Effects of traditional salt placement and strategically placed mineral mix supplements on cattle distribution in the Western Italian Alps

Effects of traditional salt placement (TS) and strategically placed mineral mix supplements (MMS) on cattle distribution were compared in the Italian Alps. Salt was placed within flat and herbaceous sites following the traditional method of farmers, whereas MMS blocks were placed on steep and shrub‐encroached sites within three large pastures (44 ha on average). Each TS and MMS site was paired with a control site, and eleven cows were tracked with GPS collars. Within 10 and 50 m of TS and MMS, treatment sites were used more than control sites (P < 0·05). No differences were detected (P > 0·05) in the number of visits by cows within 10 and 50 m of TS and MMS placements. No differences were detected in time spent within 10 m of TS and MMS placements, but cows spent more time (P < 0·05) within 50 m of TS. With either TS or MMS, cattle preferred areas with gentler terrain, higher forage pastoral value and closer to water (P < 0·001). When MMS was available cattle also preferred areas near MMS (P < 0·001). Shrub and herbaceous cover decreased near MMS placements (P < 0·05) from cattle grazing and trampling. Placement of MMS is a promising tool to enhance cattle distribution and potentially reduce shrub encroachment in rugged mountain pastures.     

Grazing preference of Merino sheep for naturalized annual clover species relative to commonly sown clover species

Selective grazing of white clover (Trifolium repens) over grass species in temperate pastures results in reduced clover abundance and availability over time. Within sheep‐ and cattle‐grazed dryland (<800 mm annual rainfall) hill and high country areas of New Zealand, naturalized unsown annual clover species show greater persistence and abundance over sown clovers. With a view to understanding legume abundance in these areas, Merino sheep grazing preference was investigated for pure swards of naturalized species Trifolium dubium, T. glomeratum, T. arvense and T. striatum and commonly sown species T. repens and T. subterraneum. The Chesson–Manly preference index was used to explore the hypothesis that grazing preference differs between these species and changes as plants mature. Herbage offtake was quantified at vegetative (mid–late spring; November) and reproductive (early summer; December) stages of plant maturity. Significant preference distinctions between species (P < 0·05) occurred in December, with relative preference ranging from 0·248 for T. repens to 0·065 for T. dubium. Reduced relative preference for naturalized species was related to decreasing nutritive value from spring to summer, reflecting increased stem and flower sward content. Relative preference was negatively related to increasing acid detergent fibre and neutral detergent fibre and positively related to greater crude protein and dry‐matter digestibility. Naturalized annual clover species of lower grazing preference at reproductive maturity will benefit pasture sustainability via herbage and seed production and associated nitrogen‐fixation inputs.     

Determination of nutritive value of forages in south Texas using an in vitro gas production technique

The objectives of this study were to use the in vitro gas production (IVGP) technique to evaluate the pattern and parameters of anaerobic fermentation of forages from south Texas pastures throughout the year to (i) obtain empirical relationships between the IVGP technique fermentation parameters and chemical composition of the forages and (ii) develop equations to compute total digestible nutrients (TDN). During four consecutive years (2006–2009), forage samples were collected monthly (n = 39) at the King Ranch, TX, and chemical analyses and IVGP were obtained. For 2006, 2007, 2008 and 2009, the average lag times, h, were 6·47 ± 0·54, 7·75 ± 0·65, 7·49 ± 2·01 and 5·44 ± 1·46, and the average ratio of millilitre of gas per milligram of dry matter was 0·41 ± 0·11, 0·34 ± 0·09, 0·34 ± 0·07 and 0·26 ± 0·10 respectively. There was a moderate negative correlation (r = ?0·53) between lignin and neutral detergent fibre (NDF) and a moderate positive correlation (r = 0·58) between crude protein and NDF digestibility. The predicted fractional passage rate (kp) by the large ruminant nutrition system model using the level 2 solution was on average 0·0366 h^?1. The average computed TDN assuming a kp of 0·04 h^?1 was 55·9%. We concluded the IVGP technique may be used to predict TDN values of warm‐season forages.     

Chloris gayana Kunth under different defoliation regimes. Morphogenesis,sward structure and leaf area index

Subtropical pastures are an important alternative to increase forage yields to fulfil cattle nutritional requirements. Despite the increasing expansion of these pastures in the semiarid subtropical region of Argentina, there is very little information about their responses to grazing management. The aim of this study was to evaluate the effect of different defoliation regimes on morphogenesis, sward structure and leaf area index of one of the most expanded forage species in this region, Chloris gayana Kunth. A combination of two defoliation frequencies (300 and 500 GDD) and two defoliation intensities (1 and 3 green stubble leaves) was compared by a controlled experiment that comprised 1,500 GDD. Defoliation frequency significantly affected leaf elongation rate (LER) and leaf area index (LAI). Under the high defoliation frequency, LER and LAI resulted almost half than under low defoliation frequency (0.34 ± 0.08 vs. 0.67 ± 0.08 mm·tiller^?1·GDD^?1; 8.31 ± 2.27 m²/m² vs. 13.27 ± 1.59 m²/m², at 300 or 500 GDD respectively), regardless of the intensity. Defoliation frequency or intensity did not affect leaf appearance rate, leaf lifespan, leaf size, number of green leaves per tiller nor tiller density at the end of the experiment. We conclude that to maintain high LER and LAI in Chloris gayana Kunth cv. Épica INTA‐Pemán pastures, defoliation frequency could be of 500 GDD. Since leaf lifespan was 415 ± 110 GDD, under this defoliation frequency, a maximum accumulation of green leaf tissues with very little dead tissues may be achieved.     

Performance and blood parameters when lambs and meat‐goat kids were finished on pasture with and without whole cottonseed (Gossypium hirsutum) supplementation

We evaluated forage production patterns, weight gains and blood parameters when lambs (Ovis aries) and meat‐goat (Caprus hircus) kids were finished on a mixed sward of cocksfoot (Dactylis glomerata L.), red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) with (SUP) and without (UNSUP) supplemental whole cottonseed (Gossypium hirsutum; WCS) in a replicated study. Botanical composition and energy/protein ratios of the sward varied with year and with time during the growing season. Swards had greater amounts of red clover relatively early and more cocksfoot later in the season. Suffolk (SX) lambs had the heaviest body weights, Katahdin (KA) lambs were intermediate, and meat‐goat (GX) kids were the lightest at the end of each year. Overall body weight gain followed a trend of SX > KA > GX, and WCS supplementation increased weight gain for all animals by 18%. Only in 2008 did SUP animals have higher blood urea nitrogen levels, which may indicate less efficient use of dietary nitrogen when grazing grass–legume pastures managed for high nutritive value compared with UNSUP animals. Gossypol in WCS did not affect blood packed cell volume between SUP and UNSUP lambs and meat‐goat kids. Suffolk lambs, Katahdin lambs and cross‐bred Boer meat‐goat kids finished on pasture with and without WCS supplementation produced desirable body weights for most ethnic markets in the USA.     

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.     

Impact of ferulic acid esterase‐producing lactobacilli and fibrolytic enzymes on ensiling and digestion kinetics of mixed small‐grain silage

This study evaluated the effects of a ferulic acid esterase (FAE) and a non‐FAE‐producing inoculant applied alone or in combination with exogenous fibrolytic enzymes (EFE) on the fermentation and nutritive value of mixed grain (barley, oats and spring triticale) silage. The mixed crop was ensiled in laboratory mini‐silos either untreated (CON), or treated with a FAE inoculant (FAE), a non‐FAE inoculant (NFAE) or NFAE + EFE. Inoculated silages were lower (P < 0·01) in water‐soluble carbohydrate, whereas NFAE and NFAE + EFE silages had higher (P < 0·001) DM loss than other silages. FAE and NFAE silage had higher neutral detergent fibre (NDF), but were lower in NFAE + EFE than other silages (P < 0·001). Copy numbers of 16S rRNA associated with Lactobacillus buchneri were higher (P < 0·001) in NFAE and NFAE + EFE silages than in others, resulting in higher (P < 0·001) acetic acid in these silages. NFAE + EFE silage had lower (P < 0·001) in vitro gas production and NDF digestibility (NDFD) than other silages. FAE silage had higher (P < 0·01) in situNDFD than CON and NFAE + EFE silages. Inoculation of mixed small‐grain silage with NFAE‐producing inoculants combining EFE reduced NDFD.     

Herbage production,nutritive value and animal productivity within hardwood silvopasture,open and mixed pasture systems in Appalachia,United States

Demand for livestock food products is projected to increase dramatically through to 2050. Increased livestock production capacity on marginal lands will be critical to meeting this demand. A 5‐year research effort was undertaken to evaluate lamb and sward productivity within open and hardwood silvopasture (SP) systems in Appalachia, USA. Grazing began in mid to late April each year, with the grazing season averaging 141 d. Grazing system treatments during 2002 and 2003 grazing seasons were as follows: 100% open pasture (OP), 67% OP and 33% SP, and 67% OP and 33% SP with delayed SP grazing initiation (OSD). In 2004, a 100% SP (SP) system was added. Animals were rotationally stocked through either 6 (2002–2004) or 7 (2005–2006) paddocks. Open pasture produced greater (P < 0·001) grazing season herbage yield, while all systems generated similar animal performance. Based on summer solstice, herbage production in spring was greater (P < 0·001) than summer, except in 2003. Total non‐structural carbohydrate (TNC) content was greater (P < 0·05) in spring than in summer, except in 2004. Animal performance was superior in spring versus summer (P < 0·001). Animal plasma urea nitrogen (PUN) was lower (P < 0·05) for OP in 2003. When PUN was correlated with nutritive value indicators, the ratio of TNC to crude protein (CP) had the strongest correlation. The strong correlation indicates the need for synchronized ruminal energy and CP availability. Development of silvopasture from existing woodlots has potential to improve whole farm productivity on marginal lands.     

Defoliation patterns and their implications for the management of vegetative tropical pastures to control intake and diet quality by cattle

This study assessed the use of pasture attributes to control daily intake and diet quality during progressive defoliation on pastures of Axonopus catarinensis. Three consecutive 12‐day grazing treatments of progressive defoliation were conducted with Brahman cross‐steers. Daily forage intake and defoliation dynamics were assessed using a pasture‐based method. The treatments differed in initial sward height (33, 44 and 61 cm) and herbage mass (1030, 1740 and 2240 kg ha^?1). The post‐grazing residual sward height, at which forage intake decreased, appeared to increase with the initial sward height (12·3, 14·6 and 15·5 cm). Steers grazed up to four distinctive grazing strata in all treatments. The depth and herbage mass content of the top grazing stratum were at least five times higher than the lower grazing strata in all treatments. This explains why forage intake decreased when the top grazing stratum was removed in approximately 93% of the pasture area in all treatments, equivalent to approximately 7% of the pasture area remaining ungrazed. We conclude that the residual ungrazed area of the pasture, rather than residual sward height, can be used to develop grazing management strategies to control forage intake and diet quality in a wide range of pasture conditions.     

Effect of offering silage during housing at night on the performance of grazing dairy cows and on labour requirements

In the UK, dairy cows are increasingly housed at night throughout the grazing season. However, there is limited information on cow performance and the impact on labour requirements when a forage supplement is offered during housing at night throughout the entire grazing season. The effects of housing at night were studied in two experiments, in which two treatments were compared. On treatment part‐grazing (PG), dairy cows were given access to grazing by day and were offered grass silage while housed at night, and, on treatment continuous grazing (CG), dairy cows were given access to grazing both by day and by night. Experiments 1 (138‐d duration) and 2 (127‐d duration) involved sixty (primiparous) and seventy‐six (primiparous and multiparous) Holstein‐Friesian dairy cows respectively. Concentrates were offered during milking at 4·0 and 3·0 kg per cow per day in Experiments 1 and 2 respectively. In Experiment 1, total milk output was significantly higher with treatment PG than treatment CG (P < 0·01) while the reverse occurred in Experiment 2 (P < 0·001). Milk protein concentration was significantly higher with treatment CG in Experiments 1 and 2 (P < 0·001). Cows on treatment CG in Experiment 2 had significantly higher body condition scores and live weights at the end of experiment than those on treatment PG (P < 0·05). Weekly labour requirements were calculated to be proportionally 0·04 lower on treatment PG than on treatment CG. When offered silage during housing at night, the response of grazing dairy cows was largely determined by the grazing conditions encountered and the quality of the forage offered.     

Production of beef cattle grazing on Brachiaria brizantha (Marandu grass)—Arachis pintoi (forage peanut cv. Belomonte) mixtures exceeded that on grass monocultures fertilized with 120 kg N/ha

Mixed grass/legume pastures are an alternative to grass monocultures for increased beef cattle production in tropical climates. The objective of this study was to evaluate the productivity of beef cattle grazing either a mixed pasture of Brachiaria brizantha cv. Marandu grass and Arachis pintoi (forage peanut) cv. Belomonte or a Marandu monoculture, under rotational stocking. Five trials were conducted over a period of nine years in north-eastern Brazil where the sward structure (forage, grass and legume mass) and animal performance were compared for a mixed Marandu grass/forage peanut pasture, and a Marandu grass monoculture with 120 kg N ha⁻¹ y⁻¹. Stocking rate was adjusted to maintain forage allowance at 4% body weight/day. A block design was used with four replicates, and warm and cool seasons within each trial were considered, using repeated measurements over time. In the warm season, the forage mass in the mixed pastures was 17% greater than in the monoculture (p = .049), and the stocking rate, average daily gain and liveweight gain per ha were 16.4%, 20.0% and 28.7% greater (p = .004, p < .001 and p < .001 respectively). The average daily gain showed a positive linear relationship with the legume proportion in the sward (p < .001). The mixed forage peanut/Marandu pasture sustained significantly greater beef cattle production (789 kg ha⁻¹ y⁻¹) compared to the N-fertilized grass monoculture (655 kg ha⁻¹ y⁻¹). Appropriately managed, mixed pastures of forage peanut/Brachiaria pastures are sustainable and have high potential for use in the humid tropics.     

Production, survival and nutritive value of the perennial legumes Dorycnium hirsutum and D. rectum subjected to different cutting heights

Dorycnium hirsutum and D. rectum are perennial legumes which may have potential for use as pastures for the control of groundwater recharge in southern Australia. Little is known about the quality of the forage of Dorycnium species for grazing livestock or how these species respond to cutting. The effect of cutting height on plant survival, production of dry matter (DM), the proportion of leaf, edible stem (approximately <5 mm diameter) and woody stem in the DM and the nutritive value of the edible components was investigated. Biomass above five cutting‐height treatments (uncut, ground level, 5–8 cm, 10–15 cm and 15–30 cm above ground level) was removed at 8‐week intervals from plots of D. hirsutum and D. rectum from September 2002 to July 2003. In both species, plants subjected to lower cutting height treatments produced less DM above the height of the cut than those cut at higher heights. DM production declined over time in all treatments. Plants cut to ground level failed to regrow after the second harvest in D. hirsutum and the fourth harvest in D. rectum. Thus, these Dorycnium species were susceptible to high severity defoliations at 8‐week intervals. Negligible inedible woody stem was present in regrowth of both species after 8 weeks but D. hirsutum regrowth had a higher proportion of leaf (0·72) than D. rectum (0·56). Plants left uncut accumulated a large proportion of inedible woody stem in the DM (0·69 in both species) by July 2003, particularly at the base of the plant. Edible DM from regrowth of D. hirsutum and D. rectum had crude protein (CP) concentrations of 120 and 150 g kg^?1 DM; dry matter digestibility (DMD) values of 0·45 and 0·58; organic matter digestibility (OMD) values of 0·50 and 0·64; neutral‐detergent fibre (NDF) concentrations of 370 and 290 g kg^?1 DM; and acid‐detergent fibre (ADF) concentrations of 260 and 210 g kg^?1 DM, respectively. Medicago sativa, grown under similar conditions, had higher digestibility values (0·63 DMD and 0·66 OMD) and similar CP concentrations to D. rectum (140 g kg^?1 DM), but higher concentrations of NDF and ADF (410 and 290 g kg^?1 DM). Leaf material from both Dorycnium species had a higher nutritive value than edible stems, with DMD and OMD values of leaf of D. rectum being 0·68 and 0·74 respectively. Uncut plants had a much lower nutritive value of edible DM than the regrowth from cut treatments; older material was also of a lower nutritive value. The relatively low nutritive value of even the young regrowth of Dorycnium species suggests that forage quality is a major limitation to its use. Forage of Dorycnium species could be used during periods when other sources of forage are in short supply but infrequent grazing it is likely to produce forage of a low nutritive value.     

Effects of ethanol,molasses and Lactobacillus plantarum on fermentation characteristics and aerobic stability of total mixed ration silages

This study was conducted to evaluate the effects of Lactobacillus plantarum, molasses and/or ethanol on fermentation quality and aerobic stability of total mixed ration (TMR) silage, which is widely used in dairy cow diets at mid‐to‐late lactation in Tibet. TMR was treated with ethanol (E), molasses (M), Lactobacillus plantarum(L), ethanol+molasses (EM), ethanol+Lactobacillus plantarum (EL) plus control. After 45 d of ensiling, inoculant significantly (P < 0·05) increased lactic acid (LA) concentration and decreased pH, ammonia nitrogen (AN) concentration, and aerobic bacterial and yeast counts, compared to control. After the first 3 d of aerobic exposure, LA for silages without ethanol started to decrease, while LA for E silages almost remained unchanged till the end of the aerobic exposure period. The pH in TMR silages without ethanol gradually increased, while that for E and EL remained about 4·60 and 4·00, respectively, and EL showed the lowest pH among six silages over the course of aerobic exposure. Aerobic bacterial counts in control, M and EM silages were significantly higher (P < 0·05) than those in E, L and EL, and yeast counts in E and EL silages were significantly lower (P < 0·05) than those in other silages after 9 d of aerobic exposure. The results suggest that inoculation with L. plantarum was more effective in altering fermentation characteristics than adding molasses, while ethanol showed a potential to protect TMR silages from pH increase and delayed the growth of aerobic bacteria and yeast either alone or in combination with L. plantarum.     

Impact of deferred grazing and fertilizer on plant population density,ground cover and soil moisture of native pastures in steep hill country of southern Australia

The impact of deferred grazing (no defoliation of pastures for a period generally from spring to autumn) and fertilizer application on plant population density, ground cover and soil moisture in a hill pasture (annual grass dominated, with Australian native grasses being the major perennial species) were studied in a large‐scale field experiment from 2002 to 2006 in southern Australia. Three deferred grazing strategies were used: short‐term deferred grazing (no defoliation between October and January each year), long‐term deferred grazing (no defoliation from October to the autumn break, that is the first significant rainfall event of the winter growing season) and optimized deferred grazing (withholding time from grazing depends on morphological development of the plants). These treatments were applied with two fertilizer levels (nil fertilizer and 50 kg P ha^?1 plus lime) and two additional treatments [continuous grazing (control) and no grazing for year 1]. Deferred grazing increased (P < 0·05) perennial grass tiller density compared with the control. On average, the tiller density of the three deferred grazing treatments was 27–88% higher than the control. There was a negative (P < 0·01) relationship between perennial and annual grass tiller density. Fertilizer application increased (P < 0·05) legume plant density. The densities of annual grasses, legumes, onion grass (Romulea rosea) and broadleaf weeds varied between years, but perennial grass density and moss cover did not. The ground cover of the deferred grazing treatments in autumn was on average 27% higher than the control. Soil moisture differed between treatments at 15–30 cm depth, but not at 0–15 depth over autumn and winter. The results imply that deferred grazing can be an effective tool for rejuvenating degraded native pastures through increases in native grass tiller density and population and through improving farm productivity and sustainability.     

Seed yield variation in plains rough fescue (Festuca hallii (Vasey) Piper) populations and its relation with phenotypic characteristics and environmental factors

Plains rough fescue (Festuca hallii (Vasey) Piper) is a dominant grass in the endangered Fescue Prairie of North America. Infrequent and unpredictable seed production presents a challenge for the use of this species in restoration and rangeland seeding. The objective of this study was to compare seed yield of different plains rough fescue populations and to determine the dependence of seed yield on phenotypic characteristics. Effect of weather conditions during the floral induction and initiation period of different years of the study was also compared. In 2007, a completely randomized field plot experiment was established from eleven populations of plains rough fescue at Swift Current, SK, Canada. In 2007, 2010 and 2011, individual plant seed yield, reproductive tillers, above‐ground biomass, plant height and crown diameter were measured, and plant vigour was scored. All measured variables differed significantly (P ≤ 0·05) among populations. Four populations were identified as having higher seed yield potential. Plants in these four populations also had characteristics of good plant vigour, taller stems, more reproductive tillers and greater biomass. Seed yield increased linearly with increasing plant height, crown diameter, above‐ground biomass and number of reproductive tillers (r² ranged 0·17–0·67, P < 0·001), but number of reproductive tillers (r² = 0·53–0·67, P < 0·001) was a better predictor for selection of lines with higher seed yield. Although seed yield varied among years, populations with higher seed yield tended to produce greater amounts of seed over the period of the study.     

A comparison between cutting and animal grazing for dry‐matter yield,quality and tiller density of perennial ryegrass cultivars

Perennial ryegrass (Lolium perenne L.) evaluation trials are often conducted under simulated grazing to identify the most productive cultivars. It is unclear whether simulated grazing identifies the most productive cultivar for animal‐grazed swards. Ten cultivars were established as plots and managed concurrently under simulated grazing (SG), animal grazing (AG) and conservation (CON). The experiment lasted 3 years with dry‐matter (DM) off‐take, digestibility, tiller density and ground‐cover score recorded in all years. A good relationship existed between DM off‐take under SG and CON (R² = 0·73). The relationship between SG and AG was strongest in year 2 and 3 (R² = 0·53 and 0·55 respectively). High DM production was observed in SG swards in year 1; this was weakly related to the DM production of the AG sward. Across the 3 years, the CON treatment had higher yields than either of the other two treatments and was poorly correlated to DM yield under AG, confirming that cultivars should be evaluated under a similar defoliation frequency to their intended use. Tiller density declined quickest under CON and slowest under AG. Some reranking of cultivars occurred between defoliation managements. The results show that simulated grazing is a useful indicator of DM yield performance of animal‐grazed swards.     

Effect of sward height and vertical distribution of clover on performance of cashmere goats in autumn

To investigate the effect of sward height on liveweight change in goats grazing grass/white clover swards, an experiment was conducted from mid-August to mid-November with groups of non-lactating female cashmere goats that continuously grazed perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) swards. Three replicated different sward height treatments — 10–8 cm (high), 7–5 cm (medium) and 5–3 cm (low) — were used to examine the effects on the competitive ability of grass and clover components within the sward canopy and their effect on liveweight. The pasture after grazing by goats had relatively higher ryegrass leaf (+0·26, high; +0·32, medium; and +0·18, low) and lower dead ryegrass proportions (?0·28, high; ?0·23, medium; and ?0·18, low) than at the beginning of the experiment, whereas the white clover fraction in the sward remained constant (+0·04, high; ?0·02, medium; and +0·03, low). Higher proportions of the white clover leaf lamina and petiole were found near the top of the sward canopy and were negatively correlated with the rate of liveweight gain by goats (P < 0·05). Goats gained 50·2 g Live weight (LW) d^?1 on the tallest treatment (high) but lost 0·01 and 42·3 g LW d^?1 on the medium and low sward height treatments respectively (s.e.d. 13·21, P < 0·001). Liveweight changes that occurred between sampling periods were also correlated (_R2= 0·858, P < 0·001) with changes in the mean sward height and proportion of white clover lamina-petiole at the sward surface in relation to the proportion found within the whole sward. These results suggest that goat liveweight gains would be increased if another species was introduced to reduce the white clover proportion in the surface horizon.     

Individual and socially learned preferences for biserrula (Biserrula pelecinus L.) in sheep

This study examined how sheep develop a learned aversion to the annual legume biserrula (Biserrula pelecinus L.). Merino sheep were grazed on paddocks sown with either (i) biserrula, (ii) biserrula + ryegrass (Lolium rigidum Gaud.), (iii) crimson clover (Trifolium incarnatum L.), (iv) crimson clover + ryegrass or (v) ryegrass, for 4 weeks. Relative preference (Chesson–Manly selection index) was determined by offering randomly ordered monoculture plots of the three forage species. The groups of sheep were then combined into a single group and grazed a paddock containing a monoculture sward of each plant type for 5 d. Relative preference of sheep was tested again after the completion of the combined grazing. The experiment was repeated at three stages of plant phenology: vegetative, reproductive and senesced. Relative preference for biserrula was lower in sheep that had grazed the paddock sown with only biserrula compared with sheep that grazed a combination of biserrula + ryegrass, at both the vegetative (α; −0·11 vs. 0·32) and reproductive (α; 0·18 vs. 0·63) stages. At each stage of phenology, when groups were combined and grazed together, preference for biserrula became uniform. This supported the hypothesis that sheep develop an aversion to biserrula when they graze a pasture containing biserrula. However, we concluded that the familiarity of sheep with biserrula did not result in low relative preference; rather, the aversion was more likely a response to the high proportion of this plant in their diet. Social facilitation may have enabled sheep to overcome rapidly the food aversion.     

Effects of incorporating cowpea in a subtropical grass pasture on forage production and quality and the performance of cows and calves

The increasing cost of N fertilizer has stimulated an interest in sourcing protein from warm‐season legumes among beef cattle producers in the tropical/subtropical areas of the world. The objective of this study was to evaluate effects of two strategies of incorporating cowpea [Vigna unguiculata (L.) Walp.] into bahiagrass (Paspalum notatum Flügge) pastures on the herbage characteristics and performance of grazing cow–calf pairs. The study was conducted in Ona, Florida, USA, from May to August in 2007 and 2008. Experimental units were 1·0 ha. Treatments were bahiagrass pasture alone (control), 50:50 bahiagrass–cowpea pasture (cowpea), bahiagrass pasture with a cowpea creep grazing area (0·1 ha, creep grazing) and bahiagrass pasture with a creep‐fed concentrate [(creep feeding; 10 g kg^?1 body weight (BW)]. The cowpea pastures had lower herbage mass [HM, 1·8 vs. 3·7 t ha^?1] and herbage allowance [HA, 0·8 vs. 1·4 kg DM kg^?1 live weight (LW)] compared with the other treatments. Cowpea had greater CP (CP, 160 g kg^?1) and in vitro digestible organic matter (IVDOM), (600 g kg^?1) than bahiagrass (110 and 490 g kg^?1 respectively); however, cowpea HM was only 0·9 t ha^?1 in May and 0·7 t ha^?1 in June, but it did not persist in July and August. Calves receiving the creep feeding treatments had greater average daily gain (0·8 vs. 0·7 kg d^?1) than calves in other treatments. Further research is necessary to exploit the superior nutritive value of cowpea in grazing systems in the south‐eastern USA.     

Estimation of nitrogen concentration and in vitro dry matter digestibility of herbage of warm-season grass pastures from canopy hyperspectral reflectance measurements

Remote sensing of nitrogen (N) concentration and in vitro dry matter digestibility (IVDMD) in herbage can help livestock managers make timely decisions for adjusting stocking rate and managing pastures during the grazing season. Traditional laboratory analyses of N and IVDMD are time-consuming and costly. Non-destructive measurements of canopy hyperspectral reflectance of pasture may provide a rapid and inexpensive means of estimating these measures of nutritive value. Using a portable spectroradiometer, canopy reflectance was measured in eight warm-season grass pastures in the USA in June and July in 2002 and 2003 to develop and validate algorithms for estimating N concentration and IVDMD of herbage. Nitrogen concentration of herbage was linearly correlated (r = 0·82; P < 0·001) with a ratio of reflectance in the 705- and 1685-nm wavebands (R₇₀₅/R₁₆₈₅) and IVDMD was correlated with R₇₀₅/R₅₃₅ (r = 0·74; P < 0·001). Compared with simple linear regressions of N concentration and IVDMD in herbage with two-waveband reflectance ratios, multiple regression, using maximum r² improvement, band-depth analysis with step-wise regression, and partial least-squares regression enhanced the correlation between N concentration and IVDMD of herbage and canopy reflectance values (0·81 ≤ |r| ≤ 0·90; P < 0·001). Validation of the prediction equations indicated that multiple regression only slightly improved accuracy of a model for predicting N concentration and IVDMD of herbage compared with simple linear regression of reflectance ratios. Results suggest that the N concentration and IVDMD of herbage of warm-season grass pastures can be rapidly and non-destructively estimated during the grazing season using canopy reflectance in a few narrow wavebands.