Call number: LD2668 .T4 1986 H66 / Master of Science

Master of Science / Department of Animal Sciences and Industry / John A. Unruh / Forty-eight Brahman-cross male calves were fed to 26 mo of age and used to determine carcass cutability and meat quality characteristics of four muscles from intact bulls and steers castrated at 3, 7, or 12 mo of age grown under tropical pasture conditions. Longissimus lumborum (LL), Psoas major (PM), Gluteus medius (GM), and Semitendinosus (ST) steaks were aged for 2, 7, 14, or 28 d for Warner Bratzler shear force (WBSF) analysis. Live weight, carcass traits, and total subprimal yields were not affected by male sex condition. For PM, GM, and ST steaks, WBSF values were similar for steaks from intact bulls and steers castrated at all ages. For both PM and GM muscles, steaks aged for 28 d had the lowest (most tender) WBSF values and steaks aged for 2 d had the highest WBSF values. For the ST, WBSF values were highest for steaks aged 2 d. A treatment × aging interaction was detected for LL WBSF values. At 14 d of aging, LL steaks from steers castrated at 3 mo tended to have lower WBSF values than those from intact bulls. At 28 d of aging, steaks from steers had lower WBSF values than steaks from intact bulls and steaks from steers castrated at 3 mo tended to have lower WBSF values than steaks from steers castrated at 12 mo. For LL steaks from steers castrated at 3, 7 or12 mo, WBSF values linearly decreased with increased days of aging. Although all sensory panel data collected were not statistically different, LL steaks from steers castrated at 3 mo tended to have higher (more tender) scores for overall tenderness than steaks from intact bull. This study indicates that castration at 3 mo would be the recommended production practice as it provided the greatest improvement of LL tenderness over intact bulls with no differences in carcass traits or subprimal yields. The degree of improvement in tenderness due to aging is muscle dependent.

Master of Science / Department of Animal Sciences and Industry / Karol E. Fike / This thesis involves two separate studies that evaluate the effects of different beef cattle management practices on reproduction. The objective of the first study was to determine if feedlot heifers administered melengestrol acetate (MGA) and growth promoting implants could serve as viable oocyte donors for in vitro embryo production. Ovaries from heifers administered MGA and growth promotants (MGA-Implant) and ovaries from heifers not administered either substance (Control) were collected from heifers post-slaughter. Oocytes were harvested and in vitro maturation, in vitro fertilization (IVF), and in vitro culture were completed. Treatment and time interacted to affect the number of oocytes aspirated per ovary (P = 0.07) and the number of zygotes per ovary (P = 0.07). Fertilization (P = 0.90) and cleavage rates (P = 0.80) did not differ between treatments. Blastocyst rates (P = 0.30) and the number of embryos per ovary (P = 0.50) did not differ between treatments. We concluded that beef feedlot heifers fed MGA and implanted with growth promotants seem to be a viable source of oocytes for in vitro embryo production. In the second study, we hypothesized that continuous fenceline exposure of prepubertal beef bulls to cycling beef females would hasten the onset of puberty as well as increase the percentage of bulls passing their initial breeding soundness examination (BSE). Bulls were either exposed to estrous females (exposed) or were not exposed (control). Monthly scrotal circumference (SC) measurements, blood samples, semen evaluations, and bull behavior assessments were conducted. Age at puberty (P = 0.40), SC at puberty (P = 0.50), and weight at puberty (P = 0.30) did not differ between treatments. A similar (P = 0.50) percentage of bulls passed their initial BSE at 363 ± 21.5 d of age (exposed: 87.8%; control: 74.2%). Treatment, month, and stage of the estrous cycle of cows interacted to affect the number of mount attempts (P = 0.05) and the number of flehmen responses (P < 0.001). In conclusion, bulls given continuous fenceline exposure to cycling beef females were neither younger at puberty nor did a greater percentage pass their initial BSE.

Thesis (doctoral)--Sveriges lantbruksuniversitet, 1987. / Thesis statement in Swedish inserted. Includes bibliographical references (p. 20-23).

Examensarbete.

Originally submitted as the author's Thesis (Ph. D.)--Catholic University of America, 1933. / Includes bibliographical references (p. 401-404).

Orientador: Frederico Ozanam Papa / Banca: Rubens Paes de Arruda / Banca: João Carlos Pinheiro Ferreira / Resumo: Dentre as biotecnologias de reprodução que visam acelerar os ganhos genéticos e econômicos dos rebanhos, a congelação de sêmen desponta como uma das principais. O sêmen congelado bovino é utilizado em larga escala há anos e não houve grandes evoluções nas técnicas de congelação visando minimizar os efeitos deletérios do processo nos espermatozóides, colaborando ativamente para o incremento da fertilidade dos rebanhos. Neste trabalho propôs inovações nas técnicas de congelação utilizando uma nova formulação de meio diluente, a introdução da centrifugação para a remoção do plasma seminal pré-congelação e a determinação do tempo ideal de estabilização do sêmen. Foram realizados três experimentos; o primeiro testou o efeito de três diferentes meios diluentes, com ou sem a remoção do plasma seminal, no ejaculado de 40 touros diferentes. Nos resultados exibidos o diluente M20 foi superior (p<0,01) aos demais diluentes na maioria das variáveis pesquisadas a remoção do plasma seminal melhorou (p<0,01) os índices de congelabilidade do sêmen. Outro experimento foi a verificação dos tempos de 60, 120, 180 e 240 min. de refrigeração do sêmen a 5ºC. O tempo de 180 minutos foi o considerado o melhor para a congelabilidade após a verificação dos resultados. No teste de fertilidade foram inseminados 418 vacas e o grupo que foi inseminado com sêmen congelado com M20 sem plasma seminal obteve uma tendência de superioridade (0,05<p<0,10) aos demais grupos. Com os resultados dos experimentos concluiu-se que as inovações propostas por este estudo incrementam os índices de congelabilidade do sêmen bovino / Abstract: Semen freezing is considered as one of the main reproduction biotechnologies that aim to accelerate genetic and economical gains of herds. Frozen bovine semen has been used in large scale for years and there were not great evolutions in freezing techniques to minimize the deleterious effects of the process in spermatozoa, actively contributing for the increase in herds fertility. Innovations in freezing techniques were proposed in this work by using a new formulation of the extenders, introducing centrifugation for the removal of prefreezing seminal plasma and determining the appropriate time for semen cooled. Three experiments were carried out: 1) the effect of three different extenders was tested, with or without the removal of seminal plasma, in the ejaculate of 40 different bulls; results showed that the extender M20 was superior (p<0,01) in relation to the other extenders in most of variables studied. The removal of the seminal plasma improved (P<0,01) semen freezability indexes. 2) verification of 60, 120, 180 and 240 min. times for semen cooling at 5ºC; after results, the time of 180 minutes was considered the most appropriate for freezability. 3) fertility test: 418 cows were inseminated and the group with frozen semen with M20 without seminal plasma obtained a superiority tendency (0,05<p<0,10) in relation to the other groups. The results of the experiments concluded that the innovations proposed in this work increase freezability indexes of bovine semen / Mestre

The objective of this study was to investigate the growth performance, feed conversion efficiency and other production traits of beef cattle performance tested on the farm. Performance testing records (collected from 2000 to 2004), of 444 bulls comprising of six breeds [viz. Aberdeen Angus (n = 42), Beefmaster (n = 135), Bonsmara (n = 97), Drakensberger (n = 64), Nguni (n = 50) and Simbra (n = 56)] from the eastern Free State, Veld Bull Club (VBC) were obtained and analysed. Bulls were performance tested on the farm (Poortije in Vrede district) for 205 days (16.53 s.d.) and finished-off in a feedlot for 100 days. Upon the completion of the entire test period, the bulls were auctioned. Traits studied were: average daily gain (ADG), Kleiber ratio (KR) and veld feed conversion ratio (VFCR), body conditions score (BCS), muscling score (MS), temperament score (TS), tick count (TC), scrotum circumference (SC) and selling price (SP). An analysis of variance with the General Linear Model (GLM) was used to determine the significance within a breed between years, between breeds within a year, the interaction of year x breed, and breeders (breed x year) for all the dependent variables. Aberdeen Angus bulls showed a significant difference for all traits analysed except for SC and SP. Beefmasters did not only differ in BCS and TS. Bonsmaras differed in all traits analysed except for FWT, SC and SP. Unlike the other breeds, the Drakensberger had more traits that they showed no significant differences viz. IWT, FWT, MS, TS and SP. The Nguni showed significant difference in all traits analysed except for IWT, TS and SC. Finally, the Simbra also did not differ significantly in five of the eleven traits measured viz. FWT, MS, TC, SC and SP. According to these results, there is a significant variation within beef cattle breeds on rangeland in certain performance and other production traits such those measured in this study. This suggests that, although selection for desirable traits within-breed may be slow, the within-breed selection and exploitation has a role to play in improving long-term herd functional efficiency. During the feedlotting period, none of the breeds showed a significant difference in ADG, suggesting that, given a favourable environment, each animal will have an equal opportunity to perform at its optimum genetic potential. This further implies that in a production environment where feed resource is not the limiting factor, higher production efficiency may well be accomplished by each animal. / Dissertation (MSc(Agric): Animal Production Management)--University of Pretoria, 2008. / Animal and Wildlife Sciences / MSc(Agric) / unrestricted

In the United States, symptoms caused by pathogenic strains of Escherichia coli are on the rise. A major source of these pathogenic strains is the E. coli in the digestive tract of cattle. The purpose of this project was to determine if E. coli are transferred between individuals of the same species and if interspecies transmission is possible. Proximity of cattle was also studied as a contributing factor to the transfer of E. coli. To accomplish this goal, E. coli isolates from cattle and cohabitating ground squirrels were compared through a new method of bacterial strain typing called pyroprinting. Bulls from the Cal Poly Bull Test were sampled every summer from May to September when around 200 bulls from ranches across California are housed together to be tested and eventually auctioned off. The impact of cattle origin (ranch, city) and habitation (pen) on E.coli isolate strain type were evaluated via pyroprinting . The cattle were studied to see if transfer was related to proximity of cohabitation. Since the complete population of intestinal E. coli could not be sampled, transfer could not be directly seen. The probability of sharing E. coli in each time point was used to infer transfer. There was an increase in the probability of sharing E. coli from the May sample date to the September date, indicating that some form of transfer was occurring. There was an even greater increase in the probability of sharing E. coli when the bulls were housed in close proximity. Lastly, ground squirrels cohabitating in the area were found to house some of the same strains as the cattle. This makes transfer between squirrels and cattle a possibility. Overall, this paper shows that the intestinal E. coli composition of bulls may be readily altered by the introduction of new bulls into a population.

The biological process of estrus in cattle is known to initiate behavioral responses as a result of fluctuations in hormones, which may alter time budgeted for feeding. The current study aimed to quantify these variations that may exist in feed intake and behaviors in the days pre and post estrus. For this study, 517 estrous cycles in crossbred beef heifers of divergent sizes were used to analyze the impact of estrus behavior on feeding behavior with or without the presence of a bull. There were few differences in estrus behavior among heifers of divergent sizes, however the presence of a bull influenced all estrus activity parameters. Our findings indicate that feed intake and behaviors were sharply decreased on the day of estrus, but returned to baseline levels the following day. Thus, decreases in feed intake and behavior may serve as an additional tool indicating the onset of estrus.