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North Carolina State University Return to main menu Comparative Assessment of Calcium Salts of AO35 and AO75 Fed to
Lactating Dairy Cows V. Fellner and J. W.
Spears Introduction Inclusion
of supplemental fats in lactating cow diets is a common practice for
nutritional as well as economical reasons. Adequate energy and fiber are
essential for dairy cows particularly during peak lactation. Increasing the
energy content by varying the amount of grain can reduce the level of forage
in the ration. Feeding fat however increases energy density of the diet without
lowering total fiber content. However, the type of fat and amount included in
the ration is very important. Long chain fatty acids are not fermented in the
rumen but are rapidly biohydrogenated by rumen microorganisms. If included in
high amounts long chain fatty acids can be toxic to microbial populations and
exert a detrimental affect on rumen fermentation. Typically, supplemental
fats included in amounts greater than 5% of diet dry matter can depress milk
fat and milk yield. The effect is greater with unsaturated fatty acids
compared with saturated fats. Fats that are protected from biohydrogenation
have a less inhibitory effect on the cellulolytic organisms in the rumen and
pass into the lower tract relatively intact. Unsaturated fatty acids, have been
shown to have anti-atherogenic properties. An increased passage of intact
fatty acids from the rumen will increase their content in milk. Increasing
the content of unsaturated fatty acids in milk is consistent with improving
the nutritional qualities of milk. In a previous in vitro study, calcium
salts of AO35M provided a stable fermentation pattern when included in forage
diets or lactating cow rations containing high concentrate. This study is
designed to determine the effects of calcium salts of AO35 and AO75 on
lactation performance of Holstein cows. Experimental Procedures
Twenty-eight Holstein
cattle in early lactation were blocked by milk production, days in milk and
parity into 4 groups of seven cows each (Table 1). Each
group was randomly assigned to one of four treatments as follows: 1) Control
(no supplemental fat); 2) Prilled fat; 3) Calcium soap of AO35M and, 4)
Calcium soap of AO75. Fat supplements replaced the corn in the concentrate
mix and were included in amounts to represent 3.2% of total dietary DM. The
basal diet consisted of corn silage, alfalfa haylage, whole cottonseed,
nutrimax bypass protein and the concentrate mix and was fed as a total mixed
ration. Ingredient composition of the diets and concentrate mix is in Table 2 and Table 3, respectively.
Cows were housed in free stalls equipped with Calan gates. All cows were
allowed to adapt to the Calan gates for 2 weeks before being fed the
experimental diets for a total of 90 days. Feed was offered twice daily at
0800 and 1500 in amounts to allow for ad libitum consumption. Individual feed
intakes were measured daily. Daily dry matter intake for all days was
calculated by drying weekly feed composite samples at 50oC for
48h. Milk production was measured daily, and milk fat and protein were
analyzed at 30 and 90 days. Separate aliquots of milk samples were frozen at
d 30 and d 90 at -70oC for subsequent analysis of milk lipid
profile. Body weights were taken before (day 0) and at the end of the trial
(day 90). Data were analyzed as a randomized complete block design using the
general linear models procedure of SAS. Results and Discussion
During the feeding trial three
batches of AO35 and two batches of AO75 were received for inclusion in the
experimental diets. Upon arrival, a representative sample from each new batch
of the fat supplement was obtained and immediately analyzed for dry matter
and total fat content. The amount of AO35 and AO75 that was included in the
respective diets was adjusted based on the batch dry matter and fat content.
The fat and dry matter content of the supplemental fat sources is reported in
Table 4. Dry matter intake was
higher by cows fed the control diet (Table 5). Cows fed
the AO75 fat supplement had numerically lower intakes but they were not
significantly different from the control diet. The prilled and AO35 fat
supplements depressed dry matter intake. It has been suggested that the
acceptability of fat sources can vary (Grummer et al., 1990). Although both
AO35 and AO75 had a relatively high moisture content and strong odor compared
to the prilled there did not seem to be any problem with palatability of the
fats used in this study. Effects of dietary addition of various fats on feed
intake have been variable. Grummer (1988) included prilled fatty acids in
diets of lactating cows and reported no effect on intake. In another study
(Andrew et al., 1991) addition of calcium salts of long chain fatty acids to
the diets of lactating cows decreased dry matter intake. Variation in dry
matter intake may be related to the type of fat included in the diet as well
as the level of total fat content in the feed. With oilseeds and liquid fat
it is recommended not to exceed 6 % of total ration. However, with inert fats
one may include them at 8 % of total ration dry matter. Body weights were higher
for the control cows compared to either the prilled or AO35 treatments. Cows
fed the AO75 fat supplement had similar body weight when compared to all
treatments (Table 5). Milk yield was highest
when cows were fed AO75. Milk yield with AO35 was similar to the prilled supplement
but both fat supplements resulted in significantly lower milk production
compared to the control (Table 5). The 4% FCM yields
were similar between AO75, control and prilled treatments; AO35 had the
lowest 4% FCM yield. Feeding AO35 had a significant effect on percentage milk
fat in comparison with the control and prilled treatments. Feeding AO75
resulted in similar milk fat percentage compared to the control and prilled
treatments (Table 5). Effect of feeding supplemental
fat has shown to have a variable response on milk fat percentage. Diets high
in fat or low in ruminally inert fat can have a negative effect on
cellulolytic organisms and fiber digestion. A reduced fiber digestion can
lower the acetate to propionate ratio and subsequent de novo fatty acid
synthesis in the mammary gland. Additionally, the biohydrogenation of fatty
acids results in the production of trans fatty acids that are transported
into milk and have been implicated in depressing milk fat. Milk protein percentage
decreased with the AO35 and AO75 fat supplements compared to the control;
prilled fat had similar milk protein percentage compared with either AO35 or
AO75. Feeding fat has shown to decrease milk protein percentage (Andrew et
al., 1991; Palmquist, D.L. 1984). The yield of milk fat and milk protein was
similar across all treatments with the exception of a lower milk fat yield
with the AO35 fat supplement (Table 5). Lactation efficiency, expressed
as kilograms of milk per kilogram of DMI, was not different across all
treatments (Table 5). Efficiency, expressed as kilogram
of FCM per kilogram of DMI increased (P <0.05) with the addition of AO75
and prilled, compared to AO35. The saturated fatty acids
in milk from C8 to C12 tended to be lower with the AO35 treatment (Table 6). All fat supplements reduced C14 content in milk
compared to the control with AO35 and AO75 resulting in the greatest
reduction. The content of palmitic acid (C16:0) declined (P <0.05) with
AO35 and AO75 compared to either the prilled or no fat control treatments.
Fatty acids with 14 or less carbons are derived from mammary de novo
synthesis. There was no effect of fat supplementation on stearic acid (C18:0) content in milk. However, both
AO35 and AO75 increased oleic acid content (C18:1) in milk compared to the
control. The increase in C18:1 was seen in both the cis and trans isomers.
The increase in trans C18:1 was highest for AO35 followed by AO75. The AO35
and AO75 were both effective in increasing the C18:1 to C16:0 ratio. Ratios
of C18:1 to C16:0 in milk fat were 0.91, 0.98, 1.44, and 1.35 for the
control, prilled, AO35 and AO75 diets, respectively. This change in milk
composition is desirable and is consistent with improved nutritional
qualities associated with increased consumption of milk and milk products
(Mansbridge and Blake, 1997; Maijala, K. 2000). Both AO35 and AO75
increased (P <0.05) the linoleic acid (C18:2) content in milk fat. Feeding
AO35 or AO75 more than doubled the linoleic acid content compared to either
the control or prilled fat (Table 6). Increased C18:2
levels in milk are consistent with reduced rates of ruminal biohydrogenation
of dietary unsaturated fatty acids. Feeding AO35 and AO75
increased (P <0.05) the conjugated linoleic acid (CLA) content in milk fat
(Table 6). Conjugated linoleic acid consist of a group
of positional and geometric conjugated dienoic isomers of linoleic acid, two
of which (cis-9, trans-11 and trans-10, cis-12 CLA) have been shown to
possess numerous beneficial physiological attributes including having anticarcinogenic
properties (Parodi, P.W. 1997) and enhancing growth and feed efficiency in
young rodents (Pariza et al., 2001). Increases in milk C18:1,
C18:2 and CLA can partly be explained by a reduction in ruminal
biohydrogenation suggesting that both AO35 and AO75 were inert in the rumen. Summary Supplemental fat was
included at 3.2 % of diet dry matter. Accounting for the fat content of corn
silage, whole cottonseed, and corn in the concentrate mix, total fat level in
the basal ration was formulated to be approximately 5 %. This resulted in a
total fat content of the experimental diets of 8.2 %. It seems that both the
prilled and AO35 fat sources depressed dry matter intake when included in
diets with total fat content of 8%. A depression of intake was not observed
for the AO75 fat source. Lower intakes resulted in reduced milk yields for
both the prilled and AO35. In contrast, AO75 resulted in the highest milk
production. Milk yield expressed as kg of milk per kilogram of dry matter
intake was not affected by fat source however AO75 supported numerically
higher efficiencies. Milk efficiency expressed as kg of fat corrected milk
per kg of dry matter intake was increased with the AO75 fat source. Both the
AO35 and AO75 fat supplements remained relatively inert in the rumen
resulting in an increased passage of the unsaturated linoleic acid into milk.
The AO35 resulted in a higher trans fatty acid production that lowered milk
fat. It seems that AO75 is relatively inert in the rumen and can be included
in diets already high in fat content. The AO75 fat supplement did not depress
intake, supported high milk yields and improved milk fatty acid composition
consistent with enhanced health benefits. ReferencesAndrew, S.M., H.F. Tyrrell, C.K. Reynolds, and
R.A. Erdman. 1991. Net energy for lactation of calcium salts
of long-chain fatty acids for cows fed silage-based diets. J. Dairy Sci.
74:2588. Grummer, R.R. 1988. Influence of prilled fat and
calcium salt of palm oil fatty acids on ruminal fermentation and
nutrient digestibility. J Dairy Sci. 71:117. Grummer, R.R., M.L.Hatfield, and M.R. Dentine.
1990. Acceptability of fat supplements in four dairy
herds. J. Dairy Sci. 73:852. Maijala, K. 2000. Cow milk and human development
and well-being. Livestock Production Sc. 65:1. Mansbridge, R.J., and J.S. Blake. 1997.
Nutritional factors affecting the fatty acid composition of bovine
milk. Br. J. of Nutr. Suppl. 1, 78: S37. Palmquist, D.L. 1984. Use of fat in diets for
lactating dairy cows. Fats in animal nutrition. J.Wiseman, ed.
Butterworths, London, Engl.
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