CARCASS-QUALITY IN BACON PIGS.

New Zealand Journal of Agriculture, Volume 54, Issue 4, 20 April 1937, Page 223

CARCASS-QUALITY IN BACON PIGS.

C. P. McMeekan,

Massey Agricultural College, Palmerston North

PART lI.—THE INFLUENCE OF SUPPLEMENTARY CONCENTRATES ON CARCASS-QUALITY. Both in New Zealand and in the United Kingdom critics of the New Zealand methods of raising and fattening pigs practically exclusively on dairy by-productsseparated milk, buttermilk, and wheyhave frequently expressed the opinion that this method of feeding injuriously affects the quality of the bacon produced from such pigs. Their opinion is undoubtedly influenced by practices that prevail in European countries, and that are not necessarily applicable under New Zealand conditions. In particular, it has been suggested that the feeding of large volumes of separated milk, causes thin bellies, and gives rise to the condition described by the trade as “ paper flanks.” Accordingly a series of experiments was designed to investigate thoroughly these assertions by comparing the quality of carcasses of pigs fattened exclusively on factory . buttermilk with those of others fattened on varying quantities of. concentrate meals in addition to buttermilk.

Experimental Technique.

Three series of group-feeding trials involving 106 Tamworth-Berkshire cross pigs, were conducted over a period of three years. Detailed description of the technique, feeding, and economy aspects of these trials have already been reported in this journal(g).

Briefly, the appetite of the pigs governed the quantity of buttermilk fed to all groups. With the supplemented groups a grain-meal mixture was fed on a per 100 lb. live-weight per day basis, the actual quantity varying between the different groups. Thus in Series A and B the control group received buttermilk only, and the respective supplemented groups an addition to the daily ration of from | lb. to 2 lb. of meal per 100 lb. live-weight. In each case in these series, supplementing extended over the whole fattening-period. (Table VII.) On the other hand, Series C was designed to fill in the experimental gaps in A and B by studying in particular the stage of growth at which at all— is beneficial from both the quality and economy viewpoints to supplement buttermilk with concentrate feeds. Accordingly, meal was fed with buttermilk at varying rates and over different growth stages during the fattening-period, which extended from weaning to bacon weights. Thus meal was fed during the early stages from weaning to pork weights, during the late stages from pork to bacon weights, throughout the whole fattening-period, and at a heavier rate during the early stage than during the late. The pigs received buttermilk only during the non-supplemented stages. (See Table VII and Reference 9.) All pigs were slaughtered as they reached 200 lb. live-weight, and were handled at and after slaughter as described in Part I of this paper, being shipped to London for examination after examination as carcasses at the New Zealand end. For special reasons a few carcasses were not exported, but the data relating to these was recorded in New Zealand. The results reported are based largely upon the measurements taken by and the opinions of the New Zealand Pig Carcass Evaluation Committee, and the author takes this opportunity of thanking Messrs. H. R. Davidson, John Hammond, J. B. Swain, and N. L. Wright for their careful and detailed work. Influence of Diet on .Thickness and Quality of Streak and Thickness of Bellies. Data based upon actual measurements only are reported, partly for reasons of space and partly because effects were noticeable only in respect to “ internal ” quality characters. A convenient summary of the group results is obtained by examining the average value obtained for each character, expressed on a percentage basis, the standard of comparison being that of the Committee(l). The general picture presented by these results (Table VII) clearly indicates that the addition of concentrate supplements to the buttermilk ration produced no measureable improvement, in the bellies of bacon pigs. Within Series A and B, where the quality of the streak was assessed by measurement on the loin-cut (at last rib) the respective groups are equally efficient. In Series C where evaluation was made by comparison with standard photographs, the efficiency differences existing are in favour of the groups receiving little or no meal.

From the quality angle the belly region should not only be thick but should also contain a high proportion of lean meat. Since the latter is not shown up by a thickness measurement, the method of evaluation by standard photographs is considered the more satisfactory index of belly or streak quality(i). Detailed results by both methods are set out in Table VIII, which also shows the thickness of bellies measured on the uncut carcass as in commercial grading practice.

The average measurements both on the loin-cut and on the uncut carcass clearly illustrate the failure to influence the thickness of the streak by increasing the dry-matter content of the ration., even though the rate of supplementing was raised as high as 4 lb. of meal per pig daily during the later stages of fattening in Group 3 (Series A). Factory buttermilk as a sole source of diet not only produced bellies as thick as those from pigs receiving more concentrated diets, but the results recorded reach a high standard of efficiency. The results throw considerable doubt on the theory that bulky diets are necessarily associated with thin bellies. With types of pigs similar to those used in these experiments, the author has not obtained significantly thicker bellies • from pigs fattened on a completely meal diet.* Neither rate of supplementing nor stage of growth of supplementing produced any effect on measurements. On the other hand, though the results are not strictly uniform, the evaluation of streak on a basis of the proportion of fat to lean as well as on thickness (Marks 2, Table VIII) suggests that the use of meal * Unpublished data.

has tended to increase the proportion of fat in the belly region. See also Plate 11. This effect is in keeping with the increase in proportion of fat as measured in other parts of the carcass. The thickness results are in agreement with recent work in England(io), where reduction in the water content of the ration failed to effect any significant improvement in bellies. In view of further work(n) which substantiates the practical farmers’, belief that a fasting-period before slaughter improves the belly thickness, it must be noted that the pigs in these series were killed after a uniform fasting-period of twelve to sixteen hours. Incidentally the latter offers a more practical method of improving- belly thickness by ensuring such a fasting-period than does the provision of special rations. Further, as pointed out in Part I of this paper, the slaughter of pigs at carcass weights of 140 lb. and over rather than at lighter weights can be of material assistance in avoiding excessively thin bellies. If thinness of belly is associated with belly distension resulting from bulky diets, it is suggested .-•that the negative results from these investigations, are due to the fact that the use of supplements even at relatively high levels ■ does not materially reduce the appetite of pigs for milk. This is a regular feature in New Zealand experience. Influence of Diet on Proportion of Fat to Lean in Different Parts of the Carcass. The use of meal with buttermilk increased the proportion of fat in the carcass, and the higher the proportion of meal fed the greater was the deposition of fat. This effect is clear from the efficiency awards summarized in Table VII. Details of group fat-measurements in the loin-cut are set out in Table IX.

The extent of the increase in fat measurements was not great, but so undesirable is even a slight excess of fat in the commercial bacon carcass that the small increase recorded in the heavy-meal-fed groups was sufficient to produce significantly lower efficiency awards from the Committee. The uniformity of the effect may be judged from the photograph of the loin-cuts of the series showing the greatest effect.

Within each series the heaviest supplemented groups had a higher proportion of fat as indicated. by the measurements on the loin-cut than both the light supplemented groups and the buttermilk - only groups, with one exception. The somewhat anomalous result of Goup i of Series C, the fat measurements of which are not in agreement with the tendency of the figures of the comparable groups of the series, mor with the results of the other two series, is rather difficult in interpret. Two points may be noted. A greater individuality effect was recorded in the pigs of each group of Series C than was the case with Series A and B, where the results were more uniform. This was specially marked in Group i, and suggests that a more sensitive technique than the group-feeding system may be necessary to provide a conclusive finding on the point at issue. ' Further, on theoretical grounds, and on the basis of a certain amount of evidence on the point (7, 12), the higher fat measurements of Group 1 might be attributed in part at least to a possible effect of very slow rate of fattening in the early stages, and rapid growth in the later stages (9) upon deposition of fat in the carcass — accelerated weightincrease resulting from unlimited feeding in the final stages, following a long period of slow growth, might be mostly fat.

The results from Series C do not show any advantage from supplementing at any particular stage of growth, but rather indicate that the important factor so far as fat is concerned is the quantity of meal fed. Proportion of fat was also assessed by fat measurements along the back-line at the thickest point of the shoulder and the thinnest point over the loin. The carcasses were graded on a basis of these measurements according to the New Zealand official grading-scheme.

These results are in agreement with those taken on the loin-cut, a greater thickness of back-fat being associated with heavy rates of mealsupplementing, and the best measurements being shown by the pigs fed buttermilk alone. Little variation in fat over the loin existed. The variations in shoulder fat were responsible for a higher proportion of first-grade carcasses from groups fed buttermilk alone or supplemented at the lower rates. It is to be noted that the shoulder-fat measurements and grading results of Group I, Series C, bring this group more in line with the related results. In respect to this tendency for meal-supplementing to produce an increased proportion of fat in the carcass, several points of practical significance arise. The inherent tendency of New Zealand bacon pigs to carry too high a proportion of fat has been demonstrated in Part I. Any system of feeding which may accentuate this tendency is potentially dangerous on economic grounds. Yet other economic advantages of meal-feeding makes the limited use of supplements with by-products highly desirable. Rather than these investigations, therefore, suggesting the abandonment of a system of feeding with many husbandry and financial 9, 13), .they point to the necessity for improvement in the type of pig in New Zealand to one capable of producing carcasses with the correct proportion of fat at bacon weights.

In view of the findings of Hammond(2, 5,6, 12) on growth in,pigs, it is not surprising that by accelerating growth with the early-maturing types of pigs used in these experiments the additional energy supplied by the meal was deposited largely as fat. The greater proportion of fat in all groups of Series C as compared with those of A and B was undoubtedly due to the excessively short pork-type pigs used in the former. Finally, it is suggested that the results brought forward herein demonstrate clearly that the feeding of buttermilk improves the quality of bacon carcasses and that the excessive fat in New Zealand baconers is due more to the use of rapid-maturing pork-type strains than, as is commonly believed, to the feeding of pigs exclusively or almost exclusively upon dairy by-products. A Influence of Diet on Firmness of Fat. The quality of the fat as well as its quantity is a factor of considerable importance in the carcass-quality of bacon pigs. The fat should be as hard as possible because soft fat readily becomes rancid. A hard fat is particularly essential in carcasses which have to withstand the strain of long periods of freezing and storage (3) as do pigs from New Zealand destined for the United Kingdom market. The following table gives details of the iodine values obtained in England from the pigs of Series C.

* Composite group samples. These iodine values are in all cases markedly lower than those quoted elsewhere for pigs fattened in other countries. They show that buttermilk produces a firm fat, and that the firmness is not reduced when the milk is supplemented with meal up to 2 lb. per 100 lb. live-weight daily. They also clearly demonstrate that New Zealand pigs, have definite advantages for storage in case of necessity. Summary. Experiments carried out with over a hundred pigs divided into groups and fed, in addition to unlimited supplies of factory buttermilk, quantities of meal varying from nil to 2 lb. per 100 lb. live-weight daily, show that . < (a) The addition of meal to a buttermilk diet does not increase the thickness of belly : (&) There is no evidence that thinness'" of belly is attributable to feeding unlimited supplies of buttermilk :

(c) Buttermilk produces carcasses with a lesser proportion of fat than buttermilk supplemented with meal, but this feature is not marked when the meal fed does not exceed a rate of i lb. per too lb. live-weight daily : (d) The type of pig exerts a greater influence than the type of diet on the proportion of fat to lean in bacon carcasses : (g) The fat of pigs fed on buttermilk and buttermilk plus meals is particularly hard. Acknowledgments In a project of this magnitude it is impossible to acknowledge adequately all those who necessarily played an essential part in the work. Particular thanks are due to Mr. W. J. Croucher, Recording Officer, Manawatu-Oroua Pig Development and Recording Club, for most valuable and extensive assistance, mention of which was made in Part I, and to the members of the New Zealand Pig Carcass Evaluation Committee, Messrs. Hammond, Davidson, Swain, and Wright, for their invaluable co-operation and assistance at the London end. The work would also have been impossible without the active support of the following organizations : Kiwi Bacon Co., Longburn ; N.Z. Co-opera-tive Pig Marketing Association ; Cheltenham Dairy Co. ; H. R. Lane and Co.; Jos. B. Swain and Co.; Smithfield, Empire Bacon Co., Newcastle ; N.Z. Department of Scientific and Industrial Research. Special thanks are due to farmers who supplied pigs and necessary information, and to Mr. A. Webb, of the Kiwi Bacon Co., Mr. H. E. Thurston, of the Cheltenham Dairy Co., and to Professor W. Riddet, all of whom were of material assistance in planning and organizing the work. Special financial grants were made by the N.Z. Meat Producer’s Board and the Department of Scientific and Industrial Research to facilitate the investigations. Personal thanks are due to Professor W. Riddet for criticism and advice in the preparation of this report. References. (9) McMeekan : N.Z. Jour. Agr., Dec., 1936. (10) Annual Report West Scot. Agr. Coll. Pig Breeders Ann., 1936-37. (11) Callow, et al., Report Food Investigation Board, 1935. (12) Hammond. Unpublished data. (13) McMeekan and Croucher : N.Z. Jour. Agr., 53, 1, 1936.

Note. —Fat measurements taken on loin-cut at last rib, Series A and B at point of eye, and. Series Cat point i| in. in from middle line. Reference(i).

* Per 100 lb. weight-gain—dressed carcass. . f N.Z. Official standardsgrading on fat measurements only, taken on cold dressed carcass (N.Z.). .

— A. Series C. Group i. Group 3. 1. Group Group 3. Group Group Group Group 4. Group 5. Rate Nil lb. lb. Nil i lb. lb. i| Nil lb. i early, Nil live- 100 whole whole whole whole whole whole whole whole nil lb. lb. day per period period period period period period period ■ (1) late (3) late(3) used Meal lb. 140 lb. 260 lb. 130 200 lb. lb. lb. 40 lb. 85 gain Weight It 40 80 lb-140 lb. 35 lb-140 lb ). 80 lb.-140 1 b. 35 lb-140 lb weight) (dressed of pigs IO IO 10 12 12 12 8 8 8 8 8 Carcass Percentage. Percentage. Percentage. Percentage. Percentage. Percentage. Percentage. Percentage. Percentage. Percentage. Percentage. Streak . 94 95 93 • 87 94 7 51 45 54 44 55 loin Eye 51 52 54 60 60 60. 46 46 51 51 47 Proportion 86 73 57.90 80 75 40 34 65 50 69 loin of Length 29 19 18 39 33 32 . 4 0 7 3 3 period: Whole (i) 50 lb.-200 lb. live-weight. (2) Early period: 50 lb.-120 lb. live-weight. (3I Late period: 120 lb. - 200 lb. live-weight. * Series A and B ; Evaluation bv measurement. Series C : Evaluation by standard photographs. : 50 lb.-120 lb. live-weight. (3) Late period : 120 lb. - 200 lb. live-weight. 50 lb. - 200 lb. live-weight. (2) Early period ; Evaluation bv measurement. Series C : Evaluation by standard photogra phs. * Series A and B

Table VII. Summary of Cascas-Quality Results Percentage Efficiency

Series and Group Number. Supplementingrate. Streak Thickness and Quality (London). (Frozen Carcass.) Belly Measurements (New Zealand). * Thickness. Marks(r). . Marks(z). Middle. Flank.. Series A. Lb. Millimetres. Percentage. Percentage. Inches. Inches. I Nil 52 94 54 i-5 I • I 2 I 50 95 40 i-4 I • I 3 2 50 93 47 i-5 I • I Series B. I Nil 45 87 65 i-4 I • I 2 a 47 94 68 1-'3 1 -o 3 . 4 46 46 87 87 63 63 i-4 1-4 I • I 1 • 1 Series C. i Nil Not taken. 5i 1-25 1-2 2 120 Comparison a r i s 0 n 45 45 1-20 1 • 20 I '2 I • 2 3 4° standard photo54 1-23 1-2 4 160 graphs more 44 1-25 I -2 5 85 satisfactory. 55 1 • 20 1-2 Index.

Table VIII. —Effect on Thickness and Quality of Streak, and on Belly Measurements.

(1) Marks on measurement. (2) Marks on eye appraisalstandard photographs. *Measurements as available for commercial grading—uncut side.

Group and Series Number. Average Carcass Weight. Fat . Thickness (average). Range in Fat Measurements. . Average Marks awarded. Percentage possible. I . . • • Lb. 137 Series A. Millimetres. 25-4 Millimetres. 20-32 17-0 86 2 . . . . . . 138 27’4 24-34 14-5 73 3 • • . .. ' . 140 31-0 29-36 II-5 57 . i .. . 136 Series B. 23'7 20-29 18 -o 90 ■2 . . . . ■ . . ■ 138 138 25’7 25’7 22-34 22-34 16-0 . 16-0 80 80 3 • • 139 27-0 23-42 i5-o 75 I . . ’ .. • 146 Series C. 29-0 25-37 8-o 40 2 . . . . . . 146 29-6 24-36 7-0 ■ 35. 3 • • .. .. 146 26-0 22-29 12’5 65 4 ... 142 28-0 23-38 10 • 0 50 5 •• •• •• . ■147 25 • 75 21-27 14-0 70

Table IX. —Effect on Proportion of Fat: Measurements on Loin-cut (Frozen Carcass.)

Group and Series Number. ; Meal-supple- . menting Rate.* ■ Back-fat Thickness at . Grading Quality. Shoulder. Loin. ' First Grade. Second Grade 1 Second Grade I . . Lb. • ’ Nil Series . A. Inches. I-6 5 Inches. 1-05 Percentage. 60 • O Percentage. 40-0 2 . . . I 4 O : I • 70 I • IO 40-0 60-o 3 • • 260 1-90 .. 1 -20 ; .. 100:o. * 100-o i . . Nil Series B. ' - 1 • 60 1-38 58-0 42-0 2 . . 130 . i-65 •1 3.0 ■ 42-0 58-0 3 •• 200 i-75 ■ " i-37 ' 34’° 66-o I . . Nil Series C. 1-76 J- IO 37’5 62-5 2 . . 120 2-00 I • 20 100-0 3 •• 40 i-75 I • 00 62-5 37‘5 4- • • 160 . • 90 I • 00 100 5 • ■ 85 i-75 I • 00 62-5 . 37’5

Table X.—Effect on Shoulder-fat Thickness and Commercial Grading Quality

Series C Group. * Iodine Numbers of Meal.fed per 100 lb. Carcasses. Frozen Carcasses. Cured Bacon : Fat.' Lb. i .. ' .: 57’5 ' ' 55 2 Lb. Nil 2 .. .. 57’3 58-6 120 3 57’7 55-6. 40 4 57’4 56-7 160 5 5 7-o 56-q 85

Table XI. —Quality of Fat Hardness.