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A feeding trial was designed to examine the effects of copper sulfate pentahydrate (CuSO4.5H2O) on the fatty acid composition and oxidative stability in muscle and adipose tissues of Boer × Spanish goat kids. Fifteen (n = 5 per treatment) goats were fed 0, 100, or 200 mg of supplemental Cu per day as copper sulfate for 98 d. The animals were slaughtered, and LM, s.c. adipose from the sternal region, and mesenteric adipose tissues were collected. Total lipids were extracted with chloroform:methanol (2:1), methylated and isolated via GLC from all tissues. The subsequent peaks were then positively identified by mass spectrometry. Thiobarbituric acid-reactive substances were measured also. In s.c. adipose, dietary Cu significantly decreased C14:0 (P= 0.03) and C16:0 (P= 0.01). In muscle, C15:0 (P= 0.03) was linearly increased by Cu. Dietary Cu supplementation did not influence oxidative stability in goat muscle or s.c. adipose. Copper supplementation at 200 mg/d resulted in a significant increase in malondialdehyde in mesenteric adipose (P= 0.01) compared with the 0 or 100 mg/d groups. These results indicate that lipid composition may differ from depot to depot and that depending on the depot, dietary Cu seems to elicit a variable response on the fatty acid composition.

Experimental techniques employed to measure protein synthesis, degradation and accretion rates in specific tissues or whole animals are discussed. These methods include polysome profiles, initiation/translation assays, in vitro and in situ perfusions, in vitro tissue incubations, in vitro tracer methodology and protein synthesis rate measurement based on single or constant rate tracer administration and whole body protein synthesis based on plasma amino acid flux. Three specific methods are outlined in detail: in vitro incubation of porcine semitendinosus muscle strips, continuous infusion of 14C-tyrosine into pigs and urinary NTmethylhistidine excretion in steers. Laboratory protocols are also provided for sample preparation, specific activity assays, amino acid derivatization for gas chromatography-mass spectrometry and fluorometric measurements of tyrosine and tyramine.

A nutritional evaluation of several winter triticale selections harvested in 1974 and 1975 was made using weanling pigs (9 kg body weight) to determine biological value (BV), net protein value (NPV) and metabolizable energy (ME) of 1974 selections and protein efficiency ratio (PER) of 1975 selections. The usefulness of lysine and threonine supplementation and/or autoclaving of the 1974 selections on BV and NPV was also evaluated. Four 1974 triticale selections were finely ground and basal diets containing about 85% triticale were formed for each selection and adequately complemented nutritionally with the exception of protein quality. Energy balance was conducted on these basal diets and nitrogen balance was conducted on each of the basal diets with or without supplementation with .3% L-lysine plus .2% L-threonine and with or without autoclaving the diet at 121 C at 9.5 kg/cm2for 1 hr in a 4 × 2 × 2 factorial arrangement. Two of the selections (MSU-3, MSU-4) had superior NPV values (P<.01) and selection MSU-4 had a higher ME value than the other selections. Additions of lysine and threonine to the basal diets significantly increased BV and NPV values (P<.05). Autoclaving the diets likewise significantly improved BV and NPV (P<.01). Four 1975 selections were evaluated by incorporating them into basal diets consisting of over 90% triticale with each diet adequately complemented with minerals and vitamins and made to 16% crude protein with wheat gluten. PER values of these diets ranged from .68 to 1.44 compared with 3.26 for a 16% crude protein corn-soybean meal diet.

The effects of tallow supplementation [0% (NT) vs 7.5% (T)] and crude protein level [8.5% (LP) vs 12.0% (HP)] on ruminal fermentation, microbial protein (MCP) synthesis, digesta passage and site of digestion were estimated using yearling Angus × Simmental steers (390 kg) fitted with ruminal and T-type duodenal cannulae. Chromium-EDTA and ytterbium (Yb) chloride were used as markers of the liquid and solid phases. Passage and site of digestion data were estimated from the concentrations of Yb in the duodenal digesta and feces. Dry matter (DM) intakes were 6.8, 6.5, 6.3 and 6.6 kg/d for the NT-LP, NT-HP, T-LP and T-HP diets, respectively. Ruminal ammonia concentrations (mg/100 ml) for the NT-LP, NT-HP, T-LP and T-HP diets were 1.22, 4.75, 1.05 and 3.41, respectively. Tallow decreased (P<.05) acetate (mol/100 mol), increased (P<.01) propionate (mol/100 mol) and decreased the total volatile fatty acid concentration. Tallow depressed apparent ruminal DM and organic matter (OM) digestibilities only on the HP diet. High protein increased ruminal DM, OM and fiber digestibilities. Tallow and LP tended to shift the site of OM digestion to the lower tract. The liquid and solid dilution rates for the NT-LP, NT-HP, T-LP and T-HP diets were 9.53, 3.37; 5.63, 3.28; 6.66, 5.10 and 6.79, 5.34%/h, respectively. Nitrogen (N) intake (g/d), duodenal non-ammonia N flow (g/d), non-degraded N flow (g/d), microbial N flow (g/d) and efficiency of MCP synthesis (g MCP/100 g of OM digested in rumen) for the NT-LP, NT-HP, T-LP and T-HP diets were 101, 130, 77, 53, 10.4; 127, 134, 59, 75, 10.6; 81, 108, 60, 48, 11.3; and 132, 146, 84, 62, 12.0, respectively. A higher percentage of the N intake escaped ruminal degradation on the LP diets. Tallow increased the efficiency of MCP synthesis, but an increase in the solid dilution rate resulted in decreases in microbial synthesis and ruminal OM digestion on T diets.

Effects of photoperiod on growth, carcass composition and serum concentrations of prolactin, growth hormone and Cortisol were determined in prepubertal and postpubertal Holstein heifers. Forty-two prepubertal (avg body wt 84 ± 3.0 kg) and 42 postpubertal (avg body wt 303 ±7.1 kg) Holstein heifers were utilized. Ten prepubertal and 10 postpubertal heifers were slaughtered before treatment began to obtain initial carcass data. The remaining 32 prepubertal and 32 postpubertal heifers were paired by body weight and randomly assigned to short-day (8 h of light: 16 h of dark) or long-day (16 h of light: 8 h of dark) photoperiods. After exposure to treatments for an average of 139 d, 10 prepubertal and 10 postpubertal heifers from each photoperiod treatment were slaughtered. In prepubertal heifers, photoperiod did not affect (P>.10) average daily body weight gain, carcass weight, carcass composition, accretion of carcass fat and carcass protein, or serum concentrations of prolactin, growth hormone or Cortisol. However, prepubertal heifers exposed to long-day photoperiods had reduced (P<.01) urinary N7-methylhistidine excretion compared with heifers given short-day photoperiods. Postpubertal heifers exposed to short-day photoperiods had greater average body weight daily gain than animals exposed to long-day photoperiods. Although there was no effect of photoperiod (P>.10) on carcass or fat depot weights, postpubertal heifers exposed to short days had greater (P=.06) percentages of fat and reduced (P=.07) percentages of protein in the soft tissue of the 9–10–11 rib sections. Fat accretion was greater (P<.05) in carcasses of postpubertal heifers exposed to short days than heifers given long-day photoperiods, but there was no effect (P>.10) of photoperiod on protein accretion. Photoperiod did not affect serum concentrations of growth hormone and Cortisol, but serum prolactin tended (P<.10) to be greater in postpubertal heifers exposed to long days. Under the conditions of this experiment, we conclude that exposure to short-day photoperiods stimulated body weight gain and fat accretion in postpubertal but not prepubertal Holstein heifers.

Experiments were conducted to evaluate the effects of dietary energy density or genetic background on protein and fat gain of growing cattle. In Exp. 1, 24 Limousin steers were used in a growing-finishing trial. A 2 × 2 factorial arrangement was used with steers randomly allotted to four treatment combinations and fed the following diets: 80% concentrate, high moisture corn-corn silage diet (HI) or a corn silage diet (LO) during both the growing (GRO) and(or) the finishing (FIN) phases. Body composition for both experiments was determined by a deuterium oxide dilution technique. Empty body weight gains were greater (P<.05) for HI during GRO, FIN and the total trial. Daily protein gains (DPG) were greater (P<.05) for HI during GRO and FIN, while cattle receiving HI during at least FIN had the greatest (P<.05) overall DPG. Daily fat gains (DFG) followed the pattern of DPG, being more rapid (P<.05) for cattle fed HI during either GRO or FIN. Cattle fed the HI diet also tended to be more energetically efficient. In Exp. 2, large frame (LG) and small frame (SM) cattle were used for the evaluation of frame size effects on protein and fat deposition. Steers were individually fed an 80% concentrate, corn-based diet during the entire trial. Average daily gains and daily dry matter intake (P<.05, P<.01) were greater for LG, while feed efficiency was similar for both cattle types. Large cattle had greater (P<.05) DPG than SM cattle, however, DFG were not different. Small frame steers were energetically more efficient (P<.05), apparently due to composition of gain difference.

Nitrogen metabolism of ruminant animals has been the subject of thousands of research publications. Study of ruminai and intestinal function continues. The quantitative and qualitative importance of ruminai microbes as a source of protein have become apparent in many trials, and factors controlling microbial protein synthesis or growth of microbes as well as ruminai degradation of dietary protein have been explored. Information on the supply side of the protein ledger (ruminai synthesis, bypass or escape of dietary protein; intestinal digestion) exceeds current knowledge of quantitative needs for amino acids. Descriptive models of N metabolism have evolved that amalgamate current concepts. With future amendments, these systems should prove useful in diet formulation to more fully utilize ruminai fermentation and increase productive efficiency of ruminant animals. Expanding knowledge of ruminai N metabolism will permit greater control and manipulation of the processes of ruminai fermentation and postruminal digestion.

Eight steers were used in two 4 × 4 Latin square designed experiments to measure non-ammonia nitrogen (NAN) passage to the abomasum and nitrogen utilization when fed corn silage (CS) or 60% corn-40% corn silage (G) diets (DM basis). All diets were supplemented with soybean meal. Corn silage diets contained 11.25 (CS-11CP) and 12.82 (CS-13CP) % crude protein, and the 60% corn-40% corn silage diets contained 12.85 (G-13CP) and 16.35 (G-16CP) crude protein, respectively. Daily DM intake (% of body weight), daily abomasal N passage (g), daily abomasal NAN passage (g), N passage as percentage of N intake, and NAN passage as percentage of N intake were: 2.1, 63.8, 49.8, 79.2, 70.6; 2.3, 68.5, 53.1, 66.7, 50.9; 2.4, 94.1, 78.6, 88.4, 77.5, 2.6, 98.4, 83.0, 67.8, 57.5, respectively, for diets CS-11CP, CS-13CP, G-13CP, G-16CP. Diets that had lower rumen NH3-N and plasma urea-N levels had a higher net recovery of dietary N in the abomasal digesta flow. The results suggest that the extra protein in G-16CP was not utilized efficiently by the steers.

Two experiments were conducted to evaluate the effects of dietary CP level on rate, efficiency and composition of gain of growing beef bulls. In Exp. 1, 59 bulls (333 ± 15.8 kg) were used. Eleven bulls were slaughtered on d 0 to provide an estimate of initial carcass composition (9-10-11 rib section chemical analyses), and remaining bulls were assigned to treatment diets containing 10, 12 or 14% dietary CP. Bulls fed the 10% CP diet grew slower (P< .05) than bulls fed the 12 or 14% CP diets, although dry matter intake and feed-to-gain ratio did not differ. Bulls fed the 12% CP diet had fatter carcasses (P< .05) than bulls fed the 10 or 14% CP diets and had greater daily fat accretion than bulls fed the 10% CP diet. In Exp. 2, 60 bulls (318 ± 9.0 kg) were used. Bulls were assigned to initial slaughter (n = 6) or to one of three dietary treatments, 10, 12 or 14% CP, and were slaughtered after feeding for 66, 136 or 202 d (n = 6 · treatment−1· slaughter time−1). Bulls fed 10% CP diets had lower (P< .05) rates of carcass protein accretion during d 0 to 136 and d 0 to 202. Carcass fat gain was similar among treatments over the entire experiment, although bulls fed the 14% CP diet gained more fat during d 0 to 136 than bulls fed the other treatments. These data indicate that 10% dietary CP is not adequate to support maximal growth of young bulls and suggest that limiting CP may decrease fatness.

Isolated porcine and bovine muscle strips were incubated in Krebs Ringer bicarbonate buffer to determine in vitro protein synthesis (PS) and protein degradation (PD) rates to validate the in vitro system for use with livestock species. The addition of 5× plasma concentrations of amino acids to the medium stimulated PS 30%. Addition of 3.5 mMleucine to a leucine-deficient buffer supplemented with amino acids decreased PD 37% and stimulated PS 24%. The addition of .1 U/ml insulin reduced PD 28% and increased PS 30%. Protein degradation was elevated in longitudinally split rat soleus and extensor digitorum longus muscles compared to their contralateral intact muscles. Muscle strips must be removed within 15 min of exsanguination because PD rates become greatly elevated thereafter. ATP concentrations declined during incubation, but the addition of ATP or creatine had no effect on either PD or PS. Neither PD nor PS was affected by the addition of transferrin, fetuin, ascorbate, dexamethasone or indomethacin to the incubation medium. However, muscle strips were sensitive to the addition of triiodothyronine (T3); PD was increased up to 75% as T3concentration was increased, and PS rates doubled compared to controls. Serum from mature barrows or gilts had no effect on protein turnover, but the addition of 10% and 15% serum from boars increased both PD and PS. With fasted pigs a continual decline in PS occurred over 5 d, whereas PD was elevated at 3 d and then declined to rates comparable to the fed state after 5 d. These data suggest that the in vitro system has application for assessing relative changes that occur in vivo following nutritional, physiological and endocrinological manipulation.

This report examines the effect of polyunsaturated fatty acids (PUFA) on lipogenic gene expression in cultured 3T3-L1 adipocytes. Arachidonic acid (20:4, n-6) and eicosapentaenoic acid (20:5, n-3) suppressed mRNAs encoding fatty acid synthase (FAS) and S14, but had no effect on beta-actin. Using a clonal adipocyte cell line containing a stably integrated S14CAT fusion gene, oleic acid (18:1, n-9), arachidonic acid (20:4, n-6) and eicosapentaenoic acid (20:5, n-3) inhibited chloramphenicol acetyltransferase (CAT) activity with an ED50 of 800, 50, and 400 microM, respectively. Given the high potency of 20:4, n-6, its effect on adipocyte gene expression was characterized. Arachidonic acid suppressed basal CAT activity, but did not affect glucocorticoid-mediated induction of S14CAT expression. The effect of 20:4, n-6 on S14CAT expression was blocked by an inhibitor of cyclooxygenase implicating involvement of prostanoids. Prostaglandins (PGE2 and PGF2alpha at 10 microM) inhibited CAT activity through a pertussis toxin-sensitive Gi/Go-coupled signalling cascade. Our results suggest that 20:4, n-6 inhibits lipogenic gene expression in 3T3-L1 adipocytes through a prostanoid pathway. This mechanism of control differs from the polyunsaturated fatty acid-mediated suppression of hepatic lipogenic gene expression.