Effects of betaine and heat stress on lactation and postweaning reproductive performance of sows

Review: What have we learned about the effects of heat stress on the pig industry?

Pig production faces seasonal fluctuations. The low farrowing rate of sows mated in summer, increased carcass fatness of progeny born to the sows mated in summer, and slower growth rate of finisher pigs in summer are three economically important impacts identified in the pig industry. The purpose of this review is to examine advances over the past decade in understanding the mechanisms underlying the three impacts associated with summer conditions, particularly heat stress (HS), and to provide possible amelioration strategies. For impact 1, summer mating results in low farrowing rates mainly caused by the high frequency of early pregnancy disruptions. The contributions of semen DNA damage, poor oocyte quality, local progesterone concentrations, and suboptimal embryonic oestrogen secretion are discussed, as these all may contribute to HS-mediated effects around conception. Despite this, it is still unclear what the underlying mechanisms might be and thus, there is currently a lack of commercially viable solutions. For impact 2, there have been recent advances in the understanding of gestational HS on both the sow and foetus, with gestational HS implicated in decreased foetal muscle fibre number, a greater proportion of lighter piglets, and increased carcass fatness at slaughter. So far, no effective strategies have been developed to mitigate the impacts associated with gestational HS on foetuses. For impact 3, the slowed growth rate of pigs during summer is one reason for the reduced carcass weights in summer. Studies have shown that the reduction in growth rates may be due to more than reductions in feed intake alone, and the impaired intestinal barrier function and inflammatory response may also play a role. In addition, it is consistently reported that HS attenuates fat mobilisation which can potentially exacerbate carcass fatness when carcass weight is increased. Novel feed additives have exhibited the potential to reduce the impacts of HS on intestinal barrier function in grower pigs. Collectively, based on these three impacts, the economic loss associated with HS can be estimated. A review of these impacts is warranted to better align the future research directions with the needs of the pig industry. Ultimately, a better understanding of the underlying mechanisms and continuous investments in developing commercially viable strategies to combat HS will benefit the pig industry.

Sow performance in response to natural betaine fed during lactation and post-weaning during summer and non-summer months

Background

Two studies were conducted to evaluate the effects of dietary natural betaine on sow reproductive performance during summer (Exp. 1) and non-summer months (Exp. 2). Treatments were designed as a 2 × 2 factorial arrangement with factors including dietary betaine (0 or 0.2%) and period of supplementation (lactation or post-weaning until 35 days post-insemination). In Exp. 1, 322 and 327 sows and in Exp. 2, 300 and 327 sows representing young (parity 1 and 2) and mature (parity 3 to 6) sows, respectively, were used.

Results

In Exp. 1, supplementation of betaine during lactation increased sow body weight losses (− 11.95 vs. −14.63 kg; P = 0.024), reduced feed intake (4.12 vs. 4.28 kg/d; P = 0.052), and tended to reduce percentage of no-value pigs (P = 0.071). Betaine fed post-weaning reduced weaning-to-estrus interval (5.75 vs. 6.68 days; P = 0.054) and farrowing rate (86.74% vs. 91.36%; P = 0.060), regardless of parity group. Post-hoc analysis with sows clustered into 3 parity groups (1, 2 and 3, and 4+) indicated that betaine fed in lactation to parity 4+ sows (P = 0.026) and betaine fed post-weaning to parity 1 sows increased the number of pigs born in the subsequent cycle (P ≤ 0.05). In Exp. 2, betaine fed during lactation tended to reduce the weaning-to-estrus interval (6.64 vs. 7.50 days; P = 0.077) and farrowing rate (88.23% vs. 83.54%; P = 0.089), regardless of parity group. Feeding betaine post-weaning reduced number of pigs born (13.00 vs. 13.64; P = 0.04) and pigs born alive (12.30 vs. 12.82; P = 0.075), regardless of parity group.

Conclusions

Using 0.2% betaine during the non-summer months did not benefit sow performance. During the summer, betaine supplementation in lactation increased subsequent litter size in parity 4+ sows. Betaine fed during the post-weaning period reduced the wean-to-estrus interval and farrowing rate, increased total number of pigs born for parity 1 sows and reduced total number of pigs born to parity 4+ sows. Further research is needed to determine if the detrimental effects on feed intake and farrowing rate may be correlated and depend on dietary betaine level.

Dietary betaine reduces incidence of follicular cyst in post-partum Karan Fries cows during hot-humid season

The objective of this study was to investigate the heat stress ameliorating effect of dietary betaine in reducing the risk of development of follicular cyst in dairy cows during hot-humid season. Eighteen pre-parturient Karan Fries (KF) cows in their 2nd to 5th parity were selected and assigned to 2 groups of 9 cows each on basis of parity and body weight. One group of cows was kept as control and other as treatment (50 g betaine/day/cow). Environmental variables and temperature humidity index (THI) of sheds were recorded during the experimental period. Body weight, dry matter intake (DMI), plasma non esterified fatty acids (NEFA) and cortisol levels were measured in both groups at fortnightly interval. Trans-rectal B-mode real time ultrasonography was performed weekly for diagnosis of follicular cyst. Results showed nonsignificant increase in mean DMI (1.86±0.12 kg vs 1.79±0.12 kg per 100 kg body weight) and overall body weight (416.76±10.24 kg vs 411.33±11.07 kg) in treatment group compared to control group. Plasma NEFA concentrations were lower in treatment group as compared to control (329.42±29.08 μmol/L vs 407.05±15.68 μmol/L). Plasma cortisol concentrations were significantly lower in treatment group as compared to control group (4.91±0.68 ng/ml vs 6.89±0.49 ng/ml). In control group, 22.22% cows had follicular cyst on their ovaries whereas no follicular cyst was found in betaine supplemented cows. It can be concluded that supplementation of 50 g betaine/cow/day reduces the incidence of follicular cyst along with reduction in plasma NEFA and cortisol levels.

A novel blood-sampling technique in lactating sows: The mammary vein route

In the pig industry, labour efficiency and animal welfare have become two of the most important factors for achieving technical goals and farming competitiveness. Blood sampling is one of the most common sample-collecting techniques, but routine on-field blood collection can be very demanding for farm operators and the welfare of the animals, in particular for lactating sows. The aim of this study was to describe and investigate the mammary vein as a novel means of blood access in lactating sows that does not require coercive restraint. The study involved a total of 68 sows: 34 animals were sampled from the jugular vein (Group J) and the other 34 sows from the mammary vein (Group M). Labour time and indicators of the sow welfare (vocalizations during collection and serum cortisol concentration in the 30min after the procedure) were collected from the two groups. The total amount of labour required, calculated as the time employed to perform blood collection multiplied by the number of operators involved in performing the technique (one for Group M and two for Group J, one for restraint and one for sampling), was significantly lower in Group M than Group J (Group M, 39.83±29.45s; Group J, 82.73±55.34s; P<0.001). Mean blood volume collected at T₀ was 4.81±2.00mL and 4.84±1.73mL in Group J and Group M, respectively (P>0.05). The percentage of sows that vocalized in Group M was less than in Group J (2.94% vs. 94.12%; P<0.001). Serum cortisol concentrations were not statistically different between the two groups (P>0.05). The present study suggests greater efficiency in terms of saving labour time and reducing sow vocalization during blood collection with the use of mammary vein access compared with jugular vein access.

Invited review: Management strategies capable of improving the reproductive performance of heat-stressed dairy cattle

Impaired fertility during periods of heat stress is the culmination of numerous physiological responses to heat stress, ranging from reduced estrus expression and altered follicular function to early embryonic death. Furthermore, heat-stressed dairy cattle exhibit a unique metabolic status that likely contributes to the observed reduction in fertility. An understanding of this unique physiological response can be used as a basis for improving cow management strategies, thereby reducing the negative effects of heat stress on reproduction. Potential opportunities for improving the management of dairy cattle during heat stress vary greatly and include feed additives, targeted cooling, genetic selection, embryo transfer and, potentially, crossbreeding. Previous studies indicate that dietary interventions such as melatonin and chromium supplementation could alleviate some of the detrimental effects of heat stress on fertility, and that factors involved in the methionine cycle would likely do the same. These supplements, particularly chromium, may improve reproductive performance during heat stress by alleviating insulin-mediated damage to the follicle and its enclosed cumulus-oocyte complex. Beyond feed additives, some of the simplest, yet most effective strategies involve altering the timing of feeding and cooling to take advantage of comparatively low nighttime temperatures. Likewise, expansion of cooling systems to include breeding-age heifers and dry cows has significant benefits for dams and their offspring. More complicated but promising strategies involve the calculation of breeding values for thermotolerance, the identification of genomic markers for heat tolerance, and the development of bedding-based conductive cooling systems. Unfortunately, no single approach can completely rescue the fertility of lactating dairy cows during heat stress. That said, region-appropriate combinations of strategies can improve reproductive measures to reasonable levels.

Effect of maternal or post-weaning methyl donor supplementation on growth performance, carcass traits, and meat quality of pig offspring

BACKGROUND

Limited studies have examined links between maternal methyl donor (MET) supplementation and the growth-development characteristics of offspring, and possible underlying mechanisms for such links. This study investigated the effect of maternal or post-weaning MET-supplementation on growth performance, carcass characteristics, and meat quality of the finishing (d 180) offspring. Twenty-four sows were placed on a control (C) or MET-supplemented diet during pregnancy and lactation. Forty-eight female offspring were fed the control or MET-supplemented diet from weaning to 6 months of age, resulting in four study groups (six litters per group): C/C, C/MET, MET/C, and MET/MET.

RESULTS

Maternal MET-supplementation increased average daily gain (ADG), body weight (BW), lean percentage and longissimus dorsi (LD) of the offspring at day 180 (P < 0.05), and upregulated the myosin heavy chain IIx, myogenic differentiation and muscle regulatory factor 4 mRNA levels in the LD muscle (P < 0.05). Meanwhile, offspring from maternal MET-supplementation exhibited a higher pH_24h post mortem and superoxide dismutase activity, a lower L^* _45min , glycolytic potential, malonaldehyde content in the LD muscle, and plasma homocysteine concentration (P < 0.05).

CONCLUSION

Maternal MET-supplementation has a remarkable effect on growth performance, carcass traits, and meat quality of the offspring, which is associated with increased expression levels of myogenic genes and anti-oxidant capacity. © 2018 Society of Chemical Industry.

Effects of L-citrulline supplementation on heat stress physiology, lactation performance and subsequent reproductive performance of sows in summer

Lactating sows are susceptible to heat stress (HS). Part of the thermoregulatory response to HS is to increase peripheral blood flow, which is mediated in part by the vasodilator, nitric oxide (NO). Therefore, the aim of this experiment was to determine the effect of supplementation of L-citrulline, a NO precursor, on symptoms of HS, lactation performance and subsequent reproductive performance of sows in summer. A total of 221 summer farrowing mixed parity sows were fed either a control diet or supplemented with 1% L-citrulline upon entry to the farrowing house (6 ± 1.8 days for mean ± standard deviation [SD] before farrowing) until weaning (26 ± 1.5 days). The average daily minimum and maximum temperature in the farrowing house was 21.0 ± 1.88 and 29.2 ± 3.82°C (mean ± SD). Rectal temperature, respiration rate, and plasma and urinary nitrite and nitrate (NOx) of sows were measured on the 19th day post-farrowing. Supplemental L-citrulline in the diet did not affect the number of piglets born alive, feed intake of sows, body weight or backfat thickness of sows at weaning, or litter weight gain. L-citrulline tended to reduce piglet pre-weaning mortality rate from 18.6% to 15.6% (p = 0.058). L-citrulline reduced the respiration rate of sows compared to the control diet at 17:00 hr (Time × Diet, p < 0.001); however, rectal temperature was not affected. L-citrulline tended to increase urinary NOx concentrations (127 vs. 224 µM, p = 0.057) but not plasma NOx concentrations. L-citrulline did not affect farrowing rate or number of piglets born alive in the subsequent parity. In conclusion, L-citrulline supplementation reduced respiration rate of lactating sows and reduced piglet pre-weaning mortality rate in summer. Whether the effects were due to a NO-dependent mechanism requires further validation.