2006 Buck Feeding Trial 23 commercial bucks from one commercial herd were evaluated on the GrowSafe system for 41 days. ADG ranged from 0.46 to 1.12 lbs/day with the group averaging 0.67 lbs/day. Ultrasound carcass data from the rams on the trial, adjusted to 80.43 pounds, ranged from 0.04-0.12 inches for backfat and 1.27- 1.93 square inches for LEA.
What makes this performance test unique? Feed Efficiency Data / Residual Feed Intake (RFI)
Understanding RFI and its Implications Residual Feed Intake
Relationship of ADG w/ Maturity Physiological maturity ADG Must grow to larger size to equal stage of finish. i.e. greater mature size
Genetic Scaling Theory Increased growth rate leads to increased mature weight and a consequent increase in maintenance requirements. In most ruminant production systems 65-75% of the total lifetime dietary energy is used for maintenance –Only 5-22% is used for protein deposition. –Maintenance energy requirements have been shown to be moderate to highly heritable (h 2 =0.22-0.71)
If so important then why have we waited until now? Difficulty in obtaining necessary measurement: –Gain –Individual feed intakes ??? validity of data under non-production environment. Understand what the data means and what concerns there are with the data generated.
Efficiency of Conversion of Feed RFI (actual – expected) –Considerable individual animal variation in feed intake above and below what is expected based on size and growth
RFI –The Practice Increase in weight over time is measured with multiple observations and modeled by regression. –Normalization of the growth curve to avoid periods of morbidity or restriction. –Initial weight, ADG, midpoint weight and final weight are calculated from the regression. –Intake is regressed on mid BW + ADG Mid BW is very important! This gives us an expected value for animals of similar weights and rates of gain.
RFI – The Theory RFI is independent of growth and maturity patterns. RFI is a more sensitive and precise measure of feed quality based on energy intake and requirements. Uses accurate contemporaries for comparison –Positive RFI indicates less efficient use of energy compared to contemporaries –Negative RFI indicates greater efficiency RFI has been shown to have a heritability coefficient near.45, similar to growth.
Results Residual Feed Intake (RFI), ranged from 3.24 to (-)2.54 lbs/day. The buck with the RFI value of (-) 2.54 was more efficient and consumed 2.54 pounds less feed than was expected per day. Difference between the most and least efficient bucks was 5.78 lbs of feed per day (a cost of $.65 per day
Result The trial demonstrated the GroSafe feeding system with modifications can be used to test meat goats.