A trial was conducted to evaluate the accuracy of the 1996 NCR beef model to predict DMI and ADG of pregnant cows under western Canadian conditions. Over two consecutive years, 90 Angus (587±147 kg) cows assigned to 15 pens (N=6) were fed typical diets ad libitum, formulated to stage of pregnancy. Data collection included pen DMI and ADG (corrected for pregnancy), calving date, calf weight, body condition scores and ultrasound fat measurements, weekly feed samples and daily ambient temperature. DMI and ADG for each pen of cows in each trimester was predicted using the computer program Cowbytes based on the 1996 NRC beef model. The results indicate that in the 2nd and 3rd trimester of both years the model under predicted (P≤0.05) ADG based on observed DMI. Ad libitum intake was over predicted (P≤0.05) during the 2nd trimester, and under predicted (P≤0.05) during the 3rd trimester of pregnancy. A second evaluation was carried out assuming thermal neutral (TN) conditions. In this case, it was found that during the 2nd and 3rd trimesters there was an over prediction (P≤0.05) of ADG relative to observed. Under these same TN conditions, the ad libitum intake of these cows was under predicted (P≤0.05) for both the 2nd and 3rd trimesters. These results suggest current energy equations for modelling environmental stress, over predict maintenance requirements for wintering beef cows in western Canada. The results also suggest that the cows experienced some degree of cold stress, but not as severe as modelled by the NRC (1996) equations. Further research is required to more accurately model cold stress felt by mature cattle, and their ability to acclimatise to western Canadian winter conditions.

This thesis summarizes an investigation of antimicrobial resistance (AMR) and antimicrobial use (AMU) in cow-calf herds. The specific objectives of this project were to describe common reasons for treatment and the types of antimicrobials used in cow-calf herds, to describe the frequency of AMR in generic fecal Escherichia coli isolated from various age groups commonly found on cow-calf farms, to determine risk factors associated with the occurrence of AMR, and finally to investigate the underlying molecular mechanisms of AMR in cow-calf herds. At least 86% of the herds treated one or more calves or cows during the study period; however, the overall proportion of both calves and cows reported as treated was less than 14% for calves and 3% for cows. The majority of antimicrobials reported as used in cow-calf operations were for individual therapeutic use rather than prophylaxis, metaphylaxis, or growth promotion. Injectable formulations were the most commonly reported method of antimicrobial administration on cow-calf farms. Cow-calf herds in Wetern Canada are not a significant reservoir for resistance to antimicrobials classified as very important to human medicine such as ciprofloxacin and ceftiofur. The three most common resistances detected were to tetracycline, sulphamethoxazole, and streptomycin regardless of age group. Young calves sampled in the spring of the year were more likely to be shedding AMR E. coli than older calves sampled in the fall of the year or than cows sampled in the spring of the year. The cow-calf pair relationship was not an important factor in transfer of AMR from the individual cow to her calf, but the presence of AMR in the general cow herd was associated with AMR in the calf population. The potential importance of co-selection for AMR at the molecular level was demonstrated by both the risk factor analysis and the molecular work. Phenotypic resistance to streptomycin, tetracycline, and sulphamethoxazole were each associated with the presence of resistance genes from all six families of antimicrobials examined in this study. Several statistically significant associations were also detected between the resistance genes considered. No significant associations were detected between any of the AMR phenotypes or genotypes and the STEC virulence factors stx1, stx2 and eae.

Birth weight (BW) (n =1277) and weaning weight (WW) (n = 1090) of calves, pregnancy rate (PR) (n = 1386), calf crop born (CCB) (n = 1386), calf crop weaned (CCW) (n = 1294), cow’s weight at palpation (CW) (n = 1474) and cow body condition score (BCS) (n = 1473) were evaluated from 1994 to 2006 in 143 F1 cows sired by Brahman (B), Boran (Bo) and Tuli (T) bulls and born to Angus and Hereford cows. Mouth scores (MS) (n = 139) were assigned to the remaining cows in 2004 and 2005. Fixed effects included sire breed of cow, dam breed of cow, and calf’s birth year/age of cow; random effects included cow and sire of cow. BW and WW were evaluated using the same model and adding gender for both and age for WW. All two-way interactions were tested for significance. Calf’s birth year/age of dam was significant for all traits (P < 0.05) except WW. BW for calves out of F1 B, Bo and T bulls were 35.08, 34.76 and 34.87 kg, respectively, and were not different. WW differed (P < 0.05) for calves out of F1 B, Bo and T cows (235.87, 221.10 and 208.35 kg, respectively). PR (0.922, 0.955 and 0.936, respectively), CCB (0.881, 0.931, 0.890, respectively), CCW (0.848, 0.898 and 0.869, respectively), did not differ among F1 B, Bo and T cows. CW when cows were 8- or 9-year old were 600.78, 514.63 and 513.14 kg, respectively, for F1 B, Bo and T cows, with those sired by B being heaviest (P < 0.05). BCS for B-, Bo- and T-sired cows were 5.23, 5.48 and 5.18, respectively, with F1 Bo cows having highest scores. Higher MS (P < 0.05) were assigned to Bo and B-sired cows (0.95 and 0.94, respectively) compared to T-sired cows (0.78), when both broken and solid incisors were scored 1, and smooth scored 0. When both smooth and broken were scored 0, and solid were scored 1, higher scores were assigned to B- (0.53) compared to T-sired cows (0.24), the Bo-sired cows being intermediate. Higher reproductive rates were found for Boran-sired cows, but Brahman-sired cows weaned heavier calves.

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)

Cow-calf producers in western Canada are faced with many decisions throughout the production cycle. The choice of calving time impacts production rate, marketability of calves, income and expenses and net revenue. The purpose of this study was to determine whether June calving could increase net revenues and be a preferred choice across different risk aversion levels over March calving in western Canada. Data for this study were taken from a study carried out by Iwaasa et al. (2009), who collected information from three sites; Brandon, MB, Lanigan, SK and Swift Current SK. Stochastic budgets and a simulation model were used to study the economic impact of calving time. In Brandon and Lanigan, It was found that June calving increased net income and was the dominant alternative across all levels of risk aversion, and in Swift Current, June dominated at high-risk aversion levels.

Cow-calf producers in western Canada are faced with many decisions throughout the production cycle. The choice of calving time impacts production rate, marketability of calves, income and expenses and net revenue. The purpose of this study was to determine whether June calving could increase net revenues and be a preferred choice across different risk aversion levels over March calving in western Canada. Data for this study were taken from a study carried out by Iwaasa et al. (2009), who collected information from three sites; Brandon, MB, Lanigan, SK and Swift Current SK. Stochastic budgets and a simulation model were used to study the economic impact of calving time. In Brandon and Lanigan, It was found that June calving increased net income and was the dominant alternative across all levels of risk aversion, and in Swift Current, June dominated at high-risk aversion levels.

Theses (M.S.)--Marshall University, 2007. / Title from document title page. Includes abstract. Document formatted into pages: contains ix, 76 pages including illustrations and maps. Includes vitae. Bibliography: p. 65-71.

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.

Master of Agribusiness / Department of Agricultural Economics / Elizabeth Yeager / Crossbreeding has long been promoted as the preferred method of production for cow-calf producers. Unfortunately, crossbreeding can add complexity to maintain a consistent cowherd and can drive the need to purchase replacement females from outside the producer’s own herd. This has led some producers to pursue straightbreeding to provide their own supply of replacements and the opportunity to more narrowly select for individuals suited to a carcass quality grid marketing system. The subject of this thesis is a Red Angus based cowherd that breeds females to Red Angus sires in early parities. The same cowherd is bred to Simmental sires in later parities to produce a terminal F1 cross. It is the objective of this thesis to explore whether this operation’s straghtbred or crossbred calf crop provides an economic advantage to the other treatment. Mortality data were collected during pre-weaning for both steers and heifers. Mortality data were collected for steers during backgrounding and feedlot phases. Wean weights and feed conversion performance during the backgrounding phase was unavailable for use in this study. Feedlot and carcass data were captured for steers from both treatments. The straightbred treatment showed an advantage in carcass quality. The composite treatment showed a slight advantage in mortality cost during pre-weaning and feedlot phase, and a slight advantage in feed conversion and cost per pound of gain while in the feedlot. The composite treatment showed a significant disadvantage during the backgrounding phase. The primary advantage for the composite treatment was the difference in actual wean weights. This difference in wean weight carried over to a higher start weight during the feedlot phase. This was the driving factor in providing the composite group the economic advantage in this study and making it the more attractive production option.

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.