Effects of grass pasture and concentrate-based feeding systems for spring-calving dairy cows in early spring on performance during lactation

The effect of offering a total mixed ration of silage and concentrate (proportionately 0·44 silage) system [indoor feeding system (IF)] was compared with grazing at a high daily herbage allowance with a low level of concentrate supplementation [early grazing system (EG)] in early spring on the performance of spring‐calving dairy cows in Ireland. Sixty‐four spring‐calving Holstein–Friesian dairy cows (mean calving date, 2 February) were allocated to one of two systems between 16 February and 4 April 2004. An equal number of primiparous and multiparous cows were assigned to each system. The dairy cows on the IF system were housed for a 7‐week period and offered a diet of 10·9 kg DM cow^?1 d^?1 (s.d. 2·3) of concentrate, the remainder of the diet was 8·6 kg DM cow^?1 d^?1 (s.d. 1·9) of grass silage. The dairy cows on the EG system were offered a mean daily herbage allowance of 15·1 kg DM cow^?1 d^?1 (s.d. 3·7) and were supplemented with 3·0 kg DM cow^?1 d^?1 (s.d. 1·0) of concentrate. There was no difference in milk yield between the two systems but the cows in the EG system had a higher milk protein concentration (2·9 g kg^?1) and a higher milk protein yield than in the IF system. Milk fat concentration was higher for cows in the IF than EG system (3·0 g kg^?1). There was no difference in total daily dry‐matter intake between the systems, measured in week 6 of the study. Mean live weight of the cows in the IF system was greater than in the EG system. The results of the study suggest that a slightly greater performance can be achieved by a system offering a high daily herbage allowance to spring‐calving dairy cows in early lactation compared with a system offering a total mixed ration containing a high proportion of concentrate with grass silage.     

Effect of maize grain and herbage allowance on estimated metabolizable energy intake and animal performance in beef cattle finishing systems

This study investigated the effects of levels of supplementation with maize grain and herbage allowance (HA) on grass herbage and maize intake, animal performance and grazing behaviour in two replicated grazing experiments with Angus beef cattle in Argentina. In Experiment 1, the response to increasing HA (2·5, 5·0 and 7·5 kg DM herbage 100 kg^?1 live weight (LW) d^?1 with and without 0·5 kg DM maize grain 100 kg^?1 LW d^?1) was investigated. In Experiment 2, the responses to level of maize grain offered (0, 0·5 and 1·0 kg DM maize grain 100 kg^?1 LW d^?1) at an HA of 2·5 kg DM herbage 100 kg^?1 LW d^?1 and an HA of 5·0 kg 100 kg^?1 LW d^?1 without maize grain were assessed. In Experiment 2, soyabean meal was added to control the crude protein concentration in the diet. Two methods were used for intake estimations: pre‐ and post‐feeding herbage mass difference, and the use of the n‐alkane and ¹³C technique. The latter predicted most accurately the metabolizable energy requirements calculated from live weights and liveweight gain of beef cattle attained in each treatment in both experiments. Increasing HA significantly increased herbage intake and liveweight gain (P < 0·01), and general quadratic relationships between these variables could be fitted across experiments despite differences in animal and pasture characteristics. Increasing the amount of maize grain offered significantly reduced herbage intake and grazing time, but increased liveweight gain and digestibility of the diet. Substitution rate increased with increasing HA in Experiment 1 but was not affected by level of maize supplementation in Experiment 2. These relationships will aid the development of grazing management models for Argentinean conditions.     

Effects of the proportions of high or medium digestibility grass silage and concentrates in the diet of beef cattle on liveweight gain, carcass composition and fatty acid composition of muscle

Abstract An experiment was carried out over 2 years to evaluate the effects of increasing the proportion of cereal‐based concentrates in diets containing high‐digestibility and conventional medium‐digestibility grass silages on the dry‐matter (DM) intake, liveweight gain and carcass composition of beef cattle, and to examine the effects of grazed grass and the ratio of grass silage:concentrates in the diet on the fatty acid composition of selected muscle tissues. Late‐maturing steers (n = 231) were offered diets based on high‐digestibility (HD) (0·743 digestible organic matter (DOM) in DM) or medium‐digestibility (MD) (0·643 DOM in DM) grass silages supplemented with barley/soyabean meal‐based concentrates. The concentrates constituted 0·20, 0·40, 0·60 and 0·80 of total DM of the diets, which were offered ad libitum (AL). The two diets, which contained 0·80 concentrates, were also offered at 0·80 of AL intake. A further group of fourteen animals were given the medium‐digestibility silage only for 5 months and then grazed perennial ryegrass pastures for a further 5 months (silage/pasture treatment). For the diets containing HD silage and 0·20, 0·40, 0·60 and 0·80 concentrate, and 0·80 concentrate at 0·8 of AL intake, the DM intakes were 9·4, 10·2, 10·4, 10·2 and 8·1 (s.e. 0·16) kg d^?1, respectively, and daily carcass gains were 0·67, 0·78, 0·77, 0·79 and 0·62 (s.e. 0·029) kg d^?1, respectively; for those containing MD silage and 0·20, 0·40, 0·60 and 0·80 concentrate, and 0·80 concentrate at 0·8 of AL, the DM intakes were 8·2, 9·3, 10·1, 10·1 and 8·0 (s.e. 0·16) kg d^?1, respectively, and daily carcass gains were 0·38, 0·48, 0·64, 0·77 and 0·56 (s.e. 0·029) kg d^?1 respectively. Increasing the proportion of concentrates in silage‐based diets decreased the concentration of omega‐3 (ω‐3) polyunsaturated fatty acids (PUFA) (P < 0·001) and increased the concentration of ω‐6 PUFA (P < 0·001) in muscle. Cattle on the silage/pasture treatment had the highest concentration of ω‐3 PUFA in muscle (51 g kg^?1 lipid), this value being over three times that for animals given diets containing MD silage and 0·80 concentrate in the diet. These results demonstrate the potential of HD silage made from perennial ryegrass relative to high concentrate diets. The consumption of pasture‐finished beef could make a significant contribution towards increasing the intake of ω‐3 PUFA in the human diet.     

Long‐term effects on sward composition and animal performance of reducing fertilizer inputs to upland permanent pasture

This study investigated the long‐term effects on sward composition and animal performance of applying different fertilizer regimes to upland permanent pasture. The experiment, which was carried out in 2008, was based on a set of replicated (n = 3) plots that had been established in 1990. The effects of applying (i) N, P, K and lime, (ii) P and K plus lime and (iii) lime only were compared with a treatment that received no nutrient applications. Using a put‐and‐take stocking system, the plots were grazed to a target sward surface height of 4 cm by ewes and lambs from April to early August and by ewes only from August to mid‐October. The long‐term reduction in nutrient inputs had led to decreases in the percentages of both sown and unsown grass species within the sward (P < 0·05), and an increase in the percentage of mosses and litter (P < 0·05), with a corresponding reduction in nutritional value. Although there were no statistically significant treatment‐related differences in lamb growth rates, lower fertilizer inputs were associated with a marked decline in stock carrying capacity and associated overall productivity during both the pre‐ and post‐weaning periods (P < 0·001). The findings highlight the challenges faced when attempting to reconcile production and environmental objectives in upland systems.     

Seasonal patterns of diet composition, herbage intake and digestibility limit the performance of cattle grazing native pasture in the Falkland Islands

The botanical composition, intake and digestibility of the diet consumed by mature lactating and non‐lactating cows grazing a native white grass (Cortaderia pilosa) plant community in the Falkland Islands was measured in four periods between September 1998 and June 1999. Five lactating and five non‐lactating cows were used in the summer, autumn and winter; five non‐lactating cows were used in the spring. Different cows were used in each period. Plant cuticle patterns in the faeces of cattle were used, in conjunction with the patterns of concentrations of n‐alkanes in the faeces, to estimate the botanical composition of the diet and predicted concentrations of C₃₂‐ and C₃₃‐alkanes in the herbage allowed herbage intake and digestibility to be estimated using the n‐alkane technique. White grass, sedges and rushes comprised 0·78, 0·64 and 0·63 of the diet in autumn, winter and spring respectively. Fine grasses, smooth‐stalked meadow grass (Poa pratensis L.), annual meadow grass (Poa annua L.), bent grass (Agrostis capillaris L.), native fescue (Festuca magellanica Lam.), Yorkshire fog (Holcus lanatus L.), wavy hair grass [Deschampsia flexuosa (L) Trin.] and early hair grass (Aira praecox L.), were consumed at the expense of sedges and rushes in summer and this coincided with the period of greatest estimated metabolizable energy and crude protein intakes by cows. Lactating cows suffered substantial liveweight loss during autumn and winter and this reflected the low quality of the diet consumed. Phosphorus intakes were insufficient and there was an estimated deficiency of vitamin D in the winter and early spring in cattle that were grazed with the experimental cows. The nutrient restrictions imposed on cattle by the low quality of native pasture during autumn and winter are likely to impair the reproductive potential of breeding females and methods should be investigated to improve the diet consumed by cows during these critical periods if cattle systems are to become sustainable in the Falkland Islands.     

Effect of early turnout to grass in spring on dairy cow performance

This experiment examined the effects of grazing severity and degree of silage restriction during early turnout of dairy cows to pasture in spring on animal performance. Forty late‐winter‐calving Holstein Friesian dairy cows were allocated to one of five treatments between 7 March and 17 April 1997. The treatments involved early turnout of cows to grass for 2 h per day at two residual sward heights and two silage allowances, plus a control treatment, in a randomized block design. Dairy cows on the control treatment remained indoors throughout the experiment and were offered grass silage ad libitum. Dairy cows on all treatments were also offered 6 kg d^–1 of a concentrate on a flat‐rate basis, split equally between the morning and afternoon milkings. Offering cows access to pasture in early spring for 2 h per day resulted in increases in both milk (P < 0·001) and protein yield (P < 0·01). On average, over all grazing treatments, cows produced an additional 2·6 kg milk per day compared with the control treatment (28·5 vs. 25·9 kg d^–1, s.e.m. 0·43). Furthermore, these increases in milk yield were obtained even when silage was restricted indoors (28·4 vs. 25·9 kg d^–1) and cows grazed down to a residual sward height of 40 mm (28·1 vs. 25·9 kg d^–1). Protein yield was higher (P < 0·01) with dairy cows grazing pasture compared with cows indoors (848 vs. 707 g d^–1, s.e.m. 28·9). Silage intake was significantly (P < 0·001) reduced when cows were turned out to pasture. In conclusion, early turnout of dairy cows to pasture in spring for 2 h per day reduced silage intake and increased milk yield and protein yield relative to those fully housed and offered grass silage with a low level of concentrates.     

The effects of high-concentrate diets and pasture on the concentration of conjugated linoleic acid in beef muscle and subcutaneous fat

Abstract In view of the evidence indicating several potential benefits of high intakes of conjugated linoleic acid (CLA) on human health, an experiment was conducted to examine the effects of the diet of beef cattle on the total CLA concentration in muscle and subcutaneous fat. High‐concentrate [steers consumed 515 g concentrates and 485 g grass silage kg^?1 dry matter (DM) for 8 weeks followed by 887 g concentrates and 113 g grass silage kg^?1 DM for 14 weeks until slaughter] and high‐forage (steers consumed 803 g grass silage and 197 g concentrates kg^?1 for 8 weeks followed by grass silage only for 10 weeks and then grazed perennial ryegrass‐based pasture for 23 weeks until slaughter) treatments were imposed on 48 steers, which were crosses of continental beef breeds (initially 414 kg live weight) The concentrates were based on barley, extracted soyabean meal, molassed sugarbeet pulp and maize meal. The silages were of medium to low digestibility and contained 117–137 g crude protein kg^?1 DM and 83–158 g ammonia‐N kg^?1 total N. The pasture was of high quality and contained 168 g crude protein, 234 g acid‐detergent fibre and 222 g water‐soluble carbohydrate kg^?1 DM. Samples of muscle were taken post slaughter from the m. semimembranosus, m. gluteobiceps, m. longissimus and m. deltoideous muscles, and subcutaneous fat was taken from over the m. longissimus. Concentrations of total CLA in the tissues were for the high‐concentrate and high‐forage treatments, respectively (mg 100 g^?1 fresh tissue), m. gluteobiceps 18 and 47 (s.e. 3·5); m. semimembranosus 9 and 20 (s.e. 1·6); m. longissimus 15 and 35 (s.e. 3·2), m. deltoideous 20 and 59 (s.e. 4·3); subcutaneous fat 584 and 1975 (s.e. 138·7). It is concluded that muscle and subcutaneous fat tissue from grass‐fed cattle contained three times as much CLA as those from concentrate‐fed cattle, and that the consumption of beef from grass‐fed cattle should be effective in increasing the intake of CLA by humans.     

Productivity of beef cattle grazing Brachiaria brizantha cv. Marandu with and without nitrogen fertilizer application or mixed pastures with the legume Desmodium ovalifolium

The use of forage legumes to contribute biologically fixed nitrogen (N) to pastures is an alternative to increase beef cattle production in tropical regions. The objective was to compare the impact of the introduction of a legume with that of N fertilizer application on forage and animal production in Brachiaria pastures. This two-year study assessed three pasture treatments: (1) mixed Marandu palisadegrass (Brachiaria brizantha [syn. Urochloa brizantha] cv. Marandu) and the legume “ovalifolium” (Desmodium ovalifolium) cv. Itabela (Mixed), (2) Marandu palisadegrass pastures with 150 kg N ha⁻¹ (Fertilized), and (3) Marandu palisadegrass without N fertilizer (Unfertilized). Rotational stocking with a variable stocking rate was used with a target herbage allowance of 1.0 kg forage kg body weight⁻¹. The pre-grazing green herbage mass was similar for Fertilized and Mixed pastures, with 54% and 63% more mass than Unfertilized pasture, respectively (p < .001). Cattle that grazed the fertilized pasture had the greatest average daily gain (ADG; p = .017). The stocking rate and liveweight gain per area were greatest for the Fertilized and Mixed pastures (p < .001 and p < .001, respectively). No differences between treatments were found for DM forage intake (p = .555). Organic matter digestibility was lowest (p < .001) for the Mixed pasture. The inclusion of the ovalifolium legume in the Marandu pasture had the same impact on beef cattle production as annual fertilization with 150 kg N ha⁻¹. The potential and environmental benefits of ovalifolium are discussed.     

Effects of reduced time on pasture caused by prolonged walking on behaviour and production of Mpwapwa Zebu cattle

In many African countries, cattle are often allowed to graze only during the daytime and the daily walk to pasture limits time for foraging. Two groups of cattle were allowed access to pasture for 9 h or 5 h associated with a daily walk of 0·5 h or 4·5 h respectively. Each treatment period lasted for 14 days in a cross‐over design. Observations of behaviour were carried out for 8 days in each treatment period. When only 5 h were allowed at pasture, the animals grazed less (0·61 vs. 0·66 of time) compared with the first 5 h of the 9 h treatment. The average daily milk yield was 323 g (0·078) higher when 9 h were allowed on pasture (P < 0·05 during the second week of treatments). There were no differences in milk yield after the end of the treatments. The daily liveweight gain was 250 g higher when the animals were on pasture for 9 h. These differences could be due to the limited time on pasture or to energy requirements for the walk to pasture. It is concluded that increasing the walking time and reducing time on pasture may compromise animal welfare and performance under the experimental conditions, i.e. on poor quality pastures in a warm humid climate where the main period at pasture is in the middle of the day.     

The use of pasture reflectance characteristics and arbuscular mycorrhizal root colonization to predict pasture characteristics of tallgrass prairie grazed by cattle and bison

An experiment was conducted to evaluate the potential for using arbuscular mycorrhizal fungal (AMF) root colonization and pasture reflectance characteristics as indicators of changes in tallgrass prairie vegetation resulting from differences in grazing history. The experiment was conducted within the context of a separate long‐term experiment in which eight 4·9‐ha pastures were grazed by either bison or cattle for nine consecutive years. Two separate ungrazed pastures were selected for comparison with grazed areas on the basis of similarity in burning regime, vegetation, soil and topographic characteristics. Four 45 m‐long transects were located in the upland sites within each pasture, and four plots were clipped to ground level along each transect. Reflectance readings were taken with a hand‐held radiometer at each sampling location and a soil core was collected within each plot for analysis of AMF root colonization. Reflectance readings at sixteen different wavelengths were used directly as inputs during multiple regression development or were transformed into each of three vegetation indices (normalized difference vegetation index, soil‐adjusted vegetation index and wide‐dynamic‐range vegetation index) and used in simple linear regressions. Ungrazed pastures were characterized by higher (P < 0·01) grass biomass, total biomass and canopy height than grazed pastures, but had a lower proportional abundance of forbs (P < 0·01) and amounts of forb biomass (P = 0·04). Species of herbivore did not significantly influence above‐ground characteristics that were measured. In general, AMF root colonization was relatively small and was not significantly affected by treatment and, accordingly, the variation was insufficient to test its potential as an indicator of grazing effects on vegetation or its potential relationship with pasture reflectance. Multiple regression equations based on individual wavelength reflectance values explained significantly more of the variation in above‐ground vegetation characteristics than did simple regressions using vegetation indices as predictor variables (r² values from 0·36 to 0·46 vs. 0·11 to 0·27) and have the potential to predict above‐ground vegetation characteristics in heterogeneous rangelands.     

Production performance and meat quality of grazing lambs finished on red clover, lucerne or perennial ryegrass swards

The combined benefits of a high crude protein concentration, and possible protein protection and growth‐promoting properties, make forage legumes potentially attractive as a natural means of increasing liveweight gain and time to slaughter of lambs in lamb finishing systems. An experiment was conducted to compare the production performance and meat quality of grazing lambs finished on red clover (Trifolium pratense), lucerne (Medicago sativa) or perennial ryegrass (Lolium perenne) swards. Replicate (n = 2) swards of red clover, lucerne and perennial ryegrass were rotationally grazed by ten ram lambs and ten ewe lambs from weaning until selection for slaughter at UK fat class 3L. Lambs grazing the red clover sward had a significantly higher liveweight gain and required significantly fewer days to slaughter than lambs grazing the lucerne sward (305 g d^?1 vs. 243 g d^?1; 38 d vs. 50 d), which in turn had a higher liveweight gain and required fewer days to slaughter than lambs grazing the perennial ryegrass sward (184 g d^?1; 66 d). Lambs grazing the red clover and lucerne swards had significantly higher herbage intakes than those grazing the perennial ryegrass sward (2·06, 1·72 and 1·16 kg DM d^?1 respectively), but in vivo digestibility of herbage was similar. Lambs grazing the red clover and lucerne swards also had significantly higher serum urea concentrations than those grazing ryegrass (12·5, 11·1 and 6·2 mmol L^?1 respectively). Killing‐out percentage was significantly higher for lambs grazing the red clover sward than for lambs grazing the perennial ryegrass sward (48% vs. 46%). There were no significant effects of finishing system on meat flavour, but meat from lambs finished on the lucerne sward was oxidatively less stable than that from lambs finished on the perennial ryegrass sward. Grazing the forage legume swards significantly increased the proportion of linoleic and linolenic acid in muscle tissue, and therefore the proportion of unsaturated to saturated fatty acids (0·19, 0·16 and 0·12 for the red clover, lucerne and perennial ryegrass swards respectively). However, the n?6/n?3 ratio was significantly lower for the muscle of lambs grazing the perennial ryegrass sward compared with those grazing the forage legume swards (1·13, 1·08 and 0·98 for the red clover, lucerne and perennial ryegrass swards respectively). The results indicate that by grazing lambs on forage legume swards it is possible to increase individual lamb performance without compromising meat quality.     

Effects of grass silage feed value on feed intake and performance of pregnant and lactating ewes and their lambs

Effects of grass silage feed value on intake, dietary sorting, body condition (BC) and body weight (BW) of pregnant and lactating ewes and on liveweight gain (LWG) of their suckling lambs were evaluated. Twin‐bearing ewes were fed ad libitum grass silage of (i) high feed value (HFV), (ii) medium feed value (MFV) and (iii) low feed value (LFV), plus 0·8 kg concentrate in late pregnancy and lactation. The HFV, MFV and LFV silages contained 11·7, 10·8 and 9·3 MJ metabolizable energy (ME) kg^?1 DM respectively. The HFV resulted in 8·2 and 15·2 MJ greater ME intake in pregnancy and 14·7 and 21·0 MJ greater ME intake from silage in lactation than MFV and LFV respectively (P < 0·01). Ewes fed the MFV and LFV silages sorted for more digestible particles during eating (P < 0·10). The HFV gave no loss in BC, whereas ewes fed MFV and LFV lost 0·7 and 0·8 units of BC, respectively, during lactation (P < 0·10). There were similar trends in BW. The nursing HFV lambs had 73 g higher daily LWG than the LFV lambs (P < 0·01). In conclusion, the HFV increased the ME intake of pregnant and lactating ewes, resulting in improved BC and BW of lactating ewes and LWG of suckling lambs compared to MFV and LFV.     

The effect of different legume‐based swards on intake and performance of grazing ruminants under Mediterranean and cool temperate conditions

Intake and performance of sheep or cattle grazing legume‐based swards were assessed over 2 years at four locations in Europe with different climatic conditions: Sardinia (Italy), southern France, northern Germany and south‐west England (UK). Legume species were sown in mixtures with locally appropriate companion grass species. Standard legume species commonly used at the location (Medicago polymorpha in Italy, Medicago sativa in France, and Trifolium repens in Germany and UK) were compared with two alternative legume species characterized by different agronomic or nutritional characteristics. They were: Trifolium subterraneum and Hedysarum coronarium in Italy; Trifolium incarnatum and Onobrychis sativa in France; Trifolium pratense and Lotus corniculatus in Germany; and Trifolium ambiguum and L. corniculatus in the UK. Lactating milk sheep in Italy, non‐lactating ewes in southern France, growing cattle in Germany, and ewes and lambs in the UK were used in three replicates per treatment. Intake and performance of sheep and cattle in various treatments varied with location, year and period within year. In Germany, intake and performance by cattle were not affected by treatment. In contrast, at the other locations, sheep grazing standard or alternative legume species known to contain condensed tannins (sulla, sainfoin and birdsfoot trefoil) had higher proportions of legume and crude protein (CP) concentrations in the diet and higher CP intakes than those grazing the other alternative legume species. Sheep performance paralleled these results. It is concluded that there is potential for a greater use of alternative legume species, at least for sheep‐grazing systems, in both the Mediterranean and cool temperate zones of Europe.     

Effect of formic acid and a bacterial inoculant on the amino acid composition of grass silage and on animal performance

An Italian ryegrass and hybrid ryegrass sward was harvested on 11 May 1994. The mean dry‐matter (DM) content of the herbage was 197 g kg^–1 fresh matter (FM), and mean nitrogen and water‐soluble carbohydrate contents were 20 and 272 g kg^–1 DM respectively. Approximately 72% of total nitrogen (TN) was in the form of protein‐nitrogen. The herbage was treated with either no additive, formic acid (3·3 l t^–1) (Add‐F, BP) or inoculant (2·3 l t^–1) (Live‐system, Genus) and ensiled in 100 t silos. Changes in effluent composition with time showed that silage fermentation and protein breakdown were delayed by treatment with formic acid. Formic acid and inoculant treatments also inhibited amino acid catabolism during ensilage. All silages were well fermented at opening with pH values < 4·0 and ammonia‐N concentrations of ≤ 50 g kg^–1 TN after 120 d ensilage. Treatment had an effect on protein breakdown as measured by free amino acid concentration, with values of 21·5, 18·2 and 13·2 mol kg^–1 N at opening (191 d) for untreated, formic acid‐treated and inoculated silages respectively. Amino acid catabolism occurred to the greatest extent in untreated silages with significant decreases in glutamic acid, lysine and arginine, and increases in gamma amino butyric acid and ornithine. The silages were offered ad libitum without concentrate supplementation to thirty‐six Charolais beef steers for a period of 69 d (mean live weight 401 kg). Silage dry‐matter intakes and liveweight gains were significantly (P < 0·05) higher on the treated silages. Silage dry‐matter intakes were 7·42, 8·41 and 8·23 kg d^–1 (s.e.d. 0·27) with liveweight gains of 0·66, 0·94 and 0·89 kg d^–1 (s.e.d. 0·058) for untreated, formic acid‐treated and inoculated silage‐fed cattle respectively. In conclusion, additives increased the intake of silage and liveweight gain by the beef steers, and it is suggested that this may be caused in part by the amino acid balance in these silages.     

The liveweight gain of Limousin × Friesian heifers grazing perennial ryegrass/white clover swards of different clover content and the effects of their grazing on sward botanical composition

An experiment was carried out in 1992 and 1993 to examine the effect of white clover content of perennial ryegrass/white clover swards on the performance of Limousin × Friesian heifers. Swards with low (L), medium (M) and high (H) white clover contents were established and managed by continuous variable stocking. A compressed sward height of 5·5 cm was maintained using a buffer fence to vary plot areas, with herbage surplus to grazing requirements cut, removed and yields measured. The mean white clover proportions for treatments L, M and H were 0·02, 0·19 and 0·18 in 1992 and 0·13, 0·16 and 0·31 in 1993 respectively. White clover contents of the swards reached a maximum in August and September, and differences between treatments diminished. There was no significant difference between treatments in the content of white clover in the swards in autumn 1993.
Liveweight gains of heifers increased asymptotically with increasing white clover content of the sward. Below a white clover herbage mass of 300 kg DM ha^–1, there was little effect on liveweight gain, which was 0·70 kg day^–1 over the grazing season. Between 400 and 450 kg DM ha^–1 white clover, liveweight gains were 0·85–0·90 kg day^–1. While clover content of the sward did not significantly affect utilized metabolizable energy output; the mean output over the grazing season in the two years from liveweight gain and herbage yield was 78 GJ ha^–1. It is suggested that, using this grazing system, white clover reached an equilibrium with a mean herbage mass of about 400 kg DM ha^–1 over the grazing season.     

The influence of grass and maize silage quality on apparent diet digestibility, metabolizable energy concentration and intake of finishing beef cattle

The effects of offering a range of grass silages and mixtures of grass and maize silages on the intake of beef cattle were studied. Four grass silages (GS1, GS2, GS3 and GS4) were used. Grass silage 1 was ensiled from a second regrowth in mid‐late September and treated with an inoculant additive. Grass silages 2, 3 and 4 were ensiled, without additive, from a primary regrowth harvested in early July, late May and mid‐June respectively. Wilting periods were 8, 30, 36 and 36 h for GS1, GS2, GS3 and GS4 respectively. Grass silages 1, 2 and 3 were precision chopped and ensiled in bunker silos, while GS4 was ensiled in round bales. The DM content (g kg^?1) and starch concentration (g kg^?1 DM) of the three maize silages (MS1, MS2 and MS3) used were 256 and 128, 256 and 184, and 402 and 328 for MS1, MS2 and MS3 respectively. Seventy‐two Charolais and Limousin cross‐bred steers were used in a changeover design with two 4‐week periods. The study consisted of sixteen treatments incorporating the four grass silages fed alone and with the three maize silages arranged as a 4 × 4 factorial design. The grass silage and maize silage mixtures were offered in a ratio of 0·60:0·40 (DM basis) once daily using individual Calan gates. All silages were offered ad libitum with 3 kg per head per day of a concentrate supplement. Dry matter and metabolizable energy (ME) intakes were highest with diets based on grass silage GS4 compared with diets containing the other grass silages. Metabolizable energy intakes of diets containing no maize silage, and those based on MS1 and MS2, were similar (P > 0·05) but lower than that of diets containing MS3. Only limited increases were found in DM and ME intakes with the inclusion of maize silage in grass silage‐based diets while offering high‐quality grass silage (assessed in terms of DM content, and fibre and N concentrations) promoted high voluntary intakes.     

Effects of method, rate and timing of slurry application to grassland on the preference by cattle for treated and untreated areas of pasture

Two experiments were conducted in the UK to investigate preference by cattle for areas of pasture treated or untreated with dairy cow slurry. Experiment 1 examined the effects of method and rate of slurry applied to a grass pasture in March (Spring); Experiment 2 examined the effects of method and timing of slurry application after cutting for silage in June (Summer). In both experiments, beef steers grazed grassland plots that had been treated with slurry on one half only of the plots for 4 weeks. Slurry was applied by shallow injection (I), trailing shoe (T) or conventional surface broadcasting (S) techniques. In Experiment 1, slurry was applied at 40 m³ ha^?1 (HI) or 20 m³ ha^?1 (LO) 21 d before grazing commenced; in Experiment 2, slurry was applied at 20 m³ ha^?1 either 32 d (E) or 10 d (L) before grazing commenced. Sward height was measured and animal behaviour was recorded during 8 × 24 h measurement periods in each experiment. Preference for slurry‐treated or untreated swards was indicated by a comparison of post‐grazing sward height on each sward and the proportion of total grazing time spent on the slurry‐treated swards. In Experiment 1, a smaller proportion of grazing time was spent on slurry‐treated areas of swards compared with untreated areas of swards on all treatments, but the proportion of time spent grazing the slurry‐treated sward was greater on method T than on methods I or S (0·28, 0·31 and 0·39 for methods S, I and T, respectively, s.e.d. = 0·035, P < 0·05). Steers showed no preference between slurry‐treated and untreated swards by 49, 45 and 44 d after slurry application for methods S, I and T respectively. Differences between HI and LO were not significant (P > 0·05). In Experiment 2, aversion to slurry‐treated swards compared with untreated swards was less for treatment E than for L, with a greater proportion of both residence and grazing time spent on the slurry‐treated sward of treatment E than L (0·43 and 0·28, respectively, for residence time, s.e.d. = 0·025, P < 0·001, and 0·47 and 0·30, respectively, for grazing time, s.e.d. = 0·021, P < 0·001). Significant differences were shown between the methods of slurry application for treatment E, with a greater proportion of grazing time spent on the slurry‐treated swards of methods I and T than method S (0·40, 0·52 and 0·49 for S, I and T, respectively, s.e.d. = 0·032, P < 0·001), and a greater difference between post‐grazing heights on slurry‐treated and untreated swards for method S than for I or T (30, 12 and 15 mm, respectively, s.e.d. = 4·8, P < 0·001). For treatment L, differences in the proportion of time spent grazing on slurry‐treated swards compared with untreated swards were not significant between treatments (0·26, 0·34 and 0·31 for methods S, I and T, respectively, s.e.d. = 0·040, P > 0·05) and indifference between slurry‐treated and untreated swards was achieved 77, 60 and 58 d after slurry spreading for methods S, I and T respectively. These results show that, when slurry is applied to pasture in a grazing rotation, the adverse effects on grazing behaviour associated with conventional surface broadcasting may be overcome by the use of novel slurry application techniques.     

The effect of stage of perennial ryegrass maturity at harvesting, fermentation characteristics and concentrate supplementation, on the quality and intake of grass silage by beef cattle

Abstract Two experiments were carried out in consecutive years to examine the influence of cutting date and restricting fermentation by carboxylic acid treatment on the nutrient intake from grass silage by beef cattle. In year 1, four cutting dates during July and August after a primary growth harvest and, in year 2, five cutting dates of primary growth between mid‐May and early July were examined. Herbage was ensiled either untreated or treated with high levels of acid additive (‘Maxgrass’, mean 8·6 l t^?1). Ninety‐six (year 1) or forty‐eight (year 2) continental cross steers were used in partially balanced changeover design experiments with each silage type either unsupplemented or supplemented with 4·5 (year 1) or 5·5 (year 2) kg concentrates head^?1 d^?1. Silage digestibility declined significantly between initial and final harvest dates (P < 0·001), whereas silage dry‐matter (DM) and digestible energy (DE) intakes were significantly higher in the initial compared with final harvest dates in both years of the study (P < 0·01). Similarly, silage DM and DE intakes, and total DM intakes, of acid‐treated and unsupplemented silages were greater than those of untreated and concentrate supplemented silages, respectively (P < 0·001). The results indicate that earlier cutting dates, and addition of acid to herbage before ensiling, can increase silage DM intake by beef cattle.     

Effects of replacing timothy silage by alsike clover silage on performance,carcass traits and meat quality of finishing Aberdeen Angus and Nordic Red bulls

The objective of the study was to determine the effects of silage plant species and cattle breed on performance and meat quality of finishing bulls. A feeding experiment was conducted using thirty Aberdeen Angus (AA) and thirty Nordic Red (NR) bulls. Both breeds were randomly allotted to three experimental diets. The composition (g kg^?1 dry matter) of the diets was as follows: (i) timothy silage (TS) (650) and barley (350); (ii) TS (325), alsike clover silage (AS) (325) and barley (350); and (iii) AS (650) and barley (350). The bulls were fed a total mixed ration ad libitum. Replacing TS by AS did not affect dry‐matter intake, growth, carcass conformation or meat quality traits of the bulls, but carcass fat score tended to decrease when replacing TS by AS (P = 0·07). The AA bulls grew faster and had better feed conversion and superior carcass conformation compared with the NR bulls (P < 0·001). The loin of the AA bulls had lower shear force value and was given higher scores in sensory analyses compared with the NR bulls (P < 0·01). The experiment demonstrated that replacing TS by AS in the diet of finishing bulls had minor effects on performance or meat quality.     

Effect of stage of maturity of whole-crop barley on intake and liveweight gain by dairy steers differing in initial live weight

The effect of maturity at harvest of whole-crop barley for ensiling on intake and liveweight gain of dairy steers differing in initial live weight (LW) was evaluated in an experiment over two years. Light (104–120 kg) and heavy (402–419 kg) dairy steers were fed diets containing predominantly whole-crop barley silage harvested at the milk stage [dry matter (DM) content of 284 g kg⁻¹ and neutral-detergent fibre (NDF) concentration of 526 g kg⁻¹ DM] or the dough stage of maturity (DM content of 328 g kg⁻¹ and NDF concentration of 445 g kg⁻¹ DM) and supplemented with up to 1 kg of concentrate. Dry matter intake (g kg⁻¹ LW) was higher for whole-crop barley harvested at the dough stage than at the milk stage of maturity and the difference was greater in heavy than in light steers ( P <  0·001). Liveweight gain was higher and feed conversion ratio was lower for dough-stage compared with milk-stage silage ( P  <   0·05) but there was no interaction with size of steer. Whole-crop barley harvested at the dough stage of maturity promoted higher liveweight gains in dairy steers compared with whole-crop barley harvested at the milk stage due to a higher DM intake.