Measures of methane production and their phenotypic relationships with dry matter intake, growth, and body composition traits in beef cattle.

Ruminants contribute up to 80% of greenhouse gas (GHG) emissions from livestock, and enteric methane production by ruminants is the main source of these GHG emissions. Hence, reducing enteric methane production is essential in any GHG emissions reduction strategy in livestock. Data from 2 performance-recording research herds of Angus cattle were used to evaluate a number of methane measures that target methane production (MPR) independent of feed intake and to examine their phenotypic relationships with growth and body composition. The data comprised 777 young bulls and heifers that were fed a roughage diet (ME of 9 MJ/kg DM) at 1.2 times their maintenance energy requirements and measured for MP in open circuit respiration chambers for 48 h. Methane traits evaluated included DMI during the methane measurement period, MPR, and methane yield (MY; MPR/DMI), with means (± SD) of 6.2 ± 1.4 kg/d, 187 ± 38 L/d, and 30.4 ± 3.5 L/kg, respectively. Four forms of residual MPR (RMP), which is a measure of actual minus predicted MPR, were evaluated. For the first 3 forms, predicted MPR was calculated using published equations. For the fourth (RMPR), predicted MPR was obtained by regression of MPR on DMI. Growth traits evaluated were BW at birth, weaning (200 d of age), yearling age (400 d of age), and 600 d of age, with means (± SD) of 34 ± 4.6, 238 ± 37, 357 ± 45, and 471 ± 53 kg, respectively. Body composition traits included ultrasound measures (600 d of age) of rib fat, rump fat, and eye muscle area, with means (± SD) of 3.8 ± 2.6 mm, 5.4 ± 3.8 mm, and 61 ± 7.7 cm(2), respectively. Methane production was positively correlated (r ± SE) with DMI (0.65 ± 0.02), MY (0.72 ± 0.02), the RMP traits (r from 0.65 to 0.79), the growth traits (r from 0.19 to 0.57), and the body composition traits (r from 0.13 to 0.29). Methane yield was, however, not correlated (r ± SE) with DMI (-0.02 ± 0.04) as well as the growth (r from -0.03 to 0.11) and body composition (r from 0.01 to 0.06) traits. All the RMP traits were strongly correlated to MY (r from 0.82 to 0.95). These results indicate that reducing MPR per se can have a negative impact on growth and body composition of cattle. Reducing MY, however, will likely have the effect of reducing MPR without impacting productivity. Where a ratio trait is undesirable, as in animal breeding, any of the RMP traits can be used instead of MY. However, where independence from DMI is desired, RMPR should be a trait worth considering.

Effects of the absence of protozoa from birth or from weaning on the growth and methane production of lambs.

Merino ewes (n 108) joined to a single sire were allocated into three flocks, with ewes in one flock being chemically defaunated in the second month of gestation. Single lambs born to defaunated ewes (BF lambs) were heavier at birth and at weaning than lambs born to faunated ewes (F lambs). After weaning, all BF and F lambs were individually housed then half of the F lambs were chemically defaunated (DF lambs). In trial 1, BF, DF and F lambs were offered a concentrate-based diet containing either 14 or 19 % protein for a 10-week period. Wool growth rate of BF lambs was 10 % higher than that of DF or F lambs and was increased 9 % by the high-protein diet. While there was no main effect of protozoa treatment on enteric methane production, there was an interaction between protozoa treatment and diet for methane production. BF and DF lambs produced more methane than F lambs when fed the low-protein diet but when fed the high-protein diet, emissions were less than (BF lambs) or not different from (DF lambs) emissions from F lambs. In trial 2, lambs were offered 800 g roughage per d and, again, methane production was not affected by the presence of protozoa in the rumen. The data indicate that while lambs without rumen protozoa have greater protein availability than do faunated ruminants, there is no main effect of rumen protozoa on enteric methane production by lambs fed either a concentrate or roughage diet.

Effects of various adjuvants on efficacy of a vaccine against Streptococcus bovis and Lactobacillus spp in cattle.

OBJECTIVE: To determine efficacy of vaccines incorporating QuilA, alum, dextran combined with mineral oil, or Freund adjuvant for immunization of feedlot cattle against Streptococcus bovis and Lactobacillus spp. ANIMALS: 24 steers housed under feedlot conditions. PROCEDURE: Steers were randomly assigned to 4 experimental groups and a control group. Animals in experimental groups were inoculated on days 0 and 26 with vaccines containing Freund adjuvant (FCA), QuilA, dextran combined with mineral oil (Dex), or alum as adjuvant. Serum anti-S bovis and anti-Lactobacillus IgG concentrations were measured, along with fecal pH, ruminal fluid pH, and number of S bovis and Lactobacillus spp in ruminal fluid. RESULTS: Throughout the study, serum anti-S bovis and anti-Lactobacillus IgG concentrations for animals in the Dex, QuilA, and alum groups were similar to or significantly higher than concentrations for animals in the FCA group. Serum anti-S bovis and anti-Lactobacillus IgG concentrations were significantly increased on days 26 through 75 in all 4 experimental groups, and there was a linear relationship between anti-S bovis and anti-Lactobacillus IgG concentrations. For animals in the QuilA and Dex groups, mean pH of feces throughout the period of experiment were significantly higher and numbers of S bovis and Lactobacillus spp in ruminal fluid on day 47 were significantly lower than values for control cattle. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that immunization of feedlot steers against S bovis and Lactobacillus spp with vaccines incorporating Freund adjuvant, QuilA, dextran, or alum as an adjuvant effectively induced high, long-lasting serum anti-S bovis and anti-Lactobacillus IgG concentrations. Of the adjuvants tested, dextran may be the most effective.

Immunological cross-reactivity between the vaccine and other isolates of Streptococcus bovis and Lactobacillus.

Recent studies have showed that immunisation with Streptococcus bovis (Sb-5) and Lactobacillus (LB-27) may confer protection against lactic acidosis in sheep and cattle. The present study was designed to determine the degree of immunological cross-reactivity between Sb-5 and eight other strains of Streptococcus bovis; and between LB-27 and four other isolates of Lactobacillus. The cross-reactivity index (CRI, a low CRI indicates a high degree of immunological cross-reactivity) ranged from 7.3 to 56.1% between the strains of S. bovis (the encapsulated strains with CRIs ranging from 7.3 to 12.4%). For isolates of Lactobacillus the CRIs ranged from 11.5 to 72.2%. The results indicate that all the isolates tested have a certain degree of immunological homology with Sb-5 and LB-27, and suggest that the vaccine may cross-react with a large number of strains of S. bovis and Lactobacillus which may cause lactic acidosis. As most of the S. bovis strains in the rumen are encapsulated, the high degree of homology between Sb-5 and encapsulated S. bovis strains further suggests that the vaccine containing Sb-5 may be effective against a wide range of strains of S. bovis in sheep and cattle.

Immunisation against lactic acidosis in cattle.

The present study was designed to investigate the efficacy of control of lactic acidosis by immunisation against lactic acid-producing bacteria, Streptococcus bovis and Lactobacillus. Ten steers were allocated to two treatment groups. One group was immunised with a vaccine containing S. bovis (strain Sb-5) and Lactobacillus (LB-27) cells, and the other was a non-immunised control group. The vaccine, using Freund's complete adjuvant for primary immunisation and Freund's incomplete adjuvant for boosters, was administered intramuscularly. After primary immunisation, boosters were given at 2 to 4 week intervals. Both anti- S. bovis and anti- Lactobacillus IgG levels in saliva increased significantly (P < 0.01) after the 1st booster which were lower (P < 0.05) than the IgG levels after the 2nd and 3rd boosters, but were not significantly different (P > 0.05) from the IgG levels prior to a grain challenge (after the 4th booster). There were positive correlations between the anti- S.bovis and anti- Lactobacillus IgG in serum and saliva. Compared with the control group, steers in the immunised group had higher (P < 0.05) feed intakes, lower (P < 0.05) rumen concentrations of lactate and lower numbers of S. bovis and Lactobacillus. Three of the control animals were withdrawn from the grain challenge due to their rumen pH persisting below 5.2, while only one animal in the immunised group was withdrawn. These results suggest that the risk of lactic acidosis can be reduced by immunisation against S. bovis and Lactobacillus.

Further studies on the effects of the presence or absence of protozoa in the rumen on live-weight gain and wool growth of sheep.

Lambs were given a diet of oaten chaff-sucrose-fishmeal (48:48:4, w/w) and either 60 (diet A) or 120 (diet B) g urea/kg sucrose in the diet. All animals were defaunated and half were refaunated. Each group of lambs (faunated and defaunated) was then divided into two groups and given diet A or diet B. Feed intake, wool growth and live-weight change were monitored over a 182 d period. The level of urea supplementation had no effect on wool growth or live-weight gain. Defaunated lambs gained live weight at a higher rate (9%, P less than 0.06) and grew 37% more wool (P less than 0.01) than the lambs with large populations of protozoa in their rumens.

The effects of defaunation of the rumen on the growth of lambs on low-protein-high-energy diets.

1. The effects of defaunation of the rumen of lambs given low-protein-high-energy diets were studied using animals fed ad lib. a basal diet of sugar and oaten chaff which was supplemented with fish meal at various levels. These diets supported relatively large populations of protozoa in the rumen. 2. A nonyl phenol ethoxylate (15 g. Teric GN9:ICI Australian Ltd) given intraruminally, was shown to be an effective means of defaunating the rumen and the lambs were maintained protozoa-free by isolation. 3. In lambs given low levels of fish meal in the diet, the absence of rumen protozoa increased growth rate and improved the food conversion efficiency (g dry matter intake/g growth). These effects were not apparent at high levels of protein supplementation. 4. These results suggested that the absence of rumen protozoa resulted in an increased availability of nutrients supplying both energy and amino acids since the efficiency of food utilization and the rate of wool growth (which is sensitive to amino acid supply) were increased in lambs on the low level of protein supplementation without apparently increasing food intake.

The effects of defaunation of the rumen on the growth of cattle on low-protein high-energy diets.

1. The effects of defaunation of the rumen of cattle on low-protein diets was studied using animals given free access to a basal diet of liquid molasses and 1500 g oaten straw/head per d. These diets induced moderate numbers of protozoa in the rumen. 2. Nonyl phenol ethoxylate (trade name teric GN9) was used for defaunation; 100 g teric GN9 was found to be sufficient to eliminate protozoa from the rumen. 3. In cattle given the basal diet without bypass protein supplementation, defaunation had no effect on growth rates. Addition of 240 g of a feed pellet containing bypass protein increased growth rate significantly. Growth rates were significantly increased by 43% in cattle on the higher protein intake and where protozoa were removed. Intake of molasses was apparently stimulated by a protein supplementation but not by defaunation and this finding is discussed. 4. The results demonstrate that in cattle given a molasses-based diet, low in bypass protein, growth rates can be stimulated by defaunation without an effect on feed intake, the main effect apparently arising through an increased efficiency of utilization of feed.