Supplementation of a flock of the Pampinta breed in the last third of gestation in the semiarid Pampeana Region

Abstract

The aim of this work was to study the effects of supplementation during the final 45 d of gestation on several productive traits in brood ewes of varying body condition of a flock of the Pampinta breed at the experimental farm of the Faculty of Agronomy of the Universidad Nacional de La Pampa, located at 36 ° 46’S latitude and 64 ° 16’ W longitude. Ninety Pampinta ewes of different ages were served by natural mating during a 21-day period in April. At the time of the ultrasound examination, 74 pregnant ewes were separated from the rest of the flock. Of these, 36 eventually gave birth to twin lambs and were the object of this study. Body condition of the mothers was measured three times: ultrasound examination, parturition, and 38 d after the mean date of parturition. The experimental model used incorporated a 2 x 2 factorial arrangement of the factors:feeding program and body condition, each with two levels; those of the first factor were either grazing only or grazing plus supplement and those of the second factor were low and high body condition. Grazing took place on a green winter grain crop (Secale cereale) with 73% in vitro digestibility and 18% crude protein. The supplement supplied 3Mcal ME/kg and was fed at the rate of 0.6 kg daily. ANOVA and mean difference tests were used to analyze data of productive variables birth weight and liveweight gain during the first month of life of the twin lambs. The proportional survival rate of twin lambs until 38 d after the mean date of parturition was analyzed by mean difference test. Supplementation of the ewes that gestated and gave birth to twin lambs showed different response to supplementation depending on the initial body condition. Significant differences were not found for the variable daily gain during the first 38 d of life, but there was a positive effect of supplementation on the survival of twin lambs.