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.     

Effect of concentrate feeding pattern in a grass silage/concentrate beef finishing system on performance, selected carcass and meat quality characteristics

Steers were offered grass silage ad libitum and 6.4 kg concentrates daily for 126 days or silage ad libitum for 35 days, followed by concentrates ad libitum (Experiment 1). Steers were offered grass silage ad libitum and 6 kg concentrates daily for 154 days, concentrates ad libitum or grass silage ad libitum for 112 days followed by concentrates ad libitum (Experiment 2). All treatments received the same total concentrate allowance. In Experiment 1, there was no difference in any measurement of meat quality. In Experiment 2, ad libitum concentrate feeding per se, decreased redness and increased shear force of muscle at 2 days post-mortem. Delaying concentrate feeding decreased fat yellowness, decreased shear force at 7 and 14 days post-mortem and increased muscle redness at 14 days post-mortem. Modifications of the beef production system examined had minor effects on beef quality which are unlikely to be of commercial significance.     

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.     

Effects of breed and a concentrate or grass silage diet on beef quality in cattle of 3 ages. II: Meat stability and flavour

This study examined the effect of breed and diet on meat quality, defined as lipid stability, colour shelf life and sensory quality. Ninety-six steers were used, half Aberdeen Angus (AA) cross and half Holstein-Friesian (HF). They were reared from 6 months of age on a standard concentrate diet or grass silage and slaughtered at 14, 19 or 24 months of age. Breed had small effects on quality with lower lipid stability in muscle of 24 month-old HF (P<0.05). Sensory scores were similar between the breeds, the few differences being in favour of AA. Diet had the biggest effects on meat quality, in all 3 age groups. The grass silage diet produced higher plasma and muscle levels of vitamin E, lower lipid oxidation in loin steaks measured at 4 and 7 days of retail display and better colour stability (saturation) during shelf life in MAP (O(2):CO(2); 75:25) (all P<0.001). The high values for lipid oxidation in the concentrate-fed steers were linked to high muscle PUFA concentrations and low levels of vitamin E.     

Effect of grass silage and concentrate based finishing strategies on cull dairy cow performance, carcass and meat quality characteristics

Sixty-eight spring calving Holstein-Friesian dairy cows on completion of lactation were randomly assigned to one of four dietary treatments. The experiment commenced on 17th December 2005 and was completed on 27th June 2006. Pre-experimental live weight and BCS were 605kg (s.d. 68.9) and 2.7 (s.d 0.28), respectively. The four treatments were: ad-lib grass silage (GS), GS+3kg concentrate (GS+3), GS+6kg concentrate (GS+6) and GS+9kg concentrate (GS+9). All cows were finished to a live weight>620kg and a BCS>3.5. Live animal, carcass and meat quality characteristics were measured. Mean (s.d.) total feed utilized was similar, at 1.5 (0.05) tonnes DM/cow across all treatments. There was a linear (P<0.001) increase in ADG (kg/day) for the first three dietary treatments, GS (0.71), GS+3 (0.91), GS+6 (1.14) with no additional response to the final increment, GS+9 (1.15). As concentrate proportion in the diet increased there was a linear decrease (P<0.001) in days to slaughter. Cows on the GS+9 treatment (84 days) finished on average 12, 25 and 38 days earlier than those on the GS+6, GS+3, and GS treatments. The GS+9 treatment had lower carcass fat yellowness ('b' value) than the GS treatment but the GS+3 and GS+6 treatments did not differ from either GS or GS+9. There was no effect of treatment (P>0.05) on muscle redness ('a' value) following exposure to oxygen. When cull cows are finished to pre-defined slaughter criteria, similar carcass classifications and carcass quality can be achieved with diets ranging from GS to GS+9, however significant difference in physical performance and days to slaughter will result.     

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.     

Fat volatiles tracers of grass feeding in sheep

Volatile compounds were analysed in subcutaneous fat from lambs raised and finished on grass (GG); raised and finished on concentrates (SS); raised on grass and finished on concentrates for a long (GS1) or a short (GS2) period. Whereas 3-methylindole (skatole), a compound that has been described as a good discriminator of grass feeding, was unaffected by the diet (P>0.05), 2,3-octanedione was lower (P<0.01) in the fat from animals that spent a period in stall with a concentrate diet than in those finished on grass. Among the 20 monoterpenes detected, only p-cymene was affected by the treatment, being higher (P<0.05) in the fat from animals raised and finished on grass (GG) than in the other treatments. Eight among the 13 detected sesquiterpenes were affected by the diet treatment. In particular β-caryophyllene, not detected in the fat from animals raised and finished on concentrates (SS group), was at basal levels in the animals raised on pasture and finished for different durations on concentrates (GS1 and GS2 treatments) and was present at high levels in the animals raised and finished on grass (P<0.0005). From a factorial discriminant analysis, four of the 33 terpenes detected discriminated perfectly those animals raised and finished on pasture (GG) from all the other groups (SS, GS1, GS2).     

Effect of pre-slaughter rations of forage and/or concentrates on the composition and quality of retail packaged beef

Continental Limousin and Charolais crossbred steers (n=66) were assigned to one of six diets: (1) high herbage allowance (18 kg grass dry matter), zero concentrate (HH0C), (2) high herbage allowance and 2.5 kg concentrate (HHLC), (3) high herbage allowance and 5 kg concentrate (HHHC), (4) low herbage allowance (6 kg grass DM) and 5 kg concentrate (LHHC), (5) medium herbage allowance (12 kg grass DM) and 2.5 kg concentrate (MHLC) or (6) concentrates ad-libitum+1 kg straw (CON). Colour was assessed in steaks (n=5) chosen at random from each dietary group and held in overwrapped and/or modified atmosphere packaging (MAP) (80 O(2):20 CO(2)) under simulated retail display conditions for 17 days. When the HH0C and the CON groups were compared, there was no significant difference in colour under overwrapped conditions, however under MAP, surface redness was significantly (P<0.01) higher (greatest Hunter "a" values) in the HH0C group. When the other four diets were compared to the HH0C and CON groups, there was no significant difference in colour under both forms of packaging. Lipid oxidation was highest for the dietary group CON compared to all other dietary groups examined. There was no significant difference in vitamin E levels between the six dietary groups, levels ranged from 1.7 to 2.5 μg/g meat.     

Conjugated linoleic acid concentration in M. Longissimus dorsi from heifers offered sunflower oil-based concentrates and conserved forages

Dietary inclusion of polyunsaturated fatty acid (PUFA)-rich plant oils is one approach to improving the fatty acid profile of ruminant meat and meat products from a human health perspective. Whole crop wheat silages represent a possible alternative forage to grass silage for beef production, however, they may adversely impact the fatty acid profile of ruminant muscle since grass silage is rich in C18:3n-3. The first objective of this experiment was to investigate the relationship between an increase in the dietary supply of C18:2n-6 from sunflower oil (SFO) and conjugated linoleic acid (CLA) concentration in the muscle tissue of beef cattle. The second objective was to investigate the effect of the basal forage type on the muscle fatty acid composition and its response to increasing inclusion of SFO. One hundred and five heifers were blocked according to initial bodyweight and assigned to one of seven silage treatments. The silage treatments were: (1) grass silage (GS), (2) whole crop wheat silage with 38% dry matter (DM) (W1), (3) GS and W1 at a ratio of 1:2 (DM basis) (W1GS) (4) GS and W1 at a ratio of 2:1 (DM basis) (GSW1), (5) whole crop wheat silage with 52% DM (W2), (6) GS and W2 at a ratio of 1:2 (DM basis) (W2GS), (7) GS and W2 at a ratio of 2:1 (DM basis) (GSW2). Within each silage treatment, 5 animals were assigned to one of three concentrate rations, differing in the content of SFO. The levels of inclusion of SFO in the concentrate were 0, 55, 110 g/kg concentrate. Inclusion of SFO in the diet led to an increase in the n-6:n-3 fatty acid ratio in muscle. In animals fed grass silage or mixed silages the n-6:n-3 ratio was lower in muscle compared with those fed whole crop wheat silages, with the exception of animals fed 55 g SFO/kg, for which feeding W1GS led to a higher ratio than W1. Other than the n-6:n-3 ratio there were no significant interactions between the effect of type of silage and the level of SFO on the concentration of fatty acids in intramuscular fat. Increasing the inclusion of SFO led to a linear increase in the CLAcis-9,trans-11 and PUFA concentration in intramuscular fat (P<0.001). This study confirmed the potential for modification, and improvement from a human health perspective, of the fatty acid composition of beef muscle by dietary manipulation.     

Effect of grass or concentrate feeding systems on lamb carcass and meat quality

Thirty-two male Ile de France lambs were divided into four equal groups at age 37 days. Two groups were allowed to graze a natural pasture in France each at a different growth rate (grass high and grass low groups). The other two groups were raised in stalls and fed concentrates to achieve the same growth rates (stall high and stall low groups, respectively) as from the grass groups. The animals were slaughtered when they attained 35 kg and their carcass and meat quality were evaluated. Animals from the two high growth rate groups were slaughtered at an average age of 129 days while those from the low growth rate groups were slaughtered at 163 days. Carcasses from stall-fed lambs were heavier than those from grass-fed lambs as the digestive tract percentage was higher in the grass lambs. Carcasses from stall lambs had better muscular conformation score (P <0.05) and were fattier than those from grass-fed animals. Subcutaneous fat was more yellow and harder in grass-fed lambs (P <0.05). Meat from grass-fed lambs was darker (P <0.05) in colour (lower L*) than meat from stall animals up to 24 h of display. Meat from stall fed animals was more tender and juicier than meat from grass-fed animals (P <0.01), as judged by a trained panel of assessors. Typical lamb flavour was higher in stall-fed lambs (P <0.01). Meat from grass-fed animals had more pronounced liver flavour (P <0.05) and less fatty flavour (P <0.01) than stall-fed lambs. Overall the difference in meat quality between the two different growth rates was minimal.     

Comparative evaluation of alternative forages to grass silage in the diet of early lactation dairy cows

Fifty-six autumn-calving Holstein-Friesian cows, blocked on the basis of days in milk (27.6 ± 10.65 d), lactation number (3.1 ± 2.21), and preexperimental milk yield (28.4 ± 6.69 kg) were used to examine the effects of replacing 330 g/kg of dry matter (DM) of first-cut perennial ryegrass silage with either fermented whole-crop wheat (WCW), urea-treated processed WCW, or corn silage on subsequent feed intake, milk production, and efficiency of nitrogen utilization. The DM (g/kg), crude protein (CP, g/kg of DM) and in vitro DM digestibility (g/kg) of the forages were 204, 179, and 762 for grass silage; 389, 90, and 711 for fermented WCW; 795, 141, and 768 for urea-treated processed WCW; and 346, 93, and 783 for corn silage, respectively. Four forage treatments were evaluated as follows: 1) grass silage as the sole forage (GS); 2) a mixture of grass silage and fermented WCW silage, (F-WCW); 3) a mixture of grass silage and urea-treated processed WCW, (UP-WCW); and 4) a mixture of grass silage and corn silage (CS). In all cases, the alternative forages comprised 67% of the forage mix on a DM basis. Isonitrogenous diets were formulated by offering all cows 8 kg of concentrate as fed, formulated to different CP concentrations. Cows were offered these diets from 28 to 104 d in milk. Total DM intake and milk yield were greater on UP-WCW (20.0 and 30.2 kg/d) and CS (18.3 and 33.2 kg/d) than on GS (13.5 and 26.5 kg/d). Although DM intake was greater on F-WCW (17.1 kg/d) than on GS, milk yield was not significantly greater (+2.7 kg/d). Milk protein concentration was greater on F-WCW (30.5 g/kg), UP-WCW (31.3 g/kg), and CS (30.7 g/kg) than on GS (28.5 g/kg). However, there was no difference between treatments in milk fat or lactose concentrations. Body weight change was greater for cows offered GS (−0.27 kg/d) than for those offered UP-WCW (−0.01 kg/d) and CS (+0.05 kg/d) but not compared with those offered F-WCW (−0.06 kg/d). There was no effect of treatment on plasma glucose, nonesterified fatty acids, β-hydroxybutyrate, urea, or total protein at d 64 ± 17.4 and d 92 ± 17.4 postpartum. Efficiency of N utilization was greatest for CS with 0.36 of N intake being recovered in milk compared with 0.28, 0.32, and 0.26 for GS, F-WCW, and UP-WCW, respectively. There was no effect of treatment on milk urea N concentration or the urinary allantoin N to creatinine N ratio. The results of this experiment indicate that corn silage is a more suitable supplementary forage to grass silage than fermented or urea-treated processed WCW, with advantages realized in milk production and more efficient N utilization.     

Growth, carcass and meat characteristics of Karayaka growing rams fed sugar beet pulp, partially substituting for grass hay as forage

Twenty-one growing male Karayaka sheep were divided into three groups of seven at 12 months of age. All groups received a commercial feed (60%) and roughage (40%). One group received grass hay as roughage (control, C), the other two groups received a mixture in which 40 (0.40SBP) or 60% (0.60SBP) sugar beet pulp (SBP) was used in partial replacement of grass hay in the C group during 56 days. Dry matter (DM) intake and DM conversion index (kg DM per kg weight gain) of the C group were higher (P<0.01) than that of the 0.40SBP and 0.60SBP groups. While the 0.60SBP increased (P<0.05) the L* of meat from the Karayaka young rams, the 0.40SBP or 0.60SBP decreased the ultimate pH (P<0.05) and cooking loss (P<0.01) compared to the C group. Means for redness (a*), yellowness (b*), Hue (H*) and Chroma (C*) and sensory characteristics indicated that there were no significant differences between dietary treatments. Inclusion of 60% SBP increased the palmitic (P<0.02) and linoleic (P<0.01) acid contents of the meat, it decreased (P<0.01) stearic, oleic and arachidonic acid contents compared to the C group. The 0.40SBP also increased (P<0.01) the linoleic acid content of the meat, but it decreased (P<0.01) stearic and arachidonic acid contents compared to the control. Although meat from young rams fed 0.60SBP diet had a higher value of lightness and linoleic acid, and a lower value of cooking loss than those from animals fed the C diet, sensory evaluation did not discriminate the meat from young rams fed with control and/or SBP diets. Therefore, grass hay can be replaced by 60% of SBP in the growing diet for Karayaka rams without a reduction in meat quality.     

Food intake, milk production, and tissue changes of Holstein-Friesian and Jersey × Holstein-Friesian dairy cows within a medium-input grazing system and a high-input total confinement system

Although interest in crossbreeding within dairy systems has increased, the role of Jersey crossbred cows within high concentrate input systems has received little attention. This experiment was designed to examine the performance of Holstein-Friesian (HF) and Jersey × Holstein-Friesian (J × HF) cows within a high concentrate input total confinement system (CON) and a medium concentrate input grazing system (GRZ). Eighty spring-calving dairy cows were used in a 2 (cow genotype) × 2 (milk production system) factorial design experiment. The experiment commenced when cows calved and encompassed a full lactation. With GRZ, cows were offered diets containing grass silage and concentrates [70:30 dry matter (DM) ratio] until turnout, grazed grass plus 1.0 kg of concentrate/day during a 199-d grazing period, and grass silage and concentrates (75:25 DM ratio) following rehousing and until drying-off. With CON, cows were confined throughout the lactation and offered diets containing grass silage and concentrates (DM ratio; 40:60, 50:50, 40:40, and 75:25 during d 1 to 100, 101 to 200, 201 to 250, and 251 until drying-off, respectively). Full-lactation concentrate DM intakes were 791 and 2,905 kg/cow for systems GRZ and CON, respectively. Although HF cows had a higher lactation milk yield than J × HF cows, the latter produced milk with a higher fat and protein content, so that solids-corrected milk yield (SCM) was unaffected by genotype. Somatic cell score was higher with the J × HF cows. Throughout lactation, HF cows were on average 37 kg heavier than J × HF cows, whereas the J × HF cows had a higher body condition score. Within each system, food intake did not differ between genotypes, whereas full-lactation yields of milk, fat plus protein, and SCM were higher with CON than with GRZ. A significant genotype × environment interaction was observed for milk yield, and a trend was found for an interaction with SCM. Crossbred cows on CON gained more body condition than HF cows, and overall pregnancy rate was unaffected by either genotype or management system. In summary, milk and SCM yields were higher with CON than with GRZ, whereas genotype had no effect on SCM. However, HF cows exhibited a greater milk yield response and a trend toward a greater SCM yield response with increasing concentrate levels compared with the crossbred cows.     

Assessment of dietary ratios of red clover and grass silages on milk production and milk quality in dairy cows

Twenty-four multiparous Holstein-Friesian dairy cows were used in a replicated 4 × 4 Latin square changeover design experiment to test the effects of changing from ryegrass (Lolium perenne) silage to red clover (Trifolium pratense) silage in graded proportions on feed intakes, milk production, milk organoleptic qualities, and whole-body nitrogen partitioning. Four dietary treatments, comprising ad libitum access to 1 of 4 forage mixtures plus a standard allowance of 4 kg/d dairy concentrates, were offered. The 4 forage mixtures were, on a dry matter (DM) basis: 1) 100% grass silage, 2) 66% grass silage: 34% red clover silage, 3) 34% grass silage: 66% red clover silage, and 4) 100% red clover silage. In each of 4 experimental periods, there were 21 d for adaptation to diets and 7 d for measurements. There was an increase in both DM intakes and milk yields as the proportion of red clover in the diet increased. However, the increase in milk yield was not as great as the increase in DM intake, so that the efficiency of milk production, in terms of yield (kg) of milk per kg of DM intake, decreased. The concentrations of protein, milk fat, and the shorter chain saturated fatty acids decreased, whereas C18 polyunsaturated fatty acids (PUFA) and long-chain PUFA (C20+) increased as the proportion of red clover in the diet increased. There was little effect of dietary treatment on the organoleptic qualities of milk as assessed by taste panel analysis. There were no effects on the aroma of milk, on aftertaste, or overall liking of the milk. Milk was thicker and creamier in color when cows were fed grass silage compared with red clover silage. The flavor of milk was largely unaffected by dietary treatment. In conclusion, increasing the proportion of red clover in the diet of dairy cows increased feed intakes and milk yields, decreased the concentration of fat and protein in milk, increased PUFA for healthiness, and had little effect on milk organoleptic characteristics.     

Plasma growth hormone and insulin during early lactation in cows fed silage based diets.

Peripheral plasma insulin, growth hormone, and blood glucose were determined in 24 dairy cows during early lactation. Blood samples were obtained at 4-day intervals during the first 56 days of experimental lactations 1 and 3 of a 3-lactation experiment. The cows were divided equally among three groups and fed one of the following forage rations for three consecutive lactations: corn silage (18.2 kg/day) plus alfalfa-timothy hay ad libitum; corn silage (18.2 kg/day) plus alfalfa-timothy silage ad libitum; or corn silage ad libitum. These diets were continued throughout the intervening dry periods except in the latter group where corn silage intake was limited if individual animals exhibited excessive body weight gain. Four animals in each group received prepartum supplemental concentrates. The remaining four animals received no prepartum concentrate supplementation. Following parturition, concentrates were fed in increasing amounts to a maximum of 14.6 kg/day during the first 56 days of lactation. Plasma insulin, growth hormone, and blood glucose were not affected by forage diet or prepartum supplemental concentrate feeding. Plasma insulin and blood glucose increased and plasma growth hormone decreased with time after parturition. These changes were correlated with nutrient intake which increased during the experiment. Changes in plasma insulin and growth hormone are related to metabolic adjustments during early lactation.     

Performance of Holstein and Swedish-Red × Jersey/Holstein crossbred dairy cows within low- and medium-concentrate grassland-based systems

This 2 × 2 factorial design experiment was conducted to compare the performance of spring-calving Holstein dairy cows (HOL, n = 34) with Swedish Red × Jersey/Holstein crossbred (SR × J/HOL, n = 34) dairy cows within low and medium concentrate input grassland-based dairy systems. The experiment commenced when cows calved and encompassed 1 full lactation. Cows were offered diets containing grass silage and concentrates [70:30 dry matter (DM) ratio, and 40:60 DM ratio, for low and medium, respectively] until turnout, grazed grass plus either 1.0 or 4.0 kg of concentrate/d during the grazing period (low and medium, respectively), and grass silage and concentrates (85:15 DM ratio, and 70:30 DM ratio, for low and medium, respectively) from rehousing and until drying off. No significant genotype × system interactions were present for any of the feed intake or full-lactation milk production data examined. Full-lactation concentrate DM intakes were 769 and 1,902 kg/cow for the low and medium systems, respectively, whereas HOL cows had a higher total DM intake than SR × J/HOL cows in early lactation, but not in late lactation. Although HOL cows had a higher lactation milk yield than SR × J/HOL cows, the latter produced milk with a higher fat and protein content, and thus fat plus protein yield was unaffected by genotype. Milk produced by the SR × J/HOL cows had a higher degree of saturation of fatty acids than milk produced by the HOL cows, and the somatic cell score of milk produced by the former was also higher. Throughout the lactation, HOL cows were on average 30 kg heavier than SR × J/HOL cows, whereas the SR × J/HOL cows had a higher body condition score than the HOL cows. Holstein cows had a higher incidence of mastitis and ovarian dysfunction that SR × J/HOL cows.     

Protein nutrition of dairy cows receiving grass silage diets. Effects on silage intake and milk production of postruminal supplements of casein or soya-protein isolate and the effects of intravenous infusions of a mixture of methionine,phenylalanine and tryptophan

Milk production responses to protein supplementation of grass silage diets were investigated in two experiments with dairy cows. In Experiment 1. four cows received a basal diet of grass silage ad libitum plus a barley/soya supplement at 5 kg day^?1. The cows received the following treatments in a 4 × 4 Latin square design with 10-day periods: (1) basal diet, (2) basal diet plus 230 g casein day^?1 infused into the abomasum; (3) basal diet plus 225 g soya protein isolate (SPI) day^?1 into the abomasum; and (4) basal diet plus a dietary addition of 1.2 kg fishmeal-based product (AP) day^?1. All three supplements increased (P < 0.05) the yield of milk and milk protein relative to the basal diet, the values being 16.9. 535:18.8. 610; 19.5, 625; and 18.5 kg day^?1 and 582 g day^?1 for the basal. AP, casein and SPI treatments respectively. Responses to casein were greater (P < 0.05) than to SPI. Changes in the concentrations of amino acids in blood plasma suggested that methionine, tryptophan and phenylalanine were in shortest supply relative to demand, and their potential role as limiting amino acids was investigated in a second experiment. In Experiment 2, four dairy cows were used in a 4 × 4 Latin square design with 10-day periods. The four treatments were (1) a diet of grass silage ad libitum plus 5 kg day^?1 of a barley/soya supplement containing 176 g CP kg^?1 DM (LP); (2) LP plus an intravenous infusion of 5.0 g methionine, 9.1 g phenylalanine and 2.2 g tryptophan day^?1; (3) grass silage ad libitum plus 5 kg day^?1 of a barley/soya supplement containing 334 g CP kg^?1 DM (HP); and (4) HP plus the intravenous infusion of methionine, phenylalanine and tryptophan. The HP treatment produced a higher yield (P < 0.05) of milk protein than the LP treatment (722 vs. 667 g day^?1) but the amino acid infusion had no effect with either treatment. The elimination of methionine, phenylalanine and tryptophan (and, in previous experiments, methionine and lysine) as candidates for limiting amino acids on diets of grass silage plus soya-based supplements questions whether the differences in responses to casein and SPI can be explained in terms of their amino acid compositions. The role of factors such as peplides, producing during digestion, some of which may be biologically active, deserves investigation.     

Forage intake,meal patterns,and milk production of lactating dairy cows fed grass silage or pea-wheat bi-crop silages

This study investigated the feed intake, milk production, and plasma nutrient status in dairy cows fed inter-cropped pea-wheat (bi-crop) silages comprised of contrasting ratios of pea to wheat. Spring peas (cv. Magnus) and wheat (cv. Axona) sown at either high (75:25) or low (25:75) pea inclusion rates were harvested after 13 (Cut 1) or 15 (Cut 2) wk. Eighteen Holstein-Friesian cows between wk 9 and 10 of lactation were used in a cyclical changeover design with three 28-d periods. Cows were fed the bi-crop silages and 6 kg of concentrates or second-cut grass silage supplemented with 6 (GS6) or 9 (GS9) kg/d of concentrates. Forage intakes were higher when bi-crops were fed (10.3 to 11.4 kg dry matter [DM]/d) than when grass silage was fed (8.6 kg DM/d). Total DM intake was similar among cows fed the bi-crop silages and GS9 diets, but intakes for GS6 were at least 1.7 kg DM/d lower. Increasing the pea inclusion rate increased the crude protein (CP) content of the ration, but it did not enhance forage quality or animal performance. The rate of intake of the different forages was similar, so that the higher intakes of bi-crop silages were associated with more time spent at the feedbunk and an increased number of meals. Diet digestibility ranged from 531 to 650 g/kg, and the highest value was given by the Cut 1 bi-crop silage diet. Milk yield tended to be similar for cows fed the Cut 2 bi-crop and GS9 diets, and these values were at least 1.7 kg higher than those for cows fed on other treatments. Generally, the bi-crop diets resulted in higher milk fat contents and lower polyunsaturated fatty acid contents. Milk protein content was highest for cows fed the GS9 diet. Blood metabolite content was unaffected by treatment except for blood urea nitrogen content, which was higher in cows fed the bi-crop silages, reflecting reduced N-use efficiency with these diets. The study showed that pea-wheat bi-crop silages can be used to replace moderate-quality grass silage in dairy cow rations, but their role as alternatives to high-quality forages requires additional investigation.     

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.