NASEM (2021) recently made strides in characterizing effects of 5 individual EAA on milk protein production. However, there are 15 other AA that are incorporated into milk protein, and as such, these AA likely also play significant roles in driving milk protein synthesis, but lack of data prevents their incorporation into current models. A greater supply of AA to the mammary glands does not always mirror AA absorption—the process by which absorbed AA convert into milk protein is variable, and this may be linked to the way the udder regulates AA uptake to preserve intracellular balance. AA transporters housed within the cellular membranes of mammary epithelial cells (MEC), the mammary glands' constituents, are responsible for mediating this intracellular balance. Thus, the objectives of this dissertation were to investigate how AA transport is affected by various AA concentrations using both in vitro and in vivo approaches. In study 1, we evaluated effects of valine and a group of NEAA (AQG; Ala, Gln, and Gly) on exchange transport rates of AA in bovine MEC. High AQG concentrations stimulated Leu, Phe, and Val influx rate parameters, demonstrating that AQG likely increased transport activity for these substrates through exchange transporters. Additionally, high Val concentrations decreased Ile and Leu net uptakes, which occurred via efflux stimulation and transamination downregulation. In study 2, we aimed to identify the effects of 10 EAA and 2 Tyr (CDENSPY) on transport rates and transporter regulation (mRNA expression and protein abundance). Within the physiological AA concentrations used, we were able to measure differential effects of AA on each AA transporter. For example, His stimulated SLC38A2 and SLC38A2 mRNA expression at a decreasing rate; the apex for this curve was reached at a concentration very close to mean plasma concentrations in lactating dairy cows. Therefore, we determined that these transporters may be transcriptionally regulated to regulate intracellular His concentrations. Additionally, all EAA and NEAA groups were involved in significant 2-way interactions on transporter expression and activity. Furthermore, we measured transport rates and rate constants (free of mass influence) of 12 AA to determine important AA on influx, efflux, transamination, irreversible loss, and protein synthesis. We demonstrated competitive inhibition among several AA that share transport systems such as between BCAA. Furthermore, we again demonstrated that NEAA can stimulate transport activity for AA involved in exchange transport. In study 3, we investigated the effects of jugular Lys, Ile, Val, or AQG infusion on mammary AA metabolism and production in lactating dairy cows. Interestingly, Val decreased DMI and milk protein production along with net uptakes of several AA, while the remaining treatments had little metabolic effects. In study 4, we demonstrated that both high protein and starch concentrations independently stimulated milk protein production, but glucose precursor partitioning (lactate, propionate and other) was only affected by starch. In conclusion, we anticipate that nutrition models estimating milk protein production will eventually incorporate up to 20 AA and multiple 2-way interactions; additionally, extremely high concentrations of AA should be prevented to combat negative impacts caused by AA imbalances. However, much more work is required to take steps in this direction. / Doctor of Philosophy / Overfed protein can pose a significant health and environmental risk. Unabsorbed amino acids (AA), the building blocks of protein, are released by dairy cattle into the environment as various nitrogen products. One specific risk is excess runoff of nitrates from dairy farms into nearby water bodies. This contamination can result in serious water quality issues, including eutrophication, which depletes O2 levels in aquatic ecosystems with algae overgrowth, causing dead zones where aquatic life cannot survive. Furthermore, high nitrate levels in drinking water can decreased oxygen availability in humans, in which pregnant women and babies are the most at risk. Finally, the volatilization of N compounds also contributes to air pollution and the formation of greenhouse gases like nitrous oxide, a potent climate-altering compound with global warming potential. Theoretically, feeding an AA profile to precisely match dairy cow requirements would minimize these losses. However, the udder does not take up all available AA. Thus, this research aimed to better understand different AA profiles on AA transport, the route in which AA are taken up by the milk-producing cells in the cow's udder, to ultimately increase efficiency of milk production. In our first study, we demonstrated that non-essential AA (Ala, Gln, and Gly), which can be synthesized in the mammary glands, stimulated Leu, Phe, and Val transport activity within mammary epithelial cells, which could mean that supplemental non-essential AA could increase essential AA transport efficiency. Interestingly, high Val had a negative effect on net uptake (entry minus exit) of Leu and Ile. The second study sought to understand how varying concentrations, within ranges observed in the blood of lactating dairy cows, of 10 different essential AA and 2 non-essential AA groups affected AA transporter expression and activity. We observed greater protein presence and mRNA expression levels of several transporters in response to low availability of their AA transport substrates. Additionally, some AA were involved in stimulating transporter expression and activity when present at high concentrations, such as Leu. There was a plethora of 2-way interactions among AA on transporter protein quantity, mRNA expression, and activity that indicated that the relationship between certain AA will need to be incorporated into future nutrition models. In our third study, we observed that high Val supply decreased the amount that cows ate as well as their milk protein production. This demonstrated that excessive concentrations of certain AA may negatively affect cow metabolism. Lastly, we wanted to investigate the relationship between protein and glucose production in dairy cows, as energy availability is another driver of milk protein production. Our fourth study revealed that dietary protein and starch independently increased milk protein production, yet only starch affected glucose formation. Our findings urge caution against excessive AA concentrations in diets, as imbalances can have negative effects. Overall, we have demonstrated that AA transporters are differentially affected by changes in individual AA supply and various 2-way interactions. This work unveiled the almost unlimited AA interactions that must be further explored to better integrate this knowledge into practical dietary formulations for dairy cows.

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Doctor of Philosophy / Food Science Institute / Melvin C. Hunt / Three experiments were conducted to evaluate factors affecting ground beef color stability with the objectives: 1) To characterize color characteristics of different ground muscles from similarly fed and managed cows and steers; 2) To evaluate the contributions different muscles make to overall ground beef color stability; and 3) To determine if cow biological type (beef-type vs. dairy-type) affects ground beef color dynamics. In general, ground muscles from fed cows appeared darker and redder than ground muscles from steers. Chronological age did not affect ground beef color stability of muscles from fed cows. Use of steroid implants or [Beta]-agonists did not affect ground muscle color stability of fed steers or fed cows. Overall color stability varied more in muscle from steers than from fed cows. Fed cow muscles tended to have a greater proportion of saturated and mono-unsaturated fatty acids to poly-unsaturated fatty acids than fed steer muscles. Ground muscles from fed cows had better color stability properties than ground muscles from steer. When muscles of various color stability were blended to make ground beef and packaged in high-oxygen modified atmosphere (HiO[subscript]2 MAP), high color stability muscles (≥ 75%) in formulations maximizes display color life; however, inclusion of low color stability muscles (≥ 25%) in ground beef formulations had deleterious effects on ground beef color life. Ground semimembranosus (SM) from dairy cows exhibited darker initial color than ground SM from beef cows when packaged in HiO[subscript]2 MAP. However, ground SM from dairy cows was more color stable than ground SM from beef cows when packaged in HiO[subscript]2 MAP. Cow trim used as a fat source in ground beef formulations improved color stability compared to young beef trim when packaged in HiO[subscript]2 MAP. Isolating and managing muscle sources enable meat processors to better manage ground beef based upon intrinsic factors affecting ground beef color stability.

Master of Science / Department of Agricultural Economics / Ted C. Schroeder / Considerable risk is present in today’s ranching world; especially price and production risk. A producer who can tolerate more risk, and is knowledgeable about how to effectively manage price and production risk, may have opportunity to increase profitability relative to a highly risk averse producer. The purpose of this study is to investigate perceptions and sources of risk, identify how risk management is conducted, assess price and production risks, and view differences between producers’ perceptions versus their attitudes towards risk and factors that affect risk. In order to investigate cow-calf producers’ perceptions of risk, an instrument was created to survey beef cow-calf producers in the Kansas Farm Management Association (KFMA). Respondents provided information on their production practices, marketing methods, operating decisions and risk related to their cow-calf operations. A risk preference score for individual producers was developed from specific survey questions to determine three objectives: to classify producers’ risk preferences related to their operating decisions; determine operating decisions that affect risk preferences; and identify what production and marketing practices in which producers were willing to risk for a chance to increase the net returns to their operations. A bi-directional causality between risk aversion and operation characteristics was illustrated between how operating decisions are related to risk aversion, and risk aversion is related to operating decisions. Factors that were found to influence risk aversion were socioeconomic factors such as age, off-farm income, debt-to-asset ratio, farm size, and number of cows owned, as well as comparative advantages of producer’s: use and analysis of new technology, business planning skills and marketing skills. Models showing how risk aversion was related to production management focused on producer’s financial soundness, production practices and marketing methods, specific to retained ownership. Producers who would participate in value-added programs to increase returns to their operation have a comparative advantage in marketing skills, own more cattle, and are less diversified in terms of their farm enterprise incomes.

A study to examine factors that influence dairy cattle fertility was conducted in the United Kingdom (UK) and Malawi. Productivity data from the UK comprising 56,014 records from 574 Holstein cows were retrieved from a database at Scotland’s Rural College Dairy Research Centre in Dumfries. The cows were of either high (select) or average (control) genetic merit and fed total mixed rations with high or low forage. These formed four production systems - high forage select (HFS), low forage select (LFS), high forage control (HFC) and low forage control (LFC). Data from Malawi were obtained through a baseline survey in 67 smallholder farms and monitoring of 28 and 62 dairy cows from smallholder farms and a commercial farm, respectively. The breeds were Holstein-Friesians and Holstein-Friesian x Malawi Zebu crosses predominantly fed forages supplemented with concentrates. Some cows were fitted with accelerometers to enable monitoring of cow activity which was then related to cow fertility and energy balance. The data were analysed using descriptive statistics, mixed models and logistic regression models using SAS 9.3. The UK data showed that production system significantly (p<0.05) influenced milk yield, body energy content (BEC) and fertility. BEC is a trait that indicates absolute level of energy in the body per day regardless of energy use and intake the previous day. Daily milk yield of LFS cows was 35±0.1 (mean±SEM) litres which was significantly (p<0.05) higher than that of LFC (30.4±0.1 litres), HFS (27.5±0.1 litres) and HFC (24.3±0.1 litres) cows. LFS cows also had the highest milk yield acceleration to peak milk yield (0.51 litres/day/day) than (LFC 0.47±0.02 litres/day/day), HFC (0.47±0.03 litres/day/day) and HFS (0.46±0.03 litres/day/day) cows. The interval from calving to nadir BEC was 68±5, 83±6, 88±5 and 106±6 days for LFC, LFS, HFC and HFS cows, respectively. Days to first high luteal activity (DFHLA) and days to successful service (DSS) were significantly different with production system and genetic merit, respectively. LFC cows had DFHLA of 27±2 days (mean±SEM) which were significantly lower (p<0.05) than those of HFC (30±3 days), HFS (30±2 days) and LFS (35±3 days) cows. Average genetic merit cows had significantly lower (p<0.05) DSS (119±5 days, mean±SEM) than high genetic merit cows (132±5 days). Results from data collected in Malawi showed variations that reflected differences in management and other environmental factors. Average daily milk yield per lactation in Malawi was 13.3±4.9 (mean±SD) litres. Fertility traits in the UK herd were better than those in Malawi herds. The average DFHLA in Malawi was 79±29 days while in the UK it was 31±18 days. Cow activity in both the UK and Malawi farms varied with the feeding system, genetic merit and BEC. Select cows on home grown feeding system were more active (motion index =6250±40), stood longer (13.4±0.04 hours/day) and spent more time eating (5.6±0.32 hours/day, mean±SEM) than select cows on by products feeding system that had motion index, standing and eating time of 5166±37, 11.9±0.04 hours/day and 4.6±0.16 hours/day, respectively. Genetic merit, lactation number, days to first observed oestrus, calving BEC, service BEC and service milk yield were significant predictors of pregnancy to first insemination (p<0.05) while genetic merit, milk yield, percentage BEC between calving and service, service milk yield and service BEC were significant predictors (p<0.05) of pregnancy to the first three inseminations. Validation of models derived showed C-statistics of the receiver operating characteristic (ROC) curve of 0.66 (95% confidence interval (CI): 0.57 to 0.75) and 0.65 (CI: 0.55-0.75), respectively. It is concluded that genetic merit, feeding system, parity, energy status and stage of lactation are the major factors that determine the likelihood of achieving pregnancy following insemination. Models developed have a potential to predict the probability of pregnancy to an insemination at an acceptable level of accuracy.

ABSTRACT: Study One - Our objective was to characterize mature range cows based on intake and grazing activity. Starting in the early spring of 2013, 4 experiments were conducted. First, mature range cows (n = 137) were fitted with radio frequency identification tags (RFID) and placed in a dry-lot pen equipped with GrowSafe® technology to monitor DMI of alfalfa hay. These data were then used to assign cows a residual feed intake (RFI) value utilizing the National Research Council (NRC) (1996) model to predict intake of beef cattle. Cattle with negative and positive RFI were characterized as low-intake and high-intake, respectively. In addition, the following data were also recorded: weight (kg), age (mo), days pregnant (d), and body condition score (BCS). Second, 30 mature range cattle were selected from the first trial and fitted with pedometers for 7 d to monitor activity with step counts and estimate distance traveled. Third, mature range cows (n = 25) selected from the first trial were fitted with global position system (GPS) collars, and placed on pinyon-juniper rangeland from 20 June 2014 to 17 September 2014. Forth, mature range cows (n = 28) were fitted with GPS collars, and placed on ponderosa pine rangeland from 17 September 2014 to 15 October 2014. Distance traveled, slope, distance from water, elevation data were collected from both GPS trials. Low-intake and high-intake cows consumed 9.3 and 12.2 kg/d, respectively (P < 0.0001). Low-intake cattle became pregnant sooner (P = 0.002) than high-intake cattle (average of 16 d sooner). Cattle age (mo) equaled 90 and 98 for low- and high-intake cows, respectively (P = 0.04). Weight, predicted DMI, and BCS did not differ between groups (P > 0.06). Step counts for low- and high-intake animals were 5839 and 5383 ± 2089, respectively (P = 0.61), and estimated distance traveled was 4.31 and 5.35 ± 1.66 km d⁻¹ for low- and high-intake animals, respectively (P = 0.77). Low-intake cows (6.23 km d⁻¹) traveled farther (P = 0.005) each day than high-intake cows (5.84 km d⁻¹) on pinyon-juniper rangelands, and high-intake cows utilized (P = 0.013) steeper slopes. No differences were detected (P ≥ 0.06) for distance traveled, distance from water, and elevation for cows grazing ponderosa pine rangeland). However, low-intake cattle preferred (P = 0.046) steeper slopes on ponderosa pine rangeland than high-intake cattle. These results indicate that low-intake animals may travel farther on some rangelands and rebreed earlier. Study Two - Commercial grade heifers (n = 173) born and raised on the University of Arizona's V bar V Ranch from 2012 to 2014 were fitted with radio frequency identification tags (RFID) and placed in a drylot equipped with Growsafe® technology (8 bunks) for 60 d in 3 groups based on birth year in order to calculate DMI, residual feed intake (RFI), ADG, G:F, and residual gain (RG). Birth date, birth weight, weaning weight, age at start of trial, initial trial weight, and final trial weights were also recorded. Residual feed intake scores were utilized to place heifers in one of three treatment groups, low-, medium-, and high-intake. Reproductive and calf data were collected on heifers born in 2012. Means for birth date, birth weight, weaning weight, initial weight, final weight, and ADG did not differ among the three treatments. Residual gain for low-, medium-, and high-intake heifers were different (P < 0.05) at 0.07, 0.00, and -0.07 kg d⁻¹, respectively. Low-intake cattle had an improved (P < 0.05) GF ratio of 0.19 when compared to the medium- and high-intake heifers with ratios of 0.15 and 0.13 (P > 0.05), respectively. Differences (P <0. 05) in DMI were detected with low-, medium, and high-intake heifers consuming 5.2, 6.2, and 7.5 kg d⁻¹, respectively. No differences were detected for pregnancy rate, calving rate, percent bred artificial insemination (AI), percent bull calves, calf birth weight, and calf birth date among treatments (P > 0.05).Study Three - Commercially available GPS tracking collars for cattle are cost prohibitive to most researchers. This paper will present a low-cost alternative to those collars (Knight GPS tracking collars), and provide detailed instructions on where to source materials and how to fabricate inexpensive GPS tracking collars. In addition, the two types of collars will be compared in a study where Brangus cattle (n = 8) were each fitted with LOTEK® 3300 and Knight GPS tracking collars for 31 d beginning 14 March 2015 at the Chihuahuan Desert Rangeland Research Center (CDRRC) 37 km north of Las Cruces, New Mexico. Location, slope, distance from water, distance traveled and elevation were recorded every 10 min. A record of GPS fix rate was logged. No differences were detected (P≥0.369) between collar types for location, slope, or distance from water. However, there was a tendency (P = 0.08) for Knight collars to report a lower estimate for distance traveled at 6171 m d⁻¹ compared to Lotek collars at 7104 m d⁻¹. Fix rate was greater (P≤0.001) for Lotek collars compared to Knight collars at 99.9 and 66.2%, respectively. Study Four - Previously characterized commercial cows (n = 26) were placed into either high (positive RFI) or low intake (negative RFI) groups. On 14 May 2015, 13 high- and 13 low-intake cows were fitted with modified igotU GT-120® GPS logging collars. Cattle were then placed on rangeland for 120 d. The first 30 d period animals transitioned from desert shrubland to pinyon-juniper. From 31 to 60 d, animals grazed pinyon-juniper rangeland. Next, during days 61 to 90, animals transitioned from pinyon-juniper to ponderosa pine, and the last 30 d were spent in ponderosa pine. Time periods will be referred to as month 1, 2, 3, and 4 for days 0 to 30, 31 to 60, 61 to 90, and 91 to 120, respectively. Location, slope, distance from water, elevation, and time spent close to water were recorded every 10 min. No differences were observed in the utilization of elevation or distance traveled, or distance from water (P>0.05). Low intake animals used a higher maximum slope (P < 0.05) during month 3, but slope utilization differences were not detected for other portions of the trial (P > 0.05). Study Five - Hereford sires (n = 35) with 7 or more cow offspring on the University of Arizona V bar V ranch in Rimrock, Arizona were tested at Neogen laboratories in Lincoln, NE for an Igenity Gold genetic profile. Their residual feed intake (RFI), ADG, tenderness, marbling score, milk production percent choice, yield grade, fat thickness, ribeye area, heifer pregnancy rate, stayability, maternal calving ease, birthweight and docility were estimated. Sires were given a genetic RFI score based on their RFI profile and placed into one of three intake groups, low (< 0.5 SD), medium (± 0.5 SD) and high (> 0.5 SD). Performance traits of cow offspring (n = 839) from those sires were also compared based on their sire's intake group. No differences (P > 0.05) were detected among sire intake groups for ADG, tenderness, marbling score, percent choice, yield grade, fat thickness, ribeye area, heifer pregnancy rate, stayability, maternal calving ease, birthweight and docility. Residual feed intake differed among groups (P < 0.05), and high intake cattle had more estimated milk production compared to low intake animals (P < 0.05). Cows from low intake sires were born later in the year (P < 0.05). High intake cattle had a higher (P < 0.05) birthweight and survived longer (P < 0.05) in the herd when compared to low and medium intake cows. Genetic RFI and expected milk production were moderately to highly correlated.

Effects of a short 40-d dry period with only a close-up diet (SHORT) and a conventional 60-d dry period with a 39-d far-off and a 21-d close-up diet (CONV) on milk production, feed intake, blood and rumen parameters, liver gene expression and rumen microbiota profile were compared in 11 second-parity and 15 third and later parity cows. Milk production was recorded daily during the first 16 wks of lactation. Differential liver gene expression was assessed by affymetrix microarray analysis and DNA extracted from rumen samples was subjected to Illumina sequencing for exploring the microbiome profile. The SHORT treatment reduced milk yield and DMI after calving in third and later parity cows, but not in second-parity cows when compared to the CONV treatment. Cows on the SHORT treatment had higher concentrations of NEFA in blood plasma and tended to have higher liver TAG immediately after calving. These effects tended to be greater in third- and later parity cows compared to second-parity cows. Expression patterns of genes involved in β-oxidation at the first week of lactation compared to those at three weeks before calving showed lower hepatic β-oxidation capacity in cows on the SHORT treatment compared to those on the CONV treatment. During this period, the expression of DGAT, a key gene in the triglyceride synthesis, increased in SHORT-treatment cows while it remained unchanged in CONV-treatment cows. The expression patterns of genes involved in gluconeogenesis showed a higher capacity at first week after calving in cows on the SHORT compared to those on the CONV treatment. Our study also showed that the SHORT treatment increased the relative abundance of Firmicutes and reduced the relative abundance of Bacteroidetes compared to the CONV treatment and reduced the shifting of rumen microbiota from before to after calving. Results also demonstrated that the rumen microbiota was more stable in the SHORT treatment during the transition period. Based on these results, a 40-d dry period management with only a close-up diet might be beneficial for second parity cows. However, this treatment may be detrimental for older cows as excessive energy intake and fat deposition during the dry period in these animals result in lower milk production and higher mobilization of NEFA and accumulation of fat in the liver. / February 2016

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Doctor of Philosophy / Department of Animal Sciences / Barry Bradford / The transition into lactation is a period of primary concern to dairy producers because of the tremendous incidence of health disorders observed during this time. Two common disorders that lead to decreases in production and retention within the herd include fatty liver disorder (FL) and ketosis. These two disorders have been commonly associated with negative energy balance, yet recently it has been hypothesized that inflammation is a contributor to the etiology of these disorders. Three individual projects were completed for this dissertation, all involving inflammation. The role of endogenous inflammation was determined by administration of sodium salicylate (SS) to cows for 7 d after parturition, and metabolites and production responses were evaluated. Overall it appears that SS induced hypoglycemic conditions and increased triglyceride accumulation in the liver (while administered), increased lipid mobilization and ketones (2 weeks after administration ended), and increased whole lactation milk production in older cows. A sensitive, specific sandwich ELISA for bovine tumor necrosis factor-[alpha] was developed, which provided the ability to measure “normal” circulating levels of this cytokine. The final study involved inducing inflammation by daily injections of the TNF[alpha] to the early lactation dairy cow. In this model, cows receiving TNF[alpha] had a reduction in dry matter intake, water intake, and decreases in milk production and milk components. Overall, it appears that inflammation is involved in the normal biology of the transition dairy cow and disrupting this can lead to interesting negative effects and some improvements of production; however, when inflammation is much greater it can lead to negative production effects.