35 pp. / The dependency of Arizona ranchers on federal lands has been well documented. Mayes and Archer (1982) estimated that public and state grazing lands outside of the Indian reservations account for 85% of the total grazing land in Arizona. The partnership between private ranchers, state lands, and the federal government comes with many complex factors that influence the cost of doing business both in terms of variable and fixed costs. Not only are the regulations, fees, and enforcement of regulations a challenge for managing mixed land ownership, but additional costs from vandalism, theft, and daily disruptions of operations add to the normal operating expenses (Ruyle et al., 2000). Ownership and maintenance of range improvements, such as wells, spring development, and dirt tanks, etc., is also complicated by the rangeland ownership mix. This study is designed to examine the cost of ranching for different geographic areas in Arizona and show how different production costs exist throughout the state.

Periconceptional heat stress is known to reduce the likelihood of establishing pregnancy; however, some conceptuses will survive. Of the pregnancies that continue to term, a proportion will be heifers which are retained as replacement animals. Alterations that occur as a result of exposure to thermal stress during such critical stages in development likely result in differential performance between the heat stress-conceieved (HSC) cows and thermoneutral-conceived (TNC) cows. National Dairy Herd Improvement Association data was obtained from Dairy Records Management Systems. Records (n =14,189,891) included cows born between 1977 and 2010 in FL, GA, SC, MS, LA, AL, and TX. Records were edited to include only Holsteins born between 2000 and 2010 (n = 704,419). Conception dates were calculated by subtracting 276 d from the recorded birth date. Records for cows conceived within the months of June, July, and August were retained as HSC cows; cows conceived within the months of December, January, and February were retained as TNC contemporaries. Significant differences (P<0.01) in mature-equivalent milk yield were observed in all first lactation cows, and in cows that were retained within one herd for three lactations. In the latter group alterations in milk compositions were statistically significant (P<0.01), but not biologically so. Furthermore, significant differences (P<0.01) in days open were observed in cows retained within one herd for three lactations. The effects of periconceptional heat stress were particularly noticeable during seasonal comparisons, with HSC cows seemingly having an advantage in subsequent episodes of heat stress. / Master of Science

The objective of this experiment was to evaluate the effects of free-choice intake of sodium bentonite and sodium bicarbonate on physiological and production parameters. Eight Jerseys and seventeen Holsteins (four fistulated) were randomly assigned to two groups to equalize stage of lactation, age and production history. Two diets were fed: diet 1 without added sodium bicarbonate and diet 2 with sodium bicarbonate added at 1.2% of dry matter. Each group followed a different diet regime: 1) diet 1 with no free-choice (D1-NFC), 2) diet 2 with no free-choice (D2-NFC), 3) diet 1 with free-choice (D1-WFC), and 4) diet 2 with free-choice (D2-WFC). Free-choice options of sodium bentonite and sodium bicarbonate were offered side by side in a covered feeder to breed groups. Diets were changed every 10 d to provide 8 periods with a repetition of each diet regime. All diets were adjusted to 17% ADF and 17% CP. There were no differences with either breed among diets for blood and fecal observations or milk protein. Urine specific gravity was lower in both breeds when sodium bicarbonate was force-fed. Holsteins force-fed sodium bicarbonate had greater intake and milk production than Holsteins not force-fed. In Jerseys, milk urea nitrogen (MUN) decreased when sodium bicarbonate was added to the TMR. During periods in which cows were allowed free-choice access to sodium bentonite and sodium bicarbonate, Jerseys had higher urine pH, fat-corrected milk, MUN, and dry matter intake (DMI), and Holsteins had higher milk fat percentages and fecal pH. / Master of Science

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No description available.

Lactating dairy cows convert 25 to 35% of intake N to milk N, and a part of the remaining N ends up in the environment, causing pollution. Dairy cows absorb amino acids available in the small intestine supplied mainly by digestion of microbial protein and ruminally undegraded feed protein (RUP). Ruminally degradable feed protein (RDP) is the major supplier of N for microbial protein synthesis. Most of the excess RDP will be degraded to ammonia and eliminated as urea in urine. Thus, avoiding excess RDP in dairy cattle diets is important in reducing environmental N pollution. The objectives of the work in this dissertation were to test the hypothesis that lactating dairy cows, when fed varying dietary RDP, can maintain feed intake, milk and milk protein yield, ruminal metabolism, passage of nutrients out of the rumen, and N excretion. The first study investigated the effects of decreasing RDP in lactating dairy cow diets on feed intake, milk production and apparent N efficiency. Forty mid-lactation cows (36 Holstein and 4 Jersey × Holstein cross-breds) were fed a diet containing 11.3% of diet dry matter (DM) as RDP for the first 28 d (covariate period). From d 29 to 47 (treatment period) cows were randomly assigned to 1 of 4 diets containing constant RUP (7.1% of DM) but 11.3, 10.1, 8.8, or 7.6% of DM as RDP. Reducing RDP in diets linearly decreased DM intake and tended to decrease milk yield. Milk protein, fat and lactose contents, milk protein yield, body weight, and plasma essential amino acids were unaffected by reduced dietary RDP. However, milk urea-N concentration and milk fat yield decreased linearly with reduced dietary RDP. The apparent efficiency of N utilization for milk N production increased linearly as dietary RDP was reduced. As RDP declined in diets, linear reductions in DM intake and milk production suggested that these cannot be maintained below NRC recommendations of RDP for cows in this study. The aim of the second study was to test the hypothesis that decreasing dietary RDP in lactating dairy cow diets can maintain ruminal metabolism and flow of nutrients out of the rumen and reduce nitrogen excretion. This study was designed as a replicated Latin square with 4 periods of 21 d each. Four treatment diets containing decreasing RDP and constant RUP similar to the first study were used. Three ruminally and duodenally cannulated and 4 ruminally cannulated lactating Holstein cows were randomly assigned to one of the four dietary treatments. A double marker system with Co-EDTA and Yb-labeled forage as markers was used to determine ruminal outflows of nutrients from omasal samples and nutrients reaching the intestine from duodenal samples. Ruminal microbial protein flow was observed using ¹⁵N as an external microbial marker. Feed intake, milk yield, milk composition, and urine and feces output were determined in the last week of each period. Ruminal fluid samples were taken 2 and 4 h after feeding to determine ruminal NH₃-N and volatile fatty acid concentrations. Outflows of nutrients from the rumen were determined by analyzing omasal samples collected over a 24 h feeding cycle in the last week of each period. Reducing dietary RDP decreased protein intakes while DM and fiber intakes were unaffected. Ruminal NH₃-N concentrations linearly declined and peptides and amino acids were unaffected with reduced dietary RDP. A trend for a linear decline in ruminal outflows of microbial N and total N was observed with decreasing dietary RDP. Ruminal volatile fatty acids concentrations were unaltered by feeding treatment diets. Ruminal outflows of DM and acid detergent and neutral detergent fibers were unaffected by treatments. Treatment diets did not have any effect on milk yield and milk composition. However, milk urea-N and milk fat yield decreased linearly with decreasing dietary RDP. Reducing dietary RDP did not affect milk and milk protein yields but did result in greater body protein mobilization. Fecal N output was unaffected however, urine volume and urine N output decreased linearly suggesting reduced environmental N pollution. There was a trend for a linear decrease in total body N balance, but no significant effects on calculated ruminal N balance as dietary RDP decreased. Linear reductions in microbial N leaving the rumen were due to decreased ruminal NH₃-N as peptides plus amino acids and energy supply were unaffected. The linear reduction in milk production and microbial N flow in the first and second studies, respectively, did not support our hypothesis that lactating dairy cows can be fed dietary RDP below current NRC (2001) recommendations without affecting animal performance. The need to raise 15% more cows to alleviate the loss in production may nullify the advantage in reduced N output into the environment by cows fed lower dietary RDP. / Ph. D.

Four Holstein cows with ruminal and duodenal cannulas were used to evaluate the effects of dietary fatty acylamides (canolamide) or abomasally infused conjugated linoleic acid on milk production and composition. In the first experiment, cows were fed diets with no supplemental fat(control), or the control diet supplemented at 3.3% of DM with canola oil, canolamide, or a mixture of equal amounts of canola oil and canolamide in a 4 x 4 Latin square. DMI and milk yield were decreased when cows were fed canolamide. Intake and duodenal flow of diet components and fatty acids were decreased by canolamide, but their apparent digestibilities were not affected by treatment. Fat supplementation decreased concentrations of fatty acids with 8 to 16 carbons and increased oleic acid in milk. In the second experiment, cows were infused abomasally with 100 g Linoleic acid (LA) or a mixture of 100 g LA plus 100 g conjugated linoleic acid (LA-CLA) for 24 h in a single crossover design. Infused CLA was a mixture of 70% cis-9, trans-11-18:2 and 30% trans-10, cis-12-18:2. Milk yield and DMI were not affected by treatment. Milk fat percentage and yield were decreased by LA-CLA. Concentration and yield of oleic and arachidonic acid and fatty acids with 6 to 16 carbons in milk were reduced by LA-CLA. Stearic acid and CLA concentrations in milk, however, were higher in response to LA-CLA. Infusion of LA-CLA led to increased (from 23 to 45%) concentration of unsaturated fatty acids with a concomitant decrease (from 70 to 42%) in saturated fatty acid concentration in milk fat. Feeding canolamide at 3.3% significantly decreased DMI and milk yield compared with canola oil or the mixture of canola oil and canolamide. However, results indicated that oleic acid and CLA concetration in milk fat can be increased proportionally to their flow into the small intestine. Utilization of these fatty acids for milk fat synthesis may cause a reduction in the amount of medium and short chain fatty acids synthesized de novo within the mammary gland. Furthermore, CLA appears to be a potent inhibitor of milk fat synthesis and desaturation of stearic and linoleic acid. / Master of Science

The use of antibiotics in dairy cattle has the potential to stimulate the development and subsequent fecal dissemination of antibiotic resistance genes (ARGs) in bacteria. The objectives were to use metagenomic techniques to evaluate the effect of antibiotic treatment on ARG prevalence in the fecal microbiome of the dairy cow and to determine the temporal excretion pattern of ARGs. Twelve Holstein cows were assigned to one of four antibiotic treatments: control, pirlimycin, ceftiofur, or cephapirin. Fecal samples were collected on d -1, 1, 3, 5, 7, 14, 21, and 28. Samples were freeze-dried and subjected to DNA extraction followed by Illumina paired-end HiSeq sequencing and quantitative polymerase chain reaction (qPCR). Illumina sequences were analyzed using MG-RAST and the Antibiotic Resistance Gene Database (ARDB) via BLAST. Abundance of ampC, ermB, tetO, tetW, and 16S rRNA genes were determined using qPCR. All data were statistically analyzed with PROC GLIMMIX in SAS. Antibiotic treatment resulted in a shift in bacterial cell functions. Sequences associated with 'resistance to antibiotics and toxic compounds' were higher in ceftiofur-treated cows than control cows. Ceftiofur-treated cows had a higher abundance of 𝛽-lactam and multidrug resistance sequences than control cows. There was no effect of treatment or day on fecal tetO and ermB excretion. The relative abundances of tetW and ampC were higher on d 3 post-treatment than d 5 and d 28. In conclusion, antibiotic use in dairy cattle shifted bacterial cell functions and temporarily increased antibiotic resistance in the fecal microbiome. / Master of Science

Optimizing forage productivity is essential to reduce pasture seasonality and ensure available forage to meet the nutritional needs of livestock. This study explores the risk-buffering ability of warm-season forages to fill the summer slump gap in production of cool-season grasses. Small plot experiments were initiated in summer of 2008 in Kentland Farm, Northern Piedmont AREC and Shenandoah AREC, Virginia. Treatments included endophyte-infected tall fescue (KY31 E+), endophyte free tall fescue (KY31 E-), novel endophyte tall fescue (MaxQ), Crabgrass in combination with endophyte-infected tall fescue, Teff, Bermudagrass (BG), and Caucasian bluestem (CB). Plots were harvested May through October of 2009 and 2010 at the late boot stage at a cutting height of 10cm. Subsamples were analyzed for dry matter and nutritive value. To assess risk, bootstrap distributions of biomass and quality data were generated by Monte Carlo simulation and compared against an objective function defined as 59 kg ha-1 d-1 forage yield; 10% CP; 60% TDN. Regardless of variability, warm-season grasses produced biomass yields and nutritional values adequate to fill the summer slump from cool-season forages and demonstrated a higher probability of meeting the minimum requirements in July, August and September. Teff was most consistent in meeting the minimum requirements in mid-summer. However, with good conditions for establishment, both BG and CB can help to fill the gap in summer months when compared to cool-season tall fescue. Bootstrap distributions provide producers with a tool that links their production goals with a measurable value of production risk. / Master of Science

Nutritional management of dairy cattle is of importance to the industry due to its influence on production performance and association with large expenses for producers. Current ration formulation may be improved by predicting feeding recommendations for individual animals, rather than groups of animals, through precision feeding. Automated feeding systems (AFS) designed to deliver individual rations must include response-based models that utilize individual cow production data to make feed recommendations. These models require large data sets of individual cow responses to a variety of nutritional interventions. As a result, an experiment was designed to collect individual response data from 24 Holstein cows fed supplemental top dresses. After analyses, dry matter intake (DMI), milk yield (MY), milk fat yield, milk protein yield, feed efficiency, and activity were significantly affected by top dress (P < 0.001). These results suggest opportunity to use precision feeding to implement economically optimal ration recommendations designed to increase dairy cow production. Therefore, a second experiment was conducted in order to develop and test two algorithms that targeted individualized feeding to increase feed efficiency. Milk protein percentage (P = 0.008) and feed efficiency (P < 0.001) were significantly affected by a 3-way interaction between top dress, algorithm, and week. These results highlight the opportunity for precision feeding to increase the efficiency of individual dairy cows. Although the control group resulted in greater income over feed costs than either of the developed algorithm feeding strategies, algorithm refinement and modification may result in more efficient feeding recommendations that are economically viable. / Master of Science / Nutritional management of cattle is crucial to the dairy industry. The feeding of dairy cattle is the largest expense for producers and directly influences cow production. In particular, precision feeding of dairy cattle may have the ability to lower costs for farmers and increase the productivity of dairy cows. Currently, cattle are fed in group configurations, where cows with similar nutrient requirements are offered the same diet. However, individually feeding dairy cows utilizing precision technologies may have the ability to increase the production performance of cattle. Utilizing precision feeding to individually feed dairy cattle requires automated feeding systems (AFS) designed to decrease the additional labor associated with feeding animals as individuals. However, algorithms designed to predict individual animal nutrient requirements are lacking for use in AFS. As a result, large data sets of individual cow responses to varying diets are necessary to train algorithms designed to predict unique ration formulations for individual animals. Two experiments were developed to collect individual animal production responses that were used to develop two response-based algorithms capable of influencing feed efficiency of individual cows. The results from these experiments highlight the potential for precision feeding of dairy cattle to influence individual animal feed efficiencies and milk production. Future improvements in algorithm development and training are necessary in order for these feeding strategies to be economically worth the investment of AFS on commercial dairy farms.