Preruminant male crossbred lambs, aged 2–5 days at the start of the experiment, were used in two experiments with low protein milk replacers (0.10 of total energy as protein) containing isolated soybean protein as the sole source of protein. Experiment 1. Groups of three lambs were given the soybean diet supplemented with DL-methionine (seven levels) in increasing (experiment la) or decreasing amounts (experiment 1b). Dietary periods were each of 3 days. Estimates of minimum intakes of methionine plus cystine, coincident with maximum animal response, based on a 1 day nitrogen balance or on plasma urea nitrogen concentrations, indicated that there was a carry-over effect when methionine was given in decreasing amounts. Experiment 2. An 8 x 8 change-over design was used to minimize carry-over effects. Each lamb was given each diet (seven levels of methionine) for 4 days, in such an order that in the final design each diet was preceded once by every other diet. No carry-over effects were observed. It was concluded that the change-over design could be used to estimate amino acid requirements with fewer animals and with shorter dietary periods than in the conventional balance experiment.
Preruminant male crossbred lambs, aged 2–5 days at the start of the experiment, were used in five experiments to determine the sequence of limiting amino acids in milk replacers containing groundnut protein isolate (GPI) as the sole source of protein. Experiment 1. Eight lambs were each given eight diets in an 8 x 8 change-over design. The diets contained GPI, unsupplemented with amino acids, to provide from 0.10 to 0.45 of the total energy as protein. Experiment 2. Eight lambs were used in two 4 x 4 change-over designs. The protein energy concentration of the diets after supplementation with amino acids was 0.22. In both experimental designs the GPI was supplemented with Met, Lys and Thr as a group in one diet. In experiment 2a each of these amino acids was added singly in successive diets, while in experiment 26 one of the amino acids was omitted in turn from the mixture. Experiment 3. Six lambs were each given six diets based on GPI, supplemented with Met and Lys, at six levels of protein energy (0,100-0.225) in a 6 x 6 change-over design. Experiment 4. Eight lambs were used in an 8 x 8 change-over design. The protein energy concentration of the eight diets was 0.12 after supplementation with a group of amino acids that included Met, Lys, Thr, Val, Leu, Isol, Try and Phe. In successive diets Thr, Val, Leu, Isol, Try and Phe were omitted singly and, in the final diet, these six amino acids were omitted as a group. In experiments 1-4 the dietary periods were of 3 or 4 days. Nitrogen balances were estimated and plasma urea nitrogen concentrations (PUN) measured on the last day of each dietary period. Experiment 5. Six lambs, in two equal groups, were used in a conventional balance experiment, with a 5-day preliminary and a 6 day collection period. One group was given an unsupplemented low protein diet based on GPI, the other group had a similar diet supplemented with Met, Lys and Thr. The protein energy concentration in both diets was 0.10. The sequence of limiting amino acids in GPI (based on a 1 day nitrogen balance) was Met, Lys (equally first limiting at a protein energy concentration of 0.22), Thr, Try (equally third limiting at a protein energy concentration of 0.12). A 1-day nitrogen balance (or urinary urea nitrogen excretion in experiment 4) was a more sensitive indicator of the protein quality of a diet than PUN concentrations. The 1 day collection period gave a similar estimate of nitrogen balance to that determined in the conventional 6 day balance experiment.
Preruminant male crossbred lambs, aged 2-5 days at the start of the experiment, were fed on milk replacers that contained groundnut protein isolate as the sole source of protein, supplemented with graded levels of L-lysine hydrochloride. A series of 6x 6 change-over designs with 4-day dietary periods was used in experiments 1 and 2, and a conventional 14-day nitrogen balance in experiment 3. Estimates were made of the minimum intake of lysine coincident with the maximum animal response (MIMR)-measured as maximum nitrogen balance (NB) or minimum plasma urea nitrogen (PUN) concentration. In experiment 1 three diets with different protein concentrations (0.11, 0.18 and 0.25 of total energy as protein) were compared at a controlled intake of gross energy (0.88 MJ/day per kg0.73). At each protein concentration the response to six graded levels of L-lysine hydrochloride was measured. In experiment 2 a diet of constant protein energy concentration (0.25) was offered at three different intakes of energy (0.63, 0.88 and 1.13 MJ/day per kg0 73). At each level of energy intake the response to six graded levels of L-lysine hydrochloride was measured. In experiment 3 a milk replacer containing 0.25 protein energy was offered at a constant intake of 0.88 MJ gross energy/day per kg0 73 and, as in the previous experiments, the response to SIX graded levels of L-lysine hydrochloride was measured. The MIMR for lysine (expressed as a percentage of dietary protein) decreased curvilinearly with an increase in protein concentration, but was unaffected by an increase in the intake of energy. Estimates based on PUN were similar to those based on NB, but the errors associated with the estimates were greater at the lowest protein concentration in experiment 1 and at the lowest intake of energy in experiment 2. Estimates of MIMR in experiments 1 and 3 were in close agreement.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.