Exposure to hot environments affects milk yield (MY) and milk composition of pasture and feed-pad fed dairy cows in subtropical regions. This study was undertaken during summer to compare MY and physiology of cows exposed to six heat-load management treatments. Seventy-eight Holstein-Friesian cows were blocked by season of calving, parity, milk yield, BW, and milk protein (%) and milk fat (%) measured in 2 weeks prior to the start of the study. Within blocks, cows were randomly allocated to one of the following treatments: open-sided iron roofed day pen adjacent to dairy (CID) + sprinklers (SP); CID only; non-shaded pen adjacent to dairy + SP (NSD + SP); open-sided shade cloth roofed day pen adjacent to dairy (SCD); NSD + sprinkler (sprinkler on for 45 min at 1100 h if mean respiration rate >80 breaths per minute (NSD + WSP)); open-sided shade cloth roofed structure over feed bunk in paddock + 1 km walk to and from the dairy (SCP + WLK). Sprinklers for CID + SP and NSD + SP cycled 2 min on, 12 min off when ambient temperature >26°C. The highest milk yields were in the CID + SP and CID treatments (23.9 L cow−1 day−1), intermediate for NSD + SP, SCD and SCP + WLK (22.4 L cow−1 day−1), and lowest for NSD + WSP (21.3 L cow−1 day−1) (P < 0.05). The highest (P < 0.05) feed intakes occurred in the CID + SP and CID treatments while intake was lowest (P < 0.05) for NSD + WSP and SCP + WLK. Weather data were collected on site at 10-min intervals, and from these, THI was calculated. Nonlinear regression modelling of MY × THI and heat-load management treatment demonstrated that cows in CID + SP showed no decline in MY out to a THI break point value of 83.2, whereas the pooled MY of the other treatments declined when THI >80.7. A combination of iron roof shade plus water sprinkling throughout the day provided the most effective control of heat load.

ObjectiveTo establish the prevalence of anthelmintic resistance in ovine gastrointestinal nematodes in southern Queensland.DesignAn observational parasitological study using the faecal egg count reduction test.MethodsSheep farms (n = 20) enrolled in this study met the twin criteria of using worm testing for drench decisions and having concerns about anthelmintic efficacy. On each farm, 105 sheep were randomly allocated to one of six treatment groups or an untreated control group. Faecal samples were collected on day 0 and days 10-14 for worm egg counts and larval differentiation. Single- and multi-combination anthelmintics, persistent and non-persistent, oral liquid or capsule, pour-on and injectable formulations were tested. Monepantel was not tested. Farmers also responded to a questionnaire on drenching practices.ResultsHaemonchus contortus was the predominant species. Efficacy <95% was recorded on 85% of farms for one or more anthelmintics and on 10% of farms for six anthelmintics. No resistance was identified on three farms. The 4-way combination product was efficacious (n = 4 farms). Napthalophos resistance was detected on one farm only. Resistance to levamisole (42% of farms), moxidectin injection (50% of farms) and the closantel/abamectin combination (67% of farms) was identified. Moxidectin oral was efficacious against Trichostrongylus colubriformis, which was predominant on only one farm. Of the farms tested, 55% ran meat breeds, 60% dosed more than the recommended dose rate and 70% always, mostly or when possible practised a drench and move' strategy.ConclusionThis level of anthelmintic resistance in southern Queensland will severely compromise worm control and force increased use of monepantel.

Faecal Egg Count Reduction Tests (FECRTs) for macrocyclic lactone (ML) and levamisole (LEV) drenches were conducted on two dairy farms in theSubtropical, summer rainfall region of eastern Australia to determine if anthelmintic failure contributed to severe gastrointestinal nematode infections observed in weaner calves. Subtropical Cooperia spp, were the dominant nematodes on both farms although significant numbers of Haemonchus placer were also present on Farm 2On Farm 1, moxidectin pour-on (MXD) drenched at 0.5 mg kg(-1) liveweight (LW) reduced the overall Cooperia burden by 82% (95% confidence limits, 37-95%) at day 7 post-drench As worm burdens increased rapidly in younger animals in the control group (n = 4). levamisole was used as a salvage drench and these calves withdrawn from the trial on animal welfare grounds after sample collection at day 7. Levamisole (LEV) dosed at 6 8 mg kg(-1) LW reduced the worm burden in these calves by 100%. 7 days after drenching OnFarm 2, MXD given at 0 5 mg kg(-1) LW reduced the faecal worm egg count of cooperioids at day 8 by 96% (71-99%), ivermectin oral (IVM) at 0.2 mg kg(-1) LW by 1 6% (-224 to 70%) and LEV oral at 7 1 mg kg(-1) LW by 100%. For H placer the reductions were 98% (85-99.7%) for MXD, 0.7% (-226 to 70%) for IVM and 100% for LEVThis is the first report in Australia of the failure of macrocyclic lactone treatments to control Subtropical Cooperia spp and Suspected failure to control H placer in cattle Crown Copyright (C) 2009 Published by Elsevier B.V All rights reserved

The experiment started in March 2002 with a 1-week adaptation, and an 8-week observation, period. Forty-two Holstein-Friesian cows in early/mid-lactation were stratified and randomly allocated to 6 groups of 7 cows. Each group was offered a SGM (11 kg DM/cow/day) formulated to contain CP of 10, 12, 14, 16.5, 19 or 21% DM. This was achieved by substituting cottonseed meal (CSM) and urea for grain. The SGM consisted of maize silage, barley grain, CSM and urea (4.3, 3.6-6.2, 0.56-2.8 and 0-0.1 kg DM/head/day, respectively). The cows were fed on a shaded feed-pad during the day, and during the evening and night, they grazed rhodes grass (Chloris gayana cv. Callide) pasture, with a fresh pasture strip offered each day. A regression model of parallel smooth curves with additional linear trends for the CP% of each SGM best represented 4% fat corrected milk yield (FCM) (P=0.06), with the slope for 10% CP being different to those for 14, 16.5 and 21% (Figure 1). Similar analyses fitting cubic smoothing splines for the effect of the CP% of SGM on FCM for each week showed that much of the difference in weeks 3- 9 could be accounted for by fitting parallel smoothed curves to each week's data. Quadratic regressions that best reflected the curves were then fitted for each week (P<0.001) (Figure 2).

The effects of stocking rate and irrigation frequency on the milk production of cows grazing nitrogen-fertilised Callide rhodes grass pastures was studied in south-east Queensland. Pastures were stocked at 3.5, 5.25 and 6.1 cows/ha from January-May inclusive, and irrigated at fortnightly or monthly intervals. Yields on offer pregrazing and pasture, leaf and stem residues after grazing decreased at the higher stocking rates. Consumption of grass leaf averaged 10.6, 7.7 and 6.5 kg DM/cow/d for cows grazed at 3.5, 5.25 and 6.1 cows/ha, respectively (P 0.05). Milk yields averaged 16.6 kg/cow/d for Weeks 7-18 and were unaffected by treatment. Liveweight loss in the first 15 weeks of the experiment averaged 15, 28 and 43 kg at 3.5, 5.25 and 6.1 cows/ha, respectively (P<0.05). Cows stocked at 3.5/ha recovered liveweight during the experiment, but liveweight losses continued for cows at 5.25 and 6.1 cows/ha. Rhodes grass management should aim to harvest a high proportion of leaf, a result which was achieved under a wide range of stocking rates in this experiment. Reducing the frequency and total volume of irrigation resulted in reduced levels of soil water and pasture yield, but did not affect milk production until the final 3 weeks of the experiment (May). The stocking rate of 3.5 cows/ha allowed cows to maintain body weight and appears optimal for these pastures. The ability of the pastures to maintain DM yield with half the applied water input demonstrates that efficiencies may be gained by closer monitoring of soil and pasture production in autumn rather than the normal practice of fortnightly watering. This, combined with the longer grazing interval of 6 weeks and a stocking rate of 3.5 cows/ha, provided the most efficient use of the tropical grass pasture resource in late summer and autumn.

Two experiments assessed grazing management strategies for irrigated and nitrogen- fertilised rhodes grass (Chloris gayana) cv. Callide pasture. In Experiment 1, the 4 treatments were: (i) open grazing of the entire paddock on a 2-week cycle (Open); (ii) grazing on a 2-week, daily strip-grazing rotation (2); (iii) a 4-week, daily strip-grazing rotation (4); and (iv) a 6-week, daily strip-grazing rotation (6). For treatments (ii), (iii) and (iv), pasture was allocated at 15 kg green leaf dry matter (DM)/cow/d and grass was mulched to a stubble height of 10 cm after grazing. Stocking rates attained were 1.7, 3.7, 3.5 and 3.4 cows/ha for Treatments (i), (ii), (iii) and (iv), respectively. In Experiment 2, pastures were grazed on a 2-paddock 2-weekly rotation [Open (O) and Open + mulching (OM)] or 28-day rotational cycle without mulching (28) or with mulching (28M) after grazing.There were substantial differences in yield of pasture on offer to cows with different grazing management, but total leaf yield appeared similar, with a mean growth rate of 42 kgDM/ha/d. There were small, but significant differences in pasture quality between treatments, though pastures in unmulched paddocks had lower crude protein and higher NDF levels than those in mulched paddocks. Animals selected strongly for leaf (78%) across all treatments, though stem content increased from 13% in February to 25% in April. Milk yield was not altered by age of regrowth or open grazing, but was reduced (P<0.05) where rotationally grazed pastures were not mulched. This was attributed to the presence of stem impeding access to leaf when pastures were grazed in narrow strips.The results demonstrate that intensive management of Callide rhodes grass pastures can support a stocking rate up to 3.7 cows/ha, but there are only small animal production differences associated with radically different grazing management routines. Additional operational costs associated with more intensive management of pastures ranged from AUD30 to AUD80/ha for the 18 weeks of the experiment compared with open grazing. In Experiment 2, net marginal returns were AUD0, -38, -145 and 66/ha for the four treatments O, OM, 28 and 28M, respectively.

Pasture quality in the subtropics declines in the autumn as fibre content of the leaf increases and leaf content of the pasture declines (Cowan et al. 1993). Tropical pastures managed to allow animals to select leaf, result in low utilisation. However the combination of high stocking rates and rotational grazing has supported higher milk production/ha, with minimal decline in per cow yield (Ehrlich et al. 1994). This experiment evaluated the effects of strip grazing and mulching on the pasture quality and milk production of tropical grass pastures. Callide Rhodes grass (Chloris gayana cv. Callide) pasture, established 11 years previously, was divided into 2 replicate areas, each of which was subdivided into 4, 0.72 ha paddocks. These paddocks were allocated at random to the 4 treatments: (i) open grazing of the entire paddock (0), (ii) open grazing plus mulching once every 4 weeks (O+m), (iii) grazing on a 4 week rotation using daily strip grazing with a backing fence and allocating l/28 of the total area per day (sg), (iv) as for sg but with twice weekly mulching of grazed strips (sg+m). For treatments O+m and sg+m pastures were mulched to 10 cm height after grazing. Stocking rate was 3.5 cows/ha for all treatments. All pastures received 300 kg N/ha over the season and were irrigated to avoid moisture stress. Five Holstein-Friesian cows grazed each treatment, alternating weekly between pasture replicates. Cows received 5 kg of concentrate daily. Mulching was used to precondition pastures during November and December and the grazing experiment was conducted for 16 weeks from 3 January 1994. Leaf protein and leaf percentage were higher and dry matter yield was lower in mulched pastures (Table 1). Milk yield/cow was similar for 0, O+m and sg treatments. Milk yield was increased in the sg+m treatment.

With high stocking rates and intensive management of tropical grasses in a sub-tropical dairying system (Ehrlich et al. 1994), part of the summer grass area could be replaced with crop legumes. Zero tillage technology, used on areas where cultivation is not sustainable, allows a higher quality feed to be offered in autumn. The aim of this experiment was to ascertain the regrowth potential of soybeans. The soybean variety Leichhardt was oversown into a grass pasture and individual plots were grazed starting at 4 weeks after planting and thereafter at 10 day intervals. Preand postgrazing yields were measured as well as regrowth yield to late autumn (17 May). Leaf and stem yield measurements were taken at every sampling. Total yield was estimated using the sum of pre-grazing yield plus regrowth. Two 400m2 paddocks were planted to soybeans on 9 February 1995 using a minimal till planter with 300 mm rows to give a final population of 225 000 plants/ha. Grass was controlled with glyphosphate at 2L/ha, 24 hours before planting. The 2 paddocks were each divided into four 20 by 50 metre plots. Five yearling Holstein-Friesian steers were introduced into the allocated plot at 0830 hours and removed the following day when the majority of leaf had been consumed. Plots were irrigated on 1 occasion to prevent plant death. Yields were restricted because of the late planting date and low rainfall during growth. Grazed plots produced similar total dry matter yields (P>O.O5) regardless of the time of grazing, though regrowth potential declined with time. The ungrazed plot produced 1357 kg DM/ha (PcO.01). Leaf percentage was high up to 60 days after planting (average 6 1%) and then declined to an average of 46% for the remaining sample times. Leaf protein declined up to flowering (Table 1) but increased at pod set to 20.6% (PcO.05). Leaf organic matter digestibility and neutral detergent fibre were initially 76 and 23% respectively at the first sampling and averaged 69 and 34% for samplings in the vegetative stage and 74 and 38% in the pod fill stage respectively. Flowering commenced at 2 May sampling and was virtually completed by 11 May with pods starting to fill at the last sampling on 17 May.

A group of 40 Holstein-Fresian cows grazing tropical pastures were supplemented from 14 days after calving with a grain-based concentrate containing 15% protein. Concentrate was given at nil, 2, 4, 6, and 8 kg/cow. day fed once daily after morning milking, and 4, 6, and 8 kg/cow.day in 2 equal feeds, after morning milking and before evening milking. The experimental period was 250 days for cows fed once daily and 150 days for those fed twice daily. Over 250 days of lactation, the milk yield of cows fed once daily was significantly increased with increasing grain feeding, from 12.8 kg/day for the nil group t o 20 kg/day for the 8 kg group. Milkfat percentage was lower (P<0.05) for cows given 8 kg grain concentrate daily than for those given 2-4 kg, and total fat yield increased (P<0.1) with up to 4kg/cow.day. Protein percentages were similar across treatments, and protein yield increased (P<0.05) with grain level. Lactose percentage was increased (P<0.05) with concentrate feeding, and lactose yield increased (P<0.05) with increasing concentrate level. Fat-corrected milk (FCM) increased (P<0.05) from 3046 kg at nil concentrate to 4465 kg at 8 kg/cow. day. Over the first 150 days of lactation, milk yield increased from 19.5 kg/day for cows fed once daily to 21.7kg/day for those fed twice daily. Milkfat and protein percentages were similar. Greatest responses to twice-daily feeding occurred at 6 kg concentrate/cow.day. It was concluded that total milk yield increased linearly to 8 kg concentrate/cow.day, but FCM yield was at a maximum at 6 kg concentrate1cow.day. There were advantages in feeding 6 kg concentrate twice daily.

Palm kernel expeller (PKE) is a by product of processing the Oil palm tree (Elaeis quineensis) and is the solid residue left after kernel oil has been extracted. The high oil content of PKE, means it can act as an energy dense source of concentrate so this experiment aimed to compare PKE with grain based concentrates in dairy cow rations. Thirty five cows that calved in April-May 1991 were blocked according to parity, milk yield and milkfat %. Cows were randomly allocated to 5 treatments: 5 kg grain concentrate/day (5G), 4 kg grain concentrate plus 1 kg PKE (4G:l PIE), 3 kg grain concentrate plus 2 kg PKE (3G:2 PKE), 2 kg grain concentrate plus 3 kg PKE (2G:3 PKE), 5 kg grain concentrate plus 1 kg PKE (5G:l PIE). The grain concentrate consisted of 90% barley grain (11.9% crude protein (CP), 2.1% fat) and 10% cottonseed meal (44.4% CP, 4.1% fat). The experiment was conducted over 4 weeks in September-October 1991. Cows took 2 weeks to adapt to their rations. Milk yield and composition data were analysed over the subsequent 2 weeks. Cows rotationally grazed 10 ha of clover-rye grass pastures during the day (1400 kg dry matter (DM)/ha on offer) and at night were offered maize silage at 9 kg DM and restricted to a feed pad without pasture. Cows were offered their supplement once a day after the morning milking in individual stalls and reject feeds were weighed daily. The PKE contained 16.3% CP, 62.1% neutral detergent fibre (NDF), 14.2% fat, 0.25% Ca, 0.57% P and 26.5 ppm Cu. Maize silage was 8.8% CP, 59.6% NDF, 0.30% Ca and 0.38% P and pasture was 21.9% CP, 25.3% NDF, 1 .Ol% Ca and 0.44% P on a dry matter basis. Feeding the PKE as a substitute for the grain concentrate increased milkfat % and 4% fat corrected milk (FCM) yield (P c 0.01) when fed at 2 or 3 kg/day (Table 1). It was concluded that PKE could replace grain concentrate in rations up to 2-3 kg/day with no deleterious effect on milk yield.

In a 2-part preliminary experiment, groups of 6 and 9 Holstein-Friesian cows in early t o mid lactation were unsupplemented or supplemented with either 3 kg cracked sorghum grain or 3 kg whole cotton seed on a base pasture of irrigated pangola grass for 12 weeks or oats for 12 weeks. The stocking rate was 5 cows/ha. Supplementation did not affect milk yield or composition. In a second experiment a group of 20 Holstein- Friesian cows in early to mid lactation grazed on a base pasture of subterranean clover at a stocking rate of 4 or 6 cows/ha a n d w e r e either unsupplemented or supplemented with 3 kg of whole cotton seed (WCS) over 12 weeks. Milk yield averaged 20.3 kg/cow.day and there were no significant effects on milk yield or composition. We suggest the lack of a significant milk yield response was due to a high substitution rate of WCS for pasture, associated with an oil content in the diet of 7.1 % of dry matter.