Browsing by Subject "Calves"
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Item A comparison of the weaning weight of Hereford cattle selected by four different criteria(Texas Tech University, 1971-05) Gibson, Kirkwood WatsonNot availableItem Acclimation of Holstein Calves to Transit Stress: The Integration of Endocrine, Immune, and Behavior Systems(2012-10-19) Adams, AmberLittle is known about the adaptation of livestock to repeated transport. This study determined how repeated transport affected calf feed intake, plasma cortisol (CORT), post-transport behavior, and the expression of immune-related genes. Thirty-six 4-month-old Holstein steer calves were housed in groups of six with each group randomly assigned to either transport (T) or control (C) treatments. The T calves were hauled for 6 h in a 7.3 m x 2.4 m goose-neck trailer, at an average density of 0.87 m2/calf, every 7 d for five consecutive weeks. Individual daily intake was determined using Calan gate feeders. Blood samples were obtained in the trailer or home pen via jugular venipuncture before loading, and after 2, 4, and 6 h of transport. Samples were analyzed for CORT, serotonin, tryptophan, and the gene expression of interleukin-4 (IL-4), interleukin-6 (IL-6), chemokine (C-X-C motif) receptor 2, interleukin-12, toll-like receptor-4, toll-like receptor-2, and 5-hydroxytryptamine receptor 2A in leukocytes. Behavior was recorded for transported calves at 5-min intervals for 1 h after return to their home pens. The C calves had a higher feed intake than T calves overall (P = 0.01), on the day of transport (P = 0.007), and the day after transport (P = 0.02). Pre-transport CORT concentrations did not differ by treatment (P = 0.77) or trial (P = 0.32). However, the T calves had higher response CORT concentrations than C calves during Transport 3 (P = 0.006), Transport 4 (P = 0.001) and Transport 5 (P = 0.02). The T calves had the highest response CORT concentrations after 2 h of transport and the lowest response CORT concentrations after 6 h of transport (P < 0.0001). Treatment did not affect gene expression in leukocytes, however, the expression of IL-4 (P = 0.01) and IL-6 (P = 0.05) was significantly lower after 2 h of transport than any other sampling times. These results suggest conflicting conclusions on whether the calves started to acclimate after being transported five times. However, CORT and gene expression differences occurred in response to the blood sampling regimen, which may provide insight to how calves acclimate during prolonged stress.Item Economic and production efficiency aspects of variable energy density in the diets of identical twin calves(Texas Tech University, 1989-05) Robbins, Randall DarylDespite the large amount of research evaluating the effects of various levels of nutrition on cattle growth, feedlot performance and carcass development, conflicting opinions remain. O'Donovan (1984), in a review article, summarized these studies in an attempt to find a common denominator that would help explain the variable but he had little success. Obviously a major contributing factor to these diverse results would be extensive variation in experimental methodology. Cattle used in experimentation differ in biological type, age, sex, diet and previous environmental treatment. Investigations have been conducted restricting energy consumption so that animals lose weight, maintain their weight or gain weight (gains are limited below maximum gain potential). In addition, proportion of maximal weight gain by energy restricted animals varies considerably between studies. Type of restriction also is different. Cattle can be restricted by reducing total daily feed consumption, reducing dietary energy concentration through feed ingredient manipulation or combinations of both. Length of restriction periods also differs. Some researchers reported that cattle were maintained on low energy diets for the entire feeding period while others provided a period of high energy consumption or a refeeding period. Cattle subjected to these diverse growth limiting treatments then were compared to cattle consuming a common dietary treatmentcontinuously fed animals consuming high energy diets. Consequently, comparisons then were made with cattle at different or similar weights and various ages.Item The effects of beef cow milk yield and composition on calf growth and cow reproduction(Texas Tech University, 1998-12) Larremore, Michael BardinDuring 1997 and 1998, purebred Angus cows were evaluated in three separate trials at the Texas Tech Beef Center. In 1997, the cows in this study were randomly separated into two groups and supplemented with cottonseed meal, extruded whole cottonseed and extruded cull cottonseed at three different time periods. The cows were milked during each period of the trial. Cow and calf weights were analyzed as well as milk yield and composition. The following year, these same cows were fed a commercial direct-fed microbial. These cows were again separated into two groups and milked throughout the trial. Cow and calf weights, milk yield, milk fat, milk crude protein and somatic cell count were analyzed. The third trial conducted analyzed the effects of milk yield in Angus cows on udder conformation, teat measurements and reproduction. Milk yields were collected each year as well as udder conformation scores. Reproduction was recorded by analyzing the time period between calving and first artificial insemination dates. Results form the first trial showed an increase in milk yield (P < .05) when extruded protein supplements were fed. Cows that were fed cottonseed meal also gained more weight than those fed extruded products. When the direct-fed microbial was fed during the second trial, cow weight gain showed to have increased (P < .05) during two of the five milkings. Percent milk fat as well as somatic cell count were also increased (P < .05). In the third and final trial, results showed that milk yield does statistically effect reproduction as well as udder confirmation traits. A negative correlation was also recognized on first artificial insemination interval when analyzed against milk EPD's for 1995.