Effects of ractopamine supplementation on growth performance and carcass characteristics of feedlot steers differing in biological type

Effects of ractopamine hydrochloride (RAC) supplementation on growth performance and carcass characteristics of feedlot steers differing in biological type were investigated using British, Continental crossbred, and Brahman crossbred calf-fed steers (n = 420). Steers of each type were weighed at reimplantation [British, mean BW = 375 kg (SD = 38 kg); Continental crossbred, mean BW = 379 kg (SD = 42 kg); Brahman crossbred, mean BW = 340 (SD = 32 kg)] and sorted into 7 BW blocks, each block consisting of 2 pens (10 steers per pen) per type. Pens within a block x type subclass were randomly assigned to RAC treatments (0 or 200 mg x steer(-1) x d(-1) fed during the final 28 d of the finishing period). The type x RAC interaction did not affect (P > 0.05) any of the traits evaluated in this study. Feeding RAC improved (P = 0.001) ADG (1.50 vs. 1.73 +/- 0.09 kg) and G:F (0.145 vs. 0.170 +/- 0.005), but did not affect (P = 0.48) DMI of steers. Dressing percentage, adjusted fat thickness, KPH percentage, and yield grade were not affected by RAC supplementation. Carcasses of steers fed RAC had heavier (P = 0.01) HCW (359 vs. 365 +/- 4.9 kg), larger (P = 0.046) LM areas (81.7 vs. 84.0 +/- 1.1 cm(2)), and tended (P = 0.07) to have lower mean marbling scores (487 vs. 477 +/- 5.2; Slight = 400, Small = 500) than did carcasses of control steers. Among the 3 biological types, Brahman crossbred steers had the lowest DMI and produced the lightest-weight carcasses that had the lowest mean marbling score (P < 0.05). Compared with Continental crossbred and Brahman crossbred steers, British steers produced carcasses with the greatest (P = 0.001) mean marbling scores. Continental crossbred steers had the heaviest BW and greatest dressing percentages and produced the heaviest carcasses with the largest LM areas (P < 0.05) compared with British and Brahman crossbred steers. In the present study, 28 d of supplementation with RAC at a dosage rate of 200 mg x steer(-1) x d(-1) elicited consistent responses in growth performance and carcass traits among 3 diverse biological cattle types.     

Characterization of supply of marine finfish species with potential for commercial growth in the United States

Global production of marine finfish has grown in total volume of production and the number of species farmed commercially, but there has been little production in the United States of marine finfish other than salmon and red drum. For most species considered to be ready for commercialization, there are few or no farms from which to evaluate the size of the market or to estimate revenues and costs necessary to assess economic feasibility. This present study takes a first step to fill this gap with an analysis of the existing supply of 20 marine finfish species identified as candidates for commercialization in the United States, as a proxy for effective demand (the volume of a product sold at the market equilibrium price). Secondary data from 1950 (where available) through 2019 were compiled on each species, including (1) global aquaculture production, (2) US aquaculture production, (3) US commercial landings, (4) US recreational landings, and (5) imports. Current effective market demand (measured as the sum of commercial landings, farmed production, and imports) was low, totaling 36.6 million kg across the 20 species, which is equivalent to less than 23% of the annual volume sold of US farmed catfish. Commercial landings for 17 of the 20 species exhibited declines, potentially offering opportunities for farmed product to capture market share by filling the increasing gaps in supply. The variability in commercial landings provides opportunities for farms to capitalize on their advantage in supplying product with a high degree of consistency of volume, size, delivery frequency, and quality. Several unknown factors suggest the need for follow-up studies on consumer preferences, degree of substitutability among finfish species, and effects of recreational landings on demand. An important limitation to prospective producers is the lack of species-specific import data for the generic categories of “flounder,” “bass,” and “snapper.” This supply analysis provides a foundational analysis for prospective producers, investors, and researchers interested in commercialization of these marine species.     

Evaluation of a Confinement System for Growout of Channel Catfish Ictalurus punctatus

Rising costs of inputs have created a need to improve catfish production efficiencies. An inexpensive confinement system was evaluated for channel catfish Ictalurus punctatus foodfish production. Barriers were constructed in five 0.1-ha earthen ponds to partition ponds into 1/3 and 2/3 sections. Large fingerling (136 g) catfish were stocked at 11,115 fish/ha in the smaller 1/3 section (shallow end) of the confinement ponds or in open ponds (control). Seining efficiency was significantly greater for the confinement system. Yield and daily growth of food fish were significantly lower and feed conversion ratio higher in the confinement system compared to open ponds. Partial budget analysis showed a net loss of –$313/ha. Additional work is needed to develop inexpensive production systems to capture efficiencies of confinement without decreasing production.     

Development of aquaculture financial planning system

Abstract

Economically efficient feeding levels in intensively stocked ponds might be below minimum biological feeding requirements under adverse market conditions. A catfish production function that estimated relationships between yield and stocking and feeding rates was used as the basis for estimating production relationships. Feed price boundaries were developed that allowed the feeding rate to exceed the minimum biological level but still reflected economically efficient rates over a range of catfish prices and producer risk preferences. At higher stocking densities (20,000/ha), the feed price upper bound is lower than at lower stocking densities. Producers stocking at higher rates will be less likely to maximize profit and meet minimum biological feeding requirements as feed price increases than those producers stocking at lower rates. However, if feed prices exceed the upper bounds calculated in this paper, producers should engage in feeding only at levels necessary to meet farm financial and cash flow obligations until such time as the feed price decreases.     

Trace mineral source impacts rumen trace mineral metabolism and fiber digestion in steers fed a medium-quality grass hay diet

Twelve Angus steers (BW 452.8 ± 6.1 kg) fitted with ruminal cannulae were used to determine the impact of trace mineral (TM) source on digestibility, ruminal volatile fatty acid (VFA) composition, ruminal soluble concentrations of Cu, Zn, and Mn, and relative binding strength of trace minerals located in the rumen insoluble digesta fraction. Steers were fed a medium-quality grass hay diet (DM basis: 10.8% CP, 63.1% neutral detergent fiber [NDF], 6.9 mg Cu/kg, 65.5 mg Mn/kg, and 39.4 mg Zn/kg) supplemented with protein for 21 d. Treatments consisted of either sulfate (STM) or hydroxy (HTM) sources (n = 6 steers/treatment) to provide 20, 40, and 60 mg supplemental Cu, Mn, and Zn/kg DM, respectively. Following a 21-d adaptation period, total fecal output was collected for 5 d. Dry matter (P < 0.07) and CP (P < 0.06) digestibility tended to be reduced, and NDF (P < 0.04) and acid detergent fiber (ADF) (P < 0.05) digestibility were reduced in STM- vs. HTM-supplemented steers. On day 6, ruminal fluid was collected at 0, 2, and 4 h post-feeding and analyzed for VFA. There were no treatment x time interactions for VFA. Steers receiving HTM had less (P < 0.02) molar proportions of butyric acid and greater (P < 0.05) total VFA concentrations than STM-supplemented steers. Steers were then fed the same diet without supplemental Cu, Zn, or Mn for 14 d. On day 15 steers received a pulse dose of 20 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either STM or HTM (n = 6 steers/treatment). Ruminal samples were obtained at 2-h intervals starting at −4 and ending at 24 h relative to dosing. There was a treatment x time interaction (P < 0.03) for ruminal soluble Cu, Mn, and Zn concentrations. Ruminal soluble mineral concentrations were greater (P < 0.05) for Cu at 4, 6, 8, 10, 12, and 14 h; for Mn at 4 and 6 h; and for Zn at 4, 6, and 8 h post-dosing in STM compared with HTM-supplemented steers. Copper concentrations were greater (P < 0.05) at 12 and 24 h and Zn concentrations in ruminal solid digesta were greater at 24 h in HTM-supplemented steers. Upon dialysis against Tris-EDTA, the percent Zn released from digesta was greater (P < 0.05) at 12 h (P < 0.03) and 24 h (P < 0.05), and the percent Cu released was greater (P < 0.02) at 24 h post-dosing in HTM steers when compared with STM-supplemented steers. Results indicate that Cu and Zn from HTM have low solubility in the rumen and appear to be less tightly bound to ruminal solid digesta than Cu and Zn from STM. The lower ruminal soluble concentrations of Cu and Zn in steers given HTM were associated with greater fiber digestibility.     

The Costs of Regulations on US Baitfish and Sportfish Producers

The US regulatory environment has been characterized as complex due to the greater than 1300 laws promulgated at local, state, and federal levels. Recent declines in the growth rate of US aquaculture have been attributed, in part, to a complex, overlapping, and inefficient regulatory framework. This study is the first to examine this question by quantifying the farm‐level regulatory burden and its economic effects in an aquaculture industry sector. A survey was conducted of baitfish and sportfish producers in the 13 major production states in the USA to identify the direct and indirect costs of regulation on producers. Survey responses captured 74% of the national volume of baitfish and sportfish production. The data revealed that only 1% of total regulatory costs are direct costs of regulation, such as license and permit fees, while 99% of the costs are due to manpower used for compliance, farm changes to remain in compliance, and sales lost without replacement. Costs due to regulations varied across states and farm sizes. Across all respondents, average total regulatory costs were found to be $148,554/farm, or $7383/ha. The farm‐level cost to the US baitfish and sportfish industry was estimated to be in excess of $12 million. On 38% of the farms, the cost of regulations exceeded the value of profits on baitfish and sportfish farms. Our findings confirm previous reports of the complexity of the regulatory environment. Results show that the total regulatory burden has increased farm‐level costs and restricted access to markets, thereby reducing profitability and contributing to reduced growth of the US baitfish and sportfish industry.     

玉米大斑病菌对广州地区甜玉米的致病性观测

通过对桂甜和华珍两个甜玉米品种的玉米大斑病病斑扩展速率及病情指数的研究结果表明,不同品种对玉米大斑病菌的抗性存在明显的差异;病斑的产孢特性显示,病斑首次产孢量显著高于再次产孢量。通过比较不同温度下的菌丝生长量,分析出广州地区玉米大斑病菌的主要构成属于高温型。     

虫生真菌在准格尔旗沙棘木蠹蛾上的流行

为了了解沙棘木蠹蛾Holcocerus hippophaecolus幼虫的虫生真菌的物种多样性和流行情况,对内蒙古准格尔旗某沙棘林中的虫生真菌进行了调查,采集到11个虫生真菌标本。经实验室显微观察鉴定,其中1个为雷州被毛孢Hirsutella leizhouensis侵染,1个为一种被毛孢Hirsutella sp.侵染,9个为球孢白僵菌Beauveria bassiana侵染;分离纯化得到7株球孢白僵菌菌株。     

浅析伊图里河林业局森林资源消长趋势

文章通过对伊图里河林业局1994年、2005年两次二类调查数据的分析,详细阐述了森林资源消长变化总趋势,在此基础上对伊图里河林业局森林资源现状及其特点进行了分析,提出了对森林资源管理利用的建议。     

Effect of fish meal supplementation on plasma and endometrial fatty acid composition in nonlactating beef cows

Seven nonlactating mature Angus cows (4 to 10 yr old) were used to examine the effects of fish meal supplementation on plasma and endometrial fatty acid composition. Cows were fed a corn silage-based diet supplemented with either fish meal, a rich source of the n-3 fatty acids, eicosapentaenoate and docosahexaenoate (n = 3; 5.1% of dietary DM), or corn gluten meal (n = 4; 8.5% of dietary DM) for approximately 64 d. Cows were given 25 mg of PGF2alpha (i.m.) on d 11 and 25 of supplementation to synchronize estrous cycles. On d 18 postestrus of the second estrous cycle, cows were slaughtered, and caruncular endometrium was dissected from uteri immediately after slaughter. Jugular blood samples were collected immediately before supplementation was initiated (d 0) and at 7-d intervals for 35 d of the study. Plasma eicosapentaenoic and docosahexaenoic acids did not differ between treatment groups on d 0 (P > 0.10); however, these fatty acids were greater in cows supplemented with fish meal over the first 35 d of supplementation compared with cows supplemented with corn gluten meal (P < 0.05). Endometrial docosahexaenoic acid did not differ (P = 0.12), whereas eicosapentaenoic acid was greater (P < 0.05) in cows supplemented with fish meal than in cows supplemented with corn gluten meal. These results indicate that dietary fish meal alters plasma and endometrial n-3 fatty acid composition in beef cows.