Colour of fat,and colour,fatty acid composition and sensory characteristics of muscle from heifers offered alternative forages to grass silage in a finishing ration

The effect of type of silage offered to beef heifers during the finishing period on aspects of beef quality was determined. In two experiments, a diet based on grass silage (GS) was compared with a diet based on maize silage (MS) or whole-crop wheat silage (WCW). Compared to the GS-based diet, increasing the amount of MS linearly increased fat whiteness while the increase in fat whiteness due to WCW was dependent on the stage of crop maturity at harvesting. There was no effect of diet on muscle colour or on muscle pH measured at 48 h post-mortem, drip loss, taste panel traits after 14 days ageing or shear force values at 2, 7 or 14 days ageing. The alternative silages decreased the n − 3 polyunsaturated fatty acid proportion and increased the linoleic:linolenic acid ratio in intramuscular lipid. It is concluded that type of silage affects fat colour and fatty acid composition of muscle but not the other muscle characteristics examined.     

Meat quality of steers finished on autumn grass, grass silage or concentrate-based diets

The objective of this experiment was to determine the effect of varying the proportions of autumn grass and concentrates and grass silage and concentrates on the quality of meat from cattle with similar rates of carcass growth. Fifty continental crossbred steers were assigned to five treatments. The experimental diets offered were (1) grass silage ad libitum plus 4 kg concentrate (SC), (2) 1 kg hay plus 8 kg concentrate (CO), (3) 6 kg grass dry matter (DM) plus 5 kg concentrate (CG), (4) 12 kg grass DM plus 2.5 kg concentrate (GC) and (5) 22 kg grass DM (GO). The experiment lasted 85 days after which all animals were slaughtered. The right side m. longissmus dorsi was excised from all animals 24 h post slaughter for assessment of meat quality. Treatments SC and CO resulted in animals with whiter (P<0.05) subcutaneous and kidney/channel fat than all other treatments. There was an interaction (P<0.05) between ageing time and treatment with treatment GC having higher (P<0.05) tenderness, texture and acceptability values after 2 days ageing, but not after 7 or 14 days ageing. It is concluded that supplementing grass with low levels of concentrate produced the most tender and acceptable meat at 2 days post mortem, but that further ageing eliminated all treatment effects on eating quality of beef.     

Effects of the inclusion of sodium bicarbonate and sugar beet pulp in the concentrate for fattening lambs on acid-base status and meat characteristics

Thirty-six young Merino lambs (15.3 kg live weight) were allocated into four equal groups to study the effects of the inclusion of sodium bicarbonate (‘Bic’, 0 vs. 2%) and sugar beet pulp (‘SBP’, 0 vs. 12%) in the concentrate on meat characteristics. Lambs were fed barley straw and concentrate ad libitum. When they reached 25 kg a blood sample was taken and the animal slaughtered. After 24 h meat characteristics (pH, colour, water holding capacity, Warner–Bratzler shear force, chemical and fatty acid – ‘FA’ – composition) were measured on M. longissimus thoracis et lumborum. SBP replacing 24% of the barley in the concentrate caused an increase in shear force (P < 0.05) and saturated FA (P < 0.05), decreasing meat unsaturated FA (P < 0.05). SB increased blood base excess (P < 0.05) and meat yellowness (P < 0.05) and decreased meat pH (P < 0.05), without altering any other meat characteristics.     

Effects of a compensatory growth strategy on sensory and physical properties of meat from young bulls

The objective of the present study was to investigate the sensory properties, with special emphasis on tenderness, of meat from strategically fed young bulls (13 months of age) slaughtered when a plateau in protein turnover was observed. Twelve Holstein Friesian young bulls were divided into two feeding strategies. One group of young bulls (n = 6) were fed ad libitum throughout the rearing period (AD) whereas the second group (n = 6) was subjected to a compensatory growth feeding strategy (CO). Sensory profiling of beef longissimus dorsi (LD), semimembranosus (SM) and supraspinatus (SS) was performed in addition to physical measurements (shear force) and content of intramuscular fat of LD. The data was analysed using a regression-based multivariate data analytical strategy. In relation to predictivity of the various shear force measurement constituents for sensory texture, it was determined that a number of the responses collected (e.g. max_mm), in addition to the commonly used max_(N) may be utilised to predict subtlety in the sensory texture differences of the samples (e.g. Crumbliness) with respect to compensatory feeding. Through profiling LD and SS were found to have enhanced texture and flavour properties when the young bulls were fed ad libitum during rearing. However, the SM samples were found to improve in characteristics regarding texture and appearance when the young bulls had been fed compensatorily. Thus, compensatory feeding as a texture improvement strategy proved to be highly dependant on muscle type. Of note, LD and SS were found to develop an off-flavour designated as ‘steer taint’ when derived from compensatory feeding. This was postulated as potentially not a problem for the consumer, in LD as the level was not significant, and in SS due to sensory masking when commonly prepared as a stew or casserole. Considering the different preparation methods used for meat from LD, SM and SS, compensatory feeding may be considered to have improved the texture and elevated the eating quality where it was most relevant, namely in SM roasts.     

The eating quality of meat of steers fed grass and/or concentrates

The objective was to determine, relative to animals expressing their full potential for carcass growth, the impact on meat quality of increasing carcass growth of grazing steers by supplementing with concentrates or by increasing grass supply. Sixty-six continental (Limousin and Charolais) crossbred steers (567 kg) were assigned to one of six diets: (1) 18 kg grass dry matter (DM); (2) 18 kg grass DM grass and 2.5 kg concentrate; (3) 18 kg grass DM and 5 kg concentrate; (4) 6 kg grass DM and 5 kg concentrate; (5) 12 kg grass DM and 2.5 kg concentrate; or (6) concentrates daily. Animals were slaughtered after an average of 95 days. Samples of the M. longissmus dorsi (LD) were collected at the 8–9th rib interface and subjected to sensory analysis and to other assessments of quality following 2, 7, or 14 days aging. Carcass weight gain averaged 360, 631, 727, 617, 551 and 809 g/day for treatments 1 to 6, respectively. There was no difference between diets for colour, Warner–Bratzler shear force (WBSF) or any sensory attribute of the LD. WBSF was negatively correlated with (P<0.05) carcass growth rate (−0.31) but only a small proportion of the variation in meat quality between animals could be attributed to diet pre-slaughter or carcass fatness. It is concluded that high carcass growth can be achieved on a grass-based diet without a deleterious effect on meat quality.     

Effects of management practices prior to and during ensiling and concentrate type on nitrogen utilization in dairy cows

Three experiments with a total of 18 multiparous Holstein-Friesian dairy cows in early to mid lactation were used in incomplete changeover designs with four periods consisting of 4 wk each. The objectives of the experiments were to investigate the effects of 1) grass management practices prior to ensiling and 2) concentrate energy sources on animal performance and N utilization and suggest ways in which the annual N excretion can be reduced. In the first experiment, four silages were prepared as early-cut material from grass that was fertilized with either 75 or 150 kg of N/ha. Two other silages were prepared from the latter but harvested 2 wk later. Within each silage type, both direct cut and wilted silages were produced. In the second experiment, starch-based and fiber-based concentrates were offered with the three wilted silages used in the previous experiment. In the third experiment, barley-based and corn-based concentrates were offered with three silages that had been treated with different additives at the time of ensiling. Neither dry matter intake nor milk yield were significantly affected by either silage or concentrate type. Milk protein content and yield, however, were higher in silages made from medium fertilized grass and also increased with increased starch content of the concentrate. Grass management and diet affected the amount and form of N excreted. Use of nitrogen fertilizer at lower than 75 kg of N/ha and feeding less degradable starch concentrate is recommended for mitigation of N pollution, especially in the form of urine N by dairy cows in intensive farming.     

Energy supply patterns for finishing steers: Feed conversion efficiency, components of bodyweight gain and meat quality

The objective was to determine the effect of pre-slaughter growth rate on feed efficiency, components of body growth and on the tenderness of longissimus muscle from steers reared to a common age and carcass weight. Sixty Friesian steers were group-housed and offered grass silage ad libitum and 3.5kg concentrates per animal daily for 5 months and then 5kg concentrates and 1kg grass hay for 1month before the experiment began. The animals were then weighed and in a randomised block were assigned to one of 5 groups, for slaughter at the beginning of the experiment or to be offered concentrates and hay (900 and 100g/kg total diet, respectively) to achieve target growths of: 0.72kg/day continuously for 17 weeks, 0.36kg/day for the first 8 weeks and 1.08kg/day for the final 8 weeks (low-high), 1.08kg/day for the first 8 weeks and 0.36 for the final 8 weeks (high-low) or 0.36kg/day for the first 2 weeks, 0.72kg/day during weeks 4 and 14 and 1.08kg/day for the final 2 weeks (pulse). One week was allowed for transition to the different dietary allowances within each energy supply pattern. The mean age at the beginning and end of the study was 18 and 22.5 months, respectively. After slaughter, the weight of the carcass and kidney+channel fat depot were recorded, the pistola hind quarter was dissected into fat, lean and bone and the tenderness of the m. longissimus thoracis et lumborum (LTM) muscle was measured instrumentally and using a trained taste panel after 2, 7 or 14 days ageing. The pattern of energy supply did not affect carcass weight, fat score or kidney+channel fat weight. The pistola hind quarter from animals offered the low-high energy pattern had a similar composition to the continuously-fed animals but contained more muscle than that from animals offered high-low or pulse energy patterns. After 14 days ageing, LTM from the continuously-fed animals was more tender than that from animals offered the other energy supply patterns but shear force did not differ between supply patterns. The data do not support the hypothesis that pre-slaughter growth rate increases tenderness but suggest that energy supply pattern can influence body composition of finishing cattle.     

The volatile profile of longissimus dorsi muscle of heifers fed pasture, pasture silage or cereal concentrate: implication for dietary discrimination

The aim of this study was to determine the effect of different diets on beef meat volatile organic compounds (VOC). Seven heifers grazed pasture for twelve months (group P); 8 heifers received grass silage ad libitum indoors for six months and then were switched to pasture for six months (group SiP); 8 heifers received grass silage ad libitum indoors for six months and then switched to pasture and also offered 0.5 of the diet dry matter of concentrate for six months (group SiPC); 8 heifers received concentrate for twelve months (group C). The muscle longissimus dorsi was sampled at slaughter and subjected to VOC analysis by SPME-GC-MS. Some aldeyhdes, ketones and furans deriving from lipid oxidation were affected by the treatments. Skatole, 3-undecanone, cuminic alcohol and 1-butanol, 2-methyl allowed the discrimination between animals fed concentrate from animals fed non-concentrate diets. Germacrene D, a terpenoid, was a marker of grass feeding.     

Effects of level of concentrate feeding during the second gestation of Holstein-Friesian dairy cows. 1. Feed intake and milk production

The objective of this experiment was to examine the residual effects of the level of concentrate feeding during the second gestation on performance in the second lactation. Forty-three Holstein-Friesian heifers that calved for the first time at 2 or 3 yr of age were offered diets based on ad libitum consumption of ryegrass silage and either 2 or 7 kg/d of concentrates over the second half of the first lactation. All cows received a low quality diet, based on grass silage and barley straw (60:40 DM basis) for a short (6-wk) dry period. Feeding in the second lactation was based on ad libitum access to grass silage and a flat rate of concentrates (8 kg/ d for 120 d; 5 kg/d thereafter). Three-year-old heifers produced more milk than 2-yr old heifers in the first lactation, equivalent to 93 kg of fat-corrected milk for each additional month of rearing. Cows given the low level of concentrates produced less milk and gained less weight and body condition, though there was a partial compensation when silage quality improved in late lactation. Forage intake declined as cows approached calving, and cows gained little weight or body condition over the dry period. There was no effect on calf weights. Cows that had received the low level of concentrates in the previous lactation consumed more forage dry matter during the second lactation. Parallel curve analysis showed that 2-yr-old heifers that had received a low level of concentrates produced significantly less milk in the second lactation. The numerically much greater gains of weight and body condition for this group were not statistically significant, owing to large between-cow variation.     

Concentrate supplementation of a diet based on medium-quality grass silage for 4 weeks prepartum: Effects on cow performance,health, metabolic status,and immune function

Because negative energy balance (EB) contributes to transition-period immune dysfunction in dairy cows, dietary management strategies should aim to minimize negative EB during this time. Prepartum diets that oversupply energy may exacerbate negative EB in early lactation, with detrimental effects on immune function. However, with lower body condition score (BCS) cows, it has been shown that offering concentrates in addition to a grass silage-based diet when confined during an 8-wk dry period resulted in increased neutrophil function in early lactation. The aim of this study was to examine if similar benefits occur when concentrate feeding was restricted to a 4-wk period prepartum. Twenty-six multiparous and 22 primiparous Holstein-Friesian cows were offered ad libitum access to medium-quality grass silage until 28 d before their predicted calving dates (actual mean of 32 d prepartum; standard deviation = 6.4). At this time multiparous cows had a mean BCS of 2.9 (standard deviation = 0.12) and primiparous cows a mean BCS of 3.0 (standard deviation = 0.14) on a 1 to 5 scale. Cows were then allocated in a balanced manner to 1 of 2 treatments (13 multiparous cows and 11 primiparous cows on each treatment): silage only (SO) or silage plus concentrates (S+C) until calving. Cows on SO were offered the same grass silage ad libitum. Cows on S+C were offered an ad libitum mixed ration of the same grass silage and additional concentrates in a 60:40 dry matter (DM) ratio, which provided a mean concentrate DM intake (DMI) of 4.5 kg/cow per d. After calving, all cows were offered a common mixed ration (grass silage and concentrates, 40:60 DM ratio) for 70 d postpartum. Offering concentrates in addition to grass silage during the 4 wk prepartum increased prepartum DMI (12.0 versus 10.1 kg/cow per d), EB (+40.0 versus +10.6 MJ/cow per d), and body weight (BW; 640 versus 628 kg), and tended to increase BCS (3.02 versus 2.97). However, postpartum DMI, milk yield, milk composition, BW change, BCS change, serum nonesterified fatty acid, and β-hydroxybutryrate concentrations, health, and corpus luteum measures were unaffected by treatment. The in vitro assays of neutrophil phagocytosis, neutrophil oxidative burst, and interferon gamma production, conducted on blood samples obtained at d 14 prepartum and d 3, 7, 14, and 21 postpartum, were unaffected by treatment. Primiparous cows had higher phagocytic fluorescence intensity at d 14 prepartum and d 3 and 7 postpartum; a higher percentage of neutrophils undergoing oxidative burst at d 3, 7, and 21 postpartum; and a higher oxidative burst fluorescence intensity at d 14 prepartum and d 7, 14, and 21 postpartum compared with multiparous cows. This suggests that neutrophil function of primiparous cows was less sensitive to the changes occurring during the transition period than that of multiparous cows. In conclusion, offering concentrates during the 4-wk period prepartum had no effect on postpartum DMI, milk yield, body tissue mobilization, EB, measures of neutrophil or lymphocyte function, health, or corpus luteum activity.     

Rumen acid production from dairy feeds. 1. Effects on feed intake and milk production of dairy cows offered grass or corn silages

Earlier studies developed a new approach to feed evaluation, measuring the net acid load that develops during rumen fermentation. Two concentrates were formulated to be isoenergetic and isonitrogenous, with extremes of rumen acid load. A third treatment comprised a 50:50 mixture of these concentrates. These concentrates were evaluated along with ryegrass silage and corn silage. The feeds were evaluated in a continuous culture system adapted to deliver and record the quantities of acid or alkali needed to maintain a constant pH (6.2 to 6.3). This study confirmed the anticipated ranking of concentrates for rumen acid load, as well as the highly acidogenic nature of corn silage. The concentrates were formulated to balance corn silage and were offered to early-lactation Holstein-Friesian cows at 50% of dry matter intake, with either ryegrass silage or corn silage. Feed intake was lower for animals offered corn silage-based diets (17.4 vs. 22.2 kg of dry matter/d). Increasing concentrate acid load led to a large decline in dry matter intake for corn silage, although not for grass silage. Feed intake effects were reflected in significant effects on yield of milk (31.0, 29.9, and 26.9 kg/d for low-, medium-, and high-acid load concentrates, respectively) and milk solids. Milk protein concentration was unaffected by concentrate type with corn silage diets but tended to be higher when high acid load concentrates were fed with grass silage. This may reflect the effect of the high starch concentrate rectifying a shortage of glucogenic precursors or microbial protein with the grass silage-based diet.     

Early lactation feed intake and milk yield responses of dairy cows offered grass silages harvested at early maturity stages

The main objective was to evaluate the potential of grass silages of very high quality to support a high milk yield with a low or moderate, or even without concentrate supplementation. Production responses to increased levels of concentrate supplementation with 3 primary growth grass silages differing in digestibility were studied using 66 Norwegian Red dairy cows. Roundbale silage was produced from a timothy-dominated sward at very early (H1), early (H2), and normal (H3) stages of crop maturity. Crops were rapidly wilted (<24h) and a formic acid-based additive was applied. All silages were restrictedly fermented. Silage digestible organic matter in dry matter (DM) values were 747, 708, and 647 g/kg of DM for H1, H2, and H3, respectively. Dietary treatments were fed in a 3×3 factorial arrangement of the 3 silages supplemented with 3 concentrate levels (4, 8, and 12 kg/d) and, additionally, H1 was offered without concentrates and H3 with 16 kg/d, giving a total of 11 diets. Cows, blocked according to parity and calving date, were introduced to the experiment before calving and kept in the experiment until wk 16 of lactation. Silage was offered ad libitum in loose housing and concentrate was available in automatic feed stations. Intake of grass silage when fed as the sole feed was 16.9 kg of DM on average for lactation wk 1 to 16. When H1 was supplemented with 4 or 8 kg of concentrates, silage DM intake did not change, but total DM intake increased to 20.6 and 23.7 kg/d, respectively. Energy-corrected milk (ECM) yield increased from 23.4 kg when H1 was offered without concentrate supplement to 29.1 and 32.8 kg when supplemented with 4 or 8 kg concentrate, respectively. None of the other diets equaled the yield obtained by H1 plus 8 kg of concentrate. Feed intake and yield of cows offered H3 plus 4 kg of concentrates were strongly constrained by high dietary fiber concentration. They consumed 16.5 g of neutral detergent fiber/kg of body weight and spent more time eating silage than cows offered other diets. The highest concentrate level within each silage quality produced similar or lower ECM yield than that with 4 kg less concentrates. The obtained milk yield responses suggest that provision of 8.0, 8.4, and 11.5 kg of concentrates to H1, H2, and H3, respectively, would maximize ECM yield within each silage type. However, H1 may successfully be used with less concentrates, or even without, if future conditions should limit the amount of concentrates available for ruminant production.     

Comparison of grass and legume silages for milk production. 1. Production responses with different levels of concentrate

Silages prepared from pure stands of ryegrass, alfalfa, white clover, and red clover over two successive year were offered to lactating dairy cows in two feeding experiments. Proportional mixtures of all cuts prepared in a yr were used to ensure that the forage treatments were representative of the crop. Additional treatments involved mixtures of grass silage with either white clover silage or red clover silage (50/50, on a DM basis). Silages were prepared in round bales, using a biological inoculant additive, and wilting for up to 48 h. Although the legumes were less suited to silage-making than grass, because of their higher buffering capacity and lower water-soluble carbohydrate content, all silages were well-fermented. A standard concentrate was offered at a flat-rate (8 kg/d in yr 1, and 4 or 8 kg/d in yr 2). All of the legume silages led to higher DM intake and milk yields than for the grass silage, with little effect on milk composition. Intake and production responses to legumes were similar at the two levels of concentrate feeding and with forage mixtures they were intermediate to those for the separate forages. An additional benefit of the clover silages, particularly red clover silage, was the increase in levels of polyunsaturated fatty acids, particularly alpha-linolenic acid, in milk. Legume silages also led to a lower palmitic acid percentage in milk. The efficiency of conversion of feed N into milk N declined with increasing levels of legume silage. White clover silage led to a higher N-use efficiency when the effect of N intake level is taken into account.     

Effects of diet and storage on fatty acid profile,micronutrients and quality of muscle from German Simmental bulls

This study evaluated the effect of diet on fatty acid profile, vitamins, trace elements, lipid peroxidation, and quality of longissimus muscle of German Simmental bulls. The effect of storage on fatty acid profile and vitamins was also included. A control group was fed concentrate including soybean, and maize silage/grass silage. Treatment group I (unrestricted) was fed concentrate including rapeseed, and grass silage. Treatment group II (restricted) was fed like treatment group I with a feed restriction period. The treatment diet was not effective to give similar daily live weight gain to the control diet, but it was successful in improving beef fatty acid composition without affecting tenderness and colour (under unrestricted conditions). There were no differences in vitamins and cooking loss, but selenium decreased in treatment groups. Stimulated lipid peroxidation, in samples taken immediately post-mortem, was higher in treatment groups. Polyunsaturated fatty acids decreased, saturated fatty acids and intramuscular fat increased after 14 days of storage while vitamins had no significant reduction.     

Effects of feeding intensity and time on feed on performance, carcass characteristics and meat quality of Simmental bulls

Seventy two Simmental bulls, weighing 489 kg and approximately 15 months old fed extensively or intensively on maize silage and concentrate mixture for 100 or 138 days, were divided into four groups to assess the effect of time on feed and feeding intensity on the performance, carcass and meat quality traits. Bulls intensively fed for 138 days before slaughter had higher final body weight (673.7 kg) compared with the other three groups (610.6 kg, as overall mean). Intensive feeding significantly increased the average daily gain (1371 g/day) and improved the feed efficiency (6.95 kg DM/kg gain) compared with extensive feeding (943 g/day and 7.97 kg DM/kg gain). No significant differences were detected by time on feed. Hot carcass and kidney fat weights were significantly higher for intensively fed bulls compared with extensive ones. Dressing percentage significantly increased for 138 day groups compared with 100 day groups. Carcass conformation and fatness scores significantly improved by intensive feeding. L and b(*) values were not affected by time on feed or feeding intensity. Slaughtering after 138 days on feed significantly elevated the meat redness value (a(*)). Intensive feeding significantly decreased moisture and increased fat content of the longissimus dorsi muscle. Shear force, collagen content, juiciness, flavour and sarcomere length did not differ by time on feed or feeding intensity, while inconsistent effects were observed on tenderness and solubility of collagen.     

The effect of by-product inclusion and concentrate feeding rate on milk production and composition,pasture dry matter intake,and nitrogen excretion of mid-late lactation spring-calving cows grazing a perennial ryegrass-based pasture

Interest is growing in the use of by-products as economical sources of nutrients that complement grazed grass, particularly at times when grass supply is insufficient to meet the nutritional demands of lactating dairy cattle. The objective of this research was to assess the effect of the amount of by-product inclusion and concentrate feeding rate on pasture dry matter intake, milk production and composition, and N excretion from spring-calving cows grazing summer pasture during mid-late lactation. Forty-eight Holstein Friesian dairy cows were randomly assigned to 1 of 4 dietary treatments in a 2 × 2 factorial design. Cows were grazed in one group on a perennial ryegrass-based sward, with pelleted concentrates offered twice daily during milking over a 63-d experimental period. The dietary treatments were 3 kg of concentrate containing 35% by-products; 6 kg of concentrate containing 35% by-products; 3 kg of concentrate containing 95% by-products; and 6 kg of concentrate containing 95% by-products on a fresh matter basis. The by-products used were soybean hulls, palm kernel expeller, and maize dried distillers grains with solubles, included in equal proportions on a dry matter basis. Pasture dry matter intake (14.5 kg/d) was not affected by the amount of by-product inclusion or feeding rate. By-product inclusion had no effect on milk yield (27.1 kg/d) or milk solids (MS) yield (2.0 kg/d). Cows offered 6 kg of concentrate had a greater milk (+1.6 kg/d) and MS (+0.13 kg/d) yield, consumed more N (+0.08 kg/d), and excreted a lower proportion of N in the milk (0.25 vs. 0.27) and feces (0.39 vs. 0.41) and a higher proportion in the urine (0.39 vs. 0.32) compared with cows offered 3 kg of by-product-based concentrate. In conclusion, by-products can be included at up to 95% of the concentrate fed to cows grazing pasture without affecting pasture dry matter intake, milk production or composition, or N excretion. Cows offered 6 kg of concentrates produced more milk and MS than cows offered 3 kg but had higher urinary N excretion. Economics of this yield response will depend on milk and concentrate prices.     

Effects of supplementation of dairy cattle with fish oil on silage intake, milk yield and milk composition

The effects of level of fish oil inclusion in the diet on grass silage intake, and milk yield and composition of dairy cows offered either 5 or 10 kg concentrates/d were evaluated in a ten treatment, partly balanced, changeover design experiment involving 50 cows in early lactation. Concentrates were prepared to provide 0, 150, 300 or 450 g fish oil/cow per d or 300 g fish oil/cow per d from a premix when each animal was offered 5 kg/d. The fish oil was predominantly from herring and mackerel caught in the North Atlantic while the fish oil premix was obtained from a commercial source and used palm kernel expeller as a carrier. Increasing fish oil supplementation decreased silage dry matter intake and the concentrations of milk fat and protein, and increased milk yield and diet digestibility. There were significant interactions between concentrate feed level and level of fish oil for silage intake and milk yield. Other than for the concentrations of milk fat and protein, and 20:4n-6 fatty acids, the source of fish oil did not affect forage intake or animal performance. Fish oil supplementation also decreased the concentrations of milk protein by 0.9 g/kg for each 100 g increase in fish oil supplementation, the depression being similar at each level of concentrate feeding. Supplementing the feed of dairy cows with 450 g fish oil/cow per d decreased the concentration of milk fat by 15 g/kg. This study also showed that feeding dairy cattle with fish oil is an efficient method of increasing eicosapentaenoic acid in the human diet through transfer into milk.     

Selection of muscles as indicators of tenderness after seven days of ageing

The selection of a muscle that could be used as an index muscle for beef tenderness was performed using nine commercially important muscles. A total of 50 bulls, Charolais × Alentejano (n = 9), Simmental × Alentejano (n = 9) and Alentejano (n = 32), were slaughtered at two different commercial live weights: crossbred animals (sample A) between 500 and 600 kg (carcass weight between 310 and 370 kg) and purebred Alentejano (sample B) between 350 and 450 kg (carcass weight between 185 and 295 kg). Slaughter ages varied between 16 and 24 months in both groups. The shear force of nine muscles (Mm. biceps femoris, gastrocnemius, longissimus thoracis, longissimus lumborum, quadriceps femoris, semimembranosus, semitendinosus, supraspinatus and triceps brachii caput longum) was assessed seven days post-mortem. In both samples, the comparison between different muscle means and the combined mean of all muscles and the respective correlations showed that the Mm. biceps femoris and semimembranosus could be used as index muscles. However, the biceps femoris is preferred, because it showed greater stability in terms of the coefficient of variation.     

Dietary tea reduces the iron content of beef

We hypothesized that the lightness of Japanese beef was related to the concentration of heme iron. In Experiment 1, six Japanese Black heifers were allotted randomly to one of three treatment groups: a basal concentrate ration (40% flaked corn) or the same diet and either 2 kg/d wheat bran or 0.5 kg/d green tea. After feeding the diets for 174 d, the cattle were slaughtered and the M. longissimus thoracis, M. semimembranosus, and M. gluteus medius were sampled for meat color, iron, and lipid content. The iron content of the M. semimembranosus from the tea-fed cattle was lower than in M. semimembranosus from the control cattle, and a* (redness) and √(a^*2+b^*2) (saturation) values were lower in M. semimembranosus from bran- and tea-fed cattle than in control cattle. Treatment main effects (across muscles) indicated that inclusion of tea in the diet increased intramuscular lipid and reduced the muscle iron content. There was a significant negative correlation (r²=0.79) between muscle iron content and L^* value (lightness). For Experiment 2, the effect of beef breed type on meat color and iron content of M. longissimus thoracis was investigated using stored meat samples from six breeds from a previous fattening experiment done under a high nutritional plane. Muscle iron content was significantly lower in Japanese Black cattle than in Japanese Black × Holstein or Japanese Black × Japanese Black/Holstein. There was no relationship between muscle iron content and intramuscular lipid content (r²=0.001). In Experiment 3, samples of M. longissimus dorsi were obtained from 17 Wagyu crossbred and 3 Angus crossbred cattle fed a corn concentrate diet in the USA for 148 d. Iron content of the M. longissimus thoracis from Japanese Black and Japanese Brown × Holstein cattle fattened in Japan was significantly less than the iron content of M. longissimus dorsi from cattle raised in the USA. Overall, the data indicate that it is possible to lower muscle iron, and lighten muscle color, by feeding green tea to Japanese cattle; also, there may be a genetic basis for the lower iron, and lighter color, of beef produced in Japan.     

Effects of level of concentrate feeding during the second gestation of Holstein-Friesian dairy cows. 2. Nitrogen balance and plasma metabolites

We offered 43 Holstein-Freisian dairy heifers that calved for the first time at either 2 or 3 yr of age ad libitum access to ryegrass silage and a standard concentrate allowance of either 2 or 7 kg/d from the middle to the end of their first lactation. All animals were given the same relatively poor quality dry period diet of a mixture of ryegrass silage and barley straw (63:37 dry matter basis) from 6 wk before their predicted second-calving date. Following their second calving, all animals received access to the same ration of ad libitum grass silage and concentrates at a rate of 8 kg/d to 120 d of lactation and 5 kg/d thereafter until the end of the experimental recording at about 150 d of lactation. Nitrogen balance was significantly higher at the end of the first lactation for animals that were given the higher concentrate allowance and tended to be higher for older animals. There was no effect of age or residual effect of concentrate allowance on N balance during the dry period or during the second lactation. Labile body protein reserves, as estimated by the depth of the muscle Longissimus dorsi (which was significantly correlated with body condition score), were similar for all animals during the dry period, but younger animals previously offered the lower concentrate allowance did not lose L. dorsi depth early in the second lactation as did other animals. Arterial plasma concentrations of amino acids Phe, Trp, and Leu were significantly higher in younger animals at wk 8 of the second lactation, and Gly was significantly lower, although mammary blood flow, arteriovenous differences, and rates of uptake of the AA measured were unaffected by treatment. It is concluded that differences in second-lactation milk yield were not mediated through the availability of labile body protein or the supply of nutrients to the mammary gland.