Effect of zinc and phytase supplementation on performance, serum biochemical profiles and carcass quality of crossbred (Hampshire × Assam local) pigs

Abstract

Twenty-four castrated weaned (42 days, 11.39 kg) pigs were used in a 2 × 2 factorial experiment to determine the influence of dietary zinc (0 upto 100 ppm/kg) and phytase (0 or 200 FTU phytase units/kg) supplementation on the performance, serum biochemical profiles and carcass quality. Growth rate and feed efficiency were significantly higher (P < 0.05) for pigs supplemented with phytase and zinc. Total serum protein, glucose, cholesterol, Ca, P and Zn concentrations were significantly higher (P < 0.05) in phytase supplemented group, whereas serum alkaline phosphatase estimates were lower (P < 0.05). No significant differences in carcass characteristics and proximate composition of meat were observed which indicated no adverse effect of zinc and enzyme supplementation. These results indicated that the growth-promoting effect of phytase may be due to increased zinc and other serum mineral concentrations and zinc dependent blood biochemical functions.

Keywords:

• carcass
• performance
• phytase
• pig
• serum
• zinc

1. Introduction

Zinc is an essential component of around 1000 metalloenzymes involved in a range of biochemical functions within the body. Its absorption is influenced by the level and source as well as presence of interfering substance like phytate (Pallauf 2005). The two third of phosphorus in cereal feeds is in the form of phytate, i.e. ionositol hexaphosphate and pentaphosphate, but, only a small portion of it can be utilised by pig that producing negligible amount of phytase, so exogenous supplementation of phytase is an alternative for enhancing the performance. Hence, present study was planned to assess the general effects of zinc supplementation with and without phytase on the performance of crossbred (Hampshire × Assam local) pigs in the hot-humid condition of Assam, India.

2. Material and methods

2.1. Selection and feeding management of animals

Twenty-four weaned castrated (42 days, 11.39 kg) crossbred (Hampshire × Assam local) piglets maintained at All India Coordinated Research Project on Pig, College of Veterinary Science; Assam Agricultural University were randomly divided into four groups of six animals in each namely T₁, T₂, T₃ and T₄ and offered ad lib. grower (CP 18.5% and 3.16 Mcal ME/kg diet) up to 50 kg body weight and finisher diet (CP 16.1% and 3.3 Mcal ME/kg diet) up to slaughter age. The zinc content in the grower and finisher diet was 50.9 and 50.2 ppm, respectively. No additional zinc and phytase was supplemented in the diet of T₁ group and acted as control. In the diet of T₂ group phytase was added at 200 unit/kg diet. Zinc was supplemented in the diet of T₃ group as ZnSO₄·7H₂O to make it 100 ppm. In T₄ group, both zinc and phytase, as above mentioned dose was supplemented in feed.

2.2. Sample collection and analysis

Blood samples were collected from anterior vena cava at 30 days intervals and separated serum samples were used for estimation of serum enzyme alkaline phosphatase and the blood metabolites (protein, cholesterol and glucose) following the method described in commercial kits (Merck) and rest of the samples were stored at −30°C for further analysis of minerals. The Zn content of feed and blood was estimated with the help of Atomic Absorption Spectrophotometer (GBC932AA). The Ca and P were estimated with the help of UV end point method described in commercial kit (Merck).

2.3. Carcass characteristics

Three animals from each group were slaughtered at the end of the experiment following electrical stunning method. After complete bleeding, the carcasses were washed and carcass weight was measured without head after 30–35 minutes of final washing. The carcasses were halved along the posterior median line through vertebrae after evisceration. Carcass length was measured between the anterior edges of the first rib to the aitch bone. The average back fat thickness was the mean of three measurements taken at the level of first rib, last rib and lumbar vertebrae. Loin eye area was recorded on the cut surface of the longissimus dorsi muscle at the interface of 10th and 11th ribs on both side of the carcass after tracing on ‘tracing paper’ and area was measured using compensating planimeter with optical tracer. Dressing percentage was calculated from the hot carcass weight of pigs just before sacrifice. The meat samples of 150–200 g were collected from the longissimus dorsi muscle in the area between 10th and 11th rib and analysed to estimate its proximate composition.

2.4. Chemical analytical of feed

The chemical composition of the diets was determined according to AOAC (2000) method (Table 1).

Table 1. Percentage ingredients and chemical composition of experimental diets.

Ingredients (%)	Grower ration	Finisher ratio
Maize	55	40
Wheat bran	14	40
DGNC	16	10
Soya bean	6	2
Fish meal	6	5
Min. mixture	2.5	2.5
Common salt	0.5	0.5
Total	100	100
Zinc (ppm)	50.9	50.2
Chemical composition (% on DM basis)
CP	18.5	16.3
EE	3.85	3.92
CF	5.80	5.84
NFE	61.57	63.69
Total Ash	10.28	10.25
ME (Mcal/kg) (calculated)	3.16	3.23

Note: Vitamin premix was added @ 25 g/100 kg diet in both the grower and finisher ration.

2.5. Experimental measurements and statistical analysis

Feed intake was recorded daily and body weight data were recorded at fortnightly intervals. Feed conversion efficiency was calculated from this data. The study was conducted in a 2 × 2 factorial method using randomised block design. Data generated in the study were analysed statistically as per the procedure of Snedecor and Cochran (1994) with the use of SPSS (1996) statistical software package.

3. Results and discussion

3.1. Performance of piglets

Statistically significant difference (P < 0.05) in respect of zinc level (338.50 ± 12.11 vs. 361.10 ± 14.24 g/d) was found on average daily body weight gain among the experimental groups, i.e. average of T₁ and T₃ vs. T₂ and T₄. The final body weight in T₄ group was higher (8.06 kg) than the body weight of T₁ group, whereas margin was about 3.50 and 3.05 kg in case of T₂ and T₃ groups, respectively. The body weight gain due to phytase supplementation might be due to the release of phytate bound proteins. Improvement in weight gain due to phytase and zinc supplementation was also reported by Martinez et al. (2005). Statistically, no significant difference (P > 0.05) was found for average feed intake among the groups. The average feed conversion ratio was found to be highest in T₁ among the experimental groups and statistically, significant effect was observed (P < 0.05) due to phytase level (4.61 ± 0.02 vs. 4.36 ± 0.02) only. Jondreville et al. (2007) also reported improved (P < 0.05) feed conversion efficiency due to phytase supplementation (Table 2).

Table 2. Growth performance, serum biochemical profiles, carcass characteristics and proximate composition of meat.

Traits	Experimental groups
	T1	T2	T3	T4
Levels of zinc and phytase per kg diet	50 ppm Zn + 0 phytase	50 ppm Zn + 200 FTU phytase	100 ppm Zn + 0 phytase	100 ppm Zn + 200 FTU phytase
Growth performance
Initial body weight (kg)	11.82 ± 1.09	11.10 ± 0.73	11.37 ± 0.58	11.30 ± 0.78
Final body weight (kg)	70.70 ± 2.62^a	74.20 ± 3.18^b	73.74 ± 3.14^b	78.76 ± 3.15^c
Total gain (kg)*	58.88 ± 1.03^a	63.10 ± 1.33^b	62.37 ± 1.13^b	67.46 ± 1.64^c
Gain per day (g)*	327 ± 12.06^a	350 ± 14.41^b	347 ± 13.58^b	375 ± 16.61^c
Feed intake (kg)*	276.49 ± 1.23	282.68 ± 1.35	282.55 ± 1.20	287.01 ± 1.06
Feed conversion efficiency*	4.69 ± 0.08^a	4.48 ± 0.06^b	4.53 ± 0.06^c	4.25 ± 0.07^d
Serum biochemical profiles
Protein (g/dl)*	6.61^a ± 0.07	6.85^b ± 0.12	6.70^b ± 0.08	6.97^c ± 0.15
Cholesterol (mg/dl)*	173.26^a ± 1.04	176.24^b ± 1.92	175.96^b ± 1.76	177.95^b ± 2.22
Glucose (mg/dl)*	80.11^a ± 0.14	80.81^b ± 0.15	80.29^ab ± 0.11	81.52^b ± 0.13
ALP (KAU/dl)*	23.60^a ± 1.52	17.86^b ± 0.36	25.17^c ± 1.82	17.85^b ± 0.25
Serum mineral concentration
Zn (ppm)*	0.829^a ± 0.03	0.899^b ± 0.04	0.898^b ± 0.05	0.985^c ± 0.04
Ca (mg/dl)*	7.93^a ± 0.18	8.18^a ± 0.19	8.08^a ± 0.18	8.31^b ± 0.26
P (mg/dl)*	5.50^a ± 0.05	5.78^b ± 0.06	5.66^c ± 0.06	5.98^d ± 0.03
Carcass measurements
Live weight (kg)	71.67 ± 0.17	73.12 ± 0.06	73.20 ± 0.46	75.53 ± 0.12
Slaughter weight (kg)	70.79 ± 0.16	72.16 ± 0.03	72.54 ± 0.35	74.42 ± 0.20
Carcass weight (kg)	49.02 ± 0.19	51.29 ± 0.02	50.91 ± 0.22	53.46 ± 0.12
Dressing percentage (%)	69.01 ± 0.08	71.08 ± 0.02	70.28 ± 0.29	71.83 ± 0.03
Carcass length (cm)	70.77 ± 0.18	71.86 ± 0.14	72.23 ± 0.34	74.67 ± 0.23
Back fat thickness (cm)	2.81 ± 0.07	2.67 ± 0.02	2.79 ± 0.02	2.50 ± 0.09
Loin eye area (cm^2)	22.85 ± 0.08	22.95 ± 0.18	24.18 ± 0.12	25.14 ± 0.06
Proximate composition of meat (%)
Moisture	74.34 ± 0.13	74.53 ± 0.05	74.26 ± 0.05	74.59 ± 0.11
Protein	20.73 ± 0.09	20.94 ± 0.06	20.87 ± 0.05	21.25 ± 0.05
Fat	2.58 ± 0.06	2.56 ± 0.06	2.53 ± 0.06	2.44 ± 0.05
T. Ash	1.19 ± 0.04	1.21 ± 0.04	1.21 ± 0.03	1.22 ± 0.02

Note: Means in a row bearing different superscript differ significantly (*P < 0.05).

3.2. Changes in enzyme activity and metabolic profile

The serum protein level was higher in T₂ and T₄ than the other two groups. Statistically significant (P < 0.05) difference was observed among the groups in respect of phytase levels (6.63 ± 0.08 vs. 6.91 ± 0.09 g/dl), but zinc level has no influence on total serum protein. Elevated serum protein level in T₂ and T₄ might be due to better utilisation of zinc due to phytase activity which might have involved in better assimilation of protein from available dietary protein (Grela & Pastuszak 2004). The blood glucose level was significantly (P < 0.05) higher in T₂ and T₄ in respect of phytase levels (80.20 ± 0.11 vs. 81.16 ± 0.19 mg/dl) indicating involvement of zinc in carbohydrate metabolism. Significant (P < 0.05) effects were observed among the groups in respect of phytase levels (174.61 ± 1.34 vs. 177.09 ± 0.97 mg/dl) as well as zinc level (174.75 ± 0.83 vs. 176.95 ± 0.92 mg/dl) on serum cholesterol concentration. It is higher in T₂ and T₄ compared to T₁ and T₃ groups. It might be due to the increased level of glucose, the precursor for cholesterol synthesis. The serum alkaline phosphatase activity was decreased along with the advancement of age in the groups supplemented with zinc and phytase while it was increased in the group supplemented with zinc without phytase. It is significantly (P < 0.05) higher in T₁ and T₃ when compared to T₂ and T₄ group. The decreased activity due to phytase supplementation might be resulting from the increased availability of phosphorus (Huff et al. 1998).

3.3. Changes in serum mineral concentrations

Significant (P < 0.05) differences were observed in respect of phytase levels (8.00 ± 0.09 vs. 8.25 ± 0.08 mg/dl) on serum calcium concentration. Phytase supplementation might have acted upon the bound phytate mineral complex resulting in an increased availability and improved absorption. Veum et al. (2006) also observed higher serum calcium concentration on phytase supplementation. Significant (P < 0.05) difference on serum inorganic phosphorus concentration was observed in respect of phytase level (5.58 ± 0.03 vs. 5.88 ± 0.03 mg/dl) as well as zinc level (5.64 ± 0.04 vs. 5.82 ± 0.05 mg/dl) which might be due to the hydrolysis of bound phytate phosphorus by the enzyme phytase. Significant (P < 0.05) difference in serum zinc concentration was observed in respect of phytase levels (0.864 ± 0.01 vs. 0.942 ± 0.01 ppm) as well as zinc levels (0.863 ± 0.01 vs. 0.941 ± 0.02 ppm). Phytate was reported to suppress the absorption of zinc secreted in to the digestive tract and also stimulates intestinal fluid secretion. (Baidoo et al. 2003; Hademann et al. 2006).

3.4. Carcass and meat quality attributes

The dressing percentages of the experimental groups were ranged from 69.01 ± 0.08% to 71.83 ± 0.03%. The loin eye areas ranged from 22.85 ± 0.08 to 25.14 ± 0.06 cm² among the groups. The trend of carcass length was similar to that in live weight gain of the animals ranges from 70.77 ± 0.18 to 74.67 ± 0.23 cm among the groups. Walz and Pallauf (2003) also reported higher rate of carcass weight gain associated with longer carcass length. However, the average back fat thickness of the pigs ranged from 2.50 ± 0.09 cm in T₄ to 2.81 ± 0.07 cm in T_1, respectively. The values declined with increasing level of zinc and phytase in the diet. The proximate composition of the longissimus dorsi muscles of the experimental pigs in the present study did not show any significant difference among the groups.

4. Conclusion

It is inferred that growth-promoting effect of phytase may be due to overall increase in zinc and other minerals as well as the activities of serum biochemical functions. Present study indicated that 100 ppm zinc with 200 FTU phytase/kg diet can be recommended for optimum growth without any adverse effect on carcass characteristics and proximate composition of longissimus dorsi muscles of the cross bred pigs.

Acknowledgements

To the Indian Council of Agricultural Research, Government of India, for providing necessary facilities under All India Coordinated Research Project on ‘Improvement of feed resources on nutrient utilization in raising animal production’ and All India Coordinated Research Project on Pig, College of Veterinary Science, Khanapara, Assam to carry out the research work.

Disclosure statement

No potential conflict of interest was reported by the authors.