Reproductive response of confined West African dwarf sheep fed whole cotton seed and cassava peels during different trimesters of pregnancy

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A total of 23 nulliparous West African Dwarf ewes were used in five treatments to determine which trimester(s) required the utmost nutritional attention during pregnancy. The animals were offered a daily basal diet of 1920 g DM Brachiaria deciin;bens plus 446 g DM Gliricidia sepizim and supplemented with 89 g DM whole cotton seed and 246 g DM dried cassava peels. The supplementary diet was either not offered in the first trimester (T1), second trimester (T2), third trimester (T3), offered in all the three trimesters (T4) or completely withdrawn in all the three trimesters (T5) of pregnancy. The initial weights of the animals were: 16.3 kg (T1), 15.3 kg (T2), 14.7 kg (T3), 15.1 kg (T4) and 15.4 kg (T5). The effects of nutrition on lamb birth weight and pre-weaning growth performance were assessed. Plasma glucose, total protein, albumins and globulins were determined as indices of nutritional state during pregnancy. The relationships between lamb birth weight and these plasma metabolites were also examined. Feed intake and weight gains of animals significantly decreased (p< 0.05) in trimesters where access to DM was restricted. The average total DM1 during full gestation in T4 (704 g/d) was significantly higher than the averages for the other treatments (p<O. 05) except T3 (694 g/d). Animals in T5 also recorded the lowest DM1 (598.3 g/d) compared to all other treatments (p<O.O5). Restricting access to DM1 by withdrawing the concentrate in trimester I, II or III did not significantly influence the total DM1 during 11111 gestation in the respective treatments; T1 (679 g/d), T2 (684 g/d) and T3 (694 g/d). Plasma glucose concentration in T2 significantly decreased from 55.0 mg/dL in trimester I to 50.6 mg/dL in trimester II where the concentrate was withdrawn (p<O.OS) and then slightly decreased (p>0.05) to 49.8 mg/dL in trimester III. The decrease in T3 was from 53.2 mg/dL in trimester II to 46.9 mg/dL in trimester III where the concentrate was withdrawn (p< 0.05) but the level in trimester III did not differ significantly from the 48.8 mg/dL in trimester I (p>0.05). In T5 where the concentrate was withdrawn throughout gestation, the fall in plasma glucose was drastic and consistent but significant only between trimester 1 (48.8 rng/dL) and trimesters 11(39.7 mg/dL) and III (37 mg/dL) p< 0.05) but not between trimesters Ii and III (p—0.05). No significant variation of glucose concentration was observed in the three trimesters of pregnancy in T1 and T4 (v> 0.05). The average plasma glucose concentrations during full gestation were 50.74, 51.79, 48.60, 48.43 and 41.90 mg/dL in T1, T2, T3, T4 and T5 respectively p<0.05). The corresponding birth weights of lambs were 1.7, 1.8, 1,5, 1.6, and 1.2 kg (p<0.05). Regardless of the type of treatment, there was a significant negative correlation between plasma glucose concentration and lamb birth weight (r - 0.0618, p0. 05). It was also observed that the glucose concentration in trimester 11 did not differ significantly in all the treatments (p>0.05) except T5 where complete concentrate withdrawal was imposed (p<0.05). Withdrawing the concentrate supplement in trimester I, II, or Ill also had no significant influence on plasma total protein concentration in the respective treatments; T1, T2, and T3 (p>0.05), but in T4 and T5 where it was respectively offered throughout or withdrawn completely during full gestation, plasma total protein concentration was significantly influenced (p<0.05). There was generally a significant positive relationship between placental weight and lamb birth weight (r = 0.748. p<0. 05) with animals in T2 showing the most superior relationship. Productivity in terms of kg lamb was higher in animals that received some form of supplementation during pregnancy and lactation than those that did not (T5). The pre-weaning growth rate and weaning weight of lambs were significantly lower in T5 compared with the others (p< 0.05). Pre-weaning lamb mortality occurred in T5 (75%) and T4 (25%) but the death in T4 was not attributed to treatment effects It was observed that feed restriction in the second trimester of pregnancy appeared to have no detrimental effect on foetal growth/birth weight. Rather, nutrient restriction in mid pregnancy seemed to have promoted placental growth and function, resulting in higher foetal growth and birth weight and subsequently better pre-weaning lamb growth performance. It was therefore concluded that, increased productivity of adolescent sheep could be achieved by supplementary feeding in the first and last trimesters of pregnancy.
A thesis submitted to the School of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the award of MSc Reproductive Physiology) Degree, 2005