Adsa Logo White Adsa Title White

Effects of differing dietary starch and digestible amino acid supply on amino acid efficiency and lactation performance in dairy cattle.

P. A. LaPierre

Events

06-24-2020

Join P. A. LaPierre on this page for a live text chat!
6:00 PM - 8:00 PM GMT

Abstract:

W119
Effects of differing dietary starch and digestible amino acid supply on amino acid efficiency and lactation performance in dairy cattle.
P. A. LaPierre*1, S. Fredin2, D. A. Ross1, M. E. Van Amburgh1. 1Cornell University Ithaca, NY, 2Adisseo Alpharetta, GA.

Efforts to optimize nitrogen (N) efficiency and improve AA balancing in lactating dairy cattle, particularly when describing the supply and requirements of essential AA (EAA), have demonstrated a relationship between metabolizable AA supply (AAS) and metabolizable energy (ME). Additional data demonstrated that gluconeogenic versus acetogenic substrates providing ME might alter the efficiency of EAA use. The objective was to evaluate milk yield and components in cattle fed diets with 2 levels of dietary starch and 2 levels of EAA supply. Lactating cattle (n = 96; 2.6 � 1.3 lactations, 91 � 22 DIM, 652 � 83 kg BW) were blocked in 16 cow pens (n = 6) by parity, DIM, and BW and enrolled for 60 d as the first of 2 blocks in a randomized incomplete block experiment. Pens were fed a common diet during a 10-d covariate period and randomly assigned to 1 of 4 diets. Diets were fed with 2 levels of dietary starch (23% [LS] and 29% [HS] DM) and 2 levels of AAS (100% [100] and 105% [105] of requirements as described by CNCPS v7). Diets were isocaloric and balanced for AAS, with the 100% MP diets formulated for the optimum gAAS/Mcal ME and the 105% diets formulated at 5% excess AAS. Milk samples were collected weekly from 3 consecutive milking sessions. Results were analyzed using an ANOVA mixed model in SAS (v.9.4) and significance was declared at P < 0.05 and a tendency at P < 0.1. Cattle fed a HS diet consumed more DM (27.2 kg) than cattle fed a LS diet (24.1 kg; P < 0.05). Cattle fed HS105 made more ECM (45.0 kg � 0.66 kg; P < 0.01) than cattle fed LS100 (40.9 � 0.94 kg) and HS100 (40.8 � 0.92 kg) and tended to make more than LS105 (42.8 � 0.66 kg; P = 0.09). The HS105 treatment produced higher milk protein yield compared with other treatments (1.29 � 0.02 kg; P < 0.01) whereas the HS100 (1.13 � 0.03 kg) and LS105 (1.13 � 0.02 kg) diets tended to yield more protein than LS100 (1.04 � 0.03 kg; P = 0.09). Cattle fed the LS105 diet (14.5 � 0.2 mg/dL) had higher MUN (P < 0.05) than LS100 (11.5 � 0.3 mg/dL) and HS105 (11.6 � 0.2 mg/dL) and tended to be higher than HS100 (12.3 � 0.3 mg/dL). The data indicate when ME supply is more gluconeogenic, the efficiency of N and EAA use increases.

Keywords: amino acids, starch, nutritional models.