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Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on June 11, 2009). Includes bibliographical references.

Four groups of weanling Hereford heifers were placed on four different winter planes of nutrition for a period of two years according to the following pattern: Group I - Low plane of nutrition Group II - Medium-low plane of nutrition Group III - Medium-high plane of nutrition Group IV - High plane of nutrition During the summer seasons the heifers were kept on pasture providing the same feeding level for all animals. The one year old heifers were bred during the months of June and July. All animals were weighed weekly and feed consumption was recorded weekly. To illustrate the growth rate of the heifers, K-values were calculated for all animals by the method of least squares and their growth curves were constructed. At the end of the second winter period all parturition data were carefully recorded and the rate of growth of the calves studied. From the results obtained in this experiment the following conclusions can be drawn: (1) The first post-weaning winter period is very important in regard to the feeding level of young growing heifers. The medium-low plane of nutrition (Group II) showed the best results from the economic point of view. (2) Young heifers can be bred as yearlings if the previous winter-feeding level allows them to grow continuously and to reach at least 700 pounds body weight before the breeding period starts. (3) The gestation period did not result in a decreased growth rate of the bred heifers. (4) The physical difficulties of parturition in two year old heifers do not appear to be insurmountable if the winter plane of nutrition is adequate. (5) The lactation period means a heavy drain on the young female hence a high level of nutrition must be provided in terms of sufficient amount of pasture dry matter during the grazing season. (6) Average birth weight of calves was 62.9 pounds, being higher for bull calves than heifer calves. (7) Pasture dry matter requirements for beef cattle may be calculated from the following equation: DM = 0.17 w•⁷ (w is animal weight given in pounds) / Land and Food Systems, Faculty of / Graduate

This thesis is the study of the literature pertinent to the assessment of growth in addition to the analysis of growth data obtained from the Albino Rat, Yorkshire Swine, Black-Tail Deer and a group, of ten Hereford Bulls. It has been concluded that animals grow at a constant percentage rate relative to body weight over each distinct portion of their growth curve. A significant error in the expression of rate of gain is introduced if animals growth rate is calculated over any but an instantaneous period. The latter is possible because growth of an animal body is directly proportional to the protoplasmic mass, a first order reaction and as such is exponential and when the expression is integrated, the slope of the' regression line, logarithm of body weight on time is provided over the period when relative growth rate is constant. From the results of ration variations with male Wistar rats it was concluded that upon returning to ad libitum feeding they will grow at the same relative rate as their controls despite thirty per cent reduction below ad libitum intake over periods up to two thirds of the birth to sexual maturity phase. The extrapolation is made that beef bull calves proceeding from varying environments normally, experienced on pure-breeding establishments will not provide biased data when placed on a test ration and allowed a period for the rumen microflora to become adjusted to the new ration. / Land and Food Systems, Faculty of / Graduate

In Study I alfalfa-bermuda grass hay or oat straw was fed with rolled barley, pelleted beet pulp, soybean oil meal and cracked wheat, in various proportions, in twenty protein-supplemented rations to immature Hereford steers. A control ration of 10% long straw, 78% rolled barley and 12% soybean oil meal was included. The best results were obtained with a roughage level of 10%. However, it was shown that it was feasible to feed roughage levels as high as 40% without detrimental effects to either average daily gain, feed efficiency, or carcass quality. In Study II various feed grains were fed in the ratio 90:10 (concentrate to roughage). The Canadian feed grains of barley and wheat were compared with corn. Various ratios of these feed grains were also compared. Excellent gains and feed efficiencies were obtained on all rations and it was shown that the cost of the grains available would be the largest factor in determining which to use. / Land and Food Systems, Faculty of / Graduate

In recent years research has expanded the knowledge one has of the actual costs Involved in the growth process of meat producing animals. These studies have shown that at the higher weights a larger proportion of the gains are made up of high cost fat tissues. Initially it was thought that this fat deposition served a useful purpose in making meat tender, but it is now known that this original premise was incorrect. Fat is no longer desired by the consumer above a certain minimum level. The feedlot operator therefore has the option of taking advantage of this phenomenon and shipping animals at a lighter weight, at a lower cost, and with the possibility of doing this at a higher profit margin than is the case at present. A study has been made of the total costs involved in the production of a pound of live animal weight under feed-lot conditions and of the changes in these costs that occur as the animal achieves a higher total body weight. It was found that on the average, each additional pound of gain requires between .006 and .028 more pounds of feed than did the previous pound. As a result of these studies, an Economic Shipping Weight was proposed as a means of signifying the beginning of an increase in the average cost of production and hence, a decrease in. the rate of return to investment. The Economic Shipping Weight was defined as that weight at which the feed cost of an additional pound of gain is equal to the current value of a pound of live animal weight. In the application of this theoretically derived shipping weight to a practical feedlot operation having a total fixed investment of $162,938.00, it was found that the total return to investment was increased from $8,822 to $22,503. This increase resulted in a change in the rate of return to investment from 5.44% to 13.81%. The major part of this increase in the total margin was due to a reduction in the average feed cost of each pound of gain from 20.2¢ to 17.4¢. The total margin between sales revenues and animal purchase and feed costs was increased by $5,485.00. This reduction in feed costs was caused by a lowering of the average amount of feed required per pound of gain as the animals were theoretically shipped 41 lb. lighter than in the actual operation. Originally they were sold at an average weight of 998 lb. Seventy-six percent of them received a Choice grade. The analysis was carried out under the assumption that they would only receive a Good grade price at the Economic Shipping Weight. Other savings arose from a reduction in the total interest charges on feed purchases because of the lower total feed consumption, and from a reduction in the total feed freight bill. These two savings amounted to $4,716.00. The remaining saving resulted from a smaller in process feed cost. A study was also made of the relative advantages for the beef industry of stressing the production of Good grade beef as opposed to Choice grade beef. It appears that an economic advantage could be gained by the packing house operators, feedlot operators, and retailers, if this were to become the main grade produced. As consumers are now making most of their meat purchases on the basis of a lack of fat, Good grade meat is also more acceptable to them. The feasibility of using Dairy breed animals as a meat source was examined as a means of producing leaner meat at a lower cost than beef breed meat. These animals were shown to have a definite economic advantage at any body weight because they used feed more efficiently. Dairy breed bulls were also shown to produce meat more economically than any other dairy or beef breed animal and resulted in meat which is more desirable to the consumer. Because of their greater efficiency they had an Economic Shipping Weight of 1050 lb. as opposed to 900-950 lb. for beef breed animals. There was, however, a certain risk involved in their production because of the wide variation in the grades they may receive. / Business, Sauder School of / Finance, Division of / Graduate

In the first study 30 Hereford steers were fed a ration of either steam rolled barley or a 50:50 mixture of barley and alfalfa leaf meal pellets. In addition to these basal rations groups of animals on each, were fed a protein supplement with Diethylstilbestrol (D.E.S.) at levels such that each animal received either 0, 10, or 18 mgm. of D.E.S./head/day. The hormone treatment of animals fed the barley ration did not affect the growth rate or feed efficiency but a significant increase in hemoglobin levels from 8.96 to 10.40 gm. % Hb. and in the red cell counts from 8.25 million/mm³ to 9.50 million/mm³ resulted. A similar increase in red cell count from 8.7 million/mm³ to 9.6 million/mm³ resulted from hormone treatment of the animals fed the 50:50 barley-alfalfa ration. There was also an apparent, but insignificant, increase in haematocrits on both rations due to hormone treatment. This treatment resulted in a significant increase in the ratio of blood acetic to propionic acids on the barley ration from 82.3:1 to 195.3:1 but, did not cause a change in total blood volatile fatty acids (V.F.A.). There was an increase in the blood acetic-propionic ratio on the barley-alfalfa ration due to D.E.S. addition. This was from 97:1 to 159:1 at 10 mgm. D.E.S./head/day, to 233:1 at 18 mgm. of D.E.S./head/day but, was insignificant due to high within-group variability. There was an apparent difference between the three blood parameters (Haematocrit, Hemoglobin, Red Cell Counts) on the two control rations due to the higher iron content of the barley-alfalfa ration. This, and an apparent decrease in thyroid weights were shown to be insignificant. In the second study, using an all barley ration and a protein supplement containing a high iron concentration, there was a stimulation in growth rate and feed efficiency due to D.E.S. The animals were started on D.E.S. at 718 lb. (cf. 465 lb. for Study I). The increase in the three blood parameters was again observed on the low iron rations but, on the high iron ration there was an apparent but insignificant decrease in these parameters due to D.E.S. The animals fed the control high iron ration produced an haematocrit and red cell count that was significantly higher than that of the control low iron ration, indicating a possible deficiency in the original supplements. On the low iron ration there was a significant increase in total blood V.F.A. from 0.88 meq./l. to 1.19 meq./l. in response to D.E.S. supplementation but, on the high iron ration the increase was insignificant. The difference between the two control rations (0 D.E.S., high and low iron) total blood V.F.A. was shown to be significant, 0.88 vs. 1.08 meq./l. at P< .05. A method of preparation of feed and liver samples for analysis of their mineral content by atomic absorption spectrophotometry was developed. There was shown to be a significant increase in liver copper storage on the low iron ration with increased levels of D.E.S. The feeding of a high iron ration caused a significant decrease (P< .05) in the level of copper in the liver from 84 ppm. to 37 ppm. A slight but insignificant increase in liver iron levels on the high iron ration and through the treatment with D.E.S. was observed. / Land and Food Systems, Faculty of / Graduate

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