Factors associated with the production of 30 or more piglets per sow per year in southeastern Mexico

J C Segura-Correa, R Aké-López, J G Magaña-Monforte, R C Montes-Pérez and R Santos-Ricalde

Campus de Ciencias Biológicas y Agropecuarias, Universidad Autónoma de Yucatán.
Km 15.5 carretera Mérida-Xmatkuil, AP 4-116, Mérida, Yucatán, C.P. 97315 México
jose.segura52@hotmail.com

Abstract

The annual pig production is critical for producers managing commercial farms. Thus, the objective of the study was to determine the effect of some environmental factors on the production of 30 or more piglets per sow per year in Southeastern Mexico. Information from 2008 to 2012 of four commercial farms located in Yucatan, Mexico were used. Data on sows producing 30 or more piglets born alive per year (PB/S/Y, n=7471) and sows producing 30 or more weaned piglets per year (PW/S/Y, n=7181) were code as 1, otherwise as 0. Data were analyzed using binary logistic regression. The statistical model included the effects of farm, year of first farrowing, season of fist farrowing, reason of culling, number of pigs born alive at first farrowing, productive lifetime and age at first farrowing.

The frequencies of sows with 30 or more PB/S/Y in farms 1 to 4 ranged from 4.30 to 19.6%, and for PW/S/Y the frequencies ranged from 1.24 to 14.4%. Farm, year, reason of culling, number of piglets born at first farrowing, productive lifetime and age at first farrowing, were all associated with the production of 30 or more PB/S/Y, but for PW/S/Y the number of piglets born at first farrowing and age at first farrowing were not important sources of variation. Farm differences for PB/S/Y and PW/S/Y indicates differences in some management practices. Reducing the reasons of culling by reproductive problems, and increasing the care of early first parity sows with large liter sizes may increase productivity in the farms.

Key words: pigs born alive, pigs weaned, sow productivity, risk factors, tropics

Introduction

Annual pig production is critical for producers managing commercial farms. The annual production of 30 pigs weaned per sow is within the reach of many farms in Europe, Canada and the USA (Gill 2007). However, to achieve that goal good sow fertility and good semen quality for artificial insemination to guarantee conception; maximum number born alive and viable; to minimize the number of non-productive days; and to maximize the number of piglets weaned and market is required (Gill 2007). In addition, the incorporation of genes from the hyper-prolific Meishan breed into pig-breeding programs has contributed to increase litter size.

Some factors may determine the ability to produce 30 or more piglets weaned per sow per year. The age of gilts at first mating is a key factor because gilts mated at younger age show better lifetime performance and longevity (Saito et al 2011; Segura-Correa et al 2011a; Koonawootrittriron et al 2012). Furthermore, the mating age of gilts and the reason of culling are associated with lifetime efficiency and longevity in F₁ crossbred sows in Japan (Sasaki and Koketsu 2011). Differences in pigs weaned per sow per year between farms could also be associated to herd size, management, litter size at first farrowing, and genetic of the sows, as have been found for lifetime performance (Babot et al 2003; Koonawootrittriron et al 2012; Sobczynska et al 2013; Soltesz and Balogh, 2013). Few studies on lifetime productivity have been carried out in tropical regions of the world (López and Galindez 2011; Koonawootrittriron et al 2012) but none dealing with factors associated to sows producing 30 or more piglets born alive or weaned per sow per year.

The knowledge of the proportion of high prolificacy sows and factors affecting them could help in making decisions and choose management practices that could increase the amount of pigs born and weaned, as well as the weaned kilograms of pigs per sow.

The main objective of this study was to determine the effect of some environmental factors on the production of 30 or more piglets per sow per year in four pig farms in the southeastern of Mexico.

Material and methods

Data of four commercial farms located in the state of Yucatan, Mexico were used. Yucatan is localized at latitude 19°30′ and 21°35′ N and, longitude 90°24′ W. The climate of the region is sub-humid tropical, with temperature, rainfall and relative humidity means of 26.6°C, 1,100 mm and 78%, respectively (INEGI 2010). Pig production is a very important commercial livestock activity in Yucatan, ranked fourth at national level.

Four farms with records kept in the Pigchamp® program were chosen. Farms 1, 2 and 4 were full cycle farms with 3,900, 1,200 and 550 sows, respectively, and farm 3 was a two-site-type farm (breeding and production) with 320 sows. All sows were bought from the pig improve company (PIC). All four farms produced their own sow replacements and practiced the quarantine of gilts. Sows were fed commercial diets based on their stage of production. First parity sows were given 2.6 kg/day of a commercial diet with 16% crude protein, 3,000 kcal EM/kg and 0.8% lysine; whereas multiparous sows received 3.2 kg/day of feed. In all farms, breeding was carried out by artificial insemination. After estrous detection, using a boar, sows were inseminated three times every 12 hours. Cross fostering was a common practice in the farms.

Data from 2008 to 2012 were used, because they were common years for the four farms. The information of interest was farm identification, sow identification, date at first mating, date of first farrowing, number of pigs born alive, number of pigs born alive per sow productive lifetime, number of piglets weaned, pigs weaned per sow productive lifetime and reason of culling. Piglets born alive per sow per year (PB/S/Y) and piglets weaned per sow per year (PW/S/Y) were calculated as follow: if sow productive lifetime was less than 366 days then PB/S/Y or PW/S/Y was equal to the total pigs born alive or weaned per sow during their productive lifetime; if sow productive lifetime was greater or equal than 365 days then PB/S/Y or PW/S/Y was equal to the total pigs born alive or weaned per sow during their productive lifetime times 365 divided by the productive lifetime of the sows. After calculating PB/S/Y and PW/S/Y, two groups of sows were formed, one with sows producing less than 30 pigs born alive or weaned per year (0) and the other with sows producing 30 or more pigs born alive or weaned per year (1), named PB30 and PW30 respectively.

Data from 7471 and 7181 sows were analyzed using descriptive statistics and binary logistic regression. The explanatory variables were farm (1, 2, 3 and 4), year of first farrowing (2008-2012), season of farrowing (dry: February to May; rainy: June to September; windy: October to December and January), reason of culling, and the continuous variables: number of pigs born alive at first farrowing, productive lifetime, in months, and age at first farrowing, in months. Reasons of culling were categorized as: reproductive associated problems (anestrous, prolapse, metritis, etc.), locomotion associated problems (lameness, downer syndrome, foot lesions), small litter size of sow, disease, advanced age, and other reasons (death, unidentified).

The binary logistic regression model which described the response variables was:

Logit [P(Y=1)]= ln[P(Y=1)/(1-P(Y=1))= β₀ + β₁ X₁ + β₂ X2+ β₃ X₃ + β₄ X₄ + β₅ X₅ + β₆ X₆ + β₇ X₇.

Where β₀ = constant; β₁, β₂, β₃, β4_, β_5, β₆ and β₇ are the regression coefficients; X₁, X₂, X₃, X₄, X₅, X₆, X₇ are the corresponding explanatory variables for farm, year of first farrowing, season of first farrowing, reasons of culling, number of pigs born alive, productive lifetime and age at first farrowing. The first four variables were included as categorical and the last three as continuous variables. Statistical analyses were carried out using the R program (2013).

Results

The overall frequencies of sows with 30 or more PB/S/Y and PW/S/Y were 16.7% (1244/7471) and 11.4% (820/7181), respectively. The frequencies of sows with 30 or more PB/S/Y in farms 1 to 4 were 19.4, 19.6, 6.65 and 4.30%, respectively. The frequencies of sows with 30 or more PW/S/Y in farms 1 to 4 were 14.4, 7.29, 4.24 and 1.24%, respectively.

The results of the binary logistic regression for the factors associated with PB/S/Y and PW/S/Y are shown in Tables 1 and 2. The factors: farm, year of first farrowing, reason of culling, number of pigs born alive at first farrowing, productive lifetime and age at first farrowing, were all associated with the production of 30 or more PB/S/Y, except season of first farrowing. For the production of 30 or more PW/S/Y, season, the number of pigs born alive at first farrowing and age at first farrowing were not significant (P > 0.05).

The odds of a sow with 30 or more PB/S/Y were higher for farms 1, 2 and lower for farm 3 as compared to farm 4 (Table 1). The odds of a sow with 30 or more PW/S/Y were higher for farms 1, 2 and 3 as compared to farm 4. The odds of sows with 30 or more PB/S/Y and PW/S/Y in farm 1 were 1.84 and 12.4 times greater than for sows in farm 4.

Also, the odds of 30 or more PB/S/Y increased and the odds of 30 or more PW/S/Y tended to increase with year of first farrowing of the sows (Tables 1 and 2). The sows culled by disease and locomotion reasons were more likely to produce 30 or more PB/S/Y; whereas, small litter size at first farrowing and disease had higher odds of 30 or more PW/S/Y. The odds of 30 or more PB/S/Y increased for large litters at first parity and for sows remaining longer in the farm, and decreased as the age of sow at first farrowing increased (Table 1). With respect to PW/S/Y the odds increased for large litters at first farrowing (Table 2).

Discussion

The percentage of sows with 30 or more pigs born alive (16.7%) and 30 or more piglets weaned (11.4%) per year here found for the four farms cannot be compared to other studies because to our knowledge this is the first study of this type. However, Gill (2007) mention that the production of 30 PW/S/Y is within the reach of many farms in Europe, Canada and the USA. This sentence suggests differences between farms as was found in this study. Because reproductive and nutritional managements were similar between farms, differences between them could be attributed to herd sizes, management decisions, population structures and length productive lifetime of sows. Also farm 3 was a continuous farm system. Farm differences have been reported for other related traits such as productive lifetime (Stalder et al 2004; Engblom et al 2008; Segura-Correa et al 2011a) and lifetime pigs produced per sow (Sasaki and Koketsu 2008; Koonawootrittriron et al 2012). Serenius and Stalder (2007) reported that longevity is impacted by farm management, leg conformation, sow’s own prolificacy, and sow’s origin parity and genetics.

The increase in the frequency of sows producing 30 or more PW/S/Y with time, may suggest a gained experience by farm workers, management improvements and better genetic material used in the farms. This indicates that the farms are doing well with time and that productivity could improve in the future.

Reason of culling was another important factor influencing the frequency of sows with 30 or more pigs per sow per year. Reproductive problem was the main reason (after unknown reason), why sows did not reach 30 or more PB/S/Y and PW/S/Y. This could be explained because reproductive problems was the main cause of culling in three of the four farms here studied (Segura-Correa et al 2011b), which in turn affects productive lifetime. For the data of this study the shortest productive lifetime means corresponded to problems related with locomotion and reproductive reason of culling (means 475 and 510 days respectively). Therefore, attention should be given to sows with reproductive problems such as anestrous, metritis, prolapses, etc.

The sows that stay longer in the farm were more likely to produce 30 or more pigs (Tables 1 and 2). The reason for this could be culling, only the most productive and healthy sows remain in the herd. However, to keep too old sows may not be prudent because too advance age (or high order parity) is associated to small litter sizes and a high incidence of reproductive problems (Lawlor and Lynch 2007). Smaller litter size has been reported, in the same farms here studied, for sows with 8 or more parities as compared to sows with 3 to 7 parities and even smaller litter size than for first parity sows (Ek-Mex et al 2016).

Sows being mated earlier or having their first farrowing at an early age were more likely to have 30 or more PB/S/Y. There is not report about risk factors affecting this traits; however, early age at first mating or first farrowing have a favorable effect on lifetime productivity of sows. Saito et al (2011); Segura-Correa et al. (2011a); Koonawootrittriron et al 2012) found significant association of gilts mated at younger age with better lifetime productivity and longer longevity. Early mating of gilts is also expected to increase PB/S/Y; however, attention should be given to their feeding and body weight at first farrowing in order to maintain their body condition.

Sows with larger litters at first farrowing were more likely to have 30 or more PB/S/Y. This is congruent with the fact that sows with large litters at first farrowing stay longer in the herd and produce more pigs during their productive lifetime (Segura-Correa et al 2011a). However, care should be taken with sows with large litter sizes at first farrowing because they suffer a drop in litter size in their second parity, as have been found in the farms here studied (Gomez-Medina et al 1999; Segura-Correa et al 2013). Litter size at first farrowing and age at first farrowing did not influence the number of PW/S/Y probably because cross fostering was a common practice in the farms here studied.

Conclusions

• Differences between the farms here studied for sows with > 30 PB/S/Y and > 30 PW/S/Y indicates differences in management practices other than feeding and reproductive management. Reducing the reasons of culling by reproductive problems, and increasing the care of early first parity sows with large liter sizes may increase productivity in the farms.

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Received 13 August 2016; Accepted 3 November 2016; Published 1 December 2016

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