title: Lactation responses and amino acid utilization of dairy cows fed low-fat distillers dried grains with solubles with or without rumen-protected lysine supplementation.
abstract: The objective of this study was to evaluate the effects of feeding different amounts of low-fat distillers dried grains with solubles (DDGS) in diets with or without supplementation of rumen-protected Lys (RPL) on lactation responses and AA utilization. Eight multiparous Holstein cows averaging 188 ± 13 DIM were assigned to a replicated 4 × 4 Latin square with a 2 × 2 factorial arrangement of treatments. Dietary treatments were as follows: (1) 15% low-fat DDGS, (2) 15% low-fat DDGS plus RPL, (3) 30% low-fat DDGS, and (4) 30% low-fat DDGS plus RPL. Periods lasted 21 d, with the last 3 d for data collection. Basal diets (without RPL) were formulated using the Cornell-Penn-Miner Dairy model [Cornell University (Ithaca, NY), University of Pennsylvania (Philadelphia), and the W. H. Miner Agricultural Research Institute (Chazy, NY)] to be isonitrogenous (16.9% crude protein) and isocaloric (2.63 Mcal/kg) and inclusion of low-fat DDGS increased at the expense of corn and soybean meal. Inclusion rate of low-fat DDGS and RPL supplementation had no effect on dry matter intake and milk yield, averaging 25.3 ± 0.97 kg/d and 26.9 ± 1.94 kg/d, respectively (means ± standard error of the means). Milk fat and lactose concentrations were unaffected by treatments but milk protein concentration decreased in cows fed treatments with 30% low-fat DDGS compared with those fed treatments with 15% low-fat DDGS (3.49 vs. 3.40 ± 0.12%). Updated predictions from the Cornell-Penn-Miner Dairy model showed a decrease of 25 g of metabolizable protein Lys in cows fed treatments with 30% low-fat DDGS. Compared with cows fed treatments with 15% low-fat DDGS, cows fed treatments with 30% low-fat DDGS had a marked increase in extraction efficiency (49.4 vs. 61.4 ± 2.51%) and a tendency to increase milk protein concentration (3.41 vs. 3.48 ± 0.12%) with RPL supplementation, which supported that Lys supply was inadequate. Despite differences observed in milk protein concentration, milk protein yield was similar across treatments and averaged 0.92 ± 0.06 kg/d. Lack of response on arterial Lys concentration with RPL supplementation leads us to suspect that the RPL product delivered a lower amount of metabolizable Lys than expected. Based on extraction efficiencies, Lys, Arg, and Phe were the first 3 limiting AA across treatments. Supplementation of rumen-protected AA has the potential to be an effective nutritional strategy to supply limiting AA; however, accurate information on the bioavailability of the AA is needed.
authors.affiliation: Department of Animal Science, University of Nebraska-Lincoln, Lincoln 68583.
authors.forename: H A
authors.initials: HA
authors.lastname: Paz
authors.affiliation: Department of Animal Science, University of Nebraska-Lincoln, Lincoln 68583. Electronic address: pkononoff2@unl.edu.
authors.forename: P J
authors.initials: PJ
authors.lastname: Kononoff
mesh_terms: D000596:Amino Acids / Q000008:administration & dosage* / Q000097:blood; D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D002417:Cattle; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D002523:Edible Grain / Q000737:chemistry*; D005260:Female; D007774:Lactation / Q000502:physiology*; D008239:Lysine / Q000008:administration & dosage* / Q000032:analysis; D008892:Milk / Q000737:chemistry; D008894:Milk Proteins / Q000032:analysis; D012417:Rumen / Q000378:metabolism*; D013025:Glycine max / Q000737:chemistry; D003313:Zea mays / Q000737:chemistry
chemical_list: D000596:Amino Acids; D008894:Milk Proteins; D008239:Lysine
keywords: amino acid; dairy cow; extraction efficiency; low-fat distillers dried grains with solubles; rumen-protected lysine