The influence of processing corn grain fed to ewes during late pregnancy on birth-weight of Finn x Awassi crossbred lambs.
1995
Landau S. | Zoref Z. | Nitsan Z. | Madar Z.
The relationship between corn starch degradability in late pregnancy diets and lambing performance was studied in 60 Finn-Awassi ewes fed diets containing 500 g/d of corn given as whole (WC), extruded (EC) or ground (GC). Lamb birth-weights ranked as follows: single lambs: EC greater than WC greater than GC (NS at 2nd parity, P less than 0.10 at 3rd and higher parities); twin lambs: EC greater than WC = GC (P less than 0.07 at 2nd, P less than 0.02 at 3rd and higher parities). The overall positive effect of EC on lamb birth-weight was significant (P less than 0.03). The ratio between birth-weight of twin lamb litters and maternal weight measured 4 days post-partum in ewes at 3rd and higher parities was 25 per cent greater in EC-fed ewes than in WC- or GC-fed counterparts (P less than 0.03). All parities included, this ratio was 24 per cent greater in EC than in the other groups (P less than 0.11). Litter birth-weight was positively correlated with maternal plasma level of non-esterified fatty acids (NEFA) and negatively correlated with plasma levels of glucose and insulin: 78 per cent of variance in lamb birth-weight could be explained by plasma NEFA (positive correlation) and insulin (negative correlation) concentrations on day 23 pre-partum, or plasma NEFA (positive correlation), insulin and glucose (negative correlations) concentrations on day 9 pre-partum, and ewe body-weight at day 4 post-partum (positive correlation). In conclusion: (i) in prolific ewes at late pregnancy, highly degradable corn starch promotes better fetal growth than moderately degradable corn starch (ii) the positive correlation between NEFA and lamb birth-weight, even in "overfed" ewes carrying single lambs shows that maximal lamb birth-weight is not likely to be maximised without some extent of maternal lipolysis.
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