With feed inputs representing the #1 expense for most dairy operations, and little relief in sight in terms of feed prices, efficient utilization of feedstuffs is a dairy sustainability imperative, according to Dr. Isaac Salfer, Assistant Professor of Dairy Nutrition at the University of Minnesota.
“The most important metric for determining a herd’s whole-farm feed efficiency is feed cost per hundredweight of energy-corrected milk sold,” Salfer stated.
In a recent publication, he cited data that showed the top 10% most profitable dairy farms in Minnesota (in terms of net return) spent 60% as much on feed per cwt. of milk ($9.58) compared to the lowest 10%, who spent $15.61/cwt.
Salfer said outright loss of feed – due factors like shrink and refusals – is one of the two overarching factors that affect whole-farm feed efficiency. The other is the digestive and metabolic efficiency of the cow herself. He identified the following factors that contribute to losses of energy that are wasted on anything other than milk production:
(1) Fecal and urinary losses – Salfer said fecal energy losses occur due to inadequate digestion of feeds, improper feed processing, poor ration formulation, and/or feeding high concentrations of low-digestibility feeds. Digestive efficiency also can be negatively influenced by poor bunk management, decreased eating frequency, heat stress, disease, poor water quality, and even noise. Overfeeding protein can add to urine energy loss because more energy is required to excrete excess nitrogen.
(2) Gas emissions – Rumen fermentation produces byproducts of methane, carbon dioxide, and other gases that are expelled by the cow and lost to the environment.
(3) Heat energy – Rumen fermentation also generates heat, as does metabolism, as nutrients are utilized further in the digestive process. “The total amount of heat an animal loses can be reduced by lowering the total number of chemical reactions – particularly ‘wasteful’ reactions – in digestion,” he stated. He noted feed additives like ionophores can help minimize wasteful digestive processes. Reducing stress also can stem heat energy losses, because any activation of the immune system, which may be triggered by factors like heat stress and metabolic stress, results in unproductive energy consumption.
Salfer pointed out that minimizing wasted energy in cows has dual benefits for both the dairy operation and the environment. Strategically balancing for protein – and, more precisely, specific amino acids – can lower feed costs while also reducing the nitrogen load in the environment. Reducing gas emissions has received much recent attention from an environmental standpoint. “But it also benefits farmers because gases can represent a loss of up to about 10% of total feed energy,” explained Salfer.
Reducing methane emissions without negatively impacting rumen microbial growth is a delicate dance, according to Salfer. He said most ration-based approaches to reducing methane focus on increasing concentration of the volatile fatty acid propionate, because propionate consumes hydrogen that would otherwise fuel methane production.
Finally, Salfer said higher milk production can promote feed efficiency, even if it requires more feed. Lactating cows require about 14-16 pounds of dry matter for basic maintenance of functions like breathing, muscle contraction, digestion, and hormone production. “Because maintenance energy needs are fixed, increased milk production decreases the percentage of energy intake used for maintenance functions compared to milk production, even if total feed intake increases,” Salfer explained.
