Manifestation of estrous behavior and subsequent progesterone concentration at timed-embryo transfer in cattle are positively associated with pregnancy success of recipients

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Meat characteristics of nellore cattle fed different levels of lipid-based diets

The objective of this study was to determine the effect of the dietary inclusion of lipid-based diets (whole cottonseed and protected fat) on the centesimal composition, fatty acid profile, and sensory properties of meat from finishing Nellore cattle. The study was carried out from August to October 2009. Thirty nine uncastrated Nellore males with average initial body weight of 494.1 ± 10.1 kg and 36 months of age were housed for 63 days in pens with thirteen animals each. A completely randomized design with three treatments and thirteen replications was used. The treatments evaluated were: feed with 2.50% cottonseed (control diet); feed with 11.50% cottonseed; and feed with 3.13% cottonseed added of protected lipid (PL), all on a dry matter basis. No differences between treatments were observed for moisture, protein, and ash contents. However, the addition of protected fat caused an increase in the percentage of ether extract in the meat. Diets containing cottonseed or protected lipid did not affect fatty acid concentration in the meat. The intensity of the aroma, strange aroma, flavor, strange flavor, juiciness, color, and overall appearance were similar between treatments, except for tenderness, which was positively affected in cattle fed a diet in which the only lipid source was cottonseed. The study demonstrated that the addition of PL in the diets of finishing cattle led to greater levels of intramuscular fat, but to less tender meat than the other treatments.

Environmental and Farm Management Factors Associated with Tuberculosis on Cattle Farms in Northeastern Michigan

Objective—To identify major environmental and farm management factors associated with the occurrence of tuberculosis (TB) on cattle farms in northeastern Michigan. Design—Case-control study. Sample Population—17 cattle farms with infected cattle and 51 control farms. Procedure—Each case farm (laboratory confirmed diagnosis of Mycobacterium bovis infection) was matched with 2 to 4 control farms (negative whole-herd test results within previous 12 months) on the basis of type of farm (dairy or beef) and location. Cattle farm data were collected from in-person interviews and mailed questionnaires. Wildlife TB data were gathered through state wildlife surveillance. Environmental data were gathered from a satellite image-based geographic information system. Multivariable conditional logistic regression for matched analysis was performed. Results—Major factors associated with increased farm risk of TB were higher TB prevalence among wild deer and cattle farms in the area, herd size, and ponds or creeks in cattle housing areas. Factors associated with reduced farm risk of TB were greater amounts of natural open lands in the surrounding area and reducing deer access to cattle housing areas by housing cattle in barns, barnyards, or feedlots and use of electrified wire or barbed wire for livestock fencing. Conclusions and Clinical Relevance—Results suggest that certain environmental and management factors may be associated with risk of TB on cattle farms.

RB30-252 Sex and Age as Factors in Cattle Feeding

Varying economic conditions and changes in the demands of the meat consuming public have been responsible for the turns that have taken place in the beef industry during recent years. Both feeder and producer must recognize and conform to these changes if they are to continue in business. Among the most important of these changes have been the turn toward the marketing of lighter cattle and the gradual disappearance from feed lots of two- and three-year-old animals. Furthermore, the cattle population of the United States is fast reaching stabilization with the resulting effect that more heifers are being marketed, since only one-fourth of the heifer crop is needed to replace worn-out breeding animals. Realizing the increasing importance of the heifer problem from the standpoint of the producer, feeder, and consumer, the Nebraska Experiment Station undertook to compare steers and heifers in a series of trials both in the feedlot and in the beef. It was hoped that these experiments would yield results which would bring out existing differences, if any, between steers and heifers both in quality and quantity of beef produced and thus provide or disprove many of the complaints against heifers. The results of these trials are summarized in this bulletin. Age as well as the sex factor has been considered, since two-year-olds, yearlings, and calves were included in these trials.

Interaction Between Roughages and Corn Milling Byproducts in Finishing Cattle Diets

During ethanol production, starch is the primary nutrient fermented and the remaining byproducts are excellent sources of fiber and protein. In addition, inclusion of byproducts in finishing diets may reduce the incidence of acidosis. As a result, roughage level and quality could potentially be reduced in finishing diets containing byproducts. Three experiments were conducted to examine the effects of roughage and wet corn gluten feed (WCGF) in finishing cattle diets containing corn distillers grains plus solubles. Cattle fed finishing diets containing wet distillers grains plus solubles (WDGS) with no roughage had decreased DMI and ADG compared to cattle fed roughage. Within roughage level, ADG was similar for cattle fed alfalfa hay, corn silage or corn stalks when included on an equal NDF basis. Apparent total tract digestibility of OM, NDF, and CP linearly decreased and ruminal pH variables increased linearly due to increasing roughage levels. Roughage sources can be exchanged on an equal NDF basis in beef finishing diets containing 30% WDGS (DM basis). In finishing diets containing modified distillers grains plus solubles (MDGS), DMI linearly increased due to increasing roughage levels but ADG responded quadratically and was lowest for cattle fed diets without roughage. There was also a quadratic response for DMI and ADG due to WCGF inclusion level. Gain:feed decreased linearly with increasing roughage and WCGF inclusion levels. Feeding 15% WCGF resulted in similar cattle performance and carcass traits to cattle fed no WCGF in diets containing 30% MDGS, but cattle fed diets with 60% total byproduct inclusion made up of 30% WCGF and 30% MDGS had reduced performance (DM basis). Additionally, reducing corn silage inclusion level to 7.5% resulted in similar finishing cattle performance and carcass traits to cattle fed 15% corn silage in diets containing 30% MDGS with or without inclusion of WCGF. Elimination of roughage in diets containing either WDGS or MDGS resulted in negative impacts on finishing cattle performance, ruminal metabolism, and carcass traits.

Strategies for Artificial Insemination of Cattle at Synchronized Ovulation or Synchronized Estrus

Two synchronization protocols in lactating dairy and beef cows and in dairy heifers were tested for efficacy of breeding by artificial insemination (AI) with or without estrus detection. Controls received three prostaglandin F2a (PGF2a) injections 14 days apart before AI at observed estrus. Pregnancy rates were compared with animals on the Ovsynch protocol that combined gonadotropin releasing hormone (GnRH) and PGF2a treatments with a timed AI 16 to 20 hours after the second GnRH injection. The pregnancy rates were similar at synchronized ovulation to fixed-time AI in lactating cows, but not effective in heifers because of the lack of synchronization.

Potential Economic Returns from Selling Beef in a Specified Value-Based Market

Three groups of steers--one theoretical group and two experimental groups—were evaluated for marketing cattle live, as boxed beef, and grade and yield when the live price was $71 to $73/cwt, grade and yield price $125/cwt for Choice yield grade 3 carcasses with $20/cwt discount for Select carcasses, and in a commodity-trim or close-trim boxed beef market. The results show that the value of highyielding steers can be significantly increased if sold in a close-trim boxed beef market. The close-trim premiums ranged from $5.06 per head for Select close-trim yield grade 4 carcasses to $87.18 per head for close-trim Choice yield grade 1 carcasses. A group of experimental steers averaging 82% Choice and 60% yield grades 1 and 2 returned an additional $104 in the close-trim boxed market compared with selling live for $73/cwt. Another group of experimental steers averaging 21% Choice, 18% Standard, and 93% yield grades 1 and 2 had $29 per head greater return than if the steers had been sold live for $71/cwt. These comparisons emphasize the importance of knowing how cattle will potentially grade before selecting an alternative marketing strategy. This prior knowledge is most important when the spread in price between Choice and Select is high. Producers need to learn more about their cattle to predict how the cattle may grade for a specified value-based market.

Use of a Digital Camera to Collect Carcass Data from Experimental Cattle

A digital camera was used to obtain digital images of beef carcasses moving on the rail in commercial beef packing plants. These images were satisfactory for measurement of backfat thickness and area of ribeye. The measurements were closely correlated with the same two measurements taken from tracings on acetate paper of fat thickness and area of ribeye made on carcasses moving on the rail.

Comparison of Various Methods of Estrus Detection in Synchronized Virgin Beef Heifers

Methods of heat detection were compared in the Mid- Crest Area Cattle Evaluation Program (MACEP) heifer development program in the 1998-breeding season. A total of 189 heifers from thirteen consignors entered the program on November 10, 1997. These heifers were condition scored, hip height measured, weighed, disposition scored, booster vaccinated, and treated for parasites at the time of arrival. Determination of the heifer’s mature weight was made and a target of 65% of their mature weight at breeding was established. The ration was designed to meet this goal. The heifers were kept in a dry lot until all heifers were AI bred once. The heifers were periodically weighed and condition scored to monitor their gains and the ration was adjusted as needed. The estrus synchronization program consisted of an oral progesterone analog for 14 days; 17 days after completion of the progesterone analog treatment a single injection of prostaglandin was given and the heifers were then estrus detected. Two concurrent methods of estrus detection were utilized: 1) Ovatec â electronic breeding probe (probe), 2) HeatWatchâ estrus detection system (HW), and 3) a combination of probe and HW. Probe readings were obtained each 12 hours and the heifers were continuously monitored for estrus activity using the HW system. The probe was used as the primary estrus detection method and the HW system was used as a back-up system. Those heifers that did not demonstrate any estrus signs prior to 96 hours post prostaglandin treatment were mass inseminated at 96 hours. Post AI breeding, 151 of the heifers were placed on pasture and ran with clean-up bulls for 60 days. The remaining heifers left the program after the AI breeding was completed. Pregnancy to the AI breeding was determined by ultrasound on June 29, 1998. Results from using both probe and HW were 60% pregnant by AI, probe alone was 32% pregnant by AI, and HW alone was 27% pregnant by AI. The result of mass insemination was 20% pregnant by AI.

Evaluation of a Mixture of Corn Steep Liquor and Distillers Solubles as a Replacement for Corn and Supplement in Cattle Finishing Diets

Finishing yearling steers fed a corn-based diet containing steep liquor had statistically similar live performance as steers fed the control diet. Numerically steers fed the steep containing diet were 6% more efficient. Steers fed steep liquor tended to contain less carcass fat (as measured by intramuscular marbling) less kidney, heart and pelvic fat, and less backfat thickness. When priced at $50/ton adding steep liquor at 10% of diet dry matter reduced feed cost for gain 9%.

Experience with an Electronic Identification System for Cattle

An electronic identification system involving placement of transponders in rumen boluses was evaluated in thirty feedlot steers. All the devices were retained and remained functional in the steers. Twenty-eight of the devices were recovered at the packing plant. Two of them were lost because of an incomplete understanding that attempts were being made to recover the boluses from rumen contents. Use of rumen boluses is a practical alternative for electronic identification of cattle that is permanent and nearly tamper proof.

Value of High-Oil and High-Protein Corn Grains for Finishing Cattle

Three specialty corns, high oil, high protein and high oil with high protein, were compared with control corn in a 113-day steer feeding trial. During the first 63 days of the study, steers fed the corns containing more oil had slower gain and poorer feed conversion compared with the control corn. At the end of the trial there were no statistically significant differences in performance of steers fed the different corns. Steers fed the high protein corn tended to have higher grading carcasses compared with those fed the control corn. Otherwise there were no differences in carcass measurements due to source of corn fed the steers. Feed cost of gain was reduced with the high-protein corn and the corn with high fat and high protein compared with the control corn because of similar feed conversions and the reduced amount of soybean meal needed to supplement the specialty corns.

Brain Regulation of Growth in Beef Calves

Small peptide hormones produced in the lower part of the brain (hypothalamus) regulate episodic and basal secretion of hormones from the anterior pituitary gland that affect metabolism and growth in cattle. This study focused on long-term growth in young calves subjected to hypophysectomy (HYPOX), hypophyseal stalk transection (HST), and sham operation control (SOC). Crossbred (Hereford x Aberdeen Angus) and Hereford, and Aberdeen Angus calves were HYPOX (n = 5), HST (n = 5), or SOC (n = 8) at 146 days of age, whereas another group was HST (n = 5) or SOC (n = 7) at 273 days of age. Body weight was determined every 21 days from birth to 1008 days of age. From day 146-1008, growth was arrested (P < 0.001) in HYPOX (0.06 kg/day) compared with SOC (0.50 kg/day) calves. Growth continued but at a significantly lower rate (P < 0.05) in calves HST at 146 days (0.32 kg/day) and 273 days (0.32 kg/day) compared with SOC (0.50 kg/day). Although episodic growth hormone (GH) secretion was abolished and peripheral blood serum GH concentration remained consistently lower in HST calves (2.4 ng/ml) than in the SOC (5.5 ng/ml; P < 0.01), the calves continued to grow throughout 1008 days. Peripheral serum thyroid stimulating hormone (TSH) concentration was less (P < 0.05) in HST compared with SOC calves. There was an abrupt decrease (P < 0.001) in serum thyroxine (T4) (4-fold) and triiodothyronine (T3) (3-fold) concentration after surgery that remained to 360 days in HST compared with SOC calves. At sacrifice, pituitary gland weight was markedly reduced (P < 0.001) in HST (0.18 g/100 kg body weight) compared with SOC (0.55 g/100 kg body weight) calves. Histological examination of pituitary glands from HST calves indicated the persistence of secretory GH and TSH cells in the same areas of the anterior pituitary gland as SOC calves. Coronal sections of the gland revealed GH and TSH secreting cells in HST calves that were similar to the controls. These results indicate that long-term growth continues, but at a slower rate, after hypophyseal stalk transection of immature calves in spite of complete abolition of episodic GH secretion and consistently decreased basal secretion of GH, TSH, T4, and T3 compared with sham-operated animals. Growth was abolished after hypophysectomy of immature calves in which circulating GH and TSH was undetectable.

Strategies for Optimizing Value of Finished Cattle in Value-Based Marketing Grids

Performance and carcass data from 624 steers in three experiments were used to evaluate potential strategies that might be used with incoming feeders to remove animals that produce low value carcasses when cattle are sold in a valuebased grid. Removing 10% of the carcasses with the lowest net value from each group increased the overall average net value of the remaining carcasses $17.50 to $21.09. Carcass weight was found to be the most significant factor determining net value of the carcass. Gain of the steers during the first 3 to 5 weeks of the feeding period was significantly related to average final gain and carcass value, but accounted for a small portion of the overall variation in gain or carcass value. Use of initial gain was successful in identifying ten of the sixty-four carcasses with least net value in a value-based grid. Adding frame score and measurement of initial thickness of backfat along with initial gain did not significantly improve identification of the low-value carcasses. Sorting the steers as feeders based on frame score and initial thickness of backfat resulted in differences in performance and carcass measurements. The low-value carcasses tended to be concentrated in the smaller-framed steers.

Evaluation of Wet Distillers Grains for Finishing Cattle

A feeding trial was conducted with 870-lb steers fed 137 days to evaluate replacing cracked corn with dry and wet distillers grains with solubles (DGS) as feed for finishing cattle. Dry DGS was evaluated at 16% of diet dry matter. Wet DGS (WDGS) was evaluated at 14.6%, 26.2%, and 37.5% of diet dry matter. Control diets were supplemented with urea or a combination of urea and soybean meal. Feeding 16% dry DGS or 14.6% wet DGS increased rate of gain and tended to increase carcass fatness. Increasing the amount of wet DGS in the diet decreased feed intake, reduced gain, and improved feed conversion. The calculated net energy for gain values for dry and wet DGS were .92 and 1.5 times the energy value of corn grain. Economic returns declined slightly as the percentage of wet DGS increased in the diet, but remained above the two diets without DGS. The average benefits from feeding wet DGS averaged $25, $21, and $19 per head for steers fed 14.6%, 26.2%, and 35.7%, respectively, based on a formula price for wet DGS related to price of corn and including a charge for transportation of the wet feed.