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Publication Date
1981
Description
Alfalfa (Medicago sativa) is an efficient and important means of producing supplemental protein for ruminants. This research was undertaken to characterize the value of alfalfa protein for ruminants and to show how the protein is affected by different harvesting or processing regimens. The effects of maturity (prebloom, one-tenth, one half, and full bloom) and processing method (freeze dried [FD], sun cured [SC], and oven heated [HJ), on percentage of nitrogen (N), acid detergent insoluble N (ADIN), in-vitro rumen ammonia release (NH3), and in-situ rumen protein degradation, using dacron bags (BAG), were studied on irrigated alfalfa harvested over 2 years. Plants were separated into leaves and stems after harvest or processing and analyses were conducted on each. Nitrogen decreased (P < 0.05) and ADIN increased (P < 0.05) as plants became more mature. Leaves contained approximately 2.5 times as much N as stems. Processing (SC and H) reduced (P < 0.05) protein degradability measured by NH3 and BAG. Heating produced greater decreases in protein degradability than SC. Leaves responded more to processing methods than stems. Two experiments were conducted to assess heat dehydration effects for steer calves (200 kg). Low-protein diets (60% corn cobs and 20% corn) were supplemented to 11.5% crude protein with urea or with combinations of soybean meal (SMB) and urea or dehydrated alfalfa (DEHY) and urea. Data for the two experiments were pooled. Daily gain (kg) and feed/gain were: 0.41, 15.23; 0.47, 12.60; and 0.54, 11.18 for urea, SBM, and DEHY, respectively. Protein efficiency values were calculated as the added gain of the test-protein animals above gains of the urea-control animals divided by the amount of test protein/day. Protein efficiency was 0.203 for SBM and 0.547 for DEHY. These values demonstrate that heat dehydration increases the value of alfalfa protein for ruminants by decreasing ruminal-protein degradability. The last set of experiments evaluated the effects of mechanical removal of solubles from alfalfa and subsequent heat dehydration on the value of alfalfa protein for ruminants. N-balance experiments with lambs showed that N digestibility of the press-cake alfalfa (PC) was reduced (P < 0.05) compared with that of regular DEHY, SBM, or urea but that N balance was not affected negatively compared with regular DEHY or SBM. The protein (P) present in the liquid from the mechanical squeezing of alfalfa can be harvested. The resultant liquid, called brown juice (BJ), is partially concentrated and can be dried on the PC. The last experiment tested the efficiency of protein utilization of PC, PC + BJ, PC + BJ + P, and regular DEHY in steer calves (10 animals/treatment). SBM and urea were included as positive and negative controls. Daily gain and feed/gain (in kg) were: urea, 0.63, 8.22; SMB, 0.66, 7.71; DEHY, 0.71, 7.81; PC, 0.77, 7.23; PC + BJ, 0.78, 7.12; and PC + BJ + P, 0.74, 7.29. Protein efficiency values were: SBM, 0.43; DEHY, 1.27; PC, 1.48; PC + BJ, 1.64; and PC + BJ + P, 1.37. These data demonstrate that removal of solubles from alfalfa does not decrease the value of the protein remaining for ruminants and confirm and emphasize the positive effect of heat dehydration of alfalfa protein for ruminants.
Citation
Britton, R; Rock, D; Klopfenstein, T; Ward, J; and Merrill, J, "Harvesting and Processing Effects on Alfalfa Protein Utilization by Ruminants" (1981). IGC Proceedings (1977-2023). 15.
(URL: https://uknowledge.uky.edu/igc/1981/section10/15)
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Harvesting and Processing Effects on Alfalfa Protein Utilization by Ruminants
Alfalfa (Medicago sativa) is an efficient and important means of producing supplemental protein for ruminants. This research was undertaken to characterize the value of alfalfa protein for ruminants and to show how the protein is affected by different harvesting or processing regimens. The effects of maturity (prebloom, one-tenth, one half, and full bloom) and processing method (freeze dried [FD], sun cured [SC], and oven heated [HJ), on percentage of nitrogen (N), acid detergent insoluble N (ADIN), in-vitro rumen ammonia release (NH3), and in-situ rumen protein degradation, using dacron bags (BAG), were studied on irrigated alfalfa harvested over 2 years. Plants were separated into leaves and stems after harvest or processing and analyses were conducted on each. Nitrogen decreased (P < 0.05) and ADIN increased (P < 0.05) as plants became more mature. Leaves contained approximately 2.5 times as much N as stems. Processing (SC and H) reduced (P < 0.05) protein degradability measured by NH3 and BAG. Heating produced greater decreases in protein degradability than SC. Leaves responded more to processing methods than stems. Two experiments were conducted to assess heat dehydration effects for steer calves (200 kg). Low-protein diets (60% corn cobs and 20% corn) were supplemented to 11.5% crude protein with urea or with combinations of soybean meal (SMB) and urea or dehydrated alfalfa (DEHY) and urea. Data for the two experiments were pooled. Daily gain (kg) and feed/gain were: 0.41, 15.23; 0.47, 12.60; and 0.54, 11.18 for urea, SBM, and DEHY, respectively. Protein efficiency values were calculated as the added gain of the test-protein animals above gains of the urea-control animals divided by the amount of test protein/day. Protein efficiency was 0.203 for SBM and 0.547 for DEHY. These values demonstrate that heat dehydration increases the value of alfalfa protein for ruminants by decreasing ruminal-protein degradability. The last set of experiments evaluated the effects of mechanical removal of solubles from alfalfa and subsequent heat dehydration on the value of alfalfa protein for ruminants. N-balance experiments with lambs showed that N digestibility of the press-cake alfalfa (PC) was reduced (P < 0.05) compared with that of regular DEHY, SBM, or urea but that N balance was not affected negatively compared with regular DEHY or SBM. The protein (P) present in the liquid from the mechanical squeezing of alfalfa can be harvested. The resultant liquid, called brown juice (BJ), is partially concentrated and can be dried on the PC. The last experiment tested the efficiency of protein utilization of PC, PC + BJ, PC + BJ + P, and regular DEHY in steer calves (10 animals/treatment). SBM and urea were included as positive and negative controls. Daily gain and feed/gain (in kg) were: urea, 0.63, 8.22; SMB, 0.66, 7.71; DEHY, 0.71, 7.81; PC, 0.77, 7.23; PC + BJ, 0.78, 7.12; and PC + BJ + P, 0.74, 7.29. Protein efficiency values were: SBM, 0.43; DEHY, 1.27; PC, 1.48; PC + BJ, 1.64; and PC + BJ + P, 1.37. These data demonstrate that removal of solubles from alfalfa does not decrease the value of the protein remaining for ruminants and confirm and emphasize the positive effect of heat dehydration of alfalfa protein for ruminants.
