With temperatures crossing the 70-degree mark in February, beef producers begin thinking about green grass and spring turnout. The current demand for lightweight and stocker calves would further support the idea spring is near.
Yet another hallmark of spring in my part of the world is the movement of fertilizer buggies and Co-op spreaders running up and down the road fertilizing wheat and cool season pastures. There have certainly been technology improvements in crop space, however, the decisions around pasture fertilization seem to remain at: whether to fertilize or not, and if so, how much nitrogen to apply.
A pair of articles by Jordan Adams and co-workers in Applied Animal Science[1] highlighted the differences between turning out on fertilized pastures compared to directing financial resources to supplementing cattle on pasture.
The comparisons reflected the three decisions one can make related to pasture management: fertilize pastures without supplement (FERT), supplemented only without fertilization (FEED) and finally the combination of fertilization with supplement (FERT+FEED).
The two fertilized pastures had nitrogen applied at 100 units per acre. Over the two years of the experiment, forage biomass didn’t differ between fertilized and unfertilized pastures, which at first glance would suggest fertilization was unsuccessful.
However, the authors reported forage biomass which is not the same as forage production. This experiment highlights the challenge of measuring pasture intake and feed substitution (trading feed for forage). The FERT cattle could have consumed more of the forage produced while FEED cattle may have consumed less pasture due to the 5.5 lb / day of distillers grains cubes supplementation. Forage biomass appears equal in these groups for different reasons, one due to increased production despite an expected greater forage intake the other lower production coupled with lower consumption due to feeding.
That said, one would think the FERT+FEED group should reflect an increase in forage production due to fertilization plus feed substitution, however these cattle were supplemented at about half (2.6 lbs of distillers cubes per day) of the FEED group and forage biomass was not different.
There are two key variables of pasture fertilization to consider from this experiment. The one we all know; fertilization requires moisture to increase forage growth. Second, fertilization requires the ability to use the increased forage growth in a timely manner. This variable is more important for stockers to consider than cow-calf operation as excessive early pasture growth is more efficiently used by mature cows than growing stocker cattle. If clipping pastures is part of your stocker cattle grazing program, you don’t have a fertility problem.
Fertilization allows for faster green-up and higher stocking rates, but stocking rates need to be flexible over the entire grazing season otherwise performance will suffer due to forage quality in the case of understocking or forage availability in the case of overstocking. Supplementation provides operations greater stocking rate flexibility later in the grazing season during seasonally drier periods.
Gain was greater in the supplemented groups in both years of the experiment, however, neither supplementation program was profitable during the grazing period compared to fertilization alone due to feed cost. Lowering supplement prices would obviously contribute to improvements in profitability of the FEED groups. Alternatively, improvement in supplemental feed efficiency could improve profits as well. The FEED converted at was 8.3 while FEED+FERT was 5.7 lb of supplement per lb of additional gain. Supplemental feed efficiency is normally more favorable at lower feeding rates.
Following these steers to the feedyard highlighted several opportunities for those operations retaining ownership. The two FEED groups required on average 22 fewer days on feed due to the greater feedyard entry weight. Heavier feedyard entry weights resulted in 600 to 627 lbs less feed needed during finishing phase. Not a one-to-one tradeoff for the pasture supplement investment but an indication backgrounding cattle before the feedyard is not always overcome by compensatory gain.
Perhaps more importantly, supplemented cattle tended to have greater marbling scores and higher quality grades despite being managed to a common backfat and carcass weight. The impact of ensuring adequate nutrition during the grazing phase is not a new revelation. Previous work supports the need to “feed” marbling deposition throughout cattle’s life.
These experiments highlight the diversity of opportunities available to cattlemen to reach similar endpoints. For some, fertilization may be key to increased carrying capacity by grazing or hay harvest. Others have the labor resources to use the stability of delivering feed to support higher performance. Regardless your approach, make sure to understand the tradeoffs relative to your production model.
[1] https://doi.org/10.15232/aas.2022-02318 and https://doi.org/10.15232/aas.2023-02434
