Trial Report - Welsh Pork Loin Project

 

Prepared by: Caroline Mitchell

FQM Global

Date: November 2021

 

 

 

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Introduction:

In 2021 Menter a Busnes and Forest Coalpit Farm commenced a trial to compare the meat quality of pigs finished in a forage rich paddock to pigs finished in a barren paddock. The fatty acid profile of the pork produced was of particular interest. 

All data was analysed using one-way ANOVA in Excel. 

Aim & Hypothesis:

To establish if a forage based system has a significant impact on pork quality

      H0 - There is no difference between treatment groups
      H1 - There is a difference between treatment groups

 

Trial Design & Allocation to Group:

Sows in the same group that were either full or half siblings were identified. The identified females were served using the same terminal sire. The intent being that by using the same sire, there is no boar effect in the data. In addition, by using females that were closely related, genetic variation is limited as much as possible in the trial pigs. 

After farrowing the piglets were group reared until weaning, thereby standardising environmental effects. Piglets were weaned at 45 days. Upon weaning, the cohort was kept together until they were allocated to a treatment group at 92 days old.

Only gilts were used for the trial so that there is no sex effect in the dataset. Pigs were allocated to the treatment groups at random. 

       Group 1 = 10 gilts – Standard Feed + Barren Paddock
       Group 2 = 9 gilts – Standard Feed + Forage Paddock

Once allocated to a group the pigs were given an ear tag (Orange = No forage, Green = Forage) to assist with identification in the abattoir. 

 

Feeding regime:

Feed was slightly restricted to encourage the pigs to eat the forage. The restriction was applied to both treatment groups with 2kg per head per day being made available to the animals. 

Over the period of the trial the animals were given two different feed rations:
Feed 1 – Grower Spec 
Feed 2 – Finisher Spec 
With the switch from Grower to Finisher ration occurring at day 120.

Specifications of the feed rations used can be seen in Appendix 1

 

Slaughter:

Once the average live weight of both treatment groups was approximately 93kg the pigs were taken to slaughter. All animals were killed on the same day (3rd September 2021) at W J George Cross House, High St, Talgarth, Brecon LD3 0PD. They were transferred from farm to abattoir as per usual farm practice. The pigs were kept in their established groups to minimise stress and fighting.

The animals were killed using electric stun and stick as per the usual abattoir protocols.

 

pH & temperature assessment:

After weighing the carcass, the pigs were transferred to the chiller where each pig was given an individual ID 1 – 19 using a chinograph pencil and the pH45 and temperature 45 were measured (Hanna instruments, HI-98163 Portable pH Meter for Meat) and recorded. Assessment was made at point of P2 on the left-hand side of each pig. The carcasses were then chilled overnight as per standard site practice before being transported 28 hours later, under refrigerated conditions, to the refrigeration unit at Forest Coalpit Farm.

On the Sunday 48 hours post-kill the carcasses were butchered into primals. The individually ID’d loins had two loin steaks, 2.5 cm thick, removed at the P2 point. 

One Loin Steak was allowed to bloom for 30minutes under ambient conditions before the colour, NPPC & CEILAB, (Table 2 and 3) were assessed and recorded and then the Temperature24 and pH24 (Table 1) were assessed. The 2nd loin steak was prepared for Drip Loss Assessment.

	Group 1  (No Forage)	Group 2    (+ Forage)	P-value
No.	10	9
Weight (lbs)	161.50	158.22	0.4973	ns
pH45	7.09	7.07	0.8431	ns
Temp45	29.96	30.84	0.2086	ns
pH24	5.64	5.66	0.7363	ns
Temp24	14.80	13.19	0.0120	*

Table 1: pH and Temperature assessment

 

As can be seen in Table 1 there were no significant differences between treatment groups for any of the traits except Temp24. The temperature difference at Temp24 is significant, however, it won’t (and did not) impact any of the additional measures.

 

CIELAB, NPPC & Drip Loss

After the 30-minute bloom time the subjective marbling and colour assessment was carried out by Caroline Mitchell and Lauren Smith using the USDA NPPC cards. The objective CEILAB assessment was carried out using a Konica Minolta CR-200. Because it’s invasive the pH24 and Temp24 were assessed after the visual and CEILAB assessment.

	Group 1 (No Forage)	Group 2 (Plus Forage)	P-value
L*	60.56	59.77	0.4852	ns
a*	10.11	11.91	0.0107	*
b*	6.47	6.62	0.7239	ns

Table 2: CEILAB assessment results

 

As can be seen in Table 2 the CEILAB colour assessment showed that there was significant difference in lightness and blue/yellow but the forage fed group were significantly redder than the non-forage group. However, as can be seen in Table 3 the difference in redness wasn’t translated into the subjective visual assessment.

For drip loss assessment the Honikel “Inflated Bag Method” was used. While the 1st loin steak was being left to bloom the second 2.5cm thick loin steak was trimmed of all backfat, being careful not to cut into the muscle structure. The trimmed loin eye was then blotted and weighed, and the weight recorded. 

A length of butcher’s string was then inserted into the loin eye about 1inch from the edge. The loin eye was then suspended in a food bag ID’d with the pigs trial ID number. The bag was inflated and sealed around the meat sample, ensuring the meat surface didn’t touch the bag. Using the tails of the butchers string the bags were then hung from the racking in the fridge making sure that no bags touch and no meat touches the bags.

 

The bags of meat were left suspended in the fridge until Fri 10th Sept. 6d post-mortem (Day of slaughter being day 0) and 5 days suspended. On the 10th of September the meat was removed from the bags, the surface blotted to remove excess water and then the sample was re-weighed. 

The difference in weight was calculated so that a percentage (%) moisture loss between treatment groups could be analysed.

	Group 1  (No Forage)	Group 2 (Plus Forage)	P-value
Drip Loss (%)	7.55	6.08	0.1042	ns
Marbling Score (Ave)	1.80	1.61	0.2977	ns
Colour Score (Ave)	3.35	3.22	0.6336	ns

Table 3: Drip Loss (%) and Subjective Visual Assessment

 

The forage fed group had a slightly lower Drip Loss (%) however, the difference between treatment groups wasn’t significant. 

 

Analysis of Data from Coleg Menai:

All of the methodologies used by Coleg Menai can be seen in their report. 

	Group 1 (No Forage)	Group 2 (Plus Forage)	P-value
Cooking Loss (%)	26.28	24.68	0.1814	ns
Weight Loss Cooking & Chilling (%)	29.49	27.50	0.1029	ns
Warner Bratzler	6974.29	7208.86	0.3061	ns
Warner Bratzler (outlier removed)	6903.71	7208.86	0.1634	ns

Table 4: Cooking Loss and Warner Bratzler Results

There was no significant difference between treatment groups for Cooking Loss, Weight Loss and Chilling or Warner Bratzler/Tenderness. For the Warner Bratzler statistical analysis, a second ANOVA was carried out with “Group A4 Core 1 sample 19” data removed because at 11138.06g peak force the reading was considered an outlier. Removal of the outlier didn’t result in any significant difference between treatment groups. 

	Group 1 (No Forage)	Group 2 (Plus Forage)	P-value
NIR: Fat	18.38	18.71	0.8537	ns
NIR: Protein	19.37	19.37	0.9978	ns
NIR: Moisture	62.08	61.46	0.6335	ns
NIR: Collagen	1.42	1.45	0.4655	ns

                                                    Table 5: NIR Analysis 

There was no significant difference between treatment groups for NIR analysis (Table 5).

	Group 1 (No Forage)	Group 2 (Plus Forage)	P-value
Fat (g/100g)	3.26	3.51	0.5972	ns
Moisture (g/100g)	72.74	72.57	0.7305	ns
Ash (g/100g)	1.10	1.12	0.1639	ns
Hydroxyproline (g/100g)	0.07	0.08	0.7503	ns
Collagen (g/100g)	0.58	0.62	0.7503	ns
Carbohydrate (g/100g)	0.10	0.10	~
Protein (g/100g)	23.36	23.07	0.1105	ns
Energy (KJ/100g)	518.30	522.22	0.8100	ns
Energy (Kcal/100g)	122.90	123.89	0.8039	ns

Table 6: Chemical Analysis 1

 

There was no significant difference between treatment groups for Chemical Analysis 1 (Table 6). For the Carbohydrate g/100g all results were 0.1 for all animals meaning a P-value couldn’t be calculated.

Following the UK Government guidelines for food labelling we can see that both treatment groups are just inside the amber zone for fat content/100g. However, when we look at the Chemical Analysis Set 2 data (Table 7) we can see that Group 1 animals have 1.4g Saturates/100g and Group 2 animals have 1.6g Saturates/100g. Group 1 would be green for Saturates while Group 2 would be amber. While there isn’t a significant difference between the two saturated fat levels when equal amounts of fat are compared, because the Group 2 have slightly more total fat in combination with slightly more saturated fat, it affects how the product could be categorised.

 

Chart 1: UK Traffic Light System for Food Labelling

Source: https://www.pid-labelling.co.uk/sandwich-label-nutrition-traffic-lights…
 

However, the differences are not enough for there to be differences in processing yields or fat “setting” ability. In addition because the data set is relatively small we would need more data to confirm the classification categories.

A second set of chemical analysis was carried out looking at the fatty acid profile of the two treatment groups. The more detailed analysis was requested because it was believed that the addition of forage would have an affect on the fatty acid profile more than any other trait. 

	Group 1 (No Forage)	Group 2 (Plus Forage)	P-value
Total Saturated (%)	44.08	44.77	0.2943	ns
Total Mono (%)	41.27	40.34	0.1207	ns
Total Poly (%)	14.34	14.56	0.7506	ns
Total Trans (%)	0.30	0.34	0.1114	ns
Lauric Acid (C12:0) (%)	0.02	0.01	0.7216	ns
Myristic Acid (C14:0) (%)	1.14	1.10	0.2090	ns
Palmitic Acid (C16:0) (%)	27.52	27.24	0.3479	ns
Palmitelaidic Acid (C16:1n9t) (%)	0.28	0.31	0.0604	ns
Palmitoleic Acid (C16:1) (%)	3.05	2.67	0.0092	**
Heptadecanoic Acid (C17:0) (%)	37.28	36.69	0.2649	ns
cis-10-Heptadecenoic (C17:1) (%)	0.18	0.21	0.4345	ns
Stearic Acid (C18:0) (%)	15.09	16.04	0.0460	*
Oleic Acid (C18:1n9c) (%)	37.28	36.69	0.2649	ns
Linoleic Acid (C18:2n6c) (%)	11.31	11.22	0.8584	ns
Linolenic Acid (C18:3n3c) (%)	0.66	0.97	0.0008	***
Arachidic Acid (C20:0) (%)	0.07	0.12	0.2350	ns
cis-11-Eicosenoic Acid (C20:1) (%)	0.75	0.77	0.5842	ns
cis-11, 14-Eicosadienoic Acid (C20:2) (%)	0.43	0.44	0.5897	ns
Eicosatrienoic Acid (C20:3n6) (%)	0.05	0.02	0.4165	ns
Arachidonic Acid (C20:4n6) (%)	1.59	1.54	0.8136	ns
Docosapentaenoic Acid (C22:5) (%)	0.30	0.36	0.1141	ns

Table 7: Chemical Analysis Set 2

As can be seen in Table 7 the addition of forage resulted in significant differences between treatment groups for Palmitoleic Acid (P = 0.0092), Stearic Acid (P = 0.0460), and Linolenic Acid (P = 0.0008).

Conclusions:

Linolenic acid was the fatty acid most affected by the addition of forage. Often referred to as α-Linolenic acid (ALA) it is an n-3 or omega 3 essential fatty acid. There are multiple benefits of eating products containing ALA for the human consumer (Heart attack prevention, lowers high blood pressure, lowers cholesterol, reverses hardening of the blood vessels). α-Linolenic acid can only be obtained by humans through their diets because the absence of the required 12- and 15-desaturase enzymes makes de novo synthesis from stearic acid impossible. Pigs are also unable to synthesise ALA and so the significant difference between treatment groups is a direct result of the addition of forage to the diet. 

Studies have shown that through manipulating feed i.e. adding fish/plant/seed oils it is possible to make the meat of pigs into a functional food due to omega 3 and omega 6 content. It would be interesting to see if different forage lays can manipulate the functionality of the meat further.  

The sample size is relatively small at 10 vs. 9 Animals. To draw further conclusions as to the effect of forage on meat quality a larger dataset would be required. 

 

Appendix 1:

	Grower Ration	Finisher Ration
Analytical Constituents:
Crude Ash	4.59%	4.70%
Crude Oils and Fats	3.67%	4.51%
Calcium	0.53%	0.69%
Sodium	0.20%	0.18%
Lysine	1.17%	0.88%
Crude Protein	17.69%	15.86%
Crude Fibre	4.64%	4.47%
Phosphorous	0.43%	0.50%
Methionine	0.40%	0.25%
Vitamins:
Vitamin A (IU/kg)	6500	8500
Vitamin D3 (IU/kg)	1500	1500
Vitamin E (IU/kg)	30	75
Antioxidants:
Butylated hydroxytoluene (mg/kg)	5	5
Trace Elements:
Iron (II) sulphate monohydrate (mg/kg)	100.00	90.00
Manganese (II) oxide (mg/kg)	35.00	60.00
Iodine (Calcium iodate, anhydrous) (mg/kg)	2.00	2.00
Selenium (Sodium selenite) (mg/kg)	0.25	0.25
Copper (II) sulphate pentahydrate (mg/kg)	15.00	15.00
Zinc (Zinc sulphate, monohydrate) (mg/kg)	100.00	90.00
Selenium (E8 Sodium selenite)	0.25
Selenium (Hydroxy analogue of Selenomet)		0.08