Effect of high dietary fat content on heat production and lipid and protein deposition in growing immunocastrated male pigs

Abstract

In immunocastrated (IC) pigs, revaccination (V2) increases lipid deposition (LD) because of increased voluntary feed intake; but little is known on associated effect of diet composition on partitioning of nutrients in IC pigs. Digestibility measurements, N and energy balances in respiration chambers were performed in two subsequent stages in four replicates of two male littermates to determine the changes between 85 (stage 1) and 135 (stage 2) kg live weight due to combined effect of IC, growth and increased feed intake (IC/growth). During stage 1, pigs received a standard low-fat diet (LF diet; 2.5% dry matter (DM) of fat fed at 2.27 MJ metabolizable energy (ME)/kg BW 0.60 per day), whereas during stage 2, feed intake was increased to 2.47 MJ ME/kg BW 0.60 per day and one littermate was fed LF diet whereas the second received a fat-enriched diet (HF diet; 8.9% DM of fat) to determine the effect of increased dietary fat content on energy utilization in IC pigs. Results from N balance and measurements of gas exchanges were used to calculate respiratory quotient (RQ), heat production (HP), nutrient contribution to fat retention, components of HP, protein deposition (PD) and LD. Nutrients and energy apparent digestibility coefficients, methane losses and N retention ( P < 0.05) increased with IC/growth. Despite higher ME intake, total HP remained similar (1365 kJ/kg of BW 0.60 per day; P = 0.47) with IC/growth. Consequently, total retained energy (RE) increased with IC/growth (from 916 to 1078 kJ/kg of BW 0.60 per day; P < 0.01) with a higher fat retention (625 to 807 kJ/kg BW 0.60 per day; P < 0.01), originating mainly from carbohydrates associated with a higher lipogenesis (536 to 746 kJ/kg BW 0.60 per day; P < 0.01) and RQ (1.095 to 1.145; P < 0.01). Both PD (from 178 to 217 g/day; P = 0.02) and LD (from 227 to 384 g/day; P < 0.01) increased due to IC/growth. Feeding HF diet after IC was associated with increased crude fat digestibility (P < 0.01) and increased RE as fat (807 to 914 kJ/kg BW 0.60 per day; P = 0.03), originating mainly from dietary fat ( P < 0.01) and resulting in increased LD (384 to 435 g/day; P < 0.01) and lower RQ (from 1.145 to 1.073; P < 0.01). Altogether, present results indicate that increased fatness of IC pigs is a result of increased daily LD caused by higher energy intake and lower basal metabolic rate. In addition, LD is further enhanced by dietary energy enrichment with fat after V2.

Sustainability of Pork Production with Immunocastration in Europe

“…Thereafter, animals change their metabolism within two weeks [87,88] as described in Section 3.1. In contrast to the increased fat deposition after second vaccination [23,89], the protein deposition seems to remain nearly constant [90]. However, because of the increased feed intake after the second vaccination as described in Section 3.3, the feed intake can be limited or the amount of protein per kg of feed, to limit the increase in nitrogen emission.…”

“…The difference in basal metabolism can be directly linked to the level of testosterone and anabolic hormones. The difference in energetic efficiency is indicative of the utilization of dietary protein as an energy source for ATP provision and lipid deposition [90], which is less efficient than the utilization of carbohydrates and lipids for such purposes [95]. Most of the time, feeding recommendations are nevertheless supported by measurements in animals in a steady state, e.g., before the second vaccination, or when the transition phase has finished.…”

The Use of Pork from Entire Male and Immunocastrated Pigs for Meat Products—An Overview with Recommendations

“…With IC, after the second immunization (usually performed 4–6 weeks prior to slaughter and at the age of 19–20 weeks), which is marked by the decline of testicular steroids, increase in voluntary feed intake, swift change in metabolism from boar-like to more castrate-like and lower basal metabolic rate, the metabolism rapidly changes towards increased fat synthesis [ 9 , 28 , 29 ]. While not markedly affecting muscle growth (remaining at the similar level), the changes are most notably observed on various carcass fat depots [ 22 ].…”

“…Compared to SC, both EM and IC present a metabolically very distinct animal type. Whereas a SC experiences early castration, late castration is practiced in IC, causing rapid metabolic changes (especially in regard to lipid metabolism), resulting in increased feed intake and fast growth [ 8 , 9 ]. On the other hand, EM are characterized by high androgenic potential, low feed intake and high protein deposition abilities [ 5 ].…”

Immunocastration as Alternative to Surgical Castration in Pigs

“…The way to control fat deposition in immunocastrates would be the manipulation of their diet after the second vaccination. Restricted feed intake [48] or energy dilution [51] improves carcass leanness due to lower fat deposition.…”