Animal Feed Science and Technology
cows fed rations with very high levels of canola meal
N. Swanepoela,b,∗, P.H. Robinsonb, L.J. Erasmusa
a
Department of Animal and Wildlife Sciences, University of Pretoria, 0001, South Africa
Department of Animal Science, University of California, Davis, CA 95616, USA
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Canola meal is the second largest protein feed in the Northern latitudes and inclusion levels
in dairy rations are expected to increase due to projected large increases in production of
canola seed in Canada. However, a recent study (Swanepoel et al., 2014) showed that even
though higher inclusions of canola meal (CM) had a positive effect on production when CM
directly substituted for high protein corn based dried distillers grains (DDG), that there was
an optimum point at 120–135 g/kg of diet dry matter (DM) after which animal performance
seemed to decline. Only the amino acids (AA), methionine (Met), phenylalanine (Phe) and
leucine (Leu) could have limited production based upon plasma AA concentrations at the
highest CM inclusion level. Our objective was to determine if either Met or Phe, or both,
was limiting performance of early lactation dairy cows fed a ration containing 180 g/kg
of diet DM as CM, by supplementing a calculated target of 7.5 g of intestinally absorbable
Phe/cow/day and/or 8.0 g of intestinally absorbable Met/cow/day in ruminally protected
(RP) forms to four pens of ∼320 early lactation cows/pen in a 4 × 4 Latin square with 28
days experimental periods. Dry matter intake was not affected (avg.: 27.6 0.4 kg/day)
by feeding either of the RP AA, or the combination. Phenylalanine supplementation alone
had no effect on milk production or composition, and body condition score (BCS) change
compared to Control. Supplemental Met alone modestly increased (P<0.01) milk protein
and fat content, while decreasing (P<0.01) milk lactose content and yield, but with no impact
on BCS change compared to Control. Combination Met and Phe supplementation decreased
milk and lactose yields, as well as lactose content (P<0.01), while increasing milk protein
content and the BCS change (P<0.01). Urine volume (avg.: 16.7 0.31 L/day) and flow of
microbial protein (MCP) from the rumen (avg.: 2092 52.7 g CP/day) were not affected by
any treatment. Plasma Met levels increased (P<0.01) with both Met treatments and plasma
tryptophan (Trp) levels decreased (P<0.01) with both Phe treatments. However, plasma Phe
levels did not change with any treatment. Results are interpreted to suggest that delivery of
Met with RP Met feeding was higher than animal requirements and caused an oversupply
of Met. Addition of Phe to the Met supplementation changed the way energy was utilized
by the cows, redirecting energy liberated by Met from milk components toward BCS gain.
Received 15 October 2014
Received in revised form 1 April 2015
Accepted 2 April 2015
Keywords:
Spot urine purine
Estimated microbial flow
Plasma amino acids
Protein feeding
Abbreviations: AA, amino acid; ADF, acid detergent fiber; ADICP, AD insoluble CP; ADIN, acid detergent insoluble N; AL, allantoin; aNDF, amylase-treated
NDF; aNDFom, aNDF free of residual ash; BCS, body condition score; BCAA, branched-chain AA; BW, body weight; CM, canola meal; CP, crude protein;
CR, creatinine; DC305, DairyComp 305 management system; DDG, dried distillers grains; DHIA, Dairy Herd Improvement Association; DIM, days in milk;
DM, dry matter; MCP, microbial CP; NDF, neutral detergent fiber; NEL, net energy for lactation; OM, organic matter; PD, purine derivatives; RDP, rumen
degradable CP; RP, rumen protected; SCC, somatic cell count; SG, specific gravity; TMR, total mixed ration; TP, true protein.
∗
Corresponding author at: Department of Animal and Wildlife Sciences, University of Pretoria, 0001, South Africa. Tel.: +27 79 891 8920.
0377-8401/© 2015 Elsevier B.V. All rights reserved.