Effect of live weight development and reproduction in first parity on reproductive performance of second parity sows - Part 3
L.L. Hovinga,b,∗, N.M. Soedea, E.A.M. Graatc, H. Feitsmad, B. Kempa
a Adaptation Physiology Group, Wageningen Institute of Animal Sciences (WIAS), Wageningen University, The Netherlands
b 荷兰Varkens KI Nederland公司
b Varkens KI Nederland, The Netherlands
c Quantitative Veterinary Epidemiology Group, WIAS, Wageningen University, The Netherlands
d Institute for Pig Genetics (IPG), The Netherlands
窝产仔数 Litter size
受胎率 Pregnancy rate
繁殖性能 Reproductive performance
二胎母猪 Second parity
The aim of this study was to quantify the association between reproductive performance of second parity sows, focusing on non-pregnancy and litter size in relation to measures of sow live weight development in first parity.
二胎母猪的繁殖性能与泌乳期体重损失(Morrow et al., 1989; Thaker and Bilkei, 2005)和第二胎断奶到配种间隔(WII2, Vesseur, 1997) 等变量有关。有文献记录，泌乳期的高体重损失会降低随后胎次的窝产仔数和受胎率(Thaker and Bilkei, 2005)，并延长二胎断奶到配种间隔WII2 (Vesseur, 1997)。
Reproductive performance of second parity sows is related with several variables such as lactation weight loss (Morrow et al., 1989; Thaker and Bilkei, 2005) and weaning to insemination interval in second parity (WII2, Vesseur, 1997). A high lactation weight loss has been reported to decrease litter size and pregnancy rate in subsequent parity (Thaker and Bilkei, 2005) and to increase WII2 (Vesseur, 1997).
在我们的研究中，二胎妊娠失败和窝产仔数与许多和体重增加相关的变量有关。然而，这些变量中的很多都是高度相关的，无法在多变量模型中分析。但当研究的目的是预测时，这并不是一个问题(Hosmer and Lemeshow, 1989)。由于我们的目的不是预测，而是解读由因果因素引起的差异，我们也将讨论单个预测因素的结果。从这些数据中无法判断哪个解释变量在解读差异时最重要。
In our study many variables concerning live weight development were associated with non-pregnancy and litter size in second parity. However, many of these variables are highly correlated and cannot be analyzed in a multivariable model. This is not a problem when prediction is the goal of the study (Hosmer and Lemeshow, 1989). As our goal is not to predict, but to explain differences caused by causal factors, we will also discuss the results of single predictors. From these data it cannot be judged which explanatory variable is most important in explaining differences.
在我们的研究中，初配到第一次断奶的体重增加情况影响了两个猪场的二胎受胎率和A场的二胎产仔数，因此这似乎是影响二胎繁殖性能的一个重要变量。然而，我们应该注意到，对于TNB2的分析，最终模型的R2相当低，这表明还应该有其他因素(尽管在研究中没有测定)影响第二胎的产仔数。从初配到第一次断奶期间的增重代表了母猪在第一个繁殖周期的生长发育，它是妊娠期间增重(r = 0.55)和哺乳期间减重(r = 0.50)的综合效应。用妊娠期间增重和哺乳期间减重这两个变量替换初配到第一次断奶期间的增重，对这两个变量的影响都不显著(结果未显示)。因此，初配到第一次断奶期间的体重增加似乎比单独的每个变量能更好地解释TNB2。
In our study, weight gain from first insemination to first weaning affected pregnancy rate in second parity on both farms and litter size in second parity on farm A and therefore seems to be an important variable affecting reproductive performance in second parity. One should note, however, that for the analysis on TNB2 the R2 for the final models was rather low, indicating that there should be also other factors, though not measured in the study, affecting litter size in second parity. Weight gain from first insemination to first weaning represents the growth of an animal during the first cycle and is a combined effect of weight gain during pregnancy (r = 0.55) and weight loss during lactation (r = 0.50). Replacing weight gain from first insemination to first weaning with the two variables weight gain during pregnancy and weight loss during lactation resulted in non-significant effects for both variables (results not shown). Weight gain from first insemination to first weaning, therefore, appears to be a better explanation for TNB2 than each variable separately.
初配到第一次断奶期间体重增加对繁殖结果的积极影响可能是由于年轻的母猪希望生长到体成熟的意愿。在育种上对瘦肉型猪的选育导致了后备母猪在初配时生理上并不成熟(Everts, 1994)。因此，后备母猪和年轻母猪仍然需要生长发育，以达到其成年体重和体成熟，或许这种成长的意愿是为了达到某个生理上的目标(Clowes et al., 1994; Everts and Dekker, 1995)。如果在初配到第一次断奶期间没有实现这种生长，那么母猪可能会在断奶后优先满足自身生长发育而不是繁殖，这可能会导致第二胎与第一胎相比妊娠失败率更高，窝产仔数更少。我们的数据显示，当初配到第一次断奶期间体重增加时，受胎率也会增加。这证实了一种假设，即生理上相对未成熟的母猪可能是导致二胎母猪繁殖性能差的一个因素。
Positive effects of weight gain between first insemination and first weaning on reproduction results might be explained by the desire of young animals to grow to a certain mature size. Selection on lean growth has led to a gilt which is physiologically immature at time of first insemination (Everts, 1994). Therefore, gilts and young sows still need to grow to reach their mature weight and body composition, perhaps by aiming to reach a certain intrinsic target (Clowes et al., 1994; Everts and Dekker, 1995). If this growth is not achieved between first insemination and first weaning a gilt might prioritize growth above reproduction after weaning, which can result in non-pregnancy or reduced litter sizes in second parity compared with first parity. Our data show that the percentage pregnancy increases when weight gain between first insemination and first weaning increases. This substantiates the hypothesis that intrinsic growth of a, relative, immature gilt to mature size, can be a factor involved in poor reproductive performance in second parity sows.
断奶至配种间隔对两个场二胎母猪的繁殖性能也都有影响；间隔≥21天的母猪与间隔6-20天的母猪相比，二胎产仔数更高。Vesseur(1997)和Morrow等人(1989)也报道了类似的结果。通过延长断奶到配种之间的间隔，母猪有更多的时间从哺乳期的体重损失中恢复过来，从而表现出更好的繁殖性能(Morrow et al.， 1989)。
Weaning to insemination interval also affected reproductive performance of second parity sows on both farms; sows with an interval≥21 days showed higher litter sizes in second parity compared with sows with an interval of 6–20 days. Similar results have been reported by Vesseur (1997) and Morrow et al. (1989). By extending the period between weaning and insemination sows have time to recover from lactation weight loss and will therefore show better reproductive performance (Morrow et al., 1989).
A场的第一胎母猪产仔数较低可能与两个猪场的母猪在初配时的日龄(可能还有体重)差异有关。Le Cozler et al.(1998)和Schukken et al.(1994)都表明首次配种或受孕时日龄大于270天的母猪在第一胎的活产仔数会更高。两个猪场第一胎产仔数和第二胎产仔数之间的关系或许可以用第一胎产仔数和第二胎产仔数之间的高度遗传相关性来解释(Hanenberg et al., 2001)。然而，正如Hanenberg等人(2001)所描述的那样，表现型相关性很低(A猪场的r = 0.05, B猪场的r = 0.22)。A场母猪体重变化情况对二胎繁殖性能的影响相对更大，也可能是因为B场后备母猪在初配时日龄更大，体重更高。一胎母猪对身体储备的消耗特别敏感，因为它们在第一次分娩时没有足够的身体储备，它们的采食量不足以满足哺乳期间的能量需求(Mejia-Guadarrama et al., 2002)。 初配日龄更大、体重更高的后备母猪，在第一次分娩时体重很可能也会更高(A场r = 0.43，B场r = 0.53，表1)。因此能够更好地应对哺乳期间的能量负平衡(Gill, 2000)。结果显示，两个猪场母猪体重的变化情况与一胎繁殖性能和二胎繁殖性能之间的关系存在差异。说明初配的日龄、体重等管理因素，以及可能还有许多其他因素会影响这些关系。因此，当评估体重变化情况、第一胎繁殖性能和第二胎繁殖结果之间的一般性关系时，一定要考虑猪场的管理策略。
The lower production of first parity sows on farm A compared to farm B might be related to the difference in age (and possibly weight) at first insemination between both farms. Le Cozler et al. (1998) and Schukken et al. (1994) both showed that sows older than 270 days at first mating or conception produced more piglets born alive in first parity. The relation between litter size in first parity and litter size in second parity on both farms might be explained by a high genetic correlation between litter size in first and litter size in second parity (Hanenberg et al., 2001). Phenotypic correlation, however, was low (r = 0.05 for farm A and 0.22 for farm B) as is also described by Hanenberg et al. (2001). The strong effect of sow development on reproduction performance of second parity sows on farm A could also be related to the fact that gilts on farm B were heavier and older at first insemination compared with gilts on farm A. First parity sows are especially sensitive to body reserve depletion during first lactation. They do not have enough body reserves at first farrowing and their feed intake capacity is not sufficient to fulfill energy needs during lactation (Mejia-Guadarrama et al., 2002). A heavier and older gilt at first insemination is probably also heavier at first farrowing (r = 0.43 for farm A and r = 0.53 for farm B, Table 1), and therefore better able to cope with the negative energy balance during lactation (Gill, 2000). The results show that relations between live weight development and reproduction in first parity and subsequent reproduction in second parity differ between the two farms. It indicates that management factors like age and weight at first insemination and probably many other factors affect these relations. Farm management strategies should therefore always be taken into account when trying to assess generalized associations between live weight development, reproduction in first parity and subsequent second parity reproduction results.
返情复配猪不纳入研究对于分析窝产仔数以确定胎次间窝产仔数的真正差异是非常重要的，因为与正常发情配种的猪相比，返情复配的猪其窝产仔数通常更高些(Tummaruk et al., 2001)。例如，A场包括返情复配的猪在内的二胎母猪产仔数要比不包括返情复配的猪的产仔数高0.2头(11.8 vs.11.6)，B场要高0.3头(11.9 vs.11.6)。然而，猪场的管理软件并不会单独显示第一次配种受孕的产仔数，所以第一个发情周期对第二胎繁殖性能的真正影响被掩盖了。因此，若能在管理软件中加入第一个发情周期配种受孕的窝产仔数，就可能会为养殖户和养猪咨询师提供有价值的信息。
Exclusion of repeat breeders for analysis on litter size is important to determine the true difference of litter sizes between parities, since repeat breeders often have larger litter sizes compared with non-repeat breeders (Tummaruk et al., 2001). For example, litter sizes for second parity sows including repeat breeders would have been 0.2 piglet higher for farm A (11.8 vs. 11.6) and 0.3 piglet higher for farm B (11.9 vs. 11.6) compared with litter sizes of second parity sows not including repeat breeders. Sow management programs, however, do not separately show litter sizes from first insemination, and therefore the true effects of first cycle on reproductive performance in second parity is masked. Adding litter size after first insemination to sow management programs might thus provide valuable information for farmers and their advisors.
The results described in this study, show that gilts that are relatively light or young at first insemination have reduced reproductive performance in first parity. For these sows, sow live weight development has a large influence on reproductive performance in second parity. Management of these animals should aim to optimize development at first insemination and to increase growth between first insemination and first weaning, for example by increasing growth during pregnancy or reducing weight loss during first lactation, in order to optimize production in second parity.
The authors thank Dr. Bas Engel for his assistance with statistical analyses. We would also like to thank research centers Sterksel and Rosmalen for providing the data.