Genetic and nutritional effects on lactational performance of gilts selected for components of efficient lean growth

Abstract

Lactational performance was measured in Large White gilts from lines that had been divergently selected over seven generations for daily food intake (DFI), lean food conversion ratio (LFC), lean growth rate with ad-libitum (LGA) or restricted (LGS) feeding during performance test. Control line gilts were included in the study. During the lactation period of 21 days, gilts were given to appetite five isoenergetic diets differing in ileal digestible lysine: energy (0·40, 0·58, 0·76, 0·94 and 1·12 g/MJ digestible energy). The study consisted of 223 gilts with a similar number of animals in each selection line.Live-weight loss was greater in the low LFC and LGA lines than in the high lines and food intake was significantly lower in the low LGA line than in the high line. Litter-weight gain of the low LFC and high LGA lines were greater than in the complementary selection lines. Prediction equations for nutrient utilization were used to express the effect of diet and selection line in terms of energy and protein inputs and outputs. Selection on DFI or LGS resulted in gilts that did not mobilize lipid during lactation as sufficient energy for milk and maintenance was provided by dietary intake. In contrast, there was insufficient dietary energy with selection on LFC or on low LGA so lipid mobilization was required to achieve energy balance. The energy required to excrete excess protein and energy from lipid mobilization increased as the dietary lysine energy ratio increased, but there were no other dietary effects on energy and protein utilization. Genotype with nutrition interactions were detected for energy intake and lipid mobilization, which were due to the lines selected for low DFI and LGA. The general absence of genotype with nutrition interactions for lactational performance in gilts selected for components of efficient lean growth and the lack of significant dietary effects on energy utilization indicated that the consequences of changing nutritional inputs will be broadly similar for genotypes within the set of genotypes studied. Selection strategies which result in reduced food intake during lactation should be avoided if lipid mobilization is then required to attain energy balance and there are resultant negative effects on subsequent reproductive performance.

Genetic correlations between lactation performance and growing-finishing traits in pigs

“…Selection for increased daily FI of grower-finishers resulted in greater backfat thickness at start of lactation. The results of Cameron et al (2002) were in line with our results. The only exception was the genetic correlation of FI as a grower-finisher and FI during lactation, which was, although small, positive in our study.…”

“…This might explain the relatively low genetic correlation for FI with FI as a grower-finisher. Cameron et al (2002) compared lactation performance in Large White gihs between lines that had been divergently selected for daily FI during growing-finishing. Lactation FI did not differ significantly between these selection lines, nor did BW.…”

Estimates of genetic parameters associated with lactation feed intake and growth and composition traits measured during a performance test

“…Cameron et al . () reported that in a population divergently selected for feed intake in the growing pig, selection for improved feed conversion ratio was genetically associated with a numerical reduction in feed intake levels and increased mobilization of body reserves during lactation.…”

“…Unfortunately, direct selection for feed conversion and leanness has been indirectly linked to reduced intake capacity in the long term, reducing sow feed intake and longevity (Hermesch ), and selection for efficient lean growth has resulted in leaner gilts and sows which have fewer body reserves available for mobilization when feed intake during lactation is inadequate (Cameron et al . ). The inclusion of LFI traits in a selection index may provide a sufficient method for improvement as several studies have indicated potential for increasing levels of LFI through direct selection (Lewis & Bunter ; Yoder et al .…”

“…Feed intake and body reserves are the only available sources of nutrients a sow can utilize for maintenance and milk production during lactation (Ball et al 2008), and lactation feed intake (LFI) is frequently inadequate, requiring body reserves to be mobilized to maintain milk production (Noblet et al 1990). Unfortunately, direct selection for feed conversion and leanness has been indirectly linked to reduced intake capacity in the long term, reducing sow feed intake and longevity (Hermesch 2004), and selection for efficient lean growth has resulted in leaner gilts and sows which have fewer body reserves available for mobilization when feed intake during lactation is inadequate (Cameron et al 2002). The inclusion of LFI traits in a selection index may provide a sufficient method for improvement as several studies have indicated potential for increasing levels of LFI through direct selection (Lewis & Bunter 2011;Yoder et al 2014).…”