Livestock Production Science 65 2000 143–153 www.elsevier.com locate livprodsci
Associative effects on total tract digestibility in horses fed different ratios of grass hay and whole oats
C. Palmgren Karlsson , J.E. Lindberg, M. Rundgren
Swedish University of Agricultural Sciences , Department of Animal Nutrition and Management, P.O. Box 7024, S-750 07 Uppsala,
Sweden Received 5 March 1999; received in revised form 18 October 1999; accepted 27 October 1999
Abstract
The present experiment was performed according to a 4 3 4 Latin square design with diets composed of on dry matter DM basis the following ratios of grass hay to whole oats: 100:0 O0, 80:20 O20, 60:40 O40 and 40:60 O60. Four
mature Standardbred geldings weighing 493 S.D. 34 kg were used. The digestibility of DM, organic matter and energy dE increased in a curvilinear pattern with the increasing inclusion levels of oats. It is suggested that this was a reflection of
the significantly lowered digestibility of nutrients and particularly of fibrous components for the O60 diet as compared with the other three rations, thus resulting in negative associative effects between grass hay and oats. On the basis of the present
data, and excluding the results of the O60 diet, the digestibility of dE of oats was estimated to be 75. As an expression of the associative effect at the O60 level, the dE of the total diet was estimated to be 58, as compared with 63 when
estimated on the oats value of 75 and the O0 diet, resulting in a depression of dE of the total diet by 8, mainly affecting the utilization of fibrous components. Urinary energy losses decreased with increasing level of oats.
2000 Elsevier
Science B.V. All rights reserved.
Keywords : Horses; Hay; Oats; Digestibility; Associative effects; Fibre; Nutrients
1. Introduction Martin-Rosset et al. 1984, the digestibility of horse
rations is equivalent to the weighted sum of the In computing rations for horses it is assumed that
nutrients supplied as forages and the associated the nutritive value of a diet corresponds to the sum
amounts of concentrates. This assumption is sup- of the individual feedstuffs included. According to
ported by other studies Hintz et al., 1971a,b; Martin-Rosset and Dulphy, 1987; Vermorel et al.,
1991, in which no associative effects were observed between dietary components and diet digestibility.
Corresponding author. Tel.: 146-18-672-094; fax: 146-18-
However, it should be noted that the systematic
672-995.
effect of diet composition on the digestibility of
E-mail address
: carina.palmgren-karlssonhuv.slu.se
C. Palmgren Karlsson
fibrous components was not evaluated by these
0301-6226 00 – see front matter
2000 Elsevier Science B.V. All rights reserved. P I I : S 0 3 0 1 - 6 2 2 6 9 9 0 0 1 7 8 - 5
144 C
. Palmgren Karlsson et al. Livestock Production Science 65 2000 143 –153
authors, with the exception of Hintz et al. 1971a,b. 2. Materials and methods
In contrast, Thompson et al. 1984 found associa- tive effects for several nutrients, implying that the
2.1. Experimental design and animals digestibility of the total ration was not equivalent to
the weighted sum of the individual components, in Four hay-based rations with increasing proportions
agreement with Kienzle et al. 1999. The literature of oats were fed according to a 4 3 4 Latin square
cited deals only superficially with the effect of diet design. Four Standardbred geldings 4–11 years old
composition on the digestibility of individual fibrous with an average body weight BW of 493 S.D. 34
components in mixed rations fed to horses. kg were used. The horses were weighed before and
There are several factors i.e. diet composition, after each collection period.
level of feed intake, feeding routines that could Each experimental period comprised 14 days, 9
influence ileal digestibility of nutrients in diets for days of adaptation to the new diet followed by a
horses, and thus indirectly also influence hindgut 4-day period of quantitative and separate collection
fermentation Meyer et al., 1982; Schwabenbauer et of faeces and urine. The change in rations between
al., 1982; Radicke et al., 1991. When comparing experimental periods was made gradually in the first
feeding with 4 g versus 2 g starch kg body weight 3 to 4 days of the adaptation period. The collection
BW, Meyer and Landes 1994 observed that the period was divided into two sub-periods of 2 days
postprandial pH of the jejunal chyme decreased each with 1 day of rest in between, to reduce the
substantially. As demonstrated by Kienzle 1994 discomfort for the horses.
high levels of starch oats and barley in the small During the adaptation period and the day of rest
intestine decreased starch digestibility, a result of the the horses were kept in individual pens and had
intestinal pH dropping below the optimal pH of access to a common grass free paddock 5 to 7 h per
intestinal a-amylase. day. During the 4 days of faeces and urine collection
The caecum and colon are the predominant sites of the horses were kept in metabolism stalls equipped
fibre digestion in the horse. The microbial digestion with rubber mats. The horses were not given any
in the hindgut depends on the nature of the ration additional exercise.
Kern et al., 1974; Tisserand et al., 1980; Meyer et al., 1995. The proportion of lignified products in
2.2. Diets and feeding plant cell walls generally influences the development
of the cellulolytic activity and biomass in the large The horses were fed rations consisting of grass
intestine Tisserand, 1989. In addition, the propor- hay, harvested in a late state of maturity, and whole
tion of roughage to concentrate in the ration in- unprocessed oats. The chemical composition of the
creases VFA production Schwabenbauer et al., feedstuffs is shown in Table 1. Dietary treatments
1982 and the excretion of H and CH
in the consisted of, on dry matter DM basis, the follow-
2 4
exhalation Nyari, 1992. The concentrate composi- ing ratios between hay and oats O: 100:0 O0,
tion with different ileal starch digestibility might also 80:20 O20, 60:40 O40 and 40:60 O60. The aim
influence the hindgut microbial activity Radicke et was to provide the horses with the same daily
al., 1991. Furthermore, by increasing feed intake amount of DM and gross energy GE on a BW basis
Meyer et al. 1982 demonstrated an increase in the in all treatment groups Table 2. The daily feed
caecal VFA concentration, as well as a marked intake varied depending on BW and was for ration
decrease in pH. O0: 7.4–8.9 kg hay; ration O20: 5.9–7.1 kg hay and
The aim of this investigation was to study the 1.5–1.8 kg oats; ration O40: 4.4–5.3 kg hay and
effects of varying the dietary ratio of hay and oats on 3.0–3.6 kg oats and for ration O60: 3.0–3.6 kg hay
nutrient digestibility and urinary nitrogen and energy and 4.4–5.3 kg oats. A slight difference in daily GE
losses in mature Standardbred geldings, and to intake between O0 and O60 occurred. For all treat-
determine the influence of associative effects be- ment groups the daily feed allowance was 16 g feed
tween feedstuffs on nutrient digestibility. air dry kg BW and covered the maintenance
C . Palmgren Karlsson et al. Livestock Production Science 65 2000 143 –153
145 Table 1
2.3. Collection of samples
Chemical composition g per kg DM and gross energy content MJ kg DM of hay and oats
Feed samples were collected at every feeding
Hay Oats
occasion, and after each collection period, they were
Organic matter 952
966
pooled, mixed, sampled and kept at 2 208C. Faeces
Crude protein 65
130
were collected several times during the day directly
Crude fat 8
40
on the rubber mats and stored at 1 108C. At the end
a
Starch 1
418
b
of each collection day the faeces were mixed,
Sugars 96
12
sampled and frozen 2208C. Urine was collected
Total fibre 782
365 Neutral detergent fibre
617 268
with a plastic funnel attached to the horse with a
Acid detergent fibre 354
128
girth, and connected with a tube to a can containing
Crude fibre 311
106
1 l 10 sulphuric acid to keep pH below 3. Each
Lignin 75
47
collection day the urine was weighed, made up to
Gross energy 18.5
19.3
constant volume with water, sampled and frozen
a
Sum of starch and maltodextrins.
2208C.
b
Sum of fructose and glucose.
2.4. Chemical analyses requirements for energy and protein, according to the
Swedish standards
LBS, 1989;
metabolizable Feed and faeces analyses were performed on oven
0.75
energy ME MJ day 5 0.55 3 BW and 5.5 g
dried 658C, 24 h samples after milling through a digestible crude protein CP MJ ME. The horses
1-mm screen. DM, ash and crude fibre CF were were fed twice a day at 08:30 and 16:30 h with the
determined according to the official methods given daily feed allowances evenly distributed. Hay was
by Jennische and Larsson 1990. CP was based on given 15 min before the oats. Water and salt blocks
total nitrogen N content also including urine were offered ad libitum. A commercial mineral
analysis determined according to Kjeldahl Nordisk ´
mixture 50 g day; 14.6 Ca, 6.6 P and 7.0 Mg Metodikkommitte, 1976 and multiplied by 6.25.
was given once a day in the adaptation periods until Crude fat EE was analysed according to the EEC-
2 days before each collection period. method B Larsson, 1989. Starch and sugars were
Table 2 Daily dietary intake of nutrients g kg BW and gross energy kJ kg BW
Ratios hay:oats O0 100:0
O20 80:20 O40 60:40
O60 40:60 S.E.M.
a b
b b
Dry matter 15.5
15.3 15.3
15.2 0.04
Organic matter 14.7
14.6 14.6
14.6 0.04
d c
b a
Crude protein 1.0
1.2 1.4
1.6 0.01
d c
b a
Crude fat 0.1
0.2 0.3
0.4 0.003
e d
c b
a
Starch 0.0
1.3 2.5
3.8 0.02
f a
b c
d
Sugars 1.5
1.2 1.0
0.7 0.01
a b
c d
Total fibre 12.1
10.7 9.4
8.2 0.07
a b
c d
Neutral detergent fibre 9.5
8.4 7.3
6.3 0.05
a b
c d
Acid detergent fibre 5.5
4.7 4.0
3.4 0.03
a b
c d
Crude fibre 4.8
4.2 3.5
2.9 0.02
a b
c d
Lignin 1.2
1.1 1.0
0.9 0.01
b b
ab a
Gross energy 287
287 288
290 0.7
a – d
Least square mean values within rows with differing superscript letters differed significantly: P ,0.05.
e
Sum of starch and maltodextrins.
f
Sum of fructose and glucose.
146 C
. Palmgren Karlsson et al. Livestock Production Science 65 2000 143 –153
analysed according
to Larsson
and Bengtsson
3. Results
