short synch is a viable alternative to an entire OVS treatment when CL status is accurately detected. Experiment 4 was performed in 2 herds to determine if administering PGF2α concurrent with timed artificial insemination in lactating dairy cows would enhance P/AI. Pregnancy per AI at d 32 and 80 did not differ between treatments. Cows treated with PGF2 alpha in one herd produced more twins than control cows (11.7 vs. 3.2%), whereas no treatment difference was detected in the second herd (5.6 vs. 5.6%), respectively. We conclude that i.m. treatment of lactating dairy cows with 10 mg of PGF2α concurrent with timed AI did not improve P/AI or embryo survival, but increased twinning in one herd. Further research is warranted to determine nutritional and hormonal strategies to improve fertility.

Two experiments were conducted. In experiment 1, the objectives were: 1) to develop and evaluate the accuracy and precision of a new continuous ruminal pH measurement system 2) to determine the required frequency for pH electrode standardization and 3) to determine the effect of additional pre-partum concentrate when compared to NRC (2001) recommendations on post-partum ruminal acidosis in primiparous cows. Accuracy and precision of the Lethbridge Research Centre Ruminal pH measurement system (LRCpH) was determined by comparing LRCpH derived values against manual measurement. To determine the required frequency of electrode standardization, three treatments were imposed (24, 48, or 72 h of continuous measurement) and arranged in a repeated 3×3 Latin square design. The LRCpH accurately and precisely measured ruminal pH (repeated measures correlation coefficient = 0.97 and concordance correlation coefficient = 0.97 for 5-min averages). Changes in baseline mV readings for pH readings after 24, 48 or 72 h of ruminal incubation were not significantly different than zero, indicating that daily standardization of new electrodes was not essential. Using the LRCpH to measure ruminal pH overcomes animal mobility restrictions of previous systems. <p>In experiment 2, the effect of additional concentrate allocation during the pre-partum period was evaluated using 14 ruminally cannulated Holstein heifers. The heifers were assigned to one of two feeding regimes pre-calving: 1) control treatment or 2) an intensive high concentrate feeding treatment (HC). All cows received the same lactation diet post-partum. Ruminal pH was measured continuously from d -5 to d +5, and for 3-consecutive days starting on d +17 ± 1.2, d +37 ± 1.4, and d +58 ± 1.5 relative to parturition. Feeding additional concentrate pre-partum did not reduce post-partum ruminal acidosis. In fact, animals fed the HC treatment had more daily episodes of acute acidosis and lower dry matter intake and body condition score than animals fed the control treatment. Day relative to parturition affected the occurrence and severity of ruminal acidosis with a dramatic increase in ruminal acidosis after parturition. This study demonstrates that feeding addition concentrate pre-partum did not reduce post-partum acidosis which emphasized the need to develop and implement feeding strategies that reduce this risk.

Two experiments were conducted. In experiment 1, the objectives were: 1) to develop and evaluate the accuracy and precision of a new continuous ruminal pH measurement system 2) to determine the required frequency for pH electrode standardization and 3) to determine the effect of additional pre-partum concentrate when compared to NRC (2001) recommendations on post-partum ruminal acidosis in primiparous cows. Accuracy and precision of the Lethbridge Research Centre Ruminal pH measurement system (LRCpH) was determined by comparing LRCpH derived values against manual measurement. To determine the required frequency of electrode standardization, three treatments were imposed (24, 48, or 72 h of continuous measurement) and arranged in a repeated 3×3 Latin square design. The LRCpH accurately and precisely measured ruminal pH (repeated measures correlation coefficient = 0.97 and concordance correlation coefficient = 0.97 for 5-min averages). Changes in baseline mV readings for pH readings after 24, 48 or 72 h of ruminal incubation were not significantly different than zero, indicating that daily standardization of new electrodes was not essential. Using the LRCpH to measure ruminal pH overcomes animal mobility restrictions of previous systems. <p>In experiment 2, the effect of additional concentrate allocation during the pre-partum period was evaluated using 14 ruminally cannulated Holstein heifers. The heifers were assigned to one of two feeding regimes pre-calving: 1) control treatment or 2) an intensive high concentrate feeding treatment (HC). All cows received the same lactation diet post-partum. Ruminal pH was measured continuously from d -5 to d +5, and for 3-consecutive days starting on d +17 ± 1.2, d +37 ± 1.4, and d +58 ± 1.5 relative to parturition. Feeding additional concentrate pre-partum did not reduce post-partum ruminal acidosis. In fact, animals fed the HC treatment had more daily episodes of acute acidosis and lower dry matter intake and body condition score than animals fed the control treatment. Day relative to parturition affected the occurrence and severity of ruminal acidosis with a dramatic increase in ruminal acidosis after parturition. This study demonstrates that feeding addition concentrate pre-partum did not reduce post-partum acidosis which emphasized the need to develop and implement feeding strategies that reduce this risk.

Increased rates of involuntary culling as a consequence of poorer health and fertility had led to the conclusion that dairy cows appear to be less “robust” or adaptable than in the past. A way to address these concerns in breeding programs could be to select for health and welfare by including appropriate traits in a broader breeding index. However, it is important to consider any consequences that such breeding goals may have on dairy cow temperament and welfare. There were two phases to this study. The main objective of phase I was to develop tests for measuring responsiveness to humans and novelty, aggression at the feedface and sociability in dairy cows for use on commercial farms. To allow these tests to be used on commercial farm, they must be short in duration, non-invasive and not disruptive to the daily farming routine, while at the same time allowing comparisons between an individual cow’s responses in a number of similar situations. Results from this study suggested that a standardised human approach test and a stationary visual object are reliable tests for measuring responsiveness of dairy cows to changes in their environment. Measuring behaviour at the feedface proved to be an effective measure of between cow aggression. Inter-animal distance, position in relation to the herd, behavioural synchrony and presence at the feedface proved accurate measures of sociability. The remaining part of the study (Phase II) focussed on assessing how the implantation of a breeding index can affect the temperament of dairy cows on commercial farms. The tests developed were then recorded on 402 first lactation Holstein-Friesian dairy cows selected from sires that scored high (HI) and low (LO) for robustness (health, fertility and longevity traits) to produce two treatment groups on 33 commercial farms. For the purpose of this thesis, only the results from the assessment of aggressiveness are presented. Continuous focal sampling was used to record aggressive behaviour during feeding of the HI and LO cows within the herd. Cows from the HI group were involved in more aggressive interactions, initiated more aggression and received more aggression than cows from the LO group. There was a strong influence of management factors influencing aggression such as the quality of stockmanship, feedface design and nutrition. In conclusion, daughters from sires scoring high for robustness may be expressing a greater ability to maintain position at the feedface during an aggressive interaction. This highlights the importance of assessing the correlated effects of selective breeding, in this case for robustness, on behavioural traits.

Cooling systems used to reduce heat stress in dairy operations require high energy, water usage, or both. Steady increases in electricity costs and reduction of water availability and an increase in water usage regulations require evaluation of passive cooling systems to cool cows and reduce use of water and electricity. A series of experiments were conducted to evaluate the use of heat exchangers buried as components in a conductive system for cooling cows. In the first experiment six cows were housed in environmentally controlled rooms with tiestall beds, which were equipped with a heat exchanger and filled with 25 cm of either sand or dried manure. Beds were connected to supply and return lines and individually controlled. Two beds (one per each kind of bedding material) constituted a control group (water off), and the other 4 (2 sand and 2 dried manure) used water at 7°C passing through the heat exchangers (water on). The experiment was divided in 2 periods of 40 d, and each period involved 3 repetitions of 3 different climates (hot and dry, thermo neutral, and hot and humid). Each cow was randomly assigned to a different treatment after each repetition was over. Sand bedding remained cooler than dried manure bedding in all environments and at all levels of cooling (water on or off). Results from this experiment demonstrated that bed temperatures were lower and heat flux higher during the bed treatment with sand and water on. We also detected a reduction in core body temperatures, respiration rates, rectal temperatures, and skin temperatures of those cows during the sand and water on treatment. Feed intake and milk yield numerically increased during the bed treatment with sand and water on for all climates. No major changes were observed in the lying time of cows or the composition of the milk produced. The efficiency of conductive cooling as a heat abatement technique in dairy production is highly correlated with the distance between the cooling system and the skin of the cow and the type of bedding material used. A second experiment was conducted to identify possible improvements in the utilization of conductive cooling for cooling cows. Heat exchangers buried 12.7 cm below the surface as components in a conductive system ware evaluated in this study. Six cows were housed in environmentally controlled rooms with tie-stall beds, which were equipped with a heat exchanger and filled with 12.7 cm of either sand or dried manure. Beds were connected to supply and return lines and individually controlled. Two beds (one per bedding material type) constituted a control group (water OFF), and the other four (two sand and two dried manure) used water at 7°C passing through the heat exchangers (water ON). The experiment was divided into two periods of 40 days and each period involved three repetitions of three different climates hot dry (HD), thermo neutral(TN) and hot humid (HH). Each cow was randomly assigned to a different treatment after each repetition was over. The sand and water on treatment was the most efficient treatment under heat stress conditions (humid or dry heat). Cows in stalls with the sand and water on treatment demonstrated lower rectal temperatures, respiration rates, skin surface temperatures and core body temperatures compared to the other three treatments. Additionally, the sand and water on treatment increased milk yield and resting time of cows under heat stress. Also, the sand and water on treatment had the lowest bed surface temperatures and highest heat exchange compared to the other treatments. From these two experiments we confirm that heat exchangers are a viable heat abatement technique that could reduce the heat load of heat stressed cows; however, this system should be paired with additional cooling systems (e.g. fans and or misters) to most efficiently reduce the negative effects of heat stress on dairy production. Additionally, Sand was superior to dried manure as a bedding material in combination with heat exchangers. To make further recommendations of the use of heat exchangers in commercial dairy farm, a third study was developed. Based on the data obtained in the previous experiments, a comprehensive energy balance was developed to fully understand conductive cooling in two different environments (HD and HH), two bedding materials (sand and dried manure) and two depths between cows and the heat exchangers (25 vs. 12.5 cm). The energy balance estimates indicated that sand is the most efficient bedding material when utilized as bedding material with conductive cooling in both hot dry and hot humid environments. In the hot-dry environment there was an increase in the conductive heat exchanged with the reduction in bedding depth to 12.5 cm, however this did not result in a reduction in the heat storage of cows. In the hot-humid environment when heat exchangers were placed 12.5 cm from the top of the bed there was an increase in both the conductive heat loss and heat storage of cows when compared to 25 cm. Additionally, results demonstrated that the efficiency of heat exchangers as measured by heat flux was improved when heat exchangers were at a depth of 12.5 cm. The sensibility analysis indicated that a reduction in the depth and/or an increase in the thermal conductivity of both bedding materials would maximize conductive heat exchange. These results should be utilized as recommendations for the utilization of heat exchangers and conductive cooling in commercial dairy farms. Evaporative cooling is widely used in dairy farms located in arid environments. Even though, these cooling systems have been shown to effectively reduce the heat stress of lactating dairy cows, a growing shortage of water and rising cost of electricity compromise its future usage. An experiment was developed to compare two evaporative cooling systems, their interaction with lactating dairy cows and their usage of natural resources. The efficacy of 2 evaporative cooling systems (Korral Kool, KK, Korral Kool Inc., Mesa, AZ; FlipFan dairy system, FF, Schaefer Ventilation Equipment LLC, Sauk Rapids, MN) was estimated utilizing 400 multiparous Holstein dairy cows randomly assigned to 1 of 4 cooled California-style shade pens (2 shade pens per cooling system). Each shaded pen contained 100 cows (days in milk = 58 ± 39, milk production = 56 ± 18 kg/d, and lactation = 3 ± 1). Production data (milk yield and reproductive performance) were collected during 3 months (June–August, 2013) and physiological responses (core body temperature, respiration rates, surface temperatures, and resting time) were measured in June and July to estimate responses of cows to the 2 different cooling systems. Water and electricity consumption were recorded for each system. Cows in the KK system displayed slightly lower respiration rates in the month of June and lower surface temperatures in June and July. However, no differences were observed in the core body temperature of cows, resting time, feed intake, milk yield, services/cow, and conception rate between systems. The FF system used less water and electricity during this study. In conclusion, both cooling systems (KK and FF) were effective in mitigating the negative effects of heat stress on cows housed in arid environments, whereas the FF system consumed less water and electricity and did not require use of curtains on the shade structure. Results of this research indicate that effective use of conductive cooling in combination with efficient evaporative cooling systems offer opportunities to reduce both water and electricity consumption on dairy farms under both hot dry and hot humid environments.

Master of Science / Department of Animal Sciences and Industry / Barry J. Bradford / Dairy cows undergo many homeorhetic adaptations during the transition to lactation. Although many of the physiological processes - including increased lipolysis and postpartum inflammation - are adaptive, exaggerated responses can contribute to metabolic disease and reduced milk production. L-carnitine has been shown to increase hepatic oxidation of fatty acids and reduce hepatic lipid accumulation in early lactation cows; however, L-carnitine is degraded in the rumen. An experiment using 4 ruminally-cannulated Holstein heifers in a split plot design demonstrated that the relative bioavailability of L-carnitine was greater when delivered abomasally than ruminally. There was a dose × route interaction and a route effect for increases in plasma carnitine above baseline, with increases above baseline being greater across all dose levels (1, 3, and 6 g L-carnitine/d) when infused abomasally compared to ruminally. A second experiment used 56 lactating Holstein cows in a randomized complete block design to evaluate 2 rumen-protected products (40COAT and 60COAT) compared to crystalline L-carnitine at doses targeting 3 and 6 g/d carnitine. Although crystalline and 40COAT were effective in linearly increasing carnitine concentrations, only subtle responses were seen for the 60COAT, which were less than that for crystalline carnitine in plasma, milk, and urine. Ineffectiveness of rumen-protected products to increase carnitine concentrations beyond crystalline may have been due to over-encapsulation that hindered liberation of the carnitine and its absorption in the small intestine. Although L-carnitine has the potential to reduce postpartum hepatic lipidosis, effective rumen protection of L-carnitine while maintaining intestinal availability needs further investigation. Plant polyphenols have anti-inflammatory properties and when administered during the transition period, have been shown to increase milk production. An experiment used 122 multiparous Holstein cows in a randomized block design to determine the effect of short term (5-d; SBE5) and long term (60-d; SBE60) administration of Scutellaria baicalensis extract (SBE)on whole-lactation milk yield, 120-d milk component yield, and early lactation milk markers of inflammation. Whole-lactation milk yield was increased for SBE60 compared to control, but was not different for SBE5 compared to control. Greater total pellet intake, milk lactose yield, and reduced SCC during wk 1-9 for SBE60 compared to control, all could have contributed to the observed sustained increase in milk yield. Milk production parameters were not different for SBE5 compared to control. No treatment effects were observed for BCS or milk markers of inflammation (haptoglobin) and metabolic function (β-hydroxybutyrate). Overall, long term administration of S. baicalensis effectively increased milk production, however the mechanism by which this was achieved is unknown. Although routes of administration to effectively achieve their physiological responses were different between L-carnitine (abomasal delivery) and SBE (feeding), both bioactive nutrients can improve the metabolic function of early lactation dairy cows.

The objective of this thesis was to determine the effect of housing and feeding management and cow characteristics on the behavioral patterns of cows in automated milking systems (AMS). In a first study, increasing frequency of feed delivery from 1 to 2x/d for cows milked in an AMS resulted in longer lying duration. In that study, lame cows milked less frequently, had increased lying durations and more frequent lying bouts. In a second, cross-sectional study of 13 AMS farms it was found that cows had longer lying durations when given more space at the feed bunk and when their feed was pushed up more frequently. Milking frequency increased as cows/AMS decreased. Milk yield increased with space at the feed bunk. Overall, these results suggest that feeding management, robot and bunk-space availability, and health status affect the behavior and production of AMS-milked cows. / Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) and the Canadian Bovine Mastitis Research Network (CBMRN)

The effects of feeding Master Graze (MG) on dairy cows productivity and nutrient digestibility were evaluated in experiment 1. Sixteen cows were divided into 4 groups and fed treatment diets for 4 consecutive periods. Cows on the control diet were fed a diet with corn silage and alfalfa hay as forage source (1:1; DM basis). For treatment groups, the MG substituted the forage mix at 16, 33 and 50%. The feeding of MG at the three tested levels had no effects on feed intake, milk production or milk composition. The apparent digestibility of DM, OM, NDF and CP were higher in cows fed the MG. In experiment 2, the effects of maturity and preservation method on MG nutrient composition and digestibility were evaluated. The MG was harvested at 3 maturity levels and then preserved using oven-dried, ensiled, or freeze dried. In general, the MG digestibility and nutritional quality was higher in the first cut and with the freeze dried preservation method.

Doctor of Philosophy / Department of Animal Sciences and Industry / Luis G. Mendonca / Reproduction is an important part of a dairy operation that directly affects milk production and profitability. Fertility of high-producing dairy cows is less than desired. Reproductive efficiency is further impaired during summer months and after cows develop postpartum uterine disease. Heat stress and uterine disease act as stressors that negatively influence fertility of dairy cattle through a variety of mechanisms. This dissertation further investigates the negative effects of heat stress and uterine disease on reproduction, as well as examines two potential markers for predicting risk of developing uterine disease. Study 1 investigated the treatment of lactating dairy cows with gonadotropin-releasing hormone (GnRH) before first insemination during heat stress. Two experiments were performed to compare ovarian responses, pregnancy per artificial insemination (AI), and patterns of insemination of two estrus detection-based presynchronization protocols before first AI during summer heat stress. Treatment of cows with GnRH during summer heat stress altered ovarian response and pattern of insemination, however, did not improve pregnancy per AI. Study 2 evaluated ovarian response to treatment with GnRH and the odds of bearing a corpus luteum or being inseminated in cows with or without purulent vaginal discharge (PVD). Furthermore, hazard of insemination after administration of prostaglandin F2α was evaluated in dairy cows with or without PVD. Ovarian response was altered in cows with PVD compared with cows without PVD. Odds of bearing a corpus luteum or being inseminated was not associated with PVD in primiparous cows, whereas it was associated with PVD in multiparous cows. Hazard of insemination after prostaglandin F2α was not associated with PVD. Study 3 investigated arginase and matrix metalloproteinase-8 (MMP-8) as potential markers for metritis. Activity of arginase 7 days before parturition has been identified as a potential marker for the risk of developing metritis in dairy cows. In contrast, MMP-8 was not associated with the risk of developing metritis, therefore, MMP-8 is not a good candidate as a marker for metritis. Further research is warranted in the areas of reproductive physiology, heat stress, and uterine disease because several unanswered questions still exist. Improving fertility during times of heat stress and after the occurrence of postpartum uterine disease will improve milk production, animal welfare, and profitability of dairy farms across the world.