59 The relationship between flush feeding on placenta characteristics and lamb birth and weaning weights in Dohne merino sheep

The aim of this study was to determine the relationship between placenta characteristics and weights of lambs from birth until weaning. A total of 100 Dohne merino ewes with weights between 48 and 62 kg were selected to GATES method as the farms’ breeding selection criteria. The ewes were divided into two groups, the flush fed (treatment) and non-flush fed group (control). All ewes were on natural grazing for 8 h daily. The treatment group was supplemented with ~500 g per animal per day of lick ration (milled maize, salt, and protein lick Maxiwol Concentrate [Voermol]) every afternoon after grazing for 6 weeks before mating season, during mating, and the early stages of pregnancy until placental development ceased (17–90 days after mating). Teaser rams were used to detect ewes on heat. Ewes were randomly allocated to a ram for hand-mating in the morning from 0700 to 0900 hours for 42 days. Pregnancy diagnosis was conducted twice using a transabdominal ultrasound, 52 days after hand-mating and 30 days after the first scan. The lamb’s weight, sex, and birth type were recorded after lambing. Placentas were weighed and recorded after they dropped naturally. Cotyledons were counted to obtain the total cotyledon number (TCN) and measured individually using a manual caliper and recorded for classification into three separate groups according to diameter: small (CNs, <10 mm), medium (CNm, <10–30 mm), and large (CNl, >30 mm). Placenta characteristics were determined based on placenta weight (PW), TCN, and placental efficiency (PE), which was calculated by dividing the birth weight (BW) by the PW. Lambs were weighed biweekly after lambing, and live weight gain was monitored until weaning. The analysis of variance (ANOVA), mixed ANOVA, Kruskal-Wallis test, Pearson’s product-moment correlation, and the Shapiro-Wilk test were used for statistical comparison and determination of the relationships between the variables. The results indicated no significant differences between the flushed and non-flushed groups (P > 0.05) in terms of PW (0.52 ± 0.14 kg vs. 0.50 ± 0.13 kg), CNs (3.43 ± 2.70 vs. 3.19 ± 0.13), CNm (68.80 ± 12.00 vs. 71.30 ± 14.81), CNl (7.47 ± 7.97 vs. 6.56 ± 5.81), TCN (79.70 ± 9.08 vs. 81.04 ± 15.70), and PE (12.3 ± 2.33 vs. 11.4 ± 1.84) respectively. There was a difference (P < 0.05) in weights at mating and lambing in favor of the flushed group. The live weight of the ewes did not differ (P > 0.05) 6 weeks before mating but did differ (P < 0.05) at mating (59.07 ± 4.02 kg vs. 56.56 ± 4.06 kg) and before lambing (74.44 ± 7.41 vs. 63.85 ± 6.25 kg). Additionally, the correlation between the BW and PW in the flushed (r = −0.1647609, P > 0.05) versus non-flushed (r = 0.333661, P > 0.05) group was not significant. However, significant differences were observed in lamb weights between the groups over time, with a 10% mean difference in the flushed group (P < 0.05). Although flush feeding had no significant influence on placenta characteristics (PW, CN [s,m,l], TCN, PE) and BW, a carry-over effect was observed over time in the live weight gain of lambs until weaning, indicating flush feeding is beneficial to lambs’ growth and survival.