Animal and Poultry Science

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Biological and economic response of laying hens to dietary isoleucine, methionine, lysine and energy.
(1980) Griessel, Munro.; Gous, Robert Mervyn.
No abstract available.
The effect of group size and floor-space allowance on the efficiency of lysine utilisation by growing pigs.
(2005) Theeruth, Bianca Karen.; Gous, Robert Mervyn.
Two experiments were conducted for this thesis, to determine whether an animal should be fed to its genetic potential in spite of this not being achievable due to an on-farm constraint. The first experiment was designed to compare the response of pigs housed either individually or in groups to a range of feeds limiting in lysine between 40 and 85 kg live weight. Two hundred and eighty-eight entire male Large White x Landrace pigs were used. The experiment was divided into two growth periods, i.e. from 40 to 60 kg and from 60 to 85 kg. In each period, pigs were subjected to feed containing one of four dietary lysine concentrations. In Period 1, the lysine concentrations were 11.03 (L1); 9.54 (L2); 8.00 (L3) and 6.51 (L4) g/kg, while in Period 2 these were 7.82 (T1); 6.71 (T2); 5.55 (T3) and 4.40 (T4) g/kg. Pigs fed an L1, L2, L3 or L4 diet in Period 1 were fed a T1, T2, T3 and T4 diet in Period 2, respectively. Three buildings provided the following group sizes and floor-space allowances: House 1 contained eight pigs per pen at 1.94 m2/pig; House 2 contained four or eight pigs per pen at 1.72 or 0.86 m2/pig; and House 3 contained one pig per pen at 1.72 m2/pig. The individually-housed pigs were divided into three feeding levels, i.e. ad libitum, or pair-fed so that feed intakes would match those of ad libitum-fed pigs housed in groups of either 4 (restricted-4) or 8 (restricted-8) pigs per pen in House 2. For all group sizes, feed intake increased linearly as the dietary lysine content increased. However, this increase was significantly lower for 8, when compared with 1 and 4 pigs per pen. The linear increase in feed conversion efficiency with dietary lysine content was similar for all group sizes. However, at any dietary lysine concentration, pigs housed in groups of 8 had significantly higher efficiencies than the pigs housed individually or in groups of 4. Average daily gain increased linearly as lysine intake increased, this increase being the same for all group sizes. However, pigs in smaller groups grew significantly faster than those in larger group sizes for any lysine intake. Protein and lysine retention were unaffected by group size, increasing linearly as lysine intake increased. The efficiency of lysine utilisation (0.45) was not impaired by group size. The pair-fed pigs housed individually (restricted-4 and -8) consumed significantly less feed than the individually-housed pigs fed ad libitum, and this was reflected in their average daily gains, which increased linearly as lysine intake increased, but with the restricted-8 growing significantly slower than the ad libitum or restricted-4 pigs. In all three treatments feed conversion efficiency increased linearly with dietary lysine content, although the restricted-4 and -8 had significantly higher efficiencies than the ad libitum-fed pigs at any dietary lysine content. Protein and lysine retentions were unaffected by feeding level and increased significantly with lysine intake. However, at any lysine intake the restricted-8 pigs had a significantly lower efficiency of lysine utilisation than the ad libitum or restricted-4 pigs. The pigs with floor-space allowances of 0.86 and 1.94 m2/pig consumed significantly less and grew slower than the pigs with floor-space allowances of 1.72 m2/pig at any dietary lysine content. Feed conversion efficiency was unaffected by floor-space allowance and increased significantly with dietary lysine content. Similarly, protein and lysine retentions were unaffected by floor-space allowance and increased linearly as lysine intake increased. The efficiency of lysine utilisation (0.45) remained unaffected by floorspace allowance. It was concluded that when animals are socially stressed, feeding according to the requirement for maximum protein growth produces the best biological performance and carcass composition, with the corollary that, if profitability and biological efficiency is to be maximised, pigs housed in stressful conditions, or those whose future performance is predicted to be below potential because of external stressors, should not be given feed of an inferior quality. The second experiment was designed to determine the extent to which grouping or floorspace allowance would alter the nutrient content of feed chosen by pigs given a choice of two feeds differing in protein: energy ratio between 40 to 85 kg live weight. Three hundred and eighteen entire male Large White x Landrace pigs were used. Two buildings provided the following group sizes and floor-space allowances: House 1 contained nine and eighteen pigs per pen at 1.72 or 0.86 m2/pig; House 2 contained four, nine and fourteen pigs per pen at 1.72; 0.86 or 0.49 m2/pig. Animals were given simultaneous ad libitum access to a high (236 g protein/kg as fed) and a low crude protein feed (115 g protein/kg as fed) in two hardened plastic self-feeder bins placed side-by-side. A training period of six days was used prior to the start of the trial, during which the two feeds were alternated daily. The reduction in the proportion of high protein feed chosen over time was significantly higher for the groups of four and eight, in comparison to the groups of nine and eighteen, contrasting with the steady increase for the groups of fourteen pigs. Similarly, the significant increase for pigs with floor-space allowances of 0.49 m2/pig differed from the significant decrease for pigs with floor-space allowances of 0.86 and 1.72m2/pig. Pigs housed in larger group sizes and smaller floor-space allowances consumed significantly less and grew slower than pigs housed in smaller group sizes and larger floorspace allowances. However, the feed conversion efficiency remained unaffected by group size and floor-space allowance. The non-significant effect on protein retention with increasing group size contrasted with the significant increase associated with increasing floor-space allowance. The results of the two studies were compared to determine whether pigs chose differently depending on the degree of stress and the implication of this choice. Average daily gain was significantly reduced as the group size increased for pigs fed a fixed lysine content and choice-fed. However, this reduction was less severe with choice-feeding than when feeding a fixed lysine content. Increasing the group size significantly reduced the feed intake in pigs fed a fixed lysine content only. The efficiency of protein utilisation remained unaffected as the group size increased for the pigs fed a fixed lysine content. However, at any group size pigs fed lower lysine contents had higher efficiencies than pigs fed higher lysine contents. On the contrary, increasing the group size significantly increased the efficiency of protein utilisation in choice-fed pigs. The average daily gain and feed intake was significantly improved as the floor-space allowance increased but was similar for pigs fed a fixed lysine content and choice-fed. Although the efficiency of protein utilisation remained unaffected by increasing the floor-space allowance for the pigs fed a fixed lysine content and pair-fed, at any floor-space allowance pigs fed higher lysine contents had higher efficiencies than pigs fed lower lysine contents. The results indicate that providing socially stressed pigs a choice between an appropriate pair of feeds differing in protein: energy ratio, does not overcome the reduction in potential growth, but does result in performance similar to that of pigs fed a fixed lysine content. It was concluded that the social stress of grouping or floor-space allowance has no influence on the ability of the animal to select an appropriate dietary combination allowing the expression of potential growth within the constraint(s) of the production system.
Meeting the amino acid requirements of growing pigs by manipulating the feeding schedule.
(2006) Butt, Tracy Susan.; Gous, Robert Mervyn.
Three experiments were designed to find the most efficient and cost-effective method of meeting the changing amino acid requirements of male and female pigs during the growing period, using the minimum number of feeds. Trial one involved 144, and trial two 192 commercial crossbred (Landrace x Large White) pigs, eight to a pen, with sexes separate. Trial three involved 24 commercial crossbred (Landrace x Large White) pigs and 24 Dalland pigs each penned separately. The amino acid requirements (g/d) for the pigs in all three trials were determined for male and female Landrace x Large White pigs, respectively, using the Pig Growth Model (EFO Software Natal, 1995). Parameter values used for males and females were: growth rate (B, Id) 0.0107 and 0.0120; protein at maturity (Pmat, kg) 39.0 and 28.0; and lipid at maturity (Lpmat, kg) 2.60 and 3.89 respectively. In trials 1 and 2 two iso-energetic (DE 13.8 MJ/kg) basal feeds were formulated; Basal A being a high crude protein (CP) (347g CP/kg) feed designed to meet the amino acid requirements of a male at 20 kg liveweight, while Basal B was a low protein feed (l34g CP/kg) designed to meet the amino acid requirements of a female at 88 kg, thus providing for the most- and the least-demanding pigs on the trial. In the third trial, two iso-energetic (DE 13.8 MJ/kg) basal feeds were again formulated; Basal A being a high crude protein (CP) (347g CP/kg) feed designed to be 20% higher than the amino acid requirements of a male at 20 kg liveweight, while Basal B was a low protein feed (l34g CP/kg) designed to be 20% lower than the amino acid requirements of a female at 88 kg, once again providing for the most- and the least-demanding pigs on the trial. Trials 1 and 2 began when the median weight of pigs in each pen reached 20kg, and were terminated at a pen median of 85 kg liveweight. In the third trial each pig was started on trial when it reached 20kg and was terminated at a weight of 85kg. The first trial involved a phase feeding schedule (20-40, 40-60 and 60-85kg liveweight). The two basal feeds were blended in different proportions to create three feeds per phase: lysine contents in each of the phases in Treatment 1 (TI) were: 11, 8.68 and 7.26g/kg; in T2 they were 9.93, 7.58 and 6.24g/kg; and in T3, 8.85, 6.48 and 5.22g/kg. From the analysis it was established that ADO and time to reach 85kg were the only variables to show significance. ADO exhibited a significant sex x treatment interaction. There were significant differences between treatments for time taken to reach slaughter weight. In addition to a treatment effect there was a sex x treatment interaction for time to slaughter weight. It was expected that males on Tl and females on T3 would exhibit the most efficient performance for their respective sex since these treatments were specifically formulated to meet their requirements. Midway through the trial the pigs contracted enteritis, this affecting the outcome of the trial by inhibiting the potential growth of the pigs. The results of the trial indicated that dietary protein level affected the time taken to reach slaughter weight. This led to the second trial where four treatments were applied. Three of the four treatments followed a fixed feeding schedule, making use of the two basal feeds and a 1: 1 blend of these. The fourth treatment followed a phase feeding schedule, differing between the males (20-65, 65-75 and 75-85 kg liveweight) and the females (20-35, 35-75 and 75-85 kg liveweight). This treatment also made use of the two basal feeds and a 1: 1 blend of these. From the analysis it was found that there were no significant effects of sex and no interactions between feeding treatments and sex; however, ADO, FI, FCE, back fat thickness, time taken to reach 85kg and cost/kg gain were all significantly affected by the feeding treatments. Carcass lean, carcass lipid and total body lipid were also significantly affected by the feeding treatment. This trial was conducted to determine the extent to which differences in growth rate, food intake and carcass lipid could be altered by dietary means. The effect of the level of feed protein was once again shown to be of importance when feeding growing pigs. The third trial was designed to test the efficiency with which two strains make use of the dietary protein supplied. Three treatments were applied: Tl was a choice-feeding treatment in which the pigs were offered the two basal feeds simultaneously. T2 and T3 followed a phase feeding schedule (20-40, 40-60 and 60-85kg liveweight). The two basal feeds were blended in various proportions to create three feeds per phase: the lysine contents in each of the phases in T2 were: 12.2, 10.0 and 7.26g/kg; and in T3 8.1, 6.7 and 5.1g/kg. There were significant sex effects as well as strain x feeding treatment interactions. All variables, ADG, FI, FCE, time taken to reach 85kg and cost/kg gain, with the exception of back fat thickness, showed significance. It was expected that the Dalland strain would perform better than the Cross strain; however, this was not the case, indicating the need for further research into the possibility of feeding according to the genetic makeup of the animal. The importance of meeting the amino acid requirements of the growing pig was evident when summarising the results of the three trials reported here.
Response of broiler chickens to dietary lysine, methionine and metabolisable energy concentrations.
(1981) Maclachlan, Rais Guthrie.; Stielau, Werner Johannes.; Gous, Robert Mervyn.
No abstract available.

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