Reproduction in Domestic Animals - Facultad de Ciencias Veterinarias

16 t h International Congress on Animal Reproduction
Poster Abstracts 83
P166
Short term nutritional supplementation improves
reproductive performance in ewes maintained under
extensive conditions in arid central Mexico
Muñoz-Gutiérrez, M 1 *; Scaramuzzi, RJ 2 ; Escobedo Alcántara, JC 3 ; Trejo-
González, A 4 ; Retana-Márquez, MS 1 ; Damian-Matzumura, P 1 and Borregos
de Patria Nueva, AC 5
1Reproductive Biology Departament, Universidad Autónoma Metropolitana
Iztapalapa 09340 Mexico City, Mexico; 2 Department of Veterinary Basic
Sciences, Royal Veterinary College, Hawkshead Lane, North Mimms Herts
AL9 7TA, United Kingdom; 3 Fundación Mexicana para el Desarrollo Rural
Tepeji del Río A.C. 42850 Hidalgo, México; 4 Medicina Veterinaria y
Zootecnia. Facultad de Estudios Superiores Cuautitlán, Universidad Nacional
Autónoma de México, 54700 Cuautitlán Estado de México, Mexico;
5Comunidad de Patria Nueva Hidalgo, Mexico
In the arid regions of Mexico (Hidalgo, Central Mexico) sheep are
managed under extensive conditions on pastures that are of poor
nutritive value. The development and transfer of a simple and
inexpensive technology to improve the reproductive performance of
these flocks would be a significant economic benefit to these
subsistence farmers. Short-term nutritional supplementation of ewes
with a high energy and high protein diet for the last three days of the
oestrous cycle increases litter size of sheep managed under more
favourable grazing conditions in Australia, Uruguay and Europe. The
present trial was carried out to determine if short-term nutritional
supplementation of ewes grazing poor quality pasture in the arid zone
on central Mexico could improve their fertility. Seventy five mixed
breed (Corriedale X Rambouillet X Suffolk) adult cycling ewes
(median BCS = 2) were treated in the breeding season for 11 days
with progestagen sponges and 500 IU of eCG injected on the day of
sponge removal. The animals were supplemented for seven days with
a diet consisting of 250 g of rolled corn, 140 g of soya bean and 950 g
of alfalfa hay per animal per day. The diet was offered to the animals
starting three days before sponge removal and continuing until four
days after sponge removal. Twenty seven control ewes were allowed
to graze the available native pasture and their oestrous cycles were not
synchronized. The proportions were analyzed using the Chi squared
test. Following the introduction of fertile males, 81% (61/75 females)
of the ewes fed the supplement displayed oestrous behaviour 1.54 ±
0.05 days (mean ± SEM) after sponge removal and all 61 animals
became pregnant at the induced cycle. Of the 27 control ewes only 8
(30%) mated and only 5 (18.5%) became pregnant (P 70 days after lambing. Ovarian activity was
considered as cyclic if the P4 level was more than 3.2 nmol/l at least
in one sample, e.g. in 20 (37%) and 13 (43%) of the HPM and TS
ewes, respectively. The distribution of various MnII and RsaI
genotypes was quite similar in the two breeds (in HPM: MnII
AA=19%, AB=51%, BB=31%; RsaI AA=23%, AB=56% BB=21%;
in the TS: MnII AA=14%, AB=54%, BB=32%; RsaI AA=11%,
AB=61%, BB=28%; in case of both RFLP sites allele “A” means the
absence of the cleavage site). Association between genotypes and
seasonality was significant (P