Effects of feeding human-inedible feedstuffs to lactating cows to improve nutriet conversion efficiency

Abstract

Dairy cattle, being ruminants, can utilize feeds that are of little nutritional value for humans and other monogastrics. Cattle can convert these ingredients into a valuable human-edible product: milk. Inclusion of such feed ingredients in dairy rations can improve the human-edible production efficiency of milk, defined as human-edible product divided by human-edible inputs. The objective of this study was to evaluate a diet composed only of feedstuffs that are inedible or mostly inedible to humans, with the goal of improving nutrient conversion efficiency. Twelve multiparous Holstein cows (231±40 days in milk and 34.4±7.2 kg/d of milk yield at the start of experiment), were studied in a 3×3 Latin square and received the following treatments: 1) Normal total mixed ration (TMR) for a lactating cow (CON); 2) TMR composed of human inedible feedstuffs (HIF); and 3) HIF with top-dressed rumen-protected amino acids [77 g/d Aji-pro-L (Ajinomoto, Chicago, IL) and 45 g/d MetaSmart (Addiseo, Antony, France); HIF-AA]. The HIF diets consisted of hay (triticale and red clover), corn hominy, corn gluten feed, wheat middlings, spent coffee grounds, whole cottonseed with lint, molasses, and a vitamin/mineral mixture. The study includes three periods lasting 21 days each; feed intake and milk yield were recorded and milk samples were collected over the last 4 days of each period. Cows were housed in tie-stalls and milked twice daily. Preliminary results from period one showed a decrease in milk yield for both the HIF diets [36.2 kg/d (CON) vs. 24.3 kg/d (HIF) and 25.8 kg/d (HIF-AA); P <0.001]. Conversion efficiency of both energy and protein were not improved with either of the HIF diets, likely because of the substantial drop in milk yield. Although avoiding human-edible feedstuffs can in some cases improve human-edible production efficiency, this is not the case when the resulting diet dramatically reduces milk yield.