The objective of this research is to evaluate liver mitochondrial oxygen consumption and proton leak kinetics in progeny from two lineages of Angus bulls with high and low residual feed intake (RFI). Two Angus bulls were selected based on results from a genetic test for RFI and were used as sires. Eight offspring at 10-11 months of age from each sire were housed in individual pens for 70–105 days following a diet adaptation period of 14 days. Progeny of the low RFI sire had 0.57 kg/d (P = 0.05) lower average RFI than progeny of the high RFI sire. There was no difference in dry matter intake between low and high RFI steers, but low RFI steers gained more body weight (P = 0.02) and tended to have higher average daily gains (P = 0.07). State 3 and State 4 respiration, RCR, and proton leak did not differ between high and low RFI steers (P = 0.96, P = 0.81, P = 0.93, and P = 0.88, resp.). Therefore, the increase in bodyweight gain which distinguished the low RFI steers from the high RFI steers may be associated with other metabolic mechanisms that are not associated with liver mitochondrial respiration and proton leak kinetics.

No abstract

In October 2011, a mail and online survey of California dairy personnel was conducted to assess producer familiarity with and support of the Dairy Animal Care and Quality Assurance (DACQA) program. The DACQA program addresses cattle of all ages (birth to culling) and standard practices that affect the use of dairy cattle for beef. The survey was mailed to a random sample of 1,071 California dairies (65%) stratified by county, proportional to the number of dairies in each respective county. Data from the 158 responses received (15%) showed that 90% of culled cows on California dairies were sold for beef. However, personnel on more than one-half of California dairies (56%) had no knowledge of how their herd cull cows ranked in terms of beef quality measures (body condition score, US Department of Agriculture carcass grade, and hot carcass weight). Survey results showed that a considerable proportion of California dairy personnel were aware of recommended injection practices including a preference for subcutaneous injections (45%). A drug inventory was maintained on approximately 50% of the state's dairies. Management at these dairies was twice as likely to test for drug residues compared with dairies that did not maintain a drug inventory. More information about the DACQA program was requested by more than half of California dairies.

Mitochondrial respiration was assessed in sixteen 7-day-old broilers as a subset of a larger study assessing the effects of Cu and Zn supplementation above requirements with a coccidiosis challenge on gain/feed ratio. The birds were selected from four treatments (four birds/treatment): a control diet (Cu 15 mg/kg and Zn 60 mg/kg) + coccidiosis challenge (CC), a Cu diet with 245 mg/kg Cu from tribasic copper chloride (TBCC) + CC, a negative control diet (Cu 15 mg/kg and Zn 60 mg/kg) - CC and a Zn diet with 2000 mg/kg Zn from ZnO. The diets were composed of 49% corn, 40% soybean meal, 6.2% vegetable oil (diet dry matter = 90.62%, crude protein = 21.37%, fat = 7.7%, metabolizable energy = 12.1 MJ/day) and were fed for 14 days. Birds were dissected, and approximately one gram of liver tissue was used for mitochondrial oxygen consumption and proton leak kinetics assays. Respiratory control ratio and mitochondrial proton leak assessed by calculating rates of oxygen consumption at 175mV membrane potential were greater for the negative control group, but there were no differences in average gain/feed among treatments. In summary, broilers that did not undergo coccidiosis challenge had lower proton leak and higher respiratory control ratio. However, the impact of supplementation of Cu and Zn above requirements did not appear to prevent changes in respiratory control ratio and proton leak kinetics with coccidiosis challenge.

<p>Fatty acid profiles of backfat (BF), intermuscular fat (IMF), kidney pelvic heart (KPH) fat and tail fat (TF) depots from 15-mo old Angus cross steers finished on grass (GS; n = 18) were compared to those finished on a grain diet (GN ; n = 14) to examine how diet and fat depot impacts fatty acid composition. GS steers grazed an average of 10 months (mo) on ryegrass and white clover irrigated pasture and GN finished steers were a corn based finishing diet for 4 mo. Overall, fat from GS steers contained higher percentages of C6:0 (P = 0.008), C12:0 (P = 0.003), C14:0 (P = 0.001), C16:0 (P = 0.002), C18:3 (P = 0.008), C20:0 (P &lt; 0.001), C18:1 trans9 (P = 0.004), C18:2 cis9 cis12 (P &lt; 0.001) and C18:2 trans9 trans12 (P &lt; 0.001) than GN steers. Fat from GN steers contained higher percentages of C18:0 (P &lt; 0.001). For both GS and GN steers, C18:0 content was higher in the KPH and IMF compared to BF and TF (P = 0.015) depots and C18:1 cis9 content was lower in KPH compared to BF and TF depots (P &lt; 0.001). Therefore, fatty acid composition differs due to diet and differs across depots. Manipulating diets and source of fat (depot) could be used as strategies to modify the fatty acid composition of meat products to increase health benefits to consumers.</p>