Livestock Production Science 64 2000 147–165 www.elsevier.com locate livprodsci
Sow factors affecting voluntary feed intake during lactation
a , a
b
J.J. Eissen , E. Kanis , B. Kemp
a
Animal Breeding and Genetics Group , Wageningen Institute of Animal Sciences, Wageningen Agricultural University, P.O. Box 338,
6700 AH Wageningen, The Netherlands
b
Animal Health and Reproduction Group , Wageningen Institute of Animal Sciences, Wageningen Agricultural University, P.O. Box 338,
6700 AH Wageningen, The Netherlands Received 3 March 1999; received in revised form 18 August 1999; accepted 23 September 1999
Abstract
Genetic and environmental changes during the last few decades have resulted in higher milk production and maintenance costs of lactating sows, leading to increased energy requirements, whereas the amount of body fat reserves of, in particular,
young immature sows have decreased and voluntary feed intake may have decreased. As a consequence, present voluntary feed intake of sows during lactation is frequently inadequate to meet nutrient demands. This may influence subsequent
reproduction. In this paper, it is argued that voluntary feed intake of lactating sows should be included in breeding programmes. To underpin this statement, it is reviewed how the sow factors body weight and body composition at farrowing,
litter size during lactation, parity and genotype affect voluntary intake during lactation and possible physiological mechanisms are provided. It is concluded that, for sustainable pig production, the trends of decreasing fat reserves at
farrowing and increasing energy requirements during lactation should be accompanied by a higher feed intake capacity during lactation. Genotype seems the most appropriate sow factor that can be used to realise the desired changes and
selection for a higher voluntary feed intake during lactation is recommended.
2000 Elsevier Science B.V. All rights
reserved.
Keywords : Body composition; Feed intake; Genotype; Lactation; Litter size; Parity; Sows
1. Introduction an attempt to maintain milk production NRC,
1987. Recent work cited below illustrates that Voluntary feed intake of young and immature
nowadays nutrition is more critical for reproduction sows during lactation is frequently inadequate to
than in the past. For example, earlier work of Elsley meet nutrient demands for maintenance, milk pro-
et al. 1969 and O’Grady et al. 1973 clearly duction and body growth Noblet et al., 1990. Milk
indicated no relationship between lactational feed production has a high priority and, if nutrient intake
intake and subsequent reproduction performance. In is insufficient, the sow will mobilise body tissue in
recent studies, however, a low feed intake during lactation, accompanied by excessive weight loss, was
found to be associated with several common re-
Corresponding author. Tel.: 131-317-482-335; fax: 131-317-
productive problems, including an increased interval
483-929. E-mail address
: jaco.eissenalg.vf.wau.nl J.J. Eissen
from weaning to oestrus Reese et al., 1982; King
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 5 3 - 0
148 J
.J. Eissen et al. Livestock Production Science 64 2000 147 –165
and Williams, 1984; Kirkwood et al., 1987a,b, 1990; illustrations that selection for production traits may
Baidoo et al., 1992, an increased incidence of affect voluntary feed intake. Breeding programmes
anoestrus Kirkwood et al., 1987a,b, a lower ovula- putting a high emphasis on production efficiency or
tion rate Zak et al., 1997, a decreased conception leanness rather than on rate of lean growth, can
rate Kirkwood et al., 1987a,b and a higher em- reduce the appetite of growing pigs Smith and
bryonic mortality Kirkwood et al., 1987a, 1990; Fowler, 1978; Ellis et al., 1979, 1983; Smith et al.,
Baidoo et al., 1992. The longer length of lactation in 1991. A reduction in appetite during the growth
the earlier works may have contributed to the lower phase can also be reflected by sows during lactation
sensitivity of sows in the past, because sows mainly Kerr and Cameron, 1996b.
lose body reserves during the first 2–3 weeks of Many factors affect spontaneous feed intake dur-
lactation and start to recover afterwards Revell and ing lactation. For convenience they can be grouped
Williams, 1993. All of the above-mentioned studies under three main headings, although some of them
restricted feed intake during at least part of the interact with each other Revell and Williams, 1993.
lactation in controlled experiments. However, data The three factors are sow e.g. body weight and
analyses of close to ad libitum fed sows on composition, litter size, parity, genotype, environ-
commercial farms also show that a higher feed intake ment e.g. temperature, air quality, management,
during lactation may improve reproductive perform- length of lactation, stock density, disease incidence
ance Koketsu et al., 1996b, 1997; Koketsu and Dial, and diet e.g. digestibility, composition, energy den-
1997. sity, protein and amino acid balance, availability of
According to Whittemore 1996, this turn of water, feeding frequency. As indicated above, cur-
events may have resulted from a change in the pig’s rent selection strategies result in increasing energy
genetic make-up. In dam lines, selection has general- requirements of sows due to higher milk production
ly been for production and reproduction traits. Selec- and maintenance costs, whereas the amount of fat
tion for production traits has resulted in an increase reserves of young sows is decreasing and voluntary
in growth rate, a reduction in backfat and an feed intake may be decreasing. Nowadays, inade-
improved feed efficiency during the growth phase quate feed intake during lactation is particularly
e.g. Vangen and Kolstad, 1986. These changes evident in primiparous sows NRC, 1987, sows fed
during the growth phase are reflected at later stages generously during gestation Baker et al., 1968;
in a reduction in the amount of fat in the body of Dourmad, 1991 and sows in a hot environment
young sows at the times of parturition and weaning NRC, 1987. Therefore, it can be argued that
Whittemore, 1996. Furthermore, maintenance re- voluntary feed intake during lactation should be
quirements at maturity are higher due to a higher considered in breeding programmes. The aim of this
mature body weight. Sows also have higher mainte- paper is to review and provide possible physiological
nance requirements due to the lower fatness Camp- mechanisms for the way in which the mentioned sow
bell and Taverner, 1988. The common breeding factors affect voluntary feed intake during lactation
objective for reproduction focuses on the number of and to investigate if selection for feed intake during
piglets weaned per sow per year Knap, 1990. The lactation should be recommended.
effect of selection for reproduction traits is illustrated by the positive genetic trends for litter size in current
dam lines Knap et al., 1993. Litter size also tends
2. Voluntary feed intake
