Effects of light intensity during rearing and beak trimming and dietary fiber sources on mortality, egg production, and performance of ISA brown laying hens
The effects of light intensity during rearing and beak trimming and dietary fiber sources on the incidence of cannibalism were investigated with 2,880 ISA Brown hens. During the rearing period, chicks were housed under two levels of light: dim light (i. e., 5 lx) and bright light (i. e., 60 to 80 lx) and two beak conditions: with or without trimming. At 15 wk of age, all birds were transferred to laying cages with five birds per cage. At 17 wk of age, four diets containing different concentrations of dietary fiber were offered: a commercial (wheat) diet, high insoluble fiber (millrun) diet, high soluble fiber (barley) diet, and high soluble fiber diet plus enzyme. Beak trimming had a profound effect (P < 0.001) on cannibalism with mortality occurring predominantly in untrimmed birds. Total mortality for the trimmed birds was 0.14 and 0.77% for the prelay (17 to 20 wk) and early lay periods (21 to 24 wk), whereas mortality was 13.4 and 37.7%, respectively, for the untrimmed birds. The beak-trimmed birds had lower feed intake than the nontrimmed birds (P < 0.05). Diet significantly affected cannibalism (P < 0.01). The highest mortality occurred in birds fed the commercial diet (13 and 29% for the prelay and early lay period, respectively). Diet also affected feed intake (P < 0.05), being lower (P < 0.05) on the commercial diet than on the higher fiber diets. Egg production per bird did not differ significantly between diets. Light intensity during rearing did not influence the incidence of cannibalism.
Use of supplementary nitrate to mitigate methane production and provide rumen degradable N for ruminants
In Australia, enteric methane from ruminants represents 11% of total agricultural GH emissions. Practical ways of reducing methane emissions from ruminants in Australia are required to enable the livestock industries to reduce their carbon footprint. When rumen microorganisms ferment feed organic matter, they generate the reduced cofactor NADH which is in equilibrium with rumen H₂. In ruminants, the H₂ is normally removed by the reduction of CO₂ to form methane. However, NO₃⁻ (present in some fresh pasture forage) has a higher affinity for H₂ than CO₂ and, when it is present, H₂ is first used in the reduction of NO₃⁻ to NO₂⁻ and NO₂⁻ to NH₃ thereby reducing the production of methane from CO₂. After reviewing the literature and considering the potential for NO₂⁻ poisoning, Leng (2008) concluded that supplementation of ruminants with NO₃⁻ (as an alternative to urea) is entirely feasible. This study therefore examined digestion, microbial growth and methane production in sheep given a diet of chaffed oaten hay supplemented with isonitrogenous amounts of KNO₃, urea, or both N sources. Eight Merino wethers (38.6 kg, SE 2.4; aged 3 years with long-established rumen fistulas) were housed in metabolism cages in 2 rooms (15-20°C, continuous lighting) and allocated to 2 treatment groups. Two isonitrogenous diets based on chaffed oat hay were prepared. A diet with 4% added KNO3 was prepared by sprinkling a solution of KNO₃ onto the hay while it was stirred in a rotary feed mixer. Another diet (0% KNO₃) was similarly prepared using a urea solution so that 5.54 g N was added per kg hay for both diets. The sheep were gradually acclimated to the NO₃⁻ containing diet over 18 days. The daily ration (1 kg/d air-dry feed) was delivered to both groups of sheep in equal portions each hour by automatic feeders during a 4-day digestibility trial, and every 2 h while the sheep were in respiration chambers to determine their methane output.
Effect of Nitrate on Variability of Methane Production in Sheep Fed Every 2 Hours
Rumen microbes ferment feed organic matter to obtain energy for microbial growth and generate endproducts including volatile fatty acids, H₂ and CO₂. H₂ and electrons from NADH are used by Archaea to reduce CO₂ to CH₄. Therefore, methane represents a loss of digestible energy as well being a potent greenhouse gas and the search for practical methods to reduce CH₄ release is a current priority. Nitrate salts inhibit methanogenesis (Allison et al 1981) and Leng (2008) has concluded that the inclusion of nitrate salts in feed supplements offers a feasible means of reducing CH₄ emissions from ruminant livestock. The study reported here was undertaken to provide a better understanding of the effect of NO₃⁻ on the rate of and variability in CH₄ production in the rumen of sheep. Twelve sheep were slowly acclimated over 2 weeks to a diet of chaffed oaten hay (1 kg/d as fed) containing no KNO₃ (n=4), or 2% (n=4) or 4% KNO₃ (n=4). CH₄ production was then measured over a 22h period while the sheep were in respiration chambers (Bird et al. 2008) and given 1/12th of their daily ration every 2h. Concentrations of CH₄ in each chamber were recorded automatically at regular (c. 14 min) intervals. These concentrations were subjected to serial correlation and spectral analysis to determine if rhythmic variations CH₄ production could be detected. Figure 1 shows the serial correlation coefficients for the mean CH₄ concentrations in the chambers for 4 sheep receiving the control diet or the same diet with 4% added KNO₃⁻. ... There are strong rhythmical cycles of 2h duration in the original signal for both control and nitrate supplemented sheep. Mean CH₄ concentration was 27.5% lower for sheep offered the diet containing 4% KNO₃⁻ (207± 1.6 vs 150 ± 2.4 ppm). This result is similar to that found by Mathers and Walters (1982) in sheep offered feed every 2h. As well as reducing ruminal CH₄ production, the addition of NO₃⁻ to the diet altered the patterns of chamber CH₄ concentrations relative to those for the control diet. Even with addition of NO₃⁻ to the diet to reduce CH₄ production and frequent feeding, there was considerable deviation from steady state in the rate of fermentation in the rumen. Further analysis of this type of data will help improve our understanding of the rumen fermentation mechanisms leading to variations in CH₄ production.
Rumen digestibility of Mulato II hybrid and rice straw for cattle feeding in Cambodia
In Cambodia, seasonal flooding of land each year by the Mekong river limits the availability of feed for cattle. To alleviate this feed shortage, the concept of forage banks was developed by CIAT (2003-05) and feed banks are being exploited in our current ACIAR project (AH/2003/008). 'Brachiaria' mulato II hybrid (CIAT 36087) is a promising grass for these fodder banks but its nutritive value for cattle when used as a supplement with rice straw has not been widely investigated. The aim of this study was to provide basic information on the in situ rumen digestibility of mulato II hybrid relative to rice straw and to determine the effect of the animal's diet on rumen degradability estimated by the in situ method. In situ evaluations of dried samples of rice straw and sun-dried, first-cut mulato were made using 3 fistulated steers (c. 2.5 years, 248 ± 38kg). In Expt 1, bags were placed in steers ingesting 30% fresh-cut mulato II and 70% rice straw and, in Expt 2, the steers ingested only freshly cut mulato ad libitum. In Expt 1, feed bins were emptied each morning and then filled with rice straw followed by half of the daily ration of fresh mulato; the second half was given in the evening. Both feeds were cut to 2 mm, placed in nylon bags (pore size 40 μm) and incubated (in triplicate) for 3, 12, 24, 36, 48, 72 and 96 h in all three steers. All bags were removed together and washed with 9 additional bags, similarly prepared but never placed in the rumen (to give washing loss). Results for loss of OM (Y) during the incubation period (t) were fitted to a curve, Y=A+B(1-e⁻ct) where A, B, c and lag time are as described by Dhanoa et al. (1996). Rumen NH₃ was also determined (Beecher and Whitten 1970). Effective degradability of both feeds was higher (P<0.05) when steers were ingesting 100% mulato, and lag time (the period before there was net loss of OM) was shorter by 3-4 h (P<0.05), indicating that rumen digestion was markedly inferior when the diet was 70% rice straw and only 30 % mulato (Table 1). Effective degradability of OM, washing loss and rate of degradation of B were higher (P<0.05) and lag time was shorter (P<0.05) for mulato than for rice straw. The degradable OM percentage, excluding washing loss (WL) was similar for mulato and rice straw but with WL included, total potential degradability was higher (P<0.05) for mulato. Thus, the main reason that mulato hybrid exhibited a higher nutritive value than rice straw was its higher washing loss (higher level of soluble components) and its apparently more rapid colonisation by rumen microorganisms.
How Often Do We Need to Measure Methane Production in Ruminants to Establish Robust Phenotype?
Increasing interest in reducing emission of the greenhouse gas methane from ruminants has lead to a need for reliable and accurate determination of the daily methane production (DMP) phenotype in ruminants. Twenty-four hour direct calorimetry is generally considered to give an accurate measurement of DMP. However, single measurements, while accurate on the day, does not account for day-to-day intra-animal variability in determination of DMP phenotype. This paper draws on the results of a large body of data (Blaxter and Clapperton, 1965) to estimate the number of measurements needed to discern real differences in the DMP phenotype with varying levels of confidence. Blaxter and Clapperton's (1965) results from 989 individual 24h CH₄ (sheep and cattle) determinations, indicated a day-to-day CV within animals of 7.2%. Using this value we calculated the number of measurements required to detect a varying degrees of difference at different confidence levels from a t-distribution. Figure 1 presents estimates of the number of measures required to detect an expected difference between individual animals at 3 levels of confidence. Increasing the number of DMP measurements will enable the detection of smaller differences in DMP between animals. ... Using a published CV of 7.2, it is clear that single measures of DMP are inadequate to characterise DMPs with a reasonable degree of confidence. We conclude that greater consideration needs to be given as to the number of measures required to adequately discern true differences in DMP phenotype.
Importance of drinking water temperature for managing heat stress in sheep
Australian sheep are transported to the Middle East where excessive temperatures (>45°C) can cause heat stress and inappetence, compromising the welfare of animals in the post-discharge phase of an industry worth $1.8 billion annually (Hassall and Associates 2006). There is little published research on the importance of drinking water temperature in managing heat stress in sheep. There are also no recommendations. Recommended water temperatures for cattle in hot climates are 16 to 18°C (EA Systems 2004). This study found that as drinking water was increased from 20°C to 40°C water intake increased and that sheep prefer to drink water of 30°C rather than 20°C in hot climates. These are new findings with important implications for the industry.
In vitro ruminal VFA production is unaffected by the presence of sulphur hexafluoride
Since first proposed by Johnson et al. (1994), the sulphur hexafluoride (SF₆) tracer technique has been used to quantify ruminal methane emissions from both cattle and sheep. To make the SF₆ technique more robust, permeation tubes with higher release rates have been developed (Hegarty and Woodgate 2003). Although SF₆ is thought to be an inert and non-toxic marker gas, the higher release rates from the new capsules could invalidate this method of determining methane production if there is any effect on microbial metabolism. The intra-ruminal concentration of SF₆ after inserting capsules releasing 100-200 mg/d was from 1-35μl/l(Goopy et al. 2003). A study was made to determine whether SF₆ had any effect on microbial VFA production in the range of 1-100 μl/l.