Context Commercial ducks often experience high temperature in summer and nutritional strategies could help them cope under these conditions. Aims To assess the effects of water and feed supplements on the growth performance of Pekin ducks exposed to high ambient temperature. Methods Commercial Pekin ducks were supplemented with betaine in feed, betaine or vitamin C in water or had feed withdrawn for 9 h/day or provided with water alone, during Weeks 5 and 6 of age. Water was supplemented with an ‘in house’ electrolyte formulation and betaine in Week 6, only. The treatments were applied to two strains, the Cherry Valley (CV) and a commercial line selected from the CV strain for higher breast muscle yield identified as CVP2. On Days 29–41 of age, shed temperature was increased to 30.5°C for 9 h (08:30–17:30) and then returned to 22.7°C for the remainder of the day. Individual liveweights of ducks were measured on Day 28, Day 35 and Day 41 of age. Feed intake and water consumption were measured over Days 14–28, Days 29–35, and Days 36–41. On Day 41, one male and one female from each pen, were weighed, euthanised and the total breast muscle was removed and weighed. Key results In Week 5, all supplements supported a higher LWG, although this was limited to 4.3–6.3%, with no effects on feed intake or feed to gain ratio. In Week 6, these same supplements provided no benefit and, in fact, vitamin C had a negative effect (−4.7%) on LWG. In Week 6, the electrolyte + betaine improved LWG by 17.1%, with no effects on feed intake or feed to gain ratio. The supplements had no effects on breast muscle weight or yields. The CVP2 selected line had a substantially higher LWG, with nearly all this being due to the 15.8% higher gain seen in males, as LWG of females was similar for both strains. Conclusions Using electrolytes as a nutritional intervention can help Pekin ducks cope with adverse high temperature and should be evaluated under more extreme high-temperature challenges. Implications Water electrolyte supplementation can support Pekin duck performance under high-temperature challenge.

Context Minimal information is available as to the optimal stocking density and light intensity for best performance of commercial ducks. Aims To investigate the effects of stocking density and light intensity on commercial Pekin duck production. Methods Cherry Valley and Grimaud Freres Pekin ducks were housed at stocking densities of 4.4 (low), 5.2 (medium) and 6 (high) birds/m2 and from 8 to 41 days of age at 6 lux (low) and 45 lux (moderate) light intensities. On Days 14, 28, and 41 of age all ducks were individually weighed, and pen feed and water intakes recorded. On Day 41, one male and female from each pen was euthanised and breast muscle weight determined. At Weeks 3 and 4 all birds were individually examined, for extent of feather and skin damage. Key results In all weeks, the Grimaud Freres birds had higher liveweight than Cherry Valley birds. Only at Week 4, birds under low light had higher liveweight than those at moderate light intensity. At Week 4, birds at low densities had higher liveweight, while at Week 6 birds at low and medium stocking densities had higher liveweight than those at high stocking densities. At Week 4, the feed to gain ratio was poorer when birds were housed in moderate light intensity. The stocking density had no effect on the feed to gain ratio. Light and stocking density had no effect on any of the breast muscle measures. In Week 4, the birds housed at medium density had a higher feather and skin damage. At Week 3, more damage was directed to the wings than the thigh regions. There was a higher incidence of damage in some pens irrespective of treatments. Conclusions The medium stocking density supported performance equivalent to that at low density and better than at the high density. Ideally the density recommendation should be based on ‘weight density’ (kg/m2) and the current results indicate this was between 16.49 and 19.0 kg/m2. The birds performed similarly under both light intensities. Implications The suitable stocking density for efficient production is 16.5–19.0 kg/m2 and housing at 6 or 45 lux had no influence on performance. Best performance and breast muscle yield was from the Grimaud Freres strain.

Normal performance can be achieved by feeding low crude protein (LCP) finisher diets when supplemented with adequate essential amino acids. The question remains as to the adequacy of LCP diets under high temperature stress. The performance of meat chickens was determined when fed an LCP finisher diet while exposed to an acute (AT) or chronic (CT) thermal challenge or thermo-neutral conditions (TN). Day-old male Ross 308 chicks (N =360) were reared in floor pens until d 28 and then transferred to metabolism cages (5 birds/cage) and housed in environmentally controlled metabolism rooms, maintained at 20 degrees C until d 38 of age. In room 1, birds were exposed to CT, 28 degrees C for 5 h/d on d 38-42 (22 cages). Room 2 was maintained at 20 degrees C on d 38-39 and then increased rapidly to 30-32 degrees C for 3 h/d (AT) on d 40-42 (22 cages). The birds in the remaining 22 cages of room 2, were removed 1 h before the ATand held in a third room at TN and returned to room 2 when the temperature had returned to 20 degrees C. For each temperature treatment equal number of cages were fed either a control finisher (20.3 % protein) or LCP diet (17% protein) on d 28-42 of age. Individual bodyweights and pen feed intake were determined on d 28 and d 38 (TN and CT) and d 40 (TN and AT) and all on d 42. Total excreta were collected d 40-42 to determine AME, AMEn and % protein retention. On d 43 breast weight and the % breast muscle yield were determined. Bird behaviours were recorded over d 38-42 of age. The AT resulted in a 32.3 % reduced LWG, had no effect on feed intake but FCR was 22.3 % poorer. The CT had no adverse effects on bird performance. The diet CP had no effects on performance under either challenge. The thermal challenges or diet CP had no effects on breast muscle yields, AME, AMEn or % protein retention. Depending on the thermal condition birds spent 73-90 % of their time crouching. The absence of any adverse effects of the CT suggest it was of moderate severity and birds coped. However, based on the reduced performance, mortality and removals, and high % of birds panting, the AT caused 'severe' to 'life-threating' conditions. The reduction in CP had no consequence under these thermal conditions.

The effects of supplying water with an 'in-house' or commercial electrolyte formulation for 3 d during severe heat stress on performance and meat quality of meat chickens was investigated. At day 35 of age, Cobb-500 meat chickens (N = 22,11 of each sex/treatment) were allocated to 36 floor pens (12 pens/ treatment). The three treatments were, 1: (Control) tap water; 2: 'In-house' electrolytes at 416.4 g/100 L water; 3: commercial electrolyte(-)at 200 g/100 L water. The treatments were applied from 16:00 h on d 39 to 17:00 h on d 42 of age. On d 40-42 the ambient temperature remained at 20-22 degrees C (17:00-08:00 h), then gradually over 08:00-12:00 h increased to a maximum of 32 degrees C where it remained until 15:00 h, and then reduced to 20-22 degrees C at 17:00 h. The severity of heat stress was assessed using the following Thermal-Humidity Index (THI): THI (%) = 0.8T(db) + RH (Tdb-14.3)/100 + 46.3. At 18:30 h on d 42 birds were loaded and transported to the processing plant and held in lairage overnight. Individual body weights, pen feed and water intakes were recorded at the start and end of the supplementations. In the morning, at the processing plant birds were weighed before and after evisceration with carcasses then stored overnight at 2 degrees C and the following morning breast muscle meat quality traits were determined. Based on the THI values, at peak temperature, birds suffered 'severe thermal discomfort'. Liveweight was improved in both sexes treated with the 'in-house' electrolyte but only males benefited on the commercial electrolyte. The 'in-house' electrolyte improved feed efficiency. There were no effects on losses during transport and lairage or breast muscle yield and meat quality. Behavioural observations indicated that birds spent 74-81 percent of their time crouching on the litter. Temperature beneath crouching birds was on average 4.4 degrees C higher than the ambient temperature and could be adding to the thermal challenge experienced by the birds and warrants further investigation. When supplied during periods of high temperature, electrolyte water supplementation alleviates in part the performance losses.

In Australia, free-range pullets are typically reared indoors, which may hinder later adjustment to outdoor access. Rearing enrichments could optimise pullet development. Hy-Line Brown® chicks (n = 1700) were reared indoors across 16 weeks with 3 enrichment treatments: (1) a standard control; (2) novel objects (novelty) provided weekly or (3) perching structures (structural) provided. All pullets were weighed at 5, 8, 12, and 16 weeks old. Pullets (n = 87) were tested in a novel arena at 9 weeks and manual restraint (n = 90) at 16 weeks. At 15 weeks, lymphoid organs were extracted and weighed from 90 pullets. Pullets were transferred to the free-range facility at 16 weeks and housed in 9 identical pens within rearing treatments. Hens perching were counted via video recordings across the first week. The structural pullets had the highest relative adrenal weights (p = 0.03) but differences may not have been biologically relevant. Structural hens perched less than the novelty hens in the layer facility (p = 0.02). There were no other consistent rearing treatment differences. The rearing environments had minimal effects on pullet behaviour and welfare, but data from the adult hens did show some longer-term welfare impacts.

Enrichments during pullet rearing may improve adaptation and welfare of hens as they move from indoor rearing to a free-range system. Individual variation in outdoor ranging may also affect welfare. This study assessed the effects of rearing enrichments and an imposed environmental stressor on hen welfare and egg quality along with the association of welfare with ranging. Hy-Line Brown® chicks (n = 1,386) were reared indoors until 16 weeks with 3 enrichment treatments including a “control” group with standard floor litter, a “novelty” group that received novel objects that were changed weekly, and a “structural” group with H-shaped perching structures. Pullets were then moved to a free-range system with three replicates of each rearing treatment. Daily ranging was individually tracked from 25 to 64 weeks via radiofrequency identification technology. Individual hen welfare assessments were performed at 25, 33, 43, 56, and 64 weeks and correlated with ranging time prior to these dates. At 44 weeks, the range area was reduced by 80% for 11 days to induce stress. Changes in ranging behavior, albumen corticosterone concentrations and egg quality were evaluated. GLMMs showed significant interactions between hen age and rearing treatment for live weight, number of comb wounds, plumage coverage, and toenail length (all P ≤ 0.003), with the enriched hens showing more consistent live weight at the later ages, fewer comb wounds at 33 weeks, and better plumage coverage at the later ages, whereas the structural hens had shorter toenails as age increased. Plumage coverage showed a positive relationship with range use across most age points (P < 0.0001). Hens reduced ranging time following the imposed stressor but increased their number of visits with the lowest increase by the structural hens (P = 0.03). Significant interactions between rearing treatment and stressor for albumen corticosterone concentrations showed the structural hens decreased concentrations immediately post-stress, but the control and novelty groups increased (P < 0.006). The stressor increased or decreased values of most egg quality parameters across all rearing groups (all P ≤ 0.02). Overall, provision of rearing enrichments and greater range use may have positive impacts on hen welfare.

Within Australia, free-range systems are prevalent, but pullets destined for range access are reared indoors. This mismatch between rearing and layer housing may hinder adaptation to the free-range environment. Rearing enrichments could enhance pullet development. A total of 1,386 Hy-Line Brown® chicks were reared inside an experimental facility across 16 weeks with 3 enrichment treatments including (1) a control group with standard floor-housing, (2) a novelty group providing novel objects that changed weekly (“novelty” hens), and (3) a structural group with custom-designed H-shaped structures including opaque sides (“structural” hens). At 16 weeks of age, all pullets were leg-banded with microchips and moved to an experimental free-range system with 9 identical pens (n = 3/rearing treatment). From 25 to 64 weeks, individual hen daily ranging behavior was tracked via radio-frequency identification technology and grouped into 6 age periods per rearing treatment. Video footage was used to count the number of hens at different distances on the range for the first 14 days of access, and eggs were assessed for albumen corticosterone concentrations 4 days prior to (n = 450) and 1 week after first range access (n = 450). Across most age periods, the structural hens spent the most time ranging (P ≤ 0.01), the novelty hens showed the fewest number of visits to the range (P < 0.0001), and both enriched hen groups had the longest maximum visit durations (P ≤ 0.02). Range use increased with age across all treatments with only 3% of hens never going outside. All hens were initially slow to use the range area with fewer novelty hens venturing farther onto the range (P ≤ 0.03). The structural hens had higher albumen corticosterone concentrations and variance (both P ≤ 0.004) prior to range access. All hens showed an increase in albumen corticosterone following the first week of range access resulting in no differences between rearing treatments in means (P = 0.92) and variance (P = 0.63). Different enrichments have differing impacts on ranging behavior, but further research is needed to understand the mechanisms of effects, with differences in brain lateralization a potential hypothesis to be tested.

The consequences of high ambient temperature for broiler chickens collectively results in poorer productivity, prostration and even death. As they approach processing weight, broilers are particularly sensitive to heat stress as they produce large amounts of metabolic heat. Transport from farm to the processing site is a stress for broilers. So, the combination of high ambient temperature prior to transport and the stress associated with transport to processing have unwanted effects on broiler performance and meat quality.In two experiments (summer and winter) the effect of supplementing the water of Ross-308 broiler chickens with electrolytes, with or without betaine for 2 days before processing, on performance and breast muscle meat quality were investigated. In the summer experiment broilers were exposed to a cyclic high temperature protocol over the two days (9h at 28–29°C and 14h at 22–24°C). In the winter experiment the shed temperature ranged between 14 and 18°C. The growth performance of birds during supplementation and then the breast muscle meat quality 24–72h post-mortem were determined.In both experiments betaine had no effect on any performance or meat quality measure and the electrolyte supplementation had no effect on growth performance. In the summer experiment, electrolyte supplementation had significant effects on some measures of meat quality. Breast muscle from supplemented birds had lower 24h post-mortem pH and based on meat ‘lightness’, lower levels of PSE meat. The 72h drip loss was significantly lower in meat from birds that had been supplemented with electrolytes. The electrolyte supplements had no effects on meat ‘redness’ or ‘yellowness’, on shear force or cooking losses.In the winter experiment, the electrolyte supplementation had no effect on growth performance or breast muscle meat quality. In this experiment, the average shed temperature was approximately 16°C with peak values of approximately 18°C. The growth rate of the birds was approximately 40% higher than that identified in industry performance standards for the Ross-308 strain. The data suggest that the temperature for best performance of the Ross-308 is lower than the 18–24°C currently accepted as ideal.In all experiments there were significant effects of bird gender on performance and meat quality measures.While electrolyte supplementation supported improvements in meat quality during periods of moderately high ambient temperature, the commercial benefit of these would need to be assessed. The value of electrolyte supplementation is likely to be more substantial when broiler chickens experience heat wave conditions with temperatures > 32°C, but this remains to be evaluated.

Animal Production Science (continuing Australian Journal of Experimental Agriculture) publishes original research into applied agriculture including animal production, animal-plant interactions, pasture and fodder crops, field crops, extension and horticulture

Free-range laying hen systems are increasing within Australia. The pullets for these systems are typically reared indoors before being provided first range access around 21 to 26 weeks of age. Thus, the rearing and laying environments are disparate and hens may not adapt well to free-range housing. In this study, we reared 290 Hy-Line® Brown day-old chicks divided into two rooms each with feed, water and litter. In the enriched room, multiple structural, manipulable, visual and auditory stimuli were also provided from 4 to 21 days, the non-enriched room had no additional objects or stimuli. Pullets were transferred to the laying facility at 12 weeks of age and divided into six pens (three enriched-reared, three non-enriched-reared) with identical indoor resources and outdoor range area. All birds were first provided range access at 21 weeks of age. Video observations of natural disturbance behaviours on the range at 22 to 23 and 33 to 34 weeks of age showed no differences in frequency of disturbance occurrences between treatment groups (P=0.09) but a decrease in disturbance occurrences over time (P<0.0001). Radio-frequency identification tracking of individually tagged birds from 21 to 37 weeks of age showed enriched birds on average, spent less time on the range each day (P<0.04) but with a higher number of range visits than non-enriched birds from 21 to 24 weeks of age (P=0.01). Enriched birds accessed the range on more days (P=0.03) but over time, most birds in both treatment groups accessed the range daily. Basic external health scoring showed minimal differences between treatment groups with most birds in visibly good condition. At 38 weeks of age all birds were locked inside for 2 days and from 40 to 42 weeks of age the outdoor range was reduced to 20% of its original size to simulate stressful events. The eggs from non-enriched birds had higher corticosterone concentrations following lock-in and 2 weeks following range reduction compared with the concentrations within eggs from enriched birds (P<0.0001). Correspondingly, the enriched hens showing a greater increase in the number of visits following range area reduction compared to non-enriched hens (P=0.02). Only one rearing room per treatment was used but these preliminary data indicate 3 weeks of early enrichment had some long-term effects on hen ranging behaviour and enhanced hen's adaptability to environmental stressors.

Free-range laying hen systems are increasing within Australia and research is needed to determine optimal outdoor stocking densities. Six small (n=150 hens) experimental flocks of ISA Brown laying hens were housed with access to ranges simulating one of three outdoor stocking densities with two pen replicates per density: 2000 hens/ha, 10 000 hens/ha or 20 000 hens/ha. Birds were provided daily range access from 21 to 36 weeks of age and the range usage of 50% of hens was tracked using radio-frequency identification technology. Throughout the study, basic external health assessments following a modified version of the Welfare Quality® protocol showed most birds were in visibly good condition (although keel damage was increasingly present with age) with few differences between stocking densities. Toenail length at 36 weeks of age was negatively correlated with hours spent ranging for all pens of birds (all r⩾−0.23, P⩽0.04). At 23 weeks of age, there were no differences between outdoor stocking densities in albumen corticosterone concentrations (P=0.44). At 35 weeks of age, density effects were significant (P<0.001) where the eggs from hens in the highest outdoor stocking density showed the highest albumen corticosterone concentrations, although eggs from hens in the 10 000 hens/ha density showed the lowest concentrations (P<0.017). Behavioural observations of hens both on the range and indoors showed more dust bathing and foraging (scratching followed by ground-pecking) was performed outdoors, but more resting indoors (all P<0.001). Hens from the 2000 hens/ha densities showed the least foraging on the range but the most resting outdoors, with hens from the 20 000 hens/ha densities showing the least amount of resting outdoors (all P<0.017). Proportions of dust bathing outdoors tended to differ between the stocking densities (P=0.08). For each of the health and behavioural measures there were differences between pen replicates within stocking densities. These data show outdoor stocking density has some effects on hen welfare, and it appears that consideration of both individual and group-level behaviour is necessary when developing optimal stocking density guidelines and free-range system management practices.

Two experiments tested the tolerance of steers (Bos taurus) to sorghum ergot (Claviceps africana) during cooler months in south-east Queensland. Sorghum grain containing 2.8% ergot and 28 mg/kg ergot alkaloids (84% dihydroergosine, 10% dihydroelymoclavine, 6% festuclavine) was incorporated into feedlot rations. In a previous study in summer–autumn, ergot (1.1–4.4 mg alkaloids/kg ration) severely reduced performance in steers when the temperature–humidity index (THI; dry bulb temperature °C + 0.36 dew-point temperature °C + 41.2) was ~70, whereas a THI of ~79 was tolerated by steers fed ergot-free rations. Experiment 1 was conducted in winter–spring, with rations containing 0, 2.8, 5.6, 8.2 or 11.2 mg ergot alkaloids/kg ration. All ergot inclusions depressed feed intake (14% average reduction) and growth rate (34% average reduction), even when the weekly average daily THI was less than 65. Rectal temperatures were occasionally elevated in ergot-fed steers (P < 0.05), primarily when the THI exceeded ~65. All ergot inclusions depressed plasma prolactin concentrations in steers. Experiment 2 was predominantly carried out in winter, with weekly average daily THI <65 throughout the experiment. Rations containing 0, 0.28, 0.55 or 1.1 mg ergot alkaloids/kg were fed for 4 weeks but produced no significant effect on feed intakes and growth rates of steers. Alkaloid concentrations were then changed to 0, 2.1, 4.3 and 1.1 mg/kg, respectively. Subsequently, feed intakes declined by 17.5% (P < 0.05), and growth rates by 28% (P > 0.05) in the group receiving 4.3 mg/kg alkaloid, compared with Controls. Plasma prolactin concentrations were depressed, relative to the Controls, by dietary alkaloid inclusion greater than 1.1 mg/kg, with alkaloid intake of 4.3 mg/kg causing the greatest reduction (P < 0.05). Cattle performance in these studies shows steers can tolerate up to ~2 mg ergot alkaloid/kg (0.2% ergot) in feedlot rations under low THI conditions (< ~60–65), but previous findings indicate a much lower threshold will apply at higher THI (>65).

Free-range systems are increasing in popularity as outdoor access is perceived to improve hen welfare, but radio-frequency identification tracking of individuals shows not all hens access the range daily with some hens never going outside. The individual variation in range use may be correlated with individual differences in fear and coping styles. In this study, tests of tonic immobility, manual restraint (coupled with plasma corticosterone responses) and open field were applied to ISA Brown hens (Gallus gallus domesticus: n = 104) at 37-39 weeks of age. Focal hens were selected as categorised into three different range access groups based on the percentage of available days across the trial period that they went outdoors: indoor-preferring (accessed the range on 0-10% of available days), moderate-outdoor (accessed the range on 30-60% of available days), and outdoor-preferring (accessed the range on 100% of available days). The indoor-preferring hens produced fewer vocalisations during manual restraint compared to the moderate-outdoor and outdoor-preferring hens (P= 0.004) and tended to be slower to vocalise (P= 0.08) but no differences were found in latency to first struggle (P= 0.55), number of struggles (P= 0.44) or plasma corticosterone responses (P= 0.82). During the open field tests, the indoor-preferring and moderate outdoor hens showed longer latencies to move and fewer squares were crossed compared to outdoor preferring hens (P <= 0.009) but no differences were found in latency to first vocalise (P= 0.72) and total number of vocalisations (P= 0.91). There were no differences between range access groups in duration of tonic immobility (P = 0.14). These results show indoor-preferring hens have elevated fear levels, and a possible behavioural indication of a different coping style compared to outdoor-preferring hens, but the inconsistent results within the moderate-outdoor range access group warrant further investigation. (C) 2016 Elsevier B.V. All rights reserved.

Animal Production Science (continuing Australian Journal of Experimental Agriculture) publishes original research into applied agriculture including animal production, animal-plant interactions, pasture and fodder crops, field crops, extension and horticulture

Animal Production Science (continuing Australian Journal of Experimental Agriculture) publishes original research into applied agriculture including animal production, animal-plant interactions, pasture and fodder crops, field crops, extension and horticulture

Research in any area of animal production can provide the opportunity to change how the system operates and is managed. The reliance on having to wean lactating sows to re-mate them has limited the commercial options for sow management. The desire to limit lactation length to maximise the litters per sow per year concurrently creates major challenges for such-aged piglets weaned abruptly. These issues are discussed in the review. This management system also fails to recognise that sows have the potential to spontaneously ovulate in lactation even when housed in farrowing crates. Inhibition of luteinising hormone release is the basis of lactational anoestrus with the suckling stimulus providing the strongest afferent signal to this inhibitory system. Any management strategy that reduces this inhibition has the potential to trigger lactational oestrus. In this review, group housing of sows, boar exposure and intermittent suckling are identified as strong stimuli that can promote lactational oestrus. Removing the need to wean sows to mate them offers further opportunities to change the way lactating sows are managed. One option is a two-stage lactation system in which the sows are housed in farrowing crates for the first 10–14 days and then moved to group accommodation for the remainder of lactation. This system provides welfare benefits for the litter in the early stage of lactation and then the benefits of less confinement for the sows in later lactation. Group lactation would also lend itself to the implementation of stimuli to assist the mating of sows in lactation, such as piglet separation and/or boar exposure. It also accommodates the mating of sows that spontaneously ovulate in lactation. Removing the need to wean sows to re-mate them provides the opportunity to increase weaning age and implement a gradual weaning, helping to attenuate the post-weaning growth check and potentially limiting antimicrobial use in weaner pigs.

Gilt progeny are born lighter, have lower weaning weights and require more medication throughout their life time than do sow progeny. Therefore, strategies to improve their post-weaning performance are of importance to pork producers. Dietary fatty acids have been shown to be potent modulators of physiological processes. Studies in other species have reported that dietary fatty acids affect in utero development, cognitive behaviour, immune system function, carcass composition as well as feed efficiency of offspring. However, little information is available that details their use in gilt progeny and when fed throughout their lifetime. In the present study, two experiments were conducted to investigate the effects of feeding three different types of fat to gilts and their progeny on the growth, body composition and performance post-weaning. Diets were enriched with either saturated fatty acids (SFA; tallow), or n-3 (fish-oil extracts) or n-6 (safflower oil) polyunsaturated fatty acids (PUFA) and were fed to gilts through gestation and to their progeny post-weaning. In Experiment 2, half of the female progeny from n-3 and n-6 PUFA litters were fed SFA post-weaning. For both studies, there was no significant difference in weaning bodyweights. However, in Experiment 1, pigs fed n-6 PUFA diets post-weaning were significantly lighter 7 days post-weaning than were pigs fed SFA- and n-3 PUFA-enriched diets. Despite feed intake of n-6 PUFA-fed pigs becoming comparable to that of the other groups during the finisher period, bodyweight for this group remained significantly lower than that of the other groups at the conclusion of the experiment. No effect of dietary fatty acid type on the carcass composition of finisher pigs, as determined by computed tomography, was found. The results of Experiment 2 showed that feeding pigs n-6 PUFA diets post-weaning through to slaughter significantly compromised their growth, being in agreement with those from Experiment 1. Feed consumption for this group was significantly less during the post-weaning and the finisher periods. However, pigs from n-6 PUFA litters that were fed SFA diets post-weaning showed no compromise in growth and performance and were comparable to pigs from the other treatment groups. During the grower and finisher periods, pigs fed n-6 PUFA diets had a significantly higher rate of mortality that was as much as 13 times that of pigs fed SFA diets. Pigs from n-6 PUFA litters that were fed SFA diets post-weaning were not affected in this manner. The results of the current study showed that feeding diets enriched with n-6 PUFA to pigs significantly compromised their growth and performance and that this fatty acid type may also have negative health effects with prolonged consumption. The data suggested that the type of fatty acid used in pig diets may be an important consideration for nutritionists when formulating diets to optimise post-weaning growth and performance.

Three studies investigated the effect of feeding strategy on production performance and endocrine status of growing pigs. For Experiment 1, 20 entire male pigs (70.0 ± 4.6 kg) were allocated randomly to individual pens in one of four climate-controlled rooms. Pigs were fed for 23 days either ad libitum or entrained to feed bi-phasically for two 90-min periods. For Experiment 2, 20 entire male pigs (41.2 ± 3.5 kg) were housed as per Experiment 1. Pigs were fed for 49 days either ad libitum or fed bi-phasically for two 60-min periods. For Experiment 3, 100 female pigs (66.1 ± 3.5 kg) were randomly allocated to individual pens within a commercial piggery and fed for 42 days either ad libitum or bi-phasically for two 60-min periods. Ear vein catheters were inserted into 10 pigs from each group and hourly blood samples were collected for 24 h in Experiments 1 and 2 and for 11 h in Experiment 3. Plasma insulin, non-esterified fatty acid and glucose concentrations were determined in Experiments 1 and 2, and glucose and insulin concentrations in Experiment 3. Feed intake and performance were recorded in all experiments and carcass composition was assessed by computed tomography for Experiment 2. There were no differences in final liveweight between the two treatment groups for all experiments. Pigs fed for two 90-min periods (Experiment 1) showed no difference in feed intake when compared with feeding ad libitum. Pigs in Experiment 2 fed for two 60-min intervals consumed 2.49 kg/pig.day compared with those fed ad libitum that consumed 2.68 kg/day (P = 0.057). In Experiment 3, pigs fed twice daily consumed 2.82 kg/pig.day compared with 2.91 kg/pig.day in ad libitum-fed pigs (P = 0.051). Bi-phasic fed pigs in Experiment 2 had improved (P < 0.05) feed conversion efficiency compared with pigs fed ad libitum. For all experiments, there was no difference in plasma glucose concentrations between the two treatments. In all three experiments, the circulating insulin concentrations for pigs fed ad libitum remained at a constant level throughout the sampling period. However, plasma insulin concentrations for the bi-phasic fed pigs significantly increased ~1 h after both feeding periods during all three experiments. Insulin secretion of pigs fed for two 90-min periods differed from that of pigs fed for two 60-min periods. Plasma insulin concentration increased five-fold following feeding for 60 min, compared with that in pigs fed for 90 min, which increased two-fold. Bi-phasic-fed pigs from Experiment 2 had reduced (P < 0.05) total carcass fat and significantly increased muscle when compared with pigs fed ad libitum. The data showed that feeding pigs at two succinct periods aligned insulin secretion to the time of feeding. Pigs fed for 60 min, unlike those fed for 90-min intervals, had reduced feed intake in comparison to those fed ad libitum. This may suggest that the duration of the feeding bout is important for this response and this may in turn influence both energy balance and the way energy is partitioned.

The effect of ergot (Claviceps africana) in naturally infected sorghum was assessed in feedlot rations. Thirty-two Hereford steers (Bos taurus) in individual pens with access to shade were adapted to feedlot conditions and then offered one of four rations containing 0, 4.4, 8.8 or 17.6 mg/kg of ergot alkaloids (84% dihydroergosine, 10% dihydroelymoclavine and 6% festuclavine), equivalent to ~0, 10, 20 or 40 g/kg ergot (sclerotia/sphacelia) in the rations. These rations were withdrawn at noon on the second day because of severe hyperthermia and almost complete feed refusal in ergot-fed steers. After recovery on ergot-free rations for 5 days, treatment groups were incrementally introduced, over a further 3–12 days, to rations containing 0, 1.1, 2.2 or 4.4 mg/kg of alkaloids (~0, 2.5, 5 or 10 g/kg ergot, respectively). Relative exposure to ergot was maintained, so that the zero- (control), low-, medium- and high-ergot groups remained so. Steers were individually fed ad libitum, and water was freely available. Steers in all ergot-fed groups had significantly elevated rectal temperatures at 0800–1000 hours, even when the temperature–humidity index was only moderate (~70), and displayed other signs of hyperthermia (increased respiration rate, mouth breathing, excessive salivation and urination), as the temperature–humidity index increased to 73–79 during the day. Plasma prolactin was significantly reduced in ergot-fed groups. Voluntary feed intakes (liveweight basis) of the ergot-fed groups were significantly reduced, averaging 94, 86 and 86%, respectively, of the feed intakes of the control group. Hair coats were rough. While the control steers grew from a mean initial liveweight of 275 kg to a suitable slaughter weight of 455 kg in 17 weeks (growth rate 1.45 kg/day), ergot-fed groups gained only 0.77–1.10 kg/day and took at least 5 weeks longer to reach the slaughter weight, despite removal of ergot at the same time as control steers were sent to slaughter. Sorghum ergot, even at low concentrations (1.1 mg alkaloids/kg feed) is severely detrimental to the performance of steers in the feedlot.