Protein Deposition in Growing and Finishing Pigs

Transcription

1 1 Protein Deposition in Growing and Finishing Pigs DETERMINING WHOLE BODY PROTEIN DEPOSITION RATES IN PIGS. Mark L. Lorschy, Doug A. Gillis, John F. Patience and Kees de Lange. Summary There is controversy as to how the rate of protein deposition changes as pigs are grown to market and whether this pattern and the rates of protein deposition are different for barrows and gilts. The rate of protein deposition is the major determinate for essential amino acid requirements. To define requirements for lysine and other essential amino acids, it is extremely important that the protein deposition rates are defined for a particular strain of pig, both barrows and gilts. Fifty-six pigs were involved in a carcass slaughter trial to characterise the changes in carcass composition (i.e water, dry matter, protein, lipid and ash content) of both barrows and gilts of a defined genotype grown from 24 to 120 kg liveweight. Estimates of protein and lipid deposition rates were derived for pigs at 24, 56, 72, 88 to 104 and 120 kg liveweight. Protein deposition peaked for barrows between 56 and 72 kg liveweight at about 137 g/d, and for gilts between 88 and 120 kg liveweight at about 137 g/d. The results indicate that there are marked differences in protein deposition rates at different liveweights between genders. Introduction Pigs that have been intensively selected for body gain or lean tissue deposition have a higher maximum protein retention than pigs of unimproved strains. Defining the amino acid requirements for these improved strains requires accurate estimates of whole body protein deposition potentials from birth to market weight. Protein deposition curves have been developed for several commercially available genotypes: the major differences between genotypes are the overall mean protein deposition rate and the rate in which protein deposition declines after 90 kg live weight. The maximal protein deposition determine the pig's nutrient requirements for growth, composition of growth, and response to nutrition or management changes. The objective of this paper were to: (i) characterise the upper limit to protein deposition; and, (ii) characterise growth curves for empty carcass dry matter, lipid and ash. Experimental Procedure All animals were PIC Camborough 15 gilts X Canabrid F1 hybrids. At weaning (~5 kg), the pigs were given ad libitum access to a commercial starter containing 1.5% available lysine. At about 18 kg, 29 gilts and 29 barrows were selected for the experiment on the basis of liveweight Pigs were given ad libitum access to a grower diet to 65 kg, and a finisher diet from 65 to 120 kg (Table 1). These diets contained essential amino acids and energy at levels deemed as to not limit lean tissue growth. At 24, 56, 72, 88, 104 and 120 kg liveweight, 5 barrows and 5 gilts were selected for slaughter, the exception being at 24 kg when only 4 pigs of each gender were slaughtered. Individual liveweight and feed disappearance data (to 100 g) were recorded weekly. When each pig reached its target slaughter weight, the pig and feed were weighed, the pig was euthanased and contents of the stomach, small and large intestines, gall bladder and urinary bladder removed. Empty carcass weight was defined as the weight of the carcass after gut contents were removed. The frozen carcasses were then ground in a meat grinder to ensure that the whole carcass was mixed thoroughly. Sub-samples of carcass were freeze-dried to estimate moisture content, after which each freeze-dried sample

2 2 was analysed for nitrogen (N), ether extract, ash and moisture. Prediction equations for each gender were derived for feed to gain ratio, rates of liveweight gain, feed intake, deposition of carcass dry matter, crude protein (N x 6.25), lipid and ash to obtain rate estimates at 24, 56, 72, 88, 104 and 120 kg liveweight. These measurements were analysed by the general linear model (SAS, 1991) with slaughter liveweight group, gender and their interaction as effects. Means for variables within a slaughter liveweight group between genders and within a gender between slaughter liveweight group were tested using the t-test. Results and Discussion Table 2 shows that the pattern of growth of empty carcass weight, dry matter, crude protein, lipid and ash were quite different for gilts and barrows. Appetites of the barrows from 24 to 65 kg, and 65 to 120 kg was equivalent to 93 and 100% of the predicted by the National Research Council (1987). Similarly, gilts consumed 87 and 91% of that predicted by the National Research Council (1987) during growth from 24 to 65 kg and 65 to 120 kg, respectively (see Figure 1). For gilts, the rate of gain for carcass weight, dry matter, lipid and ash continued to increase towards 120 kg liveweight, whereas protein deposition rate reached a maximum at 104 kg liveweight. For barrows, maximum rates of empty carcass weight, dry matter, crude protein, and ash occurred before 120 kg liveweight. Maximum empty carcass weight and dry matter gain occurred at 72 kg liveweight, whereas maximum gain of protein and ash occurred between 56 and 72 kg liveweight and for lipid at 104 kg liveweight. Average daily gain from 24 to 120 kg mimics the response of protein deposition. Protein deposition peaked in barrows at 138 g/d at 56 kg liveweight, and in gilts at 141 g/d 120 kg liveweight (Figure 2). It is suggested that the observed decline in protein deposition in barrows after 56 kg liveweight was due to the consistently greater partition of energy to lipid (Figure 3). A greater rate of lipid to protein deposition was confirmed by the greater feed to gain ratio in barrows growing towards 120 kg. The changes in protein deposition with growth observed in the current study for barrows and gilts are similar to those recently reported at Purdue University for a range of strains of pig differing in potential for fat-free lean gain from 260 to 360 g/d. These results reinforce the need for split sex and multiply phase feeding systems for pigs grown to market. As a consequence of the different patterns and rates of protein and lipid deposition for gilts and barrows, different nutritional recommendations particularly for essential amino acids and energy, are necessary to minimise feed costs and minimise excess carcass lipid deposition. This study has provided information concerning how protein deposition changes as pigs grow. As protein deposition is the major determinate of the essential amino acid requirement, recommendations for these amino acids may be made to meet these levels of protein deposition. Acknowledgment This authors wish to acknowledge the funding for this project was provided by the Archer Daniels Midland Corporation who also kindly provided crystalline amino acids and amino acid analysis for the project.

3 3 Table 1 Experimental growing and finishing diets (as fed, %). Item Grower Finisher Ingredient Barley Wheat Soybean Meal - 47% Select Menhaden Fishmeal Whey Powder L-Lysine HCl DL-Methionine L-Tryptophan L-Threonine Dicalcium Phosphate Limestone Salt Mineral Premix A Vitamin Premix B Canola Oil Calculated analysis Digestible Energy, kcal/kg Crude Protein, % Available Lysine, % Available Total Sulfur Amino Acids, % Available Threonine, % Available Tryptophan, % Calcium, % Phosphorus, % Sodium, % a Provided the following per kg of premix: vitamin A, 650,000 IU, vitamin D 165,000 IU, vitamin E 8,000 IU, menadione 800 mg, thiamine 200 mg, riboflavin 1,000 mg, niacin 7,000 mg, d-pantothenic acid 3,000 mg, vitamin B12 5 mg, biotin 40 mg and folic acid 400 mg. b Provided the following per kg of premix: copper 10 g, iron 16 g, manganese 5 g, zinc 20 g, iodine 100 mg, selenium 20 mg.

4 4 Table 1 Feed to gain ratio, rates of feed intake and gain for empty carcass weight, dry matter, crude protein, lipid and ash for gilts and barrows at six consecutive liveweights between 24 and 120 kg. Variable Gender average daily gain (g/d) gilt 709 aa 899 ba 948 ba 965 ba 952 ba 909 ba barrow 695 aa 1001 ba 1039 ba 1001 ba 886 ba 694 ab average daily feed intake (g/d) gilt 1113 aa 2025 aa 2514 aa 2571 aa 3005 aa 3422 aa barrow 1126 aa 2049 bb 2825 bb 3128 cb 3203 cb 3526 cb feed to gain ratio (g/kg) gilt 1.49 aa 2.24 ba 2.61 ca 2.99 ca 3.36 da 3.73 da barrow 1.19 ab 2.23 ba 2.75 ca 3.27 db 3.79 db 4.31 eb empty carcass weight (g/d) gilt 514 aa 798 ba 908 ca 979 da 1032 ea 1068 fa barrow 676 ab 924 bb 974 cb 982 da 948 eb 860 fb dry matter (g/d) gilt 225 aa 376 ba 481 ca 508 da 578 ea 603 fa barrow 315 ab 503 bb 543 cb 567 db 540 eb 504 fb crude protein (g/d) gilt 90 aa 119 ba 131 ca 136 ca 138 ca 138 ca barrow 119 ab 139 bb 136 ba 123 ab 113 ab 91 cb lipid (g/d) gilt 97 aa 210 ba 308 ca 327 ca 400 da 444 ea barrow 137 ab 304 bb 362 cb 415 db 425 da 404 db ash (g/d) gilt 13 aa 20 ba 25 ca 25 ca 30 da 31 da barrow 26 ab 29 ab 26 aa 26 aa 19 db 14 eb lipid /protein deposition gilt 1.06 aa 1.77 ba 2.35 ca 2.41 ca 2.91 da 3.31 da barrow 1.15 aa 2.20 ab 2.67 aa 3.38 bb 3.81 bb 4.55 cb a,b,c A,B,C Differences (P<0.05) between means within a gender between liveweight groups given by a different lower case letter; Differences (P<0.05) between means between genders within liveweight groups given by a different upper case letter.

5 Average daily feed intake (g/d) Barrows 3500 Gilts % NRC Figure 1 Average daily feed intake of gilts and barrows with respect to that predicted by the National Research Council (1987) grown between 24 and 120 kg. 160 gilts barrows Crude protein accretion (g/d) Figure 2 Average crude protein deposition rates (g/d) predicted for barrows and gilts at 24, 56, 72, 88, 104 and 120 kg liveweight.

6 6 5 gilts barrows 4 Lipid/Protein accretion Figure 3 Ratio between lipid and crude protein deposition predicted for barrows and gilts 24, 56, 72, 88, 104 and 120 kg liveweight.