Urea utilization by growing lambs. 5. N-balance with half synthetic rations

In experiment with 14-week-old lambs a combination of semisynthetic rations containing 1.2% or 0.7% resp. native crude protein an intraruminal infusion of urea clearly influenced the biologic processes in the rumen. The molar quotas of butyric and valeric acid in comparison with acetic were high. The lambs could cope with infused amounts of 0.67 g urea/kg body weight if they received the daily amount of 1.35 g/kg body weight in two parts. When more than 1.9 g/kg body weight were applied, feed intake decreased even though the daily amount was distributed over 4 doses. In 10 out of 16 lambs N retention was, in dependence on the urea amounts infused, higher than the N amount retained from native crude protein. The result indicates that urea is utilized by 14-week-old lambs. Growing energy and N intake had a positive influence on the N balance.     

Urea utilization in growing lambs. 4. N balances with unprocessed rations

N balance experiments were carried out with lambs of the ages of 8, 12 and 15 weeks fed with wheat rations with and without 2% urea supplement (N 1 and N 2) as well as with 3% urea and 20% straw (N 3) or with a soya bean meal supplement (N 4). There were no significant differences in the digestibility of the crude nutrients and in per cent of N retention between the individual ages. The straw supplement decreased the digestibility of organic matter, crude protein, crude fibre and NfE. The supplements of soya bean meal or urea increased the crude protein content in comparison to the wheat ration without supplements by 6% in the dry matter and resulted in N intakes 55 ... 60% higher and in 23 ... 38% higher N retention, which was, however, lower in relation to N intake. There were no significant differences with regard to N retention between N 2, N 3 and N 4. Consequently urea supplement to the feed mixture with 14% native crude protein resulted in increased N retention, which was not lower than with a soya bean meal supplement.     

Urea utilization in growing lambs. 6. N balance with 15N urea

Lambs of an age of 2 or 4 months and of an average live weight of 14.7 and 27.4 kg resp. received rations consisting of 44% cereals, 46% dried sugar beet pulp, 6% wheat starch, 2% urea and 2% mineral-vitamin mixture. The crude protein content was 17.1 and 15.9% resp. in the dry matter, that of native crude protein 10.6 and 9.4% resp. During a 6-day N balance period 8 and 16 g 15N urea resp. with a 15N excess (15N') of 9.26 and 9.40 atom-% were fed orally instead of commercial feeding urea. There were no significant differences between the two age groups with regard to the digestibility of the organic matter and the crude nutrients. The average N balance of 372 +/- 85 mg/kg LW 0.75/day were in the intermediate range of N retention capacity and accounted for 26 +/- 5% of the consumed N. N retention in per cent. was slightly lower in younger lambs. Projections of urea utilization in a quasi stationary state resulted in an efficiency of the utilization of 33 +/- 4%. The dismembering of the lambs at the end of the main period showed between 0.02 and 0.22 atom-% 15N' in the total N, TCA precipitable N and amino acid N of the meat. At between 0.24 and 0.38 atom-% 15N' they were highest in the heart and jaw muscles. The quota of 15N' amounts found in the total N of the meat were 10.6 +/- 3% of the 15N-intake and 20.1 +/- 5.1% of the 15N' amount remaining in the body. The bones contained 7.7 +/- 1.7% and the fleece 7.9 +/- 3.1% of the 15N'-intake. Generally seen, the total N and urea utilization was slightly lower in younger lambs than in older ones.     

Urea utilization in growing lambs. 7. NPN- and pure protein-N-utilization at various ages

The utilization quota of NPN and pure feed protein for body protein synthesis was calculated on the basis of N balance experiments with 15N labelled urea with the help of model concepts of a 3-pool model and its mathematical usage. In lambs weighing 13 kg, the efficiency of amino acid and nucleic acid synthesis in the non-amino acid N pool was 64%. This results in a total utilization quota for NPN and pure protein in the ration of 40% and 60%, resp. Lambs weighing 27 kg showed an efficiency in amino acid and nucleic acid synthesis in the non-AA N pool of 77% and in the AA N pool of 60%. The total utilization quota of NPN was 47% and that of pure protein 56%. The pure protein in the ration was thus about twice as well utilized for total protein synthesis and for protein synthesis for crude protein retention as the NPN compounds in the ration.     

Urea utilization in growing lambs. 3. Effect of urea and straw on carcass composition

Subsequent to a growth experiment with intensively fattened lambs the value of the carcasses of 4 animals each from 7 groups was determined. The control groups with mixed fattening feed for lambs and the groups with wheat and barley mixtures containing urea showed higher carcass yields, net gains, fat percentage and padding, dry matter and fat content of the carcass and lower quotas of important cuts as well as a lower crude protein content in the carcass than groups with grain without urea and groups with straw. This is due to the higher weight gains of the first-mentioned groups. There were no significant differences in the carcass characteristics between the animals of the control group and the grain-urea groups. The carcass quality of the male lambs was better than that of the female ones.     

Nutrient and energy retention in growing lambs. 1. Results of growth experiments

The results of a growth experiment are explained which was carried out as basis for the control slaughtering method and for N-balance experiments with hybrid fattening lambs of both sexes and of three different genetic constructions in comparison with male merino mutton lambs. The animals were kept individually on perforated floor and received pelleted fattening feed for lambs ad libitum. In the live weight range between 15 and 30 kg the male hybrid lambs reached significantly higher live weight gains than the merino mutton sheep, the former tending towards higher feed intake and lower energy expenditure. The male hybrid lambs showed a significantly higher live weight gain and a significantly lower energy expenditure than the female animals of equal live weight whereas there were no differences between the sexes in feed intake.     

Effects of ruminal escape proteins and canola meal on nitrogen utilization by growing lambs

The effects of ruminal escape proteins and canola meal (CM) on N utilization by growing lambs were evaluated in two experiments. In both experiments, seven supplemental dietary protein treatments were fed. For each of these protein treatments a 3 x 3 Latin square metabolism trial was conducted, using two sets of three lambs and three periods. Within square treatments were 1.4, 1.7 and 2.0 times maintenance intake levels. In Exp. 1, protein treatments were control (7.0% CP, DM basis), urea fed at 9.5 or 12% dietary CP, CM fed at 9.5 or 12% dietary CP and a 50:50 (N basis) mixture of blood meal/corn gluten meal (BC) fed at 9.5 or 12% dietary CP. In Exp. 2, protein treatments were urea, 64% urea and 36% BC (all mixtures on a N basis), 36% urea and 64% BC, BC, 50% CM and 50% BC (CM/BC), CM and soybean meal (SBM), all at 10.5% CP. In Exp. 1, apparent N digestibility (AND) was lower for CM diets than for urea (P = .13) and BC (P less than .05) diets (49.0 vs 50.6 and 51.3%, respectively). Absorbed N was utilized with similar efficiencies for all supplemental protein sources. Dietary CP and digestible protein (DP) were closely related (DP = .879[CP%] -3.66; r2 = .91), indicating that for urea, CM and BC total tract N digestibility was not influenced by theoretical ruminal degradability. In Exp. 2, N balance and N utilization efficiency indicated that the optimal extent of ruminal protein degradation was about 50%. Nitrogen balance was similar for the CM, CM/BC and SBM treatments.(ABSTRACT TRUNCATED AT 250 WORDS)     

The nutrient and energy disposition of growing lambs. 2. Results of slaughter and animal carcass analysis

A total of 90 lambs (fattening hybrids of either sex of three different genetic constructions and male merino meat sheep) were butchered at the beginning (9...16 kg live weight) or at the end (29...33 kg live weight) of a growth experiment. Total body and the meat of carcass, cutlet and loin were analysed. Significant differences between the genotypes could only proved in the crude ash content. The female animals showed a significantly higher content of fat, dry matter and energy as well as a significantly lower content of crude ash--at the end of the experiment also of protein--in the total body than the male animals. The content of nutrients and energy in the total body could be much more precisely derived regressively from the corresponding content values in the meat of the carcass than from the values of cutlet and loin.     

Lupin as a protein supplement for growing lambs

Whole lupins (Lupinus albus) were roasted with exit temperatures ranging from approximately 130 (moderate heat) to 175 degrees C (high heat). In situ N disappearance after 12 h of incubation in the rumen was 83% for raw lupins, 45% for lupins roasted at moderate temperatures, and 39% for lupins roasted at high temperatures. Lambs fed lupins roasted at moderate temperatures retained more N (P less than .01) than those fed soybean meal (SBM). However, growth rate and feed efficiency were similar among lambs fed diets containing SBM, raw lupins, or roasted lupins. Dehulled lupins commercially roasted at low, moderate, and high temperatures resulted in ruminal in situ N disappearances of 59, 47, and 43% for the respective temperatures. Dehulled lupins (Lupinus albus) were also roasted in a laboratory oven for 2, 4, and 6 h at 120, 140, and 160 degrees C. Simulation of roasting for 2 h had no effect (P greater than .10) on ruminal in situ N disappearance at any of the temperatures. In situ N disappearance was reduced (P less than .05) after roasting for 4 h at 160 degrees C, but acid detergent insoluble N was only moderately increased. Nitrogen retention in lambs fed raw, dehulled lupins was equal (P greater than .10) to that of lambs fed SBM. Whole lupins or dehulled lupins can replace SBM as the sole protein supplement for growing lambs. Although roasting lupins decreased ruminal in situ N disappearance, it had no effect on growth of lambs.     

Source and level of supplemental protein for growing lambs

Two 3 x 2 factorial growth trials and a companion metabolism trial with 13, 15, or 17% dietary CP (DM basis), with or without 3% of the DM replaced with slowly degraded menhaden fish meal, were conducted to determine if level of dietary protein influences whether slowly degraded protein improves lamb growth and protein use. The growth trials included 32 and 34 pens of two weanling lambs initially weighing 23 to 26 kg and fed for 42 d. The metabolism trial included 12 additional lambs fed in metabolism cages with a 2-wk adjustment period, a 1-wk preliminary period, and a 7-d collection period. Plasma urea N (PUN) was measured in all lambs at the conclusion of the second growth trial and at the end of the metabolism trial. There was a protein level x protein source interaction (P = 0.05) for PUN of the 12 lambs in the metabolism trial but not for the 68 lambs in the second growth trial. Replacement of part of the soybean meal protein with protein from fish meal did not affect ADG or G:F at any protein level, but it lowered (P = 0.08) PUN in the second growth trial. Plasma urea N values were higher (P = 0.002) in lambs fed diets with 15 or 17% CP; however, ADG (P = 0.037 in Exp. 1 and P = 0.055 in Exp. 2), and G:F (P = 0.094 in Exp. 1 and P = 0.003 in Exp. 2) were lower for lambs fed the diets with 13% CP. There was little difference in ADG or G:F between lambs fed the diets with 15 or 17% CP, suggesting that a CP level of 15% with supplemental protein from soybean meal would be optimal for 25- to 40-kg growing Finnsheep x Dorset lambs.     

Nitrogen utilization in growing lambs: effects of grain (starch) and protein sources with various rates of ruminal degradation

The potential interaction between grain (starch) and protein sources with varying ruminal degradation rates on N utilization in growing lambs was evaluated. Three grain sources with varying ruminal degradation rates, (barley greater than steam-flaked sorghum [SFSG] greater than dry-rolled sorghum [DRSG]) and three protein sources (urea greater than a 50:25:25 mixture of urea: blood meal:corn gluten meal [N basis, U/BC] greater than 50:50 mixture of meal:corn gluten meal [N basis, BC]), were evaluated in a 3 x 3 factorial arrangement. Supplemental protein sources provided 33% of dietary N (CP = 11.0%). For each grain-protein combination, a 3 x 3 Latin square metabolism trial was conducted using two sets of three lambs and three periods. Within-square treatments were 1.4, 1.7 and 2.0 times maintenance intake levels. No interactions were observed (P greater than .2) between dietary treatments and intake level. Grain sources did not differ (P greater than .2) in N balance or the proportion of N retained. Lambs fed urea diets retained less N (3.6 vs 4.2 and 4.1 g/d for urea vs U/BC and BC, respectively; linear, P = .07; quadratic, P = .12) and utilized N less efficiently (43.1 vs 51.9 and 52.5%, respectively; linear, P less than .001; quadratic, P = .10) than lambs fed BC diets. The grain x protein interaction was significant for most variables. Nitrogen utilization was most efficient (24 to 27% of N intake retained) when rapidly degraded sources (barley and urea) and slowly degraded sources (sorghum and BC) were fed together or when U/BC was the supplemental protein source (interaction P less than .08). An advantage was found for selection of starch and protein sources with similar ruminal degradation rates.     

Low-phytic acid corn improves nutrient utilization for growing pigs.

Thirty-five crossbred barrows averaging 14.5 kg initial BW were used in a 5-wk experiment to compare the P availability and nutritional value of a low-phytate hybrid corn (LPC, 0.26% total P, 0.08% phytic acid P) homozygous for the lpa 1-1 allele with a nearly isogenic normal hybrid corn (NC, 0.25% total P, 0.20% phytic acid P). The pigs were fed individually twice daily in metabolism pens. Three semipurified diets were created in which corn was the only source of phytate. Diet 1 contained 72% NC, 0.15% estimated available P (aP) and 0.55% Ca. Diet 2 contained 72% LPC, 0.24% aP, and 0.55% Ca. The only differences between Diets 1 and 2 were the source of corn and the levels of aP. No inorganic P (iP) was added to these diets in order to measure the animal response to the different levels of aP in the corn hybrids. Diet 3 was NC Diet 1 supplemented with iP to equal the level of aP in LPC Diet 2. Diets 4 and 5 were practical corn-soybean meal diets formulated with each corn to meet all minimum nutrient requirements and contained 0.30% aP and 0.65% Ca. For the semipurified diets, pigs fed LPC Diet 2 had higher (P < 0.01) growth performance, bone breaking strength, P absorption and retention, Ca absorption and retention, and N retention than pigs fed NC Diet 1. However, when the NC diet was supplemented with iP to equal the aP in the LPC diet, most criteria were similar (P > or = 0.2), indicating an equal nutritional value for both corn hybrids after adjusting for phytate level. The only treatment difference, other than P excretion, between the practical corn diets supplemented with soybean meal was a higher (P < 0.05) bone breaking strength for pigs fed LPC Diet 5 compared with NC Diet 4. The use of LPC in pig diets reduced P excretion in swine waste by 50 and 18.4% in the semipurified and practical diets, respectively, compared with NC. Using our in vitro procedure designed to simulate the digestive system of the pig, the availability of P for pigs was estimated at 56% for LPC and 11% for NC.     

Anthelmintic effects of Salix babylonica L. and Leucaena leucocephala Lam. extracts in growing lambs

Twenty Katahdin?×?Pelibuey crossbreed male lambs, 3 to 4 months of age and 24?±?0.3 kg of body weight, were used to study the anthelmintic effects of administering extracts of Salix babylonica L. (SB) and Leucaena leucocephala Lam. (LL). Lambs had not been treated with anthelmintics previously and were randomly allocated into four groups of five lambs each in a completely randomized design. Treatments were as follows: control (lambs fed on total mixed ration without extracts), SB (as control plus S. babylonica L. extract at 30 ml/day), LL (as control plus L. leucocephala Lam. extract at 30 ml/day), and SBLL (as control plus 30 ml/day of S. babylonica L. and L. leucocephala Lam. extracts in a 1:1 (v/v) mixture) for 63 days. Extracts were orally administered before the 8:00 a.m. feeding to each lamb. Rectal fecal samples were collected from each lamb at day 22 (P1), day 43 (P2), and day 63 (P3) of the experiment. Adult worm and egg counts were determined in each fecal sample immediately after collection. Plant secondary metabolites of total phenolics, saponins, and the aqueous fraction were 50 % lower in the SB versus LL extracts. Overall, the oral administration of extracts has improved the egg and worm count reductions in lamb feces by 54, 47, and 40 % for LL, SB, and SBLL, respectively, versus the control lambs. Reductions of worm egg counts in lamb feces were higher (P?<?0.05) in P2 and P3 versus P1. Extracts of SB and LL or possibly isolated bioactive compounds could be a promising alternative to conventional anthelmintics to treat gastrointestinal parasites of small ruminants. Such treatments could be used in control strategies against gastrointestinal nematodes in organic and conventional production systems.