Maximum Average Daily Gain Research Articles

Determination of the optimum dietary lysine concentration for growing pigs housed in pairs and in groups

AbstractThree 28-day trials were carried out to determine the optimum dietary lysine concentration for growing pigs between 20 and 68 kg. There were 96 pairs of pigs in experiment 1 (20 to 41 kg), 72 pairs in experiment 2 (40 to 68 kg) and 42 groups (14 per group) in exp. 3 (40 to 62 kg). All experiments were arranged as randomized complete block designs, blocked on the basis of sex and start weight. Treatments consisted of isoenergetic (13·8 MJ digestible energy per kg) diets with increasing lysine concentrations. Dietary lysine concentrations were 9·7, 10·7, 11·6, 12·5, 13·5 and 14·4 g/kg (experiment 1) and 9·0, 9·9, 11·0, 12·1, 13·1 and 14·1 g/kg (experiments 2 and 3). Response curves were fitted to the data to determine the optimum dietary lysine concentration for maximum average daily gain (ADG) and minimum food conversion ratio (FCR). In experiment 1, ADG and FCR responded quadratically to dietary lysine content (P < 0·01 and P < 0·05). Male pigs had better FCR and lysine conversion ratio (LCR) than female pigs (P < 0·05). In experiment 2, there was a quadratic effect of increasing dietary lysine concentration on FCR (P < 0·05). Male pigs had lower daily food intake (DFI, P < 0·01) and daily lysine intake (DLYIN, P < 0·01) and had better FCR (P < 0·01) and LCR (P < 0·01) than female pigs. In experiment 3, there was a quadratic effect of increasing lysine concentration on FCR (P < 0·05). Male pigs had better FCR and LCR (P < 0·05) than female pigs. In all experiments, increasing dietary lysine concentration resulted in an increase in DLYIN and a deterioration in LCR (all linear, P < 0·001). Regression analysis predicted optimum dietary lysine concentrations for maximum ADG at 13·1 and 12·7 g lysine per kg in experiments 1 and 2, and minimum FCR at lysine concentrations of 14·6, 12·2 and 12·7 g/kg for experiments 1, 2 and 3 respectively. In conclusion, the optimum dietary lysine concentration for maximum ADG and minimum FCR could be predicted using quadratic models and although males had better FCR than females, optimum dietary lysine concentrations were similar for both sexes.

Evaluation of alternative nonlinear mixed effects models of duck growth

Two nonlinear growth functions were evaluated on 6 groups of 32 ducks. Ducks were randomly assigned to 1 of 6 dietary treatments and weighed weekly from 1 to 43 d of age. The Weibull function had the form: BW(it) = A - (A - B) exp - [(C - 1)/C] (t/IP)**C, where BW(it) is the BW of the ith duck at age t in days and A, B, C, and IP are fixed parameters. The variable A represents mature BW and the variable IP is the age (inflection point) at which maximum average daily gain is achieved. The addition of a single random effect to the Weibull growth function (ip), in which the age to reach the BW at the overall population inflection point of each duck varies, provided a substantially better fit than any other alternative fixed or mixed models. Overall, the Weibull function under-predicted the d-1 BW (46.7 vs. 55.1 g, P < 0.05) and over-predicted the d-8 BW (233.6 vs. 211.7 g, P < 0.05). The predicted BW from d 15 to 43 was very close to the actual mean BW at each age. This model predicts that the between-duck variance in BW increases with age and that the CV increases from 1 to 8 d of age, reaches a plateau from 15 to 22 d of age, and then slowly declines. This mixed effects model predicts the mean age and approximate variation in age that ducks require to reach a specific BW, and is easily adaptable to stochastic modeling.

Effects of nitrogen and sulphur fertilization on oats yield, quality and digestibility and nitrogen and sulphur metabolism of sheep in the Inner Mongolia Steppes of China

The influence of nitrogen (N) and sulphur (S) fertilizer on yield and quality of spring oats and the N and S metabolism of sheep was determined. Eighteen crossbred wether lambs (about 30 kg) were fed oats fertilized with N (0, 138 kg N/ha as of urea) and S (0, 30 and 60 kg S/ha as gypsum) assigned randomly to six treatments in an experiment of 2×3 factorial design. On S-deficient soils, S and N fertilization increased dry matter (DM) by 10.5 and 71.9%, and crude protein (CP) yield of oats by 11–13 and 94.5%, but there was no interaction between N and S fertilizer. S fertilization increased S content of oats from 0.14 to 0.29% and significantly reduced the N:S ratio from 14.4 to 7.22. There was a significant interaction between N and S on N content. N and S fertilization significantly increased apparent DM digestibility of oats by about 4%, but did not affect intake (g/kg BW0.75), DM intake being almost 60 g/kg BW0.75 for all treatments. N increased average daily gain of lambs by 62.4–78.6% if S was supplied, being twice the gain without S supply but no interaction between N and S was observed. N retention was affected by interaction between N and S fertilization. N retention and N utilization were positively correlated with S intake. N:S ratio in oats was positively correlated with N metabolism. S fertilization increased N utilization efficiency and vice versa. The critical levels of total S in oats were 0.20 and 0.23%, and the critical levels of N:S ratio were 17.0 and 15.7 for maximum DM and CP yield, respectively. The critical levels of S content and N:S ratio for maximum average daily gain of lambs were 0.26% and 10.5, respectively. Therefore, in the diagnosis of S status in soil–forage–animal systems, the use of total S and N:S ratio in the forage tops for the maximum CP yield is preferable to that for the maximum DM yield because the values are more closely related to the requirements for maximum daily gain of lambs; similarly, the use of a combination of total S and N:S ratio is preferable to the use of N:S ratio alone.

Optimal heifer management decisions and the influence of price and production variables

A dynamic programming model was developed to optimize the rearing strategy of individual heifers. The model optimized management decisions with respect to growth rate, insemination and replacement by maximizing the present value of net returns per heifer place. Faced with the scarcity of exact information on the fundamental elements of heifer rearing, sensitivity analyses were carried out to evaluate the technical and economic consequences of various price and production variables. Results for Dutch conditions showed that it was most profitable to rear heifers at the highest achievable growth rates without fattening. Based on a critical prepubertal average daily gain (ADG) of 900 g/day and a maximum achievable postpubertal ADG of 700 g/day, optimum policy resulted in an average age of first calving of 21.2 months at a body weight of 541 kg. The sensitivity analyses demonstrated a considerable impact of the critical prepubertal growth rate on both the optimal rearing policy and expected net returns. Technical and economical results were also very sensitive to seasonal influences on price and production variables. Heifer calves born in winter were the most profitable calves to rear.

The influence of heat production on voluntary food intake in growing pigs given protein-deficient diets

AbstractNinety-six entire male Large White XLandrace pigs were assigned at 13 kg to one of six dietary crude protein (P) treatments (230 g/kg (P1), 201 g/kg (P2), 178 g/kg (P3), 151 g/kg (P4), 125 g/kg (P5), 93 g/kg (P6)) and one of four temperatures (T) (no. = 4) (18°C, 22°C, 26°C, 30°C), and were given food ad libitum until slaughter weight of 30 kg. At all temperatures gut fill was a constant proportion of food intake (Fl) (1·56) but this ratio varied with different protein concentrations. Food intake increased with decreasing temperature and with decreasing protein content to a maximum rate on P4 (1·347 kg) whereafter FI declined. There was a linear decrease in average daily gain (ADG) with decreasing protein content while temperature had a significant curvilinear effect on ADG and food conversion ratio (FCR) with maximum ADG (0·680 kg/day) at 26°C. Body protein content decreased as the dietary protein concentration declined below P3 and there was a corresponding increase in lipid content. Temperature had no effect on body protein content but had a significant effect on lipid content. Similar trends occurred in the rate of protein (PR) and lipid (LR) retention with maximum PR (117·1 g/day) attained on PI, P2 and P3. Protein and temperature had a significant effect on total heat loss (THL). Maximum THL occurred in the protein treatment that resulted in pigs consuming maximum FI. The efficiency of protein utilization increased with increasing temperature but the response was dependent on the protein supply. It is concluded that on low protein diets pigs increase their Fl to maintain potential protein growth until a point is reached where the animal can no longer compensate and FI will decline. The extent of the compensation will depend on the amount of heat the animal can lose which in turn is dependent on the environmental temperature.

Forage Characteristics Limiting Animal Performance on Warm‐season Perennial Grasses1

AbstractChemical and in vitro characteristics of six perennial summer grasses {common, ‘Coastal’ and ‘Coastcross‐1’ bermudagrasses [Cynodon dactylon (L.) Pers.]; ‘Pensacola’ bahiagrass [Paspalum notatum Flugge]; common weeping lovegrass [Eragrostis curvula (Schrad.) Nees.]; and ‘Kleingrass 75’ [Panicum coloratum L.]} were determined to identify factors limiting the performance of grazing animals. In vitro dry‐matter digestibility (IVDMD), cell wall content (CWC), acid‐detergent fiber (ADF), acid‐detergent lignin (ADL), silica, and in vitro cell‐wall digestibility (IVCWD) were determined for samples of available forage taken at 14‐day intervals. Animal performance was obtained from yearling heifers grazing established stands of each grass. Available forage was estimated from strips harvested from each pasture at 2‐ to 4‐week intervals. Animal performance was significantly correlated (r = 0.85**) with available forage when dry‐matter digestibility was relatively uniform. As IVDMD of available forage decreased, more available forage was required to reach maximum average daily gain (ADG). Also, as IVDMD decreased, maximum ADG decreased. The CWC of the grasses ranged from 45 to 82% with cell wall digestibility ranging from 82 to 36%, respectively. CWC and IVDMD were significantly correlated with animal performance (r = —0.80**, and 0.78**, respectively). Cell wall digestibility calculated from Van Soest's “summative equation” significantly over‐estimated IVCWD. Lignification was one factor limiting cell wall digestibility (r = —0.76**) and in Coastcross‐1 bermudagrass and Pensacola bahiagrass silica was as important as lignin. CWC and IVCWD could be used to accurately predict IVDMD in Kleingrass 75 (r = —0.96** and 0.95** respectively). High lignin and/or silica content of available forage was associated with poor animal perfortnance on all grasses.