Sensory evaluation and its relationship to physical meat quality attributes of beef from Nguni and Bonsmara steers raised on natural pasture

The current study compared sensory characteristics and their relationships with physical meat characteristics of beef from Nguni and Bonsmara steers. Nguni beef was more (P < 0.05) tender than Bonsmara beef after ageing for 2 and 21 days, and had higher (P < 0.05) intramuscular fat (IMF; 1.12%) than Bonsmara beef (1.07%). Nguni beef had higher (P < 0.05) sensory scores than Bonsmara beef after ageing for 2 days. There were no (P > 0.05) relationships between IMF and sensory characteristics. Aroma intensity, impression on juiciness and tenderness-related scores were affected (P < 0.05) by pH. There were significant (P < 0.05) correlations between most physical meat characteristics and sensory characteristics. Nguni beef had better sensory scores than Bonsmara beef for beef aged for 2 days. While most physical meat characteristics were correlated to sensory scores, all sensory scores were not significantly correlated to IMF.     

Tick susceptibility and its effects on growth performance and carcass characteristics of Nguni, Bonsmara and Angus steers raised on natural pasture

The objective of the current study was to compare tick loads, growth and carcass characteristics of dipped and non-dipped Nguni, Bonsmara and Angus steers raised on natural pasture. One hundred 7-month-old castrated weaners were kept at the University of Fort Hare Farm for 12 months. There were 30 weaners each of Angus and Bonsmara, and 40 weaners of the Nguni breed. Half the Bonsmara, Angus and 14 Nguni weaners were dipped every fortnight. The rest were not dipped. Monthly weights and tick counts under the tail, on scrotum, belly, sternum and ears of the steers were recorded. The dipped Nguni steers had lowest (P < 0.05) tick counts, and the non-dipped Angus steers had the highest (P < 0.05) tick counts. There were more ticks (P < 0.05) during the warm wet season than during the cool dry season. Ears had the highest (P < 0.05) tick infestation. Average daily gain (ADG) was similar (P > 0.05) among the three breeds. The non-dipped Bonsmara steers had the heaviest (P < 0.05) carcasses (142 ± 5.4) while the non-dipped Nguni steers had the lightest (P < 0.05) carcasses (111 ± 4.5 kg). The non-dipped Bonsmara had the highest (P < 0.05) eye muscle area (3996 ± 120.8 mm2) while the non-dipped Angus had the smallest (P < 0.05) eye muscle area (3291 ± 210.6 mm2). The non-dipped Bonsmara also had the highest (P < 0.05) dressing percentage (53.8 ± 1.01) while the non-dipped Nguni had the lowest (P < 0.05) dressing percentage (50.3 ± 0.84). The current study has shown that while the non-dipped steers had higher (P < 0.05) tick loads than the dipped steers, their growth and carcass characteristics were similar (P > 0.05). The study has also shown that, despite being a small-framed breed, the Nguni steers had similar (P > 0.05) ADG to the large-framed Bonsmara and Angus steers. Therefore, the Nguni cattle have the potential to produce organic beef. However, a reasonable assessment of organic beef production potential of the Nguni requires an evaluation of its meat quality traits under natural pasture.     

Variation in meat quality characteristics between Sanga (Bos taurus africanus) and Sanga-derived cattle breeds and between Sanga and Brahman (Bos indicus)

Cattle breeds indigenous to Africa (Sanga) compare favourably to Bos indicus breeds with regard to adaptation to harsh environments. This study compared the meat quality of three Sanga breeds (Nguni, Tuli and Drakensberger), a Sanga-related breed (Bonsmara) and a B. indicus breed (Brahman) and supported these results with biochemical and histological measurements on the M. longissimus lumborum. Twelve young grain-fed steers of each breed were slaughtered and carcasses were electrically stimulated. All Sanga (and related) breeds, with the exception of the Tuli, had lower Warner-Bratzler shear force (SF) values at 2 and 21 days post mortem compared with the BR (P < 0.05). Measurements related to the calcium-dependent protease system and myofibrillar fragmentation explained the bulk of the variation among breeds, whereas variation in fibre type, sarcomere length and connective tissue properties gave less convincing support. With the exception of the Tuli, Sanga and Sanga-related breeds produced more tender (according to SF) meat than BR, mainly due to favourable calpain-to-calpastatin ratios. Small differences in colour, drip loss and cooking properties were found among breeds (P < 0.05).     

Effect of α-tocopherol tissue levels on beef quality

To evaluate meat quality of beef with different α-tocopherol tissue levels, 55 feedlot steers were fed a barley-based finisher diet with four vitamin E supplementation levels (0, 350, 700 and 1400 IU DL-α-tocopheryl acetate/animal per day) for 120 days. Although the increase in oxidation levels overtime was much smaller (P < 0.001) in the high-medium and high groups, α-tocopherol tissue levels did not affect (P > 0.05) pH, proximate analysis, drip and cooking losses, and shear force of steaks. No effect of α-tocopherol tissue levels was found in retail evaluation of steaks after a short ageing time of 6 days, but with 21 days of ageing, a delay in formation of metmyoglobin (P = 0.008) was observed in steaks with higher tissue levels of α-tocopherol. Similar results were found for ground beef (25% fat) prepared from 6-day aged meat. Thus, higher α-tocopherol tissue levels protect ground beef and long-aged steaks from discolouration and lipid oxidation.     

Effect of wheat dried distillers grains and enzyme supplementation on growth rates,feed conversion ratio and beef fatty acid profile in feedlot steers

The objectives of this study were to determine: (1) the effect of wheat dried distillers grain with solubles (DDGS) inclusion, and (2) dietary feed enzyme (FE; Econase XT) supplementation in a finishing diet containing wheat DDGS on fatty acid profile of the pars costalis diaphragmatis muscle of beef cattle. A total of 160 crossbred yearling steers with initial BW of 495±38 kg were blocked by BW and randomized into 16 pens (10 head/pen). The pens were randomly assigned to one of the four treatments: (1) control (CON; 10% barley silage and 90% barley grain-based concentrate, dry matter (DM) basis); (2) diet containing 30% wheat DDGS in place of barley grain without FE (WDG); (3) WDG diet supplemented with low FE (WDGL; 1 ml FE/kg DM); and (4) WDG diet supplemented with high FE (2 ml FE/kg DM). The pars costalis diaphragmatis muscle samples were collected from cattle at slaughter at the end of the finishing period (120 days) with a targeted live weight of 650 kg. No differences in organic matter intake, final BW and average daily gain were observed among treatments. However, steers fed WDG had greater (P<0.01) feed conversion ratio than those fed CON, and increasing FE application in wheat DDGS-based diets tended (P<0.10) to linearly decrease feed conversion ratio. In assessing the effects of including WDG diets without FE, concentration of total polyunsaturated fatty acids (PUFA) in muscle tended to be greater (P<0.10) for steers fed WDG than steers fed CON. In addition, inclusion of wheat DDGS into the diet increased (P<0.05) concentration of CLA and vaccenic acid (VA) in muscle and also resulted in a higher (P<0.05) ratio of n-6/n-3 PUFA compared with that from steers fed CON diet. Increasing FE application in wheat DDGS-based diets did not modify the concentrations of individual or total fatty acids. These results suggest that inclusion of wheat DDGS in finishing diets may improve fatty acid profile of beef muscle which could benefit human health.     

Stability,fatty acid composition and sensory properties of the M. Longissimus muscle from beef steers grazing either chicory/ryegrass or ryegrass

Research has shown both production and health benefits for the use of chicory (Cichorium intybus) within ruminant diets. Despite this, little was known about the effects of this forage, containing differing fatty acid profiles and secondary plant compounds compared with ryegrass, on beef stability, fatty acid composition or sensory properties. An experiment was conducted to investigate whether the inclusion of chicory in the diet of grazing beef steers would alter these three properties in the M. Longissimus muscle when compared with beef steers grazing perennial ryegrass (Lolium perenne). Triplicate 2 ha plots were established with a chicory (cv. Puna II)/perennial ryegrass mix or a perennial ryegrass control. A core group of 36 Belgian Blue – cross steers were used within a 2-year beef finishing experiment (n=6/replicate plot). In the 2^nd grazing year, steers were slaughtered as they reached a target fat class of 3. Muscle pH was checked 2 and 48 h post-slaughter. A section of the hindloin joint containing the M. Longissimus lumborum muscle was removed and a 20 mm-thick steak was cut and muscle samples were taken for analysis of vitamin E and fatty acid analysis. The remaining section of the loin was vacuum packed in modified atmosphere packs and subjected to simulated retail display. A section of the conditioned loin was used for sensory analysis. Data on pH, vitamin E concentration and colour stability in a simulated retail display showed there were no effects of including chicory in the diet of grazing beef steers on meat stability. There were also no differences found in the fatty acid composition or the overall eating quality of the steaks from the two treatments. In conclusion, there were no substantive effects of including chicory in the swards of grazing beef cattle on meat stability, fatty acid composition or sensory properties of the M. Longissimus muscle when compared with beef steers grazing ryegrass-only swards.     

Effects of whole linseed supplementation and treatment duration on fatty acid profile and endogenous bioactive compounds of beef muscle

Diet supplementation with oilseeds is known to improve the fatty acid profile of meat, but few studies have been carried out to determine the time required for the incorporation of a significant quantity of n-3 polyunsaturated fatty acids (PUFA) into meat from steers. Therefore, the present study aimed to assess the effects of linseed supplementation and feeding duration on the fatty acid profile, cholesterol and bioactive compounds of bovine meat. In total, 54 Friesian steers were randomly allocated during the finishing period into six experimental treatments following a 2×3 factorial design. The six treatments consisted of two diets, the control diet (CO) with no supplemental fat and the linseed diet (LS) containing 10% whole linseed, fed 40, 75 or 120 days before slaughter. At the end of each finishing period, steers from the CO and LS groups were slaughtered. After 8 days of ageing chemical analysis, the fatty acid profile, cholesterol content and bioactive compounds were determined from the longissimus thoracis muscle. Including linseed in the diet increased the content of monounsaturated fatty acids, CLA and n-3 PUFA, and reduced the proportion of saturated fatty acids and n-6 PUFA. The percentage of myristic fatty acid increased with the duration of feeding, regardless of diet and a decrease in PUFA and n-6 PUFA was observed in the CO and LS diets, respectively. Furthermore, meat from steers fed linseed showed an increased percentage of n-3 PUFA, linolenic acid, and EPA from 40 to 75 days of feeding, whereas vaccenic acid, CLA 9c,11t, and total CLA increased from 40 and 75 days but declined at 120 days. Beef from the linseed group had a higher content of bioactive substances such as creatine, carnosine and anserine than beef from the control group. The duration of feeding significantly affected the creatine concentrations, with an increase in the LS group from 40 to 75 days of feeding. Feeding linseed did not modify the cholesterol content, on average and the lowest cholesterol content was found in meat after 75 days of linseed administration. This study demonstrates that a short-term diet manipulation is sufficient to improve the nutritional properties of meat, including n-3 PUFA and bioactive compounds.     

Effects of cloned-cattle meat on reproductive physiology in rats

The influence of the cloned-cattle meat diets upon reproduction in mammals was rarely studied. This study was performed to analyze the effects of the diets containing cloned-cattle (Korean native beef, Hanwoo) meat on the reproductive physiology in rats. The male and female rats were fed with the diets containing 5% or 10% of normal- (N-5 or N-10) or cloned- (C-5 or C-10) cattle meat during test periods. The rats fed with commercial pellets were used as control. Lower food consumption in normal- and cloned-cattle meat diet groups is detected in both male and female rats compared with that of control (P < 0.05, 0.01 and 0.001). No signs of cloned-cattle meat diets on male reproductive parameters are found in all groups, except for lower sperm deformity in C-5 group (P < 0.05) and higher testosterone concentration in C-10 group (P < 0.05), respectively. There are no significant test substance-related differences of Caesarean section and delivery in dams and external examination and physiological development test in neonate compared with control and normal meat groups. Based on these results, it can be postulated that there are no obvious negative effects on the reproductive physiology in rats fed with cloned-cattle meat diets compared to their comparators.     

Daidzein enhances intramuscular fat deposition and improves meat quality in finishing steers

An experiment was conducted to determine the effects of soy isoflavone daidzein on carcass characteristics, fat deposition, meat quality, and blood metabolites in finishing steers. Fourteen crossbred steers were used in a 120-d finishing study. These steers were stratified by weight into groups and randomly allotted by group to one of two dietary treatments: (1) control and (2) daidzein (500 mg/kg concentrate). The steers were fed a 90% concentrate diet. Supplemental daidzein did not affect slaughter weight, hot carcass weight, and dressing percentage, but tended to reduce fat proportion (not including intramuscular fat) in carcass and backfat thickness of steers. The carcass bone proportion was greater in steers fed daidzein diets than those fed control diets. Daidzein supplementation reduced pH at 24 h after slaughtered and moisture content and increased isocitrate dehydrogenase activity, fat content (16.28% and 7.94%), marbling score (5.29 and 3.36), redness (a*), and chroma (C*) values in longissimus muscle relative to control treatment. The concentrations of blood metabolites including glucose, blood urea nitrogen, triglyceride, total cholesterol, non-esterified fatty acid, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) were all lower in steers fed daidzein diets than those fed control diets. Current results suggest that supplemental daidzein can affect lipid metabolism, increase intramuscular fat content and marbling score, and improve meat quality in finishing steers. Daidzein should be a promising feed additive for production of high-quality beef meat.     

Impact of adding nitrate or increasing the lipid content of two contrasting diets on blood methaemoglobin and performance of two breeds of finishing beef steers

Adding nitrate to the diet or increasing the concentration of dietary lipid are effective strategies for reducing enteric methane emissions. This study investigated their effect on health and performance of finishing beef cattle. The experiment was a two×two×three factorial design comprising two breeds (CHX, crossbred Charolais; LU, Luing); two basal diets consisting of (g/kg dry matter (DM), forage to concentrate ratios) 520 : 480 (Mixed) or 84 : 916 (Concentrate); and three treatments: (i) control with rapeseed meal as the main protein source replaced with either (ii) calcium nitrate (18 g nitrate/kg diet DM) or (iii) rapeseed cake (RSC, increasing acid hydrolysed ether extract from 25 to 48 g/kg diet DM). Steers (n=84) were allocated to each of the six basal diet×treatments in equal numbers of each breed with feed offered ad libitum. Blood methaemoglobin (MetHb) concentrations (marker for nitrate poisoning) were monitored throughout the study in steers receiving nitrate. After dietary adaptation over 28 days, individual animal intake, performance and feed efficiency were recorded for a test period of 56 days. Blood MetHb concentrations were low and similar up to 14 g nitrate/kg diet DM but increased when nitrate increased to 18 g nitrate/kg diet DM (P<0.001). An interaction between basal diet and day (P<0.001) indicated that MetHb% was consistently greater in Concentrate – than Mixed-fed steers at 18 g nitrate/kg diet DM. Maximum individual MetHb% was 15.4% (of total Hb), which is lower than considered clinically significant (30%). MetHb concentrations for individual steers remained consistent across time. Concentrate-fed steers were more efficient (lower residual feed intake (RFI) values) than Mixed-fed steers (P<0.01), with lower dry matter intake (DMI) (kg/day) (P<0.001) and similar average daily gain (ADG). CHX steers were more efficient (lower RFI; P<0.01) than LU steers with greater ADG (P<0.01), lower DMI (/kg BW; P<0.01) and lower fat depth (P<0.001). ADG, BW or DMI did not differ across dietary treatments (P>0.05). Neither basal diet nor treatment affected carcass quality (P>0.05), but CHX steers achieved a greater killing out proportion (P<0.001) than LU steers. Thus, adding nitrate to the diet or increasing the level of dietary lipid through the use of cold-pressed RSC, did not adversely affect health or performance of finishing beef steers when used within the diets studied.     

Blood profile and meat quality of Holstein-Friesian steers finished on total mixed ration or flaxseed oil-supplemented pellet mixed with reed canary grass haylage

Holstein-Friesian steer beef production is renowned globally as a secondary product of the milk industry. Grass feeding is a common practice in raising Holstein steers because of its low cost. Furthermore, grass feeding is an alternative way to produce beef with a balanced n-6 to n-3 fatty acids (FAs) ratio. However, the performance and meat quality of Holstein-Friesian cattle is more likely to depend on a high-quality diet. The aim of this study was to observe whether feeding two mixed diets; a corn-based total mixed ration (TMR) with winter ryegrass (Lolium perenne) or flaxseed oil-supplemented pellets with reed canary grass haylage (n-3 mix) provided benefits on carcass weight, meat quality and FA composition compared with cattle fed with reed canary grass (Phalaris arundinacea) haylage alone. In all, 15 21-month-old Holstein-Friesian steers were randomly assigned to three group pens, were allowed free access to water and were fed different experimental diets for 150 days. Blood samples were taken a week before slaughter. Carcass weight and meat quality were evaluated after slaughter. Plasma lipid levels and aspartate aminotransferase (AST), γ-glutamyl transpeptidase (GGT), creatine kinase (CK) and alkaline phosphatase (ALP) activities were determined. Diet did not affect plasma triglyceride levels and GGT activity. Plasma cholesterol levels, including low-density and high-density lipoproteins, were higher in both mixed-diet groups than in the haylae group. The highest activities of plasma AST, CK and ALP were observed in the haylage group, followed by n-3 mix and TMR groups, respectively. Carcass weight was lower in the haylage group than in the other groups and no differences were found between the TMR and n-3 mix groups. Although the n-3 mix-fed and haylage-fed beef provided lower n-6 to n-3 FAs ratio than TMR-fed beef, the roasted beef obtained from the TMR group was more acceptable with better overall meat physicochemical properties and sensory scores. According to daily cost, carcass weight and n-6 to n-3 FAs ratio, the finishing diet containing flaxseed oil-supplemented pellets and reed canary grass haylage at the as-fed ratio of 40 : 60 could be beneficial for the production of n-3-enriched beef.     

Inclusion of sunflower seed and wheat dried distillers’ grains with solubles in a red clover silage-based diet enhances steers performance,meat quality and fatty acid profiles

The current study compared beef production, quality and fatty acid (FA) profiles of yearling steers fed a control diet containing 70 : 30 red clover silage (RCS) : barley-based concentrate, a diet containing 11% sunflower seed (SS) substituted for barley, and diets containing SS with15% or 30% wheat dried distillers’ grain with solubles (DDGS). Additions of DDGS were balanced by reductions in RCS and SS to maintain crude fat levels in diets. A total of two pens of eight animals were fed per diet for an average period of 208 days. Relative to the control diet, feeding the SS diet increased (P<0.05) average daily gain, final live weight and proportions of total n-6 FA, non-conjugated 18:2 biohydrogenation products (i.e. atypical dienes) with the first double bond at carbon 8 or 9 from the carboxyl end, conjugated linoleic acid isomers with the first double bond from carbon 7 to 10 from the carboxyl end, t-18:1 isomers, and reduced (P<0.05) the proportions of total n-3 FA, conjugated linolenic acids, branched-chain FA, odd-chain FA and 16:0. Feeding DDGS-15 and DDGS-30 diets v. the SS diet further increased (P<0.05) average daily gains, final live weight, carcass weight, hot dressing percentage, fat thickness, rib-eye muscle area, and improved instrumental and sensory panel meat tenderness. However, in general feeding DGGS-15 or DDGS-30 diets did not change FA proportions relative to feeding the SS diet. Overall, adding SS to a RCS-based diet enhanced muscle proportions of 18:2n-6 biohydrogenation products, and further substitutions of DDGS in the diet improved beef production, and quality while maintaining proportions of potentially functional bioactive FA including vaccenic and rumenic acids.     

Interaction of dietary zinc and growth implants on weight gain,carcass traits and zinc in tissues of growing beef steers and heifers

In two separate studies, 60 beef heifers (379 kg BW) and 60 beef steers (348 kg BW) were randomly assigned to six treatments in 2×3 factorial arrangements. The treatments were with or without Synovex^® implants combined with either a control diet or diets supplemented with 200 ppm Zn from ZnSO₄ or zinc methionine (Zn-Met). Near the mid-point of the feeding periods, cattle were vaccinated with a modified live virus and subsequent titers and concentrations of immunoglobulin G (IgG) were measured. Liver and blood samples were obtained 1 week prior to the start of the experiments and at intervals during the experiments. In experiment 1, average daily gains of beef heifers were (P<0.05) affected by the interaction of implant and source of dietary Zn. Compared to control and ZnSO₄ treatments, supplementation with Zn-Met increased (P<0.05) the concentration of Zn in serum. Antibody titers and concentrations of IgG in serum were highest (P<0.05) in heifers fed ZnSO₄ compared to heifers fed the control or Zn-Met supplemented diets. The Synovex-H^® implant reduced the concentrations of Zn and Cu in liver. In experiment 2, Synovex-S^® implants improved (P<0.05) weight gains of steers supplemented with 200 ppm dietary Zn from ZnSO₄ compared to non-implanted steers. However, the implant had no effect when Zn-Met was the dietary Zn source. The implant increased (P<0.05) concentrations of Zn in liver of steers supplemented with 200 ppm dietary Zn and reduced Zn in liver of steers fed the control diet. Implanted steers had higher (P<0.05) Cu status and IgG concentrations in serum than non-implanted steers. Steers supplemented with either ZnSO₄ or Zn-Met had greater (P<0.05) concentrations of Zn in liver and plasma than steers fed the control diet. These results indicate both the level and source of Zn supplementation in diets of feedlot cattle affect their response to growth implants.     

Caecal fermentation characteristics, blood composition and growth of rabbits on substitution of soya-bean meal by unconventional high-glucosinolate mustard ( Brassica juncea) meal as protein supplement

Effect of graded levels of high-glucosinolate mustard (Brassica juncea) meal as substitute of soya-bean meal (SBM) in broiler rabbit diets was studied. Forty weaning rabbits of Soviet Chinchilla and White Giant breed were randomly allocated to one of four experimental diets containing mustard meal (MM) 0, 80, 160 and 245 g/kg. The experiment lasted for 8 weeks. MM had 54.8 mg total glucosinolates (TGLSs) per g dry matter (DM). Diets had TGLS 3.8, 8.4 and 11.98 mg/g DM in 80, 160 and 245 g MM diets, respectively. MM-incorporated diets had higher digestible and linearly (P < 0.01) higher metabolisable energy (ME) content. However, the effect on total tract apparent digestibility of DM, and crude protein was quadratic. Average daily gain (ADG) reduced (P < 0.05) linearly with increasing MM levels in diet, still 80 and 160 g MM diets had similar ADG compared to that of SBM diet. Caecum weight reduced linearly (P < 0.05) with increasing MM levels in diet. The pH of caecal content ranged between 5.85 and 6.19, total N between 1.19 and 1.48 (g per 100 g) and total volatile fatty acids between 4.7 and 5.8 mmol per 100 g, and they were not statistically different. NH3-N ranged between 31.2 and 39.0 mg per 100 ml, and reduced linearly (P < 0.05) while trichloroacetic acid-precipitable nitrogen increased linearly (P < 0.01, ranged between 114 and 247 mg per 100 ml) with increasing MM levels in diet. Blood haemoglobin, packed cell volume and lymphocytes were higher (quadratic effects, P < 0.05) on 245 MM diet, whereas white blood cell count reduced linearly (P < 0.01). Serum aspartate aminotransferase increased linearly (P < 0.01) while alanine aminotransferase and alkaline phosphatase activity, protein, erythrocytes sedimentation rate and red blood cell counts were not affected by MM. Serum Cu, Na and K content increased linearly (P < 0.05) with increasing MM levels. Liver Cu concentration showed quadratic (P < 0.05) increase. Rabbits tolerated 8.4 mg TGLS per g diet (160 g MM per kg) during active growth without any apparent effect on health and growth. It is concluded that MM can replace up to 66% SBM protein in rabbit feeding, whereas complete replacement of SBM with MM reduced feed intake and ADG by 23% and 13%, respectively. Further studies are required to confirm these inclusion levels and glucosinolate tolerance of rabbits.     

Comparative effects of feeding citrus pulp and grape pomace on nutrient digestibility and utilization in steers

Feedlot beef production in tropics and subtropics is being limited by shortage of feed ingredients due to prolonged droughts resulting in high prices of cereal grains and reduced profitability. To alleviate feed shortages and increase profitability for the feedlot industry, it is important to explore underutilized non-conventional resources such as fruit by-products. The current study compared the nutrient intake, digestibility and utilization effects of feeding either 150 g/kg of dried citrus pulp (DCP) or grape pomace (DGP) as alternative dietary fibre sources to 7 months-old Angus steers (281 ± 15.7 kg) under feedlot conditions. Twenty-four steers were assigned to three dietary treatments (8 steers/treatment) in a completely randomised design. Each steer was treated as an experimental unit. Steers were adapted to diets for 21 d followed by 7 d of sample collection during which nutrient intake, digestibility, rumen fermentation parameters, nitrogen retention and microbial N supply were determined. All the data were analysed using the GLIMMIX procedures. Overall, steers fed DGP had the greatest dry matter intake (DM), organic matter (OM) crude protein (CP), ash free neutral detergent fibre (aNDFom), ether extract (EE) and starch intake followed by DCP and control (CON) diets (P ≤ .05). Apparent digestibilities of DM, OM and aNDFom were higher (P ≤ .05) for DCP diet compared to DGP and CON diets. Feeding DCP and DGP diets increased ruminal concentrations of total volatile fatty acids, acetate and isovalerate, and acetate to propionate ratio, and reduced propionate concentrations compared to the CON diet (P ≤ .05). The steers fed the CON diet had the greatest urinary excretions of allantoin, uric acid and total purine derivatives followed by those fed the DCP and DGP diets (P ≤ .05). Nitrogen intake, faecal nitrogen (N), N retention and N efficiency utilization were in the order of DGP > DCP > CON diets (P ≤ .05). Overall, feeding DGP as alternative fibre source to wheat bran improved nutrient intake, retention and efficiency of N utilization but reduced apparent nutrient digestibility compared to DCP. Current finding suggests that DGP may be a better fibre substitute for wheat bran in beef diets than DCP.     

A high-beef diet alters protein kinase C isozyme expression in rat colonic mucosa

We recently reported that a red meat (beef) diet relative to a casein-based diet increases protein kinase C (PKC) activity in rat colonic mucosa. The purpose of this study was to further elucidate the effects of a high-beef diet on colonic intracellular signal transduction by analyzing steady-state protein levels of different PKC isozymes as well as activities of the three types of sphingomyelinases. Male Wistar rats (n = 12/group) were fed AIN93G-based diets either high in beef or casein for 4 weeks. Rats fed the beef diet had significantly (P < 0.05) higher cytosolic PKC alpha and lower membrane PKC delta protein levels than rats fed the casein diet. The beef-fed rats also had alterations in subfractions of PKC zeta/lambda so that they had a significantly (P = 0.001) lower level of membrane 70 & 75 kDa fraction and a higher (P = 0.001) level of cytosolic 40 & 43 kDa fraction than rats fed the casein diet. Because protein levels analyzed with a PKC zeta-specific antibody were similar, these differences in PKC zeta/lambda were probably due to changes in PKC lambda expression. PKC beta2 levels did not differ between the dietary groups. Diet had no significant effect on the activity of acid, neutral, or alkaline sphingomyelinase. This study demonstrated that consumption of a high-beef diet is capable of modulating PKC isozyme levels in rat colon, which might be one of the mechanisms whereby red meat affects colon carcinogenesis.     

Effects of replacing grass silage with either maize or whole-crop wheat silages on the performance and meat quality of beef cattle offered two levels of concentrates

A randomised design involving 66 continental cross beef steers (initial live weight 523 kg) was undertaken to evaluate the effects of the inclusion of maize or whole-crop wheat silages in grass silage-based diets on animal performance, carcass composition, and meat quality of beef cattle. Grass silage was offered either as the sole forage or in addition to either maize or whole-crop wheat silages at a ratio of 40:60, on a dry matter (DM) basis, alternative forage: grass silage. For the grass, maize, and whole-crop wheat silages, DM concentrations were 192, 276, and 319 g/kg, ammonia-nitrogen concentrations were 110, 90, and 150 g/kg nitrogen, starch concentrations were not determined, 225, and 209 g/kg DM and in vivo DM digestibilities were 0.69, 0.69, and 0.58; respectively. The forages were offered ad libitum following mixing in a paddle type complete diet mixer wagon once per day, supplemented with either 3 or 5 kg concentrates per steer per day, in two equal feeds, for 92 days. For the grass, grass plus maize and grass plus whole-crop wheat silage-based diets food intakes were 8.38, 9.08, and 9.14 kg DM per day, estimated carcass gains were 514, 602, and 496 g/day and carcass weights were 326, 334, and 325 kg; respectively. Altering the silage component of the diet did not influence carcass composition or meat eating quality. Increasing concentrate feed level tended ( P = 0.09) to increase estimated carcass fat concentration and increased sarcomere length ( P < 0.05), and lean a* ( P < 0.01), b* ( P < 0.05), and chroma ( P < 0.01). There were no significant silage type by concentrate feed level interactions for food intake, steer performance, carcass characteristics or meat eating quality. It is concluded that replacing grass silage with maize silage increased carcass gain, and weight due to higher intakes, and improved utilisation of metabolisable energy. Whilst replacing grass silage with whole-crop wheat silage increased live-weight gain, the reduced dressing proportion resulted in no beneficial effect on carcass gain, probably due to increased food intakes of lower digestible forage increasing gut fill. Meat quality or carcass composition were not altered by the inclusion of maize or whole-crop silages in grass silage based diets.     

Impact of feed efficiency and diet on adaptive variations in the bacterial community in the rumen fluid of cattle

Limited knowledge of the structure and activities of the ruminal bacterial community prevents the understanding of the effect of population dynamics on functional bacterial groups and on host productivity. This study aimed to identify particular bacteria associated with host feed efficiency in steers with differing diets and residual feed intake (RFI) using culture-independent methods: PCR-denaturing gradient gel electrophoresis (DGGE) and quantitative real-time PCR analysis. PCR-DGGE profiles were generated from the ruminal fluid of 55 steers fed a low-energy-density diet and then switched to a high-energy-density diet. Bacterial profile comparisons by multivariate statistical analysis showed a trend only for RFI-related clusters on the high-energy diet. When steers (n = 19) belonging to the same RFI group under both diets were used to identify specific bacterial phylotypes related to feed efficiency traits, correlations were detected between dry matter intake, average daily gain, and copy numbers of the 16S rRNA gene of Succinivibrio sp. in low-RFI (efficient) steers, whereas correlations between Robinsoniella sp. and RFI (P < 0.05) were observed for high-RFI (inefficient) animals. Eubacterium sp. differed significantly (P < 0.05) between RFI groups that were only on the high-energy diet. Our work provides a comprehensive framework to understand how particular bacterial phylotypes contribute to differences in feed efficiency and ultimately influence host productivity, which may either depend on or be independent from diet factors.     

Effect of level of dietary n-3 polyunsaturated fatty acid supplementation on systemic and tissue fatty acid concentrations and on selected reproductive variables in cattle

Reproductively normal crossbred beef heifers were individually offered a diet of barley straw and concentrate supplemented with one of four levels of a fish oil (FO) enriched supplement. Following oestrous cycle synchronisation, blood samples were collected at appropriate intervals for the measurement of progesterone (P(4)), oestradiol (E(2)), fatty acids, insulin-like growth factor 1 (IGF-1) and metabolites. On days 15 and 16 of the cycle, oxytocin was administered intravenously and the prostaglandin F(2alpha) (PGF(2alpha)) response was measured as venous concentrations of 13,14-dihydro-15-keto PGF(2alpha) (PGFM). The heifers were slaughtered on days 17 or 18 of the oestrous cycle and endometrial tissue, rumen fluid and follicular fluid were collected for determination of fatty acid concentrations. In general there was no effect (P>0.05) of diet on plasma P(4) or E(2) concentrations. Increasing FO supplementation increased CL diameter on day 7 post-oestrus (P<0.0001) but had no effect on diameter on day of slaughter (P>0.05). On day 15, PGFM concentration was greater on the highest level of FO supplementation compared to controls (P<0.05), however, there were no differences between other diet comparisons (P>0.05). There was no effect of diet on PGFM concentration on day 16 (P>0.05). There was a strong positive relationship between plasma and uterine endometrial concentrations of both EPA (R(2)=0.86; P<0.0001) and total n-3 PUFA (R(2)=0.77; P<0.0001). IGF-1 concentrations increased on all diets and were greatest at the highest level of n-3 PUFA supplementation (P<0.05).