Sow responses to varying feeding panes of sorghum based diets
Two studies were done to assess the influence of feeding levels of sorghum based diets on reproduction in primiparous sows. The first study was conducted to asses the effect of replacing maize w i th sorghum in p i q diets in terms of digestibility of energy, prote in, fibre. Four di fferent iso-energetic and iso-nitrogenous diets were formulated to National Research Council (NRC) specifications and fed to eight finishing pigs (four barrows and four gilts) in a latin square designed experiment. The first diet (I) was a maize-soybean control diet. The second (II) was maize based, the third (III) was based on maize and sorghum in equal proportions by weight, while the fourth diet (IV) was based wholly on sorghum. Sunflower and cotton seed cake were the protein sources in diets II to IV. Dietary energy deficiencies were made up for by use of lard. The digestibility coefficients of energy and protein for diets I to IV ranged from (77 to 82.3%) and (69.5 to 85.9%) respectively. There was a progressive improvement ln energy and protein digestibility values with increase of maize ln the diets. In the second study, 24 gilts were fed low (L) and high (H) levels of experimental feed (14.2 MJ/kg DE; 14% CP) in gestation. The low group (L) was given 1 kg of feed per day while the high group was fed 2.1 kg per day. At farrowing gilts in each level • were redistributed to a low (L) and a high (H) levels of lactation feed (14.6 MJ/kg DE; 15% CP) during lactation. The low group was fed 1 kg plus 0.3 kg per piglet in the litter daily and the high was fed 2.1 kg plus 0.5 kg per piglet. Combinations of feeding levels in gesta~ion and lactation resulted in high-high (HH) ,-highlow (HL), low-high (LH) and low-low (LL) levels. Gilt and piglet weights were recorded weekly. Seven blood samples were taken at 30 minute intervals weekly during lactation from 2 sows in each gestation-lactation feeding level SUbgroup, centrifuged and plasma taken for LH assays. Weaning was after a four week lactation when daily feed allowance was reduced to 2 kg. The sows were slaughtered 28 days post-mating for reproductive system and carcass evaluation studies. Gilts on the high plane of feeding gained 30.3 kg while those on low plane ga ined 15.4 kg during gestation. The actual maternal body weight gain was 15.9 and 2.7 respectively (P < 0.05). Litter size, average piglet birth weight and conversion efficiency were unaffected by feeding level (P > 0.05). Over the lactation, the LL group lost 16kg, LH lost 17.1, HL lost 11.2 and HH lost 1.9 kg (P < 0.05). Litter and piglet weight gain was not affected by feeding level (P > 0.05) but feed efficiency was higher (P < 0.05) for the lower level of feeding. High fed sows came back to oestrus eight days earlier than in the other three groups. Decreasing level of feeding was characterised by either prolonged anoestrus or conception failure. In the subsequent gestation, the gilts were slaughtered 28 days after mating. The four feeding levels had no carcass measurement differences at slaughter(P > 0.05). However, sows fed high in gestation released more ova, had heavier ovaries and placentas, higher foetal fluid volumes (P < 0.05) but did not differ from low fed sows in embryo weight (P > 0.05) by slaughter time. Similarly, sows fed high in lactation released more ova and had heavier placenta and embryos (P < 0.05). In contrast there was no difference in foetal fluid volume and ovary and corpora lutea weights with level of feeding during La ct.at i.on . Increasing feed intake over gestation and lactation was associated with increased ovary, placenta and embryo sizes, and higher foetal fluid volumes (P < 0.5). However, the trend showed that these variations were • more dependent on gestation rather than lactation level of feeding. The horn of uterus did not influence any embryo developments. Low fed gilts during gestation had lower plasma levels of luteinizing hormone during the first week of l2lctation but not thereafter. It was therefore concluded that the level of feeding during gestation is important for embryo number and development in the subsequent reproductive cycle.