The role of grasslands in food security and climate change.

BACKGROUND: Grasslands are a major part of the global ecosystem, covering 37 % of the earth's terrestrial area. For a variety of reasons, mostly related to overgrazing and the resulting problems of soil erosion and weed encroachment, many of the world's natural grasslands are in poor condition and showing signs of degradation. This review examines their contribution to global food supply and to combating climate change. SCOPE: Grasslands make a significant contribution to food security through providing part of the feed requirements of ruminants used for meat and milk production. Globally, this is more important in food energy terms than pig meat and poultry meat. Grasslands are considered to have the potential to play a key role in greenhouse gas mitigation, particularly in terms of global carbon storage and further carbon sequestration. It is estimated that grazing land management and pasture improvement (e.g. through managing grazing intensity, improved productivity, etc) have a global technical mitigation potential of almost 1·5 Gt CO(2) equivalent in 2030, with additional mitigation possible from restoration of degraded lands. Milk and meat production from grassland systems in temperate regions has similar emissions of carbon dioxide per kilogram of product as mixed farming systems in temperate regions, and, if carbon sinks in grasslands are taken into account, grassland-based production systems can be as efficient as high-input systems from a greenhouse gas perspective. CONCLUSIONS: Grasslands are important for global food supply, contributing to ruminant milk and meat production. Extra food will need to come from the world's existing agricultural land base (including grasslands) as the total area of agricultural land has remained static since 1991. Ruminants are efficient converters of grass into humanly edible energy and protein and grassland-based food production can produce food with a comparable carbon footprint as mixed systems. Grasslands are a very important store of carbon, and they are continuing to sequester carbon with considerable potential to increase this further. Grassland adaptation to climate change will be variable, with possible increases or decreases in productivity and increases or decreases in soil carbon stores.

Conservation characteristics of wilted perennial ryegrass silage made using biological or chemical additives.

The effects of 7 additive treatments on the fermentation and aerobic stability characteristics of wilted grass silage were studied under laboratory conditions. Treatments included no additive applied (untreated control), ammonium tetraformate at 3 and 6 L/t, homofermentative lactic acid bacteria alone ((ho)LAB), a mixture of Lactobacillus buchneri plus homofermentative lactic acid bacteria ((he+ho)LAB), and an antimicrobial mixture of sodium benzoate, sodium propionate, sodium nitrite, and hexamethylenetetramine at 2.5 and 5 L/t. Additives were compared across 3 consecutive harvests of 2 perennial ryegrass cultivars (AberDart and Fennema) following a 24-h wilt. Silos were opened after at least 100 d of ensilage and aerobic stability was assessed. Season of harvest had a large effect on grass composition at ensiling, producing herbages of relatively low (approximately 145g/kg), medium (approximately 250g/kg), and high (approximately 365g/kg) dry matter (DM) concentrations. Within harvests there were lesser differences between cultivars. The untreated control and (ho)LAB additive produced badly fermented silage from the low-DM herbages and well-fermented silage from the medium- and high-DM herbages. The ammonium tetraformate treatments produced both well-fermented and badly fermented silage from the low-DM herbages depending on cultivar, and consistently well-fermented silage from the medium- and high-DM herbages. The (he+ho)LAB silages had similar or slightly lower standard of fermentation than the untreated and (ho)LAB silages. The antimicrobial mixture produced more silages of lower standard of fermentation than the untreated control and ammonium tetraformate and (ho)LAB additives. All additive treatments, including the untreated control, failed to consistently increase residual water-soluble carbohydrate concentrations at silo opening. Ammonium tetraformate at 6 L/t was the most successful and (he+ho)LAB the least successful additive at increasing residual WSC concentrations. The (ho)LAB silages were generally the least aerobically stable. Silages treated with ammonium tetraformate at 6 L/t were relatively stable under aerobic conditions. The (he+ho)LAB additive and antimicrobial mixture had an inconsistent effect on aerobic stability. Overall, ammonium tetraformate at 6 L/t was the most effective additive evaluated in this study, producing generally well-fermented silage with the highest concentrations of residual WSC and an intermediate to long duration of aerobic stability.

Effect of DL-malic acid supplementation on feed intake, methane emissions, and performance of lactating dairy cows at pasture.

The objective of this study was to determine the effect of dietary dl-malic acid (MA) supplementation on feed intake, methane (CH(4)) emissions, and performance of mid lactation Holstein-Friesian cows at pasture. Twenty-four (6 primiparous and 18 multiparous) mid- to late-lactation cows (206 +/- 65 d in milk) grazing a mixed-species grass sward were blocked on parity, days in milk, and pretrial milk yield, and randomly allocated within block to 1 of 2 dietary treatments offered twice daily at milking in 2 equal portions (6 kg/d in total): a control concentrate (0 g/d of MA) and a concentrate supplemented with MA (480 g/d of MA) over a 6-wk period. Cows were allowed a 3-wk acclimation period followed by a 5-d CH(4) measurement period. Enteric CH(4) emissions were estimated using the sulfur hexafluoride tracer gas technique, and herbage intake was measured using the n-alkane technique. Dietary supplementation with MA did not affect voluntary intake of herbage or total dry matter intake, body weight gain, milk yield, fat-corrected milk yield, or daily CH(4) production. These results suggest that there is little benefit to be gained from the dietary supplementation of dairy cows at pasture with MA at least within the inclusion rates used in this study.

Effect of DL-malic acid supplementation on feed intake, methane emission, and rumen fermentation in beef cattle.

The objective of this study was to determine the effect of dietary concentration of dl-malic acid (MA) on DMI, CH(4) emission, and rumen fermentation in beef cattle. Two Latin square experiments were conducted. In Exp. 1, six beef heifers (19 +/- 1 mo old) were assigned in a duplicated Latin square to 1 of 3 dietary concentrations of MA on a DMI basis (0%, MA-0; 3.75%, MA-3.75; or 7.5%, MA-7.5) over 3 periods. In Exp. 2, four rumen-fistulated steers (48 +/- 1 mo old) were assigned to 1 of 4 dietary concentrations of MA (0%, MA-0; 2.5%, MA-2.5; 5.0%, MA-5.0; or 7.5%, MA-7.5) on a DMI basis, over 4 periods. Both experimental diets consisted of grass silage and pelleted concentrate (containing MA). Silage was fed ad libitum once daily (a.m.), whereas concentrate was fed twice daily (a.m. and p.m.) with the aim of achieving a total DMI of 40:60 silage:concentrate. In both Exp. 1 and 2, experimental periods consisted of 28 d, incorporating a 13-d acclimatization, a 5-d measurement period, and a 10-d washout period. In Exp. 1, enteric CH(4), feed apparent digestibility, and feed intake were measured over the 5-d measurement period. In Exp. 2, rumen fluid was collected on d 16 to 18, immediately before (a.m.) feeding and 2, 4, 6, and 8 h thereafter. Rumen pH was determined and samples were taken for protozoa count, VFA, and ammonia analysis. Enteric CH(4) emissions were estimated by using the sulfur hexafluoride tracer technique and feed apparent digestibility was estimated by using chromic oxide as an external marker for fecal output. In Exp. 1, increasing dietary MA led to a linear decrease in total DMI (P < 0.001) and total daily CH(4) emissions (P < 0.001). Compared with the control diet, the greatest concentration of MA decreased total daily CH(4) emissions by 16%, which corresponded to a 9% reduction per unit of DMI. Similarly, in Exp. 2, inclusion of MA reduced DMI in a linear (P = 0.002) and quadratic (P < 0.001) fashion. Increasing dietary MA led to a linear decrease in molar proportion of acetic (P = 0.004) and butyric acids (P < 0.001) and an increase in propionic acid (P < 0.001). Ruminal pH tended to increase (P = 0.10) with increasing dietary MA. Dietary inclusion of MA led to a linear (P = 0.01) decrease in protozoa numbers. Increasing supplementation with MA decreased CH(4) emissions, but DMI was also decreased, which could have potentially negative effects on animal performance.

Colour of bovine subcutaneous adipose tissue: A review of contributory factors, associations with carcass and meat quality and its potential utility in authentication of dietary history.

The colour of bovine subcutaneous (sc) adipose tissue (carcass fat) depends on the age, gender and breed of cattle. Diet is the most important extrinsic factor but its influence depends on the duration of feeding. Cattle produced under extensive grass-based production systems generally have carcass fat which is more yellow than their intensively-reared, concentrate-fed counterparts and this is caused by carotenoids from green forage. Although yellow carcass fat is negatively regarded in many countries, evidence suggests it may be associated with a healthier fatty acid profile and antioxidant content in beef, synonymous with grass feeding. Nonetheless, management strategies to reduce fat colour of grass-fed cattle are sought after. Current research suggests that yellow colour of this tissue is reduced if pasture-fed cattle are converted to a grain-based diet, which results in accretion of adipose tissue and dilution of carotenoids. Colour changes may depend on the initial yellow colour, the carotene and utilisable energy in the finishing diet, the duration of finishing, the amount of fat accumulated during finishing and the rate of utilisation of carotene from body fat. Differences in nutritional strategies which cause differences in fatty acid composition may be reflected by differences in fat colour and carotenoid concentration. Fat colour and carotenoids are prominent among a panoply of measurements which can aid the authentication of the dietary history and thus to some extent, the origin of beef, although this potential utility is complicated by the simultaneous rather than discrete use of forages and concentrates in real production systems.

Responses of North American and New Zealand strains of Holstein-Friesian dairy cattle to homeostatic challenges during early and mid-lactation.

This study investigated the physiological basis of differences in nutrient partitioning between the North American (NA) and New Zealand (NZ) strains of Holstein-Friesian cattle by determining the responses to homeostatic challenges at two stages of lactation. Glucose tolerance tests, epinephrine challenges and insulin challenges were carried out on consecutive days commencing on day 32 ± 0.48 (mean ± s.e.) of lactation (T1) and again commencing on day 137 ± 2.44 of lactation (T2). The insulin and non-esterified fatty acid (NEFA) responses to glucose infusion did not differ between the strains. The NZ strain had a greater clearance rate (CR) of glucose (2.04% v. 1.66%/min) and tended to have a shorter (34.4 v. 41.1 min) glucose half-life (t½) at T2 when infused with glucose. The NA cows had a greater glucose response to epinephrine infusion across T1 and T2, and tended to have a greater insulin response to epinephrine infusion. Plasma NEFA concentration declined to similar nadir concentrations for both strains at T1 in response to insulin, though from a higher basal concentration in NA cows, resulting in a greater (-2.29 v. -1.38) NEFA area under the response curve for NA cows. Glucose response to insulin varied with time, tending to be greater for NA at T1, but tending to be lower for NA at T2. The results indicated that NA cows had a greater glycogenolytic response to epinephrine, but both strains had similar lipolytic responses. The results also imply that higher basal circulating NEFA concentrations in the NA strain in early lactation were not due to diminished adipose tissue responsiveness to insulin. There were indications that glucose CR was greater in NZ cows in mid-lactation, and may form the basis of increased body tissue accretion during mid- to late-lactation in this strain.

A comparison of energy balance and metabolic profiles of the New Zealand and North American strains of Holstein Friesian dairy cow.

The milk production, energy balance (EB), endocrine and metabolite profiles of 10 New Zealand Holstein Friesian (NZ) cows and 10 North American Holstein Friesian (NA) cows were compared. The NA cows had greater peak milk yields and total lactation milk yields (7387 v. 6208 kg; s.e.d. = 359), lower milk fat and similar protein concentrations compared with the NZ cows. Body weight (BW) was greater for NA cows compared with NZ cows throughout lactation (596 v. 544 kg; s.e.d. = 15.5), while body condition score (BCS) tended to be lower. The NA strain tended to have greater dry matter intake (DMI) (17.2 v. 15.7 kg/day; s.e.d. = 0.78) for week 1 to 20 of lactation, though DMI as a proportion of metabolic BW was similar for both strains. No differences were observed between the strains in the timing and magnitude of the EB nadir, interval to neutral EB, or mean daily EB for week 1 to 20 of lactation. Plasma concentrations of glucose and insulin were greater for NA cows during the transition period (day 14 pre partum to day 28 post partum). Plasma IGF-I concentrations were similar for the strains at this time, but NZ cows had greater plasma IGF-I concentration from day 29 to day 100 of lactation, despite similar calculated EB. In conclusion, the results of this study do not support the premise that the NZ strain has a more favourable metabolic status during the transition period. The results, however, indicate that NZ cows begin to partition nutrients towards body reserves during mid-lactation, whereas NA cows continue to partition nutrients to milk production.

The effect of early-lactation feeding strategy on the lactation performance of spring-calving dairy cows.

The objective of this study was to establish the influence of daily herbage allowance (DHA) and supplementation level offered to spring-calving dairy cows in early lactation on animal performance throughout lactation. Sixty-six Holstein-Friesian dairy cows were randomly assigned to a 6-treatment grazing study. The treatments comprised 3 DHA levels (13, 16, and 19 kg of DM/cow; >4 cm) and 2 concentrate supplementation levels (0 and 4 kg of DM/cow per day). Treatments were imposed from February 21 to May 8 (period 1; P1). During the subsequent 4-wk (period 2; P2), animals were offered a DHA of 20 kg of DM/cow and no concentrate. Subsequently, all animals grazed as a single herd to the end of lactation. Sward quality was homogeneous throughout lactation. A low DHA increased sward utilization (+14%) but reduced milk, solids-corrected milk, protein, and lactose yields compared with a high DHA during P1. Concentrate supplementation significantly increased milk, solids-corrected milk, fat, protein, and lactose yields during P1. The positive effect of concentrate supplementation remained throughout P2. A total concentrate input of 380 kg of DM/cow increased total lactation milk (+432 kg), solids-corrected milk (+416 kg), fat (+18 kg), protein (+15 kg), and lactose (+23 kg) yields. Greater P1 body weights were recorded when a high DHA and concentrate were offered. The P1 treatment had no effect on body condition score throughout lactation. The results indicate that offering a low DHA in early spring does not adversely affect total milk production, body weight, or body condition score, and offering concentrate results in a greater total lactation milk production performance.

Effect of spring grazing date and stocking rate on sward characteristics and dairy cow production during midlactation.

The objective of this study was to investigate the effect of initial spring grazing date and subsequent stocking rate on sward characteristics, grazing behavior, milk yield, and dry matter intake of spring-calving dairy cows during the main grazing season. Sixty-four spring-calving Holstein-Friesian dairy cows (58 +/- 9 d in milk) were balanced and randomly assigned to 1 of 4 grazing treatments (n = 16) between April 12, and July 3, 2004. Two swards, an early-grazed (E) sward and a late-grazed (L) sward had 2 stocking rates, high and medium, imposed across them. Cows grazing the E swards were stocked at 4.5 cows/ha (E4.5) and 5.5 cows/ha (E5.5), whereas cows grazing the L sward were stocked at 5.5 cows/ha (L5.5) and 6.4 cows/ha (L6.4). Sward characteristics, grazing behavior, and grass dry matter intake (GDMI) were investigated during the second (R2) and fourth grazing rotations (R4). Total dry matter yield was greater on L swards in R2. In R2, the E swards had a greater proportion of leaf as well as a lesser stem and dead dry matter yield. During R2, organic matter digestibility and crude protein content were greater on the E sward than the L sward. Pre-and postgrazing heights were greater for the L swards in R2 and R4. In R4, there was a larger leaf allowance on the E swards. Grazing time was greater and ruminating time lesser for animals grazing the E sward in R2. During R4, intake per bite was greater for the E5.5 and E4.5 treatments. Milk and solids-corrected milk yields as well as GDMI were greater for animals grazing the E sward in both R2 and R4. The results of the present study suggest that early grazing initially had a positive effect on sward quality and structure, which resulted in improved grazing behavior characteristics, increased GDMI, and increased milk production. During R4, sward quality and structure were similar between swards; thus, differences in grazing behavior were due to divergent daily herbage allowances. These results suggest that sward structure and quality as well as daily herbage allowance are important factors that influence animal performance and grazing behavior.

Relationships among milk production, energy balance, plasma analytes, and reproduction in Holstein-Friesian cows.

Associations were examined between components and indicators of early lactation energy balance (EB) and measures of fertility in Holstein cows. Milk production, dry matter intake (DMI), body condition score (BCS), and endocrine and metabolite data from 96 cows were analyzed using multivariate logistic regression and survival analysis. Fertility variables investigated were interval to commencement of luteal activity (C-LA), calving to conception interval (CCI), and conception rate to first service (CON1). Mean daily EB, milk protein content, and DMI during the first 28 d in milk were associated positively with CON1. Cows having poorer BCS (< or =2.25) at first service had a lower CON1. Positive associations were identified among EB, milk protein content, DMI, and the likelihood of a shorter interval to C-LA. Cows having greater DMI and a more positive EB had an increased likelihood of a shorter CCI, whereas a lower nadir BCS was associated with an increased likelihood of a longer CCI. Milk yield was not associated with any of the fertility variables investigated. A greater plasma concentration of insulin-like growth factor I (IGF-I) during the first 2 wk of lactation was associated with a greater CON1 and an increased likelihood of a shorter interval to C-LA. In conclusion, we identified DMI as the principal component of EB influencing subsequent fertility. Furthermore, results indicate that milk protein content and plasma IGF-I concentration in early lactation may be useful indicators of reproductive efficiency.

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, beta-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.

Effect of refined soy oil or whole soybeans on intake, methane output, and performance of young bulls.

An experiment was conducted to establish the effects of feeding refined soy oil (RSO) or whole soybeans (WSB) containing soy oil on DMI, animal performance, and enteric methane (CH4) emissions in young bulls. Thirty-six Charolais and Limousin cross-bred, young beef bulls (338 +/- 27 kg of BW, 218 +/- 17 d of age at the beginning of the experiment) were blocked by BW, age, and breed before being assigned in a randomized complete block design to 1 of 3 experimental treatments (n = 12). The experimental period lasted for 103 d, with enteric CH4 output recorded for 2 periods of 5 consecutive days on d 37 to 41 and d 79 to 83. The 3 dietary treatments consisted of a barley/soybean meal-based concentrate with 0 g/d of RSO; oil from WSB as 6% of DMI (WSB treatment); and oil from RSO as 6% of DMI (RSO treatment). Each diet had a 10:90 forage:concentrate ratio, using barley straw as the forage source. Diet affected DMI (P < or = 0.001) and GE intake (P < 0.05 during the CH4 measurement periods), with the WSB treatment producing the lowest values. The addition of WSB decreased ADG (P < 0.05) compared with the RSO treatment. The WSB treatment also decreased (P < 0.05) average daily carcass gain (ADCG). Both the RSO and WSB concentrates decreased (P < 0.05 to P < 0.001) daily enteric CH4 output when expressed in terms of liters per day, liters per kilogram of DMI, percentage of GE intake, liters per kilogram of ADG, and liters per kilogram of ADCG. Diet had no effect (P = 0.557) on ruminal protozoal numbers. The reductions in enteric CH4 were achieved at relatively high oil inclusion levels. Such oil levels have previously been reported to decrease DMI of high-forage diets, although no effect on DMI was noted with the low-forage diets fed in this experiment. This impact on DMI of high-forage diets may limit the range of diets for which this CH4 reduction strategy may be applicable. The inclusion level of WSB in the current experiment (27%) was beyond the palatability threshold of the bulls used and resulted in a marked decline in intake and performance. Therefore, WSB may have a role to play in ruminant diets, but only at a reduced inclusion rate.

Effect of milking frequency and diet on milk production, energy balance, and reproduction in dairy cows.

The objective of this study was to determine the effects of reduced milking frequency and increased dietary energy density in early lactation on milk production, energy balance, and subsequent fertility. Sixty-six spring-calving, multiparous Holstein-Friesian cows were assigned to 1 of 3 treatment groups: once-daily milking on a standard diet (1xST); 3-times daily milking on a standard diet (3xST); and 3-times daily milking on a high-energy diet. Treatments were imposed for the first 28 d of lactation, after which all groups were milked twice daily and fed the standard diet. During the treatment period, the 1xST cows had 19.6% lower milk yield and higher milk fat and milk protein concentrations (15.7 and 10.2%, respectively) compared with 3xST. Dry matter (DM) intake was similar between 1xST and 3xST during the treatment period (12.64 vs. 13.25 kg/ d; SED = 0.82). Daily energy balance was less negative for 1xST compared with 3xST during wk 1 to 3 of lactation [-3.92 vs. -5.30 unité fourragère lait (UFL)/d; SED = 0.65; 1 UFL is equal to the net energy for lactation of 1 kg of standard air-dry barley]. During the treatment period, the cows on the high-energy diet had 17% higher milk yield, higher DM intake (15.5 vs. 13.9 kg/d; SED = 0.71), and similar energy balance (-4.45 vs. -4.35 UFL/d; SED = 0.65) compared to 3xST. Diet had no significant effect on any of the fertility variables measured. The interval to first ovulation was shorter for 1xST than 3xST (18.3d vs. 28.6d; SED = 1.76). In conclusion, once-daily milking in early lactation may promote earlier resumption of ovarian cyclicity, mediated through improved nutritional status.

Effect of refined coconut oil or copra meal on methane output and on intake and performance of beef heifers.

An experiment was conducted to establish the effect of feeding either refined coconut oil (CO) or copra meal containing CO to beef heifers on DMI, animal performance, enteric CH4 emissions, diet digestibility, and the fatty acid profile of the resulting meat. Forty-one Charolais and Limousin crossbred beef heifers (474 +/- 29 kg; 661 +/- 89 d of age) were blocked by BW before being assigned in a randomized complete block design to 1 of 3 experimental treatments (n = 12) or to a pretrial slaughter group (n = 5) used to determine the initial carcass weight. The experimental period lasted for 93 d. Enteric CH4 output was recorded for 2 periods of 5 consecutive days from d 14 to 18 and from d 70 to 74. The 3 dietary treatments were 1) control, a barley/soybean meal-based concentrate with 0 g of CO/ d; 2) RCO, a barley/soybean meal-based concentrate with 250 g of CO/d from refined coconut oil; and 3) CM, a copra meal-based concentrate with 250 g of CO/d from copra meal. Each diet had a 50:50 forage:concentrate using grass silage as the forage source. There was no effect of diet on DMI (P = 0.734) or GE intake (P = 0.486). The addition of RCO increased ADG (P < 0.05) compared with the control treatment. The CM treatment decreased (P < 0.05) average daily carcass gain compared with the RCO treatment only. There was a decrease (P < 0.05) in the digestibility of the DM, OM, CP, and GE fractions of the diet only with the CM treatment. Both the RCO and CM concentrates decreased (P < 0.001) daily enteric CH4 output when expressed in terms of liters per day, liters per kilogram of DMI, percentage of GE intake, liters per kilogram of ADG, and liters per kilogram of average daily carcass gain. The RCO treatment produced the greatest numerical response for all measures. Ruminal protozoa numbers on the RCO treatment were lower (P < 0.05) than on the control treatment. The concentrations of the fatty acid methyl esters, lauric (P < 0.001) and myristic (P < 0.002) acids, were increased in muscle when either of the CCO treatments was compared with the controls, but the differences were of a magnitude unlikely to influence human health status. Although the CM concentrate decreased CH4 comparable with the RCO concentrate, decreased performance resulted in an extended finishing time with implications for lifetime CH4 emissions.

Changes in colour characteristics and pigmentation of subcutaneous adipose tissue and M. longissimus dorsi of heifers fed grass, grass silage or concentrate-based diets.

The objective of this experiment was to determine the effect of dietary composition and duration of feeding on subcutaneous (s.c.) adipose tissue and M. longissimus dorsi (LD) colour and pigment concentrations of heifers. Fifteen heifers were permanently housed and fed a concentrate diet (PH-CON). Fifty-four heifers were grazed on pasture (PAS) for 90d, housed and offered concentrates (PAS-CON), 200g grass silage (GS)/kg dry matter (DM) (PAS-GS20), 500g GS/kgDM (PAS-GS50) or zero-grazed grass (PAS-GRA). To facilitate assessment of the temporal pattern of tissue colour, 3 heifers/treatment were slaughtered at housing (following 7d adjustment to diets) and 28, 56, 91 and 120 days thereafter. Yellowness ('b' value) of s.c. adipose tissue and lightness ('L' value) and redness ('a' value) of LD were recorded 48h post-mortem. ß-Carotene and lutein contents of s.c. adipose tissue and total LD haem pigments were determined. At housing, s.c. adipose tissue 'b' values of the PAS group (mean=13.47) were higher (P<0.01) than those of the PH-CON group (mean=10.35) but there was no difference in ß-carotene or lutein concentrations. The change in s.c. adipose tissue 'b' for each diet following housing was best described by the following equations: PH-CON: y=-0.087 (SE 0.0347) X+0.0005 (SE 0.00029) X(2)+10.06 (SE 0.600), MSE 1.94, R(2) 0.57, P<0.01. PAS-CON: y=-0.102 (SE 0.0286) X+0.0006 (SE 0.00024) X(2)+13.32 (SE 0.598), MSE 2.30, R(2) 0.62, P<0.001. PAS-GS20: y=-0.106 (SE 0.0296) X+0.0008 (SE 0.00025) X(2)+13.10 (SE 0.618), MSE 2.46, R(2) 0.47, P<0.01. PAS-GS50: y=-0.077 (SE 0.0269) X+0.0006 (SE 0.00023) X(2)+13.29 (SE 0.552) MSE 1.95, R(2) 0.38, P<0.05. PAS-GRA: y=-0.018 (SE 0.0079) X+13.77 (SE 0.528), MSE 2.28, R(2) 0.24, P<0.05, where y='b' value, x=days post-housing (d96-d216) and MSE=mean square error. Treatment had a significant effect on s.c. adipose tissue ß-carotene and lutein (both P<0.001) with PAS-GRA and PH-CON tending to have the highest and lowest concentrations, respectively. PH-CON heifers tended (P=0.058) to have lower LD haem pigments and lighter LD than other heifers. It is concluded that, while concentrate feeding led to the greatest decrease in s.c. adipose tissue yellowness relative to PAS-GRA, choice of dietary ingredients and duration of feeding will depend on the stringency of the colour criteria in particular markets.

Manipulating enteric methane emissions and animal performance of late-lactation dairy cows through concentrate supplementation at pasture.

The objective of this study was to determine the potential of increased fiber-based concentrates to reduce methane (CH(4)) production in relation to milk yield from late-lactation dairy cows. The effect of 2 levels of concentrate supplementation (0.87 vs. 5.24 kg on a dry matter basis) on herbage voluntary intake, total dry matter intake, milk yield, milk composition, and CH(4) production were determined by way of a randomized block designed grazing trial using lactating Holstein-Friesian cows (231 +/- 44 d in milk) grazing a mixed-grass sward with a regrowth aged 36 d. Increased concentrate supplementation resulted in a significant increase in total dry matter intake, milk yield, fat-corrected milk (FCM) yield, and daily CH(4) production. However, herbage intake and milk composition were unaffected. Although daily CH(4) production increased with fibrous concentrate use the increase was not as great as that observed for milk yield. The decline in CH(4) production per kilogram of milk was nonsignificant; however, when relating CH(4) production to FCM(FCM at 35 g of fat/kg of milk), a declining trend was identified within increasing concentrate supplementation (19.26 and 16.02 g of CH(4)/kg of FCM). These results suggest that increased fibrous concentrate use at pasture, even at modest levels, could reduce enteric CH(4) production per kilogram of animal product. However, the effectiveness of such a strategy is dependent on the maintenance of production quotas and a subsequent decline in the number of livestock needed to fulfill the specified production level.

Colour stability, under simulated retail display conditions, of M. longissimus dorsi and M. semimembranosus from steers given long-term daily exercise and supplemented with vitamin E.

The objective was to determine if exercise has a negative impact on the colour stability of beef and if dietary vitamin E (VE) supplementation could counteract any negative effect. Steers were not exercised or were walked 4.41km/day for 18 weeks. Within exercise treatment animals consumed, on average, either 450 or 1050IU/day of VE. Muscle α-tocopherol increased (P=0.004) from 2.35 to 3.15µg/g with VE supplementation. Following ageing M. longissimus dorsi (LD) and M. semimembranosus (SM) steaks were packaged under 80%O(2):20%CO(2) and stored at 4°C. The LD of exercised steers was more red and more saturated (both P<0.05) after 0 and 2 days of storage than LD of unexercised steers. While redness of both muscles decreased over the display period, LD retained a higher redness than SM from day 2 to 7 (P<0.05). Colour shelf-life of LD was extended by 0.75 days, to 3.25 days, due to VE supplementation.

Colour of muscle from 18-month-old steers given long-term daily exercise.

Darker beef from pasture-fed compared with grain-fed cattle may result from differences in physical activity rather than differences in nutrition. The objective was to determine if steers that were exercised produced darker meat than non-exercised steers and whether any effect was muscle-related. Exercised steers were walked 4.41 km daily in a single bout, six days per week for 18 weeks at an average speed of 5.2 kmh(-1). All steers were fed grass silage on an ad libitum basis plus 6 kg concentrates. Following slaughter, muscle colour coordinates ('L' (lightness), 'a' (redness) and 'b' (yellowness) values) of M. longissimus dorsi (LD), M. semimembranosus (SM) and M. extensor carpi radialis (ECR) were recorded at 48 h postmortem and redness and yellowness were used to calculate muscle hue ('H') and colour intensity/saturation ('C'). The pH of all muscles was measured at 1.5, 3, 6, 22 and 48 h postmortem and LD samples were recovered (90 min postmortem) for glycolytic potential (GP) assessment. Exercise did not affect muscle lightness, yellowness, hue or colour intensity. However, LD was the darkest (P<0.001) and SM the most saturated (P<0.001) muscle. Exercise affected muscle redness in a muscle-dependent manner (muscle×exercise, P=0.038) whereby ECR became more red with exercise but LD and SM were unaffected. There were muscle×time (P<0.001) and time×exercise (P=0.045) interactions for muscle pH. The ECR muscle had the highest pH at all times. The exercised steers had higher (P<0.05) LD muscle pH than control steers at 3 and 6 h postmortem. Exercise did not affect myoglobin concentration, which was muscle dependent, decreasing in the order: SM (6.72 mg/g)>ECR (6.33 mg/g)>LD (5.48 mg/g), which were all different (P<0.001). Exercise had no effect on GP in LD muscle (111 vs. 99 µmol/g for control and exercised steers, respectively; SED=6.6 µmol/g). It was concluded that although application of exercise did not affect muscle lightness and thus, did not cause 'darker' meat, it did affect muscle redness in a muscle-dependent manner.

Supplementary concentrate type affects nitrogen excretion of grazing dairy cows.

These experiments were designed to investigate nutritional means of reducing urine N excretion by grazing cows. In experiment 1, 36 Holstein-Friesian cows averaging 92 d in milk were fed either 1 or 6 kg of a high protein concentrate or 6 kg of a low protein concentrate. Pasture dry matter (DM) intake was higher for cows fed 1 kg of high protein concentrate (15.4 +/- 0.62 kg/d) than for cows fed 6 kg of low protein concentrate (13.4 +/- 0.55) but not for cows fed 6 kg of high protein concentrate (13.9 +/- 0.96). The reduction in pasture intake per kg of concentrate DM ingested amounted to 0.35 and 0.47 kg of pasture DM for cows fed 6 kg of high protein and 6 kg of low protein concentrate, respectively. Milk yield and milk protein yield were higher for cows fed 6 kg of high protein concentrate than for cows fed 1 kg of high protein concentrate. Cows fed 6 kg of high protein concentrate had the highest levels of N intake, total N excretion, and urine N excretion. The proportion of N excreted in the urine was lowest for cows fed 6 kg of low protein concentrate. Milk N excretion as a proportion of ingested N was higher for cows fed 6 kg of low protein concentrate than for cows fed 6 kg of high protein concentrate but not for cows fed 1 kg of high protein concentrate. In experiment 2, 24 Holstein-Friesian cows averaging 211 d in milk were supplemented with 4 kg of rolled barley or 4.32 kg of NaOH-treated barley. Milk yield and milk protein yield tended to be higher for cows fed rolled barley than for cows fed NaOH-treated barley. There was no difference in N intake, fecal N excretion, urinary N excretion, or milk N output between diets. Milk urea N concentration was lower for cows fed rolled barley. Significant positive linear relationships were found between N intake and fecal N excretion, urine N excretion, and milk N excretion in experiment 1. In experiment 2, the relationships between N intake and fecal N excretion and urine N excretion were curvilinear, with urine N excretion increasing at a decreasing rate, and fecal N excretion increasing at an increasing rate, as N intake increased. The N excreted by dairy cows may be partitioned to fecal N if supplements based on high concentrations of fermentable organic matter and low concentrations of N are fed. Refinement of this nutritional strategy may allow reduced N excretion without reducing animal performance.

Colour of subcutaneous adipose tissue and M. longissimus dorsi of high index dairy and beef×dairy cattle slaughtered at two liveweights as bulls and steers.

The objectives of this study were (a) to compare muscle and adipose tissue colour of male progeny of two strains of high genetic merit Friesian cows (New Zealand [NZF] and Irish [DAF]) with those of beef (Belgian Blue)×dairy (Holstein-Friesian) [BBHF] male progeny; (b) to compare bulls and steers (gender) of these genotypes and (c) to examine the effects of slaughter weight (SW) on these quality traits. Bulls (n=48) and steers (n=48) of the three genotypes were grown to nominal target liveweights of 550 kg (light) and 630 kg (heavy). Adipose tissue from the NZF genotype was more yellow (P<0.05) than from DAF or BBHF, regardless of gender or SW. For longissimus dorsi (LD) pH, bulls and heavy animals had higher pH (P<0.05) than steers or light animals, respectively, while NZF and BBHF bulls had higher pH than steers. LD muscle from the BBHF genotype had lighter colour (P<0.05) and lower haem pigments (P<0.01) than NZF or DAF progeny. There was no difference in muscle `L' value between light bulls and steers but heavy bulls had darker muscle than heavy steers. There was an interaction between genotype, gender and SW for LD redness. Thus, NZF animals were most red when slaughtered as light or heavy bulls, but there were no differences between genotypes slaughtered as light or heavy steers. These data demonstrate differences in colour of beef, especially from progeny of NZF, which produced the most yellow adipose tissue and the most red muscle tissue.