Lambing type and body weight changes in multiparous ewes / Morales-Carrillo et al. ______________________________________________
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INTRODUCCIÓN
Multiparous ewes (Ovis aries) acquire importance in the structure of
a ock because this type of ewes has the highest representation and
productivity with respect to primiparous ewes [1, 2]. Ewe productivity
is determined during lactation, so it is important to identify the factors
that affect it. Body weight at lambing is one of the factors that affect
the productive eciency of ewes, where ewes with a higher body
weight than the average weight produce litters with a higher weaning
weight than ewes with a lower body weight than the average body
weight [3]. A higher body weight at lambing may be related to a
greater amount of body reserves, which are important to support
milk production when the voluntary intake of ewes under grazing
conditions in hot humid climate does not allow covering nutritional
requirements [4, 5]. However, further studies are required to identify
the factors that affect the daily weight gain (DWG) of ewes and lambs
throughout lactation, with the purpose of proposing nutritional
management options to optimize their productive eciency.
The number of lambs at birth is another factor that has a marked
inuence on the productive eciency of lactating ewes, where
litters consisting of two or three lambs have higher birth and weaning
weights relative to litters of one lamb; so the type of birth is a factor
that should be considered in studies aimed at identifying the causes
of variation in the productive eciency of ewes [2, 6]. The objective
of this study was to determine the inuence of the type of lambing on
the productive eciency of multiparous ewes. Collaterally, the effect
of the lambing type and number of weeks postpartum of multiparous
hair ewes on their body weight change and that of their lambs during
lactation was determined. As well as the relationship between daily
weight gain of the ewe and daily weight gain of the lamb
MATERIALS AND METHODS
Animal care
The animals were treated in accordance with the guidelines and
regulations for animal experimentation indicated in Mexican Ocial
Standards [7, 8], on humane treatment in animal mobilization and on
technical specications for the production, care and use of laboratory
animals, respectively.
Animals
Eleven multiparous Blackbelly × Pelibuey ewes and their 17 lambs were
used. All ewes were in their fourth lambing (six with single lambing and
ve with multiple lambing). The study was conducted at an experimental
sheep unit of the Instituto Nacional de Investigaciones Forestales,
Agrícolas y Pecuarias located in Huimanguillo, Tabasco, Mexico.
Location
The municipality of Huimanguillo is located at 17°50’ N | 93°23’W,
at an altitude of 20 masl. It has a warm climate with year–round
rainfall (Af) and a mean annual temperature of 27.8°C [9]. The study
was developed during the northern climatic season (November
2020 to February 2021) and had a duration of 73 days (d). During
this period, information was available for the following climatic
indicators: minimum and maximum ambient temperature (°C) and
accumulated rainfall (mm). The average minimum and maximum
ambient temperatures were 19.0°C and 30.7°C, respectively; the
accumulated rainfall during the study period was 232.5 mm.
Management of ewes prior to lambing
The ewes were fed 30 d prior to the probable lambing date based
on grazing and supplemental feeding. Grazing was carried out on a
pasture with Cynodon plectostachyus in an area of 1.0 ha, which was
divided into ten sections of variable size. Grazing had a duration of
10 hours –h– (08:00–18:00 h) and was of rotational type (on average
the periods of occupation were 3 d in each of the sections for 28 d
of rest). In the grazing sections there were areas with natural shade
provided by Erythrina americana Miller trees.
Feed supplementation consisted of offering commercial feed
(300 g·animal
-1
·d
-1
, 15% crude protein) and mineral salt
(Foscamag®)
at liberty during night housing. The amount of feed supplement
was offered on a group basis. Ewes received in the fourth month of
gestation an application of doramectin (Dectomax® 1 mL·50 kg body
weight
-1
) for the control of gastrointestinal parasites.
Ewes management during lactation
Lactation duration was 56 d. The ewes were fed during the entire
lactation based on grazing and supplemental feeding. Grazing was
on a pasture with a total area of 1.0 ha grazed with C. plectostachyus
and were managed in a similar manner as described for pre–
lambing management. Feed supplementation consisted of offering
commercial feed (500 g·animal
-1
·d
-1
, 15% crude protein) and mineral
salt (Foscamag®) at liberty during night housing.
In the rst postpartum week, the ewes were stabled with her
litters and received C. plectostachyus hay as a grazing substitute. In
the second postpartum week, the ewes went out to pasture for 6h
(8:00–14:00 h) and the rest of the day they were with their litters,
receiving C. plectostachyus hay. From the third week postpartum,
the ewes went out to graze for 10 h (8:00–18:00 h).
Lambs management from birth to weaning
At birth, lambs were identied, weighed and a methylene blue
solution was applied to the umbilicus. In the rst two hours, lambs
were checked for colostrum intake and meconium excretion.
The lambs were kept during the entire lactation in stabling (pen with
a surface area of 77 m
2
). Feeding was based on controlled suckling,
access to a commercial feed supplement (15% crude protein) and hay
of C. plectostachyus and Gliricidia sepium (Jacq.) Walp. The control
of access to suckling was applied from the second week of life of the
lambs for 6 h (8:00 to 14:00 h), later increased to 10 h (8:00 to 18:00 h)
until the end of lactation. The feed supplement was offered starting at
5 d of age, beginning with 100 g·lamb
-1
·d
-1
and was offered as a group.
The total amount of feed supplement was divided into three portions and
offered at the following times: 8:00, 12:00 and 16:00 h. From day 15 of age,
the lambs were given free range hay of C. plectostachyus and G. sepium.
Lambs growth during lactation
The lambs were weighed at 7–d intervals, from birth to the age of
56 d. A clock scale with a capacity of 20 kg and a sensitivity of 25g
(TecnoCor®, DGN 312.01.2005.2576, Mexico) was used.
Response variables
In ewes: a) body weight (kg) at lambing and at 7–d intervals until they
were 56 d postpartum; b) total weight gain (kg) and DWG (g) between
lambing and 56 d of lactation; c) DWG (g) between 7–d periods until