Conjugated linoleic acid content of beef differs by feeding regime and muscle.

The project objective was to determine the CLA content of three muscles (Longissimus lumborum, LD; Semimembranosus, SM; Triceps brachii, TB), in both raw and cooked states, in cattle finished on pasture or with grain supplements. Cattle were randomly assigned to one of four finishing regimens; pasture (n=11), pasture with grain supplement (n=11), pasture with grain supplement containing soyoil (n=12), and feedlot (n=12). In the raw state, TB had higher (P<0.05) CLA than LD or SM on a mg/g sample basis. Total CLA was higher (P<0.05) in the soyoil diet when compared to the other three feeding regimes on a mg/g sample basis and when expressed as mg/g fat in both raw and cooked analyses. Pasture inclusion produced higher levels (P<0.05) of total CLA than the feedlot diet on a mg/g fat basis for cooked samples while maintaining acceptable eating quality.

Effect of particle size upon digestible cell wall and rate of in vitro digestion of alfalfa and orchard grass forages.

Alfalfa and orchardgrass forages chopped through a 13-mm screen were larger in particle size than were rumen ingesta samples from sheep fed the same forages. Samples of the chopped forages were ground through 1-, 4-, 8-, and 12-mm screens; particle sizes of the 8- and 12-mm ground forages were not significantly different from those of rumen ingesta samples or chopped forages. The 1- and 4-mm ground forages were significantly smaller in particle size than the 8- and 12-mm ground forages, rumen ingesta and chopped forage. Alfalfa contained less cell wall at the beginning of in vivo digestion, more cell wall residue at the end of digestion and less potentially digestible cell wall than did orchardgrass. The cell wall of alfalfa was 44% digestible, whereas that of orchardgrass was 61% digestible; particle size did not affect the amount of digestible fiber. Alfalfa ground through 1- and 4-mm screen openings had digestion rate constants that were about twice those of the 8- and 12-mm granulations (.10 less than P less than .20). Particle size did not affect rate constants of orchardgrass. These data suggest that in vitro kinetic studies based on examination of finely ground forages (1) may not reflect in vivo conditions, and (2) may depend upon the type of forage. Differences between legumes and grasses in (1) amount of digestible fiber and (2) digestion rate constants and the interaction of the above two factors with particle size and passage rate have important implications for digestibility of forage fiber.

Intake, digestibility, ruminal characteristics and rate of passage of orchardgrass diets fed to sheep.

Four orchardgrass diets ranging in cell wall content from 60 to 78% were fed to sheep, and relationships among intake, digestion, passage and ruminal measurements were determined. As cell wall concentration increased, dry matter intake, digestible energy intake, dry matter digestibility and excretion rate decreased, while cell wall intake rumen volume, rumen cell wall and retention time increased. Indigestible cell wall intake was similar with each diet. It appeared that as digestible energy intake decreased, the sheep attempted to adapt by increasing ruminal ingesta volume, increasing ruminal ingesta cell wall and decreasing rate of passage; as cell wall concentration increased, indigestible cell wall limitation was manifested in decreased levels of feed and energy intake. Rate and extent of digestion appeared to be related to indigestible cell wall and appeared to be key factors in the control of cell wall turnover and feed intake.

Effects of protein and energy supplementation of Guernsey cows on the kinetics of digestion and passage of orchardgrass versus alfalfa.

Four mature, nonlactating Guernsey cows were used in a 4 x 4 latin square experiment to determine nutrient digestibility, rate of particulate passage, ruminal volume and composition of ruminal contents in cows fed diets at 80% of ad libitum intake. Diets consisted of 100% alfalfa (AL), 100% orchardgrass (OG), 85% OG plus 15% soybean meal (OG + SBM) and 70% OG plus 20% SBM plus 10% starch (OG + SBM + S) on an as-fed basis. Particulate passage rates were measured by either meal marking (Ce) or ruminal marking (La). Intake (1.6 vs 1.4% of BW) and digestibility of DM (63 vs 56%) and NDF (66 vs 39%) were greater (P less than .05) for OG than for AL. Dry matter and CP digestibility were improved 6 and 16 percentage units, respectively, when OG was supplemented with SBM + S. Nitrogen retention, higher (19 vs 3 g/d; P less than .02) in animals fed OG than in those fed AL, was reduced (P less than .05) when OG was supplemented with SBM (5 g/d), but it was improved (P less than .05) when OG + SBM was supplemented with S (39 g/d). Particulate passage (-k) measured with Ce (3.8 vs 4.6%/h) and La (4.2 vs 4.9%/h) was slower (P less than .01 and P less than .10) for AL vs OG, respectively. Supplementation of OG with SBM increased (P less than .01) -k and reduced (P less than .01) ruminal t1/2 and total t1/2. Averaged across diets, total (32.3 vs 31.1 h) and ruminal t1/2 (15.1 vs 14.0 h) of Ce were slower (P less than .10) than La. Marking techniques were not different (P greater than .05) in sensitivity for passage characteristics. Total ruminal NDF content was not different (P greater than .05) for AL vs OG (10 vs 9 g/kg BW), but it was lower for OG + SBM and OG + SBM + S (7.8 and 7.9 g/kg BW; P less than .05). Supplementation of OG with protein and starch increased total diet intake but did not decrease extent of NDF and ADF digestion.

Image texture features as indicators of beef tenderness.

Image processing techniques were developed to predict cooked-beef tenderness from fresh-beef image characteristics. Cattle from different finishing treatments were processed in a commercial plant. Two short loin steaks were sampled from each carcass; one used for sensory evaluation and the other for imaging. The samples varied significantly in both US quality grades and sensory tenderness scores. Color, marbling and texture features were extracted from the beef images. Statistical and neural network analyses were performed to relate the image features to sensory tenderness scores. Image texture features were found to be useful indicators of beef tenderness. Partial least squares and neural network models were able to predict beef tenderness from color, marbling and image texture features to R(2)-values up to 0.70.

Role of particle size and forage quality in digestion and passage by cattle and sheep.

Diminution of forage particles includes mastication, chewing, and digestion. In rumen of cattle and sheep fed all forage diets, particle size can range from 200 to over 1200 microns. Particle size reduction to about less than 1200 microns must occur before passage. Dietary particle size may influence rumen particle size, but mastication and rumination minimizes differences among diets. Ruminants expend considerable effort to move digesta. Density, cell wall percentage, osmotic pressure, and pH may affect propulsion. Dense particles may sink to the bottom and resist escape. Cell wall may reduce digestion and passage. Osmotic pressure or pH may affect digestive efficiency and rhythm of intestinal tract muscles. Chewing, exercise, physiological functions, and body size may also affect the reduction of forage particle size. More effort is necessary to chew high than low fiber diets. Young cattle (less than 225 kg) lack rumination capability and body size to process forage particles efficiently. Exercised sheep (26,400 kg-m/d) ate less forage and ruminated less than controls. Other body functions, such as lactation, appear to influence chewing patterns and rumination. These relationships are poorly understood at best and need additional intensive examination.

Nutrient content, dry matter yield, and species composition of cool-season pasture with management-intensive grazing.

The objective of this study was to determine changes in the nutrient content, available pasture, and species stand counts of cool season pastures during the grazing season. Four replicated pastures were flexibly subdivided into 18 to 36 paddocks and grazed rotationally from late April to November in each of 2 yr. Steers were grazed with fresh pasture offered each 1 to 2 d, which resulted in rest periods for paddocks of 17 to 35 d. Samples used to determine the nutrient content of pasture forage dry matter (DM) were collected from two grazing rumen-fistulated heifers that had empty, clean rumens at initiation of the sampling period. Mean stand counts in long-term established pastures for the grazing season were 24% legumes, 45% grasses, 8% grassy weeds, 10% bare ground, 11% broadleaf weeds, and 1% dung piles. Stand counts did not differ between years. Mean DM utilization of pasture per grazing cycle was 1103 kg/ha, and total DM temporal utilization per season was 6624 kg/ha, which was 35% of the pasture available for each grazing. Pasture content of neutral detergent fiber, crude protein, in situ digestible DM, and net energy for lactation did not differ between years but did differ among months of harvest: neutral detergent fiber decreased, crude protein and in situ digestible DM increased, and acid detergent fiber and estimated net energy for lactation remained relatively constant over the grazing season. The content of measured nutrients in ingested herbage did not differ among heifers sampled. These results indicate that individual cattle select similar quality diets from given pastures and nutrient differences occurred among months of sampling. Even though differences among months of season were statistically different, actual differences were small. Management-intensive grazing of pastures was uniform enough over season, and animal selectivity was strong enough over season to result in constant quality of consumed pasture.

Paper and whey as a feedstuff for ruminants.

Eleven papers were compared for absorption of whey and for digestibility in vitro. Papers were squared, ground, and soaked in whey for 1, 5, and 15 min and for 1, 6, 24, 48, and 72 h. Digestibility in vitro was determined on minimum and maximum whey absorption of each squared and ground paper sample. Whey absorption by squared papers increased with time. Ground samples absorbed more whey than squared ones and maximum quantities were absorbed with 1 to 5 min. Mean percent absorptions for ground telephone book covers, glossy magazines, computer cards, computer printout sheets, daily newsprint, telephone directory yellow pages, cardboard box, feedsacks, brown bags, telephone directory white pages, and coasters were: 31.0, 35.2, 35.4, 36.5, 43.9, 47.9, 51.0, 51.4, 51.7, 55.6, and 67.4. For seven papers, addition of whey increased digestibility. Four papers were either unchanged or decreased in digestibility. This depression of digestibility may have resulted from the high fat content of whey used. Based on in vitro digestibilities, we conclude that it is possible to recycle selected paper/whey combinations through ruminants.

Effects of variety and particle size upon utilization of fescue hay by lactating dairy cows and dairy heifers.

Missouri-96 and Kentucky-31 hays were chopped with a tub grinder containing screens with apertures of 31, 63, or 100 mm in diameter and fed to dairy cows or heifers. Particle sizes (geometric mean diameter) were 1218, 1486, and 1933 micron, respectively, for the 31, 63, and 100-mm treatments. In Trial 1, the six treatments were fed ad libitum to 24 lactating cows; concentrate was offered at 1 kg/2 kg of milk. Dry matter intake and NDF digestibility were greater for Kentucky-31, but there were no other effects of variety. Particle size did not affect DM intake, DM or fiber digestibility, nitrogen partition, milk yield, or milk fat percentage. Crude protein digestibility was greatest for the 63-mm particle size treatment. In trial 2, the six treatments were fed ad libitum to 24 dairy heifers. Intake was greater for the 31 than for the 100-mm treatment but was unaffected by variety. Variety and particle size did not affect DM digestibility, nitrogen utilization, or daily gain. In this study fescue hay chopped through screens having apertures ranging from 31 to 100 mm was without effect on milk yield or composition. Reducing particle size increased intake and nitrogen utilization but not DM or fiber digestibility.

Effect of particle size of alfalfa hay on intake, digestibility, milk yield, and ruminal cell wall of dairy cattle.

Alfalfa hay was chopped in a tubgrinder containing screens with apertures of 31, 63, or 100 mm. The hays were fed with concentrate to lactating cows (Experiment 1) and without concentrate to nonlactating, fistulated cows (Experiment 2). The objective was to find effects of forage particle size upon intake, digestibility, milk yield, and ruminal cell wall. In Experiment 1, there were no significant effects of forage particle size upon forage or total DM intake, digestibility of NDF, cellulose, nitrogen retained, milk yield, or milk fat percent. Digestibility of DM, ADF, and protein increased as particle size decreased. In Experiment 2, forage DM intake was greater for the 63 than the 100-mm forage but digestibility of cell wall and DM were not different among treatments. Ruminal volume for the 31 and 63-mm forages was greater than the 100-mm forage. Ruminal DM and ruminal cell wall were greater for the 63-mm forage than the 100-mm forage, with the 31-mm forage in between. Increased volume, DM, and cell wall probably account for increased intake of the 63-mm forage. Chopping alfalfa to these three sizes had no particularly positive or negative effects on animal productivity.

Relationship of dietary selenium to selenium in plasma and milk from dairy cows.

In a 13-wk trial Holstein cows in mid-lactation were fed four diets containing natural selenium alone or supplemented with .1, .2, or .5 mg of inorganic selenium per kilogram of diet. Dietary selenium concentration averaged .334, .385, .456, and .772 mg/kg. Selenium plasma in wk 7 averaged .112 mu/ml with no differences among treatments; milk selenium ranged from .040 to .046 mu/ml and was higher in the two higher selenium diets. In wk 13 selenium in plasma and milk averaged .119 and .054 with no treatment differences. The 7 and 13 wk concentrations were higher than pretrial .084 and .033 mu/ml for plasma and milk during which time dietary selenium concentration was .254 mg/kg. Selenium concentration increased linearly from about .08 to .120 mu/ml of plasma and about .030 to .055 mu/ml of milk as intake of selenium increased from about 2 to 6 mg/day. Increase in selenium intake from 6 to 12 mg/day resulted in little change in plasma and milk selenium. Moderate concentrations of dietary selenium (.3 to .7 mg/kg) do not result in toxic amounts of selenium in milk.

True absorption of calcium and phosphorus from corn silage fed to nonlactating, pregnant dairy cows.

A crossover design was implemented using four nonlactating dairy cows [mean body weight (BW) = 678 kg] and two rations to measure the true absorption of Ca and P from corn silage. True absorption was calculated after dosing cows intravenously with 45Ca and 32P to measure endogenous fecal losses. Rations consisted mainly of corn silage and were formulated to supply 32 g/d of Ca and 20 g/d of P or 16 g/d of Ca and 12 g/d of P. The percentages of total Ca and P that came from corn silage were 95 and 77%, respectively, for ration 1, and 98 and 79%, respectively, for ration 2. Cows ate more dry matter (10.9 vs. 10.2 kg/d) when consuming the corn silage in ration 1 than when consuming the corn silage in ration 2. Calcium intake was greater for cows fed ration 1 than for cows fed ration 2 (32.6 vs. 16.1 g/d), and P intake was greater for cows fed ration 1 than for cows fed ration 2 (20.1 vs. 11.7 g/d). True absorption of Ca was 34.4 and 43.7% for rations 1 and 2, respectively, and true absorption of P was 84.5 and 93.9% for rations 1 and 2, respectively. True absorption of Ca was about equal to values currently used in the National Research Council (NRC) feeding standards, but true absorption of P was higher than values currently used by the NRC. Fecal endogenous excretion of Ca (mean = 8.23 mg/kg of BW per d) was one-half of the value currently used by the NRC, and fecal endogenous excretion of P (mean = 7.23 mg/kg of BW per d) was only slightly less than NRC values.

Growth and nutrient digestion by dairy heifers fed semipurified diets.

Holstein heifers, which weighed an average of 154 kg, were randomly assigned to three dietary treatments in a split plot in time design. Differences in diets were fiber source: solka floc, corn cobs, and corn silage. The major source of added protein was corn gluten meal. Total collection metabolism periods were the final 7 d of each of two 30-d periods. Several heifers had simple digestive disturbances, which appeared to be related to low ruminal pH, while consuming the solka floc diet. Average daily gains were .78, .83, and 1.02 kg/d for treatments solka floc, corn cobs, and corn silage, respectively. Gains were within the range of acceptable growth standards and were higher than reports in the literature for semipurified and purified diets. Protein in corn gluten meal appeared to be utilized efficiently by the heifers for growth. The solka floc and corn cob diets are acceptable for growing dairy heifers where a low mineral content is desired but normal growth rates need to be maintained. The solka floc diet might be improved by including a buffer to help stabilize rumen pH.