Reproductive Performance, Retention Rate, and Age at the Third Parity According to Growth Rate and Age at First Mating in the Gilts with a Modern Genotype

Abstract

Background: Gilts represent the largest category (18-20%) of female pigs in a breeding herd. Under field conditions, the amplitude of growth rate and age at the first mating of gilts are remarkably higher than the recommendations made by the genetic companies. There are several studies that have considered the management of these animals starting from their introduction to the herd till the mating. It has been noted that the genetic selection constantly promotes evolution that may change certain traits of these animals. However, there is a lack of the studies that evaluate the management strategies suitable for the modern sows. This study, therefore, aimed to evaluate the effect of age and growth rate of gilts at the first mating on productive performance and retention rate until the third farrowing.Materials, Methods & Results: The study was performed in a gilt development unit (GDU) with a breeding stock capacity of 1000 females and a goal of 90 gilts mating per week. The groups were retrospectively created according to age (<210 d and ≥210 d) and the growth rate (GR; <700 g/d and ≥700 g/d) at the first mating with a 2 × 2 factorial design. A real-time ultrasound examination was performed at approximately 28 days after artificial insemination to detect pregnancy. Afterward, the productivity data over three parities of 703 females were collected and analyzed at 28 commercial farms of destination. The analyses were performed using SAS, with individual gilts as the experimental unit. The total number of piglets born and the age at the third parity were analyzed using the PROC MIXED. The number of estrus at breeding, weaning-to-estrus interval and the number of piglets in the previous farrowing were included as covariates in the model of total piglets born. The farrowing rate and retention rate until the third parity were considered as binary responses and analyzed using logistic regression (PROC GLIMMIX). The effects of age, GR, and their interaction were included as fixed effect in all analyses. There was no effect of age and GR and their interaction (P > 0.05) on farrowing rate after first, second, and third mating. The total number of piglets born in the three first farrowing and over three parities were not affected (P > 0.05) by the age and GR at first mating. The retention rate until the third farrowing of gilts inseminated with more than 210 days of age was approximately 7% greater than in the gilts mated younger; however, no statistical difference (P > 0.05) was detected. An effect of the age at the first mating was observed in the age to reach the third farrowing. Gilts mated with less than 210 and more than 210 days reached the third farrowing, respectively, at 604.5 ±1.9 and 625.1 ± 2.7 days of age (P < 0.001).Discussion: With a minimum GR of 550 g/d, 180 days of age, and at least 130 kg of weight, gilts are eligible to be inseminated without impairing their litter size, farrowing, and retention rate until the third parity. The gilts having modern genotypes can have a high stillbirth rate if bred with an excessive body weight. It is worth to consider that the gilts inseminated with > 700g/d did not present overweight in this study. The reproductive performance expressed by farrowing rate and piglets born and the longevity expressed by the retention rate from the first pregnancy until the third parturition were not impaired by the groups of age and GR in Large White × Landrace crossbred (Camborough 23®). In addition, gilts inseminated earlier than 210 days but having the minimum required weight resulted in less non-productive days for the breeding herd, which represents an important financial rate to the system.

Age and weight at first mating affects plasma leptin concentration but no effects on reproductive performance of gilts

“…Many gilt development programs recommend that gilts are first bred at a minimum of 210 days of age [12]. However, recent protocols from Europe, in particular Denmark, now recommend that gilts are bred at an older age and heavier weight [13].…”

“…Furthermore, the result of this study showed that weight at mating also did not affect the longevity and litter performance. It has been stated that growth rate and body weight of gilts are more correlated to litter size in the first parity than the total farrowing rate [12]. A higher production cost is expected for gilts mated older and heavier due to higher body weight and likely higher maintenance requirements during their lifetime [4].…”

Utilization and reproductive performance of gilts in large-scale pig farming system with different production levels in China: a descriptive study

“…However, due to the shortage of sow source, the age of introduction/first mating in all groups was generally older, especially in LP-CP group. This not only caused the gilts to miss the optimal mating period (second or third estrus), increased the NPDs and feed consumption due to excessive feeding time, but also further reduced the estrus rate due to excessive weight gain [ 1 , 22 ]. Gilts that missed the mating period will occupy a corresponding number of individual columns while waiting for the next estrus period.…”

“…Gilts are the basis for maintaining fertility in large-scale pig farms, which is the largest category in the breeding herd, accounting for 18–20% [ 1 ]. When sows are culled from the pig herd due to high parities or low reproductive performance, gilts must be introduced to ensure the reasonable parity structure of the sows in the pig farm and the stability of production objectives.…”

The importance of optimal body condition to maximise reproductive health and perinatal outcomes in pigs

“…Gilts with a good appetite should be selected; however, attention must be considered to prevent their excessive fattening (66) , as Filha et al (67) reported that gilts with growth rate (GR) from birth to insemination greater than > 770 g/d had a larger litter size but a higher percentage of stillborn piglets compared with the gilts with lower GR. According to Faccin et al (68) , gilts should have at least one oestrus prior to insemination with a minimum average daily gain (ADG) of 550 g, 130 kg of body weight and at least 180 d of age. If these criteria are met, no negative effects on litter size and longevity until the third parturition should be observed.…”