Influence of myosin heavy chain isoform expression and postmortem metabolism on the ATPase activity of muscle fibers

The objective of this study was to determine the effects of postmortem muscle pH and temperature declines on the actomyosin ATPase activity of muscle fibers expressing different MyHC isoforms. Using a quantitative histochemical procedure to determine ATPase activity, the maximum actomyosin ATPase activity was determined on individual fibers classified by MyHC expression. Samples were collected from the red (RST) and white (WST) semitendinosus muscles at 3 min and 24 h postmortem from electrically stimulated (ES) and control (NS) pork carcasses. In samples taken at 3 min postmortem, type I fibers had the lowest ATPase activity staining and type 2X and 2B had the highest activity staining, with type 2A fibers intermediate. Postmortem time and carcass treatment did not influence the ATPase activity staining of type I muscle fibers. ATPase activity staining of 2A fibers was lower (p<0.001) in 24 h samples than in 3 min samples from ES carcasses. In 3 min and NS-24 h samples, RST type 2A fibers had lower (p<0.05) activities than type 2A fibers from the WST. In type 2X fibers, ATPase activity staining decreased (p<0.01) from 3 min to 24 h postmortem in ES carcasses. This decrease was more severe in WST 2X fibers compared to RST 2X fibers. ATPase activity staining in type 2B fibers did not decrease from 3 min to 24 h postmortem in NS carcasses. In ES carcasses, activity staining of 2B fibers decreased (p<0.0001) with time postmortem. The results of the experiment indicate that fibers expressing fast MyHC isoforms have a higher ATPase activity early postmortem than slow muscle fibers but are more prone to inactivation by a rapid pH decline.     

Influence of myosin heavy- and light chain isoforms on early postmortem glycolytic rate and pork quality

This study addressed the influence of the content of myosin heavy- (MHC) and light chain (MLC) isoforms on early postmortem glycolytic rate and meat quality traits in the porcine longissimus muscle. The fast-glycolysing group showed lower contents of MHC slow and MLC 1s isoforms (P<0.05), and higher MHC fast isoform contents than the normal-glycolysing group (P<0.05). The MHC fast/slow ratio was correlated with lactate content (r=0.41) and early postmortem muscle pH (r=-0.51), and the content of the MLC 1s isoform was negatively correlated with lactate content and glycolytic potential (r=-0.38 and -0.36, respectively). Hence, both the MHC and MLC isoforms did influence metabolite contents, thus also affecting glycolytic rate, and suggested that the myosin isoforms, in particular the MHC isoforms, might also have some bearing on the extent of protein denaturation and pork quality during the early postmortem period.     

Feeding feedlot steers fish oil alters the fatty acid composition of adipose and muscle tissue

Sixteen steers (441±31.7kg initial body weight) consumed two high concentrate diets with either 0 or 3% fish oil to determine the impact of fish oil, an omega-3 fatty acid source, on the fatty acid composition of beef carcasses. Collected tissue samples included the Longissimus thoracis from the 6th to 7th rib section, ground 10th to 12th rib, liver, subcutaneous adipose tissue adjacent to the 12th rib, intramuscular adipose tissue in the 6th to 7th rib sections, perirenal adipose tissue, and brisket adipose tissue. Including fish oil in the diet increased most of the saturated fatty acids (P<0.01) and proportions of polyunsaturated fatty acids (P<0.06), and decreased (P<0.01) proportions of monounsaturated fatty acids. Dietary fish oil increased (P<0.01) levels of omega-3 fatty acids in sampled tissues, resulting in lower (P<0.01) omega-6:omega-3 ratios. The weight percentages of C20:5 and C22:6 in tissue may provide the recommended daily allowance for humans. Fish oil may have a role in beef niche marketing if there are no deleterious effects on consumer satisfaction.     

Effects of feeding strategies including different proportion of pasture and concentrate, on carcass and meat quality traits in Uruguayan steers

Eighty four steers were randomly assigned to three pasture treatments with increasing levels of grain (T1: 0%; T2: 0.6%; T3: 1.2% of live weight) and to an ad libitum concentrate treatment, T4, to study the effects on carcass and meat quality. Animals were slaughtered with 500 kg of average live weight per treatment. Average daily gain increased with increasing levels of energy, determining different slaughter dates. Intermediate treatments showed higher carcass weight than T1. T4 and T3 had a higher weight of valuable cuts than T1 and T4. Pistolas from T4 had a higher fat proportion and lower bone percentage. Increasing levels of energy in diet decreased fat yellowness. After 20 days of aging, T4 had the lowest muscle a^∗ values and shear force was higher for T4 than for T1. With pastures finishing strategy, no adverse effects on meat quality were detected and tenderness was enhanced.     

Effect of season on contractile and metabolic properties of desert camel muscle (Camelus dromedarius)

Thirty fattened one humped desert camels were used to examine the effect of season on contractile and metabolic properties of Longissimus thoracis (LT) muscle. Ten camels were slaughtered according to seasons of the year (winter, summer and autumn). Season significantly influenced muscle chemical composition, ultimate pH (pHu) and color. Activities of metabolic enzymes were higher during autumn season compared to summer and winter for phosphofructokinase (+ 64% compared to both seasons) and for isocitrate dehydrogenase (+ 35% and + 145% in autumn vs. summer and winter, respectively). Quantification of muscle myosin heavy chain isoforms by SDS-PAGE electrophoresis showed only presence of type I and type IIa MyHC in camel muscle and indicated high proportion in winter for type I and in autumn for type IIa with respect to other seasons. Several correlations between different MyHC proportions and enzyme activities were reported. These findings indicated that muscle characteristics in camels are influenced by season.     

Effect of South African beef production systems on post-mortem muscle energy status and meat quality

Post-slaughter muscle energy metabolism meat colour of South African production systems were compared; steers (n = 182) of Nguni, Simmental Brahman crossbreds were reared on pasture until A-, AB-, or B-age, in feedlot until A–AB-age. After exsanguination carcasses were electrically stimulated (400 V for 15 s). M. longissimus dorsi muscle energy samples were taken at 1, 2, 4 and 20 h. Post-mortem samples for meat quality studies were taken at 1, 7 and 14 days post-mortem. Production systems affected muscle glycogen, glucose, glucose-6-P, lactic acid, ATP, creatine-P glycolytic potential (P < 0.05), with the muscles of feedlot carcasses having a faster glycolysis rate than pasture carcasses. Energy metabolites correlated (0.4 < r < 0.9) with meat colour (CIE, L*a*b*), (0.3 < r > 0.5) water holding capacity, drip loss, and Warner Bratzler shear force. Muscle energy only affected muscle contraction of the A-age-pasture system (shortest sarcomere length of 1.66 μm vs 1.75 μm highest WBS of 6 kg vs 5 kg 7 days post-mortem).     

Effect of fiber type on postmortem proteolysis in longissimus muscle of Landrace and Korean native black pigs

The current study was conducted to characterize objective meat quality, fiber type and their relations to postmortem proteolysis in longissimus muscle of Landrace and Korean native black (KNP) pigs. Longissimus muscles from each 10 market-weighted male pigs were removed after conventional slaughtering and chilling procedures, and aged for 1 or 7 days at 4 °C to determine WB-shear force, objective meat color, proportion of myosin heavy chain I (MyHC I), intramuscular fat content and rate of proteolysis by a proteomics approach. KNP had a significantly (p < 0.05) higher content of MyHC I, and that concurred with greatly (p < 0.05) higher intramuscular fat content and Hunter a^* value, and significantly (p < 0.05) lower drip loss than those seen in Landrace. One-dimension SDS-PAGE indicated that GAPDH, troponin I and creatine kinase were prominent proteolytic products during chiller ageing. By applying a gel-based proteome analysis, 26 proteins were identified, which showed different degradation properties during ageing between the breeds. Biopsied sample revealed that myosin regulatory light chain 2, myosin light chain isotype v/sb, fatty acid-binding protein and albumin were expressed at a greatly higher level for KNP, but their relation to fiber type (or genetic background) is unclear. It was particular noticeable that different actin isoforms showed various degradation behavior during ageing time.     

The characteristics of muscle fiber types of longissimus thoracis muscle and their influences on the quantity and quality of meat from Japanese Black steers

Forty-four Japanese Black fattening steers from four groups, produced in four districts and consisting of differing genetic backgrounds were slaughtered to examine the characteristic differences in muscle fiber types at the 6th thoracic vertebra of the M. longissimus thoracis (LT). The influence of percentage, diameter, and relative area of each muscle fiber type on the carcass characteristics and some quantity and quality traits of beef taken from LT, were also investigated. Significant differences in the characteristics of the muscle fiber types were observed among the four groups, except for muscle fiber diameter in the αR fiber, and the relative area of each αW fiber. For all steers, the average percentages and diameters of each muscle fiber type, βR, αR and αW were 26.8, 18.5 and 54.7% and 51.4, 50.6 and 52.4 μm, respectively. The relative area of each fiber type was similar to those of muscle fiber composition. αR Fiber content had significant negative correlations with marbling score (p<0.05), intramuscular fat content (p<0.05) and ultimate pH value (p<0.05). Significant correlations between the diameter of each fiber type, and the quantity or quality traits of the meat were not found, with the exception of red fiber types (βR and αR) and meat color a(?) values (p<0.05) which were positively correlated.     

Effects of breed and a concentrate or grass silage diet on beef quality in cattle of 3 ages. I: Animal performance, carcass quality and muscle fatty acid composition

An increase in the intake of the n-3 series polyunsaturated fatty acids (PUFA) is recommended by nutritionists for the human diet and beef is a significant source of these fatty acids. Enhancing the n-3 PUFA content of beef is important in view of the generally saturated nature of fatty acids in ruminant meats and the potentially negative effect this can have on human health. This study examined the effects of breed and diet on the fatty acid composition of beef M. longissimus. Ninety-six steers were used, 48 Aberdeen Angus cross (AA) and 48 Holstein-Friesian (HF). At 6months of age, 3 groups were identified, to be slaughtered at 14, 19 and 24months, respectively. Each group consisted of eight steers of each breed fed on a concentrate or a grass silage diet, rich in n-6 and n-3 PUFA, respectively. The intake of the concentrate diet was restricted so that steers of each breed grew at a similar rate on each diet. The early maturing AA produced heavier, fatter carcasses with better conformation. Animals fed grass silage had higher carcass fatness and conformation scores and higher levels of neutral lipid and total lipid in muscle than those fed concentrate. When all animals were pooled, a decline in PUFA% as total muscle lipid increased was evident. Feeding a grass silage diet rich in α-linolenic acid (18:3n-3) increased levels of this fatty acid in muscle neutral lipid by a factor of about 3.0 compared with the concentrate diet, as well as enhancing the synthesis of the n-3 series long-chain C20-22 PUFA in the phospholipid fraction, including docosahexaenoic acid (DHA, 22:6n-3). In contrast, both levels and proportions of linoleic acid (18:2n-6) and the n-6 series C20-22 PUFA were higher in animals fed the concentrate diet. The proportions of 18:1trans and conjugated linoleic acid (CLA) in muscle neutral lipid were higher in animals fed concentrate compared with silage in all 3 groups. This was partly due to increased consumption of 18:2n-6. The ratio of PUFA to saturated fatty acids (P:S) in muscle was reduced by feeding grass silage, partly as the result of increased fat deposition. However, the increase in levels of n-3 series fatty acids with silage-feeding resulted in beneficially low n-6:n-3 ratios in muscle in all age groups (approximately 1.2 compared with 12.0 in the concentrate diet). Subtle breed differences in PUFA amounts and proportions were noted. Holstein-Friesians had higher proportions of PUFA and higher P:S ratios compared with AA, partly due to a higher proportion of phospholipid in total lipid. In phospholipid itself, HF in the 19 and 24months groups had higher proportions of most n-3 PUFA. In all age groups the ratio of DHA to its precursor, 18:3n-3 was higher in HF.     

Effects of milk replacer feeding strategies on performance,ruminal development,and metabolism of dairy calves

Performance, rumen development, and metabolism of male Holstein calves (n = 54) were evaluated according to 1 of 3 liquid feeding strategies: 4 L of milk replacer (MR)/d until 60 d old (4L-60d), 6 L of MR/d until 29 d old and 4 L/d from 30 to 60 d (6L-29d/4L-60d), or 6 L of MR/day until 60 d old (60d-6L). Water and starter were provided ad libitum. Intakes of MR and starter were monitored daily and body weight (BW) weekly. Blood samples for glucose and insulin concentrations and ruminal content samples for volatile fatty acids and ruminal ammonia concentrations were collected at 15, 30, 45, 60, 75, and 90 d of age. Six calves on each treatment were euthanized at 30, 60, and 90 d of age. Empty weights of forestomach and abomasum, papillae length, and mitotic index were measured. Average MR intake/d (expressed as a percent of BW) was greater for calves receiving 6 L/d than for those receiving 4 L/d until 30 d of age. Calves on the 6L-29d/4L-60d had the smallest MR intake from 30 to 60 d old, followed by the 4L-60d and 6L-60d treatments. Starter intake (kg of dry matter/day) did not differ between groups. It increased from 0.065 kg/d in the first month to 0.386 kg/d in the second month, and to 2.065 kg/d after weaning. Weight gain was greater for calves fed more MR in the first month, but no difference was observed during the second month. After weaning, 6L-60d calves had greater rate of weight gain than others and were heavier at 30, 60, and 90 d of age. Weight of empty forestomachs, ruminal pH, and ammoniac nitrogen concentration were not different among groups. Propionate concentration was lower for 6L-60d calves, but acetate and butyrate concentrations were not influenced by MR feeding strategy. Calves fed more MR until d 30 had greater ruminal epithelium mitotic index. The different MR feeding strategies did not influence papillae length or ruminal epithelium thickness. Lesions such as ruminal parakeratosis or hyperkeratosis were not observed. The MR feeding strategy did not affect glucose concentration, but insulin was higher in 6L-60d calves than in the other groups. Glucose concentration increased with age, whereas insulin decreased until 45 d old, and then started to increase until 90 d. In conclusion, MR feeding strategy did not influence ruminal development. Feeding calves 6 L of MR/d over 60 d resulted in greater rate of weight gain without negative effects on starter intake or forestomach development. The weight advantage that 6L-60d calves obtained preweaning was maintained until 90 d of age.     

Effect of feeding treatment during the backgrounding phase of beef production from pasture on: I. Animal performance, carcass and meat quality

This research evaluated effects of feedlot backgrounding on 40, 70 or 100% alfalfa hay diets (40hay, 70hay; 100hay, respectively) or pasture grazing (Pasture) before pasture finishing, on performance and beef characteristics of Angus heifers. Ninety six female calves were allocated to the four feeding strategies. Backgrounding took place during 114 days and subsequent pasture finishing over 132 days. Heifers of each strategy were slaughtered after 114 days (end of the feedlot period) and at end of the study when all remaining animals were finished on pasture. Effects of backgrounding were associated with rate of gain. Backgrounding strategies 40hay and Pasture resulted in the best performance. Beef attributes were similar. At the end of the feedlot period, 100hay was smaller and leaner, less tender and less juicy. At the end of the study, Pasture and 40hay heifers had on average the largest back fat thickness and intramuscular fat measurements. No treatment effects were detected for Warner-Bratzler shear force, muscle pH, muscle color and sensory panel attributes.     

Effect of silk flower hay (Calotropis procera Sw) feeding on the physical and chemical quality of Longissimus dorsi muscle of Santa Inez lambs

The effect of different levels of silk flower hay (Calotropis procera Sw) in the diet of confined lambs by the substitution of the commonly used foraging broom corn hay (Sorghum bicolor L) was investigated to evaluate its possible effects on the growth and quality of the lamb meat. Twenty-four male Santa Inez lambs were divided in equal numbers into four treatment groups and fed diets containing 0%, 16.7%, 33.3% and 50% of silk flower hay (SFH). Growth rate, feed intake and meat quality were investigated. Mean daily gains of lambs were 170 g for control, 180.5 g for 16.7% SFH, 96.8 g for 33.3% SFH and 22.9 g for 50% SFH. The use of silk flower hay in the diet of Santa Inez lambs affected health of the animals and meat pH when the substitution of the forage was high, up to 50%; however, the general meat quality was not affected. Meat from animals fed with levels up to 50% SFH had physical (Aw, a^*, b^* and L^*) and chemical (moisture, ash, lipid, phosphorus, iron, phospholipid and fatty-acid profile) parameters comparable to the control group (0% SFH). Among the various levels of substitution (16.7%, 33.3% and 50%) of silk flower hay in the diet tried in this work, the use of 16.7% was found to be an attractive and technically viable option for the Northeast region of Brazil.     

Reconstituted versus dry alfalfa hay in starter feed diets of Holstein dairy calves: Effects on growth performance,nutrient digestibility,and metabolic indications of rumen development

We investigated the effect of reconstitution of alfalfa hay on starter feed intake, nutrient digestibility, growth performance, rumen fermentation, selected blood metabolites, and health criteria of dairy calves during the pre- and postweaning periods. A total of 20 newborn male Holstein calves (3 d of age; 40.3 ± 1.30 kg of body weight; ±SE) were assigned randomly to 1 of 2 treatments, a starter feed containing either 10% dry (AH) or reconstituted alfalfa hay (RAH), each consisting of 10 calves. Alfalfa hay was reconstituted with water 24 h before feeding to achieve a theoretical dry matter content of 20%. Both starter feeds had the same ingredients and nutrient compositions but differed in their dry matter content (91.2 and 83.8% dry matter for AH and RAH, respectively). Calves were weaned on d 50 and remained on the study until d 70. All calves had free access to fresh and clean drinking water and the starter feed at all times. During the study period, the average maximum temperature-humidity index was 73.8 units, indicating no degree of environmental heat load for dairy calves. Starter feed dry matter intake, total dry matter intake, and body weight (at weaning and at the end of the trial) were unaffected by treatment. Nutrient intake (except for total ether extract intake) increased during the postweaning period compared with the preweaning period. Average daily gain and feed efficiency were unchanged between treatments. Calves had higher average daily gain and skeletal growth during the postweaning period; however, feed efficiency was lower during the post- versus preweaning period. Calves fed RAH gained more hip width and body barrel compared with calves fed AH during the preweaning and all studied periods, respectively. Rectal temperature was similar between treatments, but feeding RAH decreased fecal score and general appearance score during the preweaning period. Apparent total-tract nutrient digestibility was not affected by reconstitution of alfalfa hay; however, reconstitution increased total-tract digestibility of neutral detergent fiber during the postweaning period. Ruminal fluid pH, and concentrations and profile of total volatile fatty acids were unchanged between treatments. Molar concentration of propionate and acetate to propionate ratio increased and decreased, respectively, during the postweaning period. Reconstitution of alfalfa hay did not affect concentrations of glucose, β-hydroxybutyrate, blood urea N, and albumin, and albumin to globulin ratio during the studied periods; however, reconstitution increased concentration of blood total protein during the overall period. Calves had higher concentrations of blood glucose and globulin during the preweaning and β-hydroxybutyrate during the postweaning period. Overall, reconstitution of alfalfa hay did not interact with calf phase (pre- vs. postweaning) to affect dry matter intake, growth performance, and metabolic indications of rumen development (measured as ruminal volatile fatty acids and selected blood metabolites), but improved health-related variables (fecal score and general appearance score) during the preweaning period.     

Effects of forage provision to young calves on rumen fermentation and development of the gastrointestinal tract

Fifteen Holstein male calves were randomly assigned to 1 of 3 dietary treatments according to age and body weight (BW) to determine the effects of feeding different forages sources on rumen fermentation and gastrointestinal tract (GIT) development. Treatments consisted of a starter (20% crude protein, 21% neutral detergent fiber) fed alone (CON) or supplemented with alfalfa (AH) or with oat hay (OH). All calves received 2 L of milk replacer (MR) at 12.5% dry matter twice daily until 49 d of age. Calves received 2 L of the same MR from 50 to 56 d of age and were weaned at 57 d of age. Individual starter, forage, and MR intakes were recorded daily and BW was recorded weekly. A rumen sample was taken weekly to determine rumen pH and volatile fatty acid concentrations. Three weeks after weaning, animals were harvested and each anatomical part of the GIT was separated and weighed with and without contents. Rumen pH was lower in CON than in OH and AH calves. Furthermore, acetate proportion in the rumen liquid tended to be greater in AH than in CON and OH treatments. Total GIT weight, expressed as a percentage of BW, tended to be greater in AH compared with the other 2 treatments. Rumen tissue tended to weigh more in CON than in OH animals. Animals with access to forage tended to have a greater expression of monocarboxylate transporter 1 than CON calves. In conclusion, calves supplemented with oat hay have a better rumen environment than calves offered no forage and do not have an increased gut fill.     

Influence of blade tenderization,moisture enhancement and pancreatin enzyme treatment on the processing characteristics and tenderness of beef semitendinosus muscle

The combined effect of blade tenderization (BT), moisture enhancement and enzymatic tenderization on drip loss, cook loss, Warner–Bratzler shear force (WBSF) and sensory characteristics of beef semitendinosus (ST) steaks from cattle under 30 months of age was investigated.     

Influence of feeding supplements of almond hulls and ensiled citrus pulp on the milk production,milk composition,and methane emissions of dairy cows

Almond hulls and citrus pulp have been fed to dairy cows with variable responses for milk production, but no information exists on their effect on enteric methane emissions. This experiment examined the effects of dietary supplementation with either almond hulls or ensiled citrus pulp on the milk yield, milk composition, and enteric methane emissions of dairy cows. Thirty-two Holstein dairy cows in mid lactation were offered 1 of 3 diets over a 28-d experiment. Twelve cows received a control (CON) diet, 10 cows a diet containing almond hulls (ALH), and 10 cows a diet containing ensiled citrus pulp (CIT). All cows were offered 6.0 kg of dry matter (DM)/d of crushed corn, 2.0 kg of DM/d of cold-pressed canola, and 0.2 kg of DM/d of a mineral mix. In addition, cows fed the CON diet were offered 14.5 kg of DM/d of alfalfa cubes; cows fed the ALH diet were offered 10.5 kg of DM/d of alfalfa cubes and 4.0 kg of DM/d of almond hulls; and cows on the CIT diet were offered 11.5 kg of DM/d of alfalfa cubes and 3.0 kg of DM/d of ensiled citrus pulp. Milk yield was measured daily and milk composition was measured on 4 d of each week. Individual cow methane emissions were measured by a sulfur hexafluoride tracer technique on d 24 to 28 of the experiment. The mean milk yield of cows fed the CON diet (27.4 kg/d) was greater than the mean milk yield of cows fed the ALH diet (24.6 kg/cow per day), whereas the mean milk yield of cows fed the CIT diet (26.2 kg/cow per day) was not different from the mean milk yield from cows fed the other 2 diets. Dietary treatment did not influence the concentrations of milk fat, protein, and lactose or fat yields, but the mean protein yield from cows fed the CON diet (0.87 kg/d) was greater than that from cows fed the ALH diet (0.78 kg/d) but not different to those fed the CIT diet (0.85 kg/d). In general, we found no differences in the proportion of individual fatty acids in milk. The mean pH of ruminal fluid from cows offered the CON diet was not different to the pH in the ruminal fluids of cows offered the ALH or the CIT diets. The mean methane emissions (g/d) and yields (g/kg of DM intake) were not influenced by dietary treatment. These findings indicate that, although almond hulls and ensiled citrus pulp can be used as a low-cost feed supplement, almond hulls did negatively affect milk production and neither inhibited enteric methane emissions.     

Influence of freezing and thawing on the hydration characteristics,quality, and consumer acceptance of whole muscle beef injected with solutions of salt and phosphate

Effects of salt/phosphate injection level (112% or 125% pump), salt level (0.5% or 1.5% salt), and freezing/thawing on hydration characteristics, quality, and consumer acceptance of beef semitendinosus were investigated. All enhancement treatments decreased shear force by 25–35%, but negatively affected colour. Increased salt concentration yielded lower purge and cooking losses, and higher water holding capacity. The higher injection level reduced water binding properties, however, the loss in functionality with higher water addition was overcome with increased salt content. Freezing and subsequent thawing was generally detrimental to colour and water binding properties and tended to increase shear force. Freezing and subsequent thawing did not affect fluid release in steaks held for 1 day before analysis, but resulted in decreased water retention in samples held for 7 days. Holding vacuum packaged steaks for 7 days generally increased package purge and negatively affected colour parameters, although water binding characteristics were improved. Consumer panel results demonstrated a negative effect on juiciness and tenderness where meat subject to low salt/high injection was frozen then thawed – the low salt level was insufficient to maintain any positive effect of injection treatment. In general, salt/phosphate injection improved product acceptability and increased willingness to purchase.     

A comparison between red clover silage and grass silage feeding on fatty acid composition, meat stability and sensory quality of the M. Longissimus muscle of dairy cull cows

Sixteen Holstein–Friesian dairy cull cows were offered either ad libitum grass (G) or red clover (RC) silage for 12 weeks. Dry matter (DM), total nitrogen, and pH was higher for the RC than the G silage and organic matter, water-soluble carbohydrate, fibre, DM digestibility, ammonia-N, vitamin E and acetic acid higher for the G silage (P < 0.05). Fatty acid compositions were different (P < 0.05) with G silage having higher levels of C12:0, C14:0, C16:1cis−9, C18:3n−3 and total fatty acids whereas RC had higher levels of C18:0, C18:2n−6 and C20:0. Daily liveweight gain was high and not different between groups (average 1.22 kg/d). Body condition score and back fat thickness at slaughter along with conformation, fat grade and slaughter weight were not different between groups. Animals offered the G silage produced larger M. longissimus length (P < 0.01) and a trend (P < 0.1) for width. RC fed animals had higher proportions of C18:3n−3 (P < 0.001), total n−3 fatty acids (P < 0.01) and total PUFA compared to animals offered the G silage despite greater intakes of these fatty acids on G (P < 0.001). Vitamin E concentration and stability of aged meat during simulated retail display, were lower (P < 0.05) from animals offered RC than animals offered G. Shear force and ultimate pH, however were not different in steaks and sensory attributes were similar; the only difference being a higher score (P < 0.01) for fishy in the RC steaks. The results suggest that feeding high DMD silage to dairy cull cows can result in a high standard of finish and liveweight gain. Furthermore RC silage as opposed to G silage can increase the beneficial fatty acid profile of the resultant meat.     

Effect of feeding extruded flaxseed with different grains on the performance of dairy cows and milk fatty acid profile

Sixteen Holsteins cows were used in a Latin square design experiment to determine the effects of extruded flaxseed (EF) supplementation and grain source (i.e., corn vs. barley) on performance of dairy cows. Extruded flaxseed diets contained 10% [dry matter (DM) basis] of an EF product that consisted of 75% flaxseed and 25% ground alfalfa meal. Four lactating Holsteins cows fitted with rumen fistulas were used to determine the effects of dietary treatments on ruminal fermentation. Intakes of DM (23.2 vs. 22.2 kg/d), crude protein (4.2 vs. 4.0 kg/d), and neutral detergent fiber (8.3 vs. 7.9 kg/d) were greater for cows fed EF diets than for cows fed diets without EF. Milk yield and composition were not affected by dietary treatments. However, 4% fat-corrected milk (30.5% vs. 29.6 kg/d) and solids-corrected milk (30.7 vs. 29.9 kg/d) were increased by EF supplementation. Ruminal pH and total volatile fatty acid concentration were not influenced by EF supplementation. However, feeding barley relative to corn increased molar proportions of acetate and butyrate and decreased that of propionate. Ruminal NH₃-N was lower for cows fed barley than for cows fed corn. Milk fatty acid composition was altered by both grain source and EF supplementation. Cows fed EF produced milk with higher polyunsaturated and lower saturated fatty acid concentrations than cows fed diets without EF. Feeding EF or corn increased the milk concentration of C18:0, whereas that of C16:0 was decreased by EF supplementation only. Extruded flaxseed supplementation increased milk fat α-linolenic acid content by 60% and conjugated linoleic acid content by 29%. Feeding corn relative to barley increased milk conjugated linoleic acid by 29% but had no effect on milk α-linolenic concentration. Differences in animal performance and milk fatty acid composition were mainly due to EF supplementation, whereas differences in ruminal fermentation were mostly due to grain source.